GEOLEX

Summary of Citation: Mariposa

Publication:
Becker, G.F., 1885, Notes on the stratigraphy of California:
   U.S. Geological Survey Bulletin, 19, 28 p.

Usage in Publication:
Mariposa beds

Modifications:	Geologic Province:	Dominant Lithology:
Named Biostratigraphic dating	Sierra Nevada province	Slate

Summary:
Named for occurrence on Mariposa estate [southeast of Bagby] Mariposa Co, CA. Consists of immense thickness of highly metamorphosed auriferous slates occurring along foothills from Mariposa to Nevada Cos, CA. Thin-bedded strata prevail and silicification and serpentinization are predominant characteristics. Beds are upturned in nearly vertical position. Unconformably underlies Chico beds. Contains AUCELLA PIOCHII and other fossils indicating Jurassic age. Regarded as identical with Knoxville beds of Coast Ranges.

Summary of Citation: Mariposa

Publication:
Turner, H.W. and Ransome, F.L., 1897, Description of the Sonora
   quadrangle [California]: U.S. Geological Survey Geologic
   Atlas of the United States, Sonora folio, no. 41, 7 p., scale
   1:125,000

Usage in Publication:
Mariposa formation*

Modifications:	Geologic Province:	Dominant Lithology:
Redescribed	Sierra Nevada province	Slate Shale Conglomerate Schist

Summary:
Shown on geologic map of Sonora 30' quad, part of Mariposa, Tuolumne, Merced, and Stanislaus Cos, CA. Occurs in three belts. Rocks of eastern main belt are chiefly clay slates and shales with some coarse grit and conglomerate. In southwestern extension of middle belt are highly metamorphosed mica- and andalustic-schists (shown separately on map). Formation attains maximum development in Mariposa Co portion of quad; it is here in eastern belt that first fossils were found from slates northwest of Bear Valley in ravine known as Hell Hollow [this area probably included in site of Mariposa estate].

Summary of Citation: Mariposa

Publication:
Ransome, F.L., 1900, Description of the Mother Lode district
   [California]: U.S. Geological Survey Geologic Atlas of the
   United States, Mother Lode folio, no. 63, 11 p., scale
   1:63,360

Usage in Publication:
Mariposa formation*

Modifications:	Geologic Province:	Dominant Lithology:
Redescribed	Sierra Nevada province	Slate Sandstone Conglomerate

Summary:
Shown on geologic map of Mother Lode district, CA. Mariposa formation consists chiefly of cleavable and homogenous clay slates with locally varying amounts of sandstone and conglomerate.

Summary of Citation: Mariposa

Publication:
Harder, E.C., 1910, Some iron ores of western and central
   California: U.S. Geological Survey Bulletin, 430, p. 219-227

Usage in Publication:
Mariposa slate*

Modifications:	Geologic Province:	Dominant Lithology:
Areal limits Redescribed	Sierra Nevada province

Summary:
Associated with amphibolite schist are bands of Mariposa slate in Calaveras Co, CA. Mariposa slate is Jurassic age.

Summary of Citation: Mariposa

Publication:
Eric, J.H., Stromquist, A.A. and Swinney, C.M., 1955, Geology
   and mineral deposits of the Angels Camp and Sonora quadrangles,
   Calaveras and Tuolumne Counties, California: California
   Division of Mines and Geology Special Report, no. 41, 55 p.,
   (incl. geologic map, scale 1:24,000)

Usage in Publication:
Mariposa formation*

Modifications:	Geologic Province:	Dominant Lithology:
Redescribed	Sierra Nevada province	Slate Graywacke Sandstone

Summary:
Mapped in Angels Camp and Sonora quads, Calaveras and Tuolumne Cos, CA. Lithology varies; in places slate is minor constituent. In Sonora quad about 2/3rds of unit are dark-gray to black slates; rest are metamorphosed fine- to coarse-grained sandstone and grit, graywacke, pebble conglomerate, tuffaceous sandstone and sandy to silty tuff. Believed to be in depositional contact with Logtown Ridge formation along east flank of Peoria Mountain and along flanks of Bear Mountain. Is exposed in partly fault-bounded northwest-trending belt just west of Mother Lode fault system. Belt ranges in thickness up to 12,000 ft. Narrow belt 250 to 1500 ft wide is exposed just west of Bear Mountain. Measured section along Brower Creek and Angels Creek, Calaveras Co. Age is Late Jurassic based on fossils. Discussion of disagreement among paleontologists as to proper stages.

Summary of Citation: Mariposa

Publication:
Clark, L.D., 1964, Stratigraphy and structure of part of the
   western Sierra Nevada metamorphic belt, California: U.S.
   Geological Survey Professional Paper, 410, 70 p., (incl.
   geologic maps, scale 1:31,680 and 1:62,500)

Usage in Publication:
Mariposa formation*

Modifications:	Geologic Province:	Dominant Lithology:
Revised Areal limits Biostratigraphic dating

Summary:
Mariposa formation restricted to rocks in central fault block and Melones fault zone that are continuous on surface of type area [Mariposa estate, southeast of Bagby], or are repeated across strike by adequately documented structures. Brower Creek volcanic member of Mariposa formation is here applied to sequences of volcanic rocks, chiefly volcanic breccia, that forms part of Mariposa formation north of Stanislaus River. Mariposa formation exclusive of member consists largely of slate, tuff, graywacke and conglomerate. Overlies Penon Blanco volcanics (new). Age is Late Jurassic based on fossils identified by R.W. Imlay (written commun., 1959). Fossil list included.

Summary of Citation: Mariposa

Publication:
Duffield, W.A. and Sharp, R.V., 1975, Geology of the Sierra
   foothills melange and adjacent areas, Amador County, California:
   U.S. Geological Survey Professional Paper, 827, 30 p., (incl.
   geologic map, scale 1:24,000)

Usage in Publication:
Mariposa Formation*

Modifications:	Geologic Province:	Dominant Lithology:
Overview	Sierra Nevada province

Summary:
Shown on geologic map of western Sierra foothills between Cosumnes and Mokelumne Rivers, Amador Co, CA. Distinct lithologies of both formation and Brower Creek Volcanic Member shown. Detailed lithologic descriptions in text. Overlies Logtown Ridge Formation. Narrow band (about 250 to 800 m) of distinctive sheared rocks separates Mariposa Formation on west from large granitic pluton and Calaveras Formation of eastern belt to the east. Although unit is considered Late Jurassic (late Oxfordian and early Kimmeridgian Stages), recovery of pelecypod BUCHIA CONCENTRICA above base 1.2 km north-northwest of Plymouth (Imlay, 1961) demonstrates a late Oxfordian and early Kimmeridgian age there.