202 results on '"James C Zachos"'
Search Results
2. North Atlantic Drift Sediments Constrain Eocene Tidal Dissipation and the Evolution of the Earth-Moon System
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David De Vleeschouwer, Donald E. Penman, Simon D'haenens, Fei Wu, Thomas Westerhold, Maximilian Vahlenkamp, Carlotta Cappelli, Claudia Agnini, Wendy E. C. Kordesch, Daniel J. King, Robin van der Ploeg, Heiko Pälike, Sandra Kirtland Turner, Paul Wilson, Richard D. Norris, James C. Zachos, Steven M. Bohaty, Pincelli M. Hull, De Vleeschouwer, David, Penman, Donald E., D'HAENENS, Simon, Wu, Fei, Westerhold, Thomas, Vahlenkamp, Maximilian, Cappelli, Carlotta, Agnini, Claudia, Kordesch, Wendy E. C., King, Daniel J., van der Ploeg, Robin, Pälike, Heiko, Turner, Sandra Kirtland, Wilson, Paul, Norris, Richard D., Zachos, James C., Bohaty, Steven M., Hull, Pincelli M., Marine palynology and palaeoceanography, Stratigraphy & paleontology, D'haenens, Simon/0000-0003-1248-3188, King, Dan/0000-0001-7366-632X, Zachos, James C/0000-0001-8439-1886, D'haenens, Simon/0000-0003-1248-3188, Agnini, Claudia/0000-0001-9749-6003, De, Vleeschouwer, David/0000-0002-3323-807X, Penman, Donald E. E., King, Daniel J. J., Palike, Heiko, Zachos, James C. C., Bohaty, Steven M. M., Hull, Pincelli M. M., Penman, Donald, Kordesch, Wendy, King, Daniel, Kirtland Turner, Sandra, Norris, Richard, Zachos, James, Bohaty, Steven, and Hull, Pincelli
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History ,Atmospheric Science ,Stratigraphy ,Climate ,Palaeontology ,Cyclostratigraphy ,Paleontology ,Geology ,Sedimentology ,Oceanography ,Astronomical calibration ,Middle eocene ,Insolation quantities ,Circulation ,Geochemistry ,Timescale ,Solar-system ,Stability - Abstract
Cyclostratigraphy and astrochronology are now at the forefront of geologic timekeeping. While this technique heavily relies on the accuracy of astronomical calculations, solar system chaos limits how far back astronomical calculations can be performed with confidence. High-resolution paleoclimate records with Milankovitch imprints now allow reversing the traditional cyclostratigraphic approach: Middle Eocene drift sediments from Newfoundland Ridge are well-suited for this purpose, due to high sedimentation rates and distinct lithological cycles. Per contra, the stratigraphies of Integrated Ocean Drilling Program Sites U1408-U1410 are highly complex with several hiatuses. Here, we built a two-site composite and constructed a conservative age-depth model to provide a reliable chronology for this rhythmic, highly resolved (
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- 2023
3. Calcium isotope composition of Morozovella over the late Paleocene–early Eocene
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Andrew D. Jacobson, James C Zachos, Dustin T Harper, Matthew T. Hurtgen, Gabriella D. Kitch, and Bradley B. Sageman
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Isotopes of calcium ,010504 meteorology & atmospheric sciences ,Geochemistry ,Geology ,Composition (visual arts) ,010502 geochemistry & geophysics ,01 natural sciences ,0105 earth and related environmental sciences - Abstract
Ocean acidification (OA) during the Paleocene-Eocene thermal maximum (PETM) likely caused a biocalcification crisis. The calcium isotope composition (δ44/40Ca) of primary carbonate producers may be sensitive to OA. To test this hypothesis, we constructed the first high-resolution, high-precision planktic foraminiferal δ44/40Ca records before and across the PETM. The records employ specimens of Morozovella spp. collected from Ocean Drilling Program Sites 1209 (Shatsky Rise, Pacific Ocean) and 1263 (Walvis Ridge, Atlantic Ocean). At Site 1209, δ44/40Ca values start at −1.33‰ during the Upper Paleocene and increase to a peak of −1.15‰ immediately before the negative carbon isotope excursion (CIE) that marks the PETM onset. Values remain elevated through the PETM interval and decrease into the earliest Eocene. A shorter-term record for Site 1263 shows a similar trend, although δ44/40Ca values are on average 0.22‰ lower and decrease shortly after the CIE onset. The trends support neither diagenetic overprinting, authigenic carbonate additions, nor changes in the δ44/40Ca value of seawater. Rather, they are consistent with a kinetic isotope effect, whereby calcite δ44/40Ca values inversely correlate with precipitation rate. Geologically rapid Ca isotope shifts appear to reflect the response of Morozovella to globally forced changes in the local carbonate geochemistry of seawater. All data combined suggest that the PETM-OA event occurred near the peak of a gradual reduction in seawater carbonate ion concentrations during a time of elevated atmospheric pCO2, potentially driven by North Atlantic igneous province emplacement.
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- 2021
4. Surface ocean warming and acidification driven by rapid carbon release precedes Paleocene-Eocene Thermal Maximum
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Tali L. Babila, Donald E. Penman, Christopher D. Standish, Monika Doubrawa, Timothy J. Bralower, Marci M. Robinson, Jean M. Self-Trail, Robert P. Speijer, Peter Stassen, Gavin L. Foster, and James C. Zachos
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ATLANTIC ,Multidisciplinary ,Science & Technology ,IMPACT ,Multidisciplinary Sciences ,CLIMATE ,CONTINENTAL-SHELF ,DELTA-B-11 ,METHANE ,Science & Technology - Other Topics ,PROXY DATA ,ISOTOPIC COMPOSITION ,TEMPERATURE ,RECORDS - Abstract
The Paleocene-Eocene Thermal Maximum (PETM) is recognized by a major negative carbon isotope (δ 13 C) excursion (CIE) signifying an injection of isotopically light carbon into exogenic reservoirs, the mass, source, and tempo of which continue to be debated. Evidence of a transient precursor carbon release(s) has been identified in a few localities, although it remains equivocal whether there is a global signal. Here, we present foraminiferal δ 13 C records from a marine continental margin section, which reveal a 1.0 to 1.5‰ negative pre-onset excursion (POE), and concomitant rise in sea surface temperature of at least 2°C and a decline in ocean pH. The recovery of both δ 13 C and pH before the CIE onset and apparent absence of a POE in deep-sea records suggests a rapid (< ocean mixing time scales) carbon release, followed by recovery driven by deep-sea mixing. Carbon released during the POE is therefore likely more similar to ongoing anthropogenic emissions in mass and rate than the main CIE.
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- 2022
5. Astrochronology of the Paleocene-Eocene Thermal Maximum on the Atlantic Coastal Plain
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Mingsong Li, Timothy J. Bralower, Lee R. Kump, Jean M. Self-Trail, James C. Zachos, William D. Rush, and Marci M. Robinson
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Carbon Isotopes ,Multidisciplinary ,Earth, Planet ,General Physics and Astronomy ,Calcium ,Seawater ,General Chemistry ,Hydrogen-Ion Concentration ,General Biochemistry, Genetics and Molecular Biology - Abstract
The chronology of the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma) remains disputed, hampering complete understanding of the possible trigger mechanisms of this event. Here we present an astrochronology for the PETM carbon isotope excursion from Howards Tract, Maryland a paleoshelf environment, on the mid-Atlantic Coastal Plain. Statistical evaluation of variations in calcium content and magnetic susceptibility indicates astronomical forcing was involved and the PETM onset lasted about 6 kyr. The astrochronology and Earth system modeling suggest that the PETM onset occurred at an extreme in precession during a maximum in eccentricity, thus favoring high temperatures, indicating that astronomical forcing could have played a role in triggering the event. Ca content data on the paleo-shelf, along with other marine records, support the notion that a carbonate saturation overshoot followed global ocean acidification during the PETM.
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- 2022
6. Ice retreat in Wilkes Basin of East Antarctica during a warm interglacial
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Gavin Piccione, Brandon Cheney, James C Zachos, J. T. Babbe, G. H. Edwards, Bernard Hallet, Slawek Tulaczyk, M. Scudder, Terrence Blackburn, and Noah McLean
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geography ,Multidisciplinary ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Pleistocene ,General Science & Technology ,Antarctic ice sheet ,Structural basin ,010502 geochemistry & geophysics ,01 natural sciences ,Climate Action ,Current (stream) ,Oceanography ,Stage (stratigraphy) ,Interglacial ,Ice sheet ,Geology ,Sea level ,0105 earth and related environmental sciences - Abstract
Efforts to improve sea level forecasting on a warming planet have focused on determining the temperature, sea level and extent of polar ice sheets during Earth’s past interglacial warm periods1–3. About 400,000 years ago, during the interglacial period known as Marine Isotopic Stage 11 (MIS11), the global temperature was 1 to 2 degrees Celsius greater2 and sea level was 6 to 13 metres higher1,3. Sea level estimates in excess of about 10 metres, however, have been discounted because these require a contribution from the East Antarctic Ice Sheet3, which has been argued to have remained stable for millions of years before and includes MIS114,5. Here we show how the evolution of 234U enrichment within the subglacial waters of East Antarctica recorded the ice sheet’s response to MIS11 warming. Within the Wilkes Basin, subglacial chemical precipitates of opal and calcite record accumulation of 234U (the product of rock–water contact within an isolated subglacial reservoir) up to 20 times higher than that found in marine waters. The timescales of 234U enrichment place the inception of this reservoir at MIS11. Informed by the 234U cycling observed in the Laurentide Ice Sheet, where 234U accumulated during periods of ice stability6 and was flushed to global oceans in response to deglaciation7, we interpret our East Antarctic dataset to represent ice loss within the Wilkes Basin at MIS11. The 234U accumulation within the Wilkes Basin is also observed in the McMurdo Dry Valleys brines8–10, indicating11 that the brine originated beneath the adjacent East Antarctic Ice Sheet. The marine origin of brine salts10 and bacteria12 implies that MIS11 ice loss was coupled with marine flooding. Collectively, these data indicate that during one of the warmest Pleistocene interglacials, the ice sheet margin at the Wilkes Basin retreated to near the precipitate location, about 700 kilometres inland from the current position of the ice margin, which—assuming current ice volumes—would have contributed about 3 to 4 metres13 to global sea levels. Uranium isotopes in subglacial precipitates from the Wilkes Basin of the East Antarctic Ice Sheet reveal ice retreat during a warm Pleistocene interglacial period about 400,000 years ago.
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- 2020
7. Effects of size-dependent sediment mixing on deep-sea records of the Paleocene-Eocene Thermal Maximum
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Timothy J. Bralower, Brittany N. Hupp, James C Zachos, and D. Clay Kelly
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010504 meteorology & atmospheric sciences ,Carbon isotope excursion ,Size dependent ,Sediment ,Mineralogy ,Geology ,010502 geochemistry & geophysics ,01 natural sciences ,Deep sea ,Mixing (physics) ,0105 earth and related environmental sciences - Abstract
Stratigraphic features of the carbon isotope excursion (CIE) marking the Paleocene-Eocene Thermal Maximum (PETM; ca. 55.8 Ma) are used to study ocean-climate change and carbon cycling during this ancient global warming event. Yet discrepancies in its timing and amplitude exist between bulk-carbonate and planktic-foraminifera δ13C records. Here we examine these disparities through the lens of δ13C compositions of size-segregated planktic shells across the pre-CIE to CIE transition in the iconic PETM section of Ocean Drilling Program Site 690 in the Weddell Sea. Our results show that the stratigraphic position of the CIE onset is dependent upon shell size, which we attribute to preferential mixing of smaller shells with pre-CIE δ13C values up into the overlying CIE interval. Hence, the transitory loss of size-dependent δ13C signatures in photosymbiotic planktic foraminifera is a taphonomic artifact, not a geochemical signal of symbiont “bleaching” during the PETM. Our results also indicate that many salient features of the Site 690 bulk-carbonate δ13C record are aberrations caused by size-dependent sediment mixing, and as such, should not be viewed as primary signals of ocean-climate change during what is arguably one of the best ancient analogs for future ocean-climate change.
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- 2019
8. Palaeocene–Eocene Thermal Maximum prolonged by fossil carbon oxidation
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Allison A. Baczynski, Tali L. Babila, James C Zachos, Katherine H. Freeman, Lee R. Kump, S. M. Trampush, Ellen G. Polites, Timothy J. Bralower, Jean M. Self-Trail, Elizabeth Hajek, Jamie R. Vornlocher, and S. L. Lyons
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010504 meteorology & atmospheric sciences ,Earth science ,Climate system ,chemistry.chemical_element ,Sedimentation ,010502 geochemistry & geophysics ,01 natural sciences ,Fossil carbon ,Biomarker (petroleum) ,chemistry ,Carbon isotope excursion ,Erosion ,General Earth and Planetary Sciences ,Environmental science ,Sedimentary rock ,Carbon ,0105 earth and related environmental sciences - Abstract
A hallmark of the rapid and massive release of carbon during the Palaeocene–Eocene Thermal Maximum is the global negative carbon isotope excursion. The delayed recovery of the carbon isotope excursion, however, indicates that CO2 inputs continued well after the initial rapid onset, although there is no consensus about the source of this secondary carbon. Here we suggest this secondary input might have derived partly from the oxidation of remobilized sedimentary fossil carbon. We measured the biomarker indicators of thermal maturation in shelf records from the US Mid-Atlantic coast, constructed biomarker mixing models to constrain the amount of fossil carbon in US Mid-Atlantic and Tanzania coastal records, estimated the fossil carbon accumulation rate in coastal sediments and determined the range of global CO2 release from fossil carbon reservoirs. This work provides evidence for an order of magnitude increase in fossil carbon delivery to the oceans that began ~10–20 kyr after the event onset and demonstrates that the oxidation of remobilized fossil carbon released between 102 and 104 PgC as CO2 during the body of the Palaeocene–Eocene Thermal Maximum. The estimated mass is sufficient to have sustained the elevated atmospheric CO2 levels required by the prolonged global carbon isotope excursion. Even after considering uncertainties in the sedimentation rates, these results indicate that the enhanced erosion, mobilization and oxidation of ancient sedimentary carbon contributed to the delayed recovery of the climate system for many thousands of years. Delivery of fossil carbon to the oceans strongly increased about 15 kyr after the onset of the Palaeocene–Eocene Thermal Maximum as a result of oxidation of sedimentary carbon, suggests an analysis of geochemical measurements with a biomarker mixing model.
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- 2018
9. Evidence for Shelf Acidification During the Onset of the Paleocene‐Eocene Thermal Maximum
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S. L. Lyons, Tali L. Babila, Timothy J. Bralower, Jean M. Self-Trail, Lee R. Kump, William Rush, Katherine H. Freeman, Elizabeth Hajek, Marci M. Robinson, James C Zachos, and Edward Ballaron
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Atmospheric Science ,Paleontology ,010504 meteorology & atmospheric sciences ,Carbon isotope excursion ,Environmental science ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,0105 earth and related environmental sciences - Abstract
A transect of paleoshelf cores from Maryland and New Jersey contains an ~0.19‐ to 1.61‐m‐thick interval with reduced percentages of carbonate during the onset of the Paleocene‐Eocene Thermal Maximum (PETM). Outer paleoshelf cores are barren of nannofossils and correspond to two minor disconformities. Middle paleoshelf cores contain a mixture of samples devoid of nannofossils and those with rare specimens characterized by significant dissolution (i.e., etching). The magnitude of the decrease in carbonate cannot be explained by dilution by clastic material or dissolution resulting from the oxidation of organic matter during early diagenesis. The observed preservation pattern implies a shoaling of the calcite compensation depth and lysocline to the middle shelf. This reduced carbonate interval is observed during the onset of the PETM on other continental margins raising the possibility that extreme shoaling of the calcite compensation depth and lysocline was a global signal, which is more significant than in previous estimates for the PETM. An alternative scenario is that shoaling was restricted to the northwest Atlantic, enhanced by regional and local factors (eutrophication from rivers and microbial activity associated with warming) that exacerbated the impact of acidification on the shelf.
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- 2018
10. The Habitat of the Nascent Chicxulub Crater
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Bettina Schaefer, Kliti Grice, S. L. Lyons, Si Athena Chen, G. Turner‐Walker, Timothy J. Bralower, Sonia M. Tikoo, Kenneth A. Farley, Cornelia Rasmussen, Christopher M. Lowery, Vivi Vajda, Axel Wittmann, Heather L. Jones, Joshua M. Garber, Elizabeth Hajek, J. L. Gray, Charles S. Cockell, Sean P. S. Gulick, Joanna Morgan, David A. Kring, Katherine H. Freeman, Peter J. Heaney, Marco J. L. Coolen, Natalia Artemieva, J. Carte, Benjamin H. Passey, Michael T. Whalen, James C Zachos, Steven Goderis, F. J. Rodríguez Tovar, Elizabeth C Sibert, Julie Cosmidis, M. Gonzalez, Jan Smit, M. S. Fantle, and Natural Environment Research Council (NERC)
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Chicxulub impact ,Palaeoenvironment ,Cretaceous–Paleogene boundary ,Boundary (topology) ,Annan geovetenskap och miljövetenskap ,General Medicine ,K-Pg boundary ,Paleontology ,Habitat ,Impact crater ,Section (archaeology) ,Sedimentary rock ,Mexico ,Geology ,Other Earth and Related Environmental Sciences - Abstract
An expanded sedimentary section provides an opportunity to elucidate conditions in the nascent Chicxulub crater during the hours to millennia after the Cretaceous‐Paleogene (K‐Pg) boundary impact. The sediments were deposited by tsunami followed by seiche waves as energy in the crater declined, culminating in a thin hemipelagic marlstone unit that contains atmospheric fallout. Seiche deposits are predominantly composed of calcite formed by decarbonation of the target limestone during impact followed by carbonation in the water column. Temperatures recorded by clumped isotopes of these carbonates are in excess of 70°C, with heat likely derived from the central impact melt pool. Yet, despite the turbidity and heat, waters within the nascent crater basin soon became a viable habitat for a remarkably diverse cross section of the food chain. The earliest seiche layers deposited with days or weeks of the impact contain earliest Danian nannoplankton and dinocyst survivors. The hemipelagic marlstone representing the subsequent years to a few millennia contains a nearly monogeneric calcareous dinoflagellate resting cyst assemblage suggesting deteriorating environmental conditions, with one interpretation involving low light levels in the impact aftermath. At the same horizon, microbial fossils indicate a thriving bacterial community and unique phosphatic fossils including appendages of pelagic crustaceans, coprolites and bacteria‐tunneled fish bone, suggesting that this rapid recovery of the base of the food chain may have supported the survival of larger, higher trophic‐level organisms. The extraordinarily diverse fossil assemblage indicates that the crater was a unique habitat in the immediate impact aftermath, possibly as a result of heat and nutrients supplied by hydrothermal activity.
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- 2020
11. Large-scale, astronomically paced sediment input to the North Sea Basin during the Paleocene Eocene Thermal Maximum
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Simin Jin, David B. Kemp, David W. Jolley, Manuel Vieira, James C. Zachos, Chunju Huang, Mingsong Li, and Wenhan Chen
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Geophysics ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) - Published
- 2022
12. Coupled evolution of temperature and carbonate chemistry during the Paleocene–Eocene; new trace element records from the low latitude Indian Ocean
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Leah J. LeVay, Dick Kroon, Dustin T Harper, Kate Littler, Melanie J. Leng, Tali L. Babila, James C Zachos, Clemens V. Ullmann, Kirsty M. Edgar, James S K Barnet, Michael J. Henehan, and University of St Andrews. School of Earth & Environmental Sciences
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010504 meteorology & atmospheric sciences ,Paleoclimate ,Mixed layer ,NDAS ,010502 geochemistry & geophysics ,01 natural sciences ,Carbon cycle ,Foraminifera ,Water column ,Paleoceanography ,Geochemistry and Petrology ,Paleoclimatology ,Earth and Planetary Sciences (miscellaneous) ,SDG 13 - Climate Action ,Indian Ocean ,0105 earth and related environmental sciences ,Trace elements ,GE ,biology ,Trace element ,Ocean acidification ,biology.organism_classification ,Paleocene-Eocene Thermal Maximum ,Geophysics ,Oceanography ,Space and Planetary Science ,Geology ,Paleogene ,GE Environmental Sciences - Abstract
This work was principally funded by a European Consortium for Ocean Research Drilling (ECORD) Research Grant, the International Association of Sedimentologists (IAS) Postgraduate Research Grant Scheme, and the Natural Environment Research Council (NERC) Isotope Geosciences Facility (IP-1581–1115), awarded to James Barnet and Kate Littler. LJL acknowledges funding from the IODP-JRSO (NSF grant 1326927), KME acknowledges funding from NERC grants NE/H016457/1 and NE/P013112/1, and CVU acknowledges funding via NERC grant NE/N018508/1. The early Paleogene represents the most recent interval in Earth's history characterized by global greenhouse warmth on multi-million year timescales, yet our understanding of long-term climate and carbon cycle evolution in the low latitudes, and in particular the Indian Ocean, remains very poorly constrained. Here we present the first long-term sub-eccentricity-resolution stable isotope (δ13C and δ18O) and trace element (Mg/Ca and B/Ca) records spanning the late Paleocene-early Eocene (similar to 58-53 Ma) across a surface-deep hydrographic reconstruction of the northern Indian Ocean, resolving late Paleocene 405-kyr paced cyclicity and a portion of the PETM recovery. Our new records reveal a long-term warming of similar to 4-5 °C at all depths in the water column, with absolute surface ocean temperatures and magnitudes of warming comparable to the low latitude Pacific. As a result of warming, we observe a long-term increase in δ18Osw of the mixed layer, implying an increase in net evaporation. We also observe a collapse in the temperature gradient between mixed layer- and thermocline-dwelling species from similar to 57-54 Ma, potentially due to either the development of a more homogeneous water column with a thicker mixed layer, or depth migration of the Morozovellain response to warming. Synchronous warming at both low and high latitudes, along with decreasing B/Ca ratios in planktic foraminifera indicating a decrease in ocean pH and/or increasing dissolved inorganic carbon, suggest that global climate was forced by rising atmospheric CO2 concentrations during this time. Publisher PDF
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- 2020
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13. The Coupled Evolution of Temperature and Carbonate Chemistry during the Paleocene–Eocene; New Orbital-Resolution Trace Metal Records from the Low-Latitude Indian Ocean
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Tali L. Babila, Leah J. LeVay, Kirsty M. Edgar, James S K Barnet, James C Zachos, Dick Kroon, Melanie J. Leng, Dustin T Harper, Clemens V. Ullmann, and Kate Littler
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Paleontology ,chemistry.chemical_compound ,Indian ocean ,Low latitude ,chemistry ,Carbonate ,Trace metal - Abstract
The “greenhouse” climates of the Paleocene and Eocene have formed the focus for many proxy and modelling studies in recent decades, as they are the closest geological analogues for our future warme...
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- 2020
14. Enhanced Poleward Flux of Atmospheric Moisture to the Weddell Sea Region (ODP Site 690) During the Paleocene‐Eocene Thermal Maximum
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John H. Fournelle, Donald E. Penman, James C Zachos, Daniel Clay Kelly, John W. Valley, and Reinhard Kozdon
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Atmospheric Science ,Atmospheric moisture ,biology ,Paleontology ,Flux ,Oceanography ,Atmospheric sciences ,biology.organism_classification ,Greenhouse climate ,Diagenesis ,Foraminifera ,In situ analysis ,Carbon isotope excursion ,Water cycle ,Geology - Abstract
Author(s): Kozdon, Reinhard; Penman, Donald E; Kelly, DC; Zachos, JC; Fournelle, John H; Valley, JW
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- 2020
15. Perturbation and recovery of shelf ecosystems during the PETM
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Tali L. Babila, Robert P. Speijer, Marci M. Robinson, Peter Stassen, Monika Doubrawa, and James C Zachos
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Oceanography ,Environmental science ,Ecosystem ,Perturbation (geology) - Abstract
During the early Paleogene, a long-term warming trend of Earth’s climate was punctuated by a major global warming event, known as the Paleocene-Eocene Thermal Maximum (PETM) and marked by a carbon isotope excursion (CIE) and an acidification episode. The associated worldwide environmental perturbations are best studied in open marine settings, and resulted in a major extinction event in deep-sea benthic foraminifera, followed by migration and diversification. Yet, the evolutionary impact on shelf foraminiferal faunas is still poorly constrained due the inherent stratigraphic complexities in these environments. In order to understand the prelude and aftermath of peak warming during the PETM, we study the South Dover Bridge core (SDB), drilled in the US Atlantic Coastal Plain in Maryland. Here, the Paleocene-Eocene transition is stratigraphically well constrained by calcareous nannoplankton and stable isotope records. Additionally, the PETM is regionally characterized by the appearance of fine-grained sediments, known as the Marlboro Clay, contrasting with the late Paleocene glauconitic sands. Our newly generated high-resolution foraminiferal stable isotope, biotic and grain size data enable an assessment of the stratigraphic completeness of this site, and the disentanglement of the successive recovery-phases, by correlation across the paleoshelf.The mid-shelf benthic foraminiferal assemblage we recorded in the upper Paleocene indicates well-oxygenated, continuously oligo- to mesotrophic bottom water conditions. These conditions were temporarily interrupted during a pre-PETM CIE, which initiated minor, but prominent, changes in foraminiferal assemblage. The relationship with the PETM is still unclear, but it may indicate that the latest Paleocene climate was not as stable as previously assumed and instead exhibited a more gradual change towards the PETM. At the onset of the PETM diversity decreases, as more stress-resistant benthic taxa become predominant and planktic abundances increase. This probably points to periodically dysoxic bottom waters due to river-induced stratification, resulting from enhanced regional river outflow, as well as to a shift to episodic food fluxes to the sea floor.The studied expanded SDB sequence also presents an excellent and nearly complete record of the PETM isotope recovery phase. Throughout this recovery phase a third, more diverse foraminiferal assemblage starts to prevail, indicating a gradual return to sustained high food levels and increasing oxygen levels, related to a decrease of river influence. Species, dominant during the core phase of the PETM, like Anomalinoides acutus or Pseudouvigerina wilcoxensis, show strongly declining numbers in the recovery phase. Other taxa, like Cibicidoides alleni, returned to the shelf ecosystem, after disappearing nearly completely from the sediments during the initial PETM CIE interval. This coincides with reduced planktic foraminiferal abundances and a tendency towards more silty and less clayey sediments, linked to renewed bottom current activities and winnowing.The lack of severe benthic extinction among shelf-dwelling benthic foraminifera and the observed lateral variability in environmental conditions, demonstrate how foraminiferal shelf communities can adapt to massive global carbon perturbations. As more regional data will become available, these will enable more constraints on environmental parameters and variations along the Atlantic Coastal Plain prior and during the PETM.
- Published
- 2020
16. The Magnitude of Surface Ocean Acidification and Carbon Release During Eocene Thermal Maximum 2 (ETM‐2) and the Paleocene‐Eocene Thermal Maximum (PETM)
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Bärbel Hönisch, Ellen Thomas, L. Haynes, Dustin T Harper, Richard E. Zeebe, Gary Shaffer, and James C Zachos
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PETM ,Atmospheric Science ,Eocene Thermal Maximum 2 ,carbon isotope ,Surface ocean ,Paleontology ,Mineralogy ,chemistry.chemical_element ,ocean acidification ,Ocean acidification ,Isotopes of boron ,Oceanography ,Climate Action ,chemistry ,Isotopes of carbon ,Carbon isotope excursion ,Magnitude (astronomy) ,boron isotope ,hyperthermal ,ETM-2 ,Life Below Water ,Carbon ,Geology - Abstract
Eocene Thermal Maximum 2 (ETM-2; 54.1 Ma) was the second largest Eocene hyperthermal. Like the Paleocene-Eocene Thermal Maximum (PETM), ETM-2 was characterized by massive carbon emissions and several degrees of global warming and thus can serve as a case study for assessing the impacts of rapid CO2 emissions on ocean carbonate chemistry, biota, and climate. Marine carbonate records of ETM-2 are better preserved than those of the PETM due to more subdued carbonate dissolution. As yet, however, the magnitude of this carbon cycle perturbation has not been well constrained. Here, we present the first records of surface ocean acidification for ETM-2, based on stable boron isotope records in mixed-layer planktic foraminifera from two midlatitude ODP sites (1210 in the North Pacific and 1265 in the SE Atlantic), which indicate conservative minimum global sea surface acidification of −0.20 +0.12/−0.13 pH units. Using these estimates of pH and temperature as constraints on carbon cycle model simulations, we conclude that the total mass of C, released over a period of 15 to 25 kyr during ETM-2, likely ranged from 2,600 to 3,800 Gt C, which is greater than previously estimated on the basis of other observations (i.e., stable carbon isotopes and carbonate compensation depth) alone.
- Published
- 2020
17. FLUSHING THE SYSTEM: COUPLING LITHIUM ISOTOPES AND CLIMATE MODEL OBSERVATIONS DURING THE PETM
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Jeffrey T. Kiehl, James C Zachos, Phillip Pogge von Strandmann, William Rush, and Christine A. Shields
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Coupling (electronics) ,Materials science ,Chemical physics ,Isotopes of lithium ,medicine ,Flushing ,Climate model ,medicine.symptom - Published
- 2020
18. On impact and volcanism across the Cretaceous-Paleogene boundary
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Hojung Kim, Gregory E Ravizza, Michael J. Henehan, Sofie Jehle, Jonathan D. Schueth, Kasia K. Śliwińska, Philip F Sexton, Donald E. Penman, Ursula Röhl, Roger E. Summons, Alexander Deutsch, Paul A. Wilson, Peter C. Lippert, Tatsuhiko Yamaguchi, Dick Kroon, Jessica H. Whiteside, Julio Sepúlveda, Sietske J. Batenburg, C. Cournede, Kazuyoshi Moriya, Iris Moebius, Richard D Norris, Laia Alegret, D. C. Loroch, Pincelli M. Hull, Oliver Friedrich, Elizabeth C Sibert, Barbara Donner, Paul R. Bown, André Bornemann, Ellen Thomas, James C Zachos, Thomas Westerhold, Daniel J. Peppe, P. Blum, Timothy J. Bralower, Yale University [New Haven], Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), Scripps Institution of Oceanography (SIO - UC San Diego), University of California [San Diego] (UC San Diego), University of California (UC)-University of California (UC), National Oceanography Centre [Southampton] (NOC), University of Southampton, International Ocean Discovery Program, University of Zaragoza - Universidad de Zaragoza [Zaragoza], Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), University of Minnesota [Morris], University of Minnesota System, OCE 1536611, National Science Foundation, NNX09AM88G, National Aeronautics and Space Administration, USSSP Post-Expedition Activity Award, Office of the Director, PRF#52822-DN18, American Chemical Society Petroleum Research Fund, VO687/14, Deutsche Forschungsgemeinschaft, 16H04070, Japan Society for the Promotion of Science, CGL2017-84693-R, Spanish Ministry of Economy and Competitiveness and FEDER, E33_17R, Government of Aragon and FEDER funds, 11-107497, Danish Council for Independent Research/Natural Sciences, Scripps Institution of Oceanography (SIO), University of California-University of California, Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), and Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)
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010504 meteorology & atmospheric sciences ,General Science & Technology ,Earth science ,Cretaceous–Paleogene boundary ,Volcanic Eruptions ,010502 geochemistry & geophysics ,Extinction, Biological ,01 natural sciences ,Global Warming ,Carbon cycle ,Carbon Cycle ,Theoretical ,Bolide ,Models ,[SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology ,Mexico ,0105 earth and related environmental sciences ,Extinction event ,Multidisciplinary ,Extinction ,Global warming ,Models, Theoretical ,Carbon Dioxide ,Biological ,Outgassing ,13. Climate action ,[SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy ,Flood basalt ,Geology - Abstract
An impact with a dash of volcanism Around the time of the end-Cretaceous mass extinction that wiped out dinosaurs, there was both a bolide impact and a large amount of volcanism. Hull et al. ran several temperature simulations based on different volcanic outgassing scenarios and compared them with temperature records across the extinction event. The best model fits to the data required most outgassing to occur before the impact. When combined with other lines of evidence, these models support an impact-driven extinction. However, volcanic gases may have played a role in shaping the rise of different species after the extinction event. Science , this issue p. 266
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- 2020
19. CHANGES IN HYDROLOGY AND SEDIMENTATION DURING THE PALEOCENE-EOCENE THERMAL MAXIMUM IN THE SALISBURY EMBAYMENT, USA
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Christine A. Shields, Jeffrey T. Kiehl, James C Zachos, and William Rush
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Hydrology ,Hydrology (agriculture) ,Carbon isotope excursion ,Sedimentation ,Geology - Published
- 2020
20. Origin of a global carbonate layer deposited in the aftermath of the Cretaceous-Paleogene boundary impact
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Bettina Schaefer, Christopher H. House, Christine Nims, Ellen Thomas, Timothy J. Bralower, Jens E. Wendler, Sean P. S. Gulick, Si Athena Chen, Vivi Vajda, S. L. Lyons, Julie Cosmidis, Katherine H. Freeman, Christopher M. Lowery, Kliti Grice, Natalia Artemieva, Peter J. Heaney, Dustin T Harper, James C Zachos, Joanna Morgan, Lee R. Kump, and Heather L. Jones
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cyanobacterial bloom ,010504 meteorology & atmospheric sciences ,Micrite ,Geochemistry ,Cretaceous–Paleogene boundary ,Annan geovetenskap och miljövetenskap ,010502 geochemistry & geophysics ,01 natural sciences ,Deep sea ,chemistry.chemical_compound ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,0105 earth and related environmental sciences ,Extinction event ,Calcite ,Biological pump ,micrite ,K-Pg boundary ,Geophysics ,Chicxulub ,chemistry ,Space and Planetary Science ,Carbonate ,Sedimentary rock ,Geology ,Other Earth and Related Environmental Sciences - Abstract
Microcrystalline calcite (micrite) dominates the sedimentary record of the aftermath of the Cretaceous–Paleogene (K–Pg) impact at 31 sites globally, with records ranging from the deep ocean to the Chicxulub impact crater, over intervals ranging from a few centimeters to more than seventeen meters. This micrite-rich layer provides important information about the chemistry and biology of the oceans after the impact. Detailed high-resolution scanning electron microscopy demonstrates that the layer contains abundant calcite crystals in the micron size range with a variety of forms. Crystals are often constructed of delicate, oriented agglomerates of sub-micrometer mesocrystals indicative of rapid precipitation. We compare the form of crystals with natural and experimental calcite to shed light on their origin. Close to the crater, a significant part of the micrite may derive from the initial backreaction of CaO vaporized during impact. In more distal sites, simple interlocking rhombohedral crystals resemble calcite precipitated from solution. Globally, we found unique calcite crystals associated with fossilized extracellular materials that strikingly resemble calcite precipitated by various types of bacteria in natural and laboratory settings. The micrite-rich layer contains abundant bacterial and eukaryotic algal biomarkers and most likely represents global microbial blooms initiated within millennia of the K–Pg mass extinction. Cyanobacteria and non-haptophyte microalgae likely proliferated as dominant primary producers in cold immediate post-impact environments. As surface-water saturation state rose over the following millennia due to the loss of eukaryotic carbonate producers and continuing river input of alkalinity, “whitings” induced by cyanobacteria replaced calcareous nannoplankton as major carbonate producers. We postulate that the blooms grew in supersaturated surface waters as evidenced by crystals that resemble calcite precipitates from solution. The microbial biomass may have served as a food source enabling survival of a portion of the marine biota, ultimately including life on the deep seafloor. Although the dominance of cyanobacterial and algal photosynthesis would have weakened the biological pump, it still would have removed sufficient nutrients from surface waters thus conditioning the ocean for the recovery of biota at higher trophic levels.
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- 2020
21. An astronomically dated record of Earth’s climate and its predictability over the last 66 million years
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Fabio Florindo, Paul A. Wilson, Ann Holbourn, Thomas Westerhold, Roy H Wilkens, David A. Hodell, Claudia Agnini, Eleni Anagnostou, Mitchell W Lyle, Heiko Pälike, Dick Kroon, Kate Littler, Lucas Joost Lourens, Steven M Bohaty, Anna Joy Drury, Diederik Liebrand, David De Vleeschouwer, Norbert Marwan, Vittoria Lauretano, James S K Barnet, James C Zachos, Ursula Röhl, Jun Tian, Thomas Frederichs, Stratigraphy and paleontology, Stratigraphy & paleontology, Westerhold, Thomas [0000-0001-8151-4684], Marwan, Norbert [0000-0003-1437-7039], Drury, Anna Joy [0000-0001-6206-7284], Liebrand, Diederik [0000-0002-6925-7889], Agnini, Claudia [0000-0001-9749-6003], Anagnostou, Eleni [0000-0002-7200-4794], Barnet, James SK [0000-0003-3885-5664], Bohaty, Steven M [0000-0002-1193-7398], De Vleeschouwer, David [0000-0002-3323-807X], Florindo, Fabio [0000-0002-6058-9748], Frederichs, Thomas [0000-0003-0976-0332], Hodell, David A [0000-0001-8537-1588], Holbourn, Ann E [0000-0002-3167-0862], Lauretano, Vittoria [0000-0002-7869-6074], Littler, Kate [0000-0002-4604-3634], Lourens, Lucas J [0000-0002-3815-7770], Lyle, Mitchell [0000-0002-0861-0511], Pälike, Heiko [0000-0003-3386-0923], Röhl, Ursula [0000-0001-9469-7053], Tian, Jun [0000-0002-4842-7076], Wilkens, Roy H [0000-0001-8149-3908], Zachos, James C [0000-0001-8439-1886], and Apollo - University of Cambridge Repository
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13 Climate Action ,Multidisciplinary ,010504 meteorology & atmospheric sciences ,biology ,General Science & Technology ,Astronomical forcing ,sub-01 ,010502 geochemistry & geophysics ,biology.organism_classification ,01 natural sciences ,Foraminifera ,13. Climate action ,Isotopes of carbon ,Benthic zone ,Greenhouse gas ,Statistical analysis ,Physical geography ,Predictability ,General ,Cenozoic ,Geology ,0105 earth and related environmental sciences - Abstract
Much of our understanding of Earth's past climate comes from the measurement of oxygen and carbon isotope variations in deep-sea benthic foraminifera. Yet, long intervals in existing records lack the temporal resolution and age control needed to thoroughly categorize climate states of the Cenozoic era and to study their dynamics. Here, we present a new, highly resolved, astronomically dated, continuous composite of benthic foraminifer isotope records developed in our laboratories. Four climate states-Hothouse, Warmhouse, Coolhouse, Icehouse-are identified on the basis of their distinctive response to astronomical forcing depending on greenhouse gas concentrations and polar ice sheet volume. Statistical analysis of the nonlinear behavior encoded in our record reveals the key role that polar ice volume plays in the predictability of Cenozoic climate dynamics.
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- 2020
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22. Calcium Isotope Response of Morozovella spp. To Paleocene-Eocene Ocean Acidification
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Gabriella D. Kitch, Andrew D. Jacobson, Matthew T. Hurtgen, Bradley B. Sageman, Dustin T. Harper, and James C. Zachos
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- 2020
23. Global Extent of Early Eocene Hyperthermal Events: A New Pacific Benthic Foraminiferal Isotope Record From Shatsky Rise (ODP Site 1209)
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James C Zachos, Thomas Westerhold, Barbara Donner, and Ursula Röhl
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Atmospheric Science ,Oceanography ,010504 meteorology & atmospheric sciences ,Isotope ,Benthic zone ,Paleontology ,010502 geochemistry & geophysics ,01 natural sciences ,Geology ,0105 earth and related environmental sciences - Published
- 2018
24. Export of nutrient rich Northern Component Water preceded early Oligocene Antarctic glaciation
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Claire E Huck, Alba Legarda-Lisarri, Agatha M. de Boer, Jan Backman, Tina van de Flierdt, Matthew Huber, James C Zachos, Helen K. Coxall, Kasia K. Sliwinska, Matt O'Regan, Caroline H Lear, and Natural Environment Research Council (NERC)
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ATLANTIC ,EOCENE ,ARCTIC-OCEAN ,010504 meteorology & atmospheric sciences ,DRAKE PASSAGE ,Structural basin ,010502 geochemistry & geophysics ,01 natural sciences ,SOUTHERN LABRADOR SEA ,Isotopic signature ,MD Multidisciplinary ,Meteorology & Atmospheric Sciences ,Glacial period ,Geosciences, Multidisciplinary ,0105 earth and related environmental sciences ,geography ,Science & Technology ,geography.geographical_feature_category ,North Atlantic Deep Water ,Sediment ,Geology ,THERMOHALINE CIRCULATION ,SECULAR VARIATION ,FORAMINIFERAL MG/CA PALEOTHERMOMETRY ,Subarctic climate ,EVOLUTION ,Tectonics ,Oceanography ,Ridge ,Physical Sciences ,General Earth and Planetary Sciences ,MERIDIONAL OVERTURNING CIRCULATION - Abstract
The onset of the North Atlantic Deep Water formation is thought to have coincided with Antarctic ice-sheet growth about 34 million years ago (Ma). However, this timing is debated, in part due to questions over the geochemical signature of the ancient Northern Component Water (NCW) formed in the deep North Atlantic. Here we present detailed geochemical records from North Atlantic sediment cores located close to sites of deep-water formation. We find that prior to 36 Ma, the northwestern Atlantic was stratified, with nutrient-rich, low-salinity bottom waters. This restricted basin transitioned into a conduit for NCW that began flowing southwards approximately one million years before the initial Antarctic glaciation. The probable trigger was tectonic adjustments in subarctic seas that enabled an increased exchange across the Greenland–Scotland Ridge. The increasing surface salinity and density strengthened the production of NCW. The late Eocene deep-water mass differed in its carbon isotopic signature from modern values as a result of the leakage of fossil carbon from the Arctic Ocean. Export of this nutrient-laden water provided a transient pulse of CO2 to the Earth system, which perhaps caused short-term warming, whereas the long-term effect of enhanced NCW formation was a greater northward heat transport that cooled Antarctica.
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- 2018
25. Astronomically paced changes in deep-water circulation in the western North Atlantic during the middle Eocene
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Igor Niezgodzki, Gerrit Lohmann, Heiko Pälike, Philip F Sexton, Torsten Bickert, Dustin T Harper, James C Zachos, Maximilian Vahlenkamp, Sandra Kirtland Turner, and David De Vleeschouwer
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geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Lithology ,North Atlantic Deep Water ,010502 geochemistry & geophysics ,01 natural sciences ,Boundary current ,Deep water ,Abyssal zone ,Paleontology ,Geophysics ,13. Climate action ,Space and Planetary Science ,Geochemistry and Petrology ,Benthic zone ,Earth and Planetary Sciences (miscellaneous) ,Earth system model ,14. Life underwater ,Oceanic basin ,Geology ,0105 earth and related environmental sciences - Abstract
North Atlantic Deep Water (NADW) currently redistributes heat and salt between Earth's ocean basins, and plays a vital role in the ocean-atmosphere CO2 exchange. Despite its crucial role in today's climate system, vigorous debate remains as to when deep-water formation in the North Atlantic started. Here, we present datasets from carbonate-rich middle Eocene sediments from the Newfoundland Ridge, revealing a unique archive of paleoceanographic change from the progressively cooling climate of the middle Eocene. Well-defined lithologic alternations between calcareous ooze and clay-rich intervals occur at the ∼41-kyr beat of axial obliquity. Hence, we identify obliquity as the driver of middle Eocene (43.5–46 Ma) Northern Component Water (NCW, the predecessor of modern NADW) variability. High-resolution benthic foraminiferal δ 18 O and δ 13 C suggest that obliquity minima correspond to cold, nutrient-depleted, western North Atlantic deep waters. We thus link stronger NCW formation with obliquity minima. In contrast, during obliquity maxima, Deep Western Boundary Currents were weaker and warmer, while abyssal nutrients were more abundant. These aspects reflect a more sluggish NCW formation. This obliquity-paced paleoceanographic regime is in excellent agreement with results from an Earth system model, in which obliquity minima configurations enhance NCW formation.
- Published
- 2018
26. Influence of solution chemistry on the boron content in inorganic calcite grown in artificial seawater
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James C Zachos, Dustin T Harper, Joji Uchikawa, Richard E. Zeebe, and Donald E. Penman
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Calcite ,010504 meteorology & atmospheric sciences ,Analytical chemistry ,chemistry.chemical_element ,Mineralogy ,Artificial seawater ,Isotopes of boron ,Calcium ,010502 geochemistry & geophysics ,01 natural sciences ,Salinity ,chemistry.chemical_compound ,chemistry ,Geochemistry and Petrology ,Carbonate ,Seawater ,Boron ,Geology ,0105 earth and related environmental sciences - Abstract
The ratio of boron to calcium (B/Ca) in marine biogenic carbonates has been proposed as a proxy for properties of seawater carbonate chemistry. Applying this proxy to planktic foraminifera residing in the surface seawater largely in equilibrium with the atmosphere may provide a valuable handle on past atmospheric CO 2 concentrations. However, precise controls on B/Ca in planktic foraminifera remain enigmatic because it has been shown to depend on multiple physicochemical seawater properties. To help establish a firm inorganic basis for interpreting the B/Ca records, we examined the effect of a suite of chemical parameters ([Ca 2+ ], pH, [DIC], salinity and [PO 4 3− ]) on B/Ca in inorganic calcite precipitated in artificial seawater. These parameters were primarily varied individually while keeping all others constant, but we also tested the influence of pH and [DIC] at a constant calcite precipitation rate ( R ) by concurrent [Ca 2+ ] adjustments. In the simple [Ca 2+ ], pH and [DIC] experiments, both R and B/Ca increased with these parameters. In the pH–[Ca 2+ ] and [DIC]–[Ca 2+ ] experiments at constant R , on the other hand, B/Ca was invariant at different pH and decreased with [DIC], respectively. These patterns agree with the behavior of solution [B Total /DIC] ratio such that, at a fixed [B Total ], it is independent of pH but decreases with [DIC]. Based on these results, R and [B Total /DIC] ratio appear to be the primary controls on B/Ca in inorganic calcite, suggesting that both B(OH) 4 − and B(OH) 3 are possibly involved in B incorporation. Moreover, B/Ca modestly increased with salinity and [PO 4 3− ]. Inorganic calcite precipitated at higher R and in the presence of oxyanions such as SO 4 2− and PO 4 3− in growth solutions often undergoes surface roughening due to formation of crystallographic defects, vacancies and, occasionally, amorphous/hydrous CaCO 3 . These non-lattice sites may provide additional space for B, particularly B(OH) 3 . Consequently, besides the macroscopic influence of R and bulk solution chemistry, molecular-scale processes associated with calcite nucleation can be an important consideration for B incorporation, especially in complex ionic solutions. Lastly, the covariance of B/Ca with [DIC] and salinity observed here qualitatively agrees with those in planktic foraminifers. It follows that their impact on foraminiferal B/Ca is partly inorganically driven, which may explain why the effect is evident across different species.
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- 2017
27. Calcareous nannoplankton response to early Eocene warmth, Southwest Pacific Ocean
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Claire Shepherd, Kristina M. Pascher, Christopher J. Hollis, Denise K. Kulhanek, C Percy Strong, James C Zachos, and Hugh E. G. Morgans
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010506 paleontology ,geography ,Plateau ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Environmental change ,Paleontology ,Hiatus ,Oceanography ,01 natural sciences ,Deep sea ,Abundance (ecology) ,Phytoplankton ,Climate model ,Marine ecosystem ,Geology ,0105 earth and related environmental sciences - Abstract
Episodes of pronounced climatic warming in the early Eocene (56–48 Ma) provide insights into how biological systems might respond to future climate changes. Eocene climate reconstructions for the Southwest (SW) Pacific have proved challenging due to some disparities between geochemical proxy-based estimates for sea temperatures and estimates derived from climate models. Changes in marine phytoplankton populations through the early Eocene provide a means to evaluate model and proxy-based approaches and also reveal how climatic changes affected the ocean ecosystem. This study documents early to middle Eocene calcareous nannofossil assemblages from legacy Deep Sea Drilling Project (DSDP) sites in the SW Pacific. We integrate nannofossil assemblage changes with foraminiferal-based stable isotopes and other microfossil data to provide updated age models for DSDP Sites 207 (Lord Howe Rise) and 277 (Campbell Plateau), and to infer past environmental change through the early to mid-Eocene in the SW Pacific. Although these sites record a short hiatus in the earliest Eocene, deposition resumed by ~54 Ma, prior to the onset of the Early Eocene Climate Optimum (EECO). Both sites show an increase in warm-water taxa from the onset of the EECO until approximately 50.5 Ma. Abundance of warm-water taxa was higher (~23%) at the EECO onset at the more northerly Site 207 and increased only slightly to ~27%, whereas at Site 277 warm-water taxa comprised only ~3% at the EECO onset but increased to ~31% by 50.5 Ma. Cool-water taxa at both sites were present in very sparse numbers (
- Published
- 2021
28. Increased frequency of extreme precipitation events in the North Atlantic during the PETM: Observations and theory
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Jeffrey T. Kiehl, Christine A. Shields, James C Zachos, and William Rush
- Subjects
010506 paleontology ,Paleontology ,Magnitude (mathematics) ,Forcing (mathematics) ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Climatology ,Greenhouse gas ,Extratropical cyclone ,Climate model ,Sedimentary rock ,Precipitation ,Water cycle ,Ecology, Evolution, Behavior and Systematics ,Geology ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
Climate model simulations of the PETM (Paleocene-Eocene Thermal Maximum) warming have mainly focused on replicating the global thermal response through greenhouse forcing, i.e. CO2, at levels compatible with observations. Comparatively less effort has gone into assessing the skill of models to replicate the response of the hydrologic cycle to the warming, particularly on regional scales. Here we have assembled proxy records of regional precipitation, focusing on the Mid-Atlantic Coasts of North America (New Jersey) and Europe (Spain) to test the response of the hydrologic system to greenhouse gas forcing of the magnitude estimated for the PETM (i.e., 2×). Given evidence that the PETM initiated during a maximum in eccentricity, this includes the response under neutral and extreme orbital configurations. Modeled results show excellent agreement with observations in Northern Spain, with a significant increase in both mean annual and extreme precipitation resulting from increased CO2 levels under a neutral orbit. The Mid Atlantic Coast simulations agree with observations showing increases in both overall and extreme precipitation as a result of CO2 increases. In particular, the development of sustained atmospheric rivers might be significantly contributing to the extremes of the eastern Atlantic, whereas extratropical cyclones are likely contributing to the extremes in the western Atlantic. With an eccentric orbit that maximizes insolation during boreal summer, there is a suppression of extreme precipitation events in the eastern Atlantic and an amplification in the western Atlantic, which may account for observations in the relative timing of the sedimentary response to the carbon isotope excursion associated with the PETM.
- Published
- 2021
29. Orbital forcing of the Paleocene and Eocene carbon cycle
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James C Zachos, Kate Littler, Richard E. Zeebe, and Thomas Westerhold
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010504 meteorology & atmospheric sciences ,Orbital forcing ,Direct insolation ,Lag ,Astronomical forcing ,Paleontology ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Physics::Geophysics ,Carbon cycle ,Earth system science ,Amplitude ,Benthic zone ,Climatology ,Astrophysics::Earth and Planetary Astrophysics ,Physics::Atmospheric and Oceanic Physics ,Geology ,0105 earth and related environmental sciences - Abstract
Multimillion-year proxy records across the Paleocene and Eocene show prominent variations on orbital time scales. The cycles, which have been identified at various sites across the globe, preferentially concentrate spectral power at eccentricity and precessional frequencies. It is evident that these cycles are an expression of changes in global climate and carbon cycling paced by astronomical forcing. However, little is currently known about the link between orbital forcing and the carbon cycle-climate system and the amplitude of associated atmospheric CO2 variations. Here we use simple and complex carbon cycle models to explore the basic effect of different orbital forcing schemes and noise on the carbon cycle. Our primary modeling target is the high-resolution, ∼7.7 Myr long, benthic isotope record at Ocean Drilling Program Site 1262 in the South Atlantic. For direct insolation forcing (as opposed to artificial eccentricity-tilt-precession), one major challenge is understanding how the system transfers spectral power from high to low frequencies. We discuss feasible solutions, including insolation transformations analogous to electronic AC-DC conversion (DC'ing). Regarding mechanisms, we focus on tropical insolation and a long-term carbon imbalance in terrestrial organic burial/oxidation but do not rule out other scenarios. Our analysis shows that high-latitude mechanisms are unlikely drivers of orbitally paced changes in the late Paleocene-early Eocene (LPEE) Earth system. Furthermore, we provide constraints on the origin and isotopic composition of a possible LPEE cyclic carbon imbalance/source responding to astronomical forcing. Our simulations also reveal a mechanism for the large δ13C-eccentricity lag at the 400 kyr period observed in Paleocene, Oligocene, and Miocene sections. We present the first estimates of orbital-scale variations in atmospheric CO2 during the late Paleocene and early Eocene.
- Published
- 2017
30. A High‐Fidelity Benthic Stable Isotope Record of Late Cretaceous–Early Eocene Climate Change and Carbon‐Cycling
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Ursula Röhl, James C Zachos, Ian Bailey, Thomas Westerhold, Melanie J. Leng, James S K Barnet, Kate Littler, Dick Kroon, and University of St Andrews. School of Earth & Environmental Sciences
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Atmospheric Science ,Orbital forcing ,Paleoclimate ,Climate change ,Oceanography ,Eocene ,Paleoceanography ,Paleoclimatology ,SDG 13 - Climate Action ,QE ,SDG 14 - Life Below Water ,Life Below Water ,Stable isotopes ,Stable isotope ratio ,Paleontology ,DAS ,Cretaceous ,Climate Action ,QE Geology ,Benthic zone ,Geological survey ,Paleocene ,Geology - Abstract
The new Early–Middle Paleocene benthic δ13C and δ18O data were funded by the Natural Environment Research Council (NERC) Isotope Geosciences Facility at the British Geological Survey (IP‐1581–1115), awarded to James Barnet and Kate Littler. Financial support for this research was also provided by the Deutsche Forschungsgemeinschaft (DFG) to Ursula Röhl and Thomas Westerhold, and by NSF grant OCE‐1658017 to James Zachos. The Late Cretaceous–Early Paleogene is the most recent period in Earth history that experienced sustained global greenhouse warmth on multimillion year timescales. Yet, knowledge of ambient climate conditions and the complex interplay between various forcing mechanisms are still poorly constrained. Here we present a 14.75 million‐year‐long, high‐resolution, orbitally tuned record of paired climate change and carbon‐cycling for this enigmatic period (~67–52 Ma), which we compare to an up‐to‐date compilation of atmospheric pCO2 records. Our climate and carbon‐cycling records, which are the highest resolution stratigraphically complete records to be constructed from a single marine site in the Atlantic Ocean, feature all major transient warming events (termed “hyperthermals”) known from this time period. We identify eccentricity as the dominant pacemaker of climate and the carbon cycle throughout the Late Maastrichtian to Early Eocene, through the modulation of precession. On average, changes in the carbon cycle lagged changes in climate by ~23,000 years at the long eccentricity (405,000‐year) band, and by ~3,000–4,500 years at the short eccentricity (100,000‐year) band, suggesting that light carbon was released as a positive feedback to warming induced by orbital forcing. Our new record places all known hyperthermals of the Late Maastrichtian–Early Eocene into temporal context with regards to evolving ambient climate of the time. We constrain potential carbon cycle influences of Large Igneous Province volcanism associated with the Deccan Traps and North Atlantic Igneous Province, as well as the sensitivity of climate and the carbon‐cycle to the 2.4 million‐year‐long eccentricity cycle. Publisher PDF
- Published
- 2019
31. The DeepMIP contribution to PMIP4: methodologies for selection, compilation and analysis of latest Paleocene and early Eocene climate proxy data, incorporating version 0.1 of the DeepMIP database
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Christopher J. Hollis, Tom Dunkley Jones, Eleni Anagnostou, Peter K. Bijl, Margot J. Cramwinckel, Ying Cui, Gerald R. Dickens, Kirsty M. Edgar, Yvette Eley, David Evans, Gavin L. Foster, Joost Frieling, Gordon N. Inglis, Elizabeth M. Kennedy, Reinhard Kozdon, Vittoria Lauretano, Caroline H. Lear, Kate Littler, Nele Meckler, B. David A. Naafs, Heiko Pälike, Richard D. Pancost, Paul Pearson, Dana L. Royer, Ulrich Salzmann, Brian Schubert, Hannu Seebeck, Appy Sluijs, Robert Speijer, Peter Stassen, Jessica Tierney, Aradhna Tripati, Bridget Wade, Thomas Westerhold, Caitlyn Witkowski, James C. Zachos, Yi Ge Zhang, Matthew Huber, and Daniel J. Lunt
- Subjects
F800 - Abstract
The early Eocene (56 to 48 million years ago) is inferred to have been the most recent time that Earth's atmospheric CO2 concentrations exceeded 1000 ppm. Global mean temperatures were also substantially warmer than present day. As such, study of early Eocene climate provides insight into how a super-warm Earth system behaves and offers an opportunity to evaluate climate models under conditions of high greenhouse gas forcing. The Deep Time Model Intercomparison Project (DeepMIP) is a systematic model-model and model-data intercomparison of three early Paleogne time slices: latest Paleocene, Paleocene-Eocene thermal maximum and early Eocene climatic optimum. A previous article outlined the model experimental design for climate model simulations. In this article, we outline the methodologies to be used for the compilation and analysis of climate proxy data, primarily proxies for temperature and CO2. This paper establishes the protocols for a concerted and coordinated effort to compile the climate proxy records across a wide geographic range. The resulting climate atlas will be used to constrain and evaluate climate models for the three selected time intervals, and provide insights into the mechanisms that control these warm climate states. We provide version 0.1 of this database, in anticipation that this will be expanded in subsequent publications.
- Published
- 2019
32. Supplementary material to 'The DeepMIP contribution to PMIP4: methodologies for selection, compilation and analysis of latest Paleocene and early Eocene climate proxy data, incorporating version 0.1 of the DeepMIP database'
- Author
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Christopher J. Hollis, Tom Dunkley Jones, Eleni Anagnostou, Peter K. Bijl, Margot J. Cramwinckel, Ying Cui, Gerald R. Dickens, Kirsty M. Edgar, Yvette Eley, David Evans, Gavin L. Foster, Joost Frieling, Gordon N. Inglis, Elizabeth M. Kennedy, Reinhard Kozdon, Vittoria Lauretano, Caroline H. Lear, Kate Littler, Nele Meckler, B. David A. Naafs, Heiko Pälike, Richard D. Pancost, Paul Pearson, Dana L. Royer, Ulrich Salzmann, Brian Schubert, Hannu Seebeck, Appy Sluijs, Robert Speijer, Peter Stassen, Jessica Tierney, Aradhna Tripati, Bridget Wade, Thomas Westerhold, Caitlyn Witkowski, James C. Zachos, Yi Ge Zhang, Matthew Huber, and Daniel J. Lunt
- Published
- 2019
33. CHRONOSTRATIGRAPHIC FRAMEWORK AND COMPOSITE SECTION COMPILATION OF UPPER PALEOCENE AND LOWER EOCENE SEDIMENTS FROM THE SALISBURY EMBAYMENT, USA
- Author
-
Jean M. Self-Trail, Yang Zhang, Will D. Rush, Marci M. Robinson, James C Zachos, and James G. Ogg
- Subjects
Paleontology ,Section (archaeology) ,Geology - Published
- 2019
34. TWO PULSES OF CARBON RELEASED DURING THE ONSET OF PALEOCENE-EOCENE THERMAL MAXIMUM
- Author
-
Christopher D. Standish, Tali L. Babila, Monika Doubrawa, James C Zachos, Gavin L. Foster, Marci M. Robinson, Robert P. Speijer, Peter Stassen, Timothy J. Bralower, and Jean M. Self-Trail
- Subjects
chemistry ,Paleoceanography ,Carbon isotope excursion ,chemistry.chemical_element ,Mineralogy ,Global change ,Carbon ,Geology - Published
- 2019
35. NEW INSIGHTS INTO SHELF ECOSYSTEMS PRIOR AND DURING THE PETM
- Author
-
Peter Stassen, Marci M. Robinson, Robert P. Speijer, Monika Doubrawa, James C Zachos, KU Leuven, and Tali L. Babila
- Subjects
Oceanography ,Environmental science ,Ecosystem - Published
- 2019
36. No substantial long-term bias in the Cenozoic benthic foraminifera oxygen-isotope record
- Author
-
Gavin L. Foster, Michael J. Henehan, David Evans, James C Zachos, Marcus P. S. Badger, and Caroline H Lear
- Subjects
Geologic Sediments ,010504 meteorology & atmospheric sciences ,Badger ,Science ,Oceans and Seas ,General Physics and Astronomy ,Foraminifera ,Oxygen Isotopes ,010502 geochemistry & geophysics ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Isotopes of oxygen ,biology.animal ,Correspondence ,MD Multidisciplinary ,QE ,QD ,Seawater ,lcsh:Science ,0105 earth and related environmental sciences ,Multidisciplinary ,biology ,Fossils ,Temperature ,Records ,General Chemistry ,biology.organism_classification ,Plankton ,Term (time) ,Oxygen ,Oceanography ,Benthic zone ,lcsh:Q ,Cenozoic ,Geology ,Environmental Monitoring - Abstract
Author(s): Evans, David; Badger, Marcus PS; Foster, Gavin L; Henehan, Michael J; Lear, Caroline H; Zachos, James C
- Published
- 2018
37. Sea level, biotic and carbon-isotope response to the Paleocene–Eocene thermal maximum in Tibetan Himalayan platform carbonates
- Author
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Marcelle K. BouDagher-Fadel, James C Zachos, Juan Li, Eduardo Garzanti, Xiumian Hu, Li, J, Hu, X, Zachos, J, Garzanti, E, and BouDagher-Fadel, M
- Subjects
010504 meteorology & atmospheric sciences ,Environmental change ,Southern Tibet ,02 engineering and technology ,Oceanography ,01 natural sciences ,Deep sea ,Carbon cycle ,Foraminifera ,Paleontology ,Biotic response ,Continental margin ,Relative sea-level change ,0202 electrical engineering, electronic engineering, information engineering ,Shallow-water carbonate ramp ,Sea level ,0105 earth and related environmental sciences ,Global and Planetary Change ,biology ,Carbon isotope ,Paleocene–Eocene thermal maximum ,020206 networking & telecommunications ,biology.organism_classification ,Benthic zone ,Isotopes of carbon ,Geology - Abstract
During the Paleocene–Eocene Thermal Maximum (PETM, ~56 Ma), a large, negative carbon-isotope excursion (CIE) testifies to a massive perturbation of the global carbon cycle. Shallow-marine settings are crucial to understand the environmental and ecological changes associated with the PETM and the connection between continental and open-marine environments. Detailed sedimentological, paleontological, and geochemical analysis of a quasi-continuous succession of shallow-marine carbonates in the Tethys Himalaya of southern Tibet indicates that a relative rise in sea level coincided with PETM onset, continued through PETM core, and terminated with a regression at PETM recovery. At PETM onset, corresponding to the SBZ4/SBZ5 boundary, no obvious impact on biota and specifically on larger benthic foraminifera (LBF) is observed. The major biotic change occurs later on at PETM recovery, corresponding to the SBZ5/SBZ6 boundary. Our data suggest that relative sea level, rather than temperature, exerted the main control on benthic biota during the PETM. Although the δ13Corg values of organic matter are similar in the deep sea and shallow-marine continental margins, the δ13Ccarb value of bulk carbonates are significantly 13C-depleted, which we attribute to environmental change driven by relative sea-level fluctuations.
- Published
- 2020
38. Anthropogenic carbon release rate unprecedented during the past 66 million years
- Author
-
Richard E. Zeebe, Andy Ridgwell, and James C Zachos
- Subjects
010504 meteorology & atmospheric sciences ,Event (relativity) ,chemistry.chemical_element ,Climate change ,Carbon cycle ,Palaeoclimate ,010502 geochemistry & geophysics ,01 natural sciences ,Climate Action ,Palaeoceanography ,chemistry ,Climatology ,Carbon isotope excursion ,Meteorology & Atmospheric Sciences ,General Earth and Planetary Sciences ,Carbon ,Geology ,0105 earth and related environmental sciences - Abstract
© 2016 Macmillan Publishers Limited. All rights reserved. Carbon release rates from anthropogenic sources reached a record high of ∼10 Pg C yr-1in 2014. Geologic analogues from past transient climate changes could provide invaluable constraints on the response of the climate system to such perturbations, but only if the associated carbon release rates can be reliably reconstructed. The Palaeocene-Eocene Thermal Maximum (PETM) is known at present to have the highest carbon release rates of the past 66 million years, but robust estimates of the initial rate and onset duration are hindered by uncertainties in age models. Here we introduce a new method to extract rates of change from a sedimentary record based on the relative timing of climate and carbon cycle changes, without the need for an age model. We apply this method to stable carbon and oxygen isotope records from the New Jersey shelf using time-series analysis and carbon cycle-climate modelling. We calculate that the initial carbon release during the onset of the PETM occurred over at least 4,000 years. This constrains the maximum sustained PETM carbon release rate to less than 1.1 Pg C yr-1. We conclude that, given currently available records, the present anthropogenic carbon release rate is unprecedented during the past 66 million years. We suggest that such a 'no-analogue' state represents a fundamental challenge in constraining future climate projections. Also, future ecosystem disruptions are likely to exceed the relatively limited extinctions observed at the PETM.
- Published
- 2016
39. Capturing the global signature of surface ocean acidification during the Palaeocene–Eocene Thermal Maximum
- Author
-
D. Clay Kelly, Timothy J. Bralower, Bärbel Hönisch, James C Zachos, Donald E. Penman, Yair Rosenthal, and Tali L. Babila
- Subjects
010504 meteorology & atmospheric sciences ,General Science & Technology ,General Mathematics ,General Physics and Astronomy ,chemistry.chemical_element ,ocean acidification ,010502 geochemistry & geophysics ,01 natural sciences ,Foraminifera ,chemistry.chemical_compound ,planktonic foraminifera ,Palaeocene-Eocene Thermal Maximum ,MD Multidisciplinary ,Palaeocene–Eocene Thermal Maximum ,Life Below Water ,0105 earth and related environmental sciences ,Carbon dioxide in Earth's atmosphere ,biology ,fungi ,Global warming ,General Engineering ,Ocean acidification ,Articles ,biology.organism_classification ,Climate Action ,Oceanography ,boron/calcium ,chemistry ,Isotopes of carbon ,Greenhouse gas ,boron isotope ,Carbonate ,Carbon - Abstract
Geologically abrupt carbon perturbations such as the Palaeocene–Eocene Thermal Maximum (PETM, approx. 56 Ma) are the closest geological points of comparison to current anthropogenic carbon emissions. Associated with the rapid carbon release during this event are profound environmental changes in the oceans including warming, deoxygenation and acidification. To evaluate the global extent of surface ocean acidification during the PETM, we present a compilation of new and published surface ocean carbonate chemistry and pH reconstructions from various palaeoceanographic settings. We use boron to calcium ratios (B/Ca) and boron isotopes (δ 11 B) in surface- and thermocline-dwelling planktonic foraminifera to reconstruct ocean carbonate chemistry and pH. Our records exhibit a B/Ca reduction of 30–40% and a δ 11 B decline of 1.0–1.2‰ coeval with the carbon isotope excursion. The tight coupling between boron proxies and carbon isotope records is consistent with the interpretation that oceanic absorption of the carbon released at the onset of the PETM resulted in widespread surface ocean acidification. The remarkable similarity among records from different ocean regions suggests that the degree of ocean carbonate change was globally near uniform. We attribute the global extent of surface ocean acidification to elevated atmospheric carbon dioxide levels during the main phase of the PETM. This article is part of a discussion meeting issue ‘Hyperthermals: rapid and extreme global warming in our geological past’.
- Published
- 2018
40. Greenhouse- and orbital-forced climate extremes during the early Eocene
- Author
-
Mathew Rothstein, Jeffrey T. Kiehl, Christine A. Shields, James C Zachos, and Mark Snyder
- Subjects
010504 meteorology & atmospheric sciences ,General Science & Technology ,General Mathematics ,General Physics and Astronomy ,Climate change ,010502 geochemistry & geophysics ,01 natural sciences ,Palaeocene-Eocene Thermal Maximum ,MD Multidisciplinary ,medicine ,Precipitation ,Palaeocene–Eocene Thermal Maximum ,Water cycle ,0105 earth and related environmental sciences ,Global warming ,Flooding (psychology) ,General Engineering ,Northern Hemisphere ,Articles ,Seasonality ,hydrological cycle ,medicine.disease ,climate change ,Climatology ,Greenhouse gas ,Environmental science - Abstract
The Palaeocene–Eocene Thermal Maximum (PETM) was a significant global warming event in Earth's deep past (56 Mya). The warming across the PETM boundary was driven by a rapid rise in greenhouse gases. The event also coincided with a time of maximum insolation in Northern Hemisphere summer. There is increased evidence that the mean warming was accompanied by enhanced seasonality and/or extremes in precipitation (and flooding) and drought. A high horizontal resolution (50 km) global climate model is used to explore changes in the seasonal cycle of surface temperature, precipitation, evaporation minus precipitation and river run-off for regions where proxy data are available. Comparison for the regions indicates the model accurately simulates the observed changes in these climatic characteristics with North American interior warming and drying, and warming and increased river run-off at other regions. The addition of maximum insolation in Northern Hemisphere summer leads to a drier North America, but wetter conditions at most other locations. Long-range transport of atmospheric moisture plays a critical role in explaining regional changes in the water cycle. Such high-frequency variations in precipitation might also help explain discrepancies or misinterpretation of some climate proxies from the same locations, especially where sampling is coarse, i.e. at or greater than the frequency of precession. This article is part of a discussion meeting issue ‘Hyperthermals: rapid and extreme global warming in our geological past’.
- Published
- 2018
41. EFFECTS OF SIZE-SELECTIVE SEDIMENT MIXING ON DEEP-SEA RECORDS OF THE PALEOCENE-EOCENE THERMAL MAXIMUM
- Author
-
Timothy J. Bralower, James C Zachos, Brittany N. Hupp, and D. Clay Kelly
- Subjects
Carbon isotope excursion ,Mineralogy ,Sediment ,Size selective ,Deep sea ,Geology ,Mixing (physics) - Published
- 2018
42. The Paleocene–Eocene Thermal Maximum at DSDP Site 277, Campbell Plateau, southern Pacific Ocean
- Author
-
Víctor Villasante-Marcos, Denise K. Kulhanek, Andy Phillips, Stephen Eggins, Kate Littler, James C Zachos, Benjamin R. Hines, L. Northcote, C. P. Strong, and Christopher J. Hollis
- Subjects
lcsh:GE1-350 ,Global and Planetary Change ,geography ,Plateau ,geography.geographical_feature_category ,δ13C ,δ18O ,Stratigraphy ,lcsh:Environmental protection ,Ocean current ,Paleontology ,Sediment ,Deep sea ,Diagenesis ,Oceanography ,lcsh:Environmental pollution ,lcsh:TD172-193.5 ,Sedimentary rock ,lcsh:TD169-171.8 ,Geology ,lcsh:Environmental sciences - Abstract
Re-examination of sediment cores from Deep Sea Drilling Project (DSDP) Site 277 on the western margin of the Campbell Plateau (paleolatitude of ~65° S) has identified an intact Paleocene–Eocene (P–E) boundary overlain by a 34 cm thick record of the Paleocene–Eocene Thermal Maximum (PETM) within nannofossil chalk. The upper part of the PETM is truncated, either due to drilling disturbance or a sedimentary hiatus. An intact record of the onset of the PETM is indicated by a gradual decrease in δ13C values over 20 cm, followed by a 14 cm interval in which δ13C is 2 ‰ lighter than uppermost Paleocene values. After accounting for effects of diagenetic alteration, we use δ18O and Mg/Ca values from foraminiferal tests to determine that intermediate and surface waters warmed by ~5–6° at the onset of the PETM prior to the full development of the negative δ13C excursion. After this initial warming, sea temperatures were relatively stable through the PETM but declined abruptly across the horizon that truncates the event at this site. Mg/Ca analysis of foraminiferal tests indicates peak intermediate and surface water temperatures of ~19 and ~32 °C, respectively. These temperatures may be influenced by residual diagenetic factors and changes in ocean circulation, and surface water values may also be biased towards warm-season temperatures.
- Published
- 2015
43. Experimental evidence for kinetic effects on B/Ca in synthetic calcite: Implications for potential B(OH)4− and B(OH)3 incorporation
- Author
-
Richard E. Zeebe, James C Zachos, Joji Uchikawa, and Donald E. Penman
- Subjects
Calcite ,Chemistry ,Analytical chemistry ,Mineralogy ,chemistry.chemical_element ,Calcium ,Kinetic energy ,chemistry.chemical_compound ,Geochemistry and Petrology ,Dissolved organic carbon ,Carbonate ,Seawater ,Saturation (chemistry) ,Boron - Abstract
The boron to calcium ratio (B/Ca) in biogenic CaCO3 is being increasingly utilized as a proxy for past ocean carbonate chemistry. However, B/Ca of cultured and core-top foraminifers show dependence on multiple physicochemical seawater properties and only a few of those have been inorganically tested for their impacts. Accordingly, our understanding of the controls on foraminiferal B/Ca and thus how to interpret B/Ca in fossil shells is incomplete. To gain a clearer understanding of the B incorporation mechanism, we performed inorganic calcite precipitation experiments using a pH-stat system. As previously reported, we confirm that B/Ca in calcite increases with both fluid pH and total B concentration (denoted as [BT], where [BT] = [B(OH)3] + [B(OH)4−]). We provide the first evidence that B/Ca also increases with the concentration of total dissolved inorganic carbon (DIC) and calcium ion. With the exception of the [BT] experiments, these chemical manipulations were accompanied by an increase in calcite saturation, and accordingly precipitation rate (denoted as R). But when pH and [Ca2+] were jointly varied at a fixed saturation level to maintain relatively constant R at different pH and [Ca2+] combinations, B/Ca was insensitive to both pH and [Ca2+] changes. These experimental results unequivocally suggest kinetic effects related to R on B/Ca. Furthermore, with a suite of chemical manipulations we found that the B/Ca variability is explicable by just R and the [BT]/[DIC] ratio in the parent fluids. This observation was particularly robust for relatively rapidly precipitated samples, whereas for relatively slowly precipitated samples, it was somewhat ambiguous whether the [BT]/[DIC] or [B(OH)4−]/[HCO3−] ratio provides a better fit to the experimental data. Nonetheless, our experimental results can be considered as indirect evidence for incorporation of both B(OH)4− and B(OH)3 into calcite. We propose a simple mathematical expression to describe the mode of B incorporation into synthetic calcite that depends only on the fluid [BT]/[DIC] ratio and the precipitation rate R. This novel finding has important implications for future calibrations and applications of the B/Ca proxy as well as the δ11B paleo-pH proxy.
- Published
- 2015
44. Supplementary material to 'Astronomical Calibration of the Ypresian Time Scale: Implications for Seafloor Spreading Rates and the Chaotic Behaviour of the Solar System?'
- Author
-
Thomas Westerhold, Ursula Röhl, Thomas Frederichs, Claudia Agnini, Isabella Raffi, James C. Zachos, and Roy H. Wilkens
- Published
- 2017
45. Data report: relative abundance of benthic foraminiferal morphotypes across the Eocene/Oligocene and Oligocene/Miocene boundaries (IODP Expedition 342 Site U1406|North Atlantic)
- Author
-
Heiko Pälike, F. Wu, Donald E. Penman, Helen K. Coxall, Maximilian Vahlenkamp, K. Kerr, R.N. Norris, Pincelli M. Hull, David De Vleeschouwer, S. D haenens, Wendy E C Kordesch, Philip F Sexton, Oliver Friedrich, Kazuyoshi Moriya, James C Zachos, Paul A. Wilson, Bradley N. Opdyke, A. Cameron, L.E. Elder, Steven M Bohaty, and Sandra Kirtland Turner
- Subjects
010506 paleontology ,Paleontology ,Oceanography ,Benthic zone ,010502 geochemistry & geophysics ,01 natural sciences ,Relative species abundance ,Geology ,0105 earth and related environmental sciences - Published
- 2017
46. Astronomical Calibration of the Ypresian Time Scale: Implications for Seafloor Spreading Rates and the Chaotic Behaviour of the Solar System?
- Author
-
Thomas Westerhold, Ursula Röhl, Thomas Frederichs, Claudia Agnini, Isabella Raffi, James C. Zachos, and Roy H. Wilkens
- Abstract
To fully understand the global climate dynamics of the warm early Eocene with its reoccurring hyperthermal events, an accurate high-fidelity age model is required. The Ypresian Stage (56–47.8 Ma) covers a key interval within the Eocene as it ranges from the warmest marine temperatures in the early Eocene to the long-term cooling trends in the middle Eocene. Despite the recent development of detailed marine isotope records spanning portions of the Ypresian Stage, key records to establish a complete astronomically calibrated age model for the Ypresian are still missing. Here we present new high-resolution X-ray fluorescence (XRF) core scanning Iron intensity, bulk stable isotope, calcareous nannofossil, and magnetostratigraphic data generated on core material from ODP Sites 1258 (Leg 207, Demerara Rise), 1262, 1263, 1265 and 1267 (Leg 208, Walvis Ridge) recovered in the Equatorial and South Atlantic Ocean. By combining new data with published records a 405-kyr eccentricity cyclostratigraphic framework was established, revealing a 300–400 kyr long condensed interval for Magnetochron C22n in the Leg 208 succession. Because the amplitudes are dominated by eccentricity, the XRF data help to identify the most suitable orbital solution for astronomical tuning of the Ypresian. Our new records fit best with the La2010b numerical solution for eccentricity, which was used as a target curve for compiling the Ypresian Astronomical Time Scale (YATS). The consistent positions of the very long eccentricity minima in the geological data and the La2010b solution suggest that the macroscopic feature displaying the chaotic diffusion of the planetary orbits, the transition from libration to circulation in the combination of angles in the precession motion of the orbits of Earth and Mars, occurred ~ 52 Ma ago. This is the first geological evidence for the chaotic behaviour of the solar system. Additionally, the new astrochronology and revised magnetostratigraphy provide robust ages and durations for Chrons C21n to C24n (47–54 Ma) revealing a major change in spreading rates in the interval from 51.0–52.5 Ma. Significantly, this major change in spreading rates is synchronous with a global reorganization of the plate-mantle system and the chaotic diffusion of the planetary orbits. Therefore, we hypothesize that changes in the gravitational interaction of the sun and the planets may have affected the dynamic mantle flow of the Earth triggering plate motion reorganisations ~ 52 Ma ago. Finally, the newly provided YATS also includes new absolute ages for bio- and magnetostratigraphic events/reversals and early Eocene hyperthermal events. Our new biomagnetostratigraphically calibrated stable isotope compilation may act as a reference for further paleoclimate studies of the Ypresian which is of special interest because of the outgoing warming and increasingly cooling phase.
- Published
- 2017
47. The DeepMIP contribution to PMIP4: experimental design for model simulations of the EECO, PETM, and pre-PETM (version 1.0)
- Author
-
Matthew Huber, James C Zachos, Paul Nicholas Pearson, Bridget S. Wade, Bette L. Otto-Bliesner, Sandy Kirtland Turner, Yannick Donnadieu, Allegra N. LeGrande, Reinhardt Kozdon, Petra Langebroek, Arne M.E. Winguth, Anna von der Heydt, Christine A. Shields, Paul J. Markwick, Michael Starz, Garland R. Upchurch, Srinath Krishnan, Scott L. Wing, Jean-Baptiste Ladant, Caroline H Lear, Kathryn E. Snell, Ran Feng, Richard E. Zeebe, Nicky M. Wright, Gregory J. L. Tourte, Edward Gasson, Henk A. Dijkstra, Rodrigo Caballero, Christopher J. Hollis, Jessica E. Tierney, Kate Littler, Michiel Baatsen, Robert L. Korty, Jeff Kiehl, Gordon N. Inglis, Aradhna Tripati, S. M. Jones, Eleni Anagnostou, James R Super, Clay R. Tabor, Gavin L. Foster, Rob DeConto, Ulrich Salzmann, Daniel J. Lunt, David Evans, Christopher J. Poulsen, School of Geographical Sciences [Bristol], University of Bristol [Bristol], Institute for Marine and Atmospheric Research [Utrecht] (IMAU), Utrecht University [Utrecht], Department of Meteorology [Stockholm] (MISU), Stockholm University, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Modélisation du climat (CLIM), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Aston University [Birmingham], University of Nottingham, UK (UON), NASA Goddard Space Flight Center (GSFC), Camborne School of Mines, College of Engineering, Mathematics and Physical Sciences, University of Exeter, National Center for Atmospheric Research [Boulder] (NCAR), Archäobotanik Afrikas, Goethe-Universität Frankfurt am Main, University of Arizona, Department of Earth Sciences, University of Cambridge, University of Cambridge [UK] (CAM), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Department of Earth Sciences [University of Cambridge], and University of St Andrews. Earth and Environmental Sciences
- Subjects
Solar constant ,010504 meteorology & atmospheric sciences ,Meteorology ,Climate change ,Earth and Planetary Sciences(all) ,Forcing (mathematics) ,010502 geochemistry & geophysics ,01 natural sciences ,Modelling and Simulation ,Paleoclimatology ,G1 ,SDG 13 - Climate Action ,QE ,QA Mathematics ,Greenhouse effect ,QA ,Palaeogeography ,ComputingMilieux_MISCELLANEOUS ,[SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography ,0105 earth and related environmental sciences ,[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,GE ,lcsh:QE1-996.5 ,G Geography (General) ,DAS ,lcsh:Geology ,Climate Action ,13. Climate action ,[SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology ,Paleoclimate Modelling Intercomparison Project ,Climatology ,Earth Sciences ,Climate model ,[SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology ,Geology ,GE Environmental Sciences - Abstract
We thank NERC grant NE/N006828/1 for providing funds for the first DeepMIP meeting in Boulder, Colorado, USA, in January 2016. Daniel J. Lunt acknowledges the NERC grant “Cretaceous–Paleocene–Eocene: Exploring Climate and Climate Sensitivity” (NE/K014757/1), and advanced ERC grant “The Greenhouse Earth System” (T-GRES, project reference 340923), awarded to Rich Pancost. Matthew Huber acknowledges funding from NSF OCE-0902882. Michiel L. J. Baatsen, Henk A. Dijkstra, and Anna S. von der Heydt acknowledge support by the Netherlands Earth System Science Centre (NESSC), financially supported by the Ministry of Education, Culture and Science (OCW), 024.002.001. Past warm periods provide an opportunity to evaluate climate models under extreme forcing scenarios, in particular high (> 800ppmv) atmospheric CO2 concentrations. Although a post hoc intercomparison of Eocene (∼ 50 Ma) climate model simulations and geological data has been carried out previously, models of past high-CO2 periods have never been evaluated in a consistent framework. Here, we present an experimental design for climate model simulations of three warm periods within the early Eocene and the latest Paleocene (the EECO, PETM, and pre-PETM). Together with the CMIP6 pre-industrial control and abrupt 4 × CO2 simulations, and additional sensitivity studies, these form the first phase of DeepMIP-the Deep-time Model Intercomparison Project, itself a group within the wider Paleoclimate Modelling Intercomparison Project (PMIP). The experimental design specifies and provides guidance on boundary conditions associated with palaeogeography, greenhouse gases, astronomical configuration, solar constant, land surface processes, and aerosols. Initial conditions, simulation length, and output variables are also specified. Finally, we explain how the geological data sets, which will be used to evaluate the simulations, will be developed. Publisher PDF
- Published
- 2017
48. THE 'TRANSITIONAL LAYER': AN EVENT BED THAT REPRESENTS THE IMMEDIATE AFTERMATH OF THE CHICXULUB IMPACT
- Author
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Jan Smit, Benjamin H. Passey, Timothy J Bralower, Michael T. Whalen, Sean S.P. Gulick, Joanna Morgan, Francisco J. Rodríguez-Tovar, James C Zachos, Heather L. Jones, Kenneth A. Farley, Vivi Vajda, Axel Wittmann, and Christopher M. Lowery
- Subjects
Event (relativity) ,Layer (object-oriented design) ,Geology ,Seismology - Published
- 2017
49. A high-resolution benthic stable-isotope record for the South Atlantic: Implications for orbital-scale changes in Late Paleocene–Early Eocene climate and carbon cycling
- Author
-
Ursula Röhl, Thomas Westerhold, Kate Littler, and James C Zachos
- Subjects
Milankovitch cycles ,Lysocline ,Orbital forcing ,Ocean acidification ,Cyclostratigraphy ,Paleontology ,Geophysics ,Oceanography ,Space and Planetary Science ,Geochemistry and Petrology ,Isotopes of carbon ,Paleoclimatology ,Earth and Planetary Sciences (miscellaneous) ,Paleogene ,Geology - Abstract
The Late Paleocene and Early Eocene were characterized by warm greenhouse climates, punctuated by a series of rapid warming and ocean acidification events known as “hyperthermals”, thought to have been paced or triggered by orbital cycles. While these hyperthermals, such as the Paleocene Eocene Thermal Maximum (PETM), have been studied in great detail, the background low-amplitude cycles seen in carbon and oxygen-isotope records throughout the Paleocene–Eocene have hitherto not been resolved. Here we present a 7.7 million year (myr) long, high-resolution, orbitally-tuned, benthic foraminiferal stable-isotope record spanning the late Paleocene and early Eocene interval (∼52.5–60.5 Ma) from Ocean Drilling Program (ODP) Site 1262, South Atlantic. This high resolution (∼2–4 kyr) record allows the changing character and phasing of orbitally-modulated cycles to be studied in unprecedented detail as it reflects the long-term trend in carbon cycle and climate over this interval. The main pacemaker in the benthic oxygen-isotope ( δ 18 O) and carbon-isotope ( δ 13 C) records from ODP Site 1262, are the long (405 kyr) and short (100 kyr) eccentricity cycles, and precession (21 kyr). Obliquity (41 kyr) is almost absent throughout the section except for a few brief intervals where it has a relatively weak influence. During the course of the Early Paleogene record, and particularly in the latest Paleocene, eccentricity-paced negative carbon-isotope excursions ( δ 13 C, CIEs) and coeval negative oxygen-isotope ( δ 18 O) excursions correspond to low carbonate (CaCO 3 ) and coarse fraction (%CF) values due to increased carbonate dissolution, suggesting shoaling of the lysocline and accompanied changes in the global exogenic carbon cycle. These negative CIEs and δ 18 O events coincide with maxima in eccentricity, with changes in δ 18 O leading changes in δ 13 C by ∼6 (±5) kyr in the 405-kyr band and by ∼3 (±1) kyr in the higher frequency 100-kyr band on average. However, these phase lags are not constant, with the lag in the 405-kyr band extending from ∼4 (±5) kyr to ∼21 (±2) kyr from the late Paleocene to the early Eocene, suggesting a progressively weaker coupling of climate and the carbon-cycle with time. The higher amplitude 405-kyr cycles in the latest Paleocene are associated with changes in bottom water temperature of 2–4 °C, while the most prominent 100 kyr-paced cycles can be accompanied by changes of up to 1.5 °C. Comparison of the 1262 record with a lower resolution, but orbitally-tuned benthic record for Site 1209 in the Pacific allows for verification of key features of the benthic isotope records which are global in scale including a key warming step at 57.7 Ma.
- Published
- 2014
50. Millennial-scale variations in western Sierra Nevada precipitation during the last glacial cycle MIS 4/3 transition
- Author
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Warren D. Sharp, John C. Tinsley, Greg M. Stock, James C Zachos, Isabel P. Montañez, Jessica L. Oster, Howard J. Spero, and Regina Mertz-Kraus
- Subjects
010506 paleontology ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,δ18O ,Northern Hemisphere ,Speleothem ,Stalagmite ,01 natural sciences ,Oceanography ,Arts and Humanities (miscellaneous) ,Cave ,Tropical climate ,General Earth and Planetary Sciences ,Stadial ,Glacial period ,Geology ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
Dansgaard–Oeschger (D–O) cycles had far-reaching effects on Northern Hemisphere and tropical climate systems during the last glacial period, yet the climatic response to D–O cycles in western North America is controversial, especially prior to 55 ka. We document changes in precipitation along the western slope of the central Sierra Nevada during early Marine Oxygen Isotope Stages (MIS) 3 and 4 (55–67 ka) from a U-series dated speleothem record from McLean's Cave. The timing of our multi-proxy geochemical dataset is coeval with D–O interstadials (15–18) and stadials, including Heinrich Event 6. The McLean's Cave stalagmite indicates warmer and drier conditions during Greenland interstadials (GISs 15–18), signified by elevated δ18O, δ13C, reflectance, and trace element concentrations, and less radiogenic 87Sr/86Sr. Our record extends evidence of a strong linkage between high-latitude warming and reduced precipitation in western North America to early MIS 3 and MIS 4. This record shows that the linkage persists in diverse global climate states, and documents the nature of the climatic response in central California to Heinrich Event 6.
- Published
- 2014
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