YE, QIUCHENG, WILLIAM E. GALLOWAY, CLIFF FROHLICH, and STONEY GAN, Department of Geological Sciences, University of Texas, Austin, TX; and ROBLEY MATTHEWS, Brown University, Providence, RI

ABSTRACT: High Frequency Glacio-Eustatic Cyclicity in the Early Miocene Coastal and Shelf Depositional Systems, NW Gulf of Mexico Basin

High frequency glacio-eustatic sea level change is one of the major factors that control late Paleogene and Neogene clastic sedimentation. Study of such high-frequency cyclicity will greatly improve the understanding of reservoir stratification and compartmentalization. The Lower Miocene genetic stratigraphic sequence records one of the major Cenozoic depositional episodes of the NW Gulf of Mexico basin. The (ca. 9 Ma.) episode was characterized by moderate to high rate of sediment influx and deposition (500 to 1300 m/Ma at outer shelf position) and was bounded by extended intervals of reduced sediment supply, producing regional flooding of the deltaic and shore-zone depositional system array. Preliminary study shows that the shore-zone and shelf depositional systems of the lower Mioc ne have well developed high-frequency cyclicity: a total of 95 cycles have been identified on well logs, averaging about 100 Ky/cycle. The thicknesses of these parasequence scale cycles vary from 30 to 80 ft (10-25 m). Vertically, several to tens of these cycles are stacked together and show lower frequency sea level fluctuations. These cycle packages are the most correlatable features within the stratigraphy. By removing the effect of local tectonic subsidence and sediment supply using backstripping methods, we will be able to evaluate the role of glacio-eustatic sea level changes played on these cycles. The final result will be cross-checked by STRATA-various model simulation using an independently derived high-frequency glacio-eustatic Miocene sea level curve.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.