18 GULF TERTIARY OF TEXAS. 



of deposition the Texas Eocene closely resembles that of Mississippi, the dif- 

 ferent stages of which, according to Hilgard,* "are intimately interconnected 

 by community of species, from Claiborne to Vicksburg." 



The Texas Eocene contains many Claiborne and Jackson species, but the 

 Vicksburg, so far as is yet known, is but very sparingly represented, as but 

 three or four characteristic forms of that epoch were found among many fossils 

 collected on the Brazos and Colorado rivers in the region where the Vicksburg 

 strata might have been expected to occur. This is in accordance with the 

 observations of Hilgard at Sabinetown, Texas, concerning which he says: 

 " At the base of the Grand Gulf Rocks we find on the Bayou Taureau a seam 

 of shell limestone with Vicksburg fossils. "We then pass over the lignito- 

 gypseous strata to Sabinetown, Texas, where we see about seventy feet of 

 these overlying ledges of blue fossiliferous limestone, alternating every two 

 or three feet with what would be green sand marl, like that of Vicksburg, 

 had not the lime of the numerous shells, of which it contains casts, been re- 

 moved by subsequent dissolution. So far as I have seen, the usual leading 

 fossils of Vicksburg are wanting here, while the greater sandiness of the ma- 

 terials, as well as the prevalence of shallow-sea bivalves, indicates their depo- 

 sition in shallower waters." The uppermost fossiliferous strata below the 

 Fayette Beds (Grand Gulf) in Texas are represented on the Brazos by the 

 Moseley's Ferry Beds, and on the Colorado by the White Marl Bluff Beds. 

 Both these deposits show Claiborne and Jackson species, with a tendency 

 toward an increase of the Jackson over the Claiborne as we ascend the series; 

 yet the stratigraphical representatives of these beds in Mississippi and Louis- 

 iana contain a typical Vicksburg fauna. Above the Moseley's Ferry and 

 White Marl Bluff Beds are a series of clays with lignite, silicified wood, and 

 other evidences of a land deposit. Similar deposits, but probably developed 

 on a much smaller scale, overlie the Vicksburg strata in the above mentioned 

 States. Consequently it seems possible that while the Vicksburg deposits were 

 being laid down in the Mississippi embayment, a land era existed in the part 

 of Texas just mentioned, ana that this accounts for the much greater devel- 

 opment in Texas than in the Mississippi region of the fresh water or lagoon 

 clays, which overlie the last marine strata of the Eocene. Hilgard states that 

 the Vicksburg period closed with a more decided tendency to a deep sea 

 fauna than any other epoch of the Eocene. Hence it seems possible that the 

 same oscillation that caused this phenomenon may have also raised the Texas 

 region into a land area. Also the lignitic character of some of the beds of 

 the Vicksburg strata increases very much to the westward, and therefore it 

 would be expected, if this kept up, to run into purely non-marine deposits, f 



* "The Old Tertiary of the Southwest," Am. Jour, of Science, Vol. XXX, Oct., 1885, p. 267. 

 f "On the Geological History of the G-ulf of Mexico," American Journal of Science and 

 Arts, Vol. 2, December, 1871, p. 6. 



