Petroleum Systems of Deep-Water Basins - Gulf Coast Section SEPM

Late Mesozoic and Cenozoic Deposystem Evolution
in the Eastern Gulf of Mexico:
Implications for Hydrocarbon Migration
Richard H. Fillon
Earth Studies Associates
3730 Rue Nichole
New Orleans, Louisiana 70131
e-mail: fillorh@bellsouth.net
Abstract
A preliminary analysis of Mesozoic and Cenozoic deposystems in the eastern Gulf of Mexico, using published
regional stratigraphic and depth to basement studies, reveals striking elements of deposystem history and petroleum
system architecture. Integration of thirteen regional studies into a single chronostratigraphic framework provides a
basis for assessing accumulation rates within eight provisional Late Mesozoic second-order depositional sequences
and eight Cenozoic second-order depositional sequences spanning the interval 165 Ma to the present.
Interval accumulation rate mapping reveals that major deposystems shifted in response to the changing tectonic
setting of the Gulf basin. The evolving deposystems reflect changes in sequence architecture corresponding to evolution
from a dynamic environment of salt tectonics and hot mobile crust in the youthful Gulf basin to cool thermally
stable modern crust where gravity driven depositional patterns dominate. Shifting depocenters throughout this period
differentially loaded and compacted underlying sediments, thus modifying pressure gradients that influence the lateral
migration pathways of hydrocarbons. Analysis of differential deposystem loading predicts that hydrocarbon migration
paths locally converge within the original Federal lease sale 181 area, principally because Late Cretaceous strata
in the area are relatively thin compared to adjacent areas. While perceived hydrocarbon risk is therefore diminished,
low accumulation rates for most sequences suggest that reservoir risk in a given vertical section is high. The search for
productive reservoir in the area should therefore focus on specific parts of the section immediately above or below a
condensed Middle Cretaceous Sequence Boundary (MCSB) interval that exhibit accumulation rates higher than the
regional average. Accordingly, the late Albian-early Cenomanian (Paluxy sequence) and the middle to late Miocene
(upper Miocene sequence) are preferred candidates for exploration.
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