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Trinity Group

Trinity Group
State Arkansas
Name Trinity Group
Geologic age Phanerozoic | Mesozoic | Cretaceous-Early
Comments Alternating fine qtz. sand and gypsiferous marls with lenticular fossiliferous limestone, gypsum and minor novaculite gravel. Approximately 2500 ft. thick. Novaculite-similar to chert but characterized by dominance of microcrystalline quartz over chalcedony.
Primary rock type sand
Secondary rock type mixed clastic/carbonate
Other rock types limestone; gypsum; novaculite
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Carbonate > Marlstone (Bed)
Minor
Sedimentary > Carbonate > Limestone (Lense)
Sedimentary > Chemical > Evaporite > Gypsum (Lense)
Sedimentary > Chemical > Novaculite (Bed)
Map references
Haley, B. R., Glick, E. E., Bush, W. V.; Clardy, B. F.; Stone, C. G.; Woodward, M. B., Zachry, D.L., 1993, Geologic Map of Arkansas: U.S.Geological Survey Special Geologic Map. Scale 1:500K
Unit references
Dane,C. H.,1929, Upper Cretaceous formations of southwestern Arkansas: Arkansas Geol. Survey Bull.1, 215 pp.
Counties Howard - Pike - Sevier