NICHOL, SCOTT, L., Dalhousie University, Halifax, Nova Scotia, Canada; RON BOYD, University of Newcastle, Newcastle, NSW, Australia; and SHEA PENLAND, Louisiana Geological Survey, Baton Rouge, LA

ABSTRACT: Stratigraphy of a Wave-Dominated Estuary: Lake Calcasieu, Louisiana

Late Quaternary fluvial and estuarine deposits within the 92 km long Lake Calcasieu incised valley were documented from vibracore, borehole records and high resolution shallow seismic data. Estuarine sedimentation has been influenced by a low fair weather wave energy, storm-affected, microtidal environment, coupled with relative sea level rise of 0.62 cm per year. Three major facies units are recognized in the Calcasieu valley fill: (1) A tide-influenced fluvial facies along the upper 56 km of the estuary. Maximum valley depths here are 30 m. Floodplain, interdistributary basin, fluvial channel and bay-head delta subfacies comprise this portion of the valley fill; (2) A 2-10 m thick central basin facies with fringing intertidal salt marsh. Valley depths here are 10-15 m, with disconti uous lowstand alluvial deposits as the basal facies, and; (3) A low-relief prograded barrier that separates the estuary from the Gulf of Mexico. The 22 km long barrier includes chenier and beach ridge deposits with intervening and fringing marsh facies, and a tidal inlet. The barrier is 6-7 m thick and attains a maximum width of 4.4 km.

A type 1 sequence boundary occurs at the unconformity between lowstand alluvial deposits and underlying Pleistocene Prairie Terrace

deposits. The base of the transgressive systems tract correlates with the marine flooding surface, marked by the contact between lowstand alluvial and bay-head deltaand transgressive central basin deposits. The highstand systems tract is represented by both aggradational (floodplain, channel, central basin and marsh facies) and progradational (bay-head delta and chenier plain facies) parasequences.

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