Structural geology of carboniferous rocks near Marble Falls, Burnet County, Texas




Warner, Ralph Hartwin, 1932-

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Carboniferous rocks assigned to the Houy, Chappel, Barnett, Marble Falls, and Smithwick formations crop out near Marble Falls, Texas. Numerous northeast-trending normal faults that cut the Paleozoic and Precambrian rocks are covered by Cretaceous deposits. Faulting in the area began about the time that the Smithwick formation was being deposited and was initiated by the Llano uplift to the west. Folded and steeply-dipping sandstone beds in the Smithwick formation are located adjacent to faults, usually on the downthrown side. The folds are overturned to the east and have originated from sliding of sand and clay off rising fault scarps. Soft sediment deformation of the Smithwick formation was proved by study of microfaults and conglomerates containing fractured pebbles with sandstone dikes. Folded sandstone beds within the area originated during the time that normal faulting occurred. One period of tensional deformation, directly related to the Llano uplift, is responsible for the major structural features in the area