Volcanic rocks exposed on the northern end of Burro Mesa in Big Bend National Park portray the evolution of an Oligocene central volcanic vent complex that produced two generations of welded block and ash deposits associated with 1) initial dome collapse and 2) subsequent central spine collapse. Peripheral to the vent complex, isolated breccia deposit exposures overlie ignimbrites, tephras, and lavas. These blocks are a few meters to several hundred meters long and 30 m high and consist of monolithic angular and welded trachytic lava clasts in finer-grained matrix. Rheomorphic structures in the breccia deposit show ductile deformation and suggest it formed while above the glass transition temperature.
Additional publication details
Volcanic and magmatic evolution of a small trachytic vent complex, north Burro Mesa, Big Bend National Park, Texas
Abstracts with Programs
Geological Society of America
Central Mineral and Environmental Resources Science Center