the start of Middle Cambrian sedimentation, erosion removed several kilometers of Precambrian rock. Lower Paleozoic (Cambrian and Ordovician) Within and around the Llano uplift are erosional remnants and down-faulted blocks of Lower Paleozoic sedimentary strata. Within the Llano Uplift, these remnants and fault blocks often form prominent hills. The Lower Paleozoic strata are composed of over of Cambrian sandstones, limestones, and dolomites of the Moore Hollow Group and Lower Ordovician limestone and dolomite of the Ellenburger Group. The Moore Hollow Group which consists of the Hickory sandstone, Cap Mountain limestone, and Lion Mountain sandstone, and the Wilberns Formation, which consists of sandstone, limestone, shale, and an upper mixture of limestone and dolomite. The Ellenburger Group is an incomplete sequence of Lower Ordovician strata, which are divided, from the base up, into the Tanyard, Gorman, and Honeycut formations. These formations contain limestones and dolomites, which are typically nonglauconitic and sparingly fossiliferous. An erosional, pre-Devonian paleosurface with well-developed paleokarst truncates the Ellenberger Group such that it thins from a thickness of in the southeastern corner of the Llano region to only in the northwestern corner of the region. The Moore Hollow Group records the advancing of a sea from the southeast across eroded Precambrian rocks during Middle to Late Cambrian times and subsequent burial beneath coastal and nearshore marine sediments. The Cambrian sea spread northward across the eroded surface an area of Precambrian rocks that had a local relief as great as . As a result, sediments composed of locally derived residuum, often wind-abraded accumulated as a thin, discontinuous cobble conglomerate overlying Precambrian strata at the base of the Moore Hollow Group. Following the deposition of the uppermost Cambrian limestones and dolomites, the Lower Ordovician Ellenburger Group (composed of the Tanyard, Gorman, and Honeycut Formations) accumulated within shallow-water carbonate platforms. At the end of the Lower Ordovician, the Central Texas region was tilted eastwards and exposed to subaerial erosion and karstification. Possible reworked Middle Ordovician conodonts (Chirognathus) have been found in younger strata and a pocket of Upper Ordovician limestone, the Burnam Limestone, is preserved in a collapse structure in Burnet County. The reworked conodonts and the Burnam Limestone indicate that the region of the Llano Uplift was likely either partially and briefly submerged during the Middle and Upper Ordovician only to have the sediments deposited during these inundations removed by later erosion. Middle Paleozoic (Silurian and Devonian) Within the Llano Uplift,