Bulletin of the United States Geological Survey--Reconnaissance of the Rio Grande Coal Fields of Texas . , containing pebbles of slate, red quartzite, green-ish quartzite, cherty limestone, and red eruptive rock 50 (Just below 6 a much-decomposed greenish eruptive rock was seen, butit may not have been in place.) 15. Massive reddish rhyolite, containing in a portion of the bed vesicles that have been filled with chalcedony 20 4. Sands and clays 40 3. Sand^and clays, with occasional lenticular masses of conglomerate 60 2. Lenses of conglomerate 1-5 1. Laminated sandstone and clays, clays very s
Bulletin of the United States Geological Survey--Reconnaissance of the Rio Grande Coal Fields of Texas . , containing pebbles of slate, red quartzite, green-ish quartzite, cherty limestone, and red eruptive rock 50 (Just below 6 a much-decomposed greenish eruptive rock was seen, butit may not have been in place.) 15. Massive reddish rhyolite, containing in a portion of the bed vesicles that have been filled with chalcedony 20 4. Sands and clays 40 3. Sand^and clays, with occasional lenticular masses of conglomerate 60 2. Lenses of conglomerate 1-5 1. Laminated sandstone and clays, clays very sandy. The color of the rock is greenish, due to the presence of considerable quantities of 40 A small dike, striking east and west and cutting the lower part ofthe above series, was observed. This dike is probably of basalticmaterial. The dip where the above section was made is 4°+, S. 50° E. This section can be simplified and described as consisting of alternat-ing beds of sedimentaiy rocks and lava flows, or beds of rhyolitic 1 Determined from a study of thin sections by Dr. tjghan.] SECTIONS IN VICINITY OP SAN CARLOS. 77 Eroclastic material. The basalt occurs at about the center of thesction, and apparently is intrusive into the bed immediately over-ing it. The reasons for this conclusion are given in the discussion: No. 11 of the preceding section. In the sediments interbedded with the lavas and pyroclastics no>ssils were found, and we could not determine the precise age of theiries. For these interbedded lavas, pyroclastics, and sedimentste name Vieja series is proposed, from the Vieja Mountains, whereLey are well exposed and where they were studied. SECTIONS IN THE VICINITY OF SAN CARLOS. ction of the Vieja Mountains from the San Carlos arroyo, 1 mile below San Carlos, tothe top of the mountain east of the town. (PI. VIII; PI. XI, fig. 2.) Rim rock, a greenish-yellow rock, containing large phenocrysts of anor- thoclase feldspar, determine
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