Bulletin - University of Texas Mineral Survey Volume 5-9 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1902 Excerpt: ...under the gravels of the Rio Grande flats. An isolated outcrop was also found about six miles to the south-southeast of Shafter, and this exposed the lower members. This is in the basin of Morita creek, and the rocks occur in a narrow belt a mile and a half long, following this stream from northeast to southwest. For convenience in description the series will be considered in several divisions, beginning below, and taking them in ascending order. These divisions will be designated as indicated in the following table: (See also Fig. 2.) Section of the Chinati Series. Thickness In feet. The Cibolo Beds. 8. The Yellow Limestone 659 8. The Thin-bedded Zone i70 6. The Zone of Sponge Spicules 85 5. The Lower Brecciated Zone 13j- 4. The Transition Beds 100 The Alta Beds. 3. The Yellow Sand JO 2. The Dark Shales 2000 The Cieneguita Beds. 1. Basal deposits 1000 The Cieneguita Beds. The lowest of the Carboniferous sediments consist of a series of dark or almost black shales, alternating with heavy lenticular masses of mortar rocks1, conglomerates, dark limestones and of mixtures of these materials. Some of these masses are upward of thirty feet in thickness and extend for more than a mile horizontally. The shale constitutes the greater part of the division. In places it contains some layers of black chert and in the lower part some greenish glauconitic? seams were noted, and also some flattened round concretions containing a dark grayish powdery material. Farthest down, close to a granite boss, against which this shale lies, four granite or gneiss boulders, considerably decayed, were found imbedded in it. They ranged from two to four feet in diameter, and were considerably more micaceous than the intrusive granite which occurs close by, and apparently different ...