Organic facies variations in the Mesozoic South Atlantic DSDP Holes

Visual kerogen and total organic carbon determinations indicate that there are two periods of organic enrichment events in the Mesozoic sediments of the South Atlantic. The first period, from the Late Jurassic through the late Aptian, is recorded in sediments from the Falkland Plateau, the Cape Basin, and the Angola Basin. Apparently, salinity stratification in the restricted basin, coupled with rising sea level, led to bottom water anoxia and organic enrichment. The second event, from the late Albian to the Santonian period, is recorded in sediments from the Angola Basin and the Sao Paulo Plateau. It appears to have been caused by development of an anoxic oxygen minimum zone at midwater depths. Organic matter sedimentation in the Mesozoic South Atlantic is controlled by geologic, climatic, eustatic, and Oceanographic factors.干酪根目视鉴定与总有机碳（Total Organic Carbon）测定结果表明，南大西洋中生代沉积物中存在两期有机质富集事件。第一期事件时限为晚侏罗世至阿普第晚期，其沉积记录留存于福克兰高原（Falkland Plateau）、开普盆地（Cape Basin）与安哥拉盆地（Angola Basin）的沉积物中。显然，局限盆地内的盐度分层作用叠加海平面上升，引发了底层水体缺氧与有机质富集。第二期事件时限为阿尔布晚期至桑托期，其沉积记录见于安哥拉盆地与圣保罗高原（Sao Paulo Plateau）的沉积物中。该事件的成因似乎为中层水深处发育的缺氧型最低含氧带。南大西洋中生代的有机质沉积作用受控于地质、气候、海面升降与海洋学多重因素。