THE TIMBER BELT OR SABINE RIYER BEDS. 45 



Oardita, Crassatellaf, oysters and shark teeth. The shell bed contains specks 

 of lignite, and the shells are mostly in fragments. Small white calcareous 

 concretions are numerous. Dip, 1 to 2 degrees southeast. 



Similar outcrops, hut non-fossiliferous, are seen down the river to a point 

 twelve miles below San Ignacio. The sandstones vary from very friable to 

 hard and compact, and often loose masses lie on the slopes of the bluffs like 

 slabs of flagstone. Throughout this whole distance of twenty-one miles the 

 strata all dip to the northeast at an angle of from 1 to 10 degrees, and in one 

 place, five miles below San Ignacio, they dip 10 degrees northwest. This is 

 the greatest and longest variation in the normal southeast or east dip that has 

 been seen by the writer anywhere in the formations under discussion. The 

 strata do not show any other evi ience of having been upthrown or disturbed 

 in any way, and it seems probable that this abnormal dip is due simply to 

 the natural sinking and contraction of the strata as explained on page 16. 

 Below here on the river are seen many local dips to the northeast of 5 to 8 

 degrees, but they never prevail for more than a mile or so. Four miles above 

 the Texas town of Carnzo, and on the Mexican side of the river, is seen a 

 bed of woody lignite one and a half to two feet thick, overlaid by ten feet of 

 buff sands and underlaid to the water's edge by four feet of greenish-gray 

 clay. The Rio Salad o flows into the Rio Grande from the Mexican side op- 

 posite Carrizo. The town of Guererro is on this river, six miles from the 

 mouth, and in this distance are seen many outcrops of buff sandstone, often 

 rising in abrupt ledges through the river alluvium. Most of the houses, 

 churches, and fences of the town are built of it. Similar rocks are seen for 

 sixteen miles below Carrizo on the Rio Grande, and dip at an angle of 2 to 6 

 degrees southeast. At this point a small creek on the Texas side cuts through 

 a series of low ledges of interstratified buff sandstones, containing gray con- 

 cretions and chocolate black and greenish-blue semi-indurated clays, dipping 

 1 to 2 degrees southeast. In the bed of the creek were found many fossils, 

 mostly oysters, and fragments of silicified wood. Thence down the river for 

 nine miles similar, but unf ossiliferous, ledges are seen. At the end of this dis- 

 tance is a bluff forty feet high, composed of interbedded hard and soft calca- 

 reous sandstones and clay seams, and containing many Cardita and Crassatella. 

 Numerous calcareous concretions are found, and the sand occasionally con- 

 tains coarse black and gray siliceous grains the size of a mustard seed and 

 larger. Three miles below here, and half a mile above the Starr County line, 

 is a low bluff composed of gray clay and capped by a bed, six to eight inches 

 thick, of shell rock with specks of glauconite, Cardita, and many gasteropods 

 (Turritella, etc.). Eight miles below the western line of Starr County the fol- 

 lowing section was seen: 



