(Appendix) Total organic carbon, pyrolysis characteristics, and organic matter types at DSDP Holes 77-535 and 77-540

Lower to middle Cretaceous sediments in the eastern Gulf of Mexico are richer in organic matter and have a more marine organic facies than their counterparts in the nearby western North Atlantic, suggesting that the Gulf was the more productive of the two areas. As in the western North Atlantic, the rate of supply of terrestrial organic matter was high when the rate of supply of noncarbonate clastic materials was high (at times of low sea level) and diminished as sea level rose. The rate of supply of marine organic matter was lower in the Early Cretaceous than in the Cenomanian, perhaps in response to the global rise in sea level over this period. Where they are thermally mature, the organic matterrich units drilled at Sites 535 and 540 should be excellent sources for liquid hydrocarbons. The Pleistocene sediments of the eastern Gulf are dominated by terrestrial organic matter representing Mississippi River effluent.

墨西哥湾东部下白垩统至中白垩统沉积物，相较西北大西洋近岸的同期对应沉积物，有机质含量更为富集，且海相有机相占比更高，这表明墨西哥湾是这两个区域中沉积生产力更高的海域。与西北大西洋的沉积规律一致，当非碳酸盐碎屑物质供给速率升高（对应海平面下降时期）时，陆源有机质的供给速率也随之升高，并随海平面上升而降低。早白垩世海相有机质的供给速率低于森诺曼期，这或许与该时期全球海平面上升存在关联。在535号与540号钻探站位所钻获的热成熟度达标的富有机质层位，可作为优质液态烃源岩。墨西哥湾东部的更新统沉积物，以源自密西西比河径流的陆源有机质为主。