Seismic Signature of Serpentine Plugs in the Maverick Basin

James O. Lewis

Basalt necks occur on the surface in Uvalde and Kinney Counties in southwest Texas. These basalt necks are the "serpentine plugs" that produce from the Upper Cretaceous Taylor section in the subsurface of Zavala County. Many plugs exist in both the surface and subsurface.

Geology of the "serpentine plugs" indicates that most of the volcanic activity occurred as Upper Cretaceous post-Austin subaqueous extrusions. Formations below the volcanic material show no structural deformation. Formations above the Cretaceous seldom show evidence of the pile of volcanic material. The most significant evidence of structure and faulting is within the Taylor section.

The applicatio2n of two dimensional forward lithological modeling using inverse velocity calculations is successful in producing a velocity model to display stratigraphic development. The use of an interactive computer system is an important step in the interpretive process.

Seismic techniques used to evaluate the stratigraphy of the "serpentine plugs" is readily adapted to solving other exploration problems with stratigraphic implications.

AAPG Search and Discovery Article #91028©1989 AAPG History of Petroleum Industry Symposium, September 17-20, 1989, Titusville, Pennsylvania.