Montoya Dolomite (TXOm;0)

State	Texas
Name	Montoya Dolomite
Geologic age	Middle and Late Ordovician
Lithologic constituents	Major Sedimentary > Carbonate > Limestone (Bed)thin sandstone bed locally present at base Sedimentary > Carbonate > Dolostone (Bed)
Comments	(described fr. Van Horn--El Paso Sheet of Geologic Atlas of Texas, 1968) Dolomite, limestone, and sandstone. Upper part--dolomite and ls., aphanitic to medium grained, thin to thick bedded, white to dk dray, cherty. Lower part--limestone and dolomite, aphanitic to v. coarse grained, light to medium gray, local motled zones near base, chert scarce to absent, thin sandstone bed locally at base. Thickness--Franklin Mountains, 250-430 ft; Hueco Mtns 320+- ft; Sierra Diablo, 250-500 ft. Southeastern Baylor Mtns; includes Middle Ordovician Simpson Group rocks not separately mapped. Stratig. divisions used in Orogrande Basin, NM described in Kelley and Silver (1952)
Stratigraphic units	Cutter Member (at top), Aleman Chert Member, Upham Member, and Cable Canyon Sandstone Member (basal member) (not shown on Texas State map)
References	Bureau of Economic Geology, 1968, Van Horn-El Paso Sheet, Geologic Atlas of Texas: Bureau of Economic Geology, The University of Texas at Austin, scale 1:250,000. Udden, J.A., Baker, C.L., and Boise, E., 1916, Texas Univ. Bur. Econ. Geology and Tech. Bull. 44 p. 39. Kelley V.C., and Silver, C., 1952, Geology of the Caballo Mountains: Univ. of New Mexico Publications in Geology, no. 4, University of New Mexico Press. Bureau of Economic Geology, 1992, Geologic Map of Texas: University of Texas at Austin, Virgil E. Barnes, project supervisor, Hartmann, B.M. and Scranton, D.F., cartography, scale 1:500,000. Bureau of Economic Geology, 1992, Geologic Map of Texas: University of Texas at Austin, Virgil E. Barnes, project supervisor, Hartmann, B.M. and Scranton, D.F., cartography, scale 1:500,000.
NGMDB product	NGMDB product page for 68390
Counties	Culberson - El Paso - Hudspeth

State

Texas

Name

Montoya Dolomite

Geologic age

Middle and Late Ordovician

Lithologic constituents

Major

Sedimentary > Carbonate > Limestone (Bed)thin sandstone bed locally present at base

Sedimentary > Carbonate > Dolostone (Bed)

Comments

(described fr. Van Horn--El Paso Sheet of Geologic Atlas of Texas, 1968) Dolomite, limestone, and sandstone. Upper part--dolomite and ls., aphanitic to medium grained, thin to thick bedded, white to dk dray, cherty. Lower part--limestone and dolomite, aphanitic to v. coarse grained, light to medium gray, local motled zones near base, chert scarce to absent, thin sandstone bed locally at base. Thickness--Franklin Mountains, 250-430 ft; Hueco Mtns 320+- ft; Sierra Diablo, 250-500 ft. Southeastern Baylor Mtns; includes Middle Ordovician Simpson Group rocks not separately mapped. Stratig. divisions used in Orogrande Basin, NM described in Kelley and Silver (1952)

Stratigraphic units

Cutter Member (at top), Aleman Chert Member, Upham Member, and Cable Canyon Sandstone Member (basal member) (not shown on Texas State map)

References

Bureau of Economic Geology, 1968, Van Horn-El Paso Sheet, Geologic Atlas of Texas: Bureau of Economic Geology, The University of Texas at Austin, scale 1:250,000.

Udden, J.A., Baker, C.L., and Boise, E., 1916, Texas Univ. Bur. Econ. Geology and Tech. Bull. 44 p. 39.

Kelley V.C., and Silver, C., 1952, Geology of the Caballo Mountains: Univ. of New Mexico Publications in Geology, no. 4, University of New Mexico Press.

Bureau of Economic Geology, 1992, Geologic Map of Texas: University of Texas at Austin, Virgil E. Barnes, project supervisor, Hartmann, B.M. and Scranton, D.F., cartography, scale 1:500,000.

NGMDB product

NGMDB product page for 68390

Counties

Culberson - El Paso - Hudspeth