Integrated Analysis of Seismic Data Using Wireline Logs and Biostratigraphy: Examples from Texas Offshore Pliocene and Pleistocene

John M. Armentrout

Integration of high-resolution biostratigraphy with seismically defined depositional architecture permits correlation of biofacies and seismic facies within time-successive depositional sequences. Each step in the process requires critical evaluation and cross correlation of the data used, but the resultant analysis is significantly better than single-discipline interpretations.

Results from two examples of this procedure are presented, both from the High Island-Galveston South-East Breaks area of the eastern Texas continental shelf and upper slope. One example is characterized by relatively uniform cycles of sediment accumulation across a prograding shelf-slope system interrupted by growth-fault and salt-withdrawal basin architectures. A second example consists of a depositional architecture of multiple shelf-slope clinoforms relatively uncomplicated by structural movement.

The analysis of facies fabric within these depositional architectures provides a data base for defining a tentative depositional model for Pliocene-Pleistocene Gulf of Mexico siliciclastic sedimentation.

The general facies sequence can be summarized as four events. (1) Progradation of muddy clinoforms during lowering of sea level, trailed by the coastal-plain facies. With a very high rate of sediment input, the clinoforms oversteepen and slump. Additionally, multiple clinoform-slump packages form due to switching of the axis of sediment input at the top of the slope ramp. (2) Arrival of the delta-front/coastal facies at the physiographic shelf-slope break. Clinoforms continue aggrading and prograding, and river-fed turbidites bypass the slope-ramp, depositing as basinal aggradational mounds. (3) Transgression of the shelf due to rising sea level. Transgressive sands are deposited as the coastal plain facies of lowstand sea level are reworked. The basin becomes progressively sediment s arved with dominance of hemipelagic sedimentation. (4) The inner shelf deltaic-coastal plain facies during highstand sea level form depocenter thicks if coastline subsidence accommodates the volume of sediment, or form a thin, widely distributed layer due to delta-lobe switching.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.