ABSTRACT

Local extensive paleo-channels exist with the upper to lower Wilcox Group (Paleocene-Eocene) of the Gulf Coast of North America. Recent reports document paleo-channels of the Wilcox Group: Bejuco-La Laja, Chicontepec, DeSoto, Nautla, Ovejas, St. Landry, and Yoakum. An eighth channel, the Tyler (Hardin) channel suggests that passive submarine erosional forces shaped the channels prior to any active erosional forces such as those related to turbidity currents.

The north-south trending Tyler (Hardin) channel is 24 mi (40 km) long and 12 mi (20 km) wide and displays over 1000 ft (300 m) of shale fill. The channel thalweg bifurcates updip into two meandering steep-walled channels which display numerous side gullies.

The channel grew from the youthful to the mature stage through massive erosive mechanisms and during the mature stage may have been further enlarged by more active erosional agents such as turbidity currents. Old age began with increased peralic sedimentation and infilling of the channel with deep-marine shale. Eventually, progradation and eustatic drop in sea level dried the channel, its younger fill and older adjacent deposits.

Paleo-channels are silient economic features. The deep-marine shale infill of the channel acts as a source of oil and gas and a seal for adjacent reservoir rock. Upward migration of oil through fractures, faults, and sediments fills reservoirs in overlying structures formed in nearshore deposits of the upper Wilcox. Most of the major oil and gas fields of the Wilcox Group in Tyler and Hardin Counties are localized in the structures above the underlying channel fill.