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Geochemical Assessment of Depositional Previous HitEnvironmentsNext Hit Using Oil Molecular Data


Carbon and hydrogen isotopic data and biomarkers from oils, allowed the assessment, identification and differentiation of lacustrine and marine source rock depositional Previous HitenvironmentsNext Hit. The samples studied were recovered from Latin American syn-rift, sag and drift stages of Cretaceous and Tertiary ages. Two Previous HitenvironmentsNext Hit were identified in the syn-rift stage: (i) Lower Neocomian deep, fresh to brackish water lacustrine (Reconcavo basin, Brazil), (ii) Upper Neocomian shallow hypersaline lake (Sergipe basin, Brazil). Two Previous HitenvironmentsNext Hit were identified in sag basins: (iii) Tithonian semi-restricted shallow marine carbonate (Chiapas basin, Mexico), (iv) Aptian marine evaporitic. Four Previous HitenvironmentsNext Hit were identified in a drift stage: (v) Cenomanian-Turonian deep marine carbonate (Maracaibo basin, Venezuela), (vi) Miocene marine Previous HitdeltaicNext Hit siliciclastic system (Lower Magdalena basin, Colombia), (vii) Miocene marine Previous HitdeltaicNext Hit system with carbonatic influence (Foz de Amazonas basin, Brazil), and (vii) Oligocene marine Previous HitdeltaicNext Hit proximal (Plato basin, Colombia).

Within the tectono-sedimentary settings, successive sea level changes or expansions and contractions of the lacustrine water bodies, created variations in water column salinity and temperature and, hence, the development of water stratification and bottom water anoxia. These differences can be identified using only oil samples, without the need of actual source rock data. Even when oils or depositional Previous HitenvironmentsTop are mixed, individual components and their relative contributions can be assessed.

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.