ABSTRACT: THE PRECAMBRIAN - IMPORTANT FOR PERMIAN BASIN OIL AND GAS?

ERDLAC, RICHARD J., JR.

Precambrian terranes have important affects on later basin tectonics, stratigraphy, and local heat flow which in turn affects hydrocarbon maturation temperatures.

The Abilene Minimum (Grenville Front) in Texas is a thickened tectonic suture separating regions of strongly differing magnetic signature. Large igneous intrusions north of this boundary give way to basement folds and faults farther south, as defined by lower amplitude magnetic anomalies.

In northcentral Texas, the minimum affects deposition of Palo Pinto and Winchell limestone banks, and the Perrin Delta system. Westward, ancient intrusions have created a long-lived structural doming which later provided a topographically higher region for the Horseshoe Atoll to develop. The minimum extends through a saddle in the Central Basin Platform, causing a 10-15 mile rightlateral separation of the Platform along a cataclastic zone. This offset is reflected in the zero-foot porosity line of San Andres production, in distinctive drainage changes of Monument Draw, and in a subtle topographic low where sand dunes extend east along the axis of the minimum.

Precambrian complexity also underlies the Palo Duro Basin. Interbasement reflections of possible sedimentary nature and deep tectonic activity are found on seismic. The basin-like character of the Precambrian is supported by a large low density gravity anomaly. The possibility of sedimentary Precambrian rock is unknown, however petroleum production has been established from Precambrian strata in other parts of the world.

Precambrian basement studies are not just an academic exercise. Understanding the Precambrian complex in any basin may be a key in reaming how petroleum later developed.

AAPG Search and Discovery Article #90947©1997 AAPG Southwest Section Meeting, San Angelo, Texas