THE INFLUENCE OF DELTA SYSTEM EVOLUTION ON UPPER SLOPE SEDIMENTATION
Fraticelli, C.M, and Anderson, J.B. Department of Geology & Geophysics, Rice University
The Brazos, Colorado, and Trinity River systems have, over the last glacio-eustatic cycle (125 ka ˝ present), responded to both sea-level and climatic fluctuations. These responses are easily seen as each delta system progrades, backsteps, avulses, and incises across the Texas shelf. Although the fluvial systems are adjacent, and appear to be very similar, there are a number of significant differences between them including variations in sediment supply characteristics, dominant precipitation and vegetation regimes, discharge, sensitivity to climate, and geology within the drainage basin. This variability causes each system to behave in its own unique manner to climatic and eustatic changes. Because upper slope sediments originate from these delta systems, one can expect the deposits on the slope to reflect some of the variability found in the deltas.
Re-examination of cores drilled by Shell in the mid-1960Ýs on the upper slope has allowed for correlations of lithologic units found on the slope with deltaic events occurring on the shelf. A history of the Colorado, Brazos, and Trinity systems has been established by identification of the major depositional units and the emplacement of a chronostratigraphic framework. Ten cores, located just basinward of these delta systems, have been correlated in detail using sedimentology, paleontology, and high resolution seismic lines. Using the established chronostratigraphic framework, these two data sets have been integrated resulting in associations between slope sedimentation and fluvial-deltaic system dynamics.