Paleo-Currents in Eocene to Jurassic Strata of North Central Louisiana

Douglas A. Carlson
Louisiana Geological Survey, Louisiana State University, Baton Rouge, LA

It appears from examination of dipmeter log data that paleo-currents in north-central Louisiana vary in a systematic manner in terms of dip magnitude and azimuth throughout the region as a function of unit depth, lateral position and unit lithology. This study examined approximately 43,000 dip magnitude and azimuths readings from 32 dipmeter logs located in Bienville, Claiborne, Lincoln, Union and Webster Parishes, which include strata from Eocene Wilcox to Jurassic Smackover. Approximately 94% of the 43,000 discontinuities are considered to be sedimentary depositional features because their dip angles are less than 20 degrees, typically 1 to 6 degrees.

Magnitudes of average dip and standard deviation of dip typically increase down the stratigraphic section. The largest magnitude of average dip within the Pearsall, Sligo and Hosston Formations is in the north-central Claiborne Parish and near the junction of Claiborne, Bienville and Webster Parishes. In the Cotton Valley Group and Smackover Formation the largest average dip values cluster around the Homer Dome in southwestern Claiborne Parish.

From an initial examination it appears that in general trend of dip azimuth modes is toward the south and away from the Monroe and Sabine Uplifts and toward the northern Louisiana salt basins. Typically within each of seven borings that penetrated five or more stratigraphic units mode of dip azimuth is fairly consistent. For six borings with fairly consistent unit dip azimuths the average standard deviation is 30 degrees. The study results indicate consistently systematic variations in paleocurrent directions at the time of sediment implacement that indicate typically that paleo currents in north-central Louisiana were towards the northern Louisiana salt basins and away from Monroe and Sabine Uplifts.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas