Abstract

A newly described reef in the upper Tansill Formation (Paraboultonia splendens fusulinid zone) at the mouth of Sheep Draw Canyon in the Carlsbad Embayment is the northernmost occurrence of reef facies in the Guadalupe Mountains. It is also the youngest Guadalupian reef found in this area. The core of this patch reef is of typical “Capitan-like” aspect in that it consists of calcisponge-Archaeolithoporella-Tubiphytes boundstones cemented syndepositionally by marine aragonite. Succeeding Parachaetetes boundstones, overlain in turn by algal grainstones, represent shallow-water/ reef climax stage and reef crestal deposits respectively.

The Carlsbad Embayment, that area north of Dark Canyon, appears to have been a shallow-water platform in middle and upper Tansill time. Facies here are characterized by numerous patch reefs, islands, and high-energy grainstones. Tansill facies architecture in this region departs from typical upper Tansill strata elsewhere in the Guadalupe Mountains.