. Annual report of the United States Geological Survey to the Secretary of the Interior . that portionbeneath the western border of the Grand Prairie, along the Colorado-Brazos divide, the age of the Glen Rose beds; that portion beneaththe Callahan Divide of the Central Province, the age of the Paluxysands; and that portion in southern Indian Territory (top of Antlerssands), southern Kansas (Cheyenne sands), and northeast New Mexicoat Tucumcari Mesa, the age of the Fredericksburg and Washita sub-epochs. In the beginning of Cretaceous time the shore line reached the east- 134 BLACK AND GRAND PR
. Annual report of the United States Geological Survey to the Secretary of the Interior . that portionbeneath the western border of the Grand Prairie, along the Colorado-Brazos divide, the age of the Glen Rose beds; that portion beneaththe Callahan Divide of the Central Province, the age of the Paluxysands; and that portion in southern Indian Territory (top of Antlerssands), southern Kansas (Cheyenne sands), and northeast New Mexicoat Tucumcari Mesa, the age of the Fredericksburg and Washita sub-epochs. In the beginning of Cretaceous time the shore line reached the east- 134 BLACK AND GRAND PRAIRIES, TEXAS. ern margin of the Black Prairie, and during the Trinity epoch the seawent westward as far as the present western border of the Grand Prairie. An interesting illustration of the conquest of the old topographicirregularities of the Paleozoic floor by the Lower Cretaceous seas andthe diagonal transgression of the Basement sands can be seen by trac-ing the relations of the formations between Colorado River near the POST TRAVIS PEAK. i i Ml? . 1 1 v,v«; l_i I 1 I. Fig Basement sands between Travis Peak and Post Mountain, Burnet (For explanation of symbols see PI. XVI. p. 110.) mouth of Sycamore Creek, in the southwest corner of Burnet County,and Post Mountain just west of Burnet (see fig. 9). some 15 miles westof north, along the foot of the escarpment of the Lampasas Edwards limestone at the summit of this escarpment and of PostMountain makes a subhorizontal datum plane, while the changingthickness of the rocks of the Trinity division in the slopes and thegradient of the old Paleozoic floor below are variables from the hori-zontal. HILL.] HICKORY CREEK SECTION. 135 SECTIONS (IF THE BASEMENT SANDS. The most western outcrop of the Basement sands of the Trinitydivision in the Colorado Valle}r occurs just in the east bluffs of Syca-more Creek, TO feet above its bed, at an altitude of about 750 the beds of th
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