TX 79830 Investigation of possible evidence of sea level fluctuations in the limestones of the Del Carmen Mountains. Project was never begun and was abandoned. None 1996 Petrology of the Alamo Creek Basalt, Big Bend National Park. To decipher and characterize the petrology and stratigraphy of the multiflow lava unit mapped as the Alamo Creek Basalt. Mapping and chemical analyses have been completed.
Mapping indicates at least seven distinct flow units and two possible subunits.
All but one of the flow units are alkaline olivine basalts with similar petrology, though each unit has distinctive textural characteristics. One unit is unique in that it is a hybrid rock containing abundant plagioclase xenocrysts and being closer to trachybasalt in composition. Location of major accumulations and direction of thinning suggest two areas of origin in Mexico, south and west of the Rio Grande. It was hoped that chemical analyses would confirm the suggestion of two separate locii of origin. However, preliminary examination of chemical results does not reveal clearly different groups, either in major, trace of REE compositions.