Gibson coal member of Mesaverde formation. Light-gray to white lenticular sandstone, light-gray clay shale, and valuable coal beds throughout Gallup-Zuni basin. Thickness 150 to 175 feet. Underlies Allison barren member and overlies Bartlett barren member; all belonging to Mesaverde formation. Age is Late Cretaceous.
Named from village of Gibson, McKinley Co., Gallup-Zuni basin, northwestern NM, for many years the center of mining operations in the coals of this member.

Source: US geologic names lexicon (USGS Bull. 896, p. 817).

Gibson coal member of Upper Cretaceous Mesaverde formation reassigned to two formations in McKinley Co., NM in San Juan basin; lower part beneath Hosta tongue of Point Lookout sandstone reassigned as upper member of Crevasse Canyon formation (a new name) of Mesaverde group. As thus mapped the "lower coal Gibson member" is a gray papery shale, carbonaceous shale and coal, shaly siltstone, thin-bedded sandy siltstone and silty sandstone. Ranges from 135 to 345 ft thick in northern part of area to about 550 ft thick on Catron Creek to the south. Coal beds increase in thickness and in occurrence from north to south. What was called upper Gibson coal member reassigned to Menefee formation in Tohatchi quad, San Juan basin.

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

Gibson coal member of Mesaverde formation reassigned as the upper member of Crevasse Canyon formation of Mesaverde group of Late Cretaceous age and stratigraphically restricted in this paper to what was originally lower part of Gibson. Lower part is near the town of Gibson and is the part of Gibson from which much of the coal was mined. Term Mesaverde group extended throughout San Juan basin of southwest CO and northwest NM. The restricted Gibson overlies Bartlett barren member of Crevasse Canyon formation near Gallup and underlies Point Lookout sandstone to the east. Beds formerly included in upper part of Gibson reassigned to Cleary coal member (new) of Menefee formation. Small geologic map. Diagrammatic cross section. Of Late Cretaceous age.

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

Study of palynomorphs from samples of coals and shales of the Upper Cretaceous Crevasse Canyon Formation indicate a biostratigraphic age assignment of Coniacian and Santonian for the formation. Crevasse Canyon Formation, in the Hosta Butte area, McKinley Co, NM (San Juan basin), overlies Gallup Sandstone (Turonian) and is overlain by Hosta Tongue of the Point Lookout Sandstone (Santonian). Crevasse Canyon is separated into lower and upper parts by the Mulatto Tongue (Coniacian) of the Mancos Shale; lower part comprised of Dilco Coal Member (Coniacian) and upper part comprised of Dalton Sandstone Member (Coniacian) and Gibson Coal Member (Santonian). Turonian/Coniacian Stage boundary is queried at the Gallup/Dilco contact at base of Crevasse Canyon Formation. Coniacian/Santonian Stage boundary is queried at the Dalton/Gibson contact within the upper part of the Crevasse Canyon. Samples were examined from the Dilco and Gibson Members, but not the Dalton Member. Crevasse Canyon is tentatively divided into 3 pollen zones spanning the Coniacian and Santonian. The stage assignments are derived from invertebrate zone fossils found in the associated marine rocks. The Mulatto Tongue yields lower Coniacian INOCERAMUS DEFORMIS near Tohatchi. The Hosta Tongue of the Point Lookout Sandstone yields the middle Santonian ammonite CLIOSCAPHITES VERMIFORMIS. The Gibson Coal Member lies directly below the Hosta Tongue, consequently all the Gibson in the area is probably of Santonian age.

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

About 25 mi northeast of Gallup, NM near Coal Mine Canyon, Hosta Tongue of Point Lookout pinches out. South of that locality, Gibson Coal Member of Crevasse Canyon Formation and Cleary Coal Member of Menefee Formation cannot be separated. [The stratigraphic restriction by Beaumont and others, 1956 of Gibson to only the lower part of what Sears in 1925 assigned to Gibson, and application of the name Cleary by Beaumont and others to the upper part of what Sears assigned to Gibson has set up a formation contact (Crevasse Canyon-Menefee) that cannot be mapped according to these authors.] Assigned to the Late Cretaceous.

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