A thick-bedded, buff marine sandstone 300 to 360 ft thick at the top of the Upper Cretaceous Mesaverde formation named Chacra sandstone member for occurrences on Chacra Mesa, northeast McKinley Co, NM (no type locality designated), San Juan basin. Overlies Allison member of Mesaverde and underlies Lewis shale. The sandstone may be gray, white, and copper-colored, cross-bedded, and ledge-forming. Intervening gray shale and shaly sandstone, brown, thin-bedded shales with plant material, and black carbonaceous shale and sub-bituminous coal also present. Thins east probably by merging into Lewis shale. Has casts of HALYMENITES MAJOR LESQUEREUX and shells of invertebrates indicating a Late Cretaceous age and marine environment. Replaces name Cliff House sandstone as used by Reeside in this area.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Sandstones that were included in Upper Cretaceous Chacra sandstone member of Mesaverde formation are equivalent to two upper southward-extending sandstone tongues of marine Cliff House sandstone northeast of Newcomb in southwest San Juan Co in San Juan basin. Name Cliff House sandstone therefore replaces Chacra sandstone member throughout its extent. [Name Chacra abandoned? as a rock-stratigraphic unit.] Simplified geologic map. Diagrammatic cross section.

Source: GNU records (USGS DDS-6; Denver GNULEX).