Early Permian Coated Grains from a Lagoonal Environment, Laborcita Formation, Sacramento Mountains, Southcentral New Mexico, U.S.A.

Abstract

The Sacramento Mountains of southcentral New Mexico (Fig. 1) outcrop at the eastern edge of the basin-and-range province, and are a fault-block range. The mountains are aligned in an approximate north-south direction, are tilted about one degree to the east, and on the west, are bounded by a gravity fault zone situated close to the present escarpment (Pray 1961). It has been estimated that the minimum displacement along the western escarpment for a distance of 29 km is on the order of 2330 m, but this decreases to about half this amount towards the northern end of the range where the Early Permian section is exposed. Most of the salient structural features were formed by major tectonic movements during latest Upper Carboniferous and Early Permian time, with only relatively little structural complication to the Permian sequence. The major uplift of the Sacramento Mountains fault-block is believed to have occurred in late Tertiary time. Significantly, Pray (1961, p. 5) reports that fault scarps seen in Recent alluvium suggest that the uplift of the mountains is still continuing.