was a Captain in the Texas Army during the War for Independence. There is little contemporaneous evidence to support either derivation of the name. Legend has it that Mount Bonnell was once called Antoinette's Leap, after a young woman who leaped to her death to avoid being captured by Native Americans who had killed her fiancé. Geology Mt. Bonnell forms part of the Balcones Fault Escarpment and these "balconies" were first described by Bernardo de Miranda in 1756. The lower Cretaceous Glen Rose Formation limestone outcrops to the west of the fault zone but is buried 1000 feet to the east. A stratigraphic column starts with the Lower Cretaceous Trinity Group overlain by the Edwards Group and the Georgetown Formation. Upper Cretaceous formations follow, starting with the Del Rio Clay, Buda Limestone, and then the Eagle Ford Group. Formations within the Trinity Group include the Hammett Formation, Cow Creek Formation, Hensel Formation, and Lower and Upper Glen Rose Formation. The Hammett and the lower portion of the Upper Glen Rose act as confining units (or aquitard) for the Middle Trinity Aquifer. The Upper Glen Rose contains the Upper Trinity Aquifer, which appears to have intra-aquifer groundwater flow with the Edwards Aquifer as water levels are at the same elevation. Formations within the Edwards Group include the Kainier Formation and the Person Formation. The Upper Cretaceous rock units confine the Edwards Aquifer within the group. The Mount Bonnell fault has a vertical throw of up to 600 feet, making it the most prominent normal fault within the Balcones Fault Zone. During the Miocene, the Edwards Group was displaced downwards relative to the Glen Rose Formation on the Edwards Plateau, so that they are juxtaposed. Gallery See also Balcones Canyonlands National Wildlife Refuge Barton Creek Texas Hill Country National Register of Historic Places listings in Travis County, Texas References External links Early 20th century photographic postcards of Texas places at the University of Houston Digital Library Mount Bonnell Local Community-Run Website Hills of Texas Mount Bonnell Mount Bonnell Geography of Austin, Texas Mount Bonnell Mount Bonnell City of Austin Historic Landmarks Landforms of Travis County, Texas National Register of Historic Places in Texas National Park Service rustic in Texas