Designated Ford siltstone (informal, unranked) within the upper part of the Bell Canyon formation of the Delaware Mountain group. Occurs in subsurface of the northern Delaware basin [in Permian basin], in northwest Reeves, Loving, and northeast Culberson Counties, Texas, and in southern Eddy and Lea Counties, New Mexico. Is a non-reservoir unit of interbedded, calcareous, tight sand [sandstone] and silty interval [siltstone] approximately 10 to 15 feet thick. Is traceable throughout much of the northern Delaware basin. Underlies Ramsey sand (new, informal); where Ramsey is absent, may underlie Trap subdivision (new, informal). Overlies Olds sand (new, informal). Age is Permian (Guadalupian). Report includes generalized structure contour map.
Type gamma ray-sonic log presented but not located. Possibly named from Geraldine-Ford field, in northeast Culberson Co., and northwest Reeves Co., TX.

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

Redescribed from Ford siltstone (unranked, informal) to Ford shale member (informal). Is part of the upper Bell Canyon Formation of the Delaware Mountain Group, in Delaware basin area [in Permian basin], southwest Texas and southeast New Mexico. Consists of a laminated shaly siltstone that is 6 feet thick, with black shale beds, each 2 feet thick, above and below the siltstone. Recognized as a widespread marker unit below the Ramsey sandstone member (informal) in the upper part of the Bell Canyon Formation. Overlies Olds sandstone member (informal) and underlies Ramsey member (informal) throughout central and western portions of the Delaware basin. Age is Permian (Guadalupian). Report includes stratigraphic chart and subsurface log correlations.

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

Pg. 7-10. The Ford Member of the Bell Canyon Formation of the Delaware Mountain Group. The Ford Member, here [formally] named, is in the upper Bell Canyon Formation of the Delaware Mountain Group in the central Delaware basin of Texas and New Mexico. Was previously designated the informal unranked Ford siltstone by Nottingham (1960) and the Ford shale member by Grauten (1965). Consists of silty, calcareous shale that has relatively tight porosity and is defined as the first significant shaley zone above the base of the Olds Member [new, formal] of the Bell Canyon. Is regionally extensive but is difficult to correlate on a regional basis, especially where the overlying informal R3 sand of the Ramsey Member [new, formal] of the Bell Canyon is tightly cemented. Thickness is about 10 feet. Age is Permian (Guadalupian).
Type section (subsurface): Gulf J.R. Grandin No. 1 well, sonic-gamma ray log, SE/4 sec. 33, Blk. 29 PSL Survey, Loving Co., TX. [Possibly named from Geraldine-Ford field, in northeast Culberson Co., and northwest Reeves Co., TX.]

Source: US geologic names lexicon (USGS Bull. 1565, p. 111).