GEOLEX

Summary of Citation: Antero

Publication:
Johnson, J.H., 1937, Algae and algal limestone from the Oligocene
   of South Park, Colorado: Geological Society of America
   Bulletin, v. 48, no. 9, p. 1227-1236

Usage in Publication:
Antero formation

Modifications:	Geologic Province:	Dominant Lithology:
First used	South Park basin	Limestone

Summary:
Algal limestone laid down in several long, narrow, partly connected basins in pre-Cambrian rocks along east margin of South Park in central CO (mostly Park Co) in the South Park constitutes the main portion of Oligocene Antero formation. The limestones are yellowish white, locally porous, and silicified. The original deposit was probably a porous calcareous tufa. Two types of deposits found: l) narrow, fringing reefs which probably formed near the shores of an old lake; and 2) widespread flat beds which developed in the southern part of the lake south-southwest of present day Hartsel, CO. [Author refers to Stark and others, The geologic history of South Park, Colorado, which was published by Geological Society of America Memoir 33 in 1949].

Summary of Citation: Antero

Publication:
Stark, J.T., Johnson, J.H., Behre, C.H., Jr., Powers, W.E.,
   Howland, A.L. and Gould, D.B., 1949, Geology and origin of
   South Park, Colorado: Geological Society of America Memoir,
   33, 188 p.

Usage in Publication:
Antero formation

Modifications:	Geologic Province:	Dominant Lithology:
Overview	South Park basin	Sandstone Shale Tuff Limestone Conglomerate

Summary:
First published use with detailed lithologic descriptions. Intent to name not stated. No type locality given. Is extensive south and west of Hartsel, Ts12 to 15S, Rs75 to 76W and in main valley west of Dakota hogback from eastern end of Antero Reservoir for about 11 mi to a point 5 mi northwest of Garo, Park Co, CO in South Park basin. A few isolated patches occur to northwest extending to within 5 mi of Fairplay. Divided into lowest member composed of thin limestone beds, tuff, sandstone, conglomerate, and shale; a middle member composed of fine-grained tuff, shale, and limestone; and an upper member composed of poorly consolidated conglomerate and interbedded sandstone. Conglomerate has boulders, cobbles, and pebbles of quartzite, chert, limestone, and red sandstone, pre-Cambrian rocks, trachyte, and andesite. Two partial sections measured in T10S, R75W and in T14S, R75W. Maximum thickness about 2000 ft. Is younger than Balfour formation and older than Wagontongue formation. Fossil vertebrates, gastropods, ostracods, and wood identified. Of Oligocene age. Lower and middle members deposited in fresh-water lake. Geologic map. Measured sections.

Summary of Citation: Antero

Publication:
De Voto, R.H., 1964, Stratigraphy and structure of Tertiary
   rocks in southwestern South Park: The Mountain Geologist, v.
   1, no. 3, p. 117-126

Usage in Publication:
Antero Formation

Modifications:	Geologic Province:	Dominant Lithology:
Revised	South Park basin

Summary:
Intertongues with and overlies the Agate Creek Formation, a newly named unit, in South Park basin. Divided into a lower tuff member and an upper member, both of Oligocene age. Geologic map.

Summary of Citation: Antero

Publication:
Scott, G.R., Taylor, R.B., Epis, R.C. and Wobus, R.A., 1978,
   Geologic map of the Pueblo 1 degrees by 2 degrees quadrangle,
   south-central Colorado: U.S. Geological Survey Miscellaneous
   Investigations Series Map, I-1022, 2 sheets, scale 1:250,000,
   (Reprinted 1981)

Usage in Publication:
Antero Formation*

Modifications:	Geologic Province:	Dominant Lithology:
Revised	South Park basin

Summary:
Johnson's (1937) definition revised in that his lower part was renamed Tallahassee Creek Conglomerate by Epis and Chapin (1974) and his upper part was mapped as Trump Conglomerate by De Voto (1971), and as Wagontongue Formation by these authors. Name Antero applied only to middle part of Johnson's original unit that is a white, yellowish-gray and gray, platy siltstone, paper shale, and algal limestone. These lacustrine sediments are interlayered with numerous air-fall and ash-flow beds of Badger Creek Tuff. Where these lithologies intertongue, Antero and Badger Creek cannot be separately mapped. Revised Antero crops out over an area greater than 30 x 25 mi. Is a water-laid andesitic ash interbedded with air-fall and ash-flow tuff and lahar as much as 2,000 ft (600 m) thick. Overlies Tallahassee Creek Conglomerate and underlies Wagontongue. Is equivalent to Florissant Lake Beds. Has vertebrate fossils. Assigned an Oligocene age. Name Balfour Formation abandoned because it is equivalent in lithology, origin, and age to Antero. In South Park basin.

Summary of Citation: Antero

Publication:
Epis, R.C., Wobus, R.A. and Scott, G., 1979, Geologic map of
   the Black Mountain quadrangle, Fremont and Park Counties,
   Colorado: U.S. Geological Survey Miscellaneous Investigations
   Series Map, I-1195, 1 sheet, scale 1:62,500, Supersedes U.S.
   Geological Survey Open-File Report OF-79-652.

Usage in Publication:
Antero Formation*

Modifications:	Geologic Province:	Dominant Lithology:
Age modified	Denver basin

Summary:
Mapped with Gribbles Park, Thorn Ranch, and East Gulch Tuffs. Has a K-Ar age on biotite and sanidine of about 34 m.y. or Oligocene. Area where the four units are mapped is in Fremont Co, CO (Ts49 to 51N, Rs11 and 12E, T17S, R73W) in the Denver basin.