RI0020. Cretaceous of Llano Estacado of Texas, by J. P. Brand. 59 p., 14 figs., 4 plates, 1953. Print.
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Rocks of Cretaceous age crop out along the western margins of the deeper playa basins and along the southern and southeastern margins of the Llano Estacado. The Trinity group, containing only the Paluxy sandstone; the Fredericksburg group, consisting of the Walnut, Comanche Peak, Edwards, and Kiamichi formations; and the Washita group, containing only a portion of the Duck Creek formation, have been identified in the Llano Estacado. Formations of the Trinity and Fredericksburg groups are similar lithologically and paleontologically to equivalent units in the Callahan Divide and in the northern edge of the Edwards Plateau. Zonations, applicable to northern and central Texas and Pecos County, Texas, can be extended to the isolated Cretaceous exposures in the Llano Estacado.
Cretaceous strata in the Llano Estacado dip to the southeast at the rate of 7 to 8 feet per mile. Structures in the underlying Triassic and Paleozoic do not appear to be reflected in Cretaceous strata. Likewise, the locations of the isolated Cretaceous remnants do not appear to be governed by known structures in underlying units.
The Comanche Peak and Edwards limestone and the Kiamichi and Duck Creek shales are chemically suitable for the manufacture of Portland cement. The Edwards limestone is a suitable road ballast material. The sand and gravel of the Paluxy formation could be utilized in concrete aggregate.
Keywords: Llano Estacado, Cretaceous, West Texas, Trinity Group, Paluxy sandstone, Fredericksburg Group, Callahan Divide, Comanche Peak limestone, Kiamichi shale, Duck Creek Shale, fauna, paleontology, zonation
Comanche Peak limestone
Duck Creek shale
Paleontology and zonation
Correlation of Kiamichi and Duck Creek exposures in Llano Estacado
Cretaceous exposures in adjacent areas
Quay County, New Mexico
Dallam County, Texas
Conditions of deposition of Cretaceous sediments
Subsurface and structural geology
Sand and gravel
Localities and measured sections
1. Columnar section of Cretaceous of Llano
2. Correlation of Kiamichi and Duck Creek exposures in Llano Estacado
3. Subsurface distribution of Cretaceous beds in Llano Estacado
4. Contours showing elevation of Gryphaea navia zone of Kiamichi shale
5. Map of portion of Llano Estacado showing location of sections described in text
6. Cretaceous exposures at Guthrie Lake, Lynn County, Texas
7. Cretaceous exposures at Twin Lakes, Lynn County Texas
8. Cretaceous exposures at Double Lakes, Lynn County, Texas
9. Cretaceous exposures at Tahoka Lake, Lynn County, Texas
10. Cretaceous exposures at Mound Lake, Terry and Lynn counties, Texas
11. Cretaceous exposures at Bull Lake, Lamb County, Texas
12. Cretaceous exposures at Muleshoe National Wildlife Refuge, Bailey County, Texas
13. Cretaceous exposures at Monument Lake, Bailey County, Texas
14. Cretaceous exposures at Baileyboro Lake, Bailey County, Texas
I. Map of portion of eastern Lynn County and western Garza County, Texas, showing locations of Cretaceous exposures along South Double Mountain Fork of Brazos River (in pocket of book)
A. Disconformity at contact between Paluxy sandstone and Walnut formation in cut along Eppler-Fluvanna road
B. Comanche Peak and Edwards limestones in cut along Eppler-Fluvanna road
A. Comanche Peak-Edwards contact in cut on road al1mg west side of Gail Mountain
B. Porous strata in Edwards limestone near top of road cut on west side of Gail Mountain
A. Conglomeratic limestone in Gryphaea navia zone of Kiamichi shale at locality 32
B. Kiamichi shale at mid-western margin of present playa of Guthrie Lake
A. Kiamichi-Duck Creek contact at northwest Twin Lake
B. Duck Creek shale at Mound Lake
1. Stratigraphy of Llano Estacado area
2. Zonation of Cretaceous of Llano Estacado
3. Cement materials in Llano Estacado area
4. Analyses of Cretaceous rocks
Brand, J. P., 1953, Cretaceous of Llano Estacado of Texas: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations No. 20, 59 p.