Rates of Sediment Deposition during the Late Eocene of Central Texas Based on 40Ar/39Ar Dating of Volcanic Ash
New high-precision radiometric dates are available for eight Upper Eocene volcanic ash beds in the Brazos River Valley of East Texas that provide age control for determining the rate of sediment accumulation of Yegua and Jackson strata during the Late Eocene. One volcanic ash date was determined from the late Middle Eocene and five additional dates were determined for areas outside the Brazos River Valley. These dates indicate similar rates of sediment accumulation for a 580 m (1900 ft) section of strata in east-central Texas at a rate of approximately 160 m (525 ft) per million years for the last 3 million year interval of the Late Eocene. In the outcrop belt, strata of this interval are characterized by cyclic deposition and a similar periodicity of cycles. Cyclic units in Jackson Group strata of Brazos County have a duration of ~320,000 yr.
AAPG Datapages/Search and Discovery Article #90219 © 2015 GCAGS, Houston, Texas, September 20-22, 2015