Abstract: Structural Styles and Depositional History of North and South Padre Island, OCS Areas, Offshore South Texas

Ali M. Al-Ghamdi, Joel S. Watkins

North and South Padre Island OCS areas were studied using 2-D seismic reflection data, check shot data, well logs and paleontological reports. Six salt structures occur beneath the present shelf edge. Shale occurs in over-pressured ridges beneath fault footwalls. We found that growth faults in the study, area are similar in style to that of growth faults in the Brazos OCS area. However, they differ in maximum expansion periods. The Clemente-Tomas fault system (Late Oligocene-Early Miocene) is located above an over-pressured shale ridge. The Corsair fault system (Early-Middle Miocene) formed due to a large sediment influx that forced salt to withdraw basinward. The Wanda fault system formed during the Late Miocene due to further salt withdrawal.

We defined five depositional sequences from the Miocene (18.0, 16.3, 13.4, 10.5, and 6.2 Ma). Nine mini-basins are in the study area and they are connected by three main sediments pathways. Mechanism of the basin formation is controlled by the nature of depocenter shift. Depocenters formed by salt withdrawal and sediment influx do not shift. On the other hand, depocenters shift is controlled by fault expansion and sediment influx.

We generated five stratigraphic cross-sections using detailed well log correlation to show the sand and shale sequences. Discontinuities in these sequences are common due to subsidence and the large number of faults in the study area. Presence of faults and shale bodies may cause formation of structural traps.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas