Precambrian geology of part of the Little Llano River Valley, Llano and San Saba Counties, Texas

[摘要] This study was conducted for the purpose of contributing to the knowledge of the Precambrian history of the Llano Region in central Texas. Relatively little detailed information is available on the metamorphic rocks of the Llano uplift, and consequently it is believed that a detailed study of some of these rocks is of value. The Packsaddle schist in a part of the Little Llano River valley was chosen for study because its character, as compared to that of the Valley Spring gneiss, should be particularly instructive in helping to solve the evolution of these metamorphosed rocks. Generally, the Packsaddle schist in the Llano uplift is poorly exposed, occurring in areas of low relief and poor drainage. The Little Llano River valley, however, has outcrop relief of approximately 350 feet and relatively good drainage, so that a large portion of the outcrop surface is exposed and adequate observation and sampling are possible. This study has produced information on: (1) the structural effects of small, relatively incompetent bodies during deformation; (2) possible continuation of stress after the main deformation; and (3) structural control in the emplacement of magma.

[发布机构] Rice University