Publication Date:
2023-06-27
Description:
Black shales possessing high concentrations of organic carbon (Foresman, 1978, doi:10.2973/dsdp.proc.40.111.1978) were deposited in many parts of the proto South Atlantic Ocean during the Cretaceous period (Bolli et al., 1978, doi:10.2973/dsdp.proc.40.104.1978). The way such sediments accumulated is not fully understood, but is likely to have occurred through a combination of low oxygen availability and abundant supply of organic matter. Thin, centimetre-thick layers of black shales are commonly interbedded with thicker layers of organic carbon-deficient, green claystones, as found in strata of Aptian to Coniacian age, at Deep Sea Drilling Project (DSDP) Site 530, in the southern Angola Basin (Hay et al., 1982, doi:10.1130/0016-7606(1982)93〈1038:SAAOOC〉2.0.CO;2) and elsewhere. These differences in carbon content and colour reflect the conditions of deposition, and possibly variations in the supply of organic matter (Summerhayes and Masran, 1983, doi:10.2973/dsdp.proc.76.116.1983; Dean and Gardner, 1982). We have compared, using organic geochemical methods the compositions of organic matter in three pairs of closely-bedded black and green Cenomanian claystones obtained from Site 530. Kerogen analyses and distributions of biological markers show that the organic matter of the black shales is more marine and better preserved than that of the green claystones.
Keywords:
75-530A; Aliphatic hydrocarbons; Calcium carbonate; Carbon, organic, total; Carbon/Nitrogen ratio; Color description; Deep Sea Drilling Project; DRILL; Drilling/drill rig; DSDP; Glomar Challenger; Kerogen, amorphous; Leg75; n-Alkanoic acid, total per unit sediment mass; n-Alkanol, total per unit sediment mass; Polycyclic aromatic hydrocarbons; Pyrite, FeS2; Sample code/label; South Atlantic/RIDGE; Vitrinite
Type:
Dataset
Format:
text/tab-separated-values, 72 data points
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