Sources and deposition of organic matter in Cretaceous passive margin deep-sea sediments: a synthesis of organic geochemical studies from Deep Sea Drilling Project Site 603, outer Hatteras Rise

Abstract

The results of organic geochemical studies of rock samples from Cretaceous strata at Site 603 on the outer Hatteras Rise are reviewed and integrated with their tithostratigraphic information. Although most of the strata contain little organic carbon, black shales enriched in organic matter were found in two settings. 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, except during the Cenomanian-Turonian, when the entire Atlantic Ocean may have briefly become anoxic. Organic matter in the sediments from all locations is thermally immature.

Petrographic characteristics and paleomires of Mand-Raigarh coals, Mahanadi Gondwana Basin, Chhattisgarh, India

“…But in general, (Table 4). These values reflect that the precursor materials for coal were derived from land plant organic matter (Meyers 1989(Meyers , 1994Dumitrescu and Brassell 2006;Bechtel et al 2007). The samples have low H/C (\1) except sample SXIBB3 which has H/C ratio more than one and the samples have relatively high O/C atomic ratios (0.05-0.59) typical of type III organic matter (Killops and Killops 2005).…”

Palaeoceanography of organic‐rich rocks of the Loma Chumico Formation of Costa Rica, Late Cretaceous, eastern Pacific

“…The disappearance of organic-rich rocks within the Loma Chumico Formation, and the predominance of organic-lean rocks in Campanian intervals of the Loma Chumico Formation and Sabana Grande Formations, may also be linked to the fundamental palaeoceanographic changes suggested by DSDP data from the central Atlantic and Caribbean. TOC data from central Atlantic DSDP sites indicate that the late Santonian-late Campanian Central Atlantic Ocean deep water mass probably had, on average, a higher dissolved oxygen content, based on the lack of organic-rich rocks of late Santonian-late Campanian age (Dean et al, 1977;Arthur & Natland, 1979;Arthur et al, 1984;Ruddiman et al, 1988;Meyers, 1989). One possible cause for elevated dissolved oxygen levels of the bottom water may have been more efficient mixing between the stagnant Atlantic and Tethyan saline waters, and newly created, colder proto-Antarctic Intermediate Water (AAIW).…”

Geochemistry and organic petrography of Cretaceous sediments of the Calabar Flank, southeastern, Nigeria

“…With the exception of Awi Formation samples (Aptian) that have carbon isotope values from-21.5& to À23.5&, all of the d 13 Corg values measured in the Calabar Flank Cretaceous sequences are more negative than the range of À22& to À18& typical of modern marine organic matter (Dean et al, 1986;Emerson and Hedges, 1988;Meyers, 1994). Similarly negative values have been reported in black shales of the North Atlantic basin during the late Cenomanian oceanic anoxic event (Kuypers , 2002) and are common in other mid-Cretaceous black shale sequences (e.g., Dean et al, 1986;Meyers, 1989;Menegetti et al, 1998;Hofmann et al, 2000;Tsikos et al, 2004;Kolonic et al, 2005). The observed trend in isotopic values for the marine OM compared to terrestrial OM is expected under climatic conditions that amplified the stratigraphic differences.…”