Environmental Geology of Continental Margin Off Central and South Texas in Atlas Format: ABSTRACT

Abstract

Integrated environmental studies keyed to understanding fundamental processes and their interrelations were conducted from 1974 through 1977. Most of the aspects investigated were sampled seasonally to provide data on variations within each year and among the 3 years studied. The geologic and related hydrographic, biologic, and chemical data have been compiled in an atlas format consisting of topical overlays so that interrelations are apparent. Three atlases, each covering a geographic area of 2° × 1°, have been completed: Port Isabel, Corpus Christi, and Beeville. Each, in addition to bathymetry and the lease-block grid, consists of seven topical maps: location of oil and gas fields and production installations; water circulation and rates of sedimentation; trace-metals content and texture of surficial bottom sediments (plus seasonal variations); nature of shallow subsurface sediments and biogeology; post-Wisconsin sedimentation patterns and tectonism; late Pleistocene and Holocene depositional environments; and structure of the continenta terrace with emphasis on the chronology of faulting and seafloor stability. Results of the study indicate that water circulation is strongly seasonal, but both local variations and differences in surface and bottom movement are evident. Sedimentation rates have been relatively high throughout the Holocene, averaging almost 1 m/1,000 years; rates now are as much as 9 mm/year locally, based on 210Pb dating. Seasonal differences in both the texture and trace-metals content of surficial bottom sediments are characteristic and probably can be related to variations in infaunal activity and movement of bottom sediments. Faulting has migrated progressively seaward across the shelf with time; movement during the Holocene has been mainly near the shelf edge. Slumping has been extensive along parts of the outer shelf and on the upper continental slope. End_of_Article - Last_Page 420------------