. Annual report of the United States Geological Survey to the Secretary of the Interior . -where on the west by a larger fault, which may be called the motherfault, and which at Austin has a downthrow of nearly 500 feet. (SeePI. LIT, B.) It is in reality a number of short faults overlappingen echelon. This mother fault line from the Nueces to the Brazosmakes the dividing line between the Black and Grand prairies. Northof Waco it passes into the unconsolidated clays of the Black Prairie,between Whitney and Aquilla. It is impossible to trace its continuityeast of north from the last-mentioned lo
. Annual report of the United States Geological Survey to the Secretary of the Interior . -where on the west by a larger fault, which may be called the motherfault, and which at Austin has a downthrow of nearly 500 feet. (SeePI. LIT, B.) It is in reality a number of short faults overlappingen echelon. This mother fault line from the Nueces to the Brazosmakes the dividing line between the Black and Grand prairies. Northof Waco it passes into the unconsolidated clays of the Black Prairie,between Whitney and Aquilla. It is impossible to trace its continuityeast of north from the last-mentioned locality. The details of thisfaulting have been worked out minutely only at Austin, as shown inPI. LIT, A. The fault zone is very conspicuous west of George-town, at Belton. and in the vicinity of Waco, where the downthrowhas decreased. At Belton the faults are well shown in the valleys ofNoland and Lampasas rivers, hut the details have not been the vicinity of Waco the fault zone is of considerable width and U. S. GEOLOGICAL SURVEY TWENTY-FIRST ANNUAL REPORT PART VII PL. Llll. SECTIONS OF THE CRETACEOUS FORMATIONS IN THE EDWARDS PLATEAU. A, Section of Castle Mountain near Pecos River, w ;st edge of Llano Estacado ; B. section of east edge of Edwards Plateau, 15miles west of San Angelo ; C, section of Church Mountain, Runnels County. HILL.] DISPLACEMENT OF STRATA. 883 may be seen in the Austin chalk. West of the city, at the very edgeof the chalk outcrop, a fault runs due north and south and is evidentlyof considerable extent. This is the only fault in the vicinity which hasbeen distinctly noted. The presence of many others is indicated bydislocation and joints filled with calcite veins and by numerous slightcrumplings and breaks. The presence of these small faults is also proved by the borings forartesian waters. The data from this source, owing to the nature ofthe rocks, is not as j-et complete, but sufficient has been obtained toshow a considerable downthrow on the e
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