Geology of the Mozo quadrangle, Williamson County, Texas

The Austin chalk consists of seven faunal zones in northeasternWilliamson County, Texas: the Inoceramus subquadratus zone, "Gryphaea wratheri zone," Inoceramus undulatoplicatus zone, Hemiaster texanus zone, "Qstrea travisana zone, Gryphaea sucella zone, and the Exogyra laeviuscula zone in ascending order. The Austin chalk nay be divided into three lithologic sequences: a lower, fine grained clastic, a middle coarse grained clastic, and an upper fine grained sequence. The Austin chalk is estimated to be 350 feet thick; 255 feet of beds are described in detail. The faulting in the quadrangle is normal, high angle. Many faults dip west, and are upthrown on the east In contrast to faults in the area to the south, where most of the faults dip east and are dovnthrovn on the east.