Marble Falls Limestone (TXPAmf;0)

State	Texas
Name	Marble Falls Limestone
Geologic age	Phanerozoic \| Paleozoic \| Carboniferous Pennsylvanian [Morrow]
Original map label	IPmf
Comments	(fr. Llano Sheet, 1981) Along Colorado River in type section, upper 270 ft mostly ls., some spiculite beds in upper part; ls. mostly v.fine grained, some fine to medium grained, in part cherty, thin to thick bedded, oolitic near middle, various shades of brownish-gray, med.-gray, and olive-gray, microfossils abundant in most beds, megafossils common(marine algae, crinoids, brachiopods, and Chaetetes); lower 115 ft mostly massive hi-calcium ls reef, v fine grained, med-dk-gray ls, with abundant blk chert, laterally reef grades to dk-gray spiculite, in part cherty; meas. thickness of formation 385 ft. (from Brownwood Sheet, 1976) Limest. and shale, mostly ls., v.fine to coarse-grained, oolites and pellets common, locally cherty and siliceous, thin beds to massive, gen. resistent, forms ledges and slopes, rapid changes in aspect laterally and vertically, white to black, weathers lt gray to dk gray. abdt marine fossils, esp. algae, crinoids, brachiopods, and Chaetetes; thickness average ca. 300 ft, varies fr. 35 to more than 400 ft.
Primary rock type	limestone
Secondary rock type	shale
Other rock types
Lithologic constituents	Major Sedimentary > Carbonate > Limestone (Bed) Minor Sedimentary > Clastic > Mudstone > Shale > Black-shale (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, 1981, Llano sheet, Geologic Atlas of Texas, Bureau of Economic Geology, University of Texas at Austin, scale 1:250,000. Paige, S., 1912, Llano-Burnet, Texas: U.S. Geological Survey, Geologic Atlas of the United States, Folio 183. [http://pubs.er.usgs.gov/publication/gf183] Cheney, M.G., 1940, Geology of north-central Texas: American Association of Petroleum Geologists Bulletin, v. 24, no. 1, p. 65-118. Bureau of Economic Geology, 1976, Brownwood sheet, Geologic Atlas of Texas, Bureau of Economic Geology, University of Texas at Austin, scale 1:250,000. Paige, S., 1912, Llano-Burnet, Texas: U.S. Geological Survey, Geologic Atlas of the United States, Folio 183. [http://pubs.er.usgs.gov/publication/gf183]
Geographic coverage	Blanco - Burnet - Kimble - Lampasas - Llano - McCulloch - Mason - San Saba