Ulrich Heimhofer

Leibniz Universität Hannover · Institute of Geology

The Cenomanian-Turonian Oceanic Anoxic Event (OAE2; ~94.5 million years ago) represents an episode of global-scale marine anoxia and biotic turnover, which corresponds to one of the warmest time intervals in the Phanerozoic. Despite its global significance, information on continental ecosystem response to this greenhouse episode is lacking. Here we present a terrestrial palynological record combined with marine-derived temperature data (TEX86) across an expanded OAE2 section from the Southern Provençal Basin, France. Despite high TEX86-derived temperature estimates reaching up to 38 °C, the continental hinterland did support a diverse vegetation, adapted to persist under elevated temperatures. A transient phase of climatic instability and cooling during OAE2 known as Plenus Cold Event (PCE) is marked by the proliferation of open, savanna-type vegetation rich in angiosperms at the expanse of conifer-dominated forest ecosystems. A rise in early representatives of Normapolles-type pollen during the PCE marks the initial radiation of this important angiosperm group.

Correlation of shallow-marine carbonate deposits with their coeval pelagic counterparts is often hampered by the lack of open-marine stratigraphic marker fossils and by the restrictions of regional biostratigraphic schemes. These difficulties can partly be overcome by the use of coupled δ¹³C and ⁸⁷Sr/⁸⁶Sr chemostratigraphy based on pristine shell calcite and bulk rock material. Here, a new high-resolution chemostratigraphic framework covering Kimmeridgian strata is presented based on three stratigraphic sections located in the Subboreal Lower Saxony Basin (LSB) of Northern Germany. Combined with sedimentological data, the bulk rock δ¹³C signal is critically evaluated for both diagenetic alteration and local environmental effects. In general, the δ¹³C signatures are considered to predominantly record the global marine signal. Diagenetic and facies-related discrepancies are restricted to dolomitic supratidal back ramp and intertidal back ramp deposits, respectively. Strontium-isotope stratigraphic data, obtained from diagenetically screened low-Mg calcite shells, refine the existing ostracod biostratigraphic scheme in the Lower Saxony Basin (LSB) and contribute to the existing global strontium-isotope dataset of the Kimmeridgian. These new results confirm the potential of well-preserved low-Mg calcite from shallow-marine settings to preserve a global marine Sr-isotope signal. Calibrated by the integrated biostratigraphic and strontium-isotope results, a high-resolution composite δ¹³C record for Kimmeridgian shoal-water deposits is established. Comparison of the new composite δ¹³C curve from the Subboreal Lower Saxony Basin (LSB) with existing Kimmeridgian records from the peri-Tethyan and Western Tethyan realms provides new insights into the long-term global carbon cycle during the Kimmeridgian.

The Jurassic–Cretaceous boundary interval in northwest Europe is characterised by a distinctive climatic change from pronounced aridity toward more humid conditions. In order to better understand the timing and evolution of the environmental dynamics related to this climatic change, terrestrial and aquatic palynomorphs (spores, pollen, dinoflagellate cysts, freshwater algae) have been studied from two recently drilled cores. The cores, which are both located in the Lower Saxony Basin (northern Germany), provide two 139 m and 134 m thick non-marine successions embedded in a high-resolution biostratigraphic framework. The lower part of the cores can be attributed to the Münder Formation (upper Tithonian–middle Berriasian), the upper part to the Bückeberg Group (middle–upper Berriasian). For reconstructing the arid to humid climate transition 110 samples have been analysed for their palynological content. In the Lower Saxony Basin, the late Jurassic–earliest Berriasian vegetation was dominated by cheirolepidiacean conifer forests growing under arid conditions along a coastal belt. A marked decline in cheirolepidiacean pollen and the spread of pioneering plants records an increase in seasonal humidity in the early–mid Berriasian. In the mid–late Berriasian the presence of highly diverse floras reflects even more humid and warm conditions. Fluvio-deltaic mixed swamp forests, which grew landwards behind the coastal belt were composed of conifers, ferns, lycopods, horsetails, bryophytes, ginkgos, cycads and Bennettitales. Cheirolepidiaceans, probably forming part of mangrove-type plant communities, remained an important component of the coastal flora. The climatic shift correlates to the upper Subcraspedites lamplughi–middle Heteroceras kochi ammonite zones of the marine Boreal zonation scheme and is synchronous to the early–mid Berriasian shift from arid to humid recorded from southern England.

Lower Cretaceous lacustrine oil shales are widely distributed in southeastern Mongolia. Due to the high organic carbon content of oil shale, many geochemical studies and petroleum exploration have been conducted. Although most of the oil shales are considered to be Early Cretaceous in age, a recent study reveals that some were deposited in the Middle Jurassic. The present study aims at establishing depositional ages and characteristics of the Jurassic and Cretaceous lacustrine deposits in Mongolia. The Lower Cretaceous Shinekhudag Formation is about 250 m thick and composed of alternating beds of shale and dolomite. The Middle Jurassic Eedemt Formation is about 150 m thick and composed of alternating beds of shale, dolomitic marl, and siltstone. The alternations of shale and dolomite in both formations were formed by lake level changes, reflecting precipitation changes. Shales were deposited in the center of a deep lake during highstand, while dolomites were formed by primary precipitation during lowstand. Based on the radiometric age dating, the Shinekhudag Formation was deposited between 123.8 ±2.0 Ma and 118.5 ±0.9 Ma of the early Aptian. The Eedemt Formation was deposited at around 165–158 Ma of Callovian–Oxfordian. The calculated sedimentation rate of the Shinekhudag Formation is between 4.7 ±2.6 cm/ky and 10.0 ±7.6 cm/ky. Shales in the Shinekhudag Formation show micrometer-scale lamination, consisting of algal organic matter and detrital clay mineral couplets. Given the average thickness of micro-laminae and calculated sedimentation rate, the micro-lamination is most likely of varve origin. Both Middle–Upper Jurassic and Lower Cretaceous lacustrine oil shales were deposited in intracontinental basins in the paleo-Asian continent. Tectonic processes and basin evolution basically controlled the deposition of these oil shales. In addition, enhanced precipitation under humid climate during the early Aptian and the Callovian–Oxfordian was another key factor inducing the widespread oil shale deposition in Mongolia.

Shallow-marine Kimmeridgian (Late Jurassic) deposits in the Lower Saxony Basin (LSB) composed of alternating limestone, marl and claystone attract great palaeontological interest due to their rich invertebrate and vertebrate assemblages. Unfortunately, the absence of open-marine marker fossils and numerous sedimentary gaps in combination with lateral facies changes hamper the precise stratigraphic correlation of these strata on both a local and global scale. Here, an integrated approach combining carbonate microfacies analysis, ostracod biostratigraphy and high-resolution sequence stratigraphy is applied to two Kimmeridgian sections (Langenberg and Bisperode, 60 km apart) in the southeastern LSB. High-resolution carbonate microfacies analysis enables the definition of 19 microfacies types and seven microfacies associations, which can be arranged into facies belts along a carbonate ramp. Vertical microfacies, bed thickness and diagnostic surfaces define stacking patterns that are interpreted as small-, medium- and large-scale sequences. The ostracod biostratigraphic framework established in this study provides the required stratigraphic control. Correlation of the two studied sections reveals a more proximal setting for Bisperode than Langenberg and an overall shallowing-up trend from mid-ramp to proximal inner ramp developed in both sections. Furthermore, the majority of the medium-scale sequence boundaries defined in this study can be found in similar biostratigraphic positions in other European basins. Synsedimentary tectonics combined with high sediment accumulation rates can be identified as important controlling factors for the distribution and composition of the Kimmeridgian deposits in the LSB based on detailed correlation on both a regional and super-regional scale.

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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.

The non-marine Purbeck- and Wealden-type sediments of latest Jurassic (Tithonian) and earliest Cretaceous (Berriasian) age in northern Germany were deposited in a restricted intercontinental basin. They mark an interval of strong faunal and floral provincialism which makes correlation of the non-marine strata across northwest Europe difficult. The position of the Jurassic–Cretaceous boundary has therefore been debated for decades. Our integrated stratigraphy of four sections in northern Germany, based on palynology (spores, pollen, dinoflagellate cysts) and ostracods, provides new evidence for a precise correlation with contemporaneous strata of other non-marine basins in northwest Europe. Correlation with the marine Boreal Realm and the Tethys is achieved via the Purbeck type section in England. A stratigraphic subdivision of the non-marine Berriasian succession in Germany is possible by using seven short-lived marine flooding events, which are documented by ceratioid dinoflagellate cysts and foraminifera. Our data suggest that a first major transgression took place close to the base of the Boreal Surites stenomphalus ammonite Zone. This level corresponds to a contemporaneous flooding event in southern England (Scallop Beds, Purbeck Group) and in southern Sweden (Annero Formation), thereby providing an excellent marker horizon for interbasinal correlation.

Stratigraphic uncertainties due to the lack of open marine marker fossils (e.g. ammonites) hamper the precise age assignment and stratigraphic correlation of Kimmeridgian strata found in the Lower Saxony Basin of Northern Germany. Correlation of these deposits with the Jurassic standard ammonite zonation is still difficult, since the existing ostracod biostratigraphy is facies-controlled and of only limited stratigraphic precision. In this study, a chemostratigraphic approach has been chosen and biogenic shell material produced by brachiopods, oysters and lithiotids is evaluated for its reliability to act as proxy of the original Jurassic seawater strontium isotope composition. Low-Mg calcite shells have been collected from three stratigraphic sections accessible in open-cast quarries located in the Lower Saxony Basin of Northern Germany. In order to identify diagenetically altered shell calcite, trace element and stable isotope analysis of 227 calcite samples (oysters=101; brachiopods=60; Trichites=52) has been carried out. The geochemical results reveal that (1) concentration of different trace elements varies between the different groups of shell-forming organisms, which may be related to vital effects and (2) high strontium contents , low Mn and Fe contents and the lack of correlation between these elements indicate near-pristine calcite shells, and therefore shells are supposed to record the ambient sea water composition during the Late Jurassic. Strontium-isotope (87 Sr/ 86 Sr) analysis of diagenetically screened samples indicates an Early Kimmeridgian age of the studied deposits, which is in accordance with ostracod biostratigraphic data. An increasing trend in 87 Sr/ 86 Sr with stratigraphic height fits well with the global strontium-isotope curve. Besides, similar 87 Sr/ 86 Sr ratios derived from different organisms from a single stratigraphic level highlight the suitability of the shells for strontium-isotope stratigraphy. Despite the shallow-marine character of the studied deposits, no evidence for significant riverine influence on the strontium-isotope signature is observed. The new chemostratigraphic data will provide a more precise age assignment for Kimmeridgian strata in the Lower Saxony Basin and thus enable the establishment of a solid integrated stratigraphic scheme that can be used for correlation on both regional and global scale.

Fine-grained sedimentary rocks predominantly composed of silts and clays (mudstones) are currently a popular topic within industry and academia. Of particular interest is to better constrain the pervasive facies variability present within these rocks. Despite their apparent homogeneity at core and outcrop scale, mudstones can actually be highly heterogeneous when examined in detail. We used geochemical and palynofacies analyses to delineate the facies variability present within the mudstone- dominated Lower Cretaceous succession in the eastern Lower Saxony Basin (LSB). In addition, the data-set is used to establish a sequence stratigraphic framework based on X-ray fluorescence (XRF) chemostratigraphy and palynofacies within apparently homogeneous mudstone successions. Our study is based on three scientific drill cores (Scharnhorst 3, Scharrel 10 and Frielingen 9) which were drilled during 2012–2014. Because of their close geographical location and similar palaeoenvironmental setting, these cored sections can be considered as one com- plete, 510-m-thick composite section covering the late Berriasian to earliest Aptian interval. All cores have been analysed for major and minor elements (Al, Si, S, K, Ca, Ti, Mn, Fe) by X-ray fluorescence (XRF) core scanning analysis at 1 cm resolution. The resulting trends for each element were analysed in terms of facies variability and to capture relative shifts in shoreline trajectories. For example, elemental ratios indicative of coarser clastic input (e.g., Si/Al) are used to decipher proximal to distal trends within the studied sediments. In order to better un- derstand the nature of geochemical variations, XRF core scanning analyses are compared with palynofacies results.

The study of past greenhouse climate intervals in Earth history, such as the Mesozoic, is an important, relevant and dynamic area of research for many sedimentary geologists, geochemists, palaeontologists and climate modellers. The Mesozoic sedimentary record provides key insights into the mechanics of how the Earth system works under warmer conditions, providing examples of natural climate change and perturbations to ocean chemistry, including anoxia, that are of societal relevance for understanding and contextualizing ongoing and future environmental problems. Furthermore, the deposition of widespread organic-carbon-rich sediments (‘black shales’) during the Mesozoic means that this is an era of considerable economic interest. In July 2015, an international group of geoscientists attended a workshop in Ascona, Switzerland, to discuss all aspects of the Mesozoic world and to celebrate the four-decade-long contributions to our understanding of this fascinating era in Earth history made by Hugh Jenkyns (University of Oxford) and Helmut Weissert (ETH Zurich). This volume of Sedimentology arose from that meeting and contains papers inspired by (and co-authored by!) Hugh and Helmi. Here a brief introduction to the volume is provided that reviews aspects of Hugh and Helmi's major achievements; contextualizes the papers of the Thematic Issue; and discusses some of the outstanding questions and areas for future research. This article is protected by copyright. All rights reserved.

The mid-Cretaceous is characterised by significant evolutionary changes in terrestrial ecosystems. During this period, the typical vegetation consisting of ferns, conifers and other gymnosperms was replaced by an angiosperm-dominated flora. Long ranging and continuous records from the continental realm are mostly lacking due to the prevalence of sedimentary gaps. Here a comprehensive palynological and clay mineralogical dataset covering early Albian to early Cenomanian strata from the shallow marine São Julião section (Lusitanian Basin, Portugal) is analysed to reconstruct the vegetation composition as well as climate and weathering conditions in the continental realm. The palynological assemblage is dominated by non-saccate Classopollis and Inaperturopollenites gymnosperm pollen with low abundances of spores and angiosperm pollen. The clay mineralogical data is mainly composed of kaolinite and mica and shows two conspicuous intervals of high kaolinite abundances in the late Albian. Based on the ecological preferences of the associated parent plants of the spore-pollen assemblage, a gradual relative temperature increase is inferred in the hinterland of the Lusitanian Basin during the early Albian to early Cenomanian interval. The clay mineralogy and palynological record show that the climate in the continental hinterland of the Lusitanian Basin was semi-arid to sub-humid and punctuated by two distinct humid phases during the late Albian. Multivariate statistical analyses and a comparison with the nearby Guincho section demonstrate the significance and reproducibility of the spore-pollen record. Furthermore, the palynological assemblage implies that angiosperms and ferns occupied similar palaeo-ecological habitats, namely as understorey in Cheirolepidaceae, Araucariaceae and Cupressaceae conifer-dominated forests.

A Neo-Tethyan upper Cenomanian – Santonian neritic carbonate ramp succession (Sarvak and Ilam formations), drilled in the Zagros Basin in southwest Iran, was investigated via detailed sedimentology, microfacies analysis, elemental geochemistry and Sr-isotope stratigraphy (SIS). The succession contains two exposure surfaces, which are known as the CT-ES and mT-ES (Cenomanian – Turonian and middle Turonian, respectively) and associated prominent negative carbon-isotope excursions, which represent important regional stratigraphic marker horizons. Precise knowledge about the onset of platform exposure and the duration of the exposure-related hiatus, however, is currently lacking due to a rather low-resolved shallow-water biostratigraphic framework and a bulk carbonate carbon-isotope pattern that clearly differs from global Late Cretaceous reference curves. Therefore, the existing bio-chemostratigraphic framework was complemented by bulk carbonate strontium-isotope stratigraphy (SIS). As bulk carbonate material is in particular prone to diagenetic alteration, a careful selection of least altered samples has been carried out by means of elemental geochemistry and petrography. In contrast to what could be expected, the meteoric alteration of limestones beneath both exposure surfaces are not clearly expressed by increasing iron and manganese and coeval decreasing strontium contents. In contrast, the impact of meteoric diagenesis is well illustrated via pronounced increases in Rb concentrations and concomitant prominent positive shifts to radiogenic strontium-isotope values, an observation that clearly reflects the decay of continentally derived ⁸⁷Rb into ⁸⁷Sr. Rubidium corrected strontium-isotope values place the CT-ES around the Cenomanian – Turonian boundary and point to an exposure duration of less than 0.4 Myr. This rather short-term CT-ES related hiatus is supported by petrographic evidence, which indicates a youth karstification stage of strata beneath the CT-ES. Following SIS, the Ilam – Sarvak transition at the top of Nezzazatinella-Dicyclina interval zone coincides with the mT-ES. Carbonates placing above this transition (Ilam Formation) are ascribed to the earliest to latest early Santonian, while carbonates immediately beneath the mT-ES (Sarvak Formation) are dated as late Turonian. SIS thus indicates a long-lasting hiatus of 4.5 Myr associated with the mT-ES. Emergence represented by the CT-ES is here proposed as harbinger of the mT-ES in the Zagros Basin, which most likely resulted from stepwise peripheral bulging due to ophiolite obduction in combination with a small-scale global sea level fall around 94 Ma.

Carbonate concretions hosted within organic carbon-rich shale sequences represent unique archives of often exceptionally preserved fossil biota. Besides providing high-fidelity preservation, their geochemical signatures can provide insight into the physical and chemical processes during early and later-stage concretion growth. Here, two fossiliferous carbonate concretions of the late Early Cretaceous Santana Formation (Araripe Basin, north-east Brazil) are analysed with an integrative geochemical approach including μ-XRF scanning, δ13C, δ18O, 87Sr/86Sr and Δ47 (clumped-isotope thermometry). Individual concretions show a concentric internal zonation with the outermost layer being composed of millimetre-thick cone-in-cone calcite. A strong covariance of δ13C and δ18O values of the fine-crystalline concretion body indicates mixing of two different carbonate phases and supports a scenario of temporally separated pervasive growth stages. Microbially-mediated formation of an early porous calcite framework was controlled by the combined processes of fermentation and methanogenesis around the decaying carcass, forming localized environments within a zone of sulphate reduction. Microbial sulphate reduction is indicated by the concentric enrichment of pyrite in the outer part of the concretion body and by high pyrite abundance in the surrounding shale. Information on the later-stage diagenetic processes affecting the Santana concretions can be derived from the outermost fringing cone-in-cone calcite. The carbonate precipitating fluid was characterized by a more or less marine δ18O composition (calculated δ18Oporewater = -1.0 to -1.8‰) and by radiogenic Sr-isotope ratios (up to 0.713331 ± 7.0*10-6), the latter probably reflecting modification due to interaction with the surrounding shale or, alternatively, with underlying evaporitic sulphate deposits influenced by strong continental inflow or with crystalline basement rocks. The Δ47-derived temperature estimates range between 37 to 42°C ± 5, indicating precipitation of the cone-in-cone calcite at a depth of 650 to 850 m, which is only half as much as the maximum burial depth derived from existing fission-track data. Overall, the study of fossiliferous carbonate concretions in organic carbon-rich sedimentary sequences can reveal a complex growth history spanning incipient microbially-influenced precipitates as well as later-stage burial diagenetic phases. This article is protected by copyright. All rights reserved.

During the Kimmeridgian, sedimentation in the Lower Saxony Basin was characterized by shallow-water deposits composed of alternating limestones, marls and claystones. Stratigraphic uncertainties caused by the absence of open marine marker fossils and prevalence of sedimentary gaps hamper a precise age assignment and correlation of these successions on a regional and global scale. Here, we provide new sedimentological and chemostratigraphic data for two sections (Langenberg and Bisperode sections), with particular focus on microfacies and stratigraphic architecture analysis coupled with high-resolution carbon-isotope stratigraphy. A total of 14 carbonate microfacies types (MF-types) are assigned covering mid-ramp to back-ramp settings. Based on the stratigraphic variation of MF-types and their stacking pattern, A/S cycles (accommodation space to sediment supply and/or sediment production) of different hierarchies (small-scale and mid-scale) are distinguished. Based on integration with information on facies proportion (which indicate facies changes in each cycles) and semiquantitative microfacies data, an overall change in depositional facies towards more proximal conditions can be observed from the base to the top in both sections. Carbon-isotope stratigraphy based on bulk carbonate is used for both intra- and interbasinal stratigraphic correlation. The chemostratigraphic correlation on regional scale reveals that (1) higher-amplitude as well as rather subtle trends in the carbon isotope record are preserved at both localities, (2) values in both curves gradually decrease with stratigraphic height and, (3) both the mid-scale cycles and the small-scale cycles correlate very well with the chemostratigraphic correlation framework. Furthermore, a first tentative carbon-isotope correlation between the Langenberg record and existing carbon-isotope records from European basins further highlights the potential of carbon-isotope stratigraphy for the correlation of Mesozoic shoal-water deposits. Additionally, strontium isotope data based on investigation of pristine low-Mg calcite shells (brachiopods and oysters) will be used to refine the stratigraphic age. Bulk geochemistry parameters including carbonateand total organic carbon (TOC) content, as well as clay mineral fraction will provide additional information and complement the sedimentological data.

Preceding the early Toarcian Oceanic Anoxic Event by ~1 Myr, the Pliensbachian – Toarcian boundary event is in many aspects as severe and disturbing for the environment as its better-studied successor. Both events are associated with rapid and pronounced global warming, major faunal and floral turnover, increased hydrological cycling and dramatic collapses of carbonate production. To better characterize the Pliensbachian – Toarcian boundary event, a high-resolution, paired carbonate and organic matter carbon isotope survey of three sections from the Central High Atlas Basin of Morocco has been undertaken. A pronounced negative shift in the carbonate carbon isotope record, not paralleled by a similar excursion in the organic carbon, can be linked to the collapse of the neritic carbonate factory in the earliest Toarcian. These results show that, contrary to the Toarcian Oceanic Anoxic Event, a rapid and massive injection of 13C-depleted carbon into the atmosphere is not responsible for the environmental perturbations observed during the Pliensbachian – Toarcian boundary event. However, input of isotopically non-depleted carbon such as mantle source CO2 into the atmosphere as a potential cause for the Pliensbachian – Toarcian boundary event cannot be excluded. This would most probably be sourced from an early pulse of the Karoo-Ferrar Large Igneous Province.

The evolution of angiosperms significantly changed the composition of the terrestrial vegetation during the mid-Cretaceous. In contrast to the wealth of information available on the biology and systematic relationships of early angiosperms, the temporal patterns of their evolution and radiation are poorly constrained. Here we present a continuous angiosperm pollen record from well-dated shallow marine deposits in the Lusitanian Basin, Portugal. The São Julião section provides a solid stratigraphic framework to track angiosperm pollen distribution patterns from the early Albian to early Cenomanian at mid-latitudes. In comparison to previous angiosperm pollen records from the Lusitanian basin, the section shows an extended late Albian succession and provides new insights into the diversification of early angiosperms during this important interval. Productive palynological samples were analysed and 79 different angiosperm pollen types have been recorded. Throughout the Albian angiosperm pollen represent only a minor component of the total palynoflora. The early Albian pollen record is characterized by highly diverse assemblages of monoaperturate pollen of monocot or "magnoliid" affinity and by the first appearance of polyporate and tricolpate pollen of eudicot affinity. A distinct diversification phase among tri- and poly-aperturate pollen (e.g., Cretacaeiporites, Retitrescolpites, Rousea, Striatopollis and Tricolpites) and the presence of conspicuous pollen grains assigned to Dichastopollenites characterize the middle and late Albian palynological assemblages. Thus, the section records a striking sequence of appearances of important angiosperm pollen morphologies. Monocolpates, polyporates and tricolpates appear in the early Albian whereas tricolporates appear from the early part of the late Albian onwards. Furthermore, well-constrained biostratigraphic ranges of selected angiosperm pollen from mid-latitudes are presented. In view of these new data, the temporal framework of the palynological Subzones II-B and II-C in the Potomac Group succession from the Atlantic Coastal Plain, eastern USA is revised to a middle to late Albian age.

Deep-time shallow-marine carbonate platforms record distinct biotic responses to climatic and environmental stressors. Unfortunately, precise temporal assignment of these biotic responses is often problematical due to poor biostratigraphic control and/or a significant diagenetic overprint of the neritic bulk carbonate chemostratigraphic inventory. An accurate stratigraphic framework is essential to better understand the causal relation between biotic events recorded by carbonate platforms and environmental changes that, for instance, culminated in mass extinction events or prolonged episodes of oceanic anoxia. Here we provide an integrated carbon and strontium-isotope stratigraphy of the Early Cretaceous subtropical Provence carbonate platform in SE France that is based solely on pristine low-Mg calcite from rudist bivalves. Carbon-isotope data of geochemically screened rudist fragments enabled reconstruction of a characteristic Barremian pattern including the Mid-Barremian Event (MBE) that allowed for a precise correlation with stratigraphically well-constrained Tethyan shallow-water and hemipelagic reference sections. In order to evaluate ontogenetic carbon-isotope changes and the overall variability of the shell-derived carbon-isotope data, numerous sclerochronological carbon-isotope profiles of individual large rudist shells are presented. Strontium-isotope stratigraphy supports the carbon-isotope based age of the studied sections, but also provides unequivocal evidence for a major hiatus in the depositional record covering large parts of the Late Barremian. In contrast to biostratigraphic and bulk carbonate chemostratigraphic archives, the here established chronostratigraphy of carbonate platform evolution in the southern Provence region demonstrates a twofold resurgence of udist-rich carbonate platform production during the Early Aptian and arguably the latest Early Aptian. PLEASE CONTACT FIRST AUTHOR AND REQUEST A PDF VERSION OF THIS ARTICLE!

Studies dealing with the response of the continental biosphere to the environmental perturbations associated with Cretaceous oceanic anoxic events (OAEs) are comparatively rare. Here, a quantitative spore-pollen record combined with clay mineral data is presented, which covers the entire early Aptian OAE 1a interval (Forcall Formation, Maestrat basin, east Spain). The well-expressed OAE 1a carbon-isotope anomaly is paralleled by changes in the clay mineral assemblage and by a stepwise decline in the normalized frequency of Classopollis pollen (produced by xerophytic Cheirolepidiaceae) with lowest contents occurring during the positive δ13C shift. In contrast, Araucariacites and Inaperturopollenites pollen show a pronounced increase in relative abundance from low background values to become a significant component of the palynological assemblage during the Classopollis minimum. The observed changes in clayminerals and pollen distribution patterns are interpreted to reflect amajor change in the composition of the hinterland vegetation of the Maestrat Basin, most probably due to short-lived but pronounced climatic cooling and changes in humidity. Temperature anomalies driven by organic carbon burial and associated CO2 decline have been postulated for all major Mesozoic OAEs. The palynomorph record from the Iberian Maestrat basins indicates that the climax of this cooling episode was significantly delayed in comparison to the end of organic carbon-rich deposition in the world oceans.

The Valanginian Weissert episode of environmental change is associated with a positive carbon–isotope excursion (CIE) in δ13Ccarb and δ13Corg records and a crisis in pelagic and neritic carbonate production. The CIE was interpreted to represent the first oceanic anoxic event (OAE) of the Cretaceous, linked with the formation of the Paraña–Etendeka large igneous province (LIP). Recent studies suggest though that the extent of oceanic anoxia was limited to high-latitude epicontinental seas and the Pacific, and that the Paraña–Etendeka LIP postdates the Valanginian CIE. With these new interpretations, the palaeoenvironmental changes behind the observed perturbation of the carbon cycle remain to be elucidated. Here we present sedimentological and geochemical results from a drill core near Wąwał, central Poland. The excavated succession is of particular interest due to its near-shore depositional setting within the former Polish Basin and its preservation (up to 17 wt.% of aragonite). The core consists of lower to upper Valanginian silty to sandy clays deposited under fully marine conditions on top of an Upper Jurassic karstified limestone. A change in weathering mode from very humid and highly hydrolysing towards less humid and seasonally contrasted conditions is indicated by the abrupt change from a kaolinite- to a smectite-dominated clay-mineral association near the boundary between the early and late Valanginian. Moreover, two phosphate-rich horizons were identified, which correlate in time to northern Tethyan occurrences in the Helvetic Alps. The lower level is associated with the early Valanginian transgression and corresponds to peak humidity recorded in the Wąwał core. The upper layer corresponds to the paroxysmal phase of the Valanginian crisis in carbonate production. In the Wąwał core, evidence for anoxic conditions during the Valanginian CIE is lacking. The climatic conditions and changes identified in the Polish Basin are different from those of the northern Tethyan area, where an increase in humidity is observed near the early–late Valanginian boundary. The contrasting climate conditions are probably an expression of latitudinal shifts in the position of the northern mid-latitude humid belt.

A new Albian –Turonian carbon isotope (δ13Ccarb and δ13Corg) curve based on epeiric-neritic carbonate successions from Peru is reported. The study was carried out to test the hypothesis that mid-Cretaceous OAEs, which are well-documented in the Tethys and Atlantic realm, are equally recorded in the epeiric-neritic realm of the eastern sub-equatorial Pacific as exposed in Northern and Central Peru. Depositional environments range from shallow subtidal inner ramp to outer ramp settings. For this purpose, we combined chemostratigraphic and sedimentological information from expanded and well-exposed sections in NW Peru. The geochemical data provide evidence for the record of the OAE1b set, the OAE1c, the OAE1d, as well as the Cenomanian – Turonian Boundary Event (OAE2), known as one of the most extreme carbon cycle perturbation. The new δ13C record is constrained by biostratigraphic evidence and 87Sr/86Sr isotope stratigraphy using well-preserved oyster shells. Sedimentological observations, combined with the δ13C stratigraphic record, were used to elucidate the complex interplay of climate changes, nutrient supply and platform drowning. These observations indicate: (1) A late Aptian–early Albian change from siliciclastic-to carbonate-dominated sedimentation that may be coeval with the placement of the Kilian event. (2) Incipient platform-drowning during the early Albian probably linked to the impact of the Paquier event. (3) An early middle Albian demise of neritic carbonate production that coincides with the Leenhardt Level, followed by middle Albian condensed sedimentation that reports prominent negative values in δ13Ccarb. (4) Renewed carbonate ramp production during the late Albian–middle Cenomanian. (5) An upper Cenomanian–middle Turonian transition interval with the OAE2 represented by a 44-m-thick sedimentary succession characterized by rhythmically bedded marls, marly limestones and limestones. Despite the scarcity of significant amount of organic matter (a.k.a, black shales) or indicators of oxygen deficiency, the δ13C curve matches well with published high-resolution curves for coeval successions in the Pacific elsewhere (Pacific Guyots; Hokkaido, Japan; Guerrero, Mexico), European Tethys (Vocontian Basin, France; Piobbico section, Italy; English Chalk; Wurstorf section, Germany) and Western Atlantic domain (Pueblo Colorado, USA; Sierra Madre, Mexico), supporting the global nature of the isotope patterns observed in Peru.

Integrated biostratigraphic-chemostratigraphic studies provide evidence that the proto-North Atlantic realm witnessed major changes in carbonate platform production in the run-up of the Early Aptian oceanic anoxic event (OAE) 1a. Whereas pervasive growth of Lithocodium microencrusters represents an early harbinger of OAE1a-related environmental perturbation, the subsequent replacement of oligotrophic rudist-coral-nerineid by mesotrophic orbitolinid-oyster communities was clearly associated with the event itself. In order to test the supra-regional relevance of this major community replacement, two shallow-water sections in the southern Lusitanian Basin (Portugal) are investigated by means of geochemistry (carbon and oxygen isotopes), cement petrography and detailed sedimentological analysis. The focus is on a regional, prominent discontinuity surface (S4) at the transition between oligotrophic and mesotrophic carbonate platform production, which might indicate that the major biotic change could have been associated with a phase of non-sedimentation and possibly erosion. The studied sections (São Julião, Crismina) provide evidence that the major Early Aptian biotic turnover was preceded by numerous subordinate but significant changes in platform ecology, which mirrored a series of progressive short-term environmental changes in the course of OAE1. Several transient mass occurrences of orbitolinids indicate repeated phases of ecological stress arguably due to enhanced nutrient input and deepening. Small-scale sea-level changes at parasequence level below the major discontinuity surface are revealed by alternations of rudist assemblages dominated by clinger or recumbent forms as well as intercalated hardground and subaerial exposure stages. Expanded phases of subaerial exposure, however, can be largely ruled out following the geochemical and cement-petrographic data presented here. Enhanced continent-derived siliciclastic input characterising the lower orbitolinid-oyster dominated limestones is in support of a shift to more humid conditions during the middle Early Aptian. This is in line with palaeoclimatic data, which propose a southward movement of the mid-latitude arid climate belt during this time. The documented rapid replacement of oligotrophic assemblages by various environmental-stress adapted carbonate platform communities might be seen as explanation for ongoing Early Aptian proto-North Atlantic carbonate production during a time of widespread platform demise and drowning in the northern Tethyan realm.

Stratigraphic age assignment of Cretaceous shoal-water deposits is notoriously difficult and often hampered by the lack of typical index fossils and the prevalence of sedimentary gaps. Here, we present new bio- and chemostratigraphic data for three sections located in the Lusitanian Basin, Portugal, composed of Albian strata. Sections are correlated and dated using dinoflagellate cyst biostratigraphy, strontium-isotope stratigraphy based on oyster and rudist shells and carbon-isotope stratigraphy. The measured Sr-isotope values from pristine shells are in line with global open marine 87Sr/86Sr values from the Albian. Correlation of the Portuguese C-isotope curve with hemipelagic Albian reference records and the presence of typical Albian dinoflagellate cysts further constrain the age of the different sections. The proximal-marine and thick (∼ 190 m) Sao Julião section serves hereby as reference curve. Correlation with the independently well-dated and more distal Guincho section in the Lusitanian Basin slightly revise the age of the Sao Julião and Magoito sections compared to previously published results. Furthermore, our findings demonstrate the time-transgressive nature of marine deposition in the southern Lusitanian Basin. The onset of marine conditions in the Água Doce Member and the deposition of rudist bearing carbonates of the Ponta da Galé Member are diachronous and started significantly earlier in the southernmost part of the basin compared to the north. In summary, the combined geochemical and biostratigraphic results provide an enhanced time control and slightly revise the age of the sections in comparison to previously published studies while providing lithological descriptions, Sr-isotope derived ages and carbon-isotope records. Furthermore, the carbon-isotope record of Sao Julião can be correlated with Italian (Umbria-Marche Basin) and French (Vocontian Trough) sections and highlights the applicability of shallow marine deposits as chemostratigraphic archives.

We collected a set of 120 clay samples with precise stratigraphic locations from the Lower Cretaceous coastal outcrops of the Ericeira area (western Portugal). The kaolinite versus illite dominance can be considered as revealing wet or dry climates, respectively, prevailing in the watershed. Swelling clays are associated with seasonally dry climates. However, since hydrodynamics and rejuvenation events also control clay associations, the relative role of climate versus depositional setting is still to be fully deciphered. As the onshore Lower Cretaceous of western Portugal is a key area for studying the Early Cretaceous initial diversification of angiosperms, several well-studied floras are summarized and their environmental interpretations presented.

Changes in terrestrial vegetation patterns during the Valanginian (Early Cretaceous) and their link to major climatic and environmental alterations are poorly studied. In this study, the spatial and temporal changes in plant community structure are reconstructed based on spore pollen records from two mid-latitude sites located in the Mid-Polish Trough (MPT, central Poland), and the Vocontian Basin (VB, southeast France). Stratigraphic control is provided by delta C-13(carb) chemostratigraphy and calcareous nannofossil biostratigraphy. Reconstruction of hinterland vegetation is based on palynological investigations of 83 samples from hemipelagic (VB) and marginal marine (MPT) sediments rich in terrestrial palynomorphs. A total of 45 palynomorph taxa were identified at generic level (30 spores, 15 pollen). Vegetation around the MPT was dominated by araucarian/cupressacean conifers while that surrounding the VB was dominated by drought-resistant cheirolepidiacean conifers. At both sites the understorey and/or vegetation of open areas was dominated by pteridophytes. An early Valanginian gradual trend towards humid conditions at the MPT, well expressed by a distinct increase in the spore pollen ratio, culminates in a short-lived spore-maximum stratigraphically located at the lower/upper Valanginian boundary. It is characterized by low conifer abundances and high abundances of the fern spore taxa Cyathidites, Leiotriletes and Gleicheniidites accompanied by enhanced abundances of the pteridosperm pollen Vitreisporites pallidus, whose parent plants are assumed to be indicative of swamp habitats. The spore-maximum is coeval to a similar peak observed in the VB, characterized by essentially the same taxa. Here, the spore-maximum is preceded by a protracted phase of arid conditions, characterized by low spore abundances and exceptionally high numbers of the cheirolepidiacean conifer pollen Classopollis. Changes in moisture, identified as the key climatic factor determining trends and turnovers in vegetation, were probably controlled by a monsoonal circulation. The supra-regional humid phase expressed by the coeval spore maxima was probably induced by an intensified monsoonal climate. The temporal influence of a northern hemisphere arid belt at the VB, under the influence of the subtropical high-pressure belt, may have caused the temporal drying not affecting the MPT site, located further north.

Cretaceous oceanic anoxic events (OAEs) have received considerable attention during the last couple of decades and a wealth of information has been obtained on the stratigraphy, paleoceanography and biogeochemistry of these episodes. Up to now, research focused mainly on the marine OAE record, whereas studies investigating the response of the continental biosphere to OAEs are comparatively rare. Here, a quantitative spore-pollen record is presented, which covers the entire Early Aptian OAE1a interval including its onset and aftermath. Sporomorph-bearing deposits from the Forcall Formation, Maestrat basin of E Spain, have been investigated using bulk rock geochemistry (TOC, CaCO3, carbon isotopes) as well as palynofacies analysis and palynology. The carbon-isotope trend shows a very distinct pattern and enables detailed correlation with established curves covering OAE1a. A total of 28 different genera of spores and pollen have been distinguished within the studied 38 samples. Whereas pteridophyte spores and conifer-derived bisaccate pollen show only minor variations with stratigraphic height, non-saccate gymnosperm pollen (notably Classopollis, Araucariacites, Inaperturopollenites) record a major shift during and in the aftermath of OAE1a. Classopollis pollen, produced by the xerophytic Cheirolepidiaceae, is the dominant pollen group before the event (80-90 %) and shows a distinct two-step decrease with lowest abundances (as low as 21 %) occurring within the positive carbon isotope anomaly (C7 segment in Bover-Arnal et al. 2011). This gradual decline is followed by a subsequent rise in Classopollis pollen reaching almost pre-OAE values of 60-80 %. In contrast, Araucariacites and Inaperturopollenites pollen show a distinct increase from low background values (less than 10 %) to become a significant component of the palynological assemblage during the Classopollis drop. The observed changes in pollen distribution patterns are interpreted to reflect a major change in the composition of the hinterland vegetation of the Maestrat basin, most probably due to short-lived but pronounced climatic cooling. Temperature anomalies driven by organic carbon burial and associated CO2 decline have been postulated for all major Mesozoic OAEs. The palynomorph record from eastern Iberia indicates that the climax of this cooling episode (represented by the Classopollis minimum) was significantly delayed in comparison to the end of organic carbon-rich deposition in the world oceans.

The Lusitanian Basin in Portugal is one of the most important areas to investigate the rise and radiation of early angiosperms. Here, important micro-, macro- and mesofossil remains including pollen, reproductive organs, fruits and seeds have been found. In this study, a high-resolution Early to Late Albian pollen record from a thick (~160m) coastal succession in the Lusitanian Basin containing mixed carbonate-siliciclastic near-shore deposits is generated. The outcrop is located near the town of Ericeira (São Julião) and exhibits some important new features compared to existing records from the Lusitanian basin. The comparatively proximal depositional setting and high sedimentation rate of the São Julião outcrop is well suited for high-resolution palynological sampling compared to previously studied, more distal outcrops. In addition, the succession covers almost the entire Albian including a thick interval representing Late Albian strata. Dating of the succession was obtained using dinoflagellate cyst biostratigraphy, bulk C-isotope analysis and strontium isotope analysis of low-Mg oysters and rudist shells. The high-resolution pollen record shows a distinct radiation pattern of early angiosperm pollen as well as significant changes in the accompanying palynoflora. During most of the section gymnosperm pollen types such as Classopollis spp., Inaperturopollenites spp. and Exesipollenites spp. are dominant. Angiosperm pollen abundances do not exceed 20%, although angiosperms increase slightly from the Early Albian onwards. Monoaperturate grains of magnoliid or monocot affinity remain the most dominant angiosperm pollen type, both in abundances and diversity. Tricolpate and zonoaperturate pollen grains are also present. In addition, the occurrence of several odd-shaped Dichastopollenites-type pollen types is intriguing. The palynological results indicate a warm and dry climate during most of the Albian, although a rise in the spores over pollen ratio in the second half of the section may suggest more humid conditions. In summary, the combined approach of Sr- and C-isotope stratigraphy together with marine biostratigraphy gives an accurate age assessment, which enables precise dating of the angiosperm pollen pattern emerging during the Albian.

Mid-Cretaceous shoal-water ecosystems have been proven to show characteristic response modes (microencruster blooms, carbonate platform drowning) to major climatic and environmental changes that finally culminated in so-called oceanic anoxic events (OAEs). During most OAEs, the widespread burial of unusual amounts of organic matter in pelagic basins caused a strong carbon-cycle perturbation, expressed as prominent positive carbon-isotope excursion. Stratigraphically, the Aptian OAE1a is marked by a well-defined carbon-isotope pattern (negative spike and subsequent positive anomaly). Judging from high-resolution chemostratigraphic (C, Sr) studies, the observed neritic response modes are diachronous in nature and certain biotic changes (orbitolinid-rich sediments, Lithocodium blooms, carbonate platform drowning) clearly predate the deposition of OAE1a black-shales. The perturbations observed in the neritic realm underline the previously quoted progressive nature of Late Barremian-Early Aptian environmental change. Considering the observed time lag between the earliest biotic perturbations and widespread oceanic anoxia, a volcanic scenario related to the release of large volumes of CO2 during the formation of the Ontong Java large igneous province seems at least likely. The aim of the current project is to reconstruct the evolution of carbonate platform ecosystems in the northern subtropical realm during the early onset of enhanced (submarine) volcanic activity. A Late Barremian carbonate platform succession (Sausset-les-Pins section), deposited on a proximal part of the Provence platform (Marseille area, SE France), has been investigated applying high-resolution chemostratigraphy and detailed sedimentological analysis. The 60-m thick section is composed of peloidal to bioclastic packstones and grainstones rich in rudist bivalves (Urgonian limestones sensu stricto) and subordinate mudstones and wackestones. In order to obtain information on the palaeoecological and palaeoenvironmental boundary conditions of this subtropical carbonate platform, we combine (i) an in-depth microfacies analysis based on 60 thin sections with (ii) a detailed geochemical analysis of rudist bivalve shells (Toucasia, Monopleura and Requienia). The outer (fibrous prismatic) low-Mg calcite shell layer of these rudists is relatively resistant against diagenetic alteration and therefore might serve both as chemostratigraphic (C + Sr) and palaeoenvironmental archive. Intra-shell (sclerochronological) variations in isotopic (δ18O, δ13C, clumped isotopes) and geochemical composition (Sr, Fe, Mn, Ba, Ca/Mg) will provide insights into seasonal (intra-annual) and long-term (Myr) palaeoclimatic and palaeoenvironmental changes. The outcome of this work will be of significance both for those studying the triggering factors of oceanic anoxic events and the palaeoecology of rudist bivalves.

The Valanginian stage displays the first major perturbation of the carbon cycle of the Cretaceous period. The Valanginian Weissert episode is associated with a positive excursion (CIE) in δ13Ccarb and δ13Corg values, and the occurrence of a crisis in pelagic and neritic carbonate production (Weissert et al., 1998; Erba, 2004, Föllmi et al., 2007). As for Cretaceous oceanic anoxic events (OAEs), the carbon anomaly is explained by the intensification of continental biogeochemical weathering triggering an increase in marine primary productivity and organic-matter preservation. However, to the contrary of OAEs, the organic matter trapped in the Tethyan Ocean during the Valanginian is both marine and continental and the occurrence of a widespread anoxia could not be evidenced (Westermann et al., 2010; Kujau et al., 2012). The resulting marine Corg burial rates were probably not sufficient to explain the shift in δ13C values and an alternative scheme has been proposed by Westermann et al. (2010): the carbonate platform crisis combined with the storage of organic-matter on the continent may be the major triggers of the δ13C positive shift. (Westermann et al., 2010). We present the results of an analysis of the Wawal drilling core (Mid-Polish Trough), which is of particular interest because of its near-coastal setting and its exceptional preservation, demonstrated by the presence of up to 17 wt.% aragonite. The section consists in marine silty to sandy clays deposited on top of a lower Berriasian karstified limestone. It covers the Early and early Late Valanginian, and displays the onset of the positive excursion. The lack of anoxia is evidenced by trace-element and Rock-Eval data. Two intervals of phosphogenesis are emphasised that appear equivalent in time to the condensed horizons of the northern Tethyan region (Helvetic Alps). A rapid climate change toward less humid and seasonally-contrasted conditions that is similar to the northern Tethyan areas is observed closed to the early-late Valanginian boundary. This is associated to a decoupling of the δ13Ccarb and δ13Corg, which is interpreted as a change in atmospheric pCO2. References Erba, E., Bartolini, A. and Larson, L.R. (2004) Valanginian Weissert oceanic anoxic event. Geology, 32, 149-152. Föllmi, K.B., Bodin, S., Godet, A., Linder, P. and van de Schootbrugge, B. (2007) Unlocking paleo-environmental information from Early Cretaceous shelf sediments in the Helvetic Alps: stratigraphy is the key! Swiss journal of geosciences, 100, 349-369. Kujau, A., Heimhofer, U., Ostertag-Henning, C., Gréselle, B. and Mutterlose, J. (2012) No evidence for anoxia during the Valanginian carbon isotope event - an organic-geochemical study from the Vocontian Basin, SE France. Global and Planetary Change, doi: 10.1016/j.gloplacha.2012.04.007. Weissert, H., Lini, A., Föllmi, K.B. and Kuhn, O. (1998) Correlation of Early Cretaceous carbon isotope stratigraphy and platform drowning events: a possible link? Palaeogeography, Palaeoclimatology, Palaeoecology, 137, 189-203. Westermann, S., Caron, M., Fiet, N., Fleitmann, D., Matera, V., Adatte, T. and Föllmi, K.B. (2010) Evidence for oxic conditions during oceanic anoxic event 2 in the northern Tethyan pelagic realm. Cretaceous Research.

Theropod dinosaur teeth from a Lower Cretaceous karst filling in Devonian reef limestone (Massenkalk) located near the village of Balve on the northern margin of the Rhenish Massif, Germany, are described. Palynological evidence indicates that the karst filling took place during the Late Barremian to (Early) Aptian time interval. Palaeontological excavations carried out during several years at the Balve locality yielded remains of various animal groups, including sharks, amphibians, turtles, crocodiles, pterosaurs, herbivore dinosaurs, and, rarely, mammals. Of particular interest is an assemblage of different theropod dinosaur teeth, which has been characterized with the help of dental comparative morphometry. Based on these analyses, the teeth material from the Balve excavation can be assigned to five morphological groupings including dromaeosaurid and tyrannosauroid theropods. Morphological comparison of the theropod dinosaur teeth record with finds from other fossil localities in western and northwestern Europe of similar age shows clear similarities, but also some distinct differences.

Pervasive growth of microencrusters (Lithocodium/Bacinella) characterizes shortlived stratigraphic intervals in Lower Aptian shallow-water carbonate platform settings of the central and southern Tethys. Although a causal relationship between this peculiar shallow-water facies and the early Aptian oceanic anoxic event (OAE) 1a seems likely, the temporal and spatial distributions of Lithocodium and Bacinella mass occurrences in the rock record point to a rather complex pattern. Possible controls include various global and regional drivers expressed in environmental perturbation of neritic ecosystems. Microencruster blooms have hitherto been reported to occur at the onset and in the aftermath of OAE 1a, slightly pre- or postdating the deposition of dark organic-rich black shales in pelagic basins. This study presents evidence for a punctuated and well-expressed early Aptian bloom of the ulvophycean green algae Lithocodium aggregatum observed at the proto-North Atlantic margin, Lusitanian Basin, Portugal. Similar to southern and central Tethyan sections, a Lithocodium-dominated interval temporally replaces the rudist-dominated platform ecosystem. This Lithocodium-rich horizon is composed of oncoidal floatstones and boundstones, including a well-exposed biohermal level, and reaches a thickness of up to 6 m. High-resolution carbon-isotope stratigraphy shown here clearly argues for Lithocodium to represent a biotic harbinger of environmental change in the run-up of OAE 1a. Chemo stratig raphy provides evidence that the subsequent carbonate platform breakdown in the proto-North Atlantic was coeval with an early Aptian carbonate platform drowning episode observed in the northern Tethys prior to OAE 1a. A regionally enhanced nutrient level and a relative sealevel rise are suggested to have triggered the transient mass occurrence of Lithocodium microencrusters, which also may have been influenced by elevated atmospheric CO2 concentrations related to the emplacement of the Ontong Java large igneous province. Upwelling water masses and enhanced terrigenous runoff due to increased weathering may have served as possible sources of the required nutrients, which tentatively diminished and finally interrupted the metazoan carbonate platform factory.

The late Early Cretaceous greenhouse climate has been studied intensively based on proxy data derived essentially from open marine archives. In contrast, information on continental climatic conditions and on the accompanying response of vegetation is relatively scarce, most notably owing to the stratigraphic uncertainties associated with many Lower Cretaceous terrestrial deposits. Here, we present a palynological record from Albian near-shore deposits of the Lusitanian Basin of W Portugal, which have been independently dated using Sr-isotope signals derived from low-Mg oyster shell calcite. 87Sr/86Sr values fluctuate between 0.707373 ± 0.00002 and 0.707456 ± 0.00003; absolute values and the overall stratigraphic trend match well with the global open marine seawater signature during Albian times. Based on the new Sr-isotope data, existing biostratigraphic assignments of the succession are corroborated and partly revised. Spore-pollen data provide information on the vegetation community structure and are flanked by sedimentological and clay mineralogical data used to infer the overall climatic conditions prevailing on the adjacent continent. Variations in the distribution of climate-sensitive pollen and spores indicate distinct changes in moisture availability across the studied succession with a pronounced increase in hygrophilous spores in late Early Albian times. Comparison with time-equivalent palynofloras from the Algarve Basin of southern Portugal shows pronounced differences in the xerophyte/hygrophyte ratio, interpreted to reflect the effect of a broad arid climate belt covering southern and southeastern Iberia during Early Albian times.

The Valanginian time interval (Early Cretaceous) is characterized by a positive carbon isotope excursion (CIE) which represents the first of several prominent Cretaceous δ13C anomalies. A combined chemostratigraphic and organic-geochemical approach has been chosen to investigate the composition and distribution of sedimentary organic matter (OM) deposited before the Valanginian CIE, during its onset and plateau-phase. This was done to test whether this CIE is accompanied by changes in marine primary production and/or OM preservation. Biostratigraphically well-calibrated deposits from two hemipelagic sections located in the Vocontian Basin of SE France are used as sedimentary archives. A newly established high-resolution δ13C record covering the composite succession shows a characteristic Valanginian pattern and enables a detailed correlation with existing carbon isotope curves from the northern Tethyan margin. The analyzed solvent extractable fraction of the sedimentary OM is mainly composed of a marine origin with an admixture of land plant material. Variations in specific biomarkers for cyanobacteria (2α-methyl-hopanes), dinoflagellates (dinosterane or 4-desmethyl-23,24-dimethyl steranes) and terrigenous plant-derived OM (odd‐numbered long-chain n-alkanes) as well as the sterane/hopane ratio, the C35 hopane index and the isoprenoids pristane and phytane were investigated. In contrast to the well-studied mid-Cretaceous Oceanic Anoxic Events (OAEs), neither significant OM enrichment nor prominent fluctuations in the selected biomarker abundances can be observed during the build-up phase of the Valanginian CIE. This points to relatively stable marine paleoenvironmental conditions with well-oxygenated bottom waters. Prior to the CIE, four cm-thick, finely laminated, dark layers (known as Barrande layers) with total organic carbon content reaching up to 4% show an exception from the generally stable biomarker pattern. Sedimentological and biomarker evidence support deposition under less oxygenated conditions for the Barrande layers. However, their occurrence clearly predates the onset of the positive δ13Ccarb shift (by about 180 kyrs). Contrary to the subsequent mid-Cretaceous CIEs, the occurrence of widespread anoxia associated with the Valanginian CIE cannot be confirmed for the Vocontian Basin.

The late Early Cretaceous greenhouse climate has been studied intensively based on proxy data derived essentially from open marine archives. In contrast, information on the response of coastal settings is relatively scarce - most notably due to the stratigraphic uncertainties associated with many Early Cretaceous siliciclastic-rich near-shore marine deposits. Here, we present a revised stratigraphic assignment of Albian near-shore deposits of the Lusitanian Basin of W' Portugal, which have been independently dated using C- and Sr-isotope signals derived from bulk rock and low-Mg oyster shell calcite. Studied sections include the Guincho section (near Cascais) and the Praia do Sul and Praia Sao Julia sections (south of Ericeira). Carbon isotope trends based on bulk rock carbonate are difficult to correlate between the different sections, most probably due to the heterogeneous composition and diagenetic alteration of the carbonate fraction. In contrast, analysis of the low-Mg calcite shell of abundant oysters from these successions provides some promising results. Following a detailed screening of the shell material (incl. cathololuminescence microscopy, trace element geochemistry) for diagenetic alteration, C- and Sr-isotope measurements have been carried out. Sr-isotope analysis of a first set of samples (Guincho section) was done using laser-ablation multi-collector ICPMS technique, which allows for sampling of small shell areas. 87Sr/86Sr ratios of low-Mg oyster shell calcite fluctuate between 0.707373 ± 0.00002 and 0.707456 ± 0.00003; absolute values and the overall stratigraphic trend match well with the global open-marine seawater signature during Albian times. Based on the new Sr-isotope data, existing biostratigraphic assignments of the Guincho section are corroborated and partly revised. In summary, the use of low-Mg oyster shell calcite represents a promising tool for the age assignment of Mesozoic siliciclastic-rich near-shore deposits and provides a stratigraphic resolution unmatched by conventional biostratigraphic approaches.

Environmental perturbations associated with the Oceanic Anoxic Event (OAE) 2 at the Cenomanian-Turonian boundary (~93.5 Myr ago) include significant changes in sea-surface temperature, oceanic circulation and marine carbon cycling. Widespread and massive organic carbon burial observed in marine sediments has been linked to a large and abrupt decline in atmospheric [CO2], affecting both, climate and biota. In recent years, work has focused on the chemo- and biostratigraphy of this event as well as on the molecular composition of marine organic-rich black shales deposited during the OAE2. Whereas the response of the marine realm to this event is well documented, data on the impact of the OAE2 on terrestrial vegetation patterns and carbon cycling is almost absent. In order to investigate the continental response to the OAE2, we studied the Cassis section of SE France with an integrated approach, including stable isotope chemostratigraphy, optical organic matter (OM) analysis and organic geochemistry. In contrast to most other sedimentary records covering the OAE2, the Cassis section is characterized by a high terrestrial OM fraction as indicated by RockEval data and visual inspection. Carbon isotope data derived from both, marine carbonate and bulk OM show a characteristic carbon isotope excursion (CIE) allowing for chemostratigraphic correlation with existing OAE2 isotope curves. Observed differences in the amplitude of Ccarb and Corg isotope records across the OAE2 are often used to infer changes in atmospheric [CO2]. For the Cassis record, increased input of land plant-derived OM, as indicated by the branched vs. isoprenoid tetraether (BIT) index, seems more likely to explain for the isotopic offset. Long-chain n-alkanes from the thermally immature deposits show a moderate odd-over-even carbon number predominance (CPI = 1.7-2.3) indicating origin from epicuticular plant waxes. The stable carbon isotopic composition of the odd-numbered C27 and C29 n-alkanes ranges from -29.3 to -33.4 permil. Co-variation of the land plant-derived n-alkane isotope signature and the marine carbonate record highlights the involvement of the entire ocean-atmosphere system during the OAE2 carbon cycle perturbation. Comparison with published n-alkane data from Atlantic deep-sea deposits (DSDP site 367, offshore NW Africa) shows a significant isotopic offset between the biomarker signatures with the data from France being ~5 permil more negative during the plateau phase of the CIE. The significantly smaller carbon isotope shift observed in mid-latitudes (France) compared to the palaeotropics (NW Africa) points to differing ecophysiological response mechanisms of the vegetation to the climatic perturbation associated with the OAE2.

After a long-lasting period of relatively stable conditions during the late Jurassic to earliest Cretaceous, the Valanginian was a time of climatic and environmental perturbations. Proposed changes include fluctuations in atmospheric pCO2, an accelerated hydrologic cycling, a cooling phase, and changes in composition and abundances of the marine fauna. A prominent perturbation of the global carbon cycle is documented in a globally recorded positive δ13C shift. Widespread storage of Corg-rich sediments in ocean basins, probably accompanied by anoxic conditions has long been supposed to explain for the positive carbon isotope anomaly. However, no widespread deposition of black shales has been shown for the Valanginian. Research on the Valanginian carbon cycle has focused on marine environmental changes, while studies on continental archives are scarce. This study deals with stable isotope chemostratigraphy, spore-pollen assemblages, palynofacies, and organic geochemistry of two successions located in the northwestern Tethyan realm (Vocontian Basin, SE France) and the Carpathian seaway (Polish Trough, central Poland). For both sites no evidence for anoxic conditions in the form of the occurrence of specific biomarkers like isoreniratene are found. Spore-pollen assemblages from both localities show many similarities in terms of composition, diversity and abundances of taxa. Both are dominated by conifer pollen and fern spores. During the initial phase of the δ13C shift the palynological compositions of both sites are quite diverging. Here, the French site is characterized by a decrease in spore abundances not being observed for the Polish site. This is followed by a peak in fern spores for both sites. Bulk Corg and algal-derived pristane and phytane follow the positive isotope shift of Ccarb with a lead of ~200 kyrs. Land plant derived long chain C27 n-alkanes for the Vocontian Basin as well show this positive shift while for the site at the Carpathian seaway the coeval shift is negative. PCO2 reconstructions based on the Δδ record point to an increase in atmospheric pCO2 for this time interval. Results are interpreted to reflect an increase in aridity at the French site, whereas conditions become more humid in the hinterland of the Carpathian seaway during the initiation of the carbon cycle perturbation. This would explain for diverging compositions of vegetation and the negative shift in C27 n-alkanes of the Polish site, since an increase in humidity enhances discrimination in land plants and therewith the amount of implemented 12C. The subsequent peak in fern spores may point to supra-regional hostile conditions favoring massive appearance of fern plants, coinciding with pCO2 drawdown, arid conditions, and the initiation of a cooling phase during the plateau-phase of the carbon isotope excursion. Results point to an important role of continental environments during the complex pattern of environmental and climatic changes accompanying and/or causing the Valanginian carbon isotope anomaly.

Lower Aptian Tethyan carbonate platforms were affected by severe perturbations in the carbonate production and platform drowning, preferentially during OAE 1a. In the northern Tethyan realm, the Late Barremian is generally known for the widespread deposition of Urgonian limestones, which are composed of oligotrophic carbonates with rudists and corals. The deposition of these typical carbonates became interrupted during the earliest Aptian by an Orbitolina episode. Following this episode, oligotrophic carbonate production comes back with the Upper Urgonian. After this, a new deposition of a mesotrophic orbitolinids interval appears or, following the location in the northern Tethyan margin, several drowning horizons are recorded. They are interpreted to be coeval to the OAE 1a. In the central Tethyan and southern margin of the Tethys, the OAE 1a event is rather represented by an accumulation of the problematic micro-organisms Lithocodium/Bacinella. Nonetheless, this classical repartition is challenged by several outcrops in the Western Portugal where rudist/coral/Lithocodium-Bacinella and orbitolinids co-occur in Late Barremian-Early Aptian deposits. The aim of this study is to investigate the factors leading to this unusual faunal and floral co-existence during the Early Aptian. This is done by studying three outcrop sections in the Lusitanian basin (Ericeira, Praia Grande and Crismina, Western Portugal) from a drowning surface to the siliciclastic sedimentation installation. This interval corresponds to the end of the Ponta Alta Member and the Praia da Lagoa Member. The Ponta Alta Member is composed of massive rudist beds topped by a prominent discontinuity surface with encrusted rudists, corals and orbitolinids and overlain by orbitolinid-rich marls and limestones. These marine deposits are unconformably overlain by coarse-grained continental siliciclastics of the Rodízio Formation. The limited stratigraphic thickness (around 20 m) of this succession allows for a high-resolution sedimentological and geochemical analysis. In order to quantify nutrient input, which is the prime control of the trophic level, phosphorus content will be measured. A detrital index is calculated based on XRD analysis and clay mineralogy is used as a proxy for paleoclimate reconstruction. These mineralogical and geochemical analyses are also combined with a detailed sedimentological study. The results of this project have the potential to open new perspectives on the mid-Cretaceous paleo-ecology of carbonate platform and particularly the behavior of reefal ecosystems under increasing nutrient levels.

The Valanginian (Lower Cretaceous) was characterized by a distinct positive carbon isotope excursion (CIE), spanning ∼2 Ma, which represents the first of several prominent Cretaceous δ13C anomalies. During the Valanginian CIE the whole marine and terrestrial carbon system was affected, evidenced by Ccarb and Corg records of marine and terrestrial archives, showing positive shifts of ∼1.5 to 2.5 for marine carbonates, ∼2 to 3 for organic matter (OM) from marine sediments and ∼4 to 5 for terrestrial plant-derived OM. This CIE was assigned to be the result of an anoxic event (Weissert OAE) and was accompanied by changes in pCO2, a distinct cooling and turnovers in the marine fauna (e.g. Lini et al., 1992; Wortmann and Weissert, 2000; Erba et al., 2004; Gröcke et al., 2005). Causal links are yet to be assessed. Research so far has mainly focused on the interaction between the marine carbon cycle and the oceanic biosphere while information on dynamics in the terrestrial environment and interactions with the atmosphere is sparse. In this study, a combined palynological and organic-geochemical approach has been chosen to investigate the composition and distribution of sedimentary OM deposited in hemipelagic and shallow marine settings in the Vocontian Basin (SE France; La Charce, Vergol, Morenas) and the Carpathian seaway (Central Poland; Wawal), covering the late Early to Late Valanginian/Early Hauterivian (e.g. Kutek et al., 1989; Gréselle, 2007). While the OM of the French successions is of predominantly marine origin the Polish site reveals distinct terrestrial input. Biomarker evidence points to relatively stable palaeoenvironmental conditions with well-oxygenated bottom waters prevailing during the CIE. Fluctuations in the marine biota seem to be related to temperature changes. In contrast to the mid-Cretaceous OAEs, no severe fluctuations in biomarker abundances and associated marine biota (dinoflagellates, methanotrophic bacteria and cyanobacteria) can be observed during the build-up phase of the Valanginian CIE. Contrary to later Cretaceous CIEs there is no evidence for the marine realm being a site of enhanced organic carbon accumulation/preservation, and the occurrence of widespread anoxia during the CIE cannot be confirmed for the locations investigated. The marine realm can therefore probably be excluded to be the major trigger for this carbon isotope anomaly. Changes on continents may have played the key role for this Early Cretaceous event (van de Schootbrugge et al., 2000; Westermann et al., 2010). Variations in terrestrial biomarker and spore-pollen compositions are under investigation. Our results will assess vegetation and associated humidity changes within the framework of Valanginian climatic and paleoenvironmental changes. Therby the role of the terrestrial realm during this carbon cycle perturbation will be enlighted.: Impact des variations paléoclimatiques sur la sédimentation carbonate au Valanginien. – PhD-thesis, 1-179. Université Lyon1 – Claude Bernard, France. Gröcke et al., 2005 The Upper Valanginian (Early Cretaceous) positive carbon-isotope event recorded in terrestrial plants. Earth

A widely accepted hypothesis proposes that the Early Aptian demise of carbonate platforms in the northern Tethyan realm reflects the impact of environmental changes that eventually led to the deposition of organic-rich basinal sediments during oceanic anoxic event (OAE) 1a. In fact, the temporal correlation of oceanic anoxia and platform drowning has not been rigorously tested and evidence indicating causality is debated. The present paper provides a high-resolution carbon- and strontium-isotope chronostratigraphy combined with detailed sedimentological analysis applied to the Barremian-Aptian Urgonian carbonate platform development at the northern rim of the Tethys (Subalpine Chains, Haute-Savoie, ESE France). A characteristic Barremian-Aptian carbon- and strontium-isotope pattern below the onset of OAE 1a interval permits precise platform-to-basin correlation with the Barremian stratotype locality of Angles (SE France). This chemostratigraphic pattern equally allows for a correlation with well-studied shoal-water and pelagic records of the northern and central Tethys. Strontium-isotope stratigraphy provides a high-resolution numerical age-data set, indicating an earliest Aptian age (<124.5 ± 0.4. Ma) of platform demise in the Subalpine Chains. The detailed platform-to-basin correlation obtained in France clearly illustrates that shoal-water carbonate production in the Urgonian platform ceased about 300. kyr before the most negative values of the characteristic negative carbon-isotope anomaly, which marks the beginning of OAE 1a black-shale deposition. The stratigraphic results confirm (i) the theory of an Early Aptian northern Tethyan platform drowning episode predating OAE 1a and (ii) document the temporal response of shoal-water carbonate platforms to the environmental perturbations prior to the OAE acme.

Ocean-wide anoxic events represent intensively investigated anomalies in the global carbon cycle. Most previous research has focussed on hemipelagic and pelagic settings and on the relationship between black-shale deposition and carbon-isotope excursions. The study of ocean-wide anoxic events and coeval shallow-water settings is now increasingly seen as an interesting complementary approach, but one that is not without problems. Whereas platform drowning characterizes the Early Aptian of the northern Tethyan margin, Lithocodium–Bacinella-rich facies and ongoing shoal-water sedimentation at the southern Tethyan margin (Oman) bears important information on potential causes of carbon-cycle perturbations. The present paper seeks to test the supra-regional relevance of the Oman data by investigating coeval central Tethyan limestones. Three Lower Aptian shoal-water sections in Istria (Croatia), deposited on the isolated Adriatic Carbonate Platform, are investigated applying chemostratigraphy (carbon and strontium) and detailed sedimentological analysis. The focus is on peritidal to lagoonal facies characterized by mass occurrences of Lithocodium–Bacinella, an enigmatic microencruster community. Lithocodium–Bacinella facies occurs predominantly in layers ranging from one to several centimetres in stratigraphic thickness, with several layers merging to metre-thick packages. Growth fabrics within the layers include oncoidal morphotypes, lumps, interconnected patches and columns, layers and rare nodular to massive bindstone facies. These growth patterns show a remarkable regional extent and consistency over study sites distributed several kilometres apart. This widespread distribution suggests that specific Lithocodium–Bacinella morphotypes might serve as regional stratigraphic markers. The high-resolution carbon-isotope chemostratigraphy presented here is based on pristine rudist shells and matrix micrite samples and calibrated against strontium-isotope data obtained from screened rudist low-Mg calcite. The chemostratigraphic data are consistent with existing biostratigraphic data and place the studied strata at the onset of Early Aptian oceanic anoxic event 1a. Moreover, results indicate the near-coeval nature of Lithocodium–Bacinella bloom facies in Istria and Oman. The outcomes of this study point to latitudinally different responses of Tethyan shoal-water carbonate systems (platform drowning versus Lithocodium–Bacinella blooms) to the ocean-wide anoxic event 1a.

The radiation of flowering plants during the Cretaceous represents a marked evolutionary turnover from gymnosperm- to angiosperm-dominated ecosystems within a time span of about 30 Ma. Despite the importance of this profound ecological transformation, many aspects regarding the timing, floral composition and spatial distribution of early angiosperms are poorly documented. Here, we present a record of early angiosperm pollen from the Brazilian Araripe Basin from the late Aptian to early Albian time interval. For this study, 17 samples from 5 sedimentary sections, spanning a total of ∼ 150 m, have been investigated for their palynological content with particular attention on the occurrence of angiosperm pollen. Our results show a relatively high angiosperm pollen diversity of 70 different taxa, including numerous undescribed forms. Across the succession, angiosperm pollen accounts on average for 7% of the total palynoflora, with maximum abundances reaching 18%. Dominant taxa include monocolpate pollen of “magnoliid” or monocotyledon origin (e.g. Stellatopollis, Retimonocolpites, Pennipollis, Dichastopollenites, and Trisectoris) as well as pollen with eudicotyledon affinities (e.g. triaperturate forms like Rousea, Tricolpites, and Striatopollis). Judging from the existing evidence it appears that the diversity of the late Aptian–early Albian angiosperm palynoflora from the Araripe Basin has been underestimated. In addition, the composition of the total palynoflora shows congruent shifts in the abundance of hygrophilic ferns, Afropollis spp. and angiosperm pollen. The co-occurrence of moisture-loving ferns and early angiosperm pollen may support the hypothesis that early angiosperms evolved and diversified in moist and shady disturbed habitats near the palaeoequator.

Exceptional fossil preservation (incl. soft-tissue phosphatization) within organic-rich black shales is often associated with the formation of a protective carbonate shell surrounding the fossil specimen. Whereas the mechanisms controlling soft-tissue mineralization during the earliest stage of fossilization are considerably well understood (e.g. Briggs and Kear, 1993), only limited information is currently available on the complex biogeochemical processes which lead to the precipitation of the concretionary carbonate mantle around the fossils. This study focuses on the organic and inorganic geochemistry of carbonate concretions derived from black shale deposits of the Early Cretaceous Santana Formation, Araripe Basin, NE Brazil (Martill, 1993; Heimhofer et al. 2008). This konservat-type fossil lagerstätte is world famous for its fossiliferous concretions hosting an exceptionally preserved fish and reptile fauna. The principle aim is twofold including (1) identification of the type and source of organic matter trapped within the Santana concretions and (2) assessment of the different microbial or microbially-mediated processes associated with successive concretion growth during early burial. Based on sedimentological evidence and palaeoenvironmental considerations, the involvement of a prokaryotic mat in early fossilization of the Santana biota has been proposed (Martill, 1988). At this stage, 3 different carbonate concretions hosting fossil fish remains (incl. Notelops brama, Calamopleurus sp. und an unknown specimen) have been analysed with a combined approach including organic molecular geochemistry, high-resolution stable isotope analysis, micro-XRF scanning and sedimentary petrography. Petrographic inspection shows a distinct zonal pattern of the carbonate shell surrounding the fossils. The innermost zone I shows an undulating and discontinuous lamination superimposed on a clotted fabric. Zone II is characterized by the frequent abundance of finely dispersed pyrite aggregates and a less pronounced lamination pattern, whereas the outmost zone III consists of a layer of medium to coarse-grained bundles of calcite crystals showing a "cone-in-cone" pattern. This zonal pattern is also visible in the distribution of elemental intensities derived from micro-XRF scanning results. In particular, variations in pyrite content are well displayed in the distribution of Fe and S intensities, probably reflecting the occurrence of BSR during concretion formation. Preliminary high-resolution carbon isotope profiles of the carbonate perpendicular to bedding show values varying between -9.1 and -19.7 permil and display a distinct trend throughout the concretion rim with relatively stable values of -12 permil in zones I and II. A distinct shift to less negative values occurs in the uppermost part of zone II. In contrast, the "cone-in-cone" calcitic fabric shows the most negative C-isotope signature with values as low as -19.7 permil. Organic geochemical analyses of sample material taken from the different zones confirm the low thermal maturity of the sedimentary organic matter. The biomarker composition is dominated by acyclic isoprenoids, steranes and by isorenieratane and its derivatives, whereas n-alkanes and hopanoids are of only subordinate importance. Biomarker composition and concentration shows considerable variations with the innermost sample displaying only few compounds occurring in relatively low concentrations (incl. squalane, phytane and isorenieratane derivatives). In contrast, the outermost sample shows a much broader biomarker spectrum probably indicative of marine background sedimentation. In summary, the preliminary petrographic and geochemical results provide convincing evidence for the involvement of different microbial processes actively influencing concretion growth. Analyses of new sample material as well as compound-specific carbon isotope measurements will provide further insights into the role of microbes in concretion formation. References Briggs DEG, Kear AJ (1993) Fossilization of soft-tissue in the laboratory. Science 259:1439-1442 Heimhofer U, Hesselbo SP, Pancost RD, Martill DM, Hochuli PA, Guzzo JVP (2008) Evidence for photic-zone euxinia in the Early Albian Santana Formation (Araripe Basin, NE Brazil). Terra Nova 20:347-355 Martill DM (1988) Preservation of fish in the Cretaceous Santana Formation, Brazil. Palaeontology 31:1-18 Martill DM (1993) Fossils of the Santana and Crato Formations, Brazil. Palaeontological Association, London, UK, pp 159

A lively controversy still exists between different authors dealing with the timing of northern Tethyan platform drowning and the Early Aptian oceanic anoxic event (OAE 1a). To the present day, there is no consensus if the OAE 1a black shales must be attributed to the Deshayesites weissi or the Deshayesites deshayesi zone (see discussion in Moreno-Bedmar et al., 2009). OAE 1a black shale deposition has been traditionally attributed to the Deshayesites weissi zone (Gradstein et al., 2004). Despite this disagreement about the biostratigraphic timing, several authors postulate a relation between biotic perturbations and environmental changes linked to OAE 1a, e. g. the disappearance of coral-rudist reefs related with the demise of the northern Tethyan Urgonian platforms in the Helvetic Alps (Weissert et al., 1998; Föllmi et al., 2008). In the central and southern Tethyan realm (Istria, Oman), OAE 1a is likely expressed as the transient mass occurrence of microencrusters (Lithocodium-Bacinella) and the coeval demise of the characteristic mid-Cretaceous framework-builders (rudists, corals). Chemostratigraphic data indicate that these microbial blooms coincide with the Deshayesites weissi zone (Huck et al., 2010, Rameil et al, 2010). These observations raise the question whether northern Tethyan platform drowning is coeval to microbial bloom periods in the central and southern Tethys? The analysis of all available literature and unpublished evidence demonstrates that well constrained age data are surprisingly scarce and controversial. The goal of the present research project is to compile a chemostratigraphic framework for the northern Tethyan platform drowning (Haute-Savoie, SE France) in order to shed light on the temporal constraints of platform drowning versus pelagic black shale deposition versus microbial blooms. Two Barremian to Aptian shoalwater sections (Cluses section, Grande Forclaz section) in the Subalpine Chains were investigated applying chemostratigraphy (carbon, strontium) and detailed sedimentological analysis. The lower part of the studied interval of both sections comprises limestones rich in rudist bivalves and intercalated oncoidal beds (including Lithocodium-Bacinella). The upper part consists of open to slightly protected lagoonal limestones (peloidal-foraminiferal grainstones) alternating with Orbitolina-rich intervals (Lower Orbitolina limestones?). Rudist shells are well preserved and relatively common. In the uppermost part, pulsed shedding of silt-sized siliciclastics is recorded and both sections are finally truncated and capped by the helvetic Garschella Formation, represented by siliciclastic glauconite-rich sedimentary rocks alternating with more argillaceous intervals. In essence, this stratigraphic succession is typical for the drowned Lower Aptian platforms observed along the northern Tethyan margin. Due to the lack of ammonites and a debated biostratigraphic control based on orbitolinids, a high-resolution chemostratigraphic framework (carbon and strontium) for the studied sections is established. Carbon-isotope chemostratigraphy is based on carbonate bulk samples. The obtained ages derived by 86Sr/87Sr isotope ratios (Strontium Isotope Stratigraphy, SIS) from screened rudists' low-Mg calcite are used to calibrate the carbon isotope stratigraphy as well as to pinpoint the timing of platform drowning. With respect to the timescale of Gradstein et al. (2004) preliminary chemostratigraphic data from Urgonian shoalwater sections in SE France indicate that the platforms at the northern margin of the Tethys Ocean drowned at the onset of OAE 1a black shale interval (Deshayesites weissi zone, close to the Aptian/Barremian boundary). This points to a near-coeval nature of pelagic black shale deposition, Oman and Istrian Lithocodium-Bacinella facies and platform demise in the northern Tethyan realm. References Föllmi, K.B. (2008) A synchronous, middle Early Aptian age for the demise of the Helvetic Urgonian platform related to the unfolding oceanic anoxic event 1a (« Selli event »). Revue de Paléobiologie, 27, 461-468. Gradstein, F.M., Ogg, J.G., Smith, A.G., Bleeker, W. and Lourens, L.J. (2004) A new Geologic Time Scale, with special reference to Precambrian and Neogene. Episodes, 27, 83-100. Huck, S., Rameil, N., Korbar, T., Heimhofer, U., Wieczorek, T.D. and Immenhauser, A. (2010) Latitudinally different responses of Tethyan shoal-water carbonate systems to the Early Aptian oceanic anoxic event (OAE 1a). Sedimentology (pending acceptance of revised version). Moreno-Bedmar, J.A., Company, M., Bover-Arnal, T., Salas, R., Delanoy, G., Martinez, R. and Grauges, A. (2009) Biostratigraphic characterization by means of ammonoids of the lower Aptian Oceanic Anoxic Event (OAE 1a) in the eastern Iberian Chain (Maestrat Basin, eastern Spain). Cretaceous Research, 30, 864-872. Rameil, N., Immenhauser, A., Warrlich, G.M.D., Vahrenkamp, V.C., Hillgärtner, H., Droste, H.J., Al-Mahruqi, I., Buhl, D., Schulte, U. and Kunkel, C. (2009) Chemostratigraphy-based correlation of Lower Shu'aiba Formation platform sections (Early Aptian, Sultanate of Oman). In: Aptian Stratigraphy and Petroleum Habitat of the Eastern Arabian Plate (Eds F.S.P. van Buchem, M.I. Al-Husseini, F. Maurer and H.J. Droste), 4. GeoArabia Special Publication (in press), Gulf PetroLink, Bahrain. Weissert, H., Lini, A., Föllmi, K.B. and Kuhn, O. (1998) Correlation of Early Cretaceous carbon isotope stratigraphy and platform drowning events: a possible link? Palaeogeography, Palaeoclimatology, Palaeoecology, 137, 189-203.

Terrestrial and marine sedimentary archives covering the Valanginian interval (136.8-133.9 Ma, Ogg et al., 2004) display a distinct positive delta13C-isotope excursion (CIE) of ~2.5 permil (Lini et al., 1992; Gröcke et al., 2005). The carbon isotope shift spans ~2.0 Ma and has been interpreted to reflect severe perturbations of the Early Cretaceous carbon cycle and paleoenvironmental conditions. According to different authors, the Valanginian CIE was accompanied by enhanced volcanic activity of the Paranà-Etendeka large igneous flood basalts, enhanced pCO2 (Lini et al., 1992; Weissert et al., 1998), widespread biocalcification crisis (Erba et al., 2004) and a distinct climatic cooling as evidenced by ice-rafted debris and glendonites from high-latitude sites. In addition, the positive CIE was assigned to be the result of an anoxic event, named the Weissert OAE (Erba et al., 2004). In this study, we investigate the composition and distribution of sedimentary organic matter (OM) deposited in a hemipelagic setting before, during, and after the Valanginian CIE. The aim of this study is to provide a detailed view on possible changes in OM deposition during a time of major paleoenvironmental and climatic stress. The chosen approach combines sedimentological and chemostratigraphical information (delta13Ccarb) with geochemical analysis of the bulk OM (incl. TOC, C/N, delta13Corg, Rock-Eval) and biomarker data. For this study, hemipelagic deposits located in the basinal part of the Vocontian Trough (SE France) covering the late Valanginian to early Hauterivian (Campylotoxus Zone to Radiatus Zone) (Gréselle 2007) have been sampled on a high resolution (sampling spacing of ~2/m). A total of three sections has been logged (La Charce, Vergol, Morenas), which consist of hemipelagic marl-limestone alternations and which allow for the construction of a composite succession. The delta13Ccarb values range between ~0.1 and 2.7 permil and show a characteristic stratigraphic trend typical for this time interval, including a prominent positive CIE. The high-resolution delta13Ccarb record allows for detailed correlation and comparison with existing chemostratigraphic records across this event. TOC values fluctuate between 0.20 and 4.05%, Rock-Eval pyrolysis results depict HI values of 134 to 383 mgHC/g TOC and OI values of 19 to 160 mg CO2/g TOC indicating the predominance of marine OM with only minor terrestrial inputs in all investigated samples. The aliphatic fraction of the OM extractable by organic solvents is dominated by n-alkanes, isoprenoids, and a variety of hopanes and steranes. No distinct changes during the CIE in the abundances of biomarkers specific for Dinoflagellates and methanotrophic bacteria are observed, pointing to no significant response of the marine biota in this basin to the carbon cycle perturbation. There is no indication for an anoxic water column during the CIE. Steranes show slightly enhanced values for the plateau phase of the excursion, and increasing values during the decline of the delta13C shift (e.g. dinosterane) what may just as well be due to the cooling episode or a change in sea-level (Melinte and Mutterlose, 2001). At this stage, the detailed analysis of the sedimentary OM does not provide evidence for the existence of an OAE or enhanced accumulation/preservation of OM associated with the Valanginian CIE. These findings point to paleoenvironmental changes on continents rather than in marine settings as causes for the isotope shift. References: Erba E. et al. (2004). Geology 32, 149-152. Gréselle B. (2007). PhD thesis, University Lyon1, Lyon. Gröcke D. et al. (2005). EPSL 240, 495-509. Lini A. et al. (1992). Terra Nova 4, 374-384. Melinte M. and Mutterlose J. (2001). Marine Micropaleontology 43, 1-25. Ogg J.G. et al. (2004). In: Gradstein FM, Ogg JG, Smith AG (eds.). A Geological Timescale 2004. Cambridge University Press, 63-86. Weissert H. et al. (1998). Paleogeography, Paleoclimatology, Palaeoecology 137, 189-203.

The laminated limestones of the Early Cretaceous Crato Formation of the Araripe Basin (North-eastern Brazil) are world-famous for their exceptionally well-preserved and taxonomically diverse fossil fauna and flora. Whereas the fossil biota has received considerable attention, only a few studies have focused on the sedimentary characteristics and palaeoenvironmental conditions which prevailed during formation of the Crato Fossil Lagersttte. The Nova Olinda Member represents the lowermost and thickest unit (up to 10 m) of the Crato Formation and is characterized by a pronounced rhythmically bedded, pale to dark lamination. To obtain information on palaeoenvironmental conditions, sample slabs derived from three local stratigraphic sections within the Araripe Basin were studied using high-resolution multiproxy techniques including detailed logging, petrography, μ-XRF scanning and stable isotope geochemistry. Integration of lithological and petrographic evidence indicates that the bulk of the Nova Olinda limestone formed via authigenic precipitation of calcite from within the upper water column, most probably induced and/or mediated by phytoplankton and picoplankton activity. A significant contribution from a benthonic, carbonate-secreting microbial mat community is not supported by these results. Deposition took place under anoxic and, at least during certain episodes, hypersaline bottom water conditions, as evidenced by the virtually undisturbed lamination pattern, the absence of a benthonic fauna and by the occurrence of halite pseudomorphs. Input of allochthonous, catchment-derived siliciclastics to the basin during times of laminite formation was strongly reduced. The δ18O values of authigenic carbonate precipitates (between −7·1 and −5·1‰) point to a 18O-poor meteoric water source and support a continental freshwater setting for the Nova Olinda Member. The δ13C values, which are comparatively rich in 13C (between −0·1 and +1·9‰), are interpreted to reflect reduced throughflow of water in a restricted basin, promoting equilibration with atmospheric CO2, probably in concert with stagnant conditions and low input of soil-derived carbon. Integration of lithological and isotopic evidence indicates a shift from closed to semi-closed conditions towards a more open lake system during the onset of laminite deposition in the Crato Formation.

Sr-isotope measurements of unaltered oyster shell calcite using laser-ablation multi-collector ICPMS techniques represent a powerful tool capable of establishing a chronostratigraphic framework for fossil near-shore deposits. This approach is tested on two shoal-water successions from the Portuguese Algarve and Lusitanian basins covering Late Barremian to Albian strata. 87Sr/86Sr values derived from low-Mg calcite of oyster shells fluctuate between 0.70717 ± 0.00001 and 0.70746 ± 0.00002; absolute values as well as stratigraphic trends match well with the global open-marine seawater signal. The new Sr-isotope results in combination with existing bio- and chemostratigraphic records allow for identification of an Early Aptian biocalcification crisis at both studied localities and show that this event has severely affected coastal environments along the evolving Atlantic. Siliciclastic intervals in the Algarve section are interpreted as near-shore equivalents of enhanced detrital shedding into shelf and deep-sea environments as a consequence of increased chemical weathering rates during humid climate episodes.

Organic matter from two black shale units in the Santana Formation, Araripe Basin, NE Brazil, has been studied to investigate the palaeoenvironmental conditions prevailing during formation of this famous fossil lagerstätte. Optical and organic geochemical analyses indicate a predominantly autochthonous source with very limited terrestrial input. Molecular fossils of green sulphur bacteria show that the water column was stratified with euxinic conditions reaching up into the photic zone. Thus, mass-mortality events of fish may be explained by intrusion of sulphide-containing waters. The low quantity of material derived from land plants in this interior marine setting is interpreted to reflect a consequence of enhanced marine productivity, resulting in dilution of the continental signal. Different depositional scenarios are proposed to explain our findings including (1) coastal erosion and nutrient leaching during a transgressive event, (2) intrusion of euxinic waters during an early Albian OAE or (3) an estuarine circulation pattern associated with thermohaline stratification.

The Late Aptian to Early Albian transition has previously been identified as a possible example of substantial climate cooling within the mid-Cretaceous greenhouse period. To study the response of continental weathering and terrestrial vegetation to this cooling episode at low- to mid-latitudes, marine nearshore deposits from the Algarve Basin (SW Portugal) have been investigated with a combined approach including palynology, clay mineralogy and bulk-rock geochemistry. In the Lower Aptian part of the succession, quartz-rich sandstone facies is accompanied by high abundances of early diagenetic kaolinite, which is interpreted to reflect episodes of enhanced humidity and high meteoric flow-through. In contrast, the Late Aptian to Early Albian deposits are characterized by high abundances of detrital clay minerals (mica and chlorite) indicating the dominance of physical weathering processes in the source area, most probably related to low precipitation rates in conjunction with tectonically enhanced erosion. Palynological data show a strong dominance of Classopollis pollen associated with low pteridophyte spore abundances, suggesting warm semi-arid to arid palaeoenvironments. Changes in sedimentation patterns from varicoloured lagoonal marls to thick-bedded shallow-water carbonates are neither expressed in the spore-pollen assemblages nor in the distributions of clay minerals which both remain essentially stable throughout the Late Aptian to Early Albian. These relatively stable patterns are in contrast with various lines of evidence, predominantly from high-latitude areas, that suggest a significant cooling during this time interval. Our study demonstrates that terrestrial environments of low- to mid-latitude regions were not significantly affected by the Late Aptian - Early Albian “cold snap”.

Pipe-like structures filled with massive and brecciated Fe-rich dolomites occur within a 5–6m sequence of otherwise horizontal, millimetre-laminated limestones of the Nova Olinda Member of the Crato Formation (Aptian, Lower Cretaceous) of north east Brazil. The pipe-fills predate compaction, contain hydro-brecciated host strata, developed penecontemporaneously with a carbonate laminite, and may represent methane seeps. Such seeps may have developed above buried topographic highs as fluids emanating from deeper strata migrated along buried discontinuities such as the basement/Cretaceous unconformity and buried faults in the basement.

Coastal mixed carbonate-siliciclastic and carbonate deposits of Late Barremian to Early Aptian age from the Lusitanian Basin (Portugal) are compared with a deep-sea succession (ODP 641) off the coast of Portugal. The coastal deposits show an abrupt cessation of rudist-dominated carbonate deposition marked by an emersion horizon and followed by the deposition of orbitolinid-rich marls during the Early Aptian. The subsequent development of the carbonate platform during the Late Aptian is masked by a hiatus. For this time interval shallow-water debris deposits of the deep-sea succession ODP 641 indicate that carbonate production in shallow-water areas resume in the early Late Aptian. Carbon-isotope stratigraphy in combination with available biostratigraphic data is used for intrabasinal correlation and for the correlation of the Portuguese with shallow-water successions from Switzerland, France, Oman and the Pacific. The correlation reveals that during the Early Aptian similar changes in their sedimentary patterns occur at the beginning of a marked negative shift of carbon-isotope values associated with the global deposition of organic rich black shales in the deep sea (OAE 1a). In all compared sections rudist-dominated carbonate deposition is stopped and followed either by orbitolinid-rich deposits, the deposition of microbial carbonates or by the drowning of the carbonate platform. The comparison shows that the deterioration for carbonate platform growth conditions during the Early Aptian occurred essentially simultaneously at the various localities. During this episode the ocean waters were in a preconditioned state of acidification stressing biocalcifying organisms. Sea level change combined with local effects like elevated nutrient levels and higher temperatures, were probably determining the nature of sedimentary change in shallow-water environments during the carbonate crisis. In the sections studied in Portugal the high abundance of orbitolinids overlying rudist limestones indicates that increased nutrient input may have played an important local role among the factors that caused an overall deterioration for carbonate producers during the late Early Aptian.

Pseudomorphs after hopper-faced halite occur at several horizons and in five distinctive morphologies in carbonate dominated members of the Late Aptian–Early Albian Crato Formation of the Araripe Basin in northeast Brazil. Some forms exhibit typical hopper-faced cubes with an outer veneer of marcasite with calcite and quartz in the centre. A second morph comprises compacted marcasite veneers exhibiting a collapsed cube morphology showing that compaction predated calcite and quartz precipitation. A third morph comprises four pointed ‘stars’ in a series of concentric circles, representing halite crystals that grew within the sediment and possibly tore apart a thin bacterial mat that bound the surface of the sediment. Pseudomorph size varies from 5–10 mm diameter for those replaced by several mineral phases to aggregates of up to 20 mm diameter for those replaced by silica. The presence of abundant halite pseudomorphs suggests that hypersaline waters prevailed during deposition of the Nova Olinda Member fossil Konservat Lagerstätte and were a contributing factor to the excellent preservation of its fossil assemblage.

Detailed and continuous palynological records from two well-dated successions in the Portuguese Algarve and Lusitanian Basins document the diversification of early angiosperm pollen during the Late Barremian to Middle Albian time interval. Based on dinoflagellate cyst biostratigraphy, an accurate stratigraphic framework has been established for the studied near-shore deposits resulting in distinct changes of the stratigraphic position of individual units. The qualitative and quantitative analysis of the palynofloras of the two sections revealed a total of 66 different types of angiosperm pollen. Most of them (55 taxa) are monoaperturate grains of magnoliid or monocot affinity. In both records, eudicots, represented by various tri- and polyaperturate taxa (11 taxa), are restricted to the Albian part of the sections. Angiosperm pollen grains display a distinct increase in both, diversity and relative abundance between the Late Barremian and the Middle Albian. Comparison with published palynofloras from other areas shows strong similarities with regard to floral composition and the timing of first appearances of particular angiosperm pollen forms. Our results indicate a new age interpretation of the well-known angiosperm mesofossil floras from the Portuguese Beira Litoral region which have been interpreted as Barremian or possibly Aptian in age. Several lines of evidence, including sequence- and biostratigraphy as well as palynology, indicate a post-Aptian age for these assemblages, hence demonstrating a major radiation phase during the Early Albian.

Although the exceptionally preserved fossils from the Crato Formation have attracted a multitude of palaeontological studies dealing predominantly with the systematics and taxonomy of the assemblage, reports on the sedimentology and depositional environment of this important Fossil Lagerstätte are rather scarce. There are even fewer studies on the geochemistry and sedimentary diagenesis of the formation. A few exceptions include analyses of the organic matter composition (Baudin and Berthou, 1996; Neumann, 1999; Neumann et al., 2003) and a study of evaporite mineral pseudomorphism in the Nova Olinda Member (Martill et al., 2007). Some workers have examined spot samples from the Crato Formation in studies on the Araripe Group as a whole (e.g. Berthou et al., 1990) and a few assessments of the palaeoenvironment have been undertaken (Cavalcanti and Viana, 1990; Martill and Wilby, 1993). For a better understanding of the unusual taphonomy and exceptional preservation of the Crato fossils, a more detailed knowledge of the physico-chemical conditions of the aquatic palaeoenvironment is necessary. Because the Crato Formation is a heterolithic sequence with both clastic and carbonate deposition, it is clear that many different and often contrasting environments are represented by the sedimentary sequence. Many previous analyses fail to address the situation, preferring to summarize the unit as a whole, and providing generally unsatisfactory interpretations. Here we concentrate on the sedimentology and geochemistry of the Nova Olinda Member of the Crato Formation, with a view to elucidating the sedimentary and diagenetic environment that resulted in the exquisite preservation of the fossil assemblage.

Introduction The Crato Formation comprises a series of laminated limestones inter-bedded with sandstones, marls and clays, sandwiched between a highly variable sequence of strata in the mainly Mesozoic Araripe Basin. Its distribution has not been completely mapped as an integral stratigraphic unit, although some beds of limestone were mapped by the Projeto Santana team in the 1970s (Moraes et al., 1976). The formation has never been formally defined, although Martill and Wilby (1993) proposed a type section in the river at Cascata near Crato, but exposures of the upper part of the Crato Formation sequence are only poorly exposed here compared with elsewhere. There have been a few attempts to define the unit (e.g. Martill and Wilby, 1993; Berthou et al., 1994), but it is not always clear what authors are referring to when discussing the Crato sedimentary unit, partly due to terminology and partly due to concept. Here we consider the Crato Formation to comprise a heterolithic suite of strata lying above the Rio da Batateiras Formation of Ponte and Appi (1990) and beneath a unit of evaporites termed the Ipubi Formation by Martill and Wilby (1993) (Figure 3.1). Its base is defined as the first appearance of laminated limestones and its top by the first appearance of the evaporites of the overlying Ipubi Formation (see Figures 3.4 and 3.8, respectively, below).

New stratigraphically controlled pollen data from the late Early Cretaceous of Portugal allow a recalibration of the classical continental succession of the Potomac Group (USA), which has long been used to demonstrate the gradual morphological changes of angiosperm leaves and pollen. The Portuguese record represents the best dated succession of angiosperm pollen assemblages of the interval between the late Barremian and the mid-Albian. Comparison of the angiosperm pollen record of the Potomac Group with the pollen assemblages from Portugal and with other independently dated records indicates that the distinct differences in the angiospenn pollen assemblages between the three formations of this group (the Patuxent Formation, Arundel Clay Formation and Patapsco Formation) are related to discontinuities. Our revised age model for the Potomac Group implies a major discontinuity between the Arundel Clay (of early Albian age), and the Patapsco Formation (of mid-Albian-early Cenomanian age). The Portuguese record reveals a so far undocumented radiation phase of angiosperms within the early Aptian to mid-Albian in which monocolpate angiosperm pollen of monocot and/or magnoliid affinity appear as a highly diversified group. These new findings imply that the onset of the radiation of monocots-magnoliids preceded the radiation of eudicots by at least 10 Ma.

Detailed records of spore–pollen assemblages, particulate organic matter (OM), dinoflagellate cysts and calcareous nannofossils provide new insights into the palaeoclimatic and palaeoceanographic conditions during formation of Early Cretaceous black shales in the Vocontian basin (southeastern France). The early Aptian Niveau Goguel, which corresponds to the OAE1a, and the regionally distributed late Aptian Niveau Jacob have been studied with regard to changes in terrestrial vegetation patterns, terrigenous inputs and palaeofertility conditions. Palynological results from both black shale intervals exhibit a rich and stable floral pattern, dominated by various ferns, different types of cycads, bennettites as well as by several conifer families. Dinoflagellate cyst assemblages and the calcareous nannofossil-based nutrient index show no prominent changes in surface water productivity across the two studied intervals in the Vocontian basin. Significant variations are observed in terrestrial detrital input indicated by changes in absolute abundances of marine and terrestrial palynomorphs. According to our results, the laminated, OM-rich horizons of the Niveau Goguel interval reflect deposition during times of reduced siliciclastic input. Episodes of pronounced condensation were accompanied by anoxic conditions preventing degradation of the predominantly marine-derived OM. In contrast, the Niveau Jacob is characterised by a strong increase in terrestrial palynomorphs, most probably reflecting an abrupt increase in riverine runoff. The enhanced terrestrial OM input may have triggered oxygen-depletion in bottom waters, resulting in turn in increased OM preservation. Our results highlight the variety of processes that controlled the accumulation of OM in the Vocontian basin and they illustrate that enhanced surface water productivity is not an indispensable prerequisite for the formation of mid-Cretaceous black shales.

Palynological records from the Western Portuguese and Algarve basins (Portugal) provide new insights on the timing and pattern of the early diversification of angiosperms (flowering plants) and its relationship to global environmental perturbations during the late Early Cretaceous. Angiosperm pollen displays a stepwise increase in both diversity and relative abundance during the late Barremian to middle Albian interval (ca. 124 104 Ma), reflecting the incipient radiation of flowering plants in lower midlatitude floras. Our results provide new evidence for the age interpretation of the previously described angiosperm mesofossil floras and associated in situ pollen assemblages from the Western Portuguese basin, until now interpreted as Barremian or possibly Aptian in age. Biostratigraphic and sedimentologic evidence indicates a post-Aptian age for these assemblages, hence demonstrating a major radiation phase of angiosperms during the early Albian. Correlation of the angiosperm pollen record with data on global paleoenvironmental changes suggests a link between the rapid adaptive radiation of flowering plants and major climatic and oceanographic perturbations during the late Early Cretaceous.

The deposition of organic-rich sediments during the late Early Aptian Oceanic Anoxic Event (OAE) 1a has been interpreted to result in a major decrease of palaeoatmospheric CO2 concentrations, accompanied by significant changes in the terrestrial flora. In order to test this hypothesis, the OAE 1a interval in the Vocontian Basin (SE France) has been studied with a combined approach including stable carbon isotopes, organic geochemistry and palynology. To estimate changes in palaeoatmospheric CO2 levels across the OAE 1a, the δ13C composition of presumed algal biomarkers (low molecular weight n-alkanes, steranes) and of bulk carbonate carbon are used. Our results yield estimated Early Aptian carbon dioxide partial pressure (pCO2) values three to four times the preindustrial level and only a moderate drop across the black shale event. This moderate drop in pCO2 is supported by palynological results. The frequency patterns of climate-sensitive sporomorphs (incl. pteridophyte spores, bisaccate pollen and Classopollis spp.) display only minor fluctuations throughout the studied section and indicate relatively stable patterns of terrestrial vegetation during and after formation of the OAE 1a black shale. The occurrence of a characteristic Early Aptian carbon isotope pattern across the OAE 1a interval permits accurate chemostratigraphic correlation with the well-studied Livello Selli interval of the Cismon record (N Italy). The contemporaneous formation of individual black shale layers at both sites indicates that transient episodes of dysoxic–anoxic bottom waters prevailed over large areas in the W Tethys Ocean independent of depositional setting. Comparison of the palynological data from the two locations displays significant differences in the frequency patterns of bisaccate pollen. The contrasting pollen spectra are interpreted to reflect prominent changes in the palaeoceanographic current patterns and/or selective sorting due to sea-level rise rather than latitudinal shifts of the major floral belts.

Rudist bivalves, benthic foraminifers and calcareous algae are common in the Upper Cenomanian-Turonian Tethyan inner platform deposits of the Sinai peninsula. In this study, special emphasis is placed on the vertical distribution of these benthic organisms across the Cenomanian-Turonian transition, and on laterally varying occurrences along a N-S transect involving a sequence stratigraphic interpretation of Cenomanian and Turonian sediments. A significant disturbance of latest Cenomanian carbonate production was followed by flooding of the Upper Cenomanian inner platform during the Early Turonian and the establishment of a new carbonate platform during the Middle-Late Turonian. Diversities and frequencies of the studied fossils are distinctively different in Cenomanian and Turonian deposits. Rudists and benthic foraminifers are common in the Upper Cenomanian successions but occurrences decline drastically in the Lower Turonian and recover again in the Middle-Upper Turonian. In contrast, calcareous algae of Upper Cenomanian deposits are species-poor and flourished in the Lower and Upper Turonian. In addition to these large scale distribution trends, the occurrences of the studied benthics is closely related to regional facies belts, which prevail in individual systems tracts. Rudists occur mainly in HSTs, benthic foraminifers and calcareous algae mainly in TSTs and HSTs. The correlation of facies, systems tracts and biota distribution suggests a link between repeated reorganisation processes of the depositional system due to relative sea-level changes and the distribution of individual benthic groups.

The Aptian is referred to as a time of major perturbations in the ocean-atmosphere system, documented in the widespread and repeated deposition of organic-rich shales, accompanying biological turnover and pronounced excursions in the carbon-isotope record. In the Vocontian basin, a stratigraphically well-constrained hemipelagic succession of mid-Cretaceous age provides a series of black shale horizons. Some of these black shales display a super-regional character, whereas others are of only regional extent. The Lower Aptian Niveau Goguel corresponds to the globally recognized oceanic anoxic event 1a and has been interpreted as a productivity-driven black shale, associated with major changes in marine micro- and nannoplankton, floral assemblages and a pronounced excursion in the carbon-isotope record. In contrast, the Upper Aptian Niveau Jacob is restricted to the northern margin of the western Tethys and is interpreted to reflect enhanced organic matter (OM) accumulation under mesotrophic conditions and/or increased runoff during a sea-level lowstand. To investigate the similiarities and differences of regional and super-regional black-shale depositional events with regard to possible trigger mechanisms and the prevailing paleoceanographic setting, these two different black-shale horizons were studied in detail. The combination of organic geochemistry and palynofacies analysis is applied to characterize variations in type, distribution and preservation of the sedimentary organic matter. Both horizons are marked by the occurrence of immature organic matter (OM) of primarily marine origin. Compositional changes of the OM are indicated by variations in the odd-over even predominance of n-alkanes and by changing contributions of marine and terrestrial palynomorphs. Pristan/Phytan ratios and homohopane index indicate deposition of the organic carbon-rich intervals under dysoxic to anoxic conditions in both studied sections. In the Niveau Jacob, the carbon-isotopic signature of bulk Ccarb, bulk Corg and of selected organic molecules shows only minor variations throughout the organic-rich interval. In contrast to this, the Niveau Goguel displays a prominent carbon isotope excursion of about 2.5 per mil in both bulk Ccarb and Corg, which has been documented from many sites and different environments. The carbon isotope signature of selected n-alkanes parallels the bulk OM profile almost perfectly, but shows a depletion of 3 per mil to 4 per mil compared to the bulk OM signal. Palynofacies results indicate an increase in both, marine and terrestrial OM within the black shale intervals. Whereas the increase in marine amorphous OM is interpreted to reflect enhanced productivity and preservation, the higher terrestrial fraction points towards changing weathering conditions and/or changes of the floral assemblage in the hinterland. Variations in the relative amount of bisaccate pollen and in the spore/pollen ratio are interpreted to reflect the response of terrestrial environments to climatic perturbations during times of black shale formation.

ABSTRACT The carbon-isotope signature of terrestrial organic matter (OM) offers a valuable tool to develop stratigraphic correlations for near-shore deposits. A mid-Cretaceous coastal succession of the western Algarve Basin, Portugal, displays a marked negative δ13C excursion ranging from − 21.2‰ to − 27.8‰ in the Early Aptian followed by two shifts towards higher values (up to − 19.3‰) during the Early and Late Aptian, respectively. The dominance of cuticle and leaf debris in the bulk OM fraction is confirmed by optical studies, Rock-Eval pyrolysis and by comparison with the δ13C signature of four different types of fossilized land-plant particles. Correlation of two terrestrial δ13Cbulk OM records from different study sites leads to a significant enhancement of the intrabasinal stratigraphic correlation within the Algarve Basin. Three prominent excursions in the Portuguese records can be correlated with existing δ13C curves from pelagic and terrestrial environments. The general carbon-isotope pattern is superimposed by small-scale fluctuations which can be explained by compositional variations within the OM.

The carbon-isotope composition of terrestrial organic matter (OM), obtained from Aptian coastal deposits of the western Algarve basin, Portugal, displays significant small- and large-scale variations throughout the record, which can be related to perturbations of the global carbon-cycle. The dominance of continent-derived plant debris in the bulk OM fraction is confirmed by optical studies, Rock-Eval pyrolysis and by comparison with the delta 13C signature of different types of vascular land-plant particles, including charcoal, lignite, cuticules and leaf fragments. Two terrestrial delta 13CbulkOM records from different study sites within the Algarve basin can be correlated on a high-resolution scale resulting in a significant enhancement of the stratigraphic resolution of these shallow water sections. The global significance of the Portuguese land-plant delta 13C data is demonstrated by comparison with existing terrestrial and marine carbon-isotope records and indicates that variations in the terrestrial delta 13C record are primarily controlled by changes in the carbon-isotopic composition of the mid-Cretaceous atmospheric CO2.

Changes in biogeochemical cycling and sedimentary development are well known from open marine sediments of the lower Cretaceous Tethyan-Atlantic realm. Coastal sediments in Portugal (Lusitanian Basin) show the imprints of global disturbances occurring during the Early Cretaceous. The successions can be correlated with pelagic sediments off the Portuguese coast (ODP 641) and with Tethyan shallow water and pelagic sediments. In the Lusitanian Basin the Barremian-Aptian succession is built up by neritic limestones, marlstones and siltstones, followed by massive biostrome limestones that are overlain by fluvial quartzose sandstones. Sequence stratigraphic investigations based on microfacies analysis revealed transgressive-regressive 2nd-order and 3rd-order cycles which can be used for intra- and interbasinal correlation. C-isotope studies indicate that the global carbon isotope pattern is, in part, overprinted by local factors. Values vary between -1 per mille to +2 per mille VPDP. In the lower Aptian a rise of 2,5 per mille is followed by a drop of 2 per mille which is comparable to well known data from the Tethys. Though the isotope values are shifted to the negative side they still reflect the global trend and can thus be used for chemostratigraphic correlation. The sudden change from carbonate to fluvial sandstone deposition in the Lusitanian Basin also coincides with global perturbations of the carbon cycle. Carbonate platform demise in the Tethys and the North Atlantic predates or coincides with intensified volcanic activity. Generally sudden input of siliclastics has been assigned to tectonic activity. However, eustatic sea level rise and low local subsidence at the time of deposition of the siliciclastics in the Lusitanian Basin don't indicate a classical low stand situation. The major facies change in the coastal succession coincides with changes in the carbon cycle as reflected by the C-isotope curves. This coincidence may suggest that increased influx of siliciclastics into the Lusitanian Basin may have been controlled by climate change related to the perturbation of the global carbon cycle.