Buried Hill at Wilcox-Carrizo Contact in East Texas

Reprinted from American Association of Petroleum Geologists Bulletin, v. 35, no. 8, 1951. A recently discovered buried hill, at least 77 feet high, is composed of strata of the Wilcox group (lower Eocene) and covered on its flanks by cross-bedded sands of the lower Carrizo and at the top by level-bedded shales and silts of the upper Carrizo formation. Peculiar small funnel-shaped pits filled with Carrizo sand extend into the underlying Wilcox ball clay at the peak of the hill. Other extensions fill shrinkage cracks of the clay. These and other features of the contact demonstrate a disconformity at the base of the Carrizo sand caused by rejuvenation that occurred shortly before Carrizo sand deposition.