Michael M. Joachimski

Friedrich-Alexander-University of Erlangen-Nürnberg | FAU · Department of Geography and Earth Sciences

In Scandinavia, the boundary between provisional Cambrian Stage 4 and the Wuliuan Stage is marked by a prominent unconformity ascribed to non-deposition and erosion during a eustatic sea-level fall that may partially correlate with the regressive ’Hawke Bay Event’. Wuliuan strata are widely distributed in Scandinavia, but exposures are relatively few and small. Hence, the stratigraphic succession has to be pieced together using information from several outcrops and available drill cores. The Wuliuan Stage of Scandinavia can be subdivided into three polymerid trilobite zones, in ascending order: the Eccaparadoxides insularis, Acadoparadoxides pinus and Ctenocephalus exsulans zones. The A. pinus and C. exsulans zones are equivalent to the Ptychagnostus praecurrens and P. gibbus agnostoid zones, respectively. The Wuliuan Stage of southeast Sweden comprises the silt- and mudstone-dominated Borgholm Formation, followed by dark grey to black, organic-rich siliciclastic mudstones of the Drumian through Lower Ordovician (Tremadocian) portion of the Alum Shale Formation. In southern and south-central Sweden, the upper or topmost part of the Wuliuan Stage is generally developed as a bioclastic limestone, the Exsulans Limestone Bed, assigned to the P. gibbus Zone. The Borgholm Formation is well developed in the Öland-Gotland area, southeast Sweden, and in Närke and Östergötland, south-central Sweden. On the island of Öland, it comprises the Grötlingbo, Mossberga, Bårstad and Äleklinta members. The Mossberga and Bårstad members are generally richly fossiliferous, and the fossil faunas are commonly dominated by trilobites, agnostoids (including condylopygids) and phosphatic-shelled brachiopods. A δ13Corg curve based on 51 samples from the Mossberga and Bårstad members in the recently retrieved Tingskullen drill core from northern Öland shows values between –32.1 and –29.1‰. Despite some scatter in the δ13Corg values through this part of the succession, the curve shows a general positive trend up-section. No distinctive excursion was captured, suggesting that the entire Acadoparadoxides (Baltoparadoxides) oelandicus Superzone (the ‘Oelandicus beds’) of Scandinavia is younger than the negative Redlichiid-Olenellid Extinction Carbon isotope Excursion (ROECE), which is known from near the top of Stage 4 and close to the traditional ‘Lower-Middle Cambrian boundary’ in many areas. A δ13Corg chemostratigraphy has been performed in the upper Wuliuan (Ptychagnostus gibbus Zone) and Drumian stages of the Almbacken and Tomten-1 drill cores from Scania, southern Sweden, and Västergötland, south-central Sweden, respectively. In the Almbacken drill core, the interval with dark grey to black mudstones and shales in the P. gibbus Zone between the Forsemölla and Exsulans beds is characterized by strongly negative δ13Corg values (~–33.5‰). In the lower Drumian above the Exsulans Limestone Bed there is an abrupt shift (~+1.5‰) to less negative values. A similar chemostratigraphic pattern occurs within the same interval in the Tomten-1 core. The strongly negative values in the P. gibbus Zone of Sweden may correspond to a distinct negative excursion that has been recorded from the Ehmaniella Zone (upper Wuliuan Stage) in western Laurentia and from strata slightly below the base of the Drumian Stage in western Hunan Province, South China.

The impact of climate change on biodiversity has been the focus of studies on the Phanerozoic biotic crises. However, it is still controversial whether climate change has caused the Frasnian–Famennian (F–F) biotic crisis since there is no unequivocal view on the global climate change during this critical period. In order to reconstruct palaeotemperatures during the F–F transition in South China (eastern Palaeotethys), a high-resolution oxygen isotope (δ¹⁸OPO4) record was obtained based on 104 measurements of conodont apatite from the Yangdi section. The oxygen isotope record based on mono-generic samples reveals an increase in δ¹⁸OPO4 by 0.7‰ in the Lower Kellwasser horizon (LKH) and 1.4‰ in the Upper Kellwasser horizon (UKH), translating into low-latitude surface water cooling of ∼3 °C and ∼6 °C, respectively. These two δ¹⁸OPO4 shifts agree well with the time-equivalent δ¹⁸OPO4 records from the western Palaeotethys, suggesting that two climate cooling pulses in conjunction with the deposition of the Kellwasser horizons are a global signal during the F–F transition. The positive shift of δ¹⁸OPO4 coincides with positive excursion in carbon isotope of carbonates (δ¹³Ccarb) in the UKH, indicating that enhanced burial of organic carbon resulted in a drop in atmospheric pCO2 and thus global climate cooling. Cooling started immediately before the Upper Kellwasser biotic crisis, with the lowest temperature documented at the top of the UKH. Climate cooling during the deposition of the LKH is observed in conjunction with the sharp decline in metazoan reefs. The coincidence of cooling and the Kellwasser biotic crisis suggests that global cooling played a major role in the collapse of ecosystems.

The Famennian (Late Devonian) started after and ended with two of the seven largest crises of the Phanerozoic, the Kellwasser and Hangenberg events, respectively. In between, global environmental trends have been identified, involving cooling and eustatic regression. Tropical and subtropical marine faunas were largely cosmopolitan. Overall, this suggests that the Famennian was marked by long-term environmental changes occurring in a relatively homogeneous manner despite being punctuated by several short-term events of limited faunal impact. How these trends were modulated according to geographic location is investigated in this study by comparing two continuous outcrops in the Montagne Noire (Col des Tribes section, France) and in Saxo-Thuringia (Buschteich section, Germany). Both were located in the subtropical area during this period and belonged to two former microcontinents bracketed between the closing Rheic Ocean and Gondwana. Sedimentary facies, oxygen isotopes, and the generic conodont composition (biofacies) were studied in a high resolution and in the same rock samples. Sedimentary facies provided an estimate of water depth and oxygen isotopes were used as paleotemperature proxy. Conodont biofacies were analyzed using a principal component analysis, allowing the expression of the variations in the two outcrops on the same axes, and a quantitative comparison with the other proxies. Sea-level and temperature variations were different between the two areas. Saxo-Thuringia displayed stable deep and warm conditions throughout. In contrast, the environment of the Montagne Noire was shallower and cooler during the Late and latest Famennian compared to the Early and Middle Famennian, congruent with the global change evidenced elsewhere. The location of Saxo-Thuringia, close to the first point of closure of the Rheic Ocean, might have favored active tectonics, causing a local departure from the eustatic trend. The stable temperatures at BU during the Late and latest Famennian may be due to the position of Saxo-Thuringia in the remnant Rheic Ocean, limiting water mass exchange with open seas, and favoring the persistence of warm conditions. Offshore taxa persisted later at high abundance in the Saxo-Thuringian record. The two conodont biofacies records were otherwise very comparable. This suggests that other factors mitigated the water depth forcing on these conodont assemblages.

We evaluate the potential of ophiolites as archives of paleoseawater and hydrothermal fluid compositions by analysing the chemical and isotopic composition of abiogenic carbonates, precipitated from fluids within the oceanic crust of the 91 Ma Troodos Ophiolite, Cyprus. Calculated variations in fluid Mg/Ca, Sr/Ca and ⁸⁷Sr/⁸⁶Sr with temperature within the upper sections of the ophiolite are similar to those from drilled oceanic crust, and yield literature values for late Cretaceous seawater Mg/Ca, Sr/Ca and ⁸⁷Sr/⁸⁶Sr. This indicates that carbonates from ophiolites could be used to estimate the composition of ancient seawater at times before the age of the oldest preserved in-situ oceanic crust. Whereas most carbonates recovered from in-situ oceanic crust were precipitated at temperatures <60 °C, abiogenic carbonates from the Troodos Ophiolite formed over a temperature range of 7 °C to 218 °C. These provide unique insights into the chemical and mineralogical processes that transform seawater into a high temperature hydrothermal fluid within the oceanic crust. We use ‘hydrothermal variation diagrams’ of Mg/Ca, Sr/Ca, ⁸⁷Sr/⁸⁶Sr and δ44/40Ca versus calculated temperature (δ¹⁸O) to trace this fluid evolution within the Troodos oceanic crust. We find that successive fluid-crust-interaction, the precipitation of Mg- and Ca-bearing minerals and the early formation of anhydrite (>44 °C) gradually transform Cretaceous seawater into a Troodos hydrothermal fluid. Comparison of the Troodos data with a global dataset of abiogenic carbonates from in-situ oceanic crust shows that the chemical pathways of low-temperature fluid evolution are similar for all Cretaceous sites. These different sites represent varied geotectonic settings (mid-ocean ridge vs. suprasubduction zone), with different basement composition (basalt, basaltic andesite/boninite) and situated in different ocean basins (Atlantic, Pacific, Mediterranean [Tethys]). The similarity in the carbonate record indicates that these differences do not significantly influence seafloor weathering and hydrothermal alteration at low temperatures. However, abiogenic carbonates from younger oceanic crust differ from the Cretaceous trends and follow different fluid evolution pathways. This indicates, that temporal variations in the composition of seawater may control the nature and the extent of seafloor weathering and hydrothermal alteration at low temperatures. A thermodynamic model of fluid-crust interaction, in which modern and Cretaceous seawater are heated to 200 °C while an average Troodos basaltic andesite is successively added under otherwise identical conditions predicts that fluid evolution and alteration of the oceanic crust were different in the Cretaceous than they are today, and that initial seawater chemistry affects the nature and the extent of seafloor alteration up to moderate fluid temperatures. For example, twice the amount of carbonate formed during alteration of the oceanic crust in the Cretaceous compared to modern times, indicating that the flux of CO2 from the hydrosphere-atmosphere system into the oceanic crust was greater in the Cretaceous than it is nowadays, and that it probably varied throughout geologic time.

The Grönhögen-2015 core drilling on southern Öland, Sweden, penetrated 50.15 m of Cambrian Series 3, Furongian and Lower–Middle Ordovician strata. The Cambrian succession includes the Äleklinta Member (upper Stage 5) of the Borgholm Formation and the Alum Shale Formation (Guzhangian–Tremadocian). Agnostoids and trilobites allowed subdivision of the succession into eight biozones, in ascending order: the uppermost Cambrian Series 3 (Guzhangian) Agnostus pisiformis Zone and the Furongian Olenus gibbosus , O. truncatus , Parabolina spinulosa , Sphaerophthalmus ? flagellifer , Ctenopyge tumida , C. linnarssoni and Parabolina lobata zones. Conspicuous lithologic unconformities and the biostratigraphy show that the succession is incomplete and that there are several substantial gaps of variable magnitudes. Carbon isotope analyses (δ ¹³ C org ) through the Alum Shale Formation revealed two globally significant excursions: the Steptoean Positive Carbon Isotope Excursion (SPICE) in the lower–middle Paibian Stage, and the negative Top of Cambrian Excursion (TOCE), previously referred to as the HERB Event, in Stage 10. The δ ¹³ C org chemostratigraphy is tied directly to the biostratigraphy and used for an improved integration of these excursions with the standard agnostoid and trilobite zonation of Scandinavia. Their relations to that of coeval successions in Baltoscandia and elsewhere are discussed. The maximum amplitudes of the SPICE and TOCE in the Grönhögen succession are comparable to those recorded in drill cores retrieved from Scania, southern Sweden. The results of this study will be useful for assessing biostratigraphic relations between shale successions and carbonate facies on a global scale.

A recent core drilling in the geologically classical Fågelsång area resulted in a 58.70-m-long drill core through the lowermost Sandbian Sularp Shale, the Darriwilian Almelund Shale and Komstad Limestone, and part of the late Tremadocian to earliest Darriwilian Tøyen Shale. The shales contain zone index graptolites that are used for an update of the standard Darriwilian graptolite zone succession in Baltoscandia in which six zones are now recognized. The Komstad Limestone interval and lowermost part of the Almelund Shale have been subdivided into four conodont zones. The δ¹³Corg chemostratigraphy, which has been established through the entire drill core based on 120 closely spaced samples, shows a somewhat subdued development of the middle Darriwilian Isotope Carbon Excursion (MDICE), which is dated in terms of graptolite biostratigraphy. The Fågelsång isotope curve is correlated with a closely similar δ¹³Ccarb curve from a coeval, apparently stratigraphically essentially continuous, succession at Kårgärde in south-central Sweden, which previously has been subdivided into 13 conodont zones and subzones. For the first time, these conodont zonal units can be calibrated with Fågelsång graptolite zones using δ¹³Corg chemostratigraphy. The several new results of this study are expected to be useful for assessing biostratigraphic relations between units in shale and carbonate facies in Baltoscandia and elsewhere in the world.

The Cristal Zn prospect consists of a mixed sulfide and nonsulfide mineralization located in the Bongará province (Amazonas region, northern Peru). The mineralization is hosted by carbonate rocks of the Pucará Group, deposited in a Mesozoic extensional basin on the western margin of the Brazilian-Guyana shield. Zinc sulfides at Cristal occur in the roots of the nonsulfide concentrations, and are locally present also nearer to surface. The sulfide mineralization postdates two hydrothermal dolomitization phases (Dol1 and Dol2) and the sulfides occur mainly in veins, cavity fillings or as disseminated mineralization, within sparry to saddle dolomite. They mostly consist of dark-brown sphalerite, intergrown with smaller amounts of pyrite. Sphalerite shows a distinct Fe-zonation, with average ca. 7 wt% Fe (max. ca. 12 wt% Fe), and is Ge-rich (mean concentration of 142 ppm). Galena is rare. The Cristal sphalerite has sulfur isotopic compositions of δ³⁴S = 14 to 15 ‰ VCDT. Oxygen isotopic compositions of dolomites are: δ¹⁸O = 24.4 to 24.7 ‰ VSMOW for Dol1 and 18.4 to 22 ‰ for Dol2. δ³⁴S and δ¹⁸O values of Cristal sulfides and dolomites are similar to those observed in two Mississippi Valley-type (MVT) deposits located ca. 20–30 km south of the Cristal prospect, namely the Florida Canyon and Florcita deposits. This could be consistent with one or more events within a same MVT mineralizing system, acting at the district scale. The Pb isotope compositions of sphalerite from two different areas of the prospect (named Cristal s.s. and Charlita North) define two distinct data-point clusters (centered around averages of ²⁰⁶Pb/²⁰⁴Pb = 18.850 ± 0.002, ²⁰⁷Pb/²⁰⁴Pb = 15.685 ± 0.002, ²⁰⁸Pb/²⁰⁴Pb = 38.752 ± 0.004, and ²⁰⁶Pb/²⁰⁴Pb = 19.042 ± 0.002, ²⁰⁷Pb/²⁰⁴Pb = 15.712 ± 0.002, ²⁰⁸Pb/²⁰⁴Pb = 39.080 ± 0.004, respectively). This difference requires distinct metal-bearing hydrothermal pulses in the mineralized area and/or distinct Pb sources. The Pb isotopic compositions of the Cristal s.s. and Charlita North sulfides are intermediate between the compositions of galena from the San Vicente and Shalipayco MVT deposits, and record a contribution from an old crustal component. The Paleozoic basement, which has Pb isotopic ratios roughly matching those of dolomites and sulfides from Cristal and Charlita North areas, represents the most reliable candidate to be an end-member source of the metals of the Cristal sulfide mineralization. The second end-member could be an igneous source, isotopically identical to the Late Paleozoic to Early Mesozoic intrusives of the Peruvian Eastern Cordillera, or the Triassic volcanic rocks occurring within the Mitu Group.

The Komstad Limestone forms a distal part of the widespread ‘orthoceratite limestone’ of the Baltoscandian continent. In this paper, we present an integrated conodont biostratigraphy and carbon isotope stratigraphy for a major part of this formation and address its significance for evaluating Middle Ordovician correlation and overall stratigraphy. Four conodont zones are distinguished, including the Lenodus antivariabilis Zone, Lenodus variabilis Zone, the Yangtzeplacognathus crassus Zone, and the Eoplacognathus pseudoplanus Zone. Carbon isotopes have previously not been published from the Komstad Limestone. The data herein show that carbonate strata may retain a comprehensive pristine δ¹³C signal despite relatively strong thermal influence during diagenesis (Conodont Color Alteration Index 4–5).

We present a multi-proxy study of an upper Paleocene-lower Eocene succession from the paleo-equatorial region. The study is carried out on a coal-bearing, shallow-marine succession exposed at Jathang, east Khasi hills, Meghalaya, northeastern India. The succession was deposited in a low-energy, coastal marsh-bay complex. Dinoflagellate cyst biostratigraphy yields a late Paleocene to early Eocene age for the section. The deposits of the lower part of the succession represent a transgressive systems tract (TST) defined by seven parasequences, each starting with bay sediments deposited during transgression, followed by a shallowing-upward bay fill-marsh deposit. In the vertical succession, each parasequence acquires an increasingly marine character, culminating in a maximum flooding surface at the Paleocene-Eocene boundary. It is followed by four shallowing upward parasequences deposited in a highstand systems tract (HST). Enhanced chemical weathering and high terrestrial supply are testified by raised SiO2 and Al2O3 contents and high percentages of terrestrial palynomorphs. The pollen flora recovered from the Jathang section was used for quantitative paleoclimate and vegetation reconstructions. The Coexistence Approach was applied based on Nearest Living Relatives (NLRs) of sixty fossil species recorded at different stratigraphic levels. Seven climate variables were determined for the fossil assemblages, and, as a measure of the seasonality of climate, the number of dry months was estimated. Our study shows that during the Paleocene there existed warm, seasonally dry tropical climate conditions with mean annual temperature at ca. 24–26 °C and mean annual precipitation at ca. 700–1800 mm, and with a dry season of 5–6 months. Particularly warm and wet, perhumid climate conditions with 26–27 °C and 2200–3200 mm mean annual precipitation with a dry period of 2–3 months were reconstructed for the latest Paleocene-earliest Eocene interval. The study shows a distinct vegetational turnover from palm-dominated, seasonally dry tropical forest during the Paleocene to highly diversified dicotyledonous megathermal rainforest during the latest Paleocene-early Eocene. The present study demonstrates that the reduced duration of the dry period during the latest Paleocene-earliest Eocene, due to a more active hydrological cycle, played a major role in determining the climate and shaping the vegetation cover in the paleo-equatorial region. There is evidence from our data that seasonality of rainfall is the determining factor for the tropical forest vegetation pattern of the equatorial region rather than mean annual rainfall condition. As the main trigger for the observed step-wise changes of the hydrology along the studied succession, the fast northward movement of the Indian Plate is inferred.

A preliminary C–O stable isotopes geochemical characterization of several nonsulfide Zn-Pb Tunisian deposits has been carried out, in order to evidence the possible differences in their genesis. Nonsulfide ores were sampled from the following deposits: Ain Allegua, Jebel Ben Amara, Jebel Hallouf (Nappe Zone), Djebba, Bou Grine, Bou Jaber, Fedj el Adoum, Slata Fer (Diapir Zone), Jebel Ressas, Jebel Azreg, Mecella (North South Axis Zone), Jebel Trozza, Sekarna (Graben Zone). After mineralogical investigation of selected specimens, the C–O stable isotopic study was carried out on smithsonite, hydrozincite, cerussite and calcite. The data have shown that all the carbonate generations in the oxidized zones of Ain Allegua and Jebel Ben Amara (Nappe Zone), Bou Jaber, Bou Grine and Fedj el Adoum (Diapir Zone), Mecella and Jebel Azreg (North South Zone) have a supergene origin, whereas the carbonates sampled at Sekarna (Graben Zone) (and in limited part also at Bou Jaber) precipitated from thermal waters at moderately high temperature. Most weathering processes that controlled the supergene alteration of the Zn-Pb sulfide deposits in Tunisia had probably started in the middle to late Miocene interval and at the beginning of the Pliocene, both periods corresponding to two distinct tectonic pulses that produced the exhumation of sulfide ores, but the alteration and formation of oxidized minerals could have also continued through the Quaternary. The isotopic characteristics associated with the weathering processes in the sampled localities were controlled by the different locations of the sulfide protores within the tectonic and climatic zones of Tunisia during the late Tertiary and Quaternary.

The Verkhnyaya Kardailovka section is one of the best candidates for the GSSP (Global Stratotype Section and Point) at the base of the Stage (Mississippian). For boundary definition, the first appearance of the conodont Lochriea ziegleri Nemirovskaya, Perret et Meischner, 1994 in the lineage Lochriea nodosa (Bischoff, 1957)−L. ziegleri is used. L. ziegleri appears in the Venevian Substage somewhat below the base of the Serpukhovian in the Moscow Basin. The position of the FAD of L. ziegleri within the Hypergoniatites−Ferganoceras Genozone is confirmed and lies between 19.53 and 19.63 m above the section’s base. Before 2010, deep-water stylonodular limestone containing the boundary in unnamed formation C at Kardailovka was well exposed but only 3 m of Viséan strata cropped out immediately below. Recent trenching exposed another 10 m of underlying Viséan carbonates in formation C and older Viséan siliciclastics and volcanics in unnamed formation B. The contact between formation B and underlying crinoidal limestones in unnamed formation A representing the middle Viséan Zhukovian (Tulian) regional Substage was excavated. The boundary succession, situated in the Magnitogorsk tectonic zone above the Devonian Magnitogorsk arc and Mississippian magmatic and sedimentary rift succession, was deposited west of the Kazakhstanian continent during closure of the Ural Ocean. In the lower part of the section, Viséan tuffaceous siliciclastics and volcanics of formation B record rapid deepening after deposition of neritic middle Viséan crinoid lime grainstone of formation A and subsequent subaerial exposure. The overlying condensed upper Viséan to Serpukhovian succession in formation C comprises deep-water limestone deposited in a sediment-starved basin recording minor turbidite influx and carbonate-mound development. The δ¹³Ccarb plot shows a positive shift of 1‰ V-PDB (from +2 to +3‰) between 17.0 and 17.75 m (3.05 and 1.97 m below FAD L. ziegleri). The δ¹⁸Oapatite graph displays a prominent upward shift from 19.9 to 21.1‰ V-SMOW (at 19.15 to 19.51 m) in the nodosa Zone below FAD of Lochriea ziegleri.

Biogenic minerals such as dental apatite have become commonly analysed archives preserving geochemical indicators of past environmental conditions and palaeoecologies. However, post-mortem, biogenic minerals are modified due to the alteration/replacement of labile components, and recent moves to utilise micro-mammal tooth d18O signatures for refined Cenozoic terrestrial palaeoclimate reconstructions has lacked consideration of the chemical effects of predator digestion. Here, the physical and chemical condition of laboratory-raised mouse (Mus musculus) teeth have been investigated in conjunction with their bulk phosphate and tissue-specific d18O values prior, and subsequent, to ingestion and excretion by various predator species (owls, mammals and a reptile). Substantial variability (up to 2‰) in the d18O values of both undigested teeth and those ingested by specific predators suggests significant natural heterogeneity of individual prey d18O. Statistically distinct, lower d18O values (~0.7‰) are apparent in teeth ingested by barn owls compared to undigested controls as a result of the chemically and enzymatically active digestive and waste-pellet environments. Overall, dentine tissues preserve lower d18O values than enamel, while the greatest modification of oxygen isotope signals is exhibited in the basal enamel of ingested teeth as a result of its incompletely mineralised state. However, recognition of 18O-depletion in chemically purified phosphate analyses demonstrates that modification of original d18O values is not restricted to labile oxygen-bearing carbonate and organic phases. The style and magnitude of digestive-alteration varies with predator species and no correlation was identified between specific physical or minor/trace-element (patterns or concentrations) modification of ingested teeth and disruption of their primary oxygen isotope values. Therefore, there is a current lack of any screening tool for oxygen isotope disruption as a result of predation. These results point to the need for careful application of the micro-mammal oxygen isotope palaeoenvironmental proxy in future studies.

Zinc nonsulfides are well represented in the Middle East, with occurrences in Turkey, Iran, and Yemen. Their genesis can be constrained by using carbon and oxygen isotope systematics applied to carbonate minerals. The δ13C ratios of smithsonite and hydrozincite in Iran and Turkey are comprised in the typical interval of supergene Zn carbonates (−0.4 and −7.1‰ V-PDB). The oxygen isotope geochemistry is more complex. Oxygen isotope compositions of smithsonite of the Hakkari deposit (Turkey) (δ18O from 24.2 to 25.6‰ V-SMOW) point to precipitation temperatures between ~4 and ~18 °C, corresponding to a normal weathering environment at these latitudes, whereas δ18O of smithsonite from other Middle East deposits (Angouran in Iran, Jabali in Yemen) point to the precipitation from low- to medium-temperature hydrothermal fluids. The C–O isotopic compositions of hydrozincite from the Mehdi Abad, Irankuh, and Chah-Talkh deposits can be only partially compared with those of smithsonite, because the oxygen isotopes fractionation equation for hydrozincite-water is not known. A comparison between the geochemical characteristics of all Zn-nonsulfide ores in the Middle East indicates that, even though several mineral deposits are derived from supergene weathering processes, other ones have been deposited from fluids associated with magmatic activity (Angouran, Iran) or with hydrothermal systems (Jabali, Yemen). This suggests that it is not possible to apply a common interpretative model to the genesis of all nonsulfide deposits in the Middle East.

The Cristal Zn prospect is located in the northernmost part of a wide mining district corresponding to the “Charlotte Bongará Zinc Project”, which covers an area of approximately 110 km² in the Amazonas district in northern Peru. The mineralized area consists of many Zn occurrences that contain mixed sulfide and nonsulfide mineralizations. The nonsulfide ores are interpreted to be the product of weathering of primary MVT sulfide bodies. The Zn concentrations of the Cristal prospect are hosted by platform carbonates of the Condorsinga Formation (Early Jurassic), which belongs to the Pucará Group. The prospect extends over an area of approximately 2 x 1 km, with nearly continuous zones of Zn enrichment that has been detected in soil and rock samples. The nonsulfide mineralization consists mainly of semi-amorphous orange to brown zinc “oxides” that include hemimorphite, smithsonite and Fe-(hydr)oxides. The most important mineralized areas are the Esperanza and Yolanda occurrences, which were also most intensively explored. In both occurrences, the supergene Zn-carbonates and silicates infill solution cavities, or replace the carbonate host rocks and/or the primary sulfides, forming smithsonite- and hemimorphite-rich mineralizations. The analyzed drill core samples have on average 20 wt.% Zn and maximum Ge concentrations of 200 ppm. The Bongará area experienced a prolonged phase of weathering from Miocene to Recent under tropical climatic conditions. In these conditions, the weathering processes affected many pre-existing sulfide deposits (e.g. Cristal, Florida Canyon, Mina Grande), where supergene profiles were developed under locally different settings that are defined primarily on the basis of mineralogical and geochemical data. Contrary to the Mina Grande deposit, at Cristal, the development of a karst network was minor due to limited uplift, and supergene alteration did not completely obliterate the roots of the original sulfide orebody. The mineralogy and geochemistry of Bongará nonsulfides is dependent on two main factors at the local scale: (1) uplift rates, and (2) host rock composition. The latter may have favored the development of more (e.g. Mina Grande) or less (e.g. Cristal) alkaline supergene environments. Uplift was controlled by the activity of local faults, which allowed the exposure of sulfide protores at variable elevations in different periods of time and hydrological settings. Such different settings resulted in the precipitation of isotopically different supergene carbonates (e.g. smithsonites and calcites at Mina Grande and Cristal).

The Mina Grande zinc nonsulfide deposit (Amazonas region, Peru) consists of several accumulations in karst cavities of Zn oxide minerals, derived from weathering of a Mississippi Valley-type deposit hosted in Mesozoic carbonate rocks of the Condorsinga Formation (Pucará Group). The karst cavities hosting the nonsulfide ores were developed in the Miocene along northwest-southeast faults (avg 230° dip, 70° dip angle) associated with regional structures, and locally along stratification joints (avg 8° strike, 278° dip, and 26° dip angle). Thus far, the Mina Grande Zn accumulations have been partially mined in two pits (named "Fase A" and "Fase B") and explored in a third area, named "Fase C." In 2008, the resources were as follows: Fase A = 160,000 metric tons (t) @ 21.2% Zn, Fase B = 36,400 t @ 28.9% Zn, and Fase C = 116,700 t @ 22.5% Zn. The nonsulfide mineral assemblage, consisting mostly of hydrozincite, smithsonite, and hemimorphite, is associated with few remnants of the hypogene ore (pyrite and sphalerite). Mineralogical and petrographic studies revealed several texturally distinct smithsonite and hydrozincite generations, which are characterized by extremely negative δ13C compositions, pointing to the prevailing contribution of an isotopically light carbon component from the oxidation of organic matter-derived carbon, and different δ18O isotope compositions: 26.9 to 27.2 and 26.0 to 26.3% δ18O VSMOW for smithsonite, and averages 24.6 and 23.7% δ18O VSMOW for hydrozincite. These distinct δ18O compositions indicate that smithsonite and hydrozincite precipitated at least after two depositional stages. These stages were probably related to several periods of uplift that occurred in the Bongará district since at least ∼10 Ma, when the transition from the Pebas to Acre systems affected the Amazonas foreland basin in the Miocene. The karst activity, to which the supergene mineralization is related, was restricted to the late Miocene and early Pliocene periods. Climatic conditions reconstructed from the ecosystems persisting in the region from Late Tertiary to Recent time suggest that the Mina Grande supergene mineralization was associated with several weathering episodes that occurred under a climate resembling the present-day climatic conditions.

The Central European Basin is very suitable for high-resolution multistratigraphy of Late Permian to Early Triassic continental deposits. Here the well exposed continuous transition of the lithostratigraphic Zechstein and Buntsandstein Groups of Central Germany was studied for isotope-chemostratigraphy (δ¹³Corg, δ¹³Ccarb, δ¹⁸Ocarb), major and trace element geochemistry, magnetostratigraphy, palynology, and conchostracan biostratigraphy. The analysed material was obtained from both classical key sections (abandoned Nelben clay pit, Caaschwitz quarries, Thale railway cut, abandoned Heinebach clay pit) and a recent drill core section (Caaschwitz 6/2012) spanning the Permian-Triassic boundary. The Zechstein–Buntsandstein transition of Central Germany consists of a complex sedimentary facies comprising sabkha, playa lake, aeolian, and fluvial deposits of predominantly red-coloured siliciclastics and intercalations of lacustrine oolitic limestones. The new data on δ¹³Corg range from − 28.7 to − 21.7 ‰ showing multiple excursions. Most prominent negative shifts correlate with intercalations of oolites and grey-coloured clayey siltstones, while higher δ¹³Corg values correspond to an onset of palaeosol overprint. The δ¹³Ccarb values range from − 9.7 to − 1.3 ‰ with largest variations recorded in dolomitic nodules from the Zechstein Group. In contrast to sedimentary facies shifts across the Zechstein-Buntsandstein boundary, major element values used as a proxy (CIA, CIA*, CIA-K) for weathering conditions indicate climatic stability. Trace element data used for a geochemical characterization of the Late Permian to Early Triassic transition in Central Germany indicate a decrease in Rb contents at the Zechstein-Buntsandstein boundary.

The Central European Basin is very suitable for high-resolution multistratigraphy of Late Permian to Early Triassic continental deposits. Here the well exposed continuous transition of the lithostratigraphic Zechstein and Buntsandstein Groups of Central Germany was studied for isotope-chemostratigraphy (δ13Corg, δ13Ccarb, δ18Ocarb), major and trace element geochemistry, magnetostratigraphy, palynology, and conchostracan biostratigraphy. The analysed material was obtained from both classical key sections (abandoned Nelben clay pit, Caaschwitz quarries, Thale railway cut, abandoned Heinebach clay pit) and a recent drill core section (Caaschwitz 6/2012) spanning the Permian-Triassic boundary. The Zechstein–Buntsandstein transition of Central Germany consists of a complex sedimentary facies comprising sabkha, playa lake, aeolian, and fluvial deposits of predominantly red-coloured siliciclastics and intercalations of lacustrine oolitic limestones. The new data on δ13Corg range from − 28.7 to − 21.7 ‰ showing multiple excursions. Most prominent negative shifts correlate with intercalations of oolites and grey-coloured clayey siltstones, while higher δ13Corg values correspond to an onset of palaeosol overprint. The δ13Ccarb values range from − 9.7 to − 1.3‰with largest variations recorded in dolomitic nodules from the Zechstein Group. In contrast to sedimentary facies shifts across the Zechstein-Buntsandstein boundary, major element values used as a proxy (CIA, CIA*, CIA-K) for weathering conditions indicate climatic stability. Trace element data used for a geochemical characterization of the Late Permian to Early Triassic transition in Central Germany indicate a decrease in Rb contents at the Zechstein-Buntsandstein boundary. New palynological data obtained from the Caaschwitz quarry section reveal occurrences of Late Permian palynomorphs in the Lower Fulda Formation, while Early Triassic elements were recorded in the upper part of the Upper Fulda Formation. The present study confirms an onset of a normal-polarized magnetozone in the Upper Fulda Formation of the Caaschwitz quarry section supporting an interregional correlation of this crucial stratigraphic interval with the normal magnetic polarity of the basal Early Triassic known from marine sections in other regions. Based on a synthesis of the multistratigraphic data, the Permian-Triassic boundary is proposed to be placed in the lower part of the Upper Fulda Formation, which is biostratigraphically confirmed by the first occurrence date of the Early Triassic Euestheria gutta-Palaeolimnadiopsis vilujensis conchostracan fauna. Rare records of conchostracans reported from the siliciclastic deposits of the lower to middle Zechstein Group may point to its potential for further biostratigraphic subdivision of the Late Permian continental deposits.

The Central European Basin is very suitable for high-resolution multistratigraphy of Late Permian to Early Triassic continental deposits. Here the well exposed continuous transition of the lithostratigraphic Zechstein and Buntsandstein Groups of Central Germany was studied for isotope-chemostratigraphy (δ13Corg, δ13Ccarb, δ18Ocarb), major and trace element geochemistry, magnetostratigraphy, palynology, and conchostracan biostratigraphy. The analysed material was obtained from both classical key sections (abandoned Nelben clay pit, Caaschwitz quarries, Thale railway cut, abandoned Heinebach clay pit) and a recent drill core section (Caaschwitz 6/2012) spanning the Permian-Triassic boundary. The Zechstein–Buntsandstein transition of Central Germany consists of a complex sedimentary facies comprising sabkha, playa lake, aeolian, and fluvial deposits of predominantly red-coloured siliciclastics and intercalations of lacustrine oolitic limestones. The new data on δ13Corg range from −28.7 to −21.7‰ showing multiple excursions. Most prominent negative shifts correlate with intercalations of oolites and grey-coloured clayey siltstones, while higher δ13Corg values correspond to an onset of palaeosol overprint. The δ13Ccarb values range from −9.7 to −1.3 ‰ with largest variations recorded in dolomitic nodules from the Zechstein Group. In contrast to sedimentary facies shifts across the Zechstein-Buntsandstein boundary, major element values used as a proxy (CIA, CIA*, CIA-K) for weathering conditions indicate climatic stability. Trace element data used for a geochemical characterization of the Late Permian to Early Triassic transition in Central Germany indicate a decrease in Rb contents at the Zechstein-Buntsandstein boundary. New palynological data obtained from the Caaschwitz quarry section reveal occurrences of Late Permian palynomorphs in the Lower Fulda Formation, while Early Triassic elements were recorded in the upper part of the Upper Fulda Formation. The present study confirms an onset of a normal-polarized magnetozone in the Upper Fulda Formation of the Caaschwitz quarry section supporting an interregional correlation of this crucial stratigraphic interval with the normal magnetic polarity of the basal Early Triassic known from marine sections in other regions. Based on a synthesis of the multistratigraphic data, the Permian-Triassic boundary is proposed to be placed in the lower part of the Upper Fulda Formation, which is biostratigraphically confirmed by the first occurrence date of the Early Triassic Euestheria gutta-Palaeolimnadiopsis vilujensis conchostracan fauna. Rare records of conchostracans reported from the siliciclastic deposits of the lower to middle Zechstein Group may point to its potential for further biostratigraphic subdivision of the Late Permian continental deposits.

The subdivision of Ladinian and Carnian strata in Guizhou, South China has been a matter of intense debate because of the paucity of age-diagnostic faunas. Here we have carried out a detailed conodont biostratigraphic investigation on the Yangliujing, Zhuganpo and Wayao formations in the Yongyue section of western Guizhou Province. Conodonts are only prolific in the Zhuganpo and Wayao formations. Three genera and twenty species are identified, including two new species Quadralella wanlanensis n. sp. and Quadralella yongyueensis n. sp. They represent a rather endemic fauna of latest Ladinian to early Carnian age. Four conodont zones are established. They are, in the ascending order, the Paragondolella foliata, Quadralella polygnathiformis, Quadralella tadpole, and Quadralella aff. praelindae zones. Thus in the study area, the Zhuganpo Formation is generally of early Carnian (Julian 1) age whilst the Wayao Formation probably extends from the Julian 2 into the late Carnian (Tuvalian substage). The Ladinian–Carnian boundary (LCB) cannot be precisely defined due to the absence of the ammonoid Daxatina Canadensis and the paucity of conodonts. However, the LCB is unlikely lower than the Yangliujing–Zhuganpo formation contact. The Julian 1–Julian 2 (early Carnian) substages boundary is defined in the uppermost Zhuganpo Formation by the occurrence of basal Julian 2 ammonoid Austrotrachyceras ex gr. A. austriacum and is also evidenced by the disappearance of most short-range Julian 1 conodonts in the overlying Wayao Formation.

This study characterizes the stratigraphical context as well as the palaeoenvironmental and sea-level trends during the Late Frasnian and Famennian in the Buschteich section (Thuringia, Germany). An integrated approach combines conodont biostratigraphy, chemostratigraphy based on carbon and oxygen isotopes , conodont biofacies analyses and investigations of the morphotypes of foraminifera that occur in the section was applied. Conodonts provided a fine-scale biostratigraphical framework. All the Famennian con-odont biozones were identified, with the exception of the three lowest. The Frasnian–Famennian transition was further identified by a positive carbon isotope excursion. This continuous Famennian record is developed in a condensed limestone succession. The reddish Griotte facies, typical of strata of this period, were not documented. Black shales were not developed except for an interval of dark colored mud rocks corresponding to the Hangenberg event at the top of the section. The carbonate succession of Buschteich was deposited in an outer ramp environment, pelagic organisms are the dominant fauna. This is corroborated by the overall dominance of the deep-water conodont genus Palmatolepis. Microfacies, conodont biofacies and foramini-fera indicated a deepening trend from the Lower crepida to the Lower rhomboidea Zone, followed by a shal-lowing trend from the Upper rhomboidea to the praesulcata Zone. This sequence overall matches the sea level reference curve for Euramerica. The timing of maximum water depth at Buschteich, as well as the general sea-level reference record, differs from the Col des Tribes (Montagne Noire, France). Differential uplift or overprinting of the long-term eustatic changes may be the cause of the discrepancy in the local sea-level records.

Conodont biogenic apatite has become a preferred analytical target for oxygen isotope studies investigating ocean temperature and palaeoclimate changes in the Palaeozoic. Despite the growing application in geochemically-based palaeoenvironmental reconstructions, the paucity or absence of conodont fossils in certain facies necessitates greater flexibility in selection of robust oxygen-bearing compounds for analysis. Vertebrate microfossils (teeth, dermal denticles, spines) offer a potential substitute for conodonts from the middle Palaeozoic. Vertebrate bioapatite is particularly advantageous given a fossil record extending to the present with representatives across freshwater to fully marine environments, thus widening the scope of oxygen isotope studies on bioapatite. However, significant tissue heterogeneity within vertebrates and differential susceptibility of these tissues to diagenetic alteration have been raised as potential problems affecting the reliability of the oxygen isotope ratios as palaeoclimatic proxies. Well-preserved vertebrate microfossils and co-occurring conodont fossils from the Upper Devonian and Lower Carboniferous of the Lennard Shelf, Canning Basin, Western Australia, were analysed using bulk (gas isotope ratio mass spectrometry, GIRMS) and in-situ (secondary ion mass spectrometry, SIMS) methodologies, with the latter technique allowing investigation of specific tissues within vertebrate elements. The δ¹⁸Oconodont results may be interpreted in terms of palaeolatitudinally and environmentally sensible palaeo-salinity and -temperature and provide a baseline standard for comparison against vertebrate microfossil δ¹⁸O values. Despite an absence of obvious diagenetic modification, GIRMS of vertebrate denticles yielded δ¹⁸O values depleted in ¹⁸O by 2–4‰ relative to co-occurring conodonts. SIMS analysis of dentine tissues exhibited significant heterogeneity, while hypermineralised tissues in both scales and teeth produced δ¹⁸O values comparable with those of associated conodonts. The susceptibility of permeable phosphatic fossil tissues to microbial activity, fluid interaction and introduction of mineral precipitates post-formation is demonstrated in the dentine of vertebrate microfossils, which showed significant heterogeneity and consistent depletion in ¹⁸O relative to conodonts. The hypermineralised tissues present in both teeth and scales appear resistant to many diagenetic processes and indicate potential for palaeoclimatic reconstructions and palaeoecological investigations.

Permian strata from the Tieqiao section (Jiangnan Basin, South China) contain several distinctive conodont assemblages. Early Permian (Cisuralian) assemblages are dominated by the genera Sweetognathus, Pseudosweetognathus and Hindeodus with rare Neostreptognathodus and Gullodus. Gondolellids are absent until the end of the Kungurian stage—in contrast to many parts of the world where gondolellids and Neostreptognathodus are the dominant Kungurian conodonts. A conodont changeover is seen at Tieqiao and coincided with a rise of sea level in the late Kungurian to the early Roadian: the previously dominant sweetognathids were replaced by mesogondolellids. The Middle and Late Permian (Guadalupian and Lopingian Series) witnessed dominance of gondolellids (Jinogondolella and Clarkina), the common presence of Hindeodus and decimation of Sweetognathus.

This study characterizes the stratigraphical context as well as the palaeoenvironmental and sealevel trends during the Late Frasnian and Famennian in the Buschteich section (Thuringia, Germany). An integrated approach combines conodont biostratigraphy, chemostratigraphy based on carbon and oxygen isotopes, conodont biofacies analyses and investigations of the morphotypes of foraminifera that occur in the section was applied. Conodonts provided a fine-scale biostratigraphical framework. All the Famennian conodont biozones were identified, with the exception of the three lowest. The Frasnian – Famennian transition was further identified by a positive carbon isotope excursion. This continuous Famennian record is developed in a condensed limestone succession. The reddish Griotte facies, typical of strata of this period, were not documented. Black shales were not developed except for an interval of dark colored mud rocks corresponding to the Hangenberg event at the top of the section. The carbonate succession of Buschteich was deposited in an outer ramp environment, pelagic organisms are the dominant fauna. This is corroborated by the overall dominance of the deep-water conodont genus Palmatolepis. Microfacies, conodont biofacies and foramini fera indicated a deepening trend from the Lower crepida to the Lower rhomboidea Zone, followed by a shallowing trend from the Upper rhomboidea to the praesulcata Zone. This sequence overall matches the sea level reference curve for Euramerica. The timing of maximum water depth at Buschteich, as well as the general sea-level reference record, differs from the Col des Tribes (Montagne Noire, France). Differential uplift or overprinting of the long-term eustatic changes may be the cause of the discrepancy in the local sea-level records.

Oxygen isotopes were measured on several types of fossil hardparts from the Gault Clay Formation including benthic and planktonic foraminifera, belemnite guards, and fish small-teeth. Belemnites d18O values indicate low temperatures (13.5–19.3°C) with an increase from the Middle to Late Albian. Foraminifera provide variable d18O values, some too low to be relevant in terms of temperature (until 42°C). These low values probably result from a diagenetic alteration of the foraminiferal tests even though SEM observations revealed well-preserved microstructures. However, higher foraminiferal d18O values recorded in some levels indicate temperatures in the range of previously published estimates for the Albian at comparable palaeolatitudes. In these levels, temperatures inferred from benthic and planktonic foraminiferal d18O range between 15–17°C and 27–30°C respectively, during the Middle–Late Albian interval. This slight increase in temperature is coherent with the long-term warming that characterises the Aptian–Cenomanian interval. The temperature difference between sea-surface and bottom waters fits well with a deposition at a palaeodepth of about 180 m in lower offshore environments, assuming a temperature gradient with depth comparable to the modern one in similar epicontinental tropical environments. Fish small-teeth indicate a temperature range from 22 to 28°C consistent with previously published data from planktonic foraminifera, with a greater variability recorded during the late than during middle Albian. This correspondence suggests that small-teeth assemblages may be dominated by pelagic fishes, thus recording upper ocean temperatures. Finally, the markedly lower temperatures recorded by the belemnite guards compared to other analysed materials suggest a necto-benthic mode of life of belemnites

Globally, the Series 2 – Series 3 boundary of the Cambrian System coincides with a major carbon isotope excursion, sea-level changes and trilobite extinctions. Here we examine the sedimentology, sequence stratigraphy and carbon isotope record of this interval in the Cambrian strata (Durness Group) of NW Scotland. Carbonate carbon isotope data from the lower part of the Durness Group (Ghrudaidh Formation) show that the shallow-marine, Laurentian margin carbonates record two linked sea-level and carbon isotopic events. Whilst the carbon isotope excursions are not as pronounced as those expressed elsewhere, correlation with global records (Sauk I – Sauk II boundary and Olenellus biostratigraphic constraint) identifies them as representing the local expression of the ROECE and DICE. The upper part of the ROECE is recorded in the basal Ghrudaidh Formation whilst the DICE is seen around 30m above the base of this unit. Both carbon isotope excursions co-occur with surfaces interpreted to record regressive–transgressive events that produced amalgamated sequence boundaries and ravinement/flooding surfaces overlain by conglomerates of reworked intraclasts. The ROECE has been linked with redlichiid and olenellid trilobite extinctions, but in NW Scotland, Olenellus is found after the negative peak of the carbon isotope excursion but before sequence boundary formation.

Oxygen isotope ratios (δ18O) of biogenic apatite have become a widely used tool for reconstructing palaeoenvironmental conditions in the past. Ongoing improvements in secondary ion mass spectrometry (SIMS) technology have made in situ δ18O analyses on sub-nanogram domains within single microfossil samples possible; however this method requires calibration with reference materials (RMs) with a matrix “similar” to that of the samples. Here we evaluated five sources of gem-quality, abiogenic apatites to assess their potentials as SIMS RMs. Our results show that all these gem-quality apatites are low-REEs calcium fluorapatites with δ18OVSMOW values between 6.6 and 11.4‰. Large variations in δ18O have been found for between crystals from a single deposit as well as within individual crystals. Durango apatite has an inter-crystal δ18O range of 4.4‰ (6.6–11.0‰, N = 9 crystals). Madagascar Green apatite, Madagascar 1st Mine apatite and Ipira apatite have inter-crystal variations in δ18O of 4.1‰ (7.3–11.4‰, N = 15 crystals), 3.5‰ (7.6–11.1‰, N = 9 crystals) and 3.1‰ (7.1–10.2‰, N = 11 crystals), respectively. South Africa Blue apatite has a smaller inter-crystal δ18O range of only 0.9‰ (8.7–9.6‰, N = 6 crystals), though this might be an artefact due to the restricted number of samples studied. Intra-crystal δ18O variations of studied crystals generally range from 0.8 to 1.8‰. However, several gem apatite crystals from Madagascar have minor δ18O variation within 0.5‰ and represent most promising candidate RM.

During the Global Taghanic Biocrisis (c. 385 Ma), Middle Devonian faunas worldwide underwent extinction. In the biocrisis type region, the northern Appalachian Basin, biodiversity changes occurred through three bioevents that ultimately resulted in the loss of numerous endemic taxa. Carbon isotope excursions during this biocrisis have been documented in various stratigraphic successions, but never in the type region. Herein, we reconstruct changes in d 13 C carb from the biocrisis type region and compare these changes to local faunal transitions. An approximately 1.5‰ negative excursion corresponds to the first bioevent, a time of inferred global warming and replacement of most endemic taxa of the mid-palaeolatitude Appalachian Basin by invasive palaeoequatorial taxa. An approximately 2‰ positive excursion is associated with the second bioevent, recognized as a return of the endemic fauna and the loss of invasive taxa. This positive excursion occurs near the Polygnathus ansatus– Ozarkodina semialternans zonal boundary and is recognized elsewhere. Faunal cosmopolitanism associated with the third bioevent corresponds with an inflection in the carbon isotope record from negative to positive trending values, which agrees with a positive carbon record excursion seen elsewhere at the semialternans–Schmidtognathus hermanni zonal boundary. This new carbon isotope record provides an important reference for recognizing this biocrisis in other areas and facies.

The Carnian Humid Episode (CHE), also known as the Carnian Pluvial Event, and associated biotic changes are major enigmas of the Mesozoic record in western Tethys. We show that the CHE also occurred in eastern Tethys (South China), suggestive of a much more widespread and probably global climate perturbation. Oxygen isotope records from conodont apatite indicate a double-pulse warming event. The CHE coincided with an initial warming of 4 °C. This was followed by a transient cooling period and then a prolonged ∼7 °C warming in the later Carnian (Tuvalian 2). Carbon isotope perturbations associated with the CHE of western Tethys occurred contemporaneously in South China, and mark the start of a prolonged period of carbon cycle instability that persisted until the late Carnian. The dry-wet transition during the CHE coincides with the negative carbon isotope excursion and the temperature rise, pointing to an intensification of hydrologic cycle activities due to climatic warming. While carbonate platform shutdown in western Tethys is associated with an influx of siliciclastic sediment, the eastern Tethyan carbonate platforms are overlain by deep-water anoxic facies. The transition from oxygenated to euxinic facies was via a condensed, manganiferous carbonate (MnO content up to 15.1 wt%), that records an intense Mn shuttle operating in the basin. Significant siliciclastic influx in South China only occurred after the CHE climatic changes and was probably due to foreland basin development at the onset of the Indosinian Orogeny. The mid-Carnian biotic crisis thus coincided with several phenomena associated with major extinction events: a carbonate production crisis, climate warming, oscillations, marine anoxia, biotic turnover and flood basalt eruptions (of the Wrangellia Large Igneous Province).

Lower Triassic marine strata in Spitsbergen accumulated on a mid-to-high latitude ramp in which high-energy foreshore and shoreface facies passed offshore into sheet sandstones of probable hyperpycnite origin. More distal facies include siltstones, shales and dolomitic limestones. Carbon isotope chemostratigraphy comparison allows improved age dating of the Boreal sections and shows a significant hiatus in the upper Spathian. Two major deepening events, in earliest Griesbachian and late Smithian time, are separated by shallowing-upwards trends that culminated in the Dienerian and Spathian substages. The redox record, revealed by changes in bioturbation, palaeoecology, pyrite framboid content and trace metal concentrations, shows anoxic phases alternating with intervals of better ventilation. Only Dienerian–early Smithian time witnessed persistent oxygenation that was sufficient to support a diverse benthic community. The most intensely anoxic, usually euxinic, conditions are best developed in offshore settings, but at times euxinia also developed in upper offshore settings where it is even recorded in hyperpycnite and storm-origin sandstone beds: an extraordinary facet of Spitsbergen's record. The euxinic phases do not track relative water depth changes. For example, the continuous shallowing upwards from the Griesbachian to lower Dienerian was witness to several euxinic phases separated by intervals of more oxic, bioturbated sediments. It is likely that the euxinia was controlled by climatic oscillations rather than intra-basinal factors. It remains to be seen if all the anoxic phases found in Spitsbergen are seen elsewhere, although the wide spread of anoxic facies in the Smithian/Spathian boundary interval is clearly a global event.

A high-resolution and continuous conodont apatite oxygen isotope record spanning the late Viséan to Middle Permian is reported from South China, which is interpreted with respect to the ice volume and/or tropical sea water temperature history of the Late Paleozoic Ice Age (LPIA). The presented δ18O record shows significant fluctuations in δ18O from the late Viséan to Middle Permian with highest values observed in the Bashkirian (Early Pennsylvanian). The δ18O maximum coincides with a major eustatic sea level fall recorded in low-latitudinal successions, and postdates the significant increases in 87Sr/86Sr and δ13Ccarb measured on well-preserved brachiopod calcite, which can be interpreted as reflecting intensified weathering as consequence of the closure of Rheic Ocean as well as enhanced carbon burial. Both processes may have contributed to lower greenhouse gas levels and cooled down the Earth's surface, triggering the maximum glaciation. The high Bashkirian δ18O values are interpreted to represent the glacial maximum of the LPIA. A coeval change in faunal composition and a decreasing diversity in climate-sensitive marine invertebrates can be ascribed to icehouse cooling and/or loss of habitat. Despite inconsistenceies with earlier interpretations that the Early Permian represented the glacial maximum of the LPIA as inferred from Gondwanan glacial sediments records, the suggested Bashkirian glacial maximum agrees well with ice extent estimates based on the regional tectonic history in Gondwana, which suggests that the Bashkirian glaciation occurred during Gondwana interior uplift promoting maximum ice cover of the entire LPIA. However, maximum glaciation is only poorly represented in the depositional record because large parts of the glacial deposits were possibly removed by erosion as outlined by a major regional unconformity.

Conodont faunas from the Wulankeshun section in the northwestern Junggar Basin of Xinjiang, NW China, are characterized by shallow-water assemblages with many endemic taxa. This study presents separate local icriodid and polygnathid conodont zonations for the Lower Member of the Hongguleleng Formation, which can only roughly be correlated with the pelagic “standard zonation”. The basal beds of the Hongguleleng Formation are assigned to a low diverse Icriodus praealternatus ferus n. ssp. Zone, which possibly includes latest Frasnian strata but it continues into the basal Famennian. At present, the Frasnian/Famennian boundary cannot be defined unequivocally by conodonts and there are no obvious Upper Kellwasser equivalents. However, the carbon isotope data are comparable with the Bulongguor Reservoir stratotype, where the top-Frasnian lies within the basal Hongguleleng Formation. In the early Famennian, partly endemic icriodid lineages provide successive I. cornutus, I. stenoancylus junggarensis n. ssp., and I. plurinodosus n. sp. (sub)zones. The basal Famennian is possibly marked by the oldest, endemic species of Neopolygnathus, Neo. huijunae n. sp. It is followed by local Neo. communis communis, “Polygnathus” pomeranicus, Po. cf. szulczewskii, and “Po.” pseudocommunis n. sp. zones. The new local conodont zonations provide a high biostratigraphic resolution for further future studies. The Wulankeshun shallow-water conodont faunas show restricted similarities with contemporaneous faunas from eastern Europe, Kazakhstan, and Iran. There are a few taxa that were originally described from other distant regions, such as NW Canada and eastern Australia. The local high number of endemic taxa (17 (sub)species, 46%) points to a significant plate tectonic isolation of the Junggar Basin in the early Famennian.

The Hangenberg Event at the Devonian-Carboniferous (D-C) transition is a period of mass extinction and rapid global faunal changes characterized by carbon-rich black shale deposits in many locations throughout Europe, North America, and Asia. Conodont biostratigraphy indicates that the D-C boundary is present within the Pho Han Formation on Cat Ba Island in northeastern Vietnam, which represents a basinal facies of the South China platform. The Pho Han Formation is primarily composed of whitish to dark gray carbonates punctuated with black shales. Scanning electron microscopy (SEM) imaging has been used to determine presence and size distribution of pyrite framboids, which serve as a proxy for water column redox conditions. Samples examined to date contain more than 7000 framboids/cm ². Between 88.5% and 97.1% of the framboids observed were less than five microns in diameter, indicating euxinic conditions that extended throughout the basin’s history and were not constrained to the Hangenberg Event. SEM analysis also confirms the presence of kerogen within many of the beds. Whole rock geochemistry analyses indicate a Mo spike near the D-C transition, further confirming the highly anoxic conditions around the time of the Hangenberg Event. The geochemical results also indicate clastic input stratigraphically above the Mo spike, possibly due to a major regression (consistent with the Hangenberg Event in other locations). This research shows long-term, sustained anoxia/euxinia in this ocean basin and supports the location of the Hangenberg Event within the Pho Han Formation on Cat Ba Island, Vietnam.

Fluorine-, boron-, and magnesium-rich metamorphosed xenoliths occur in the Campanian Ignimbrite (CI) deposits at Fiano(southern Italy), at about 50 km northeast of the sourced volcanic area. These rocks originated from Mesozoic limestones of the Campanian Apennines, embedded in a fluid flow. The studied Fiano xenoliths consist of ten fluorophlogopite-bearing calc-silicate rocks and five carbonate xenoliths, characterized by combining mineralogical analyses with whole rock and stable isotope data. The micaceous xenoliths are composed of abundant idiomorphic fluorophlogopite, widespread fluorite, F-rich chondrodite, fluoborite, diopside, Fe(Mg)-oxides, calcite, humite, K-bearing fluoro-richterite and grossular. Out of the five mica-free xenoliths, two are calcite marbles, containing very subordinate fluorite and hematite, and three are weakly meamorphism carbonates, composed of calcite only. The crystal structure and chemical composition of fluorophlogopite approach those of the end member. The Fiano xenoliths are enriched in trace elements with respect to the primary limestones. Comparison between the REE patterns of the Fiano xenoliths and those of both CI and Somma-Vesuvius marble and carbonate xenoliths shows that the Fiano pattern on the whole both overlaps that of Somma-Vesuvius marble and carbonate xenoliths, and yet reproduces the trend of CI rocks. δ13C and δ18O values depict the same trend of depletion in the heavy isotopes observed in the Somma-Vesuvius nodules, related to thermometamorphism. Trace element distribution, paragenesis, stable isotope geochemistry and data modelling point to infiltration of steam enriched in F, B, Mg, As into carbonate rocks at temperature of ∼ 300- 450°C during the emplacement of the CI.

New collecting at a biostratigraphically highly-resolved deep-water section in South China, reveals a brief (a few tens of thousands of years) but measurable delay in extinction timing relative to contemporaneous, shallower water sections. Foraminifers and conodonts in the Bianyang section show a sharp extinction at the top of Hindeodus changxingensis Zone, whilst in shallower sections, such as the well-known Meishan GSSP location, these taxa have a major extinction pulse at the top of the preceding Clarkina yini Zone. The main end-Permian extinction coincides with the onset of a negative carbon isotope excursion whilst the deep-water extinctions occur around the lowpoint of the carbon isotope curve. Rapidly increasing surface water temperatures, and the effects of deep-water anoxia were all important during the crisis although it is noteworthy that regression and extinction also show a close temporal link.

The Early Aptian encountered several crises in neritic and pelagic carbonate production, majorperturbations in the carbon cycle, and an oceanic anoxic event (OAE1a). Yet the causal links betweenthese perturbations and climate changes remain poorly understood, partly because temperature recordsspanning the Early Aptian interval are still scant. We present new δ18O data from well-preserved bivalves froma carbonate platform of the Galve subbasin (Spain) that document a major cooling event postdating mostof OAE1a. Our data show that cooling postdates the global platform demise and cannot have triggeredthis event that occurred during the warmest interval. The warmest temperatures coincide with the timeequivalent of OAE1a and with platform biotic assemblages dominated by microbialites at Aliaga as well as onother Tethyan platforms. Coral-dominated assemblages then replace microbialites during the subsequentcooling. Nannoconids are absent during most of the time equivalent of the OAE1a, probably related to thewell-known crisis affecting this group. Yet they present a transient recovery in the upper part of this intervalwith an increase in both size and abundance during the cool interval portion that postdates OAE1a. Anevolution toward cooler and drier climatic conditions may have induced the regional change from microbialto coral assemblages as well as nannoconids size and abundance increase by limiting continent-derivedinput of nutrients.

This study investigates stable isotope signatures of five species of Silurian and Devonian deep-water, ahermatypic rugose corals, providing new insights into isotopic fractionation effects exhibited by Palaeozoic rugosans, and possible role of diagenetic processes in modifying their original isotopic signals. To minimize the influence of intraskeletal cements on the observed signatures, the analysed specimens included unusual species either devoid of large intraskeletal open spaces ('button corals': Microcyclus, Palaeocyclus), or typified by particularly thick corallite walls (Calceola). The corals were collected at four localities in the Holy Cross Mountains (Poland), Mader Basin (Morocco) and on Gotland (Sweden), representing distinct diagenetic histories and different styles of diagenetic alteration. To evaluate the resistance of the corallites to diagenesis, we applied various microscopic and trace element preservation tests. Distinct differences between isotopic compositions of the least-altered and most-altered skeleton portions emphasise a critical role of material selection for geochemical studies of Palaeozoic corals. The least-altered parts of the specimens show marine or near-marine stable isotope signals and lack positive correlation between δ13C and δ18O. In terms of isotopic fractionation mechanisms, Palaeozoic rugosans must have differed considerably from modern deep-water scleractinians, typified by significant depletion in both 18O and 13C, and pronounced δ13C-δ18O co-variance. The fractionation effects exhibited by rugosans seem similar rather to the minor isotopic effects typical of modern non-scleractinian corals (octocorals and hydrocorals). The results of the present study add to growing evidence for significant differences between Scleractinia and Rugosa, and agree with recent studies indicating that calcification mechanisms developed independently in these two groups of cnidarians. Consequently, particular caution is needed in using scleractinians as analogues in isotopic studies of extinct coral lineages. Answering some of the pertinent palaeoecological questions, such as that of the possibility of photosymbiosis in Palaeozoic corals, may not be possible based on stable isotope data.

The Early Triassic was a time of remarkably high temperatures, large carbon cycle perturbations and episodes of widespread ocean anoxia. The sediments in the Nanpanjiang Basin of South China provide superb opportunities to examine the sedimentary response to these extreme conditions especially during the crisis interval at the Smithian–Spathian (S-S) boundary. We have investigated a deep water section at Jiarong and a shallower water section at Mingtang. These contain a range of facies including black shales, micritic limestone units and rudaceous carbonate event beds that include flat pebble conglomerates and breccia debrites that bear similarities to the hybrid event beds seen in clastic turbidite successions.

The Reef Ridge deposit is a typical supergene "nonsulfide" zinc mineralization, located in the Yukon-Koyukuk region of west-central Alaska (USA). It is hosted in sedimentary rocks of the Farewell terrane, a continental fragment sandwiched between the Siberian and Laurentian cratons during the early Paleozoic. The mineralization occurs in Lower-Middle Devonian shallow-water dolomite of a Paleozoic carbonate platform succession belonging to the Nixon Fork tectonic unit. The mineralization consists of oxidized minerals associated with minor remaining sulfides (pyrite/ marcasite and sphalerite). In the oxidation zone, smithsonite is the predominant mineral, mixed with Fe(hydr)oxides (goethite and hematite). A complete petrographic and mineralogical study was performed. Samples were analyzed by X-ray diffraction, inductively coupled plasma-mass spectrometry and emission spectrometry, energy dispersive scanning electron microscopy, and QEMSCAN (R)-(quantitative evaluation of minerals by scanning electron microscopy). The most abundant mineral in the nonsulfide ore is smithsonite. Similar to other nonsulfide Zn deposits worldwide, the first generation of smithsonite has replaced both primary sphalerite and the host carbonates. A second smithsonite generation precipitated as cement in vugs, cavities, and fractures. Minor-zinc amounts also occur in the Fe-(hydr)oxides-, and zinc traces have been identified in clay minerals. The carbon and oxygen isotope values of smithsonite at Reef Ridge vary from -0.7 to 2.1 parts per thousand relative to Vienna Peedee belemnite (VPDB) and 19.1 parts per thousand to 21.9 parts per thousand relative to Vienna-standard mean ocean water (VSMOW). The delta C-13 values are similar to those of the host rock, suggesting that the predominant carbon source for smithsonite was the host carbonates, with only a limited contribution from organic carbon. The oxygen isotope ratios of Reef Ridge smithsonite are more depleted in O-18 compared to supergene nonsulfides from other parts of the world formed under warm-humid, temperate, or semiarid climates. The oxygen isotope fractionation between water and smithsonite, which relates the delta O-18 value of the mineralizing solution, the formation temperature of smithsonite, and its delta O-18 composition, indicates that the delta O-18 composition of Reef Ridge smithsonite is related to very low formation temperatures (similar to 10 degrees C), and strong depletion in O-18 of the precipitating waters. The delta O-18 smithsonite composition, the strong O-18 depletion, and the relationship of the formation of the Reef Ridge nonsulfide deposit with the development of the Sleetmute upland surface (which started in the Late Tertiary and continues to the present) indicate that the formation of the Reef Ridge nonsulfide deposit is probably related to cold/humid weathering episodes during a period comprised between Late Tertiary and Holocene. The "traditional" interpretation on the genesis of Zn nonsulfide deposits in warm-humid, temperate, or semiarid conditions should be questioned where other climate zones are indicated.

The controversial Capitanian (Middle Permian, 262 Ma) extinction event is only known from equatorial latitudes, and consequently its global extent is poorly resolved. We demonstrate that there were two, severe extinctions amongst brachiopods in northern Boreal latitudes (Spitsbergen) in the Middle to Late Permian, separated by a recovery phase. New age dating of the Spitsbergen strata (belonging to the Kapp Starostin Formation), using strontium isotopes and d 13 C trends and comparison with better-dated sections in Greenland, suggests that the fi rst crisis occurred in the Capitanian. This age assignment indicates that this Middle Perm-ian extinction is manifested at higher latitudes. Redox proxies (pyrite framboids and trace metals) show that the Boreal crisis coincided with an intensifi cation of oxygen depletion , implicating anoxia in the extinction scenario. The widespread and near-total loss of carbonates across the Boreal Realm also suggests a role for acidifi cation in the crisis. The recovery interval saw the appearance of new brachiopod and bivalve taxa alongside survivors, and an increased mollusk dominance , resulting in an assemblage reminiscent of younger Mesozoic assemblages. The subsequent end-Permian mass extinction terminated this Late Permian radiation.

The δ13C record from an early Sheinwoodian limestone unit in the Prague Basin suggests its deposition during the time of the early Sheinwoodian carbon isotope excursion (ESCIE). The geochemical data set represents the first evidence for the ESCIE in the Prague Basin which was located in high latitudes on the northwestern peri-Gondwana shelf during early Silurian times.

The province of Jämtland, central Sweden, records a well-preserved but very thin suite of the Lower–Middle Ordovician cool-water carbonates. In this study we present the first carbon isotope profile for these strata on the basis of whole-rock samples from the Brunflo 2 core. The studied succession is 41.55 m thick and includes, in ascending order, the Bjørkåsholmen Formation, Latorp Limestone, Tøyen Shale, and the Lanna, Holen, and Segerstad limestones. We identify two distinct positive δ13C excursions that can be used for intra- as well as inter-continental correlations. A positive excursion in the Tøyen Shale probably correlates to the mid-late Floian and the Oepikodus evae Zone in Baltica and Precordillera, and the Reutterodus andinus Zone in North America. A continuous increase in δ13C values through the upper Holen Limestone and the preserved part of the overlying Segerstad Limestone is interpreted as the rising limb of the Middle Darriwilian Isotope Carbon Excursion (MDICE), an important tie-point for the global correlation of the Jämtland strata. Negative δ13C values associated with the Latorp Limestone may correlate with similar low values in the late Tremadocian and early Floian of the Argentine Precordillera and the Shingle Pass and Ibex sections in North America.

Based on δ 13 C data from two drillcores recovered from the Siljan district, we present a first continuous carbon isotope record of the upper Tremadocian–lower Katian limestone succession of central Sweden. New names for some isotopic carbon excursions from the Cambrian–Ordovician boundary through the basal Darriwilian are introduced. The Mora 001 core from the western part of the Siljan impact structure ranges through the Lower–Middle Ordovician, whereas the Solberga 1 core from its eastern part ranges through the Middle–lower Upper Ordovician. Upper Tremadocian and Floian units are extremely condensed and include extensive stratigraphic gaps. Multiple hardgrounds, sometimes with minor karstic overprint, imply recurrent periods of erosion and/or non-deposition. Like in other parts of Sweden, the Dapingian and Darriwilian succession is characterized by a relatively complete sedimentary record and low sedimentation rates.

Reefs developed simultaneously during the latest Sandbian/earliest Katian global Guttenberg Isotopic Carbon Excursion (GICE) in several places across Baltoscandia. Latest Sandbian/earliest Katian patch reefs are also described from the Vasalemma Formation of northern Estonia. The Saku Member of the Vasalemma Formation was previously considered as a proximal facies related to the reefs. However, the Saku Member clearly post-dates the GICE interval and ranges from the latest Keila to Rakvere in terms of regional stages. Some small reefs occur in direct proximity to the stratotype of the Saku Member. New δ 13 C data from the stratotype section and the adjacent reefs indicate that these reefs developed before the deposition of the Saku Member during the GICE interval. The chemostratigraphic data support the hypothesis of a short-time Baltoscandian reef growth event that terminated during the GICE interval.

A 506 m drill-hole has been recently drilled in the framework of the Campi Flegrei Deep Drilling Project (CFDDP) and the International Continental Scientific Drilling Program (ICDP) with the intention of coring the subsurface in the eastern sector of the Campi Flegrei caldera. The borehole, located in the western district of the Neapolitan city (Bagnoli Plain) 3 km to the east of the most active volcanic area and about 5 m above sea level, is now targeted for monitoring purposes. This paper reports the results obtained from the analysis of two short cores collected at depths of 443 and 506 m below the ground level. The cores sampled two pre-caldera tuffs. Observations performed by optical and scanning electron microscopy, energy dispersive spectroscopy and powder X-ray diffraction were used to achieve data on the primary lithology, both primary and secondary mineralogical assemblages, and the relationship between texture and secondary mineralization. Sr isotope ratios were determined on selected primary feldspars, whereas delta C-13 and delta O-18 analyses were performed on carbonates from veins and filled-voids in tuffs. Our results provide information on the hydrothermal system in the eastern sector of the caldera that was not among the goals in the previous drilling programs. Secondary mineralization suggests a saline hydrothermal environment characterized by fluids that progressively evolved from boiling toward more alkaline and cooler conditions. A paleo-temperature of ca. 160 degrees C has been inferred from authigenic mineral occurrences and calculated on the basis of equilibria between cored calcites and fluids presently emitted at the surface, by using carbon and oxygen isotope data. The temperature measured at the bottom of the drilling is about 80 degrees C. (C) 2014 The Authors. Published by Elsevier B.V.

The oxygen and strontium isotope composition of biogenic apatite in fossil shark teeth has demonstrated its worth for palaeoecological and palaeoenvironmental interpretations. δ18OP values and 87Sr/86Sr ratios were determined on disarticulated shark tooth material from several Early Permian (Sakmarian–Kungurian) continental bone beds of northern Texas and southern Oklahoma as well as from the marine Middle Permian (Roadian) of northern Arizona, predominantly derived from xenacanthiforms (Orthacanthus, Barbclabornia, Bransonella), hybodontids (Lissodus, Acrodus, Diablodontus) and ctenacanthids (Kaibabvenator, Glikmanius, Heslerodus). Tooth preservation was investigated by cathodoluminescence microscopy. The δ18OP values derived from teeth of bone beds are in the range of 17.6–23.5‰ VSMOW, and are mostly depleted in 18O by 0.5–5‰ relative to proposed coeval marine δ18OP values. This indicates an adaptation to freshwater habitats on the Early Permian coastal plain by several sharks. Distinctly higher δ18OP values from two bone beds are attributed to significant evaporative enrichment in 18O in flood plain ponds owing to warm and dry climate conditions and sufficient water residence time in the ponds. 87Sr/86Sr ratios of around 0.71077 are notably more radiogenic than 87Sr/86Sr of contemporaneous seawater. In contrast, the isotopic composition of teeth from the marine Kaibab Formation is characterised by low δ18OP values in the range of 13.4–15.6‰ VSMOW while 87Sr/86Sr ratios of around 0.70821 are closer to the Roadian seawater value. The distinctly depleted δ18OP values cannot be readily explained by fluvially affected freshening in a nearshore marine environment, so a diagenetic alteration of the Kaibab material seems to be more likely, excluding it from further interpretation. Differences in δ18OP between co-site hybodontid and xenacanthid teeth indicate a certain degree of niche partitioning of these taxa.

The Paleoproterozoic Malmani Subgroup and Penge Formation (Transvaal Supergroup) exposed on the farms Leeuwbosch and Cornwall north of Thabazimbi (Limpopo Province, South Africa) host hydrothermal Pb–Ag–Cu–Zn and high-grade hematite iron ore deposits which include the historic Leeuwbosch lead mine. Based on ore petrography, fluid inclusion and stable isotope analyses and geochemical modeling, the structurally controlled, stratabound Leeuwbosch Pb–Ag–Cu–Zn–Fe deposits formed from high salinity NaCl–CaCl2-rich basinal brines with total salinities from 18 to 24 wt.% NaCl equivalent which are similar to those found in the Mississippi Valley Type (MVT) Pb–Zn deposits. The minimum formation temperatures (homogenization temperatures) for the lead deposits range between 120 and 185 °C and the estimated formation conditions are 200 °C at 1 kbar pressure. Stable isotope analyses of gangue siderite and calcite indicate that the deposits formed from base metal-enriched brines derived from recycled seawater with δ13Cvs. PDB from 0.46 to 3.17‰ and δ18Ovs. SMOW from − 2.95 to − 1.79‰. Hydrothermal transport of lead and silver as PbCl3− and AgCl2− respectively took place at mildly acidic pH and elevated fO2 in the SO42 − predominance field. Extensive host rock interaction neutralized and reduced the ore fluid to precipitate galena hosting Ag with chalcopyrite and sphalerite. Fluid inclusions in gangue quartz and calcite in the extensive structurally controlled and pervasive stratabound hydrothermal iron ore deposits on the farms Leeuwbosch and Cornwall, chiefly consisting of high-grade hematite with rare relict magnetite, show a wide compositional variability due to episodic fluid mixing and successive hydrothermal activity in the presence of several distinct fluid end members. Total salinities of fluid inclusions in quartz from the hematite deposits range from 9.2 to 39.9 wt.% NaCl eq. with highly variable proportions of NaCl and CaCl2 and minimum formation temperatures are between 100 and 190 °C. The estimated formation conditions for the iron ore deposits are 175 °C and 1 kbar. Stable isotopes of gangue calcite indicate that diagenetic fluids with δ13Cvs. PDB from − 3.33 to − 2.09 and δ18Ovs. SMOW from 2.52 to 5.60‰ and a second fluid with δ13Cvs. PDB of − 7.45 and δ13Cvs. PDB of 17.45 were controlling the formation of the hematite deposits. In agreement with oxidized conditions during hematite formation and characteristic host rock alteration patterns traced by carbon and oxygen isotopes, the second low salinity fluid was derived from the overlying Waterberg Group sandstones and played an important role in the formation of the iron ore deposits, in addition to high salinity diagenetic brines. Iron was leached from the BIFs of the Penge Formation, transported as FeCl+ under mildly acidic conditions and likely deposited in response to the oxidation of the iron-bearing fluids. The lead and iron ore deposits formed by combinations of structural controls which influenced the regional fluid flow patterns and fluid compositions, and fluid–rock interaction with reactive carbonate lithologies of the Malmani Subgroup which acted as a sink for metals transported in acidic hydrothermal solutions.

A life-size whitish marble statue of a “Virgin with Child” has been recently rediscovered in the St. Rosario church located in Ottaviano, a small town near Naples (southern Italy). This artwork shows stylistic features of the Tuscan-Roman school of the 16th century, and is framed in an intriguing historical context. Historical documents testify that the sculpture was a property of the cadet branch of noble Tuscan family of the Medici, the Medici of Ottaviano. A multianalytical approach has been used to try to indicate the supply area of the white marble of the studied sculpture. Considering the whole mineralogical, petrographic and geochemical data, the source rock can be possibly limited to the main classical white marbles of the Mediterranean district, as the classical marble of Aphrodisias. A reuse practice of a former artwork can be also hypothesized.

The end-Permian mass extinction has been associated with severe global warming. Main stage volcanism of the Siberian Traps occurred at or near the extinction interval and has been proposed as a likely greenhouse catalyst. In this study, a high-resolution δ18O record is established using diagenetically resistant apatite of conodonts and low-Mg calcite of brachiopods from stratigraphically well-constrained Permian-Triassic (P-Tr) boundary successions in northwestern Iran. A new evaluation is made for previously published conodont δ18O values from South China and revised palaeotemperatures are presented together with new data from Wuchiapingian to Griesbachian sections in Iran. δ18O data from P-Tr sections in Iran document tropical sea surface temperatures (SST) of 27-33 °C during the Changhsingian with a negative shift in δ18O starting at the extinction horizon, translating into a warming of SSTs to over 35 °C. The results are consistent with re-calculated SSTs of the South Chinese sections. Warming was associated with an enhanced hydrological cycle involving increased tropical precipitation and monsoonal activity in the Tethys Sea. Global warming, intensification of the hydrological cycle and associated processes, vertical water column stratification, eutrophication and subsequent local anoxia may all have facilitated an extinction event.

The Jabali Zn–Pb–Ag deposit is located about 110 km east of Sana'a, the capital of Yemen, along the western border of the Marib-Al-Jawf/Sab'atayn basin. The economic mineralization at Jabali is a nonsulfide deposit, consisting of 8.7 million tons at an average grade of 9.2% zinc, derived from the oxidation of primary sulfides. The rock hosting both primary and secondary ores is a strongly dolomitized carbonate platform limestone of the Jurassic Shuqra Formation (Amran Group). The primary sulfides consist of sphalerite, galena and pyrite/marcasite. Smithsonite is the most abundant economic mineral in the secondary deposit, and is associated with minor hydrozincite, hemimorphite, acanthite and greenockite. Smithsonite occurs as two main generations: smithsonite 1, which replaces both host dolomite and sphalerite, and smithsonite 2, occurring as concretions and vein fillings in the host rock. At the boundary between smithsonite 1 and host dolomite, the latter is widely replaced by broad, irregular bands of Zn-bearing dolomite, where Zn has substituted for Mg. The secondary mineralization evolved through different stages: 1) alteration of original sulfides (sphalerite, pyrite and galena), and release of metals in acid solutions; 2) alteration of dolomite host rock and formation of Zn-bearing dolomite; 3) partial dissolution of dolomite by metal-carrying acid fluids and replacement of dolomite and Zn-bearing dolomite by a first smithsonite phase (smithsonite 1). To this stage also belong the direct replacement of sphalerite and galena by secondary minerals (smithsonite and cerussite); 4) precipitation of a later smithsonite phase (smithsonite 2) in veins and cavities, together with Ag- and Cd-sulfides.

We present the first universal calibration of the clumped isotope thermometer for calcites of various mineralizing types. These are an eggshell of an ostrich, a tropical bivalve, a brachiopod shell, cold seep carbonate, and three foraminifera samples that grew between 9 and 38 °C. CaCO3 was digested at 90 °C using a common acid bath. Considering a difference in phosphoric acid fractionation factors between reaction at 25 and 90 °C of 0.069‰ (Guo et al., 2009), the function between growth temperature T and the excess of 13C-18O bonds in the evolved CO2 is expressed by a linear regression between 1/T2 and absolute Δ47 (R2 = 0.9915):

Supplying WELL-DATED carbonized plant remains (or palynomorphs) of terrestrial origin, especially from the lowermost and Upper Devonian stages, is highly welcome and would contribute to a better understanding of the evolution of the Devonian carbon cycle.

Permian sedimentary rocks exposed in the southwestern USA record a highly diverse shark fauna from marine and continental environments. Especially mixed marine and “typically freshwater-considered” shark faunas in Early Permian (Sakmarian–Kungurian) continental bone beds complicate palaeoecological evaluation of the available taxa. These bone beds were originally formed on a coastal plain along the northeastern margin of the Midland Basin in western equatorial Pangaea that was dominated by meandering rivers and associated floodplain environments with repeatedly intercalated marine limestones. The oxygen and strontium isotope composition of biogenic apatite in fossil shark teeth has demonstrated its worth to widen the knowledge regarding palaeoenvironmental conditions as well as habitat preferences of the investigated fishes. δ18OP values and 87Sr/86Sr ratios were determined on 36 disarticulated teeth from four bone beds of northern Texas (Conner Ranch, Coprolite Site, Spring Creek B) and southern Oklahoma (Waurika), derived from the xenacanthiform sharks Orthacanthus texensis (Cope, 1888) and Barbclabornia luederensis (Berman, 1970) as well as the hybodontid Lissodus zideki (Johnson, 1981), which numerically dominate the fossil assemblages. Tooth preservation was ascertained by cathodoluminescence microscopy. The δ18OP values derived from the teeth are in the range of 17.6–23.5‰ VSMOW, and are mostly depleted in 18O by 0.5–5‰ relative to proposed coeval marine δ18OP values. This indicates an adaptation to freshwater habitats on the coastal plain by these sharks. Distinctly higher δ18OP values from two bone beds (Waurika, Spring Creek B) are attributed to significant evaporative enrichment in 18O in floodplain ponds owing to warm and dry climate conditions and sufficient water residence time in the ponds. 87Sr/86Sr ratios of around 0.7108 are notably more radiogenic than 87Sr/86Sr of contemporaneous seawater (0.7074–0.7079). Differences in δ18OP between co-site hybodontid and xenacanthid teeth indicate a certain degree of niche partitioning of these taxa. Moreover, the δ18OP pattern from the bone beds may trace the overall Permian aridification trend between Sakmarian and Kungurian by progressive 18O-enrichment in shark tooth bioapatite during times within non-marine environments in combination with a shift of the ponds closer to nearshore on the coastal plain. Altogether, the conspicuous mixture of fossil taxa in the bone beds that are typically considered to be freshwater in origin with species that are regarded as marine might represent different scenarios: (1) a euryhaline behaviour of the latter with a ‘temporary’ coexistence in the pond; (2) accumulation of different remains owing to reworking of underlying marine deposits; or (3) post-mortem transport from freshwater deposits into a ‘brackish pond’.

Based on the Tingskullen drillcore, we present the first continuous carbon isotope stratigraphy from the Lower–Middle Ordovician “orthoceratite limestone” of O¨ land, Sweden. The extremely condensed Tremadocian and Floian stages include large gaps as well as the Ceratopyge Regressive Event and the widespread Evae transgression accompanied by prominent shifts in the d13C record. The Dapingian and Darriwilian stages are characterised by low sedimentation rates and a relatively complete sedimentary record. A total of 99 whole-rock samples were analysed for carbon isotope geochemistry from the Ordovician part of the succession (46m thick). The most striking anomaly detected is the middle Darriwilian isotope carbon excursion (MDICE) that appears unusually well developed and complete for the region, and thus forms an important proxy for intercontinental correlation of the succession.

We present the first universal calibration of the clumped isotope thermometer for calcites of various mineralizing types. These are an eggshell of an ostrich, a tropical bivalve, a brachiopod shell, cold seep carbonate, and three foraminifera samples that grew between 9 and 38 °C. CaCO3 was digested at 90 °C using a common acid bath. Considering a difference in phosphoric acid fractionation factors between reaction at 25 and 90 °C of 0.069‰ (Guo et al., 2009), the function between growth temperature T and the excess of 13C–18O bonds in the evolved CO2 is expressed by a linear regression between 1/T2 and absolute Δ47 (R2 = 0.9915): Δ47=0.0327(±0.0026)×106/T2+0.3030(±0.0308)(withΔ47in‰andTinK). Both the slope and intercept of our regression line deviate significantly from the first experimental calibration based on synthetic calcites digested at 25 °C (Ghosh et al., 2006a) and from several other studies having confirmed this pioneering calibration (i.e., Came et al., 2007; Tripati et al., 2010; Thiagarajan et al., 2011; Grauel et al., 2012; Saenger et al., 2012; Zaarur et al., 2013). However, our relationship between temperature and absolute Δ47 values is indistinguishable from that determined by Henkes et al. (2013) if the same difference in phosphoric acid fractionation factors between 25 and 90 °C is applied to both datasets. Our study and that of Henkes et al. (2013) have in common that data were primarily projected onto the absolute scale proposed by Dennis et al. (2011) – a reference frame that allows comparison of clumped isotope data measured in different laboratories. Furthermore, at any T, our regression line lies within 0.006‰ of the theoretical calcite calibration of Guo et al. (2009). The observation that both empirical calibrations are indistinguishable from each other implies that clumped isotope data can be directly compared between laboratories and referenced to a unique temperature calibration if (1) the phosphoric acid digestion temperature is set to 90 °C, and (2) raw data are primarily projected to the absolute scale.

Oxygen isotope composition of shark dental tissue biomineral have been studied in three modern species from monitored environment (temperature and salinity) of the tropical ocean tank at the Blackpool Sea Life Center. Teeth of Carcharhinus plumbeus, Carcharhinus melanopterus and Carcharias taurus were collected from deceased specimens in-situ, and from the substrate. Two geochemical methods have been applied to obtain the 18 O / 16 O ratios: (1) the in-stu δ 18 O measurements of entire fluorapatite oxygen components within separate layers of enameloid and dentine has been carried out using Cameca 1280 secondary ion microprobe (NORDSIM), and (2) conventional IRMS analyses of the δ 18 O of chemically separated phosphatic component has been performed in parallel on tissue-selective bulk samples. The resulting δ 18 O values showed intra-tissue uniformity (parallel-bundled enameloid in particular) of each species within the sub-permil precision of the measurements, but gave average 2‰ (1σ = ± 0.35) inter-specific variation, comparable to previously reported 2.5‰ and 2.9‰ taxonomic offsets in fossil vertebrate bioapatite. The δ 18 O variation within and between species have both histological and mineralogical explanations, and allow us to estimate the extent of 'vital effects' as part of the oxygen isotopic fractionation in modern aquatic vertebrate fluorapatite, as well as species-specific biomineralization patterns in sharks.

A high-resolution oxygen isotope record based on 356 measurements of conodont apatite from several low latitudinal sections in South China, USA and Iran was composed in order to unravel Permian palaeotemperature and ice volume history. The conodont apatite δ¹⁸O record is compared to published brachiopod calcite δ¹⁸O records. Brachiopods and conodonts from different palaeocontinents show significantly different δ¹⁸O values, suggesting differences in local climatic conditions (e.g., evaporation/precipitation ratio). As a consequence, secular changes in palaeotemperature and oxygen isotope composition of Permian sea water cannot be reconstructed from records combined from different areas, but have to be based on records from a specific area.

New oxygen isotope data from the Prague Basin document drastic climate changes from a cold interval during the early Přídolí followed by moderate to rapid warming and development of supergreenhouse conditions during the late Přídolí transgrediens graptolite Zone. This extremely warm climate presumably triggered the flooding of northern Gondwana shelf areas. The corresponding fine-grained siliciclastics are widely distributed in Romania, Turkey, Saudi Arabia, Libya, the Algerian Sahara, NW Spain, and central and northern Armorican Massif (see references in Jaglin & Paris 2002). In cratonal and shelf successions in tropical and subtropical areas (e.g., Laurentia; Ross & Ross 1996), the Přídolí successions are often not recorded due to widespread palaeokarst development in the areas covered by shallow epicontinental seas. However, the highstand during the transgrediens interval is recorded in deeper shelf and basinal areas (e.g. eastern Baltoscandian Basin, Lazauskiene et al. 2003). Přídolí warming event is expressed by an increase in surface seawater temperatures of more than 8°C in the mid latitudes of northern peri-Gondwana, and was followed by cooling in the latest Přídolí and across the Silurian–Devonian boundary. During the TBE, high seawater temperatures stressed shelf faunas culminating in high extinction rates and presumably affected the entire food chain including planktonic organisms.

The end-Permian mass extinction has been associated with rapid and severe global warming. Main stage volcanism of the Siberian traps occurs at or near the extinction interval and has been proposed as a likely greenhouse catalyst (Wignall and Twitchett, 1996). The worldwide occurrence of a negative 13 C excursion is a second prominent feature often directly related to volcanism and associated CO 2 degassing (Erwin, 1993). The 4‰ negative carbon isotope shift requires carbon sources depleted in 13 C (CH 4 and CO 2), possibly from synergistic effects such as oxidation of sedimentary organic matter and destabilization of marine methane clathrates (Berner, 2002). However, proxy studies providing support for the hypothesis of extreme climate change are limited (Brand et al., 2012; Joachimski et al., 2012). Oxygen isotope records are presented from two Iranian sections spanning the Permian-Triassic interval. Pre-extinction values are remarkably stable between 19 and 20‰ VSMOW. Calculated seawater temperatures range between 30-35°C assuming an ice-free ocean with a 18 O w of -1‰ VSMOW. In comparison, 18 O values of late Permian pristine brachiopod calcite range from 2.3 to 3.5‰VPDB and give palaeotemperatures ranging from 27-35°C. A continuous 18 O record across the Permian-Triassic boundary was reconstructed by analyzing the conodont taxa Hindeodus sp. A distinct 1 to 3‰ excursion (5-10°C increase) is observed, which plateaus in the early Griesbachian. These tropical seawater temperatures match inferred temperatures from CO 2 models (Kiehl and Shields, 2005; Rampino and Caldeira, 2005) and temperatures from clumped isotope palaeothermometry (Brand et al., 2012). However, they are higher then temperatures reported in an previous 18 O study on conodonts from the P-T sections in China (Joachimski et al. 2012) but similarly peak temperatures seem to lag the extinction event as well as the decrease in 13 C. However, calculated temperatures would have been lethal for many organisms and could certainly have added to the slow recovery in the aftermath of the extinction (Romano et al., 2012; Sun et al., 2012). References

Goudemand et al. replot a subset of our well-constrained data using a new Early Triassic biostratigraphic scheme based on a lower-resolution ammonoid zonation scheme and hypothetical ammonoid-conodont correlation to produce a less distinct seawater temperature history. We dispute their unsubstantiated correlation and, consequently, their allegations.

Siljan is Europe’s largest impact structure and preserves unique Lower Palaeozoic sedimentary successions in its ring-like depression around the central uplift. Outcrops are limited, but the Lower Palaeozoic stratigraphy investigated in three core sections provides new information revolutionizing the knowledge of the development of this area located at the western margin of Baltica. Effects of the Ordovician/Silurian foreland basin development and several facies belts can be observed in the sedimentary record of the area some 100 km away from the Caledonian front in the west (Fig. 1A). The Mora 001, Stumsnäs 1 and Solberga 1 cores (Fig. 1B) provided by the Swedish company Igrene AB comprise more than 1500 m of strata ranging from the late Tremadocian to Wenlock in age. The cores provide a complex dataset which is the basis for reconstructing shifts in palaeoclimate, sea-level, and changes in ecosystems. The volcanic record, expressed by Ordovician and Silurian K-bentonites, may be compared to occurrences of ash layers in other parts of Baltoscandia which serve as time-lines in a detailed stratigraphic framework including litho-, bio-, chemo- and sequence stratigraphic parameters. Well-defined carbon isotope excursions are additional pin-points within this framework.

One of the main effects of supergene alteration of ore-bearing hydrothermal dolomite in areas surrounding secondary zinc orebodies (Calamine-type nonsulfides) in southwestern Sardinia (Italy) is the formation of a broad halo of Zn dolomite. The characteristics of supergene Zn dolomite have been investigated using scanning electron microscopy and qualitative energy-dispersive X-ray spectroscopy, thermodifferential analysis, and stable isotope geochemistry. The supergene Zn dolomite is characterized by variable amounts of Zn, and low contents of Pb and Cd in the crystal lattice. It is generally depleted in Fe and Mn relative to precursor hydrothermal dolomite (Dolomia Geodica), which occurs in two phases (stoichiometric dolomite followed by Fe-Mn-Zn-rich dolomite), well distinct in geochemistry. Mg-rich smithsonite is commonly associated to Zn dolomite. Characterization of Zn-bearing dolomite using differential thermal analysis shows a drop in temperature of the first endothermic reaction of dolomite decomposition with increasing Zn contents in dolomite. The supergene Zn dolomites have higher δ18O but lower δ13C values than hydrothermal dolomite. In comparison with smithsonite-hydrozincite, the supergene Zn dolomites have higher δ18O, but comparable δ13C values. Formation of Zn dolomite from meteoric waters is indicated by low δ13C values, suggesting the influence of soil-gas CO2 in near-surface environments. The replacement of the dolomite host by supergene Zn dolomite is interpreted as part of a multistep process, starting with a progressive “zincitization” of the dolomite crystals, followed by a patchy dedolomitization s.s. and potentially concluded by the complete replacement of dolomite by smithsonite.

The Mediterranean is considered as an area which will be affected strongly by current climate change. However, temperature records for the past centuries which can contribute to a better understanding of future climate changes are still sparse for this region. We established a network of multi-century stable carbon isotope chronologies on Corsica to study long-term climate variation in the Western Mediterranean Basin. The chronologies show strong correlations with summer temperature and precipitation as well as summer cloud coverage. A summer temperature reconstruction (AD 1448-2008) reveals that the Little Ice Age was characterized by low, but not extremely low temperatures on Corsica. Relatively warm temperatures during the Maunder minimum may indicate a decoupling from climate cooling registered in northern latitudes. A comparison of the summer temperature reconstruction with a summer cloud coverage reconstruction indicates warm summers with reduced cloudiness during the periods AD 1480-1520 and 1950-2008 and cool and cloudy summers during AD 1580-1620 and 1820-1890. The distinct features of the reconstruction underline the uniqueness of the Corsican climate and highlight the necessity of a better temporal and spatial resolution of climate reconstructions for a more robust estimation of current climate change on a local scale.

Global warming is widely regarded to have played a contributing role in numerous past biotic crises. Here, we show that the end-Permian mass extinction coincided with a rapid temperature rise to exceptionally high values in the Early Triassic that were inimical to life in equatorial latitudes and suppressed ecosystem recovery. This was manifested in the loss of calcareous algae, the near-absence of fish in equatorial Tethys, and the dominance of small taxa of invertebrates during the thermal maxima. High temperatures drove most Early Triassic plants and animals out of equatorial terrestrial ecosystems and probably were a major cause of the end-Smithian crisis.

The oxygen and strontium isotopic composition of 125 teeth of the hybodont sharks Lissodus and Hybodus from various late Triassic (Rhaetian) bone bed localities in the Central European Basin are used as environmental and ecological tracers for the shallow epicontinental Rhaetian Sea. The preservation of tooth enameloid was ascertained by cathodoluminescence microscopy. Mean δ18OP values differ regionally across the Rhaetian Sea with values of 18.6 ±0.6 ‰ near the western gate, 16.1 ±0.8 ‰ in the east, 15.4 ±0.6 ‰ in the southeast, and 17.7 ±0.9 ‰ in the south. The δ18OP values in the eastern Rhaetian Sea are 4–5 ‰ lower relative to Tethyan seawater, while teeth from the southern and western parts close to the marine gates are less fractionated. The strontium isotopic composition of teeth from most localities is more radiogenic in comparison to late Triassic seawater. The observed spatial δ18OP trend in the Rhaetian Sea indicates a shift from marine to brackish conditions in the south and west towards extensively brackish conditions with salinities of less than 16 ‰ in the east, thus confirming the existence of two marine gates. Brackish conditions persisted throughout early Rhaetian times, and were maintained by increased fluvial discharge from the Vindelician-Bohemian and Fennoscandian Highs as a result of enhanced atmospheric moisture availability in the course of the Rhaetian transgression. The δ18OP values of Lissodus and Hybodus indicate euryhaline behaviour of Rhaetian hybodonts by exceeding modern shark intraspecific variability. The lack of accordance in δ18OP values between different isotopically conspicuous localities in the Rhaetian Sea contradicts a basin-wide migration pattern. Differences between co-site taxa might indicate some degree of niche partitioning.

An about 215 m thick sedimentary sequence of the Early Permian Gipshuken Formation was measured at Tålmodryggen in central Spitsbergen. The sequence consists of predominantly several metres thick gypsum deposits at the base, overlain by metre thick cyclic dolomite/gypsum alternations, followed by mainly laminated dolomites with intercalated layers of dolomitic marls, gypsum and ooids. The sediments are interpreted to represent deposits of salinas, sabkha cycles and shallow marine (lagoonal) environments. Stable carbon isotopes in the lower part of the Gipshuken Formation exhibit δC values similar to those known from open marine settings indicating that early diagenesis and dolomitisation took place in marine derived pore water solution. Distinctly lowered δC values in the upper Gipshuken Formation point to an influence of remineralisation of organic carbon and lower δC during diagenesis. The change in diagenesis may possibly be ascribed to a change from arid to slightly more humid conditions. German In Zentral-Spitzbergen wurde eine etwa 215 m mächtige Schichtenfolge der unterpermischen Gipshuken-Formation am Tålmodryggen aufgenommen. Die Abfolge besteht an der Basis aus vorwiegend mehrere Meter mächtigen Gipsablagerungen, überlagert von Meter mächtigen Gips/Dolomit-Wechsellagerungen und schließlich gefolgt von meist laminierten Dolomiten mit Einschaltungen von dolomitischen Mergeln, Gipsen und Oolithen. Die Schichten werden als Bildungen von Salinas, Sabkhas und flachmarinen (lagunären) Ablagerungsräumen gedeutet. Stabile Kohlenstoffisotope zeigen im tieferen Teil der Gipshuken-Formation δ13C-Werte, die den bekannten unterpermischen Werten aus offen marinen Profilen entsprechen. Daher lief die frühe Diagenese und Dolomitisierung wohl unter dem Einfluss von marinem Porenwasser ab. Deutlich erniedrigte δ13C-Werte in der höheren Gipshuken-Formation deuten auf den Einfluss von remineralisierter organischer Substanz und niedrigerem δ13CDIC während der Diagenese hin. Der Wechsel in der Diagenese ist möglicherweise auf einen Wechsel von ariden zu mehr humiden Bedingungen zurückzuführen.

During the last two decades it became evident that the Silurian was a period of major climatic changes. There are classic studies on the Gotland carbonate successions where Llandovery through Ludlow faunal extinctions, sedimentological changes and isotopic events have been intensively studied and there are many reports from coeval events in other parts of the world. However, in many areas Pridoli strata and events are often not preserved or not investigated to such detail. The graptolite extinctions (more than 70% of all graptolite taxa) during the Transgrediens Bioevent (TBE) are famous, but there are only limited data on other faunas, sedimentology or stable isotopes across the same interval. Our new oxygen isotope data from the Prague Basin display rapid climate warming and an increase in sea water temperatures of more than 8◦C in the mid latitudes of northern peri-Gondwana succeeded by major cooling in the latest Pridoli and across the Silurian-Devonian boundary. During the TBE, high sea water temperatures stressed shelfal faunas culminating in high cephalopod and graptolite (about 70%) extinction rates and presumably affecting as well primary producers. We assume that the drastic climate change from a cold interval with strong cooling during the early Pridoli followed by ‘cool’ to supergreenhouse conditions during the late Pridoli transgrediens graptolite Zone caused dramatic extinctions and faunal overturns on a global scale.

The Silurian was a period of major climatic changes, faunal overturns, drastic sea-level fluctuations and platetectonic reorganisations. Llandovery through Ludlow faunal extinctions, sedimentological changes and isotopic events have been intensively studied on Gotland and in other parts of the world. For Pridoli strata limited information is available, because sediments of this age are often not preserved or, if present, are commonly not investigated to such detail. There are reports on major graptolite extinctions affecting 70 % of all known taxa during the Transgrediens Bioevent (TBE). Unfortunately there are very limited data on other faunas, facies changes or stable isotopes across this famous interval. New oxygen isotope data from the Prague Basin document drastic climate change from a cold interval with strong cooling during the early Pridoli followed by moderate warming to a rapid development of supergreenhouse conditions during the late Pridoli transgrediens graptolite Zone. These climatic changes caused dramatic extinctions and faunal overturns on a global scale. This extreme climate warming expressed by an increase in sea water temperatures of more than 8° C in the mid latitudes of northern peri-Gondwana is succeeded by major cooling in the latest Pridoli and across the Silurian-Devonian boundary. During the TBE, high sea water temperatures stressed shelfal faunas culminating in high extinction rates and presumably affected the whole food chain including planctonic organisms.

Stable carbon and oxygen isotopes in tree rings are considered as reliable climate archives as they provide past environmental information with high resolution. However, recent studies have shown that isotope chronologies may reveal a long-term age trend and be influenced by non-climatic factors as other tree-ring parameters as well. These trends can only be identified in chronologies measured on individual trees but not on pooled sample chronologies consisting of several trees. In order to test whether pooled chronologies from pine trees from the Island of Corsica (Mediterranean/France) can be used for climatic reconstructions, we compared calculated mean values from 5 individual trees with pooled chronologies from the same 5 individuals. Carbon and oxygen isotope chronologies for a 50-year interval with annual resolution and 400 years with decadal resolution were analysed in order to document secular changes in inter-tree variability and to test for age related trends in the isotope ratios. Pooled carbon and oxygen isotope series correspond well to chronologies based on mean values calculated from analyses of individual trees. Inter-tree variability in oxygen isotope ratios is higher than in carbon isotope ratios but remains relatively constant over time. Similarities between the isotope series of individual trees are stronger over the 400-year time scale documenting a common long-term signal in the isotope values. No long-term age related trends are observed. Oxygen isotope values of the juvenile phase are characterised by a remarkable decrease over 40–50 years, interpreted to be related to the less developed root system of the young trees. This age effect can be avoided by not considering the first 50 years from the chronologies. Our results confirm that pooled carbon and oxygen isotope chronologies from Pinus nigra can be used for environmental reconstructions without statistical detrending.

The Katian (Upper Ordovician) facies succession of the Siljan district, central Sweden, records some of the most prominent environmental changes in the Ordovician of Baltoscandia. These changes include two separate phases of major sea-level drawdown that were of basinwide and presumably global importance. The first regression and lowstand terminated an entire generation of carbonate mud mounds (the Kullsberg Limestone) and resulted in the formation of polymict carbonate conglomerates (Skålberg Limestone) belonging to the Amorphognathus superbus Zone. New stable isotope data from the Amtjärn quarry shows that this is immediately after the peak of the Guttenberg Carbon Isotope Excursion (GICE), which reaches a δ13C peak value at 3.3‰ in the uppermost Amorphognathus tvaerensis Conodont Zone. A second major regression and sea-level lowstand is manifested by palaeokarst morphologies in the Slandrom Limestone, which formed close in time to the comparably minor Waynesville positive carbon excursion in the basal Amorphognathus ordovicicus Conodont Zone. The widespread exposure associated with this latter lowstand terminated carbonate production in much of the basin, and, during the subsequent flooding, organic-rich, graptolitic shale formed across most of Baltoscandia. The two corresponding sequence boundaries are amalgamated at the top of truncated carbonate mud mounds in the Siljan district, resulting in a pronounced Middle Katian hiatus in the immediate mound areas.

The δ18O values of phosphatic microfossils recovered from NW Ireland are used to determine the timing and magnitude of cooling associated with the onset of the Carboniferous glaciation. Microfossil fish δ18Oapatite demonstrates a +2.4‰ (V-SMOW) shift, which, once corrected for δ18Oseawater changes owing to evolving ice volumes, equates to an approximate 4.5 °C reduction in equatorial sea surface temperature between the earliest Asbian and the mid-Brigantian (late Visean). Both conodont and microfossil fish δ18Oapatite indicate stabilization of an ‘icehouse’ climate during the Brigantian and into the Serpukhovian. Substantial late Visean cooling identified herein is in good agreement with global glacioeustatic records.

A total of 239 isotope samples are used for establishing the δ13C chemostratigraphy in the upper Middle Ordovician to Lower Silurian succession in the approximately 70 m long Borenshult drillcore. The study interval starts in the upper Darriwilian Furudal Limestone and ends in the Rhuddanian Motala Formation. Four named δ13C excursions are recognized in 3–4 formations, namely the Guttenberg isotope carbon excursion (GICE) in the lower-middle Freberga Formation, the Kope (Rakvere) excursion in the uppermost Freberga Formation and possibly the Slandrom Formation, the Whitewater (Moe) excursion in the Lower Member of the Jonstorp Formation and the Hirnantian isotope carbon excursion (HICE) in the Loka Formation. The Middle Darriwilian isotope carbon excursion (MDICE) is missing in the drillcore and it is suggested that the study succession starts just above the interval of this excursion, which is in agreement with the range of MDICE in other Baltoscandic successions. The widespread Waynesville (Saunja) excursion may be cut out by the prominent unconformity below the Fjäcka Shale. The two most conspicuous excursions are the GICE (peak value ∼+1.9‰) and the HICE (peak value ∼+3.7‰), whereas the other excursions are represented by relatively minor perturbations in the δ13C curve. The Borenshult drillcore chemostratigraphy, which has been closely tied to conodont biostratigraphy, is quite similar to that of Estonian drillcores and is useful for not only trans-Baltic but also trans-Atlantic correlations. It is the first drillcore-based δ13C chemostratigraphy from the Swedish Ordovician.

The Early Cretaceous is punctuated by widespread biocalcification crises. These are characterized by decrease in the carbonate platform growth and, in the pelagic realm, by a decline in Nannoconus relative abundance in the calcareous nannofossil assemblages. The Valanginian Nannoconus decline started before the positive delta C-13 excursion characterizing the Weissert Event. The nannoconid decline is investigated in two sections of the Vocontian Basin, La Charce and Vergol, which are biostratigraphically well-constrained and contain well-preserved calcareous nannofossils. Absolute and relative abundances of Nannoconus show a polyphased decline, with a first decrease in the interval from the Campylotoxus to the Verrucosum Ammonite Subzones before the positive delta C-13 shift, and a second decrease from the end of the Peregrinus to the base of the Radiatus Ammonite Zones concomitant with the long-term decrease in delta C-13. These two declines are separated by an important increase in the Nannoconus abundance from the Verrucosum to the Peregrinus Ammonite Subzones concomitant with a slight short-term decrease of delta C-13. Biometric analysis shows size changes of N. steinmannii and N. kamptneri along the nannoconid decline. The patterns of abundances and size changes seem to be related to paleoenvironmental changes, mainly characterized by a temperature decrease and variable nutrient supply. The described Valanginian nannoconid recovery seems to occur during the most intense phase of the cooling event and is recorded in the Vocontian basin as well as in the Atlantic and Tethys Oceans. These spatial correlations suggest a supra-regional character for the Valanginian nannoconid recovery event best recorded in the Vocontian Basin and at low latitudes.

The oxygen isotopic compositions of Carboniferous conodonts and fish microfossils (ichthyoliths), from identical samples, were analysed in tandem in order to test whether these phosphatic media can be reliably used for palaeoclimatic reconstruction. The structure of conodonts and of most ichthyoliths analysed are somewhat analogous to the enamel and dentine/bone tissue, respectively, of modern mammals. Therefore, the diagenetic susceptibilities of the taxa analysed may provide important clues to other palaeoclimatic studies utilising a variety of biogenic apatite.Thermal maturation indices and scanning electron microscopy were used to characterise the preservation of biogenic apatite. Despite a high conodont colour alteration index (CAI) of ~ 5.5, conodont elements appear to have been only mildly affected by diagenetic alteration. In contrast, ichthyoliths were commonly recrystallised and exhibited diagenetic apatitic overgrowths containing amorphous pyrolytic carbon, interpreted as indicating that at least some overgrowth material derived from the original biogenic apatite.Diagenetic alteration has resulted in ichthyolith δ18O values being systematically lower by, on average, 2.9‰ (1σ = ± 0.3) relative to conodont apatite. Conodont samples yielded regionally correlatable isotope values, which can be interpreted in terms of more palaeoenvironmentally sensible palaeotemperatures relative to ichthyolith values. Densely crystalline, enamel-like conodont elements are interpreted as the more robust phosphatic medium to preserve original isotopic compositions. The strong correlation (r = 0.8) of the δ18O values of the more structurally pristine conodont and commonly recrystallised ichthyolith apatite, indicates that (i) despite diagenetic lowering of absolute isotope values, original palaeoenvironmental records may be preserved and (ii) diagenetic overprinting may result in a stable offset, and therefore be correctable, locally.

High-resolution oxygen isotope records document the timing and magnitude of global warming across the Permian-Triassic (P-Tr) boundary. Oxygen isotope ratios measured on phosphate-bound oxygen in conodont apatite from the Meishan and Shangsi sections (South China) decrease by 2 parts per thousand in the latest Permian, translating into low-latitude surface water warming of 8 degrees C. The oxygen isotope shift coincides with the negative shift in carbon isotope ratios of carbonates, suggesting that the addition of isotopically light carbon to the ocean-atmosphere system by Siberian Traps volcanism and related processes resulted in higher greenhouse gas levels and global warming. The major temperature rise started immediately before the main extinction phase, with maximum and harmful temperatures documented in the latest Permian (Meishan: bed 27). The coincidence of climate warming and the main pulse of extinction suggest that global warming was one of the causes of the collapse of the marine and terrestrial ecosystems. In addition, very warm climate conditions in the Early Triassic may have played a major role in the delayed recovery in the aftermath of the Permian-Triassic crisis.