Abstract

Permian rocks of the Santa Fe-Las Vegas area, New Mexico, exhibit many shoreline characteristics, a single cycle onlap-offlap sequence. Ripple marks, cross-bedding, bars and channels, fossils, beachrock, facies changes, gypsum, supposed halite prints, mud cracks, trails, pebble sizes, and rock thicknesses are used to interpret this pattern. The shoreline was oriented roughly N.-S., or NE.-SW. Local hills or small mountains, and a wide coastal plain, were on the W. and NW. The sea extended toward the E. and SE. In early Permian time, the sea was advancing; in middle Permian time, retreating. The onlap-offlap cycle produced a wedge-shape body of marine Permian sediments which feathered out along a line W. of the present Rio Grande. The Sangre de Cristo Formation (of upper Pennsylvanian and lower Permian age) is dominantly maroon shale, with about 20% sandstone and conglomerate, representing continental deposition. The Yeso Formation is primarily orange-colored ripple-marked siltstones representing the tidal flat environment, but the upper part of the formation includes several beachrock units. The Glorieta Formation is highly cross-bedded clean sand which apparently accumulated in the near-shore environment. The Lagunita Formation is beachrock, formed early in the regressive stage. The Bernal Formation is orange-colored stone thought to represent the tidal flat, and supposedly deposited in middle Permian time. No late Permian rocks are known in the area. Coastal plain sediments accumulated again during the Triassic (Santa Rosa and Chinle formations). Ripple marks, cross-bedding, bars, and facies changes are used to give orientations. Ripple marks, cracks, trails, and evaporites are used to provide information about water depths. Ripple marks, beachrock, and fossils are used to interpret specific environments. A tropical or sub-tropical climate is inferred.

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