ULTIMA THULE AND ANTOINE SECTIONS. 309 



described by McGee as the Appomattox or Lafayette formation, and 

 which is the Plateau gravel of my Arkansas report. This caps the Little 

 and Red river divide and that of Red and Sulphur river, and is sur- 

 rounded on all sides by the later second bottom valleys of the drainage 

 system. 



The recent and Pleistocene valleys of Red river, or " bottoms " and 

 " second bottoms," as they are called, have widened to great proportions 

 along this section, and their phenomena alone would occu23y many pages 

 of description. They extend from twelve to fifteen miles on each side of 

 the river, and the river itself begins to assume that serpentine meandering 

 which characterizes the retarded drainage of the low Mississippi embay- 

 ment. The baselevel deposits of this region are : (a) Present deposition 

 at times of overflow; ib) ancient or second bottom deposits, occurring 

 about 100 feet and higher above the level of present high water ; (c) 

 swampy lacustral or marsh deposits upon the higher slopes making the 

 prairie at New Boston, Prairie d'Ane, etcetera; (d) the older Plateau 

 gravel constituting the divides. 



Beneath this veil of post-Tertiary estuarine deposits two views of the 

 underlying floor of Upper Cretaceous marine sediments are obtained 

 through erosion. In Little River county, Arkansas, the Austin chalk is 

 exposed at Rocky Comfort — so named because it is probably the only 

 dry spot in that county of overflow and backwater. About fifteen miles 

 southward, in Bowie count}^, Texas, at the Freise place, the Greensand 

 beds of the Glauconitic division are exposed. 



Near the summit of the divide of Sulphur and Red river, close by the 

 old abandoned town of Boston, the typical laminated clays and sands of 

 the Eocene-Tertiary appear beneath the Plateau gravel, which forms the 

 cap, and are exposed from thence southward in the Sulphur river slopes 

 and bottoms. 



ANTOINE SECTION. 



This is in Arkansas, 60 miles east of the Choctaw line. The Trinity 

 valley and sand still follow the mountain foot. The upper limestone or 

 Glen Rose member of the Trinity, which has been missing westward from 

 the Trinity river in Texas, reappears in a small area, but the Fredericks- 

 burg, Washita, Dakota and Austin l)eds have been completely overlapped 

 by later deposits. The Glauconitic outcrops in patches beneath the 

 Eocene overlap, and the Plateau gravel still spreads its mantle over all 

 the uplands except where cut through by the ever increasing second 

 bottoms. The Eocene begins to appear north of Little river from Nash- 

 ville to Arkadelphia, approaching nearer and nearer the ancient moun- 

 tain shore. A few miles east of this section, near Arkadelphia, the Glau- 

 conitic completely overlaps the Trinity and abuts against the upturned 

 mountains. 



