Caractérisation par différentes méthodes physico-chimiques de types de matière organique dans des sédiments du Crétacé d'Atlantique en mer profonde

Geochemical characterizations of the Cretaceous formations at Site 603 are quite comparable with those at Site 105. In the Blake-Bahama and the Hatteras formations, the petroleum potential is medium (<5 kg HC/t of rock) to very low (<0.5 kg HC/t of rock), and the organic matter is mainly of type III origin, that is, terrestrial. At the top of the Hatteras Formation, there is a condensed series, which chiefly contains organic matter of type II origin, with up to 20 wt.% total organic carbon content in Core 603B-34 and 25 wt.% in Core 105-9. This accumulation corresponds to the Cenomanian/Turonian boundary event. An examination of dinoflagellates in the kerogen concentration assigns dates to the samples studied by organic geochemistry. The Cenomanian and Turonian age of the organic-matter-rich black claystones indicates a low rate of sedimentation, about 1 m/Ma. Furthermore, the occurrence of type II organic matter indicates an anoxic environment with insufficient oxygen renewal to oxidize the sinking hemipelagic organic matter. This organic enrichment is not related to local phenomena but to sedimentation over an extended area, because deposits are well known in various areas with different paleodepths in the North Atlantic.

Section: Nature Of the Organic Mattermentioning

confidence: 95%

Cretaceous Formations from the Lower Continental Rise off Cape Hatteras: Organic Geochemistry, Dinoflagellate Cysts, and the Cenomanian/Turonian Boundary Event at Sites 603 (Leg 93) and 105 (Leg 11)

Herbin¹,

Masure²,

Roucache³

1987

“…This would be indicative of an immature material derived from higher plants. In the same carbon-number range, cyclic molecules of the sterane and triterpane series should be present, as indicated by more detailed analyses (GC/MS) of other Cretaceous oceanic materials (Roucaché et al, 1979). Such compounds are more likely to be derived from marine material (Fig.…”

Section: Humic Compounds (Table 2)mentioning

confidence: 99%

Organic Geochemistry of Upper JurassicCretaceous Sediments from Site 511, Leg 71, Western South Atlantic

Deroo¹,

Herbin²,

Roucache³

1983

Self Cite

“…Most of the samples from the mouth of the Gulf and the central Guaymas Basin mainly contain inert, terrigenous organic matter, whereas the sediment from the Guaymas Basin slope is enriched in liptinites and contains more marine organic matter. The organic matter from the Basin is Type III kerogen; that from the slope resembles Type II kerogens (Espitalié et al, 1977;Roucaché et al, 1979).…”

Section: Amount and Type Of Organic Mattermentioning

confidence: 99%

“…The hydrogen index values are low, and all samples are grouped near the Type III trend line. Our classification follows the scheme of Roucaché et al (1979) for immature, Cretaceous deep-sea sediment from the Atlantic Ocean.…”

Section: Site 474 Mouth Of Gulf Of Californiamentioning

confidence: 99%

Organic Petrography and Extractable Hydrocarbons of Sediments from the Gulf of California, Deep Sea Drilling Project Leg 64

Rullkötter¹,

Dick²,

Welte³

1982

We determined the quantity, type, and maturity of organic matter in Pleistocene sediment from the Gulf of California. We analyzed extractable hydrocarbons by capillary column chromatography and combined gas chromatography/mass spectrometry (GC/MS). We investigated kerogens by Rock-Eval pyrolysis and microscopy. Organic carbon is mostly between 1 and 2°7o in samples from the mouth of the Gulf (Holes 474 and 474A) and in the Guaymas Basin (Holes 478, 481, and 481 A) and between 2 and 4% at the Guaymas Basin slope (Hole 479). We determined total extracts of about 10 mg/g C org for all samples. The organic matter seems to be mostly terrigenous in Holes 474,474A, 478,481, and 481 A, as indicated by the extractable hydrocarbons and the macefal analysis. But we believe that the large amounts of steroid and triterpenoid hydrocarbons in some samples indicate marine and bacterial biomass, which probably is finely disseminated and cannot readily be identified under the microscope. Rederived, inert organic matter is common in these holes. In Hole 479, the terrigenous contribution is less pronounced, and algal liptinites exceed terrigenous liptinites. But in all samples, perylene is the predominant aromatic hydrocarbon. Optical and chemical investigations show that the organic matter in the Gulf of California sediment is immature, despite the high heat flow and local basaltic intrusions. We could not establish a regular maturity trend with increasing depth.