Paleoredox chemistry of Cenomanian–Coniacian black shales at high paleolatitudes: Implications for the extent of anoxia during OAE2
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Paleoredox chemistry of Cenomanian–Coniacian black shales at high paleolatitudes: Implications for the extent of anoxia during OAE2. / Lenniger, Marc; Nøhr-Hansen, Henrik; Hills, Len V; Bjerrum, Christian J.
In: Mineralogical Magazine, Vol. 77, No. 5, 2013, p. 1585.Research output: Contribution to journal › Conference abstract in journal › Research
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T1 - Paleoredox chemistry of Cenomanian–Coniacian black shales at high paleolatitudes: Implications for the extent of anoxia during OAE2
AU - Lenniger, Marc
AU - Nøhr-Hansen, Henrik
AU - Hills, Len V
AU - Bjerrum, Christian J.
PY - 2013
Y1 - 2013
N2 - Cretaceous oceanic anoxic events (OAEs) have been studied in detail during the last decades. OAE2 is of particular interest as it reflects one of the largest perturbations of the global carbon cycle in the Mesozoic. It is characterised by awidespread deposition of organic rich sediments which is reflected by a positive carbon isotope excursion (CIE) in the terrestrial and marine record. Whereas the paleoredox conditions in low and mid-paleolatitudes are well constrainedfor OAE2, data from high paleolatitudes are still scarce.The paleoceanographic response at high paleolatitudes during OAE2 is here characterized by samples from Axel Heiberg Island in Canada. Preliminary palynological analyses indicate a Late Cenomanian!Coniacian age for the section.Bulk organic carbon isotope data have been corrected using the hydrogen index (Rock Eval pyrolysis) to account for changes in organic matter sourcing. Our corrected isotope record correlates in detail with the European carbonatereference curve and confirms our biostratigraphic model. Iron speciation (FeHR/FeT and FePy/ FeHR) data point to anoxic but non-euxinic conditions at high paleolatitudes during OAE2.Furthermore the Sverdrup Basin was intermittently suboxic to anoxic (ferruginous) throughout most of the latest Cenomanian–Coniacian. Despite very high TOC (>10%) and hydrogen index values, molybdenum concentrations arerelatively low during OAE2 but increase after the event. This suggests a global drawdown of the seawater molybdenum reservoir caused by the widespread extent of ocean anoxia/euxinia in the Cretaceous oceans during OAE2.
AB - Cretaceous oceanic anoxic events (OAEs) have been studied in detail during the last decades. OAE2 is of particular interest as it reflects one of the largest perturbations of the global carbon cycle in the Mesozoic. It is characterised by awidespread deposition of organic rich sediments which is reflected by a positive carbon isotope excursion (CIE) in the terrestrial and marine record. Whereas the paleoredox conditions in low and mid-paleolatitudes are well constrainedfor OAE2, data from high paleolatitudes are still scarce.The paleoceanographic response at high paleolatitudes during OAE2 is here characterized by samples from Axel Heiberg Island in Canada. Preliminary palynological analyses indicate a Late Cenomanian!Coniacian age for the section.Bulk organic carbon isotope data have been corrected using the hydrogen index (Rock Eval pyrolysis) to account for changes in organic matter sourcing. Our corrected isotope record correlates in detail with the European carbonatereference curve and confirms our biostratigraphic model. Iron speciation (FeHR/FeT and FePy/ FeHR) data point to anoxic but non-euxinic conditions at high paleolatitudes during OAE2.Furthermore the Sverdrup Basin was intermittently suboxic to anoxic (ferruginous) throughout most of the latest Cenomanian–Coniacian. Despite very high TOC (>10%) and hydrogen index values, molybdenum concentrations arerelatively low during OAE2 but increase after the event. This suggests a global drawdown of the seawater molybdenum reservoir caused by the widespread extent of ocean anoxia/euxinia in the Cretaceous oceans during OAE2.
U2 - 10.1180/minmag.2013.077.5.12
DO - 10.1180/minmag.2013.077.5.12
M3 - Conference abstract in journal
VL - 77
SP - 1585
JO - Mineralogical Magazine
JF - Mineralogical Magazine
SN - 0026-461X
IS - 5
ER -
ID: 49753168