THE FAYETTE BEDS. 49 



grains. It is of a gray to light buff color, and frequently contains lenticular 

 beds of very coarse sand with grains the size of a mustard seed. These lat- 

 ter evidently represent eddies, or pot-holes in the surface of the bed during 

 its deposition, as they often occur in very irregular and always in very local 

 patches. The sand beds frequently contain lenticular seams and nodules of 

 the same kind of watery-green clay that underlies them, and these often give 

 the impression of being eroded masses from a clay shore line. The strata 

 are all impregnated to a greater or less extent with carbonate of lime, some- 

 times occurring as a white cement in the interstices of the sand, and at others 

 in soft white nodules, a quarter of an inch to two inches in diameter, or as len- 

 ticular beds six to twelve inches thick. The amount of carbonate of lime in 

 these beds is much greater than that described by Hilgard* in the correspond- 

 ing strata of Mississippi and Louisiana. This great increase of calcareous mat- 

 ter can be easily explained, as in the case of the underlying Timber Belt sands 

 and clays, by the fact that the waters supplying the basin in which these sands 

 were deposited were much more heavily charged with carbonate of lime than 

 those of the other Gulf States. Of course, most, if not all, the calcareous 

 matter that was in solution was carried far out to sea, but a large part of that 

 in a state of mechanical suspension must have been deposited with the sands 

 under consideration. 



Roemer,f speaking of this country, says: " You see no solid rock in place 

 through the whole distance, excepting irregular layers of a coarse calcareous 

 sandstone of very modern origin exposed on the steep banks of some of the 

 rivers." The sand beds vary very much in their state of coherence. 

 Sometimes they are soft and loose, as the sands of the modern coastal bars, 

 but generally they are more or less hardened. The presence of carbonate 

 of lime has much to do with this state of induration, as it acts as a cement for 

 the sand, and frequently we find the latter in the state of a soft friable sand- 

 stone. Often, however, silica is the cementing material, and in some places we 

 find the sand beds hardened by this substance to such an extent that they al- 

 most approach the character of a quartzite. Such beds are seen at Quarry, 

 in the northern part of Washington County, where there are found hard 

 siliceous and semi-transparent strata, which are very valuable for economic 

 purposes. (See Building Stones.) Frequently the strata of the Fayette Beds 

 form reefs across the rivers, causing rapids, and sometimes much impeding 

 navigation. Such occurrences are seen above La Grange, on the Colorado, 

 and in many places on the Brazos, in Washington County. Iron pyrites is 



*"The Later Tertiary of the Gulf of Mexico," American Journal of Science, Yol. XXII, 

 July, 1881. 



f u A Sketch of the Geology of Texas," American Journal of Science and Arts, Second 

 Series, Yol. II, 1846, p. 359. 

 D 



