Paleoshorelines in the Upper Cretaceous Point Lookout Sandstone, southern San Juan Basin, New Mexico

Abstract

LANDSAT images and aerial photography reveal several parallel linear features as much as 17 km long and 0.7 km wide. Detailed cross sections normal to a linear feature show it to be an exhumed paleoshoreline containing several overlapping sandstone units. Each unit tends to pinchout into the shales of the overlying Menefee Formation, showing a range of depositional environments including upper shoreface, foreshore, washover and eolian. Paleogeomorphic elements, predominately beach ridges and interridge swales, shape the upper surface of the sandstone and produce a relief *as great as 4.2 m. The various components found in the paleoshoreline create a trellis-like drainage pattern that contrasts with the regional dendritic drainage pattern; the resulting linear feature is easily discernible on aerial photography and LANDSAT images. The rapid lithologic and thickness changes of the sandstone bodies in these linear features provide excellent potential as stratigraphic trap for hydrocarbons. Paleoshoreline facies are likely to be preserved in areas of thickest marginal marine regressive sand accumulation and similar paleoshoreline systems may be preserved at depth in the Point Lookout (Sandstone) or other Cretaceous sandstones.

Heavy-mineral placer deposits of the Ute Mountain Ute Indian Reservation, southwestern Colorado and northwestern New Mexico

“…The presence of monazite was not investigated. The Alien and Balk (1954) study was in an area where the Point Lookout sandstones were wave dominated (Zech, 1982), as is the case on the Ute Mountain Ute Indian Reservation. One difference between the two areas was the presence of a major(?)…”

Subsurface Analysis of the Mesaverde Group on and near the Jicarilla Apache Indian Reservation, New Mexico-its implication on Sites of Oil and Gas Accumulation

“…Straight strandplain coastlines are well preserved near Gallup, New Mexico. (Zech, 1982) as planar laminated, seaward dipping foreshore deposits. North from the Gallup area, foreshore deposits are less well preserved due to removal by later fluvial and tidal channels.…”