Lower Devonian Reef and Associated Facies in Tor Limestone, Toquima Range, Central Nevada

Michael E. Anderson, Michael A. Murphy

The Tor Limestone at its type section in the Toquima Range, central Nevada, is an organically bound algal-coral-stromatoporoid reef as revealed by outcrop and thin-section study of the basal 200 ft. Light-colored coarse-grained massive grainstone-bindstone-framestone deposits of the reef mound are preserved in June Canyon, where laminated hemispherical algal heads form the bulk of the rocks; Renalcis and Stringocephalus are other reef-dwellers present.

One-half mile north, in Ikes Canyon, the off-reef facies is developed as darker colored thin to thick-bedded packstones and grainstones. The thinner beds are often graded and are interpreted as turbidity current deposits. Thicker beds with randomly oriented clasts are interpreted as debris-flow deposits. Both turbidity current and debris-flow deposits were shed eastward into the Roberts Mountains depositional basin.

Conodonts of the delta and sulcatus zones have been recovered from the type section in June Canyon, indicating that the lower part of the Tor is Early Devonian (high Lochkovian to low Pragian).

AAPG Search and Discovery Article #91024©1989 AAPG Pacific Section, May 10-12, 1989, Palm Springs, California.