Ocean-wide stagnation episode in the late Cretaceous

Graciansky, P. C. de; Deroo, G.; Herbin, J. P.; Montadert, L.; Müller, Carla; Silva, André; Sigal, Jacques

doi:10.1038/308346a0

Cited by 119 publications

(42 citation statements)

References 7 publications

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“…A period of high productivity, a greatly intensified and expanded oxygenminimum zone, or deep-water anoxia have been discussed as possibilities (e.g., de Graciansky et al, 1984;Herbin et al, 1986). Enhanced proportions of marine organic matter and diminished sediment-accumulation rates are two features common to Cenomanian-Turonian deposits in the Atlantic (Stein, 1986;Stein et al, 1986); both are consistent with the section from Hole 641 A.…”

Section: Paleoceanographic Implicationssupporting

confidence: 63%

“…At Hole 641A, the abbreviated Cenomanian-Turonian section argues against downslope redeposition, and the concentrations of organic carbon, although elevated, do not indicate a time of greatly enhanced marine productivity, as is recorded in sediments from Site 367 off northwestern Africa (e.g., Herbin et al, 1986). Enhanced preservation of the mixture of marine and continental organic matter found in rocks from Hole 641A probably resulted from a period of deep-water anoxia (de Graciansky et al, 1984;Stein, 1986).…”

Section: Paleoceanographic Implicationsmentioning

confidence: 99%

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Organic Geochemistry of Cretaceous Black Shales and Adjacent Strata from the Galicia Margin, North Atlantic Ocean

Dunham¹,

Meyers²,

Ho³

1988

Proceedings of the Ocean Drilling Program

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Organic-carbon-rich "black shales" and adjacent organic-carbon-poor rocks from three different Cretaceous settings encountered during ODP Leg 103 have been studied by organic geochemical methods. Rock-Eval analysis, carbon isotope data, and lipid biomarkers show organic matter to contain varying proportions of marine and continental materials. In Hauterivian-Barremian organic-carbon-rich marlstone turbidites, large amounts of land-derived organic matter are found. Aptian-Albian black-colored shales are interspersed within green claystones, from which they differ by containing more marine organic matter. An abbreviated layer of black shale from the Cenomanian/Turonian boundary is dominated by well-preserved marine organic matter. Downslope transport and rapid reburial within a predominantly oxygenated deep-water setting created most of these examples of black shales, except for the Cenomanian-Turonian deposits in which deep-water anoxia may have been involved.

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Section: Paleoceanographic Implicationssupporting

confidence: 63%

Section: Paleoceanographic Implicationsmentioning

confidence: 99%

Organic Geochemistry of Cretaceous Black Shales and Adjacent Strata from the Galicia Margin, North Atlantic Ocean

Dunham¹,

Meyers²,

Ho³

1988

Proceedings of the Ocean Drilling Program

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“…OAE II has been causally connected with the opening of the deep-water gateway between the North and South Atlantic that may have allowed the influx of a dense water mass that if volumetrically significant could have displaced nutrient rich deep-waters resulting in rapid ocean overturning and advection of a low N/P ratio water mass to the surface [Arthur and Natland, 1979;Arthur et al, 1987;Kuypers et al, 2002b;Summerhayes, 1987;Tucholke et al, 1979]. A widespread hiatus near the C/T boundary in the late Cenomanian in the South Atlantic [Zimmerman et al, 1987] and Tethys [de Graciansky et al, 1984] may be due to the initiation of this deep-water connection and erosive currents [Wagner and Pletsch, 2001] between the North and South Atlantic and may record this connection. The models of Poulsen et al [2001Poulsen et al [ , 2003 and Handoh et al [1999] demonstrate that the opening of the North-South Atlantic gateway could have been responsible for reorganization of deep-water circulation patterns resulting in introduction of water from the South Atlantic into the North Atlantic basin.…”

Section: C-t Boundary Eventmentioning

confidence: 99%

Nitrogen cycling during the Cretaceous, Cenomanian‐Turonian Oceanic Anoxic Event II

Junium

Arthur

2007

Geochem Geophys Geosyst

147

135

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Low δ15N values, ranging from +1.2‰ to −3.9‰, and atomic carbon/nitrogen (C/N) ratios of 25–50 are characteristic of “black shales” deposited during the Cenomanian‐Turonian boundary interval and Oceanic Anoxic Event II (OAE II). An observed antithetic relationship between C/N ratios and δ15N could suggest a predominance of terrestrially derived organic matter or a diagenetic control on δ15N variability shifting bulk δ15N values lower. However, Hydrogen Indices (HI) generally >450, and a positive correlation of HI with C/N mitigates against a significant terrestrial organic matter fraction. High C/N values are likely the result preferential degradation of labile, N‐rich compounds during early diagenesis and loss of N as ammonium from sediments through time. A hypothetical model that considers the degradation of a 15N‐enriched labile protein fraction yields only small, 1–2‰ negative shifts in δ15N. However, 15N depletion during diagenesis is contrary to normal isotope kinetics which should result in 15N enrichment of bulk organic matter. Therefore we conclude that the bulk δ15N values in this study reflect primary changes in the nitrogen cycle. The δ15N data support the hypothesis of expanded nitrogen fixation driven by upwelling of nutrient‐nitrogen poor, phosphorus replete waters during OAE II and from the mid‐Cenomanian to Santonian at Demerara Rise. The low δ15N values, which are significantly lower than bulk δ15N values in modern regions where nitrogen fixation is known to be important, probably result from a more significant fraction of dissolved inorganic nitrogen being produced by nitrogen fixation. During the peak of OAE II a marked shift to lower δ15N values is observed. This shift possibly reflects greater utilization of 15N‐depleted ammonium during a chemocline upward excursion (CUE). Dominance of low δ15N values from other periods of more widespread marine anoxia is likely the result of similar processes.

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“…Nonetheless, the overall productivity of the western North Atlantic was probably low to moderate, on the basis of sediment compositions (Waples, 1983;de Graciansky et al, 1984;Bralower and Thierstein, 1984). Indeed, Demaison and Moore (1980) comment on the lack of correlation in modern oceans between productivity and preservation of marine organic matter.…”

Section: Factors Contributing To Deposition Of Black Shales At Site 603mentioning

confidence: 99%

“…Possible explanations of black shale depositional conditions are exemplified by de Graciansky et al (1982), Summerhayes and Masran (1983), and Summerhayes (in press) and combine the effects of sea-level changes, changes in continental climates, nutrient availability, and basin morphology to achieve periods of mid water or bottom anoxia in the Mesozoic North Atlantic. It is probable that these are the important factors, but de Graciansky et al (1984) caution that a simple model employing one set of conditions appears inadequate to explain the geographically broad extent of Cenomanian black shales. Similar caution may be appropriate in seeking explanations of black shale formation in other parts of the geological record as well.…”

Section: Factors Contributing To Deposition Of Black Shales At Site 603mentioning

confidence: 99%

Synthesis of Organic Geochemical Studies, Deep Sea Drilling Project Leg 93, North American Continental Margin

Meyers¹

1987

Initial Reports of the Deep Sea Drilling Project

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The results of organic geochemical studies of samples from Site 603 on the outer Hatteras Rise and from Sites 604 and 605 on the New Jersey continental slope are reviewed and integrated with lithostratigraphic information from those locations. Although most of the sediments and rocks encountered at all three sites contain little organic carbon, "black shales" enriched in organic matter were found in Cretaceous strata obtained from Hole 603B. These rocks exist as claystones in the Aptian to Turonian Hatteras Formation and as marlstones in the Neocomian Blake-Bahama Formation. Terrigenous organic matter predominates in these deposits, except in Cenomanian and Valanginian rocks, where marine material becomes dominant. Organic carbon concentrations in Cenomanian black claystones are higher than any previously reported from the western North Atlantic, but lower than the concentrations found in the eastern North Atlantic. Black shales at Site 603 appear to result from downslope transport and rapid reburial of coastal and ocean margin sediments by turbidity flows. Deep-basin anoxia is not a major factor. At Site 605, a well-defined Cretaceous/Tertiary boundary was obtained, and terrigenous components of the organic matter diminished in sediments deposited above this boundary. Organic matter in the sediments from all locations is thermally immature.

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Ocean-wide stagnation episode in the late Cretaceous

Cited by 119 publications

References 7 publications

Organic Geochemistry of Cretaceous Black Shales and Adjacent Strata from the Galicia Margin, North Atlantic Ocean

Organic Geochemistry of Cretaceous Black Shales and Adjacent Strata from the Galicia Margin, North Atlantic Ocean

Nitrogen cycling during the Cretaceous, Cenomanian‐Turonian Oceanic Anoxic Event II

Synthesis of Organic Geochemical Studies, Deep Sea Drilling Project Leg 93, North American Continental Margin

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