Navarro Group and Marlbrook Marl, undivided (TXKnb;0)

State	Texas
Name	Navarro Group and Marlbrook Marl, undivided
Geologic age	Phanerozoic \| Mesozoic \| Cretaceous-Late [Gulfian]
Original map label	Knb
Comments	Clay, calcareous, variable amount of silt and glauconite, limestone bed in so. Collin Co. 10-13 inches thick, aphanitic, lt. gray, forms scarp 180 ft above base; light yell-gray, marine megafossils, thickness 300 +- ft. Upper 250 ft, mostly silty, calcar. clay with sandst beds and concretionary masses near top, some interbeds of sandst. near base. Lower 200+- ft, quartz sand, fine grained, silty, locally calcar. concretions in discontin. beds, lt. gray; marine megafossils. On Sherman Sheet (1967) east of Sabine River.
Primary rock type	clay or mud
Secondary rock type	fine-grained mixed clastic
Other rock types	sandstone; sand
Lithologic constituents	Major Sedimentary > Clastic > Mixed-clastic > Siltstone-Mudstone (Bed) Unconsolidated > Fine-detrital > Clay (Bed) Minor Sedimentary > Clastic > Sandstone (Bed) Incidental Sedimentary > Clastic > Sandstone (Bed)
Map references	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
Unit references	Bureau of Economic Geology, 1972, Dallas sheet, Geologic Atlas of Texas, Bureau of Economic Geology, University of Texas at Austin, scale 1:250,000. Bureau of Economic Geology, 1967, Sherman Sheet, Geologic Atlas of Texas: University of Texas at Austin, Bureau of Economic Geology, scale 1:250,000. Bureau of Economic Geology, 1974, Austin Sheet, Geologic Atlas of Texas, University of Texas, Bureau of Economic Geology, scale 1:250,000.
Geographic coverage	Bastrop - Bell - Bexar - Caldwell - Falls - Guadalupe - Hays - Milam - Travis - Williamson