Carbon Isotope Record Research Articles

The relation between carbon isotopic record of a stalagmite from Uchimagido cave, Kuji City and vegetational change inferred from pollen and phytolith records.

The relation between carbon isotopic record of a stalagmite from Uchimagido cave, Kuji City and vegetational change inferred from pollen and phytolith records.

Authigenic Carbonate and the History of the Global Carbon Cycle

We present a framework for interpreting the carbon isotopic composition of sedimentary rocks, which in turn requires a fundamental reinterpretation of the carbon cycle and redox budgets over Earth's history. We propose that authigenic carbonate, produced in sediment pore fluids during early diagenesis, has played a major role in the carbon cycle in the past. This sink constitutes a minor component of the carbon isotope mass balance under the modern, high levels of atmospheric oxygen but was much larger in times of low atmospheric O(2) or widespread marine anoxia. Waxing and waning of a global authigenic carbonate sink helps to explain extreme carbon isotope variations in the Proterozoic, Paleozoic, and Triassic.

Carbon isotope records in a Mesoproterozoic epicratonic sea: Carbon cycling in a low-oxygen world

Carbon isotope profiles of sedimentary strata are widely used as both a tool for stratigraphic correlation and as a mechanism for inferring important changes in Earth's biogeochemical cycles. Chemostratigraphic interpretations, however, often rely on the assumption that the isotopic composition of dissolved inorganic carbon (DIC) in the surface oceans is broadly homogeneous. At times of globally high sea level, when epicratonic (epeiric) environments dominate our sedimentary record, carbon isotope records reveal substantial lateral variability. Here we investigate lateral variability in the marine carbon isotope record from pericratonic to epicratonic environments of the Mesoproterozoic (∼1.1Ga) Atar/El Mreiti Groups of the Taoudeni Basin, West Africa. Restricted-marine epicratonic environments are consistently 2–4‰ lighter than open-marine pericratonic environments, suggesting input of an isotopically light carbon source that preferentially affected epicratonic environments. In contrast to epicratonic environments in the Paleozoic, where input of isotopically light carbon is generally attributed to input of terrestrial organic matter, we suggest that in situ remineralization of organic carbon via anaerobic microbial cycling drove observed isotopic variability. Within epicratonic El Mreiti Group strata, the extent of organic matter remineralization (and thus degree of 13C depletion) is correlated with water depth, and associated with distinct differences in both total organic carbon (TOC) and pyrite concentration, suggesting a potential linkage to both the persistence of anoxia and the availability of sulfate within epicratonic environments. In such settings, the isotopic effects of organic carbon remineralization are potentially enhanced by either methane oxidation following methanogenic decomposition, or the intermittent oxidation of an enhanced dissolved organic carbon (DOC) pool.

Carbon-isotope stratigraphy from terrestrial organic matter through the Monterey event, Miocene, New Jersey margin (IODP Expedition 313)

The stratigraphic utility of carbon-isotope values from terrestrial organic matter is explored for Miocene siliciclastic sediments of the shallow shelf, New Jersey margin, USA (Integrated Ocean Drilling Program [IODP] Expedition 313). These shallow marine strata, rich in terrestrial organic matter, provide a record of deposition equivalent to the Monterey event, a prolonged interval of time characterized by relatively positive carbon-isotope values recorded from foraminiferal carbonate in numerous oceanic settings. Coherent stratigraphic trends and short-term isotopic excursions are observed consistently in palynological preparation residues, concentrated woody phytoclasts, and individually picked woody phytoclasts obtained from the New Jersey sediments. A bulk organic matter curve shows somewhat different stratigraphic trends but, when corrected for mixing of marine-terrestrial components on the basis of measured C/N ratios, a high degree of conformity with the woody phytoclast record is observed. However, assuming that the correlations based on strontium-isotope values and biostratigraphy are correct, the carbon-isotope record from the New Jersey margin contrasts with that previously documented from oceanic settings (i.e., lack of positive excursion of carbon-isotope values in terrestrial organic matter through the Langhian Stage). Factors that may potentially bias local terrestrial carbon-isotope records include reworking from older deposits, degradation and diagenesis, as well as environmental factors affecting vegetation in the sediment source areas. These possible factors are assessed on the basis of pyrolysis data, scanning electron microscope observations, and comparison to palynological indices of environmental change. Some evidence is found for localized degradation and/or reworking of older woody phytoclasts, but where such processes have occurred they do not readily explain the observed carbon-isotope values. It is concluded that the overall carbon-isotope signature for the exchangeable carbon reservoir is distorted, to the extent that the Monterey event excursion is not easily identifiable. The most likely explanation is that phytoclast reworking has indeed occurred in clinoform toe-of-slope facies, but the reason for the resulting relatively heavy carbon-isotope values in the Burdigalian remains obscure.

Facies and climate changes across the Permian–Triassic boundary in the North German Basin: insights from a high-resolution organic carbon isotope record

Abstract The transition from the uppermost Permian Zechstein Group to the lowermost Triassic Lower Buntsandstein Subgroup in the North German Basin is characterized by a shift from sabkha to playa and to fluviatile facies indicative of a shift to a more humid climate and associated with a major reorganization of the sedimentary system. These changes are recorded in a high-resolution carbon isotope profile of bulk organic matter spanning from the upper Zechstein Group of Changhsingian age to the Calvörde Formation of the Lower Buntsandstein Subgroup of Changhsingian–Indusian age. The organic carbon isotopes reflect a varying composition of the organic matter. Dependent on the facies type, which is mainly controlled by humidity, the proportions of cyanobacterial, phytoplankton and land-plant-derived organic matter with differing organic carbon isotope values change in the samples. A negative organic carbon isotope excursion shortly below the supposed Permian–Triassic Boundary (PTB) is interpreted as a horizon rich in isotopically light phytoplankton, representing a perennial playa lake stage. Although certain effects of global carbon cycle perturbations around the PTB on the analysed organic carbon isotope profile cannot be excluded, the facies and climatic changes associated with the PTB events are thought to be more important.

Tracing seafloor methane emissions with benthic foraminifera in the Baiyun Sag of the northern South China Sea

Changes in the concentrations of atmospheric greenhouse gases are an important part of the global climate forcing. The hypothesis that benthic foraminifera are useful proxies of local methane emission from the seafloor has been verified on sediment cores by numerous studies. The calcium carbonate (CaCO3) content and the high-resolution carbon and oxygen isotope composition of the benthic foraminifera from the core 08CF7, from the northeastern Shenhu gas hydrate drilling area in the Baiyun Sag of the northern South China Sea were analyzed, and the benthic foraminifera's evidence for methane release from gas hydrate decomposition are presented here for the first time. Two rapid obvious carbon isotope negative excursions were observed in the oxygen isotope stage boundaries 5d/5c and 6/5e (penultimate deglaciation, about 130 ka) of the cold-to-warm climatic transition period. The largest negative value of delta C-13 is about -2.95 aEuro degrees, and the whole change of carbon and oxygen isotope is strikingly similar and is in consonance with the atmospheric methane concentration recorded by the Vostok ice core and the carbon isotopic record from Lake Baikal. Combining these results with the analysis of the geological conditions of the study area and the fact that gas hydrate exists in the surrounding area, it can be concluded that the carbon isotope negative excursions of the benthic foraminifera in the northern South China Sea are associated with methane release from gas hydrate decomposition due to deglacial climate warming. By recording the episodes of massive gas hydrate decomposition closely linked with the northern hemisphere temperatures during major warming periods, the new delta C-13 record from the Baiyun Sag provides further evidence for the potential impact of gas hydrate reservoir on rapid deglacial rises of atmospheric methane levels.

Recurrent Early Triassic ocean anoxia

The Early Triassic record, from the Smithian stratotype, shows that the organic carbon isotope record from northwest Pangea closely corresponds to major fluctuations in the inorganic carbon records from the Tethys, indicating truly global perturbations of the carbon cycle occurred during this time. Geochemical proxies for anoxia are strongly correlated with carbon isotopes, whereby negative shifts in δ 13 C org are associated with shifts to more anoxic to euxinic conditions, and positive shifts are related to return to more oxic conditions. Rather than by a delayed or prolonged recovery, the Early Triassic is better characterized by a series of aborted biotic recoveries related to shifts back to ocean anoxia, potentially driven by recurrent volcanism.

Late Chalcolithic - Early Bronze Age (5350 to 4000 years BP) carbon isotope record of plant macroremains from an Eastern Anatolian archaeological site

Late Chalcolithic - Early Bronze Age (5350 to 4000 years BP) carbon isotope record of plant macroremains from an Eastern Anatolian archaeological site

A new high-resolution δ13C record for the Early Triassic: Insights from the Arabian Platform

A new carbon isotope record with conodont biostratigraphy is presented for the entire Early Triassic from the Musandam Peninsula, United Arab Emirates (UAE). This is a near-continuous and exclusively shallow marine carbonate succession that allows analysis of a high-resolution primary carbon cycling signature in the absence of significant depth-dependent or lithologic controls. The Musandam carbon isotope record can be broadly correlated with global isotopic events but also resolves additional features, including the presence of significant negative events during the previously identified positive excursions at both the Dienerian/Smithian and Smithian/Spathian boundaries. A further positive event is revealed during the development of the mid-Spathian negative excursion, a feature not previously reported in any other section. These new short-lived events are probably related to the occurrence of the more widely recognized Early Triassic excursions, and may represent fluctuations in the driving mechanisms superimposed on the continued instability of the global carbon cycle in the aftermath of the end-Permian extinction. Together, these features highlight additional complexities to the Early Triassic carbon cycle perturbations than previously documented.

What does leaf wax δD from a mixed C3/C4 vegetation region tell us?

Hydrogen isotope values (δD) of sedimentary terrestrial leaf wax such as n-alkanes or n-acids have been used to map and understand past changes in rainfall amount in the tropics because δD of precipitation is commonly assumed as the first order controlling factor of leaf wax δD. Plant functional types and their photosynthetic pathways can also affect leaf wax δD but these biological effects are rarely taken into account in paleo studies relying on this rainfall proxy. To investigate how biological effects may influence δD values we here present a 37,000-year old record of δD and stable carbon isotopes (δ13C) measured on four n-alkanes (n-C27, n-C29, n-C31, n-C33) from a marine sediment core collected off the Zambezi River mouth. Our paleo δ13C records suggest that each individual n-alkanes had different C3/C4 proportional contributions. n-C29 was mostly derived from a C3 dicots (trees, shrubs and forbs) dominant vegetation throughout the entire record. In contrast, the longer chain n-C33 and n-C31 were mostly contributed by C4 grasses during the Glacial period but shifted to a mixture of C4 grasses and C3 dicots during the Holocene. Strong correlations between δD and δ13C values of n-C33 (correlation coefficient R2=0.75, n=58) and n-C31 (R2=0.48, n=58) suggest that their δD values were strongly influenced by changes in the relative contributions of C3/C4 plant types in contrast to n-C29 (R2=0.07, n=58). Within regions with variable C3/C4 input, we conclude that δD values of n-C29 are the most reliable and unbiased indicator for past changes in rainfall, and that δD and δ13C values of n-C31 and n-C33 are sensitive to C3/C4 vegetation changes. Our results demonstrate that a robust interpretation of palaeohydrological data using n-alkane δD requires additional knowledge of regional vegetation changes from which n-alkanes are synthesized, and that the combination of δD and δ13C values of multiple n-alkanes can help to differentiate biological effects from those related to the hydrological cycle.

Atteinte cutanée dans la sclérose tubéreuse de Bourneville : intérêt de l’expansion cutanée

In Central and NW Europe, the transition from the Permian to the Triassic (i.e., the Zechstein–Buntsandstein boundary interval) is developed mainly in red bed facies. This continental sedimentary succession is marked by relatively high sedimentation rates providing a high temporal resolution favorable for magnetic polarity stratigraphy. Here, we present a Zechstein to Lower Buntsandstein magnetostratigraphy obtained from the c. 100 m thick Everdingen-1 core from the Netherlands. Seven magnetozones (EV1n to EV4n) and five submagnetozones (EV1n.1r to EV3r.1n) have been delineated. The Everdingen-1 magnetostratigraphy has been integrated into the well-established high-resolution Zechstein–Buntsandstein stratigraphic framework, and verifies the geomagnetic polarity record from Central Germany. This confirms the hypothesis of nearly synchronous base-level cycles within the interior of the Central European Basin. These cycles are related to solar-induced ~ 100 ka eccentricity cycles. The most distinctive feature of the Everdingen-1 magnetostratigraphy is a transition from a thin reverse to a thick dominantly normal magnetic polarity interval. This reversal predates both the terrestrial mass extinction, which is indicated by a palynofloral turnover and a major sediment provenance change at the base of the Buntsandstein, and the marine Permian–Triassic Boundary (PTB). The PTB is located within the lowermost Buntsandstein and is approximated by the last occurrence of the conchostracan Falsisca postera and a negative excursion in the carbon isotope record. According to the Buntsandstein cyclostratigraphy, the R/N reversal predates the marine end-Permian extinction event by about 0.1 Ma and the marine biostratigraphic PTB by about 0.2 Ma. The thick normal magnetozone is estimated to have lasted c. 700 ka, and roughly coincides with the main phase of Siberian Trap volcanism.

A multiple sulfur and organic carbon isotope record from non-conglomeratic sedimentary rocks of the Mesoarchean Witwatersrand Supergroup, South Africa

Multiple sulfur isotope ratios (36S/34S/33S/32S) and organic carbon isotope ratios (13C/12C) were measured from 198 non-conglomeratic sedimentary samples that were collected from five deep diamond drill-cores that cover the majority of the ca. 2.96–2.82Ga Witwatersrand Supergroup. δ13Corg, δ34Spy and Δ33Spy values of the sample set range from −44.3 to −21.9‰, −3.7 to +16.5‰ and −4.0 to +1.9‰, respectively. These geochemical data vary relative to depositional facies (proximal marine, distal marine and fluvial-dominated) and tectonic setting (trailing margin and foreland basin).In the trailing margin setting of the ∼2.96Ga Hospital Hill Subgroup, the proximal marine depofacies is characterized by relatively high organic carbon contents (up to 0.9wt.%) and δ13Corg values around −28‰, in contrast to the distal marine depofacies that yields low organic carbon contents (0.01wt.%) and high δ13Corg values (up to −22‰). Both depofacies yield low sulfur contents (0.02wt.‰), a narrow range of δ34S values (∼+3±2‰) and positive Δ33S values (up to +1.9‰). This data is consistent with photoautotrophic carbon fixation in shallow marine environments and limited organic carbon production/preservation in deeper water settings due to longer transport distances and effective biological degradation (e.g., Fe-reducing microbes). Positive Δ33S values imply that sulfur was largely derived from a photochemical elemental sulfur reservoir. In the foreland basin tectonic setting of the ∼2.94Ga Government and ∼2.92Ga Jeppestown subgroups, shelf deposits associated with fluvial braidplain depofacies are characterized by 13C-depleted organic carbon (∼−44 to −38‰), relatively high sulfur contents (0.2–1.3wt.%), variable δ34S values (−3.7 to +16.5‰) and small negative Δ33S values (∼−0.4‰). These data suggest that the microbial community in the fluvial-dominated depofacies may have consisted of photoautotrophs, methanogens, anaerobic methanotrophs and sulfate reducers. Sulfate was derived from a variety of sources that include photochemical, crustal and marine sulfur reservoirs.The occurrence of three regionally persistent diamictite deposits in the Government Subgroup coincides with the onset of compressional tectonics and development of pyritic shales with highly 13C-depleted organic carbon, suggesting that an increase in continental sulfur flux and methane oxidation may have triggered the Mesoarchean glaciations (drawdown of H2 and CH4). However, the link between large Δ33S anomalies (−4.0 to +1.2‰) and diamictite suggests low levels of atmospheric oxygen and minimal dilution of photochemical signatures.

A high-resolution stable isotopic record from the Junggar Basin (NW China): Implications for the paleotopographic evolution of the Tianshan Mountains

This study presents high-resolution oxygen and carbon isotopic records of paleosol carbonates from fluvial sediments and lacustrine carbonates, sampled from the Jingou He and Kuitun He stratigraphic sections, located in the northern Tianshan piedmont. These sections expose remarkable outcrops of Junggar foreland basin sediments that have been previously dated by high-resolution magnetostratigraphy to between ∼23.6 and ∼1Ma, and ∼10.5 and ∼3.1Ma. A total of 216 samples of fluvio-lacustrine sediments were collected from which isotopic analyses yield δ18O (SMOW) values that range from 13.7‰ to 29.9‰ in the Jingou He section, and 16.3‰ to 21.0‰ in the Kuitun He section. δ13C (PDB) values range from −12.9‰ to 3.0‰ in the Jingou He section and from −7.8‰ to −4.0% in the Kuitun He section. δ18O values decrease between ∼25 and 23Ma, and then remain relatively steady, with the exception of one period that contains samples with higher oxygen isotope values at ∼16Ma. During the periods when there are samples that overlap in time from the Kuitun He and Jingou He sections, we observe a difference of ∼1.7% between values from the two locales. The δ13C values also decrease between ∼25 and 23Ma, and then remain relatively steady until ∼10Ma with, again, one short period of higher values at ∼16Ma. Then, between ∼10 and 3.1Ma, carbon isotope values progressively increase. We interpret that δ18O and δ13C isotopic values during lacustrine periods (∼25–23Ma and ∼16Ma) as largely controlled by evaporation and opening/closing of the lake to external inputs. We interpret the δ18O values of paleosol carbonate in the Junggar Basin to be influenced by the hypsometry of the high Tianshan range while the δ13C values may record the uplift history of the depositional area in the foreland basin itself as well as the isotopic composition of plants. Consequently, we conclude that the Jingou He and Kuitun He drainage basins in the Central Tianshan have remained at relatively unchanged elevations for the past ∼20Ma. We also suggest that the elevation of the southern part of the foreland basin increased between ∼10 and ∼3.1Ma, probably as a result of tectonic deformation in the piedmont and sedimentary filling of the sedimentary basin. The carbon isotope record remains relatively stable through time, and isotopic values suggest that there was little or no expansion of C4 plants in this region in the late Miocene.

Carbon isotopic record of terrestrial ecosystems spanning the Late Miocene extinction of Oreopithecus bambolii, Baccinello Basin (Tuscany, Italy)

Oreopithecus bambolii is a Late Miocene hominoid with an extensive fossil record in the Baccinello Basin (Tuscany, Italy), and was the only western European hominoid to survive a major extinction event ca. 9.6 Ma (millions of years ago). Oreopithecus lived in the insular Tusco-Sardinian paleobioprovince, where it evolved many unique anatomical specializations that make it important for understanding the mechanisms and history of Late Miocene hominoid evolution. The eventual extinction of Oreopithecus and its associated fauna ca. 6.5 Ma has generally been attributed to interaction with species that arrived from continental Europe following tectonic collision of the Tusco-Sardinian province with mainland Italy, but palynological, paleontological, and sedimentological records indicate an environmental shift toward more variable climate across the extinction event.To explore the possibility of environmental change as a contributing factor in the extinction of Oreopithecus, we developed a stable carbon and oxygen isotope record from organic matter in paleosols from the Baccinello Basin. These data show very low temporal and spatial variability (indicating plant ecosystem stability through time and space) and provide no evidence for ecologically significant changes in floral composition spanning the extinction event, suggesting that environmental change was not an underlying cause for the extinction of Oreopithecus and its associated fauna. The carbon isotope values fall entirely within the range of isotopic variability for modern plants following the C3 photosynthetic pathway (trees, shrubs, cool-season grasses), indicating that C4 vegetation (warm-season grasses) was not an important component of biomass. When corrected for temporal variation in the carbon isotopic composition of atmospheric carbon dioxide, the paleosol carbon isotope values are consistent with predicted values based on modern plants and the Baccinello palynoflora, supporting the reliability of paleosol isotopic records as paleoecological proxies.

Mid-Ludfordian coeval carbon isotope, natural gamma ray and magnetic susceptibility excursions in the Mielnik IG-1 borehole (Eastern Poland)—Dustiness as a possible link between global climate and the Silurian carbon isotope record

The graptolite-bearing upper Silurian succession of the Mielnik IG-1 borehole (eastern Poland) represents a periplatform setting on a neritic carbonate platform located on the palaeocontinent of Baltica and records widely recorded positive mid-Ludfordian Carbon Isotope Excursion (CIE). The initial increase of δ13C values occurs in the uppermost part of the Neocucullograptus kozlowskii Zone whereas pronounced increase and maximal values (+6.74‰) are noted in the N. kozlowskii–Pseudomonoclimacis latilobus interzone (Pristiograptus dubius bloom interval). The thickness–time relation in the section indicates that the main, initial shift in carbon isotope ratio (of 2.7‰) occurred over a very short time, estimated to be around 4000years, and is coeval with a rapid initiation of deposition of rock-forming, silt-sized detrital dolomite and quartz. The CIE decline is interpreted as steeper than in inner shelf sections, and is coincident with a flooding event in the Ps. latilobus–Slovinograptus balticus Zone; whereas the end of the excursion is coeval with the next flooding surface marked by the Ps. Latilobus–Uncinatograptus acer graptolite assemblage. Combined SGR (Spectral Gamma Ray), facies, and faunal records during the CIE suggest prolonged sea-level lowstand conditions. The abundant detrital material (‘dolomite siltstone facies’), occurring exclusively in the CIE interval, is noted in microfacies as well as in the geophysics record—as pronounced negative excursions in total natural gamma ray and magnetic susceptibility, both resulting from dilution by diamagnetic and low-radioactivity minerals. The perfectly sorted, vertically equally-sized silt material contains unique, constant and low diversified grain assemblage (euhedral dolomite, quartz, minute ooids)—suggesting its provenance exclusively from the shallower and/or emerged parts of the carbonate platform interior. The spot findings of graptolites and nautiloids along with delicate parallel lamination of sediments indicates relatively deep environment, with absence of traction processes. These features, along with the lack of dolomite detritus in accompanying redeposited carbonates, suggest its derivation by wind. With regard to the earlier noted presence of aeolian detritus in the middle Ludfordian, we suggest dustiness as a plausible driving force of the CIE. In the hypothesis proposed, bioavailable Fe-bearing dust inflow in concert with antiestuarine circulation on shelfs, caused nutrient (N:P ratio) disturbances, resulting in methanogenesis in surface layer of the seas. The surface layer methanogenesis should resulting in bathymetric gradient of isotope fractionation, what is consistent with the CIE record. Coincidence of sea-level lowstand, low-latitude aridity, and gustiness of the global climate, are in accordance with the hypothetical short-lived glaciation in mid-Ludfordian time.

Palynology of the Lower Triassic succession of Tulong, South Tibet — Evidence for early recovery of gymnosperms

The thermally altered but otherwise well preserved Early Triassic palynomorphs from the Tulong area (South Tibet) allowed for qualitative and quantitative analyses and the differentiation of two distinct palynofloras, a Smithian lycopod-dominated flora and a Spathian gymnosperm-dominated flora. This suggests that gymnosperm vegetation recovered about 2Ma after the end-Permian event on the subtropical North Indian Margin. Together with previously described successions from Pakistan, Australia, and Norway the new palynofloral record suggests an earlier establishment of diverse, gymnosperm-rich plant communities after the end-Permian event than previously proposed. The observed change in the ratio of the two major plant groups (pteridophytes/gymnosperms) in these two assemblages supports the global extent of a major climate change near the Smithian–Spathian boundary. The observed palynofloral patterns are closely related to the changes in the carbon isotope record, which suggests that the floral recovery dynamics were linked to environmental conditions.

High-resolution carbon-isotope stratigraphy across the Campanian–Maastrichtian boundary at Shatsky Rise (tropical Pacific)

The Campanian–Maastrichtian transition is characterized by a negative carbon-isotope excursion, the so-called Campanian–Maastrichtian Boundary Event (CMBE), thought to have been triggered by climatic cooling and sea-level fall. This event is known from stable isotope datasets around the world, but little is known about the causal mechanisms of the proposed cooling or the exact timing of this event. A tool both to enhance our knowledge about this event and to highlight the relative timing between the cooling and the proposed sea-level fall, is high-resolution carbon-isotope stratigraphy. In this study, an upper Campanian–Maastrichtian high-resolution carbon-isotope record from bulk carbonates of Ocean Drilling Program Hole 1210B at Shatsky Rise is presented. The new carbon-isotope record shows a number of distinct variations on short and longer time scales, which can be calibrated with age-diagnostic planktonic foraminifera and calcareous nannoplankton datum levels. This detailed biostratigraphically calibrated carbon-isotope stratigraphy can be correlated with the carbon-isotope record of Deep Sea Drilling Project Site 305 (∼500m deeper in palaeodepth than Hole 1210B). One result of this correlation is the detection of two major hiatuses at Site 305 associated with the lower and upper part of the CMBE. As possible mechanisms for these hiatuses, we discuss the effects of erosion as a result of mass wasting and/or of changes in the strength of bottom currents. By reducing stratigraphic uncertainties our new correlation proves the usefulness of biostratigraphically calibrated carbon-isotope stratigraphy, even for time intervals of small changes in the global carbon cycle as in the late Campanian–Maastrichtian. The new carbon-isotope record of Hole 1210B may serve in future as a reference for detailed calibration and correlation with other well-established δ13C records from shelf seas and open-ocean settings. This will help to enhance our understanding of ocean-climate processes associated with the CMBE.

No causal link between terrestrial ecosystem change and methane release during the end-Triassic mass extinction

Research Article| June 01, 2012 No causal link between terrestrial ecosystem change and methane release during the end-Triassic mass extinction Sofie Lindström; Sofie Lindström * 1GEUS (Geological Survey of Denmark and Greenland), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark *E-mail: sli@geus.dk. Search for other works by this author on: GSW Google Scholar Bas van de Schootbrugge; Bas van de Schootbrugge 2Institute of Geosciences, Goethe University Frankfurt, Altenhöferallee 1, D-60438 Frankfurt, Germany Search for other works by this author on: GSW Google Scholar Karen Dybkjær; Karen Dybkjær 1GEUS (Geological Survey of Denmark and Greenland), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Search for other works by this author on: GSW Google Scholar Gunver Krarup Pedersen; Gunver Krarup Pedersen 3Department of Geography and Geology, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Search for other works by this author on: GSW Google Scholar Jens Fiebig; Jens Fiebig 2Institute of Geosciences, Goethe University Frankfurt, Altenhöferallee 1, D-60438 Frankfurt, Germany Search for other works by this author on: GSW Google Scholar Lars Henrik Nielsen; Lars Henrik Nielsen 1GEUS (Geological Survey of Denmark and Greenland), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Search for other works by this author on: GSW Google Scholar Sylvain Richoz Sylvain Richoz 4CPSOE, Austrian Academy of Science, c/o University of Graz, Heinrichstrasse 26, 8020 Graz, Austria Search for other works by this author on: GSW Google Scholar Author and Article Information Sofie Lindström * 1GEUS (Geological Survey of Denmark and Greenland), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Bas van de Schootbrugge 2Institute of Geosciences, Goethe University Frankfurt, Altenhöferallee 1, D-60438 Frankfurt, Germany Karen Dybkjær 1GEUS (Geological Survey of Denmark and Greenland), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Gunver Krarup Pedersen 3Department of Geography and Geology, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Jens Fiebig 2Institute of Geosciences, Goethe University Frankfurt, Altenhöferallee 1, D-60438 Frankfurt, Germany Lars Henrik Nielsen 1GEUS (Geological Survey of Denmark and Greenland), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark Sylvain Richoz 4CPSOE, Austrian Academy of Science, c/o University of Graz, Heinrichstrasse 26, 8020 Graz, Austria *E-mail: sli@geus.dk. Publisher: Geological Society of America Received: 17 Oct 2011 Revision Received: 29 Dec 2011 Accepted: 11 Jan 2012 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2012 Geological Society of America Geology (2012) 40 (6): 531–534. https://doi.org/10.1130/G32928.1 Article history Received: 17 Oct 2011 Revision Received: 29 Dec 2011 Accepted: 11 Jan 2012 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Sofie Lindström, Bas van de Schootbrugge, Karen Dybkjær, Gunver Krarup Pedersen, Jens Fiebig, Lars Henrik Nielsen, Sylvain Richoz; No causal link between terrestrial ecosystem change and methane release during the end-Triassic mass extinction. Geology 2012;; 40 (6): 531–534. doi: https://doi.org/10.1130/G32928.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Profound changes in both marine and terrestrial biota during the end-Triassic mass extinction event and associated successive carbon cycle perturbations across the Triassic-Jurassic boundary (T-J, 201.3 Ma) have primarily been attributed to volcanic emissions from the Central Atlantic Magmatic Province and/or injection of methane. Here we present a new extended organic carbon isotope record from a cored T-J boundary succession in the Danish Basin, dated by high-resolution palynostratigraphy and supplemented by a marine faunal record. Correlated with reference C-isotope and biotic records from the UK, it provides new evidence that the major biotic changes, both on land and in the oceans, commenced prior to the most prominent negative C-isotope excursion. If massive methane release was involved, it did not trigger the end-Triassic mass extinction. Instead, this negative C-isotope excursion is contemporaneous with the onset of floral recovery on land, whereas marine ecosystems remained perturbed. The decoupling between ecosystem recovery on land and in the sea is more likely explained by long-term flood basalt volcanism releasing both SO2 and CO2 with short- and long-term effects, respectively. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The Ice Age Carbon Puzzle

A carbon isotope record helps to explain why carbon dioxide concentrations change during ice age cycles.

Stable isotopic evidence for climate and basin evolution of the Late Cretaceous Songliao basin, China

Because of the need to understand the links and feedbacks of the carbon cycle during times of global greenhouse conditions numerous studies have focused on the Cretaceous climate. Much of what we know about this warm period in Earth's history comes from the study of ocean sediments recovered from both ocean drill cores and marine sediments exposed at the Earth's surface. In contrast, there are few studies of Cretaceous terrestrial sediments. The Songliao basin located in northeast China offers a unique opportunity to understand Cretaceous paleoclimate of terrestrial settings because it contains a nearly complete record of lacustrine sediments deposited throughout the Cretaceous and there is an active drilling program to recover core from this paleolake. We present carbon, oxygen and strontium isotopic data from ostracods collected from two drill cores (SK-1 (N) and SK-1 (S)) that cover a time interval that extends from the Turonian through the Maastrichtian. These data record robust isotopic trends with numerous carbon and oxygen isotope shifts that are both rapid and long-term. We tentatively interpret this record to reflect changes in both global climate and regional basin evolution. In the Turonian and Coniacian Qingshankou Formation we observe several carbon isotope shifts that appear to be correlative to marine isotopic records based upon timing and magnitude of the isotopic changes. We suggest that the carbon isotope record in the Songliao basin reflect the decrease in carbon isotope ratios following the strong positive excursion at the Cenomanian/Turonian boundary, a positive isotope excursion in the late Turonian, and the negative isotope shift that occurs at the Turonian/Coniacian boundary. Upward in the section, however, the marine and Songliao isotopic records diverge as sediment sources shift from the southwest, east and north to more northerly. Strontium isotopes record the change in source region as they increase markedly between the Coniacian/Santonian Yaojia and Santonian/Campanian Nenjiang Formations. As this is the first isotopic record of the Songliao basin we are cautious about many of our interpretations of these isotopic data. Yet it is clear that with tighter age constraints and focused sampling centered on many of the isotope excursions presented here will allow for a deeper understanding of the terrestrial response to changing climate and the hydrologic response to basin evolution.