Article

Sedimentology and trace element geochemistry of shallow-marine carbonates: An approach to paleoenvironmental analysis along the Pagny-sur-Meuse Section (Upper Jurassic, France)

March 2006
Facies 52(1):69-84

DOI:10.1007/s10347-005-0026-0

Authors:

Benoit Vincent

Cambridge Carbonates Ltd

Claire Rambeau

University of Strasbourg

Laurent Emmanuel

Sorbonne University

The Middle Oxfordian formations of the eastern edge of the Paris Basin (France) contain mostly shallow-marine carbonate sediments. A detailed sedimentological study of the Pagny-sur-Meuse section reveals five major environments that make up a depositional profile succession grading from tidal-flat to distal lagoon/oolithic shoal. Stratigraphic cycles were established and illustrate variations of the A/S ratio (accommodation rate/sedimentation rate) and hence variations of accommodation space. Geochemical analyses (Sr, Mg, Fe, and Mn) have been conducted along a part of the section. Statistic analysis of the geochemical data (box diagrams and principal component analysis, PCA) are used to investigate similarities between the variations of trace element contents and depositional environments. An analysis of variance (ANOVA) is used to test whether the amounts of trace elements are related to the depositional environments. The relationship is highly significant for Sr, Fe, and Mn. A number of a posteriori tests are performed with this ANOVA to compare the geochemical data for each environment. Tidal-flats and distal lagoon/oolithic shoal transition are the most significantly discriminated environments. Differences among the lagoonal environments are less obvious. Despite (1) an open diagenetic system that explains the low Sr values and (2) the possible influence of clays on Fe–Mn contents in the upper part of the section, some of the variations in Sr and Fe–Mn seem to reflect changes in depositional environment. A number of hypotheses are proposed about the relations between trace elements and paleoenvironmental parameter records: Sr contents may illustrate variations of paleosalinity in depositional environments, whereas Fe and Mn contents seem to record variations of specific low detrital inputs coming from isolated islands submitted to pedogenesis. Low Sr content coupled with relatively high Fe and Mn contents is indicative of low salinity environment near subaerially exposed islands, located in the proximal part of a reconstructed theoretical depositional profile. Conversely, high Sr content coupled with relatively low Fe and Mn contents reflect a more open marine environment in the distal part of the same profile. Such analysis based on trace element geochemistry does not constitute a model but it shows that Sr, Fe, and Mn can partially record indications about paleoenvironmental conditions in shallow-marine carbonates.

Statistical evaluation of elemental concentrations in shallow-marine deposits (Cretaceous, Lusitanian Basin)

Article

Jul 2017
MAR PETROL GEOL

The elemental geochemistry of ancient shallow-marine carbonates represents an often underexplored archive of paleoenvironmental change and diagenetic pathways. Complex multi-parameter datasets from a lithologically heterogeneous sedimentary succession in the southern part of the Lusitanian Basin (Ericeira, Portugal) are presented and interpreted. The section comprises marly, carbonate, and sandstone-rich coastal-marine deposits of early Albian to early Cenomanian age. Principal component analysis of bulk elemental abundance (Ca, Mg, Sr, Fe, and Mn) lead to define four geochemical clusters based on common elemental attributes. Siliciclastics and dolomitized limestones facies yield evidence for significant diagenetic alteration, but still preserve information on paleoshoreline position. Mixed carbonate-siliciclastics and limestone facies bear evidence for relative sea-level position and relevant paleoclimatic information in their elemental record. Accordingly, mid-Albian mixed carbonate-siliciclastic deposits present variable degrees of continental influx. Specifically, a sharp increase of Fe and Mn concentrations in relation to continental input is in agreement with periods of enhanced hydrological cycling and increased weathering on adjacent emerged lands. The progressive transition towards more marine conditions is accompanied by higher Ca and Sr content and represented by limestone facies corresponding to a higher sea-level position during late Albian to early Cenomanian times. Moreover, this facies records a trend towards warmer and more arid conditions. Early diagenetic stabilization and /or dissolution of aragonite into low-Mg calcite can account for major elemental variations, including higher Sr content strongly coupled with Ca content, along with lower Mg, Fe and Mn concentrations. Data shown here provide solid evidence that the statistical analysis of the elemental record of ancient marine deposits, when combined with conventional sedimentology and thin section petrography, allow for elaborate conclusions on their depositional environment and diagenetic pathways. Cored wells and facies-specific reservoir properties can be addressed by these methodologies, able to detect and quantify changes in patterns. Both industry and academy can therefore benefit from approaching such a complex interplay.

Geochemical Study of Late Cretaceous Sediments in Kuh-e- Dezdaran Section, in Central Zagros of Iran

Article

Full-text available

Aug 2012

Tarbur Formation is formed In Kuh-e- Dezdaran section that is situated in south of Chahar Mahal and Bakhtiyari Province with thickness of 115m and contains all of Calcareous and Dolomite sediments. The elemental analysis results and their plotted beside together shows that primary mineralogy of Tarbur Formation limestones contain in that section is aragonite and plotted amounts Mn about based on Sr/Ca indicated one close diagenetic environment with low water and rock ratio in this Formation . Geochemistry studies of Tarbur Formation Dolomites shows that, Mg,Fe and Mn values in dolomitic samples are more than calcic samples,whereas Ca,Na and Sr values in calcic samples are more than dolomitic samples that is related to Preferential Succession of Fe and Mn elements Instead of Mg in dolomite crystal network and Preferential Succession of Na and Sr elements Instead of Ca in aragonite crystal network.

New insights into geochemical behaviour in ancient marine carbonates (Upper Jurassic Ammonitico Rosso): Novel proxies for interpreting sea-level dynamics and palaeoceanography

Article

Jul 2014
SEDIMENTOLOGY

Elemental concentrations in Phanerozoic seawater are known to fluctuate both in time and space. With regard to carbonates precipitated from marine fluids, elemental concentrations in the carbonate crystal lattice are affected by a complex array of equilibrium and non-equilibrium as well as post-depositional alteration processes. In order to assess the potential of carbonate elemental chemostratigraphy, seven Upper Jurassic sections were investigated along a proximal to distal transect across the south-east Iberian palaeo-margin. The aim was to explore stratigraphic and spatial variations in Ca, Sr, Mg, Fe and Mn elemental abundances. The epicontinental geochemical record is influenced by the combination of continental runoff and a significant diagenetic overprint. In contrast, the epioceanic geochemical record agrees with reconstructed open marine sea water values, reflecting a moderate degree of syn-depositional to early marine pore water diagenesis. Establishing a fair degree of preservation of matrix micrite, a thorough statistical approach was applied and elemental associations tested for their environmental significance. Principal component and hierarchical cluster analyses revealed a persistent relation between carbonate Mg, Fe and Sr abundances. Processes related to early diagenetic nodulation in Ammonitico Rosso facies are most likely to account for the incorporation of these elements in the calcium carbonate lattice. The clear decoupling of carbonate manganese abundance with respect to the remaining elements is documented and related to high sea floor spreading rates and hydrothermal activity during the Late Jurassic. The investigation of potential time-fluctuation of geochemical patterns was approached through variogram computation. The observed temporal behaviour is most likely to be forced by relative sea-level dynamics, reflecting Late Jurassic palaeoceanographic conditions and potential planetary interactions. The data obtained in this study highlight the utility of elemental data from carbonate matrix micrites as geochemical proxies for studying the influence of remote trigger factors.This article is protected by copyright. All rights reserved.

The physical and geochemical character of the post‐depositional alterations in the Early‐Middle Jurassic carbonates on the western margin of the Indian Plate: Implications for cement morphologies and dolomitization

Article

Jul 2022

The physical and geochemical character of the post‐depositional changes present in the Early‐Middle Jurassic carbonate‐dominated units (Samana Suk, Shinawari, Chiltan and Loralai formations) of the Indus Basin, Pakistan have been addressed. The study is based on 11 sections along a N‐S transect on the western margin of the Indian Plate to provide an insight into the nature of cementation and dolomitization behavior by using an integrated petrographic and geochemical analysis. The carbonates located in the northern proximity are dominated by the eogenetic signatures of hardgrounds, biogenic micritization, and iron‐containing burrows. The pattern and yellowish‐brown coloration of the burrows is distinct, and shows a positive relationship with the Fe, Si, Al, K, Mn concentrations, and meteoric phase. The transition from the Early to Middle Jurassic is marked by a correspondent increase in the dolomitization and bioturbation but its intensity decreases from north to the south. The packing index and marine phreatic environments generally increase towards the south. The planar‐s to planar‐e protodolomite and dolomite proper have particularly targeted the micritic facies and allochems, courtesy of retaining high‐magnesian calcite waters, and the geochemical analysis also reveals some dedolomitization, associated with sequence boundaries. The pore occluding cements of the Samana Suk and Chiltan formations are Fe deficient and have low Sr and Mn levels, as compared to the Shinawari Formation. The latter has an elevated concentration of Fe, Mg, Si, Al, Sr, Mn, and the Fe + Mn versus Sr relationship and Mn* values suggest that cementation dominantly occurred in the oxic‐dysoxic zones of sub‐tropical climate.

Early Jurassic–Early Cretaceous Calcareous Nannofossil Biostratigraphy and Geochemistry, Northeastern Iraqi Kurdistan: Implications for Paleoclimate and Paleoecological Conditions

Article

Full-text available

Feb 2022

Early Jurassic- to Early Cretaceous-age calcareous nannofossils from the Sarki, Sehkanyian, Sargelu, Naokelekan, Barsarin and Chia Gara formations are investigated for the first time from the Warte area, northeastern Iraqi Kurdistan. A range of isotopic and inorganic geochemical analyses are carried out in order to reconstruct the paleoecological and paleoclimatic conditions during which the Sarki, Sehkanyian, Sargelu, Naokelekan, Barsarin and Chia Gara formations were deposited. The age of the Sargelu Formation was determined as Bajocian–Callovian based on the first occurrence of Cyclagelosphaera margerelii, Watznaueria britannica, W. fossacincta, W. manivitiae, Watznaueria barnesiae and Watznaueria ovata. Geochemical proxies (Sr, Ca, Al, Rb/Sr, Sr/Cu and Sr/Ba) for paleoclimate and paleoecological conditions, along with oxygen isotopes (δ18O) data, suggest that warm and arid climatic conditions were predominant during the Early Jurassic–Early Cretaceous period.

Effect of paleoclimate and paleoenvironment on organic matter accumulation in lacustrine shale: Constraints from lithofacies and element geochemistry in the northern Qaidam Basin, NW China

Article

Aug 2021
J PETROL SCI ENG

Organic matter enrichment in lacustrine shale is significantly influenced by the shale's paleoclimate and paleoenvironment as well as the changes within these settings. In this study, a total of 24 shales were vertically collected from the YQ-1 drilling well in the northern Qaidam Basin, north-western China. The high-resolution geochemistry analyses were performed to provide a detailed geological description of these samples through lithofacies interpretation, total organic carbon (TOC) content testing, element geochemistry analysis, mineralogical composition characterization, and comprehensive mechanism research. The results show that four lithofacies types can be identified in the Middle Jurassic Shimengou Formation, which consist of the brown oil shale with horizontal bedding, the black shale with well-developed lamination, the grey-black mudstone with horizontal and wavy bedding, and the carbonaceous mudstone with plant debris matter. The former two types are mainly deposited in the Upper Member within a deep and semi-deep lake environment, whereas the latter two types are deposited in the Lower Member within a littoral-shallow lake. The TOC content, paleo-salinity, redox action, and paleo-productivity of the Upper shales are higher than those of the Lower shales, and other parameters, such as the chemical weathering degree and terrestrial clastic input, are higher in the Lower Member shales. Based on the interpretation for lithofacies and geochemical data, the Lower shales are deposited in a small, shallow freshwater lake within an oxygen-rich and relatively wet and hot paleoclimate, whereas the Upper Member shales are deposited in a large, deep saltwater lake with dysoxic-anoxic conditions and a relatively arid and cold paleoclimate. The organic matter content in Lower Member is primarily determined through the amount of detritus input with a low paleo-productivity owing to a strong weathering, whereas that in the Upper Member is dominated by anoxic processes under a good preservation and a low deposition rate. The model reflecting the interrelation between accommodation and sediment-fill is employed to determine the mechanism of organic matter accumulation. Three depositional stages are distinguished within the Shimengou Formation corresponding to overfilled, underfilled, and balanced-filled sediments with average TOC contents of 0.84 %, 4.95 %, and 6.09 %, respectively. This study reveals the dominated factors controlling organic matter enrichment in a continental basin and proposes a TOC distribution mechanism, which could provide a guide for the shale gas and shale oil exploration.

Oxic-dysoxic Tidal Flat Carbonates from Sadara, Pachham Island, Kachchh

Chapter

Aug 2021

Sadara limestones in Goradonagar Formation of Pachham IslandPachham Island are dominantly intramicritic and contain bioclast, pellet, peloid, ooid; with nodular anhydrite. They exhibit intraformational chert breccia at the base, early diagenetic dolomite and predominant lime flake pebbles of intrabasinal origin in the middle, with development of algal laminated structures and desiccation cracks in the upper part; representing subtidal-intertidal-supratidal mudflat environment. Higher content of insoluble residue (av. 11.56%) and presence of illite, kaolinite, anhydrite, gypsum; indicate restricted circulation in coastal sabkha-like intertidal-supratidal zones. They exhibit higher CaO, low SiO2, Fe2O3, Al2O3, TiO2, K2O and P2O5. Trace elementTrace element composition of these sediments reveals higher Na, lower Mn, Ni, Cu, Co, Pb, U, Th, Sr contents, V/Cr and Ni/Co ratios. These signatures, together with seawater like REE pattern with low ∑REE + Y content, LREE depletion, positive La, Eu and negative Gd, Y, Ce anomalies, (Nd/Yb) SN and Y/Ho in these limestones; substantiates shallow marineShallow marine oxic-dysoxic nature with an insignificant terrigenous contribution. The δ13C (av. −1.06‰), δ18O (av. −5.06‰), Z values (av. > 120) support the shallow marineShallow marine nature of these limestones.

Mineralogy and geochemistry of the Late Triassic Baluti Formation, Northern Iraq

Article

May 2021
J AFR EARTH SCI

The petrography and geochemistry of clastic rocks collected from two sections from the Baluti Formation northern Iraq, have been investigated to infer the depositional environment of the Late Triassic Baluti Formation. Petrographic study of the carbonate unit shows that they consist mainly of heterogeneous poorly sorted grainstones and packstones, ooids, intraclasts, peloids, bioclasts and green algae (Halimeda). The abundant and heterogeneous size of these constituents suggests a subtidal lagoon/oolitic shoal depositional environment with an open marine water circulation. Trace element concentrations of the shales and marlstones reveal a wide difference in the depositional environment. The paleoclimate proxies (C-value, Sr/Cu, Rb/Sr, Ga/Rb, and Sr/Ba ratios) and presence of illite suggest a hot and arid to semiarid climates during the deposition of the Buluti sediments, which coincide with the Late Triassic global warming. The combined use of the Cd/Mo and Co*Mn proxies indicate the deposition mainly in open marine settings on the continental margin associated with upwelling and subordinate restricted marine settings. Trace element redox proxies (V/(V + Ni), Th/U, V/Cr, Ni/Co, and V/Ni ratios indicates anoxic to dysoxic to marginally oxic marine conditions. This difference in paleoredox conditions is likely to arise from the variation in the hydrographic conditions of the depositional basin including water depth, upwelling oxidation degree in the water column and salinity.

Testing carbonate chemostratigraphy across differentiated ancient shallow-platform environments (Early Kimmeridgian, S Iberia)

Article

Full-text available

Apr 2019

Shallow-platform settings with marked differences in paleoplatform bottom physiography influence the degree of connection with oceanic waters and overall circulation patterns, even when sharing the same palaeoclimatic conditions. Two Kimmeridgian shallow-marine settings have been explored to test the sensitivity and reliability of carbonate chemostratigraphy to detect such differences. An integrated overview of the obtained elemental trends depicted four major facies, shared along specific stratigraphic intervals of both depositional records. Diagenesis obliterated original geochemical signals only throughout the siliciclastics-rich interval, corresponding to the most landward setting. For the remaining facies, elemental features could be attributed to the differential action of forcing mechanisms operating along the south-Iberian paleomargin during Kimmeridgian times. The highest degree of continental influence can be recognized by a strong relationship between Fe and Mn for the most proximal setting, which fades out along the mixed carbonate-fine siliciclastic rhythmic deposition in more open settings. A characteristic geochemical signature of progressively more positive δ ¹³ C values and significantly higher Sr content is identified for the interval dominated by biogenic sponge buildups. Such a local response is related to local forcing by upwelling in the surroundings of a coral fringe. The geochemical signature of a hydrothermal origin can be clearly differentiated from the influence of mere terrigenous pulses. Accordingly, the decoupling of Fe and Mn along marginal settings is the clue to detecting major events of palaeogeographic restructuring. Observed temporal variations in Mg content along both studied sections are attributed to tectonic activity influencing nearshore/coastal water masses. By integrating chemostratigraphic information and complementary evidence, the palaeoenvironmental mechanisms promoting differentiated sedimentary records along ancient subtropical, shallow, coastal settings can be disentangled. © 2019 China University of Geosciences (Beijing) and Peking University

Temperature and cyclone frequency in Kimmeridgian Greenhouse period (late Jurassic)

Article

Aug 2018
GLOBAL PLANET CHANGE

The relationship between palaeoclimate warming and cyclone frequency is still poorly understood, even though tempestites (i.e. storm deposits) may be abundant in Greenhouse period deposits. The Kimmeridgian marl-limestone alternations of the North Aquitaine Platform include abundant tempestites that formed in shallow to moderate-depth marine environments affected by westward-moving cyclones. High-resolution sedimentological and sequence stratigraphic interpretations, combined with biostratigraphy have allowed us to date these deposits. However, changes in cyclone frequency and temperature have never been determined and compared for this interval. In the present work, the relationship between temperature, cyclone frequency and their controlling factors are addressed for the first time. Oxygen isotope analyses were performed on brachiopod and oyster shells and on bulk rock samples from three sections close to La Rochelle, western France. To define a western European temperature tendency for the entire Kimmeridgian, these δ¹⁸Oshell values were supplemented by new oxygen isotope measurements from Kimmeridgian brachiopod shells of the Burgundy and Jura Platforms. These new δ¹⁸Oshell values were compared with a selection of published contemporaneous δ¹⁸Oshell values in order to specify the Kimmeridgian Greenhouse climatic conditions. The resulting overview shows that the average temperature of shallow seawater did not change through the Kimmeridgian while deep seawater warmed close to the early-late Kimmeridgian boundary (i.e. during the Cymodoce zone of the Sub-boreal realm or time equivalent zone). This global seawater thermal homogenization coincides with the most important increase in cyclone frequency recorded through the Kimmeridgian of western France. At the western European scale, a small decrease in temperature took place during the early Kimmeridgian, which is interpreted as a switch in oceanic circulation, on the basis of new mineralogical and elemental analyses performed on the Kimmeridgian of the North Aquitaine Platform. This switch in oceanic circulation may be due to widespread Kimmeridgian extensional tectonic activity, and to proto-North Atlantic seaway opening in particular. This kind of tectonically-induced regional divergence from the late Jurassic Greenhouse climate conditions probably diminished or even disappeared at the early-late Kimmeridgian boundary, favouring the global thermal homogenization of marine waters and the increasing frequency of cyclones observed in the present work.

Cretaceous coastal lagoon facies: Geochemical insights into multi-stage diagenesis and palaeoclimatic signals

Article

Jan 2018

Shallow-water Cretaceous, carbonate platform archives have only rarely been explored through their elemental signature. Yet, facies-sensitive geochemical records can shed light onto the specific dynamics of shallow/proximal settings, where changes in depositional conditions are pronounced. Changes stemming from early and later diagenetic processes must be considered, since they may alter the original geochemical signals, but still contribute to a better understanding of the evolution of ancient shallow carbonates. Here, the elemental record of a variety of carbonate materials from two middle Cenomanian coastal lagoon settings is examined. The two selected sections (Lousa and Lampas, W Portugal) provide a varied record of lithofacies, including matrix micrite, corresponding to diverse palaeoenvironments (marine, marine lagoon, restricted lagoon and subaerial exposed intervals), along with dolomitized beds and atypical darkened grey carbonate horizons. Sparry carbonate veinlets that intersect these materials are included for comparison. Based on the characteristic elemental composition of each carbonate material, and by means of a stepwise statistical approach, dolomitization was determined to be a rather early feature occurring exclusively along shallow to frequently exposed intervals. In contrast, carbonate veinlets were identified as the latest diagenetic event. Matrix micrite and darkened beds present the lowest degree of geochemical differentiation, though certain key elemental contrasts allow for their comparison. Accordingly, the atypical case of darkened beds was attributed to an early blackening process in which low contents of organic matter and non-carbonate mineral phases played a decisive role. Matrix micrite samples—presenting a rather narrow range of elemental fluctuations—were linked to previously identified palaeoenvironmental settings by means of stratigraphically constrained cluster analysis. Specific combinations of elemental trends identified for each established cluster reflect variations in palaeoclimatic regimes throughout the studied interval. Furthermore, the degree of connectivity between open waters and coastal lagoons emerged as predictive of the distribution of major and trace elements in ancient shallow carbonates. This study explores the depositional and diagenetic controls forcing elemental distribution across dynamic shallow carbonate settings, as is the case of coastal lagoons. Complex and atypical elemental fingerprints, established by means of statistical analysis, provide arguments to reconstruct the evolution of the examined carbonate materials. Our findings are highly pertinent, as they: (i) provide a rich dataset not only regarding Lusitanian Basin deposits, but also for coeval settings where basin evolution and diagenesis are pivotal; (ii) underline the insight to be gained from time series analyses of raw elemental data collected from carbonate facies; and (iii) place a suite of numerical analyses within a logical hierarchy for stratigraphic facies analysis, fully supported by independent data.

Regression trees for modeling geochemical data—An application to Late Jurassic carbonates (Ammonitico Rosso)

Article

Dec 2014
COMPUT GEOSCI-UK

Fluid flow-driven multiphase dolomitization in the Cambrian Jutana Formation, salt range and adjacent area (Pakistan): insights from sedimentological and isotopic analyses

Article

Full-text available

May 2024

In this study, the aim was to investigate the circulation of Mg-rich fluids in the Cambrian Jutana Formation in the Salt Range and Khisor Range, Pakistan, through mineralogical, geochemical, and isotopic analyses. Previous research by (Khan and Shah, Geol Acta 17:1–18, 2019) identified three distinct dolomite types based on field observations and petrographic studies: Dol. I, as a fine-to-medium crystalline dolomite matrix, Dol. II as a medium-to-coarse crystalline dolomite cement, and Dol. III as fracture-filling dolomite cement. Mineralogical analyses conducted in this study revealed that Dol. I exhibited non-stoichiometric, low-ordered dolomite with a CaCO3 content ranging from 45.5 to 46.8% mol. In contrast, Dol. II and Dol. III were near stoichiometric, moderately ordered dolomites with CaCO3 contents of 48.0–49.3% mol and 49.0–49.7% mol, respectively. Geochemical compositions, including major and trace elements, showed high concentrations of Sr (184–436 ppm) and Na (4087–8710 ppm) in Dol. I, accompanied by relatively low values of Mn (466–1848 ppm) and Fe (1940–10510 ppm). Dol. II and Dol. III, on the other hand, exhibited high concentrations of Mn (1355–3157 ppm) and Fe (9030–32060 ppm) but lower contents of Na (1084–5566 ppm) and Sr (67–277 ppm). Oxygen isotope (δ¹⁸O) compositions indicated slightly negative values (−5.75 to −1.18‰ V-PDB) for Dol. I, extending to lower values (−6.64 to −2.05‰ V-PDB) for Dol. II, and even more negative values (−7.73 to −6.71‰ V-PDB) for Dol. III. Carbon isotope (δ¹³C) values (−2.02 to 0.10‰ V-PDB) for all three dolomite phases fell within the range of original marine compositions. Sr-isotope ratios were found to be higher (0.710154 to 0.713198) than contemporary marine compositions, indicating interactions between the dolomitizing fluids and radiogenic elements. Mg-isotope (δ²⁵Mg and δ²⁶Mg) results suggested that the fluids originated from an altered marine mixing zone (−0.70 to −0.61% 2σ) as well as from burial dolomitization (−1.66 to −1.19% 2σ). Based on the mineralogical studies, geochemical analysis, and isotopic compositions, it is proposed that the initial stage of dolomitization (Dol. I) occurred through near-surface mixing zone processes. Subsequently, Dol. II and Dol. III dolomitization took place under intermediate to deep burial conditions in later stages.

Depositional environment of the late Paleocene-early Eocene Sinjar Formation, Iraq: Implications from facies analysis, mineralogical and geochemical proxies

Article

Full-text available

Feb 2024

Reconstruction of the depositional environment of the Paleocene-Eocene Sinjar Formation from two outcrop sections in northwestern and northeastern Iraq has been evaluated using the traditional petrographic and facies analysis supported by X-ray diffraction and scanning electron microscopy with a focus on the Paleocene-Eocene (P-E) transition boundary. To this end, major and trace elemental geochemistry was conducted and various paleoenvironmental proxies for the paleoredox, paleoclimate, paleosalinity and paleoproductivity were determined in order to evaluate the changes in widely acknowledged environmental and climatic indicators and the elemental enrichment/depletion across the P-E boundary. The redox-sensitive trace element enrichment and the ir ratios (V/V + Ni, V/Cr, and U/Th) indicate that normal oxygenated circumstances prevailed during the late Paleocene deposition, and that anoxic conditions and a gradual commencement of oxygen depletion occurred during the early Eocene deposition. The coeval increase in the P 2 O 5 content, P/Ti, and P/Al ratios in the Eocene sediments suggests an increase in nutrients and primary productivity due to the effect of upwelling currents during early Eocene. The conditions can be verified by observing a small change in salinity levels from low to high across the P-E boundary, which can be indicated by the Sr/Ba ratios. In addition, certain minerals such as Mg-calcite, dolomite, and palygorskite are commonly present, and paleoclimatic changes can be observed across the P-E transition from arid to semiarid and then to humid conditions, which can be recorded from C-values, Sr-Cu, Rb/Sr ratios, and clay mineralogy. These conditions were noted in the Sinjar Formation, which is made up of many microfacies such as lime mudstone, wackstone, packstone, grainstone and boundstone. These microfacies were deposited in a shallow marine environment that extended from tidal flats to reef slopes, with a developed reef environment that included back reef, reef core, and fore reef environments.

Mineralogy and Geochemistry of the Paleocene-Eocene Palana Formation in Western Rajasthan, India: Insights for Sedimentary Paleoenvironmental Conations and Volcanic Activity

Preprint

Full-text available

Nov 2023

Organic-rich shale deposits of the Paleocene-Eocene Palana Formation in western Rajasthan, India were systematically analyzed based on the elemental composition and organic geochemistry combined with microscopic examinations to evaluate the sedimentary paleoenvironmental conations and volcanic activity and their impact on the high organic carbon accumulation. The Palana shales are categorized by high OM and sulfur contents with total values up to 36.23 wt. % and 2.24 wt. %, respectively, suggesting marine setting and anoxic environmental conditions during the Paleocene-Eocene period. The richness of phytoplankton algae (i.e., telalginite and lamalginite) together with redox-sensitive trace elements further suggests anoxic environmental conditions. The significant low oxygen conditions may contributes to enhance preservation of organic matter during deposition. The mineralogical and inorganic geochemical indicators demonstrate that the Palana organic-rich shale facies was accumulated in warm and humid climate and low salinity stratification conditions of the water columns, thereby contributing to high bioproductivity of the phytoplankton algae blooms within the photic zone. The presence of the high concentrations of Fe-rich silica minerals such as olivine in most of the Palana organic-rich shales facility volcanic origin and supports hydrothermal activities during the Paleocene-Eocene period. These volcanic activities in this case are considered influx of large masses of nutrients into the photic zone due to the ash accumulation. Therefore, high bio-productivity associated with effective OM preservation contributed to the organic carbon accumulation in the Palana Formation during the Paleocene-Eocene.

Paleoenvironmental reconstruction of the Eocene sediments in the Baiyun sag of the Pearl River Mouth Basin OPEN ACCESS EDITED BY

Article

Aug 2023

A comparative study of the paleoclimate, paleosalinity and paleoredox conditions of Lower Jurassic-Lower Cretaceous sediments in northeastern Iraq

Article

Jul 2023
MAR PETROL GEOL

Evaluating and comparing geochemical sampling protocols in dinosaur eggshells: refining Cretaceous ecosystem research

Article

Jun 2023
CRETACEOUS RES

Paleoenvironmental reconstruction of the Eocene sediments in the Baiyun sag of the Pearl River Mouth Basin

Article

Full-text available

Jun 2023

The Baiyun sag of the Pearl River Mouth Basin has become a focus for deepwater exploration with the highest hydrocarbon potential in northern South China Sea. The Eocene organic-rich mudstones are the main source rocks in the Baiyun sag, and the evolution of their depositional environment remains unclear. Based on the core and geochemical data, we investigated the depositional environments of the Eocene Wenchang and Enping sediments in the Baiyuan sag and revealed the sedimentary environment influences on the formation of the source rocks in the study area. The results indicate that the sediments of the Wenchang and Enping formations were deposited in dysoxic to oxic environments. Moreover, according to the concentrations of salinity-sensitive trace elements, and δ¹³C (-10.9‰ to -7.2‰, average -8.58‰) and δ¹⁸O (-18.4‰ to -14.5‰, average -17.1‰) values of carbonate cement in the sandstone samples, the Wenchang and Enping formations were in fresh water to brackish water conditions during their deposition, with increasing salinity from bottom to top, which suggests that the two formations were mainly deposited in lacustrine environment and the Enping formation experienced a relatively extensive lake transgression. The vertical variations of geochemical characteristics suggest that the Wenchang and Enping formations were deposited under a semi-arid/warm condition and all Eocene sediments experienced mild to moderate chemical weathering, relatively large detrital input and stable paleowater depth. Both primary productivity and preservation conditions played essential roles in controlling the enrichment of organic matters in the Baiyun sag, and the preservation conditions resulted from the restricted water setting. The present work provide a comprehensive analysis of depositional environments based on the abundance of high-resolution geochemical data. The results obtained reveal the dominated factors controlling organic matter enrichment in the Baiyun Sag of the Pearl River Mouth Basin. Those findings are not only significant for understanding the region’s paleogeography, but also provide guidance for future profitable oil and gas exploration in the northern South China Sea and other similar areas.

Strontium isotope stratigraphic insights on the end-Permian mass extinction and the Permian-Triassic boundary in the Dolomites (Italy)

Article

May 2022
CHEM GEOL

The Dolomites (Southern Alps, Italy) is a most significant region to investigate the evolution of shallow-marine ecosystems during the end-Permian mass extinction (EPME). Shallow-marine ecosystems are complex places from an oceanographic viewpoint and combine high biological productivity and ecological diversity. Therefore, establishing the timing and correlation of globally recognisable events in this region are fundamental to interpreting the biological crisis that followed. We took advantage of the Strontium Isotope Stratigraphy (SIS) concept to correlate our stratigraphic succession, ranging from the upper Bellerophon (Bulla Member, upper Changhsingian) to the lower Werfen (Tesero Member, upper Changhsingian - lower Induan) Formations of the Dolomites, to the Meishan (Zhejiang Province, China), the Global Stratotype Section and Point (GSSP) for the Permian–Triassic boundary. We integrated new and previously published ⁸⁷Sr/⁸⁶Sr data from well preserved brachiopods and show that the topmost part of the Bellerophon Formation (the Bulla Member) correlates with bed 24 e-f of the GSSP section, while the Tesero Member, where the Permian-Triassic boundary is located, is characterised by more radiogenic Sr isotope ratios than expected. Differences in Sr isotope ratios may be due to small-scale variations in local paleoenvironmental and paleogeographic conditions/settings. Continental weathering of sedimentary or igneous rocks, distance from terrestrial environment and nearby occurrence of radiogenic rocks might also produce locally variable Sr isotope signatures especially in shallow water environments complicating the application of SIS principles.

Etude de l'hétérogénéité, de la diagenèse et des propriétés réservoirs associées au système sédimentaire carbonaté "Plateforme de Kruja - Bassin Ionien" au Crétacé Supérieur (Albanie)

Thesis

Aug 2021

Jihad Hamd

L’objectif des travaux de recherche menés dans cette thèse est de mieux comprendre les facteurs sédimentaires, diagénétiques et structuraux à l’origine de l’hétérogénéité des systèmes carbonatés réservoirs et de leur propriétés pétrophysiques en contexte de plateforme et de la transition plateforme-bassin. Pour ce faire, les séries sédimentaires de la plateforme carbonatée du Crétacé Supérieur de Kruja et du Basin Ionien adjacent en Albanie ont été choisis et présentent un bon exemple d’analogue terrain de réservoir carbonaté. Les dépôts carbonatés gravitaires de pente et de bassin de ce système forment des réservoirs pétroliers exploités en Albanie, en Grèce ainsi qu'au large de l'Italie. Les analyses sédimentologiques ont été menées sur trois localités dans le centre et le sud de l’Albanie: (i) massif de Krujë-Dajt, (ii) Çorovodë et (iii) Kremenara, dans lesquelles s’affleurent les successions carbonatées du Crétacé Supérieur de plateforme et de bassin. Douze faciès sédimentaires (5 faciès dans les coupes de Çorovodë; 7 faciès dans le massif de Krujë-Dajt) ont été identifiés le long des successions stratigraphiques de plateforme reflétant des environnements de dépôts représentant des conditions allant de subtidal passant par la zone intertidal jusqu’à l’environnement supratidal avec des périodes d’expositions subaériennes. Les faciès identifiés sont intégrés dans des séquences métriques (small-scale sequences) suggérant une cyclicité conduite par des fluctuations haute-fréquence du niveau marin relatif durant le Crétacé Supérieur. Dans le bassin, la période Campanien est caractérisée par d’épais intervalles de dépôts gravitaires calciturbiditiques. Cette succession de dépôts gravitaires montre une épaisseur de ~ 160 m, constitués essentiellement de séquences calciturbiditiques à basse et à forte énergie intercalées avec des dépôts de débris flow représentant une phase stable de système de sédimentation de plateforme-bassin. Au Maastrichtien, une inversion s’opère de la dynamique de sédimentation représentée par trois intervalles de slump résultants du démantèlement de la bordure de plateforme reflétant une déstabilisation de la pente durant cette période.L'étude diagénétique des faciès de plateforme peu profonds des coupes de Çorovodë a révélé que la succession stratigraphique est impactée par une diagenèse marine représentée par de ciments précoces, micritiques, fibreux, aciculaires et aussi en frange, formés dans la zone phréatique marine. Ces ciments sont responsables de la destruction de la porosité primaire intergranulaire et intraparticulaire dans ces faciès. La majorité des ciments identifiés sont liés à des surfaces spécifiques de type « hardground » qui ont été mis en évidence dans plusieurs intervalles le long de la succession étudiée. En revanche, dans le massif de Krujë-Dajt, des ciments calcitiques d’origine marine, d’origine météorique et des calcites tardives ont été identifiés dans la coupe étudiée.

Dolomitization of the Middle Ordovician Ma55 Sub-member of the Majiagou Formation and implications for hydrocarbon exploration in the northern Ordos Basin, NW China

Article

Full-text available

Mar 2021

The Middle Ordovician Majiagou Formation in the northern Ordos Basin consists of a sequence of subtidal and peritidal carbonates that are extensively dolomitized. The diagenetic evolution of the Ma55 Sub-member was investigated to determine the factors controlling reservoir quality in the northern Ordos Basin. Dolomite in the Ma55 Sub-member is classified into three main types on the basis of crystal size: dolomicrite (D1), micritic–silty and fine silty dolomite (D2), and silty (and coarser) dolomite (D3). The Dolomite D1 was produced by dolomitization in a low-salinity diagenetic environment and transformed by near-surface freshwater leaching during shallow burial. The Dolomite D2 developed as a result of post-penecontemporaneous seepage–reflux dolomitization and was affected by later burial dolomitization. The Dolomite D3 was produced during burial dolomitization. Although the original porosity of the Dolomite D1 was low, freshwater diagenesis increased the porosity significantly. As a result of the transformation of montmorillonite to illite, there was a deficiency in the Mg2+ necessary for Dolomite D2 formation, resulting in the nonuniform dolomitization of this type of dolomite. The intercrystalline pores of the Dolomite D2 are mostly filled with montmorillonite and illite, reducing its porosity and permeability and consequently making the Dolomite D2 a poor reservoir. The Dolomite D3 has a higher porosity and contains various types of dissolution and intercrystalline pores, generating a higher permeability. This dolomite is a potential reservoir in the study area and a possible target for oil and gas exploration. Overall, the results of the study suggest that the quality of a potential dolomite reservoir is strongly controlled by the diagenetic history of the host carbonates.

Petrographical and geochemical constraints on carbonate diagenesis in an epeiric platform deposit: Late Cretaceous Bagh Group in central India

Article

Full-text available

Aug 2020

A combined facies, petrography and isotope geochemistry reveal an extensive pedogenic alteration of platform carbonate deposits of the Upper Cretaceous Bagh Group in the western Narmada basin in central India. The highly fossiliferous carbonate sequence of the Bagh Group consists of two formations, the Nodular Limestone at the base, and the Bryozoan Limestone Formation at top. The Nodular Limestone Formation comprises primarily of mudstone and wackestone, with relics of bioclasts such as gastropods, echinoderms, molluscs, forams and calcispheres, reflecting a low-energy supratidal to upper intertidal environment of deposition. Prolonged pedogenesis leads to pervasive micritization, brecciation, desiccation and recrystallization. The overlying Bryozoan Limestone, dominated by packstone and planar laminated rudstone with bryozoans, gastropods, echinoderms/echinoid spines, and molluscs, indicates deposition within the lower intertidal environment with moderately high-energy conditions. Abundant meniscus cement and biomolds suggest meteoric vadose diagenetic modification, whereas, intense secondary micritization of sediments indicates prolonged calichification. The δ13C and δ18O ratios of both Nodular Limestone and Bryozoan Limestone formations are depleted than the normal marine values, indicating an extensive diagenetic resetting of the carbonates. While the meteoric cement is depleted in both δ13C and δ18O ratio, the burial cement shows a decrease of δ18O at constant δ13C. The pedogenetic horizons within the Bagh carbonates bear subtle evidence of subaerial exposures within the overall transgressive Bagh Group. A glauconite bed at the upper part of the Bryozoan Limestone Formation marks the top part of the transgressive deposit.

Origin and paleoenvironmental reconstruction of phosphorus-bearing sandstones of the Cambrian Xinji Formation, southwestern margin of the Ordos Basin, China

Article

Full-text available

Apr 2020
CAN J EARTH SCI

Increasing exploration interest in oil and gas hosted by early Cambrian strata has focused research efforts on early Cambrian sandstones. The origin of phosphorus and the paleoenvironment of phosphorus-bearing sandstones from the Xinji Formation are discussed in this paper. X-ray diffraction, optical microscopy, grain size analysis, total organic carbon, and the concentrations of major, trace, and rare earth elements (REEs) are analyzed in this work. The sandstones are mostly sublitharenite with calcareous cement. The content of the sandstone samples is quartz (39.8%–73.9%), with illite (7.9%–27.6%) and calcite (4.5%–29%). The mineral particles of sandstone samples are mainly well sorted with a fine particle size, suggesting strong paleohydrodynamic force. The value of SiO 2 is 37.69%–78.19%, followed by Al 2 O 3 (6.11%–13.67%). Compared with upper continental crust, the boron in the sandstone samples is relatively enriched, whereas Sc, Sr, and Ba are relatively depleted. The ΣREE content is 124.46–323.99 ppm. Phosphorus is of biogenic origin and enriched by upwelling current. The source of the Xinji Formation sandstone samples was mainly a mixture of sedimentary rock, granite, and alkali basalt, with the provenance of terrestrial clastic materials. The sandstone was deposited under oxic conditions and a warm and humid paleoclimate with saline to brackish features on a passive continental margin. Phosphorus occurring in sandstones is sensitive to paleoclimate and can be used as an indicator to judge paleoclimate, as it is more enriched in warm and humid weather.

Million-year secular variations in the elemental geochemistry of Devonian marine records and a link to global climate and bioevents: Prague Basin, Czechia

Article

Mar 2020
SEDIMENT GEOL

The sedimentary record is affected by periodic and/or random variations in Earth's near-surface conditions, such as the Milankovitch band variations, which are responsible for small-scale cyclicity in distal marine settings. However, the controlling factors of normal field-scale sedimentary cycles operating on Myr-scale that dominate the stratigraphic record remain largely enigmatic. The Lower to Middle Devonian succession (Lochkovian to Givetian) of the Prague Basin, Czechia, is represented by an alternation of largely deep-marine carbonates and shales with typical duration of ~5–7 Myr. We studied the elemental geochemistry of bulk rock samples supported by XRD mineralogy and TOC concentrations. Stratigraphic distribution of the organic-productivity proxies, redox proxies, Ce/Ce* and Pr/Pr* anomalies, and TOC, supported by lithology, allochem composition and field gamma-ray spectrometry, indicates that the Prague Basin was governed by two alternating depositional modes. The oligotrophic mode is characterised by low values of productivity proxies and U/Th ratios, good bottom water oxygenation, heterotrophic skeletal producers, and facies typical of homoclinal ramp settings. The mesotrophic mode is characterised by high U/Th, elevated organic productivity, less oxic bottom conditions, relatively abundant autotrophic skeletal producers and deposition on a distally steepened ramp. The modes were in phase with the Devonian climatically driven environmental changes. We assume that the elevated silicate weathering rates during warmer periods, as previously reported, resulted in higher nutrient input to the seas setting the marine system into the mesotrophic mode. Cooler periods led to oligotrophic water conditions. The global Devonian bioevents show recurrence intervals of the same order as the trophic modes but they typically coincided with the transition between the modes. It is suggested that marine biotic assemblages and the associated carbonate production became unstable during perturbations of the carbon cycle.

Petrologic and geochemical characteristics of high-quality saline lacustrine source rocks in western Qaidam Basin

Article

Full-text available

Nov 2018

The main oil source in western Qaidam Basin is the Paleogene saline lacustrine source rocks. Traditionally, it was considered that these source rocks were characterized by low abundance and poor type of organic matter as well as limited oil generation potential, but this poor source rock condition was very inconsistent with good hydrocarbon exploration results. A previous study has just confirmed that this area develops high-quality source rocks, which is of great significance for recognizing potential of hydrocarbon resource and consolidating confidence to search large and medium-sized oil and gas fields in western Qaidam Basin. Based on fine geochemical analysis of source rocks, petrology, element geochemistry and organic geochemistry are applied to discuss development conditions of high-quality source rocks in this area. The results showed that the saline lacustrine sediments in western Qaidam Basin were deposited in relatively shallow and quiet water with relatively high salinity and low nutrient content; influenced by the drought and cold climate, the terrigenous supply of fresh water was limited, and few aquatic organisms were developed. Good preservation condition is favorable for rapid preservation of oil generating biomass (such as aquatic organisms), to form source rocks rich in hydrogen element with high soluble organic matter content; but relatively lower paleo-productivity makes organic matter abundance lower than that in the eastern saline lacustrine basins. The semi-deep lake, with relatively low salinity and abundant nutrients, is the most favorable are for development of high-quality source rocks; the source rocks have large thickness in the sedimentary depression areas, but due to high water salinity and far away from the provenance area, the water stratification was obvious, so it have moderate to high organic matter abundance.

Evaluation of terrigenous input, diagenetic alteration and depositional conditions of Lower Carboniferous carbonates of Tethys Himalaya, India

Article

Full-text available

May 2018
SE

Geochemical and isotopic signatures from Lower Carboniferous Limestone of the Lipak Formation of Spiti region, Tethys Himalaya (for the first time) have been studied for palaeo-climatic reconstruction of the region and to evaluate the influence of terrigenous input into the Tethyan Ocean. The principal component analysis (PCA) suggests that CaO exhibits different modes of origin as compared to other elements. The low and relatively constant Al/Si ratio (0.19e0.46) of Lipak limestone suggests that Si has multiple sources besides clay minerals. Higher Al 2 O 3 of the limestone than siliciclastic-contaminated carbonates (1.59%) as well as comparable Y/Ho ratio to terrestrial material suggests terrigenous input into the basin. The Er/Nd ratio ranges from 0.07 to 0.18 which further indicates the influence of detrital input (in normal seawater Er/Nd is 0.27). The Mn/Sr ratio suggests insignificant diagenetic alterations. The lack of correlation between Sr and LREE concentration in the limestone (r ¼ 0.036) lends credence to this conclusion. Geochemical palaeo-redox parameters such as negative Mn and positive Ce anomalies (V/V þ Ni) and Th/U ratios indicate that the limestone was deposited in anoxic environmental conditions. d 18 O and d 13 C isotope composition of whole-rock samples ranges from À10%o to À24%o and þ3.34%o to À8.24%o respectively indicating significant climatic change during Carboniferous period. These observations are consistent and match with those of contemporaneous carbonates elsewhere in the world, which can be linked to the alternative occurrences of cold and warm paleoclimates in the Carboniferous. The onset of the Permo-Carboniferous glaciation would have resulted in more positive d 13 C and less negative d 18 O values for these carbonates. The isotopic values also indicate eustatic sea level changes due to the glacial and interglacial phases during the period. Thus the signatures of Gondwana glaciation events are well preserved in the Lipak limestone of Spiti region.

Evaluation of terrigenous imput, diagenetic alteration and depositional conditions of Lower Carboniferous carbonates of Tethys Himalaya, India

Article

Full-text available

May 2018

Javid Ahmad Ganai

Geochemical and isotopic signatures from Lower Carboniferous Limestone of the Lipak Formation of Spiti region, Tethys Himalaya (for the first time) have been studied for palaeo-climatic reconstruction of the region and to evaluate the influence of terrigenous input into the Tethyan Ocean. The principal component analysis (PCA) suggests that CaO exhibits different modes of origin as compared to other elements. The low and relatively constant Al/Si ratio (0.19–0.46) of Lipak limestone suggests that Si has multiple sources besides clay minerals. Higher Al2O3 of the limestone than siliciclastic-contaminated carbonates (1.59%) as well as comparable Y/Ho ratio to terrestrial material suggests terrigenous input into the basin. The Er/Nd ratio ranges from 0.07 to 0.18 which further indicates the influence of detrital input (in normal seawater Er/Nd is 0.27). The Mn/Sr ratio suggests insignificant diagenetic alterations. The lack of correlation between Sr and LREE concentration in the limestone (r = 0.036) lends credence to this conclusion. Geochemical palaeo-redox parameters such as negative Mn and positive Ce anomalies (V/V + Ni) and Th/U ratios indicate that the limestone was deposited in anoxic environmental conditions. δ¹⁸O and δ¹³C isotope composition of whole-rock samples ranges from −10%o to −24%o and +3.34%o to −8.24%o respectively indicating significant climatic change during Carboniferous period. These observations are consistent and match with those of contemporaneous carbonates elsewhere in the world, which can be linked to the alternative occurrences of cold and warm paleoclimates in the Carboniferous. The onset of the Permo-Carboniferous glaciation would have resulted in more positive δ¹³C and less negative δ¹⁸O values for these carbonates. The isotopic values also indicate eustatic sea level changes due to the glacial and interglacial phases during the period. Thus the signatures of Gondwana glaciation events are well preserved in the Lipak limestone of Spiti region.

刘丽静--2016---Calcified rivulariaceans from the Ordovician of the Tarim Basin, Northwest China, Phanerozoic lagoonal examples

Data

Full-text available

Oct 2016

Calcified rivulariaceans from the Ordovician of the Tarim Basin, Northwest China, Phanerozoic lagoonal examples, and possible controlling factors

Article

Sep 2015
PALAEOGEOGR PALAEOCL

A distinctive association of rivulariacean-like calcified microfossils is recognized in back-reef lagoon facies on the Bachu-Tazhong Platform in the Lianglitag Formation (Katian Stage, Upper Ordovician) of the Tarim Basin, based on investigation of 4500 thin sections from 35 well drill cores. The genera include Hedstroemia, Ortonella, Zonotrichites, Cayeuxia, and Garwoodia, most of which have features comparable with present-day calcified cyanobacteria such as Rivularia, Calothrix and Dichothrix (Rivulariaceae, Nostocales). A similar association is present in lagoonal and other restricted nearshore shallow-marine carbonate environments during much of the Paleozoic and Mesozoic. This suggests the sustained presence of a rivulariacean-dominated cyanobacterial association characteristic of back-reef/lagoonal environments. At the present-day, uncalcified Rivularia, Calothrix and Dichothrix remain common in back-reef, lagoon, mangrove-swamp, rocky shore, salt-marsh, and saline lake environments. The ability of these cyanobacteria to grow in environments low in inorganic nitrate and phosphate could be help to explain this distribution. Cenozoic decline in marine calcified rivulariaceans is attributed to global reduction of seawater carbonate saturation state. The Phanerozoic record of calcified rivulariacean cyanobacteria appears to sensitively reflect long-term variations in the carbonate and nutrient chemistry of marine environments.

Characterizing and modeling the Upper Jurassic Arab-D reservoir using outcrop data from Central Saudi Arabia

Article

Full-text available

Apr 2014
GEOARABIA

Outcrop analogs are used to improve the characterization of reservoir stratigraphy, to understand subsurface facies architecture and heterogeneity, and to overcome the limitations associated with large inter-well spacing within individual oil fields. This study characterized and modeled outcropping strata equivalent to the Upper Jurassic Arab-D carbonate reservoir in Central Saudi Arabia. The study presents qualitative and quantitative sedimentological and petrographic descriptions of lithofacies associations and interprets them within a high-order stratigraphic framework using geostatistical modeling, spectral gamma-ray, geochemistry, petrography and micropaleontology. The sedimentological studies revealed three lithofacies associations, which are interpreted as a gentle slope platform depositional environment comprising nine high-frequency sequences. The biocomponents of the study area show a lower degree of diversity than the subsurface Arab-D reservoir; however, some key biofacies are present and provide indications of the nature of the paleoenvironments. The geochemical results show a strong correlation between the major and trace elements and the reservoir facies, and suggest that the concentrations of elements and their corresponding spectral gamma-ray logs follow the same general upward-shoaling pattern. The 3-D geocellular model captures small-scale reservoir variability, which is reflected in the petrophysical data distribution in the model. This investigation increases the understanding of the stratigraphy of the Arab-D reservoir and provides a general framework for zonation, layering, and lateral stratigraphic correlations.

Galasy na liściu paproci z dolnej jury Gromadzic (Góry Świętokrzyskie) - przykład interakcji rośliny - zwierzęta

Conference Paper

Full-text available

Sep 2011

Grzegorz Pacyna

Geochemical analysis of mass mortality events in the Cretaceous (Aptian) Konservatt-Lagerstätte of Crato paleolake, Brazil

Article

Oct 2024
PALAEOGEOGR PALAEOCL

Geochemical records from the Cretaceous (Aptian) Crato paleolake in Brazil reveal the influence of volcanism and wet-dry paleoclimatic variations on the lake system and improve understanding of the mass mortalities represented by Konservat-Laggerst¨ atte assemblages in the deposits. Specifically, we used paleoredox (PbEF, MnEF, UEF, VEF, MoEF, FeEF, V/Cr and U/Th ratios) and paleoproductivity (PEF, CuEF, ZnEF, NiEF, BaEF, and δ13CVPDB) indexes to elucidate changes in detrital input (Al and Fe), paleoclimate (Sr/Cu, C- values, Sr/Al and Mg/Al), paleosalinity (Sr/Ba and Rb/K), and lake level (Fe/Mn and δ18OVPDB), and their linkage to episodes of volcanism (Hg/Al and Hg/Fe). The mass mortalities of lacustrine organisms are found to be closely related to paleoclimatic variations. During dry episodes, the lake became more saline and alkaline, which impeded the larval development and the maturation of mayflies (Ephemeroptera), and triggered mass mortality events of these organisms. During wet periods, metal enrichment indicates that a rise in paleoproductivity may have caused hypoxia, thereby inducing the mass mortality events among Dastilbe fish. Mercury anomalies suggest that extrusion of Rajmahal-Kerguelen Plateau basalts in the late Aptian times influenced regional paleoclimatic and depositional processes, and may have been ultimately responsible for generating the Konservat-Lagerst¨ atte of the Crato paleolake.

Ypresian–Lutetian platform evolution in the Indus Basin, Southwestern Pakistan: An interplay between local and regional tectonic changes

Article

Jul 2024
SEDIMENT GEOL

The present investigation aims to analyze the depositional environment, sequence stratigraphy, and geochemistry of the Early-Middle Eocene succession in the Laki Range of the Southern Indus Basin, Pakistan. The sequence is subsequently correlated with other sections within the Southern Indus Basin, Central Indus Basin, Upper Indus Basin, and Hazara Basin in Pakistan. For this study, the Lakhra and Laki formations were sampled from four sections in the Laki Range. Based on detailed outcrop observations， eight lithofacies were identified including four clastic lithofacies (CLF-1 to 4) and four limestone lithofacies (LLF-1 to 4). Similarly， based on detailed petrographic examination， seven microfacies were identified in limestone units. Considering the biotic paleoecology, facies texture, and chemical composition, depositional environments were assigned to the microfacies and lithofacies. All the microfacies， and the shale and sandstone lithofacies (CLF-1 and CLF-4) represent shallow inner to deeper outer-shelf settings whereas the other two lithofacies (CLF-2 and CLF-3) represent deltaic and tidal flat settings, respectively. All the microfacies and lithofacies information was used to establish sequence stratigraphy for the studied strata. The top of the Lakhra Formation and the whole of the Laki Formation in the Bara Nala Section (BNS) represent two complete, and two partial, third-order sequences, further divided into fourth order and small-scale cycles. The sequence's development is primarily influenced by regional and local tectonics. The regional correlation of the Indus Basin and Hazara Basin indicates that the regional basin's bathymetry and resultant depositional sequence were significantly influenced by the Himalayan Orogeny. The regional depositional pattern indicates that subsequent to India-Asia collision, the closure of eastern Tethys took place in a temporal succession from northwestern to the southwestern parts of the Indus Basin. In the Central Indus Basin, marine environments persisted until the Priabonian Stage (SBZ20) compared to those of the Upper (SBZ11–12) and Southern (SBZ13–14) Indus basins. This study offers valuable insights into both the local and regional depositional frameworks and the influence of local and regional tectonics on a carbonate platform evolution.

Characteristics of the Cenomanian-Turonian oceanic anoxic event 2 and its impact on the organic carbon accumulation in the Abu Roash (F) organic-rich carbonate rocks in the Abu Gharadig Field, Egypt

Article

Jul 2024

Paleoenvironment evolution and organic matter enrichment mechanisms in the first member of the Qingshankou Formation, Songliao Basin, China

Article

Jun 2024

Organic matter is the basis for oil and gas generation, and the depositional environment controls its enrichment. The first member of the Qingshankou Formation (K2qn1) in Songliao Basin has a thick organic-rich shale and so is an important target section for shale oil exploration and development. In the Gulong Sag, shale samples from this unit were collected over the full length of the section. The characterization of the environments of deposition (EOD) of K2qn1 was improved by utilizing lithological characteristics, thin section observations, elemental compositions, and organic carbon concentrations. Combined with the normalization coefficients proposed in this paper, an organic matter correlation model was established to elucidate the factors that influence organic matter enrichment. From the bottom to the top of K2qn1, the lake depth gradually becomes shallower, the primary productivity first decreases and then increases, the reducing conditions become stronger and then weaker, the water salinity gradually decreases, the climate first becomes semi-humid and then warm and humid, and the input of terrigenous debris first decreases and then increases. A major marine transgression at the base of the K2qn1’s brought in nutrients to increase primary productivity, and the density-stratified reducing environment preserved and enriched organic matter. High primary productivity occurred during the middle of the deposition of the K2qn1, while terrigenous input is low. Organic matter is preserved in reduced deep lake environments, resulting in organic matter-rich black shale. The lake became shallower, and the salinity decreased in the upper part of K2qn1. Benthic organisms rapidly multiplied, consuming large amounts of oxygen and destroying the previously depositional environment, resulting in a reducing environment disturbed by benthic organisms with poor preservation conditions and the lowest organic matter content.

Mineralogy and Geochemistry of the Paleocene-Eocene Palana Formation in Western Rajasthan, India: Insights for Sedimentary Paleoenvironmental Conditions and Volcanic Activity

Article

Full-text available

Jan 2024

Organic-rich shale rocks from the Paleocene-Eocene Palana Formation in western Rajasthan, India, were systematically investigated based on inorganic and organic geochemistry combined with microscopic examinations to evaluate the sedimentary paleoenvironmental conditions and volcanic activity and their impact on the high organic carbon accumulation. The Palana shales are categorized by high organic matter (OM) and sulfur contents, with total values up to 36.23 wt.% and 2.24 wt.%, respectively. The richness of phytoplankton algae (i.e., telalginite and lamalginite) together with redox-sensitive trace elements further suggests a marine setting and anoxic environmental conditions during the Paleocene-Eocene. The significant low oxygen conditions may contribute to enhancing the preservation of organic matter during deposition. The mineralogical and inorganic geochemical indicators demonstrate that the Palana organic-rich shale facies was accumulated in a warm and humid climate with moderate salinity stratification conditions in the water columns, thereby contributing to the high bioproductivity of the phytoplankton algae blooms within the photic zone. The presence of significant contents of zeolite derived from volcanic material together with silica minerals such as apophyllite and tridymite in most of the Palana organic-rich shales indicates a volcanic origin and supports hydrothermal activities during the Paleocene-Eocene period. These volcanic activities in this case are considered the influx of large masses of nutrients into the photic zone due to the ash accumulation, as indicated by the presence of the zeolites in the Palana shales. Therefore, the high bio-productivity associated with effective OM preservation led to the organic carbon accumulation in the Palana Formation during the Paleocene-Eocene.

Stable isotopes and rare-earth elements of carbonate rocks, Paleocene–Eocene Kolosh Formation, High Folded Zone, NE Iraq: implication for depositional environment and Diagenesis

Article

Full-text available

Oct 2023

Petrographic and geochemical studies were carried out on the Paleocene–Eocene carbonates of the Kolosh Formation in the High Folded Zone to infer the environment of deposition, diagenetic overprints, and their origin. The petrographic study revealed five main microfacies; packstone, wackestone, mudstone, grainstone, and crystalline carbonate. There are different depositional environments from shoal to shallow marine environments (mid-ramp conditions) that are adequate for mixing continental material with seawater. Several evidences of diagenetic processes were observed, such as micritization, neomorphism, and dolomitization. Petrographic and geochemical analyses show the dominance of calcite and dolomite minerals. The contents of major oxides and the concentrations of trace elements were normalized to Post-Archean Australian Shale (PAAS) values. The Paleocene–Eocene carbonates are enriched in CaO, MgO, Cr, and Ni, whereas are highly depleted in Na2O, K2O, TiO2, Al2O3, Rb, Ba, Th, and Zr. The low contents of Al2O3 and SiO2 refer to a low siliciclastic involvement during the deposition of the Paleocene–Eocene carbonate. The REEs average content is lower (15.60 ppm) than that of marine carbonates (28 ppm). The REE patterns (normalized to PAAS) display a seawater-like type, while a slightly lower average Y/Ho value (33.66) relative to that of typical seawater (~ 44 to 74) refers to the alteration of the seawater by the freshwater. The REEs of this study are comparable with the limestone of the Middle Eocene Fulra Formation and Arabian Sea carbonates. Paleocene–Eocene carbonates have δ¹³CPDB ranging between − 13.31 and 1.25‰PDB, and δ¹⁸O from − 6.30 to 0.12‰PDB. The negative values and no correlation between δ¹³C and δ¹⁸O indicate that modification of the primordial composition of the isotopes is not a result of diagenesis only, but other factors, such as temperature, and organic matter have an important role. The negative Ce/Ce*, Th/U ratios, and authigenic U suggest their accompanying the deposition of the carbonates in oxidizing conditions. The paleotemperature of the studied carbonates (~ 12 to 42 °C) is slightly higher than other global records in the Paleocene–Eocene, which may propose the variations in the composition of oxygen isotope and modification in the geochemical characteristics during the post-carbonate deposition time.

Diagenetic Processes and Geochemical Propertiesof the Elika Formation in Gadamgah Anticline in South of Central Alborz

Article

Aug 2020

Investigation of sedimentary facies and geochemical parameters of the Asmari Formation (Oligocene-Miocene) in the Shadegan Oil Field, Dezful Embayment, SW Iran

Article

Jul 2022

Abstract: In this research, depositional environment and geochemical studies of the Asmari Formation with 363.9 meters thickness were investigated in well-11 of the Shadegan Oil Field in the Dezful Embayment, Zagros Basin. In the Shadegan Oil Field, the Asmari Formation consists mainly of limestones and porous dolostones associated with sandstones, and shales. In the SG-11 well, The Asmari Formation with Oligocene (Chattian) and lower Miocene (Aquitanian-Burdigalian) in age conformably overlies the marly and shaly Pabdeh Formation and is, in turn, conformably overlain by the evaporites of the Gachsaran Formation. Twenty six carbonate-evaporate microfacies were identified, that are deposited in four main settings comprises of inner ramp, mid ramp, outer ramp and basin. Depositional environment of the Asmari Formation proposed as a homoclinal ramp. Geochemical and petrographic studies of Asmari carbonates suggests that aragonite was the original carbonate mineralogy of this formation. The δ18O values of the Asmari limestones range from –8.96 to -0.85‰PDB (mean –2.99‰PDB), and the δ13C values range from -5.86 to +1.56‰PDB (mean -0.74‰PDB). The results of this study indicate that the stable-isotope composition of the Asmari limestones is fairly original and was in quite good isotopic equilibrium with the Palaeogene-Neogene seawater. Some samples were affected, however, by later diagenetic processes during burial depth in a closed to semi-closed diagenetic system. Relatively high ratio of Sr/Mn also indicates a low water/rock interaction in a closed to semi-closed diagenetic system for the carbonates of the Asmari Formation. One of the δ18O-depleted samples (-8.96‰) yields a temperature of 68.8 °C, which must, obviously, represent a temperature during burial diagenesis and one of the δ18O-enriched samples (-0.85‰) gives a minimum syn-sedimentary temperature of only 23 °C. Keywords: Shadegan Oil Field, Oxygen and carbon isotopes, Oligocene-Miocene, Asmari Formation, Diagenetic system.

Stratigraphic Modelling of the Lower/Middle Oxfordian (Upper Jurassic) Outer Ramp Deposits from the NE Paris Basin (France)

Article

Full-text available

Oct 2022

We investigate herein the lateral and vertical lithological heterogeneities of the Lower/Middle Oxfordian deposits (“Terrain à Chailles” and “Marnes des Eparges” formations) in the north-eastern Paris Basin. This new detailed stratigraphic framework documents the evolution at high resolution of an outer ramp based on regional correlations in order to constrain the evolution of petrological properties between the clayey “Argiles de la Woëvre” Formation and the more calcareous “Marnes et Calcaires à Coraux de Foug Formation. The “Argiles de la Woëvre” Formation is targeted for the deep storage of nuclear waste in north-eastern France. Nine wells are correlated over the “Zone of Interest for Further Research” (ZIRA), defined by the French agency for radioactive waste management (Andra), with a resolution of 0.5–1.0 m. The architecture and the age control of these formations have been refined, revealing that the “Terrain à Chailles” Formation is characterised by a regular slightly inclined sedimentation gently deeping in the SW direction and shows a lithological evolution from silty claystones to an increased occurrence of its calcareous content towards the top (Lower Oxfordian, uppermost mariae and cordatum ammonite zones). The above “Marnes des Eparges” Formation, characterised by claystone limestone alternations, is assigned to the Middle Oxfordian (plicatilis ammonite zone), deposited during a slightly enhanced subsidence phase in the SE part of the basin and documented and associated with onlaps geometries on the more proximal areas. However, this change in geometry does not affect petrological properties over ZIRA, as this is not accompanied by lithological changes. The environmental factors controlling petrological heterogeneities over ZIRA are also discussed. The stepwise increase in the carbonate content and the decrease in the detrital content towards the Lower to Middle Oxfordian deposits was likely triggered by a climate change towards drier conditions, modulated by sea level changes on a ramp morphology. A major condensation phase encompassing most of the Lower Oxfordian cordatum ammonite zone is also highlighted. The occurrence of a maximum regressive surface associated with gentle slope topography is a probable trigger for condensation. Changes in geometries are, however, associated with the activity of the Metz Fault, which potentially had an influence on the subsidence rates of the basin at that time.

Multiproxy analysis constraining climatic control over the Cenozoic depositional history of Kachchh, Western India

Article

Jun 2022

A well-developed 86 m-thick Cenozoic sedimentary succession in the Matanomadh area, western Kachchh, was studied to assess the stratigraphic positions of different units, ascertain depositional environments, and the degree of climatic controls over time depositional processes. Age-diagnostic nannoplankton species Cyclicargolithus floridanus (46.29–12.1 Ma), Reticulofenestra dictyoda (53–30.8 Ma), Reticulofenestra minuta (50.5–2.59 Ma) and foraminiferal species, for example, Orbulinoides beckmanni (41–39.5 Ma) found across studied units envisage the stratigraphic age and palaeoenvironment. CaO with strong negative elemental correlation, binary/ternary discriminant tectonic and depositional regimes cross-plot from units indicate the biogenic origin of limestones and shales were formed in typical passive, marginal, shallow littoral settings with plausible detritus influx from Deccan basaltic provenance. Total organic carbon with TE-REE respectively connotes a sedimentation process in a nearly consistent open shallow marine, locally transient semi-restricted marginal basin in a tropical-equatorial region. Furthermore, principal component analysis (PCA) of weathering indices based on elemental abundance and X-ray diffraction data of clays deterministically suggest with empirical relation between humid tropical climate-induced weathering and fluctuant terrestrial influx. Palaeoredox indices with biological data demonstrate localized redox-stratified conditions. However, coherent signatures of the global events such as Eocene Thermal Maximum-2, Middle Eocene Climatic Optimum, and Mid Miocene Climatic Optimum can be traced and validated by synthesizing geochemical data for direct/indirect estimation of sediment routing, rainfall (αAlMg and αAlCa) and climate proxies (PCA), productivity indices (Babio, Cubio and Nibio), and localized periodic oxic-dysoxic environment (V/Cr, U/Th, Ni/Co) from core samples.

Petrography and geochemistry of the Middle-Upper Jurassic Banik section, northernmost Iraq -Implications for palaeoredox, evaporitic and diagenetic conditions

Poster

Full-text available

Nov 2021

Petrography and geochemistry of the Middle-Upper Jurassic Banik Section, northernmost Iraq -Implications for palaeoredox, evaporitic and diagenetic conditions

Article

Full-text available

Jun 2020
Neues Jahrbuch Geol Palaontol Abhand

Lithological, petrographic, and geochemical analysis of the Middle to upper Jurassic succession (i.e. Sargelu and Naokelekan formations) from northernmost Iraq were undertaken with the aim of providing an updated discussion for their sedimentary and diagenetic histories, as well as examining the evaporation proxies and paleoredox conditions under which these two formations were deposited. Lithologically, the Sargelu Formation comprises massive dolomites, interbedded with shales, rare cherts and one single limestone bed, whilst the Naokelekan Formation consists of shales overlain by limestones and one single dolomite bed. Petrographic analysis of both formations revealed the presence of rare ostracods, bioclastic fragments as well as calcispheres. Five main microfacies were recognized, including bioclastic wackestone, mudstone, dolorudite, dolarenite and dolomicrite microfacies. The shales comprise clay minerals assemblages (illite/muscovite and kaolinite) with some quartz, alkali feldspar and rare pyrite. The Sargelu Formation was probably deposited in a shallow-marine environment. In contrast, the Naokelekan Formation is hypothesized to be deposited in a restricted shallow-lagoon environment. Palaeoredox indicators suggest that both formations were accumulated under anoxic conditions, most probably in silled basins where water circulation was restricted. Tectonic activity thus resulted in basin compartmentalization across the region, which also explains the marked differences which are often observed. 3

Sedimentary environment, sequence stratigraphy and elemental geochemistry of the Taleh Zang Formation in the South of Kermanshah

Article

Full-text available

Jul 2019

In this study, for the first time depositional conditions, sequence stratigraphy and elemental geochemistry of the Taleh Zang Formation with Paleocene to Lower Eocene age in the Kermanshah province (Kaboutar Bala section) have been evaluated. In this section, the Taleh Zang Formation conformably overlies the Amiran Formation and is overlain by the Kashkan Formation with a disconformity surface. Field and microscopic studies led to recognition of six microfacies within the succession. Gradual microfacies change, the absence of calciturbidites and lack of extensive barrier reefs with considerable thickness, confirms a carbonate ramp. Sequence stratigraphic studies led to the identification of one-third order depositional sequence which includes TST and HST facies association. The lower boundary of this sequence, specified as type II and the upper boundary with evidences of subaerial exposure is type I. The maximum flooding surface (MFS) is determined with bioclastic coral corallinacea floatstone/rudstone microfacies of proximal middle ramp. The results of geochemical analysis of major elements (Ca, Mg) and minor elements (Sr, Na, Mn and Fe) indicate that the original carbonate mineralogy is aragonite and diagenetic system is semi-close to open system. Trend of elements changes along this stratigraphic section shows that in the HST sediments, the amount of Sr is decreased, while Fe and Mn are increased due to more meteoric diagenetic effect. Keywords: Taleh Zang Formation, Sedimentary Environment, Sequence Stratigraphy, Elemental Geochemistry, Kermanshah. Introduction The Taleh Zang Formation is part of Lower Paleogene (Upper Paleocene–Middle Eocene) in the Lorestan zone of Zagros basin (Aghanabati 2010). At the type locality, this formation conformably overlies Cretaceous beds of marl and siltstone belonging to the Amiran Formation and is overlain by the Kashkan Formation with an unconformity (Aghanabati 2010). The thickness of the Taleh Zang Formation is very variable, as in some areas, this formation is absent and the Kashkan Formation directly overlies the Amiran Formation (Rajabi et al. 2011). In this paper the carbonate deposits of the Taleh Zang Formation in the Kermanshah province (Kaboutar Bala section) have been studied for the first time. The previous study of the Taleh Zang Formation in the Kermanshah province are focused on the biostratigraphy and also the components of this current study is different from other sections in the Lorestan zone (such as the absence of larger benthic foraminifera e.g. nummulitidae, alveolinidae and discocyclinidae and presence of corals and algae). So in this research for the first time depositional conditions, sequence stratigraphy and elemental geochemistry of the Taleh Zang Formation in the Kermanshah province (Kaboutar Bala section) have been evaluated. Material & Methods: For the present study, one surface section of the Taleh Zang Formation in the south of the Kermanshah region (Kaboutar Bala section) has been studied. The section measured a total thickness of 65 m and consists of limestone, dolomitic limestone, dolostone and minor amount of marl. During the fieldwork studies, 33 rock samples from carbonate deposits (limestone and dolostone) have been taken for petrographic studies. In order to differentiate ferroan and non-ferroan calcite from ferroan and non-ferroan dolomite in thin sections, the staining method of Dickson (1965) was applied. According to the methods of some researchers such as Haq et al. (1987) and Posamentier et al. (1988), depositional sequences were recognized. Elemental geochemistry analysis were performed form 12 samples of carbonates at the geochemistry laboratory of Shahid Beheshti University, Iran. Discussion of Results & Conclusions Based on the field and petrographic studies, the microfacies and depositional environment of the Taleh Zang Formation were recognized. This formation in the Kaboutar Bala section have been made of six microfacies which occur in four facies belts. The tidal flat sediment is composed of dolomicrite with ranging in size from 4 to 16 µm and contain silt-size quartz grains. Many researchers believe that dolomicrite forms during very early diagenesis in supratidal to intertidal environments (e.g. Sibley and Gregg 1987; Adabi 2009). From the shoreline towards the seas, the lagoon facies belt consists of two microfacies; bioclastic benthic foraminifera peloidal wackestone, and bioclastic benthic foraminifera dasycladacea wackestone to packstone. The lack of marine biota and abundant components of restricted biota (such as miliolids and dasycladacea), represent a restricted conditions in the lagoon environment (Bachmann and Hirsch 2006; Adabi et al. 2015; Kahsnitz et al. 2018). Barrier facies belt is composed of coral boundstone microfacies with limited lateral extension. The main components of this microfacies are only corals. The dominance of coral colonies indicate a high energy environment in the barrier facies belt (Vescogni et al. 2016; Ghafari et al. 2017). The open marine facies belt includes coral floatstone and bioclastic coral corallinacea floatstone/rudstone microfacies. The common coral debris may have derived from erosion of pre-existing coral colonies (in the barrier facies belt) by currents and/or storms (Roozpeykar and Maghfouri Moghaddam 2015; Shabafrooz et al. 2015). Gradual microfacies change, the absence of calciturbidites and lack of extensive barrier reefs with considerable thickness, confirms a carbonate ramp . Based on the sequence stratigraphic studies, one depositional sequence was identified in the studied sequence. The lower boundary of this sequence is located at the base of the formation and specified as type II. The upper boundary with evidences of subaerial exposure and the presence of siliciclastic Kashkan Formation specified as type I. The MFS is determined with bioclastic coral corallinacea floatstone/rudstone microfacies belonging to the proximal middle ramp. Geochemical analysis in limestone parts of the formation including Ca (37.57–39.25%), Mg (0.25–1.3%), Sr (964–1833 ppm), Na (65–160 ppm), Mn (161–421 ppm) and Fe (281–2107 ppm), and their variations indicate that the original carbonate mineralogy is aragonite and diagenetic system is semi-close to open system. Variation trends of elements along the stratigraphic column shows that the amounts of elements in the TST and HST are different from each other. Generally in the HST sediments, the amount of Sr is decreased, while Fe and Mn are increased due to more meteoric diagenetic effect at this part of the sequence.

Sedimentological and Geochemical Analysis of the Middle Jurassic Shinawari Formation, Upper Indus Basin, Pakistan: Implications for Palaeoenvironmental and Hydrocarbon Assessment

Article

Full-text available

Feb 2019

Microfacies, palynofacies, and hydrocarbon source rock potential of Toarcian–Bathonian sediments of the Shinawari Formation are investigated in the Chichali Nala Section, Baroch Nala, Gulla Khel Nala, Surghar Range, and Askari Cement Factory Section, Nizampur Kala Chitta Range, Pakistan. The Shinawari Formation is dominated by a mix of limestone, sandstone, shale, marls, siltstone, and mudstone units with the association of laterite, hard grounds, coal layers, and coal disseminations. Microfacies analysis suggests that deposition of the Shinawari Formation occurred in peritidal lagoon, beach shoal to distal shelf setting. This interpretation is supported by sub-types of standard Tyson (in: Sedimentary organic matter, Springer, Berlin, 1995), palynofacies, which we have defined as palynofacies SFPF-A, attributed to a marginal dysoxic to an anoxic basinal setting, and palynofacies SFPF-B, deposited in heterolithic proximal platform settings. Some of the intervals have low (

\le 0.5\%

) total organic carbon (TOC) values except for intervals with fair values (0.5–2.09%) in the Shinawari Formation in different stratigraphic sections. Despite some lower TOC values, and the presence of kerogen types III and II, spore colouration index of 5.0–8.0, thermal alteration index of 2–3+, and vitrinite reflectance (VR) of 1.16–1.35 indicate possible hydrocarbon source rock potential. The various geochemical plots obtained from TOC (%), VR and Rock-Eval pyrolysis data indicate that the Shinawari Formation specifies kerogen type III having Tmax (

{}^{\circ }

C) range of 430–450

{}^{\circ }

C and thermal maturity lies in the oil window.

Coral patch reef system and associated facies from southwestern Gondwana: paleoenvironmental evolution of the Oxfordian shallow-marine carbonate platform at Portada Covunco, Neuquén Basin, Argentina

Article

Jan 2017

During the Middle Oxfordian, the epicontinental shelf of the Neuquén Basin was a site of major coralline evolution and reef building. This work expounds the studies performed on the La Manga patch reefs at Portada Covunco locality, near Zapala city, Neuquén province. Based on the results of 12 facies/microfacies types and the vertical succession of coral morphotypes a shallowing-upward trend ranging from a shallow subtidal-lagoon- to intertidal settings is inferred. The microfacies model suggests an ooidal shoal area in the highest energy zone and various patch reefs on the shallow carbonate platform. Autochthonous reefal facies comprise a low diversity of platy coral and mixed coral-siliceous sponge framestone, ramose coral bafflestone, and microbial bindstone. Non-reefal facies are composed of ooidal packstone, bedded bioclastic wackestone-packstone, and marl levels. Several shallowing-upward episodes are evidenced by local erosional surfaces (main exposure surface-MES). The succession of platy corals (exclusively Australoseris) followed by ramose corals (Etallonasteria, Stelidioseris, and Stephanastrea rollieri) probably reflects local environmental changes. The upward change in reefal composition is best interpreted in response to extrinsic physical parameters (local relatively minor sea-level fluctuations). Siliceous sponges occur in low percentages. The La Manga reefal succession could be correlated with the “global carbonate reef event”. This event occurred in most basins associated with the Tethyan oceanic belt and the North Atlantic Ocean, in low paleolatitude. The Portada Covunco reefs grew at higher paleolatitudes (nearly 39° south), within an embayment of the Neuquén Basin, with open circulation to the paleo-Pacific Ocean on the southwestern margin of the Gondwana realm.

Characteristics of sedimentary geochemistry and evolution of platform of the Lianglitag formation carbonate, Upper Ordovician in Tahe Oilfield

Article

Jan 2010

The Upper Ordovician Lianglitag Formation, Tahe Oilfield, mainly consists of micrite, nodular limestone in the lower member and oolitic limestone, bioclastic limestone, calcarenite, calcirudite in the upper member,which constitutes a shallowing upward sedimentary sequence. Based on sequence stratigraphy research, the Lianglitag Formation is a integral three-order sequence, which is composed by two systems tracts. By means of detail investigation in petrographic and geochemical characteristics of stratigraphic units in every systems tract, the palaeogeographic and sedimentary facies distribution are recognized. There are three kinds of facies belts during upper Ordovician in Tahe Oilfield: platform, platform margin and slope facies,which is approximately east-west strike and distribute orderly from north to south in the plane. Analysis of trace elements and rare earth elements further support and improve the analysis of sedimentary facies. The content of VNNi and Cr trace elements shows a overall increasing trend from shallow to deep water facies, as well as the abnormal curve of Ce is a good reflection about the sedimentary environment and the Sr/Ba ratio shows abnormally high values in platform margin.

Sedimentological and diagenetic influences on low permeability properties of the Middle Jurassic limestones (Paris Basin, France)

Article

Dec 2009

Benjamin Brigaud

A detailed sedimentological, geochemical and mineralogical study is carried out on the Early Bajocian to Early Callovian (Middle Jurassic) limestones of the Paris Basin. Deposits include 18 lithofacies which are stacked into 10 third-order depositional sequences. Our geochemical study including a compilation of bibliographic data allows us to refine the existing sea surface palaeotemperature pattern. A cooling from the latest Early Bajocian to the Late Bajocian and a subsequent warming from the earliest Callovian to the Early/Middle Callovian transition are described using a proxy of sea surface temperatures. Together with δ13C and mineralogical data, our new δ18O values suggest a palaeo-climatic/palaeo-environmental control of facies in this shallow carbonate ramp environment. Using petrographic and geochemical analyses (stable O and C isotopes, Sr isotopes, major elements), we identify six calcitic spar stages, two dolomite stages, and several episodes of fracturing and stylolitization ordered in paragenetic sequence, reducing significantly the porosity during the burial diagenesis. Cement quantification shows the predominance of two blocky calcite cement stages (75% of total cementation). Lateral meteoric recharge may have occurred as a result of two separate uplift events (Late Cimmerian Unconformity and Late Aptian Unconformity) and the related exposures of carbonates to the north of the study area during the Early Cretaceous. This palaeohydrological circulation brought about a significant reduction of porosity (from 40% to 10%) through calcite cement precipitation. Two porous levels (PL1 and PL2; Φ=15-20%) are detected at the top of the Dogger formation (Calcaire de Chaumont –Bathonian) in the study area. They form the carbonate reservoir levels. Their permeability is variable: high for PL1 (k=100-700mD) corresponding of macroporous grainstones (deposited in a ooid shoal), and low for PL2 (k=0,1-1mD) within muddy facies dominated by intercrystalline microporosity (deposited in protected lagoon). The sedimentological and diagenetic study shows the existence of PL1 and PL2 can be summarized in 3 stages: (1) lithification and early mineralogical stabilization (aragonite and high magnesium calcite to low magnesium calcite) below exposure surfaces (SB7 and SB8) which rigidify the sediment (grainstone or micrite), prevent compaction and favor the preservation of the primary porosity; (2) low meteoric recharges and cementation (Bc1 and Bc2) during the Cretaceous due to the Marnes à Rhynchonelles, acted as a lateral permeability barrier, which prevent lateral phreatic circulations and cementation at the top of the Dogger formation; (3) very low hydrothermal circulations and cementations (dolomite, Bc3 and fuorite) during the Oligocene. These 3 factors were combined only in PL1 and PL2, on a very low thickness (20 m) compare to the 210 m completely compacted and/or cemented forming the the Dogger.

Sedimentpetrological study of Upper Cretaceous platform carbonates in the Llogara pass (Vlora, Albania)

Thesis

Full-text available

Jan 2014

Gert Ghysels

The Llogara succession (Vlora, Albania) consists of Upper Cretaceous shallow-water carbonates. It is part of the Sazani or pre-Apulian zone, which is the easternmost expression of the Apulian platform onto the Albanian mainland. This succession is composed of the stacking of small-scale sequences that in turn form medium- and large-scale sequences. A stratigraphical, sedimentological, diagenetic and petrophysical study was performed on samples originating from six intervals, each representative for a particular type of small-scale sequence. Also samples from Maastrichtian slumped intervals at the top of the Llogara succession were studied. The identification of benthic foraminifera and other microfossils expanded the biostratigraphic dataset of the succession. A targeted strontium isotope analyse could not identify suitable components for the dating of the deposits. Mainly rudist fragments were targeted but these are affected by alteration and do not reflect the original marine strontium signature. A detailed microfacies analysis was performed and the results were compared with a lithofacies classification scheme based mainly on field observations. In general, the results of the microfacies analysis correspond well with the lithofacies definitions in the classification scheme. However, one lithofacies did not correspond with the microfacies observations, resulting in the definition of a new lithofacies. Two depositional models are proposed. The lower part of the succession is deposited in a shallow-subtidal to supratidal restricted lagoonal setting. A moderate deepening of the system is attested in the upper part of the succession by the increased importance of subtidal rudist-rich deposits. A restricted lagoonal setting behind rudist biostromes is proposed as depositional environment for this upper part of the succession. Early dolomitization evidences a slightly increased salinity due to evaporative conditions. Similar depositional environments are evidenced for time-equivalent deposits at the Italian side of the Apulian platform and at the Kruja platform. Early diagenetic dolomitization and dedolomitization is evidenced by small (100 µm) rhombohedral moldic pores scattered throughout the matrix. Early marine or meteoric diagenesis affected the micrite of lithofacies at the top of the small-scale sequences, completely cementing them. The Llogara succession is influenced by early meteoric alteration as evidenced by stable isotope analysis and supported by petrographic observations (including cathodoluminescence). An inverted J-trend is observed with depleted 13C related to soil formation processes and depleted 18O related to a meteoric influence. The covariance between 13C and 18O indicates alteration in the marine-meteoric mixing zone. Meteoric alteration is mainly related to exposure surfaces at the end of medium- or large-scale sequences. However, meteoric alteration related to sequence boundaries of small-scale sequences could not be excluded. Possibly cementation under burial conditions occurred, as indicated by uniform dull equant cement, but this is not supported by the stable isotope results. Bedding-parallel stylolites (BPS) indicate chemical compaction during burial. Possible also minor telogenetic alteration occurred. Similar diagenetic evolution is observed in the L'Escalier and La Route sections in time-equivalent deposits of the Kruja platform. Mercury injection porosimetry is conducted. In general, porosity is quite low, pore network connection is poor and small pores (<15 µm) are dominant. Lithofacies display a good predictability of porosity. A trend of decreasing porosity towards the top of the small-scale sequences is observed and is related to the early marine/meteoric cementation. Reservoir potential is low. This can be explained by a combination of sedimentological factors (mostly micrite-dominated lithofacies) and diagenetic factors (early marine and/or meteoric alteration). Cyclicity in the sedimentology is clearly present in the stacking of the lithofacies. This cyclicity is less clear in the diagenesis, but is present in the early dolomitization and cementation of the micritic matrix at the top of the small-scale sequences. The latter is the reason for the clear cyclicity in porosity with decreasing porosity towards the top of the small-scale sequences.

Origine, âge et processus physico-chimiques des circulations de fluides dans les fractures : exemple de socle sous couverture (Vienne) et de formations riches en argiles (Gard, Est)

Thesis

Full-text available

Jan 2001

Stephane Buschaert

L'étude des colmatages minéraux déposés dans les discontinuités lors des circulations de fluides, anciennes à récentes, est l'unique moyen de reconstituer les comportements paléo-hydrologique et -hydrogéochimique des milieux granitiques ou sédimentaires. Le couplage d'outils pétrographiques, minéralogiques, isotopiques et géochimiques a permis de déterminer la source et la nature des fluides, et les processus physico-chimiques à l'origine des colmatages. 3 contextes distincts ont été ciblés dans le cadre des recherches menées par l'ANDRA pour l'implantation d'un laboratoire souterrain (le granite de la Vienne, les siltites du Gard et les argilites de l'Est du bassin de Paris). Ce travail a montré que le traçage isotopique en C et O des minéraux de discontinuités, couplé aux études pétrographiques, minéralogiques, et thermiques obtenues sur les inclusions fluides, sur les matières organiques et sur les argiles, constitue un outil puissant pour reconstituer les conditions paléo-hydrogéologiques, quel que soit le contexte.

Strontium as a tool in facies analysis

Article

Full-text available

Mar 1974

Sedimentology, clay mineralogy and depositional environment of Purbeckian green marls (Swiss and French Jura)

Article

Full-text available

Jan 1987

Buschaert S. (2001) Origine, âge et processus physico-chimiques des circulations dans les fractures. Ex. de socle sous couverture (Vienne) et de formations riches en argiles (Gard, Est). Thèse de doctorat, Université de Nancy 1, publication FORPRO 2001/28Th et Andra n°214-6 dans la collection « Les Rapports », 260 p.

Thesis

Full-text available

Oct 2001

Stephane Buschaert

The study of minerals sealing the discontinuities and the cavities by past to recent fluid circulations is the only method to assess the paleo -hydrological and -hydrogeochemical behavior of both sedimentary or granitic systems. Petrographic, mineralogic, isotopic (C, 0, H) and geochemical (KlAr) tools provide the opportunity: i) to identify the source and the nature of sealing (carbonates and quartz) -forming waters and ii) to precise the physical and chemical mechanisms occurring during fluid circulations. This study is focused on 3 sites selected in the framework of a survey managedby Andra for the feasibility of an underground laboratory: • In the covered plutonites of Charroux Civray (Vienne), 3 major fluid circulations (Hercynian fluids, Mesozoic brines, diagenetic waters) have been identified. The carbonates deposited in discontinuities or pervasively inside the granitic rocks have been formed from an unique C source (013C ranging from -9 and -14 %0). C stock has been early introduced during retrograde metamorphism, and afterwards, remobilized by successive fluid inputs. This confers on the Ca-rich plutonic rocks an efficient self-sealing capacity during later fracturing and fluid flow. • In Cretaceous siltites and surrounding limestones and sandstones of Marcoule (Southeastern Basin), calcites from fracture formed during Eocene compression and/or Oligocene extension have been deposited under low temperature conditions (T<50-55°C). C and 0 sources of fracture calcites differ as a function of stratigraphical levels. Fracture sealing occurs: i) either in close system, by redistribution of the nearby host-rock cements, or ii) in open system with introduction of C and 0 from external sources. These late events have contributed to reduce the global permeability of the rocks trough the sealing of the fractures. • In the Eastern part of the Paris basin, circulations of meteoric fluids have occurred at a regional scale during Tertiary, both in the fractures, cavities and in the porosity of the Bathonian and Oxfordian limestone series surrounding the Callovian-Oxfordian argillites. Carbon isotopie values of deposited calcites indicate that fluid circulations occurred upwards along the distensive regional faults. Fluids have also infiltrated Iimestones and sealed the porosity by crystallizing late sparite, resulting in the low present-day permeability values. However, these f1uids have not influenced the isotopie characteristics of argillites cements. The carbon isotopie composition must be exercised with caution to unravel the fluid origins in the event of poly-cyclic carbonate redistribution, as carbon of early minerais could be easily redistributed by the later fluid flows. Our methodology, based on the combined use of C-O isotopie tracers, petrographie, mineralogical and thermal (fluid inclusion, organic matter, clay typology) studies, is a promising powerful tool to assess the paleo-hydrogeologic behavior in geological systems. Keywords: Discontinuity sealing, Stable isotopes, Paleo-circulation, Fluid-rock interaction, Carbon remobilization, Vienne plutonites, Mesozoic series, Eastern Paris basin, South Eastern basin.

Caractérisation et interprétation de cycles géochimiques sur la plate-forme bourguignonne (France) au Bajocien-Bathonien

Article

Full-text available

Nov 1997

A sedimentological and facies sequence study, coupled with geochemical analyses (Sr, Mg, Fe, Mn and δ18O) was made on a core (Ravières, Yonne; south-east Paris Basin, France) in the Bajocian-Bathonian carbonate-shelf sedimentary succession. By studying the strontium variations, geochemical cycles can be correlated to transgressive-regressive sedimentary cycles. However, the interpretation of the geochemical cycles must refer to a different standard than the studies generally realised in basin environments.

Chemical diagenesis of a multicomponent carbonate system - 1. Trace elements.

Article

Full-text available

Jan 1980

Theoretical considerations of elemental behaviour during diagenetic stabilization with meteoric waters suggests that it leads to a decrease in Sr, Na, and possibly Mg and an increase in Mn, Fe, and Zn in progressively altered carbonates. Such elemental behaviour is exhibited by the different carbonate components of the Mississippian Burlington Limestone of Iowa and Missouri and the Silurian Read Bay Formation of Arctic Canada. Application of this trace element model suggests that Paleozoic crinoids were composed originally of metastable high Mga calcite, rugose corals were composed originally of stable low-Mg calcite or high-Mg calcite with low Mg 2+ content, and micrite was originally aragonite lime mud. -from Authors

Coral-microbialite reefs in pure carbonate versus mixed carbonate-siliciclastic depositional environments: The example of the Pagny-sur-Meuse section (Upper Jurassic, northeastern France)

Article

Full-text available

Jan 2004

Middle to Upper Oxfordian reefs of a shallow marine carbonate platform located in northeastern France show important facies changes in conjunction with terrigeneous contents. The Pagny-sur-Meuse section shows coral-microbialite reefs that developed both in pure carbonate limestones and in mixed carbonate-siliciclastic deposits. Phototrophic coral associations dominated in pure carbonate environments, whereas a mixed phototrophic/heterotrophic coral fauna occurred in more siliciclastic settings. Microbialites occur in pure carbonate facies but are more abundant in mixed carbonate-siliciclastic settings. Reefs seem to have lived through periods favourable for intense coral growth that was contemporaneous with a first microbialitic layer and periods more favourable for large microbialitic development (second microbialitic layer). The first microbialitic crust probably developed within the reef body and thus appears to be controlled by autogenic factors. The second generation of microbialites tended to develop over the entire reef surface and was probably mainly controlled by allogenic factors. Variations in terrigeneous input and nutrient content, rather related to climatic conditions than to water depth and accumulation rate, were major factors controlling development of reefs and their taxonomic composition.

Depositional sequences in shallow carbonate-dominated sedimentary systems: Concepts for a high-resolution analysis

Article

Full-text available

Oct 1999
SEDIMENT GEOL

Oxfordian and Berriasian sections representing shallow-water, carbonate-dominated sedimentary systems have been studied in the Swiss and French Jura, in Spain, and in Normandy. They all display a hierarchical stacking of depositional sequences. Facies evolution and stacking pattern allow to define elementary, small-scale, medium-scale, and large-scale sequences. Some depositional sequences display well-marked sequence boundaries, others are limited by transgressive or maximum-flooding surfaces. The hierarchical organisation of such sequence-stratigraphic elements implies that sea-level fluctuations were an important factor in their formation, and that these fluctuations had different frequencies. The superposition of high-frequency sea-level changes on a long-term sea-level trend leads to repetition of diagnostic surfaces, defining sequence-boundary and maximum-flooding zones wherein the corresponding high-frequency surfaces are well developed. Chronostratigraphic tie points permit us to estimate the duration of large-scale sequences. This time control and the observed hierarchical stacking suggest that the high-frequency sea-level changes were controlled by climatic cycles in the Milankovitch frequency band. The variability of stacking pattern and facies evolution between sections illustrates the complexity of the studied environments. Furthermore, because of the minimal accommodation space available in these shallow-water settings, much of the geologic time is not recorded. Nevertheless, detailed analysis of the depositional sequences allows the interpretation of the evolution of the sedimentary system with a high time resolution. Thus, there is a potential to monitor sedimentological, ecological, and diagenetic processes on a time scale of 20 to 100 ka.

Palynology, ammonites and sequence stratigraphy fromtethyan middle oxfordianto lower kimmeridgian, S-E France comparison with the boreal realm

Article

Jan 2000

Roger Jan Du Chene

The results presented in this paper have to be considered as a contribution to an important project whose aim is the geological study and global sequence stratigraphie correlation (multidisciplinary approach) of the Middle Oxfordian to Tithonian of different French areas, from the Sub-Boreal sections of Boulonnais, Normandy, Charente, Quercy, to the Tethyan sections of the Vocontian Trough. The review includes shallow water as well as deep water sections. The concept of this project is similar to the SE France Berriasian study published by the same working group (JAN DU CHÊNE et al., 1993). A dinocyst stratigraphie distribution chart zone is proposed between the Middle Oxfordian Transversarium Zone and the basal Upper Kimmeridgian Acanthicum of the Mesogean deep water reference sections of Vergons and Châteauneuf-d'Oze (Vocontian Trough; SE France). The two sections studied are rich in ammonites and are there-fore easily correctable with other Vocontian Trough sections to propose a sequence stratigraphic break-up primarily based on bed geometry, lithofacies and stratonomic observation, complemented by palynological and geochemical data, such as Mn content. The 3rd order sequences are stratigraphically calibrated using biostratigraphic information based on ammonites and dinocysts. From Sequence Ox 5 to Kim 3, most of the 3rd order sequences proposed by HARDENBOL et al. (1998) are stratigraphically recognised correctly with the exception of Kim 2. Data given by different geological tools as well as from other areas (particularly from the north of the Aquitaine Basin) suggest a double sequence Kim 2. To avoid any confusion with the HARDENBOL et al. cycle chart, the sequences proposed in this paper are called Kim 2' and Kim 2" respectively at the base and at the top of the interval. Correlation with the Boreal and Sub-Boreal realms are also proposed. The correlation takes into account recent papers on ammonite distribution at the Oxfordian-Kimmeridgian boundary. The joint occurrence of both Amoeboceras bauhini(a boreal species common in the base of the Baylei Zone) and Taramelliceras hauffianum (a Mesogean species) in outcrops of South Germany strongly suggests that the base of the Baylei Zone (and consequently the Oxfordian-Kimmeridgian boundary) corresponds to the base occurrence of T. hauffianum in the uppermost part of the Hauffianum subzone in the Tethyan realm. Most of the important dinocyst species have been observed in fairly comparable stratigraphic position to those known in the Boreal and Sub-Boreal realms. Additional information will be given in the near future by integrated studies presently in progress along the Upper Jurassic margins of the Aquitaine Basin (Quercy and Charente) and in Normandy.

Evolution of Mn contents of Neogene carbonates along the Bahamas transect (ODP Leg 166). Relationship of geochemical data to sea-level change

Article

Jan 1999

Calculation of simultaneous isotopic and trace element variations during water-rock interaction with applications to carbonate diagenesis

Article

Jan 2002
GEOCHIM COSMOCHIM AC

Dosage de quelques éléments traces dans les eaux naturelles et les roches carbonatées. Application à l'étude géochimique de la coupe duKef (Tunisie)

Article

Jan 1990

G. Richebois

Les formations carbonatées du Kimméridgien et du Portlandien dans le Jura méridional. Stratigraphie, micropaléontologie, sédimentologie

Article

Jan 1984

Paul Bernier

Sédiments aragonitiques et leur genèse

Article

Jan 1982

J.P. Loreau

The North Sea Cycle: an overview of 2nd order transgressive?regressive facies cycles in Western Europe

Chapter

Jan 1998

Four 2nd-order transgressive/regressive (T/R) facies cycles, including about forty 3rd-order depositional sequences, have been identified within western European Basins. They are: T/R 7 (Bajocian-middle Bathonian), T/R 8 (Upper Bathonian-middle Oxfordian), T/R 9 (Upper Oxfordian-Lower Volgian) and T/R 10 (Ryazanian). These long-term cycles are surprisingly synchronous over widespread areas, even though extensional tectonics were particularly active at that time. Only two regressive pulses (lower-middle Callovian and lower Kimmeridgian) are locally reported as a direct consequence of synrift block tilting. The 3rd-order depositional sequences, which are the building blocks of these 2nd-order T/R cycles, have been calibrated and defined from the North Sea to the Tethyan margin. This allows precise correlation between different tectonic settings and depositional environments. Major erosional unconformities relate to critical events of North Sea rifting. However, they are recorded as major 3rd-order sequence boundaries on surrounding shelves, even far away from the North Sea, such as on the Tethyan margin in the French sub-Alps. Most of the forty defined 3rd-order sequences can be objectively correlated within the limits of the available biostratigraphy. They represent a very efficient tool to constrain the timing of the tectonic control, to quantify the tectonic subsidence and the sediment supply and to predict the development of stratigraphic features.

Les systèmes biosédimentaires urgoniens (Aptien-Albien) sur la marge nord-ibérique

Article

Jan 1984

A. Pascal

Carbonate geochemistry (Mn, ∂13C, ∂18O) of the late Tithonian - Berriasian pelagic limestones of the Vocontian Trough (SE France)

Article

Jan 1993

Shows that manganese content fluctuations agree well with third order relative sea-level changes. This can help to characterise the various systems tracts: low values of manganese contents are recorded in the low-stand systems tract; increasing values occur in the transgressive systems tract with the maxima content corresponding to the maximum flooding surface; decreasing values in the highstand systems tract. -from Authors

Sedimentary Environments: Processes, Facies, Stratigraphy

Article

Jan 1996

H G Reading

Discontinuity surfaces on a shallow-marine carbonate platform (Berriasian, Valanginian, France and Switzerland)

Article

Nov 1998

Heiko Hillgartner

Discontinuities in sedimentation are commonly expressed as surfaces in outcrop sections and are due to rapid and substantial environmental changes. On shallow-marine carbonate platforms most such surfaces represent hiatuses below biostratigraphic resolution, and detailed analysis is necessary to identify and evaluate the environmental change involved. Surfaces in nine sections of the Lower Cretaceous of the French and Swiss Jura platform are characterized on the basis of eight universally applicable criteria (geometry, lateral extent, morphology, biological activity, mineralization, facies contrast, diagenetic contrast, and biostratigraphy). Nine different surface types are distinguished by their common features and environment of formation. AH of them are related to environmental changes in the form of subaqueous erosion, subaerial exposure, subaqueous omission, or changes in texture and facies. The distribution of surface types in the studied sections shows that condensation and exposure-related surfaces tend to occur repetitively in certain intervals. Calibrated by biostratigraphy, these surface zones can be correlated across the platform from proximal to distal positions. In comparison with the global sequence-stratigraphic framework (Hardenbol et al. 1997) most exposure zones correlate with third-order sequence boundaries, condensation zones fall in between. In the studied sections, third-order eustatic sea-level drops appear to be represented rather by zones of small-scale discontinuities than by widespread and well-marked single sequence boundaries. This is explained by the superposition of high-frequency, low-amplitude sealevel fluctuations on a larger-scale sea-level trend under greenhouse conditions. The lateral extent of the surface zones varies through time and indicates important changes in platform morphology. Changes in local subsidence rate indicated by variable thicknesses of the deposits in comparison with second- and third-order sea-level trends suggest an evolution of the French Jura platform from a ramp-type morphology in the late Middle Berriasian to a flat-topped platform in the Late Berriasian. The Early Valanginian again is characterized by increased differential subsidence and well-marked platform morphology. This study demonstrates that: (1) small-scale and short-lived discontinuities can reflect large-scale variations of relative sea level; (2) on shallow platforms characterized by small topographic variations and lateral facies changes, third-order séquence-stratigraphie surfaces are not necessarily expressed by one widespread single surface, but by zones of surfaces indicating repeated environmental changes; surface zones can serve as an additional tool for correlation and interpretation of platform evolution; and (3) small-scale discontinuities form an integral part of the stratigraphic record and should receive the same attention as the sedimentary deposits they delimit.

Visite des carrières d'Euville et de Pagny sur Meuse

Article

Jan 1998

Bernard Lathuilière

Jurassic Coral Reefs of the Northeastern Paris Basin (Luxembourg and Lorraine)

Conference Paper

Jan 1991

Apport de la cathodoluminescence à la connaissance de la spéciation du manganèse dans les carbonates pélagiques

Article

Mar 2000

Mn contents analysis of pelagic carbonates from the Upper Jurassic of the Vocontian trough (Châteauneuf-d'Oze section, Hautes-Alpes) allowed the definition of six third-order eustatic sequences that agree with the chronostratigraphic chart [17]. Cathodoluminescence intensity enables a semi-quantitative approach of Mn trapped in the calcite lattice; thus, CL-results show that most of Mn is found in the pelagic limestones as Mn2+. The Mn content variations observed in the low stands (low Mn contents) and in the high-stand systems tract samples (high Mn contents) reflect the sea water Mn content variations, which appear to be linked to the hydrothermal activity, especially by the ocean ridge. In the Vocontian realm, third-order sequences of the Upper Jurassic seem to be controlled by tectono-eustatism.RésuméLes variations des teneurs en Mn des carbonates hémi-pélagiques du Jurassique supérieur vocontien (coupe de Châteauneuf-d'Oze, Hautes-Alpes) permettent de définir six séquences de 3e ordre, en accord avec la charte des cycles eustatiques [17]. La cathodoluminescence permet une évaluation semi-quantitative des concentrations en Mn2+ incorporé dans le réseau de la calcite. Cette forme représente la plus grande part du manganèse dosé par AAS après attaque acide. Les différences observées entre les cortèges de bas niveau (faibles teneurs) et les cortèges de haut niveau (fortes teneurs) reflètent donc les variations de concentration dans le milieu océanique. L'activité des dorsales, par l'intermédiaire de l'hydrothermalisme sous-marin, semble être le mécanisme responsable de telles fluctuations. De ce fait, les séquences de 3e ordre étudiées paraissent contrôlées par le tectono-eustatisme.

Diagenesis of fibrous magnesian calcite marine cement: Implications for the interpretation of 18O and 13C values of ancient equivalents

Article

Jul 1996
GEOCHIM COSMOCHIM AC

Fibrous, high Mg-calcite (HMC) marine cement from the Pliocene Hope Gate Formation, Jamaica occurs as 1–2 mm thick isopachous coatings on skeletal grains in local occurrences of Halimeda grainstone and is commonly syntaxially overgrown by clear, prismatic low Mg-calcite (LMC) interpreted as a mixing zone cement. The presence of inclusions at discrete levels in the fibrous marine cement produces internal growth banding wherein clear, inclusion-free zones alternate with cloudy, inclusion-rich zones. Clear zones have uniform Mg contents (13.7 ± 0.2 mol% MgCO3) and stable isotopic compositions (δ18O = 0.8 ± 0.1%; δ13C = 3.2 ± 0.1%) consistent with a marine origin. In contrast, inclusion-rich zones contain fine-scale intergrowths of LMC, dolomite, and HMC, and have carbon and oxygen isotopic compositions that define a linear mixing trend between compositions of inclusion-free HMC and prismatic LMC cement overgrowths. Petrographic observations indicate that the mixing trend defined by isotopic data from inclusion-rich zones is related to the addition of large volumes of secondary LMC as cement in primary pore space, as intergrowths among fibers of primary HMC marine cement, and/or as replacements of primary HMC crystallites.

Temporal and compositional diversity in seafloor hydrothermal fluids

Article

Jul 1995

K. L. von Damm

Within the last 4 years a number of discoveries have significantly improved our understanding of the processes occurring in seafloor hydrothermal systems, and their net effects on the chemical and physical properties of the fluids. Prior to the 1990's time series samplings of vent fluids suggested that they were characterized by great temporal stability in their chemistry [e.g., Campbell et al, 1988]. In the late 1980's, the discoveries of megaplumes in the water column over the Juan de Fuca Ridge provided evidence for the episodicity of hydrothermal processes [Baker et al, 1987]. We therefore had a basic contradiction in our observations - astounding temporal stability in the vent systems that had been sampled numerous times (primarily 21°N East Pacific Rise (EPR), Guaymas Basin, South Cleft on the Juan de Fuca Ridge) (Figure 1) versus the water column evidence for temporal variability. The observation of volcanic eruptions at three sites on the world ridge crest system has provided the resolution to this apparent contradiction, and provided new insights into the evolution of seafloor hydrothermal systems. Direct information on the third dimension of a hydrothermal system became available for the first time, with the successful drilling of an active hydrothermal site at Middle Valley by the Ocean Drilling Program (ODP). Evaluating the hydrothermal input to the ocean (i.e., the flux) has become more problematic, but progress in understanding the underlying processes responsible for controlling vent chemistry, and in defining the flux of chemicals from the ocean ridge flanks, are important steps to eventual resolution of the flux question.

Subtidal carbonate cycles: Implications for allocyclic vs. autocyclic controls

Article

Jan 1991
GEOLOGY

David A. Osleger

Thick successions of repetitive metre-scale subtidal carbonate cycles require that short-term sedimentation rates approximate long-term accumulation rates in order to maintain submergence below peritidal depths. Intrinsic processes such as storm and wave reworking and redistribution may act to inhibit aggradation into the zone of optimal carbonate production. The presence of subtidal vs. peritidal carbonate cycles may be a function of energy regime that in turn may relate to platform morphology. The ultimate control on stacked subtidal cycles appears to be eustasy acting in concert with intrinsic processes such as storm and wave reworking.

L’âge du complexe récifal des Côtes de Meuse entre Verdun et Commercy et la stratigraphie de l'Oxfordien dans l'est du Bassin de Paris

Article

Dec 1981
Geobios

The question of the age of «Hauts de Meuse coral rag is studied again using new faunas of brachiopods and ammonites collected above, below and inside the coral rag. Ammonites fauna of the well known «Calcaires de Creuë is revised. Results obtained agree closely.The «Hauts de Meuse coral rag grew up during Middle Oxfordian time; and extend part of the Plicatilis zone (Antecedens Subzone) and the whole Transversarium Zone up to the basis of the Bifurcatus Zone, for the first time identified in Lorraine. So it span a short depositional time, about 1 MY, with a high deposition rate, the thickness of the coral rag being more than 100 meters, reaching 150 meters in Saint-Mihiel area. Towards SE, on the other side of the Marne Gap, the sudden change into basinal facies go with a reducing of thickness and deposition rate.Upper Oxfordian deposits show a relative uniformity of facies and thickness. At the top of Middle Oxfordian limestones, the age of the discontinuity and the Sequanian renewal of deposition is basal Bifurcatus Zone. Erosional renewal and terrigeneous deposits are a wide spread event by the beginning of Upper Oxfordian.In the paleontological part, species upon which are based new ages and interpretations are only figured, except the species new or with new paleontological data, which are described. Type specimen of Perisphinctes mosensisBayle, from the «Calcaires de Creuë, is described and photographically figured for the first time.

Observations of the distribution of manganese over the East Pacific Rise

Article

Dec 1980
CHEM GEOL

Gary P. Klinkhammer

When seawater circulates through hot basalt at active spreading centers, the manganese concentration of the seawater increases by ∼ 106 times. Eventually, this hydrothermal water is discharged back into ambient seawater through vents and fissures on the sea floor. Mn vs. silica relationships in water samples collected from active vent fields on the Galapagos Rift are linear but have different slopes. These relationships demonstrate that the Mn in the hydrothermal end-member mixes conservatively with ambient seawater (at least below 10°C) but the physical and chemical processes responsible for the Mn concentration of the hydrothermal fluid must be variable. The Mn concentrations measured for the Galapagos system predict that hydrothermal emanations are major sources of Mn to the oceans but only if these data are not anomalously high. This paper presents profiles of Mn in bottom waters at four locations along the East Pacific Rise (EPR) which support the hypothesis that Mn emanations comparable to those from the Galapagos are occurring along the EPR. Bottom water at one station in the Guatemala Basin, some 1000 km from the EPR crest, also has anomalously high Mn concentrations suggesting that this hydrothermal Mn signal can be transported far from the source.

Continental, brackish and marine carbonates from the Lower Cretaceous of Kolone-Barbariga (Istria, Croatia): Stratigraphy, sedimentology and geochemistry

Article

Jul 1998
PALAEOGEOGR PALAEOCL

During the Early Cretaceous, wide areas of the Dinaric–Adriatic Carbonate Platform emerged for long periods. The Hauterivian–Barremian carbonates from Kolone–Barbariga show a few typical examples of lacustrine facies with dinosaur bones and brackish/palustrine facies. The sequence of the platform is made for the most part by subtidal and intertidal limestones. The bone levels are located in a large depression few meters deep in the uppermost Hauterivian marine limestones. The filling facies of this depression are made by oncolitic rudstones and algal boundstones, which represent marginal lacustrine facies, and by laminated limestones, thin stromatolitic levels and distal fringes of rudstones which represent relatively open lacustrine facies. The fossil content is characterized by rare charophyte stems, ostracods, gastropods and plant remains, while typical marine fauna is absent. At the Hauterivian–Barremian boundary a major emersion event has been observed, then a slow transgressive phase occurred. The transgressive facies are primarily made by mudstones with ostracods, charophytes and Spirillina (brackish and probably freshwater facies), wackestones with Ophtalmidiidae and rare dasyclad algae, storm layers with gastropods and miliolids and breccia-like dinoturbated beds. Wackstones, packstones and very rich in dasyclad grainstones outcrop at the top of the section, representing the maximum of the transgression. Trace elements content, carbon and oxygen stable isotope analyses have been performed to aid the palaeoenvironmental interpretation. In this geological setting, Barium seems to discriminate between brackish and freshwater facies. The isotopic values of the marine carbonates appear to depend on early diagenetic processes, meanwhile lacustrine facies seem to show a weak signal of the depositional environment.

Possible use of strontium in sedimentary carbonate rocks as a paleoenvironmental indicator

Article

Jan 1971
SEDIMENT GEOL

The differences in present-day Sr concentrations in pure limestones (average insoluble residue < 5%) of the Western Carpathians region are interpreted as being due mainly to their original mineralogy. It is proposed that Sr content in conjunction with other observations may be used to distinguish between physicochemical and organodetrital carbonate sediments.

Etude geochimique de la fraction carbonatee d'un facies de bordure de depot gypseux (exemple du gypse ludien du Bassin de Paris) (geochemical study of a carbonate-rich facies in the northern border-area of the Ludian gypsum in the Paris Basin)

Article

Jun 1975
SEDIMENT GEOL

Renard Maurice

The bore-hole of Mont-Pagnotte (Oise, France), located in the northern border-area of the Ludian gypsum in the Paris Basin, shows a facies richer in carbonate than those of the centre of the basin. It is possible to relate this facies to the typical formations of the centre of the basin. Samples from the Middle Bartonian (Calcaire de Saint-Ouen) to the Stampian (argile verte) are studied. In this part of the core, the proportion of argillaceous minerals is very low, but there are many variations which are related to the evolution of the area of sedimentation. Alizarine-coloured thin-section study and X-ray analysis show that the microfacies is constant: it is always a calcimicrite. This constancy is very important in geochemical study, because we can eliminate a possible action of mineralogic and diagenetic factors on the distribution coefficient of the different elements studied. Results of the atomic absorption analysis of the trace elements (on the carbonate part of the samples) are positive for 8 elements (Sr, Na, K, Mg, Zn, Mn, Cr, Ni). After a critical discussion (based on much experimental data) of the comportment of those elements during carbonate sedimentation, the Sr, Na, K, Mg, Zn contents appear to represent an indicator of the salinity of the water in the area of sedimentation; the Mn concentration as an indicator of oxydo-reduction conditions in the sediment and the Ni and Cr contents as an indicator of variation in the quality of continental supplies (in ionic or detritic form). It is possible to relate this variation to weathering conditions on the continent.

Signification du signal isotopique ( δ 18O, δ 13C) des carbonates néritiques : composante diagénétique et composante originelle (Jurassique supérieur de l'Est du bassin de Paris, France)

Article

Jan 2004
CR GEOSCI

Along a reference section of the Upper Jurassic carbonate formations of Lorraine (HTM102 borehole, northeastern France), isotopic analyses (δ18O, δ13C) are performed on the carbonated phase of bulk rock. The study of these geochemical signals within carbonate platform setting is realized through a confrontation between bulk isotopic data and different sets of parameters (sedimentological data, isotopic data from microdrilled specific phases, petrophysical data). It appears that the use of the δ18O record as a chemostratigraphic descriptor is impossible, since this signal is a lithologic counterpart, only reflecting facies and diagenesis. On the other hand, the δ13C curve proves to be a promising tool in proximal realm. To cite this article: B. Vincent et al., C. R. Geoscience 336 (2004).

Best practices in sequence stratigraphy for explorationists and reservoir engineers

Article

Jan 1999

Sr/Mg variation during rock-water interaction: Implications for secular changes in the elemental chemistry of ancient seawater

Article

Mar 2001
GEOCHIM COSMOCHIM AC

Prior studies have recently demonstrated a positive linear covariance in the Sr and Mg contents of abiotic marine carbonates such that the slope of this relation is dependent upon the Sr/Mg ratio of seawater at the time of precipitation. Samples of ancient abiotic marine calcite cements that have undergone diagenesis through alteration by meteoric waters exhibit similar linear trends that range from primary marine ratios to low values that converge to zero. Thus, Sr/Mg ratios in diagenetic precipitates are potential proxies for the reconstruction of past variations in the elemental chemistry of ancient seawater.

Calculation of simultaneous isotope and trace element variations during water–rock interaction with applications to carbonate diagenesis

Article

Nov 1990
GEOCHIM COSMOCHIM AC

Equations are developed for the calculation of the simultaneous variations in trace element concentrations and radiogenic and stable isotopic compositions that occur during water-rock interaction. The equations are of general use for modeling chemical and isotopic variations in porous media and are applied here to the diagenesis of carbonate rocks and sediments. The variables which control the ultimate geochemical composition of diagenetic carbonates include the composition of the original sediment and fluid, water:rock ratio, fractionation factors, distribution coefficients, open vs. closed system behavior, and porosity.

The evidence of Polar ice during the Mesozoic

Article

Nov 1999
EARTH-SCI REV

Gregory D. Price

The Mesozoic, perhaps representing the longest period of warmth during Phanerozoic Earth history, contains in general sparse and frequently equivocal evidence for polar ice. Although this time is undoubtedly punctuated by oscillations in climate, whether sufficient to lead to polar cooling and the formation of polar ice (an inviting mechanism to account for faunal and floral distribution patterns and large scale sea level change), has been widely debated. Mesozoic evidence for glacial conditions includes abraded rock surfaces, generally unsorted stone-rich beds and the presence of dropstones rafted by ice within a finer-grained host sediment. Faunal and floral evidence has also been utilised to determine the presence or absence of cold or sub-freezing polar conditions, together with more indirect evidence for glacial conditions derived from General Circulation Model (GCM) simulations of climate, the analysis of clay mineral distributions, glendonite abundance, and palaeontological and sedimentological evidence for globally synchronous sea level change. The extent of possible glacial environments during the Mesozoic has been established by plotting published reports of glacial sediments on palaeogeographic reconstructions. The general clustering of evidence at high palaeolatitudes suggests that the extent of polar ice during the Mesozoic is likely to have been approximately one third the size of the present day. Based on such evidence a number of episodes of cold or sub-freezing polar climates during the Bajocian–Bathonian, Tithonian/Volgian, Valanginian and Aptian are recognised. Evidence exists possibly also for a cold episode during the early Jurassic (?Pliensbachian) although poorly constrained owing to limited biostratigraphical control. The longevity of these events may be represented by a `cold snap' within a stage, although undoubtedly the possible `smearing' of ages may have had the effect of lengthening and hence promoting the importance of these proposed events. The climate regime of the Earth during these times may be hypothesised to be characterised by a relatively steep pole-to-equator temperature gradient where low-latitude regions are as warm or warmer than today. The evidence to support such reasoning includes sharp increases in the areal distribution of both glendonites and deposits with affinities to glacial tillites and dropstones for these times. Coincidental falls of sea level, arid events and an increased bipolarity of faunas at these times imparts further confidence that these events were of a magnitude to effect the Earth as a whole.

Sedimentology and geochemistry of carbonates from lacustrine sequences in the Madrid Basin, Central Spain

Article

Jun 1995
CHEM GEOL

Lacustrine and alluvial carbonate facies have been investigated in Middle Miocene successions of the western side of the Madrid Basin in order to evaluate paleoenvironments in which carbonates formed. Carbonate facies are varied and include: (1) calcrete and dolocrete; (2) pond deposits; (3) lake margin dolostone; (4) mudflat carbonate; and (5) open-lake carbonate facies. The dominant mineralogy of these is dolomite and/or low-Mg calcite. No high-Mg calcite or aragonite have been detected in any sample. δ18O- and δ13C-values range from −8.20 to −1.80% PDB and −10.25 to −0.70% PBD, respectively. More negative δ18O- and δ13C-values correspond to predominantly calcite calcretes and to carbonate deposited in ponds at the foot of arkosic alluvium. Higher δ18O-values are from both lacustrine carbonate and dolocrete. This latter lithofacies has strong geochemical similarities to dolostones deposited in a lake margin environment. Mudflat carbonate, deposited on shallow platforms subject to lake water oscillation, shows great heterogeneity in both stable isotope value and trace-element content. The mineralogy of these carbonates is dominated by calcite and the limestones contain molds of gypsum. Occurrence of calcitized dolomite textures in these facies suggests the influence of fresher water during expanding lacustrine cycles or further interaction with less saline groundwater. Trace-element contents are considered to be potential indicators of the different carbonate facies types, thus aiding the paleoenvironmental interpretation. However, discrimination among carbonate facies on the basis of trace-element contents appears to be dependent on the statistical method utilized for treatment of data. More information is needed to ascertain their use as paleoenvironmental indicators.

Manganese in Pelagic carbonates: Indication of major Tectonic events during the geodynamic evolution of a passive continental margin (the Jurassic European Margin of the Tethys-Ligurian Sea)

Article

Feb 2000
PALAEOGEOGR PALAEOCL

Mid-oceanic hydrothermal activity is the main source of manganese in the pelagic realm. Consequently, long-term fluctuations of manganese in bulk carbonates could represent the variations in the hydrothermal flow intensity through time depending on global tectonic activity. Within this scope, we analysed three Jurassic sedimentary series in the Southeastern Basin (France), thus providing valuable information for further palaeogeographic and geodynamic reconstructions of the European Tethyan passive margin. The long-term variations of the manganese curve can be correlated with second-order sea-level changes. The main transgressive phases (Early Toarcian, Late Aalenian to Bajocian and Late Bathonian to Callovian) are marked by a manganese content increase whereas the regressive phases (Late Pliensbachian, Late Toarcian to Middle Aalenian, Early Bathonian to Middle Bathonian, Oxfordian) are characterized by decreasing trends. Furthermore, some manganese positive anomalies can be superimposed on the global geochemical record of sea-level changes. These coincide with periods of increasing subsidence rate (Early Toarcian, Late Bajocian, Middle and Late Oxfordian) and also with phases of extension (Early Aalenian) of the European margin of the Ligurian Ocean. The major event is the very sharp increase of manganese content localised in the Athleta Zone (Late Callovian) and corresponds to the first occurrence of oceanic crust. Moreover, the manganese enrichments recorded in carbonates deposited before Callovian times, may have resulted from hydrothermal emanations during the first stages of rifting.

Upper Jurassic microsolenid biostromes of northern and central Europe: Facies and depositional environment

Article

May 1996
PALAEOGEOGR PALAEOCL

Enzo Insalaco

Microsolenid biostromes are a common and important reef type in many Upper Jurassic reefal sections. Comparative study of these biostromes in western Europe allows the characterisation of this distinct biostrome type in terms of its taxonomic composition, palaeoecology and sedimentary regime.The biostromes are characterised by a coral community of relatively low generic diversity, being dominated by the Microsolenidae family of corals. The coral skeletal biovolume is generally high and is overwhelmingly dominated by platy ecomorphotypes. Sedimentologically these biostromes developed in low energy marl and limestone regimes which were subject to low sedimentation rates and varying degrees of siliciclastic influx. In contrast to the coral fauna the associated fauna shows a high generic diversity, in particular a rich assemblage of echinoids and bivalves. In addition the coral plates provide an ideal habitat for a well developed and strongly polarised encrusting and boring fauna. Top surfaces show limited post-mortem encrustation by serpulids and cementing bivalves, and are also bored by lithophagan bivalves. The undersides of the plates show a highly developed and diverse cryptic fauna of serpulids, thecidean brachiopods, bryozoans, calcareous sponges and sclerosponges.It is concluded that the main control on the development of these biostromes was low light intensities, though low energy level and low background sedimentation rates were also important. It is suggested that relatively high nutrient levels may have also played a significant role. The conditions for microsolenid biostrome development prevail in relatively deep-water environments, and hence these are the first coral-dominated reefal structures to have developed in deeper water shallowing upward sequences.The corals in these biostromes have adapted to these conditions by developing a strongly platy growth form, but also reducing their growth rates substantially. The microsolenids are particularly adapted to these environments in two ways: (1) They secreted an extremely porous calcium carbonate skeleton, which in environments where calcification rates are slow, such as deep water environments, is a distinct advantage; (2) In response to the limited potential of phototrophy in these environments the microsolenids have developed a pennular septal structure which is suggested to be a means of improving heterotrophic feeding. Trophic analysis of the reef fauna reveals that the nutrient limitation model developed for present-day coral reefs cannot be applied to these biostromes. It is demonstrated that the Microsolena and the present-day agariciid, Leptoseris show a number of significant morphological and ecological similarities.

Recherche méthodologique pour la restitution de l'histoire bio-sédimentaire d'un Bassin / L. Humbert

Article

Louis Humbert

Incluye bibliografía

Subaerial exposure and deposition of shallowing upward sequences: evidence from stable isotopes of Purbeckian peritidal carbonates (basal Cretaceous), Swiss and French Jura Mountains

Article

Aug 1994

Michael M. Joachimski

Purbeckian (lowermost Cretaceous) peritidal carbonates are characterized by open marine, lagoonal, intertidal and lacustrine facies arranged in Milankovitch‐type shallowing upward sequences. Shallowing upward sequences typically consist of 2–6 individual beds. The sequences may be (i) complete, (ii) incomplete or (ii) pedogenetically overprinted, reflecting the duration of subaerial exposure and/or the extent of erosion and pedogenetic modification at the cycle tops. The stable isotopic composition of the peritidal micrites reveals homogenous δ ¹⁸ O values attributed to diagenetic stabilization in a meteoric, water‐buffered system. Carbon isotopes show three distinctly different carbon isotope patterns dependent on the completeness of the shallowing upward sequences. Complete shallowing upward sequences consist of 4–6 individual carbonate beds. The carbon isotope values show a facies‐dependent pattern: open marine carbonate muds record enriched δ ¹³ C values of +0·28‰ while lagoonal (−0·82‰), intertidal (−2·46‰) and lacustrine micrites (−2·96‰) are increasingly depleted. This distinct pattern is explained by carbonate mud deposition in environments of differing salinity and marine influence. Incomplete sequences (2–5 carbonate beds) are characterized by depleted δ ¹³ C values below subaerial exposure surfaces that become progressively enriched in ¹³ C with increasing depth. Pedogenetically overprinted sequences (1–3 carbonate beds) show strong ¹³ C depletion throughout the sequence with little variation in the carbon isotopic composition. The depleted values (−4·5‰) of the pedogenetically altered micrites suggest that modification during subaerial exposure was associated with equilibration with meteoric solutions enriched in isotopically light soil gas CO 2 . The duration of subaerial exposure is the most crucial factor determining the extent of pedogenetic alterations, the completeness of the shallowing upward sequences and the carbon isotope pattern. The recorded patterns clearly illustrate that micrites have a good potential for the preservation of their primary carbon isotopic composition if the duration of subaerial exposure is rather brief. Otherwise, the recorded carbon isotope patterns may support sequence stratigraphic analysis by providing a refinement of the time‐stratigraphic interpretation.

Géochimie des carbonates pélagiques: mise en évidence de la fluctuation de la composition des eaux océaniques depuis 140 Ma, essai de chimiostratigraphie

Renard

Milankovitch sea-level changes, cycles and reservoirs on carbonate platforms in greenhouse and ice-house worlds

Jan 1995
1

J F Read
C Kerans
L J Weber
J F Sarg
F M Wright
JF Read

Jurassic coral reefs of the North-eastern Paris Basin (Luxembourg and Lorraine) Excursion Guidebook of VI International Symposium on fossil Cnidaria

Jan 1991

J Lathuilì

J,Lathuilì ere B (1991) Jurassic coral reefs of the North-eastern Paris Basin (Luxembourg and Lorraine). Excursion Guidebook of VI International Symposium on fossil Cnidaria.

Isotope and trace element record of relative sea-level in Albian carbonates from Congo Atlantic margin

F Walgenwitz
Le Dluz
A Eichenseer

F, Le Dluz A, Eichenseer H (1992) Isotope and trace element record of relative sea-level in Albian carbonates from Congo Atlantic margin. In: Kharaka YK, Maest AS (eds) 7th Int Symp Water–Rock Interaction, Balkema, Rotterdam, pp 487–491

Collection les rapports

Jan 1997
783-789

Vincent B L Jp Loreau
Thierry

B (2001) Sé et gé de la diagen ese des carbonates. Application au Malm de la bordure est du Bassin de Paris. PhD Thesis ANDRA " Collection les rapports ", University of Burgundy, 308 p Vincent B, Emmanuel L, Loreau JP, Thierry J (1997) Caracté et interpré de cycles gé sur la plate-forme bourguignonne (France) au Bajocien-Bathonien. CR Acad Sci Paris 325:783–789

Multidisciplinary approach to sedimentary dynamics of Malm deposits on Paris Basin eastern edge: facies, geochemical and sequential analysis

Oct 2000
13-15

B L Loreau
Jp

B, Emmanuel L, Loreau JP (2000) Multidisciplinary approach to sedimentary dynamics of Malm deposits on Paris Basin eastern edge: facies, geochemical and sequential analysis. Proceedings of the 20th IAS Reg Meet, Dublin, Ireland, 13–15 September 2000, pp 148

SIMS investigation of carbonate diagenesis

Jan 2005

B Loreau
Jp

B, Loreau JP, Emmanuel L (2005) SIMS investigation of carbonate diagenesis (Upper Jurassic, Paris Basin, France).

Signification du signal isotopique (δ 18 O, δ 13 C) des carbonates né: composante diagéné et composante originelle

Jan 2004
29-39

Vincent B L Loreau
Jp

Vincent B, Emmanuel L, Loreau JP (2004) Signification du signal isotopique (δ 18 O, δ 13 C) des carbonates né: composante diagéné et composante originelle (Jurassique supé de l'Est du Bassin de Paris, France). CR Gé 336:29–39

Recherche mé pour la restitution de l'histoire bio-sé d'un bassin. L'ensemble carbonaté oxfordien de la partie orientale du Bassin de Paris Upper Jurassic microsolenid biostromes of north-ern and central Europe: facies and depositional environments

Jan 1971
169-194

Humbert

Humbert L (1971) Recherche mé pour la restitution de l'histoire bio-sé d'un bassin. L'ensemble carbonaté oxfordien de la partie orientale du Bassin de Paris. Ph.D. Thesis, Nancy University n @BULLET AO 5096, 364 p Insalaco E (1996) Upper Jurassic microsolenid biostromes of north-ern and central Europe: facies and depositional environments. Palaeogeogr Palaeoclimatol Palaeoecol 121:169–194

Jurassic coral reefs of the Northeastern Paris Basin (Luxembourg and Lorraine) Excursion Guidebook of VI International Symposium on fossil Cnidaria. Münster, 112 p Hillgärtner H (1998) Discontinuity surfaces on a shallow-marine carbonate platform

Jan 1991
1093-1108

J Geister
B Lathuilì Ere

Geister J,Lathuilì ere B (1991) Jurassic coral reefs of the Northeastern Paris Basin (Luxembourg and Lorraine). Excursion Guidebook of VI International Symposium on fossil Cnidaria. Münster, 112 p Hillgärtner H (1998) Discontinuity surfaces on a shallow-marine carbonate platform (Berriasian, Valanginian, France and Switzerland). J Sediment Res 68:1093–1108

Sedimentology and trace element geochemistry of shallow-marine carbonates: An approach to paleoenvironmental analysis along the Pagny-sur-Meuse Section (Upper Jurassic, France)

Abstract

No full-text available

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