THE TIMBER BELT OR SABINE RIVER BEDS. 43 



Similar strata are seen from here to the San Tomas coal mines.* These are 

 situated on the Texas side of the river and at the mouth of San Tomas Creek, 

 about twenty-five miles by river above Laredo. The following section shows 

 the occurrence of the coalrf 



1. Calcareous sands 12 feet. 



2. Friable sandstone 12 feet. 



3. Chocolate, gray, white, and brown clays, with sulphur and gypsum crystals 



in layers, running downward into black clays, with a two-inch seam of 



woody lignite a few inches above 4 10 feet. 



4. Coal, massive glossy black conchoidal fracture, but sometimes having the 



form of bituminous coal 1% feet. 



5. Hard black clay 2 inches. 



6. Coal, same as 4 1£ feet. 



7. Gray clays containing lignite seams, directly under the coal.. 10 feet. 



For three miles below this are seen indurated greenish clays with leaf im- 

 pressions, broken stems, and specks of lignite. Occasionally seams of choco- 

 late clay and calcareous nodules are found. As usual, the bluffs are capped 

 with pebbles or sand, and dip two degrees southeast. Fifteen miles above 

 Laredo is a bluff reaching a maximum height of forty feet, and about a mile 

 long. It is composed of interbedded coarse sand with calcareous nodules, 

 and sandy clay with gypsum and sulphur. The sand grains are red, yellow, 

 white, and gray, and the whole bluff has a greenish appearance, spotted in 

 places by ferruginous matter. Many similar outcrops are seen for seven miles 

 below, and as the dip is often horizontal, or nearly so, the exposures show 

 simply different parts of the same bed. Eight miles above Laredo is a bluff 

 about eighty feet high and a half mile long, composed of semi-indurated buff 

 sands with an undulating dip. Similar exposures are seen down the river to 

 Laredo, and in fact that town is built partly on the same beds. In limestone 

 from this place Professor Heilprin has found Cardita densata, Turritella cari- 

 nata, and other Claiborne fossils. J One mile below the town are seen highly 

 calcareous sandstones, soft on a weathered surface, hard and flinty inside, and 

 associated with chocolate clays. Large quantities of iron pyrites are found 

 all through the formation, as well as specks of lignite, grains of glauconite, 

 and often an efflorescence of sulphur. Five miles below Laredo, a large bed 

 composed of fragments of an oyster was found in the following associations : 



*Dr. C. A. White refers the coal of Maverick and Webb counties to the "Fox Hills" or to 

 the "Laramie" formation. American Journal of Science. Vol. XXXIII, p. 19, January, 

 1887. 



fFor description of coal, see "Economic Geology.." 



^"Contributions to the Tertiary Geology ana Paleontology of the United States." 



