Calcium isotope composition of Morozovella over the late Paleocene–early Eocene

Geology ◽  
2021 ◽  
Author(s):  
Gabriella D. Kitch ◽  
Andrew D. Jacobson ◽  
Dustin T. Harper ◽  
Matthew T. Hurtgen ◽  
Bradley B. Sageman ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Calcium Isotope ◽  
Ocean Drilling Program ◽  
Ocean Drilling ◽  
Carbonate Ion ◽  
Kinetic Isotope ◽  
Carbon Isotope Excursion ◽  
Thermal Maximum ◽  
Igneous Province ◽  
North Atlantic Igneous Province

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.

scholarly journals Tropical Atlantic climate and ecosystem regime shifts during the Paleocene–Eocene Thermal Maximum

2018 ◽  
Vol 14 (1) ◽  
pp. 39-55 ◽  
Author(s):  
Joost Frieling ◽  
Gert-Jan Reichart ◽  
Jack J. Middelburg ◽  
Ursula Röhl ◽  
Thomas Westerhold ◽  
...  
Keyword(s):  
Heat Stress ◽  
Environmental Variability ◽  
Equatorial Atlantic ◽  
Ocean Drilling Program ◽  
Tropical Regions ◽  
Surface Ocean ◽  
Ocean Drilling ◽  
Carbon Isotope Excursion ◽  
Thermal Maximum ◽  
Surface Dwelling

Abstract. The Paleocene–Eocene Thermal Maximum (PETM, 56 Ma) was a phase of rapid global warming associated with massive carbon input into the ocean–atmosphere system from a 13C-depleted reservoir. Many midlatitude and high-latitude sections have been studied and document changes in salinity, hydrology and sedimentation, deoxygenation, biotic overturning, and migrations, but detailed records from tropical regions are lacking. Here, we study the PETM at Ocean Drilling Program (ODP) Site 959 in the equatorial Atlantic using a range of organic and inorganic proxies and couple these with dinoflagellate cyst (dinocyst) assemblage analysis. The PETM at Site 959 was previously found to be marked by a  ∼  3.8 ‰ negative carbon isotope excursion (CIE) and a  ∼  4 °C surface ocean warming from the uppermost Paleocene to peak PETM, of which  ∼  1 °C occurs before the onset of the CIE. We record upper Paleocene dinocyst assemblages that are similar to PETM assemblages as found in extratropical regions, confirming poleward migrations of ecosystems during the PETM. The early stages of the PETM are marked by a typical acme of the tropical genus Apectodinium, which reaches abundances of up to 95 %. Subsequently, dinocyst abundances diminish greatly, as do carbonate and pyritized silicate microfossils. The combined paleoenvironmental information from Site 959 and a close-by shelf site in Nigeria implies the general absence of eukaryotic surface-dwelling microplankton during peak PETM warmth in the eastern equatorial Atlantic, most likely caused by heat stress. We hypothesize, based on a literature survey, that heat stress might have reduced calcification in more tropical regions, potentially contributing to reduced deep sea carbonate accumulation rates, and, by buffering acidification, also to biological carbonate compensation of the injected carbon during the PETM. Crucially, abundant organic benthic foraminiferal linings imply sustained export production, likely driven by prokaryotes. In sharp contrast, the recovery of the CIE yields rapid (≪ 10 kyr) fluctuations in the abundance of several dinocyst groups, suggesting extreme ecosystem and environmental variability.

scholarly journals Tropical Atlantic Climate and Ecosystem Regime Shifts during the Paleocene-Eocene Thermal Maximum

2017 ◽  
Author(s):  
Joost Frieling ◽  
Gert-Jan Reichart ◽  
Jack J. Middelburg ◽  
Ursula Röhl ◽  
Thomas Westerhold ◽  
...  
Keyword(s):  
Environmental Variability ◽  
Equatorial Atlantic ◽  
Ocean Drilling Program ◽  
Tropical Regions ◽  
Surface Ocean ◽  
Ocean Drilling ◽  
Carbon Isotope Excursion ◽  
Thermal Maximum ◽  
Surface Dwelling ◽  
Upper Paleocene

Abstract. The Paleocene – Eocene Thermal Maximum (PETM; 56 Ma) was a phase of rapid global warming associated with massive carbon input into the ocean-atmosphere system from a 13C-depleted reservoir. Many mid- and high-latitude sections have been studied and document changes in salinity, hydrology and sedimentation, deoxygenation, biotic overturning and migrations, but detailed records from tropical regions are lacking. Here, we study the PETM at Ocean Drilling Program (ODP) Site 959 in the equatorial Atlantic using a range of organic and inorganic proxies and couple these with dinoflagellate cyst (dinocyst) assemblage analysis. The PETM at Site 959 was previously found to be marked by a ~3.8 ‰ negative carbon isotope excursion (CIE), and a ~4 ºC surface ocean warming from the uppermost Paleocene to peak PETM, of which ~1 ºC occurs before the onset of the CIE. We record upper Paleocene dinocyst assemblages that are similar to PETM assemblages as found in extra-tropical regions, confirming poleward migrations of ecosystems during the PETM. The early stages of the PETM are marked by a typical acme of the tropical genus Apectodinium, which reaches abundances of up to 95 %. Subsequently, dinocyst abundances diminish greatly, as do carbonate and pyritized silicate microfossils. The combined paleoenvironmental information from Site 959 and a close by shelf site in Nigeria implies the general absence of eukaryotic surface-dwelling microplankton during peak PETM warmth is most likely caused by heat stress. Crucially, abundant organic benthic foraminiferal linings imply sustained export production, likely driven by prokaryotes. In sharp contrast, the recovery of the CIE yields rapid (≪10 kyr) fluctuations in the abundance of several dinocyst groups, suggesting extreme ecosystem and environmental variability.

scholarly journals Paleocene/Eocene carbon feedbacks triggered by volcanic activity

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sev Kender ◽  
Kara Bogus ◽  
Gunver K. Pedersen ◽  
Karen Dybkjær ◽  
Tamsin A. Mather ◽  
...  
Keyword(s):  
North Atlantic ◽  
Proxy Records ◽  
The North ◽  
The Earth ◽  
Thermal Maximum ◽  
Igneous Province ◽  
Carbon Release ◽  
Carbon Reservoir ◽  
Earth’S Climate ◽  
North Atlantic Igneous Province

AbstractThe Paleocene–Eocene Thermal Maximum (PETM) was a period of geologically-rapid carbon release and global warming ~56 million years ago. Although modelling, outcrop and proxy records suggest volcanic carbon release occurred, it has not yet been possible to identify the PETM trigger, or if multiple reservoirs of carbon were involved. Here we report elevated levels of mercury relative to organic carbon—a proxy for volcanism—directly preceding and within the early PETM from two North Sea sedimentary cores, signifying pulsed volcanism from the North Atlantic Igneous Province likely provided the trigger and subsequently sustained elevated CO2. However, the PETM onset coincides with a mercury low, suggesting at least one other carbon reservoir released significant greenhouse gases in response to initial warming. Our results support the existence of ‘tipping points’ in the Earth system, which can trigger release of additional carbon reservoirs and drive Earth’s climate into a hotter state.

scholarly journals Insensitivity of alkenone carbon isotopes to atmospheric CO<sub>2</sub> at low to moderate CO<sub>2</sub> levels

2019 ◽  
Vol 15 (2) ◽  
pp. 539-554 ◽  
Author(s):  
Marcus P. S. Badger ◽  
Thomas B. Chalk ◽  
Gavin L. Foster ◽  
Paul R. Bown ◽  
Samantha J. Gibbs ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Ice Core ◽  
Co2 Uptake ◽  
Geological Time ◽  
Ocean Drilling Program ◽  
Time Intervals ◽  
Ocean Drilling ◽  
The Past ◽  
Global Carbon ◽  
Carbon System

Abstract. Atmospheric pCO2 is a critical component of the global carbon system and is considered to be the major control of Earth's past, present, and future climate. Accurate and precise reconstructions of its concentration through geological time are therefore crucial to our understanding of the Earth system. Ice core records document pCO2 for the past 800 kyr, but at no point during this interval were CO2 levels higher than today. Interpretation of older pCO2 has been hampered by discrepancies during some time intervals between two of the main ocean-based proxy methods used to reconstruct pCO2: the carbon isotope fractionation that occurs during photosynthesis as recorded by haptophyte biomarkers (alkenones) and the boron isotope composition (δ11B) of foraminifer shells. Here, we present alkenone and δ11B-based pCO2 reconstructions generated from the same samples from the Pliocene and across a Pleistocene glacial–interglacial cycle at Ocean Drilling Program (ODP) Site 999. We find a muted response to pCO2 in the alkenone record compared to contemporaneous ice core and δ11B records, suggesting caution in the interpretation of alkenone-based records at low pCO2 levels. This is possibly caused by the physiology of CO2 uptake in the haptophytes. Our new understanding resolves some of the inconsistencies between the proxies and highlights that caution may be required when interpreting alkenone-based reconstructions of pCO2.

scholarly journals Drilling disturbance and constraints on the onset of the Paleocene/Eocene boundary carbon isotope excursion in New Jersey

2014 ◽  
Vol 10 (4) ◽  
pp. 3303-3325 ◽  
Author(s):  
P. N. Pearson ◽  
E. Thomas
Keyword(s):  
New Jersey ◽  
Carbon Isotope ◽  
Supporting Evidence ◽  
Drilling Mud ◽  
Ocean Drilling Program ◽  
Surface Ocean ◽  
Turbid Waters ◽  
Carbon Isotope Excursion ◽  
Thermal Maximum ◽  
The Impact

Abstract. The onset of the Paleocene/Eocene thermal maximum (PETM) and associated carbon isotope excursion (CIE; about 56 million years ago) was geologically abrupt but it is debated whether it took thousands of years or was effectively instantaneous. A significant new record of the onset of the CIE was published by Wright and Schaller (2013) who claimed that it could be resolved across 13 annual layers in a drill core through the Marlboro Clay at Millville, New Jersey (Ocean Drilling Program Leg 174X). Supporting evidence of similar layering was also reported from another New Jersey drill site, Wilson Lake B, and a photograph of the Marlboro Clay in outcrop. Such a short duration would imply an instantaneous perturbation of the atmosphere and surface ocean, and the impact of a comet or asteroid as the likely cause. However it was suggested by Pearson and Nicholas (2014) from the published photographs that the layers in the Marlboro Clay could be artifacts of drilling disturbance (so-called "biscuiting", wherein the formation is fractured into layers or "biscuits" and drilling mud is injected in between). Here we report new observations on the cores which support that interpretation, including concentric grooves on the surfaces of the biscuits caused by spinning in the bit, micro-fracturing at their edges, and injected drilling mud. We re-interpret the outcrop evidence as showing joints rather than sedimentary layers. We argue that foraminifer concentrations in the sediments are far too high for the layers to be annually deposited in turbid waters at depths of 40–70 m, indicating that the onset of the CIE in the Marlboro Clay likely took on the order of millennia, not years. Re-coring of Millville to minimize drilling disturbance and allow a higher resolution study of the carbon isotope excursion is highly desirable.

scholarly journals Drilling disturbance and constraints on the onset of the Paleocene–Eocene boundary carbon isotope excursion in New Jersey

2015 ◽  
Vol 11 (1) ◽  
pp. 95-104 ◽  
Author(s):  
P. N. Pearson ◽  
E. Thomas
Keyword(s):  
New Jersey ◽  
Carbon Isotope ◽  
Supporting Evidence ◽  
Drilling Mud ◽  
Ocean Drilling Program ◽  
Surface Ocean ◽  
Turbid Waters ◽  
Carbon Isotope Excursion ◽  
Thermal Maximum ◽  
The Impact

Abstract. The onset of the Paleocene–Eocene thermal maximum (PETM) and associated carbon isotope excursion (CIE; approx. 56 Mya) was geologically abrupt, but it is debated whether it took thousands of years or was effectively instantaneous. Wright and Schaller (2013) published a significant new record of the onset of the CIE, and claimed that it could be resolved across 13 annual layers in a drill core through the Marlboro clay at Millville, New Jersey (Ocean Drilling Program (ODP) Leg 174X). Supporting evidence for similar layering was reported from another New Jersey drill site, Wilson Lake B, and a photograph of the Marlboro clay in outcrop (Wright and Schaller, 2014). Such a short duration would imply an instantaneous perturbation of the atmosphere and surface ocean and the impact of a comet or asteroid as the likely cause. However, Pearson and Nicholas (2014) suggested, based on the published core photographs, that the layers in the Marlboro clay cores could be artifacts of drilling disturbance, so-called biscuiting, wherein the formation is fractured into layers or biscuits and drilling mud is injected in between the layers. (We now prefer the term core discing following Kidd, 1978.) Here we report new observations on the cores which support that interpretation, including concentric grooves on the surfaces of the core discs caused by spinning in the bit, micro-fracturing at their edges, and injected drilling mud. We re-interpret the limited outcrop evidence as showing joints rather than sedimentary layers. We argue that foraminifer concentrations in the sediments are far too high for the layers to have been annually deposited in turbid waters at depths of 40–70 m, indicating that the onset of the CIE in the Marlboro clay likely took on the order of millennia, not years (Zeebe et al., 2014). Re-coring of Millville aimed at minimizing drilling disturbance to allow a higher-resolution study of the carbon isotope excursion is highly desirable.

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