Abstract

Ingrown meanders incised into a limestone plateau on four streams in the western half of Mason County are described.

The meanders of Bluff Creek and its West Branch are notably angular, and appear to have developed from round meanders under the influence of two sets of vertical minor faults and joints. Faults of larger displacement do not affect the stream's course. A small unnamed creek west of Bluff Creek shows well-developed ingrown meanders where it crosses a folded structure, but not where it flows parallel to the strike.

Various authors have challenged the classical concept that incised meanders are inherited from free meanders developed on a flood plain, but there is as yet no satisfactory explanation of how meanders can be initiated in hard rock. Other evidence suggests uplift and rejuvenation for the Central Texas region. Although it seems difficult to assign such a long history to such a small stream as the unnamed creek described, the presence of a meander core suggests a considerable age.

Large incised meanders occurring on Bluff Creek and on the James River just above their confluences with the Llano River, which does not meander, are difficult to explain. Backwater in the early history of these tributaries is suggested as a possible cause.

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