Decoupling of the carbon cycle during Ocean Anoxic Event 2

Eldrett, James S; Minisini, Daniel; Bergman, Steven C.

doi:10.1130/g35520.1

Cited by 131 publications

(137 citation statements)

References 24 publications

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“…In particular, our record from the Maverick Sub-basin from a starved, distal part of the KWIS demonstrates that the maximum organic carbon accumulation and preservation occurred during the early to middle Cenomanian (95e97 Ma), which does not correspond with the global peak in organic-matter sequestration at the C-T boundary indicated by the positive global CIE. Similarly, the recorded decrease in carbon preservation during the OAE-2 interval in Iona-1 (Eldrett et al, 2014) is also observed further to the north in the KWIS (e.g. Sageman and Lyons, 2003).…”

Section: Accumulation Rates and Lithologymentioning

confidence: 57%

“…Sageman and Lyons, 2003). This indicates that massive carbon sequestration occurred in some other region than the KWIS (e.g., Kuypers et al, 2004;Trabucho Alexandre et al, 2010;Jim enez Berrocoso et al, 2010;Eldrett et al, 2014). Carbonate mass accumulation rates are highest in both marl and limestone lithologies in the underlying Buda Limestone and overlying Austin Chalk suggesting relatively reduced carbonate productivity during Eagle Ford deposition.…”

Section: Accumulation Rates and Lithologymentioning

confidence: 92%

“…This interval in particular was characterized by the widespread deposition of organic-rich, fine-grained sediment marked by a globally recognized positive carbon isotope excursion (CIE) reflecting the widespread removal of 12 C-enriched organic matter in marine sediments under global anoxic conditions (see Jenkyns, 2010 and references therein). However, the exact timing of this inferred global OAE-2 event is still debated with recent studies showing diachroneity between the deposition of the organic-rich sediment and the CIE (e.g., Sageman et al, 1997;Tsikos et al, 2004;Meyers et al, 2005;Meyers, 2007;Trabucho Alexandre et al, 2010;Eldrett et al, 2014), whereas interpretations vary on the precise timing and origin of the trigger (Mitchell et al, 2008;Turgeon and Creaser, 2008;Du Vivier et al, 2014;Eldrett et al, 2014;Laurin et al, 2015).…”

Section: Introductionmentioning

confidence: 96%

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An astronomically calibrated stratigraphy of the Cenomanian, Turonian and earliest Coniacian from the Cretaceous Western Interior Seaway, USA: Implications for global chronostratigraphy

Eldrett

Bergman

et al. 2015

Cretaceous Research

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156

154

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Section: Accumulation Rates and Lithologymentioning

confidence: 57%

Section: Accumulation Rates and Lithologymentioning

confidence: 92%

Section: Introductionmentioning

confidence: 96%

See 1 more Smart Citation

An astronomically calibrated stratigraphy of the Cenomanian, Turonian and earliest Coniacian from the Cretaceous Western Interior Seaway, USA: Implications for global chronostratigraphy

Eldrett

Bergman

et al. 2015

Cretaceous Research

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156

154

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“…A sea level rise associated with the LowerÀUpper Eagle Ford Formation boundary marks the transition from restricted-circulation, Tethys-influenced conditions from the south to more boreal, open marine-influenced conditions from the north (Eldrett et al 2014). Despite a globally contemporaneous d 13 C excursion, sediments from the Upper Eagle Ford Formation and coeval sediments in Colorado, i.e.…”

Section: Geological Settingmentioning

confidence: 99%

“…the Portland-1 core at Pueblo, were mostly oxygenated during OAE-2, as indicated by limited or no enrichment in redox-sensitive elements (Meyers 2007, fig. 4;Eldrett et al 2014). Donovan & Staerker (2010) suggested a depositional setting for Lozier Canyon and Comstock West on a submarine platform at a likely distance of 300À500 km from the nearest landmass and water depths of approximately 60 m during commencement of deposition of the Lower Eagle Ford Formation.…”

Section: Geological Settingmentioning

confidence: 99%

Palynostratigraphy and palaeoenvironments of the Eagle Ford Group (Upper Cretaceous) at the Lozier Canyon outcrop reference section, west Texas, USA

Dodsworth¹

2015

Palynology

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This study describes the detailed palynology of the Eagle Ford Group at Lozier Canyon, its principal outcrop reference section in west Texas. Prominent marine phytoplankton assemblages are consistent with a proposed depositional setting for Lozier Canyon on a submarine platform within the Cretaceous Western Interior Seaway (KWIS) of the USA. The Lower Eagle Ford Formation (middle to upper Cenomanian) was deposited under restricted marine conditions with oxygen-deficient, probably anoxic bottom waters, as indicated by the black, organic-rich (ca. 1 to > 6% total organic carbon) shale lithology. The formation comprises two fourth-order stratigraphical sequences, each showing sedimentary evidence of increasing water depth during deposition. Palynomorph assemblages from the sequences are dominated by green algal prasinophyte phycomata in the lower parts and peridinioid dinoflagellate cysts in the upper parts. The productivity of these marine phytoplankton groups may have been stimulated by availability of ammonium (prasinophytes) and nitrite (peridinioids) from upwelling, or vertical expansion of the oxygen-minimum zone. The transition from prasinophyte-to peridinioid-dominated assemblages may reflect elevation of the photic zone to a level less regularly encroached by deeper, ammonium-enriched waters of the denitrification zone. The overlying Upper Eagle Ford Formation (upper Cenomanian to upper Turonian or Coniacian) was deposited under deeper, relatively open marine conditions, as indicated by a decrease in organic carbon content and an increase in carbonate content. This is supported by the presence of diversified dinoflagellate cyst assemblages, including inter-regional (high-to mid-latitude) marker events; in the upper Cenomanian, base and acme Cyclonephelium compactum-membraniphorum, top consistent and frequent Litosphaeridium siphoniphorum, and top Adnatosphaeridium tutulosum; in the middle to upper Turonian, range bases of Heterosphaeridium difficile and Senoniasphaera rotundata. The stratigraphical resolution offered by palynology indicates potential application to wellsite 'geosteering' of commercial shale oil and shale gas wells drilled in the Eagle Ford Group.

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Upper ocean oxygenation dynamics from I/Ca ratios during the Cenomanian‐Turonian OAE 2

et al. 2015

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Global warming lowers the solubility of gases in the ocean and drives an enhanced hydrological cycle with increased nutrient loads delivered to the oceans, leading to increases in organic production, the degradation of which causes a further decrease in dissolved oxygen. In extreme cases in the geological past, this trajectory has led to catastrophic marine oxygen depletion during the so-called oceanic anoxic events (OAEs). How the water column oscillated between generally oxic conditions and local/global anoxia remains a challenging question, exacerbated by a lack of sensitive redox proxies, especially for the suboxic window. To address this problem, we use bulk carbonate I/Ca to reconstruct subtle redox changes in the upper ocean water column at seven sites recording the Cretaceous OAE 2. In general, I/Ca ratios were relatively low preceding and during the OAE interval, indicating deep suboxic or anoxic waters exchanging directly with near-surface waters. However, individual sites display a wide range of initial values and excursions in I/Ca through the OAE interval, reflecting the importance of local controls and suggesting a high spatial variability in redox state. Both I/Ca and an Earth System Model suggest that the northeast proto-Atlantic had notably higher oxygen levels in the upper water column than the rest of the North Atlantic, indicating that anoxia was not global during OAE 2 and that important regional differences in redox conditions existed. A lack of correlation with calcium, lithium, and carbon isotope records suggests that neither enhanced global weathering nor carbon burial was a dominant control on the I/Ca proxy during OAE 2.

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Decoupling of the carbon cycle during Ocean Anoxic Event 2

Cited by 131 publications

References 24 publications

An astronomically calibrated stratigraphy of the Cenomanian, Turonian and earliest Coniacian from the Cretaceous Western Interior Seaway, USA: Implications for global chronostratigraphy

An astronomically calibrated stratigraphy of the Cenomanian, Turonian and earliest Coniacian from the Cretaceous Western Interior Seaway, USA: Implications for global chronostratigraphy

Palynostratigraphy and palaeoenvironments of the Eagle Ford Group (Upper Cretaceous) at the Lozier Canyon outcrop reference section, west Texas, USA

Upper ocean oxygenation dynamics from I/Ca ratios during the Cenomanian‐Turonian OAE 2

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