GEOLEX

Summary of Citation: Abrams

Publication:
Hershey, O.H., 1901, Metamorphic formations of northwestern
   California: American Geologist, v. 27, p. 225-245

Usage in Publication:
Abrams mica schist*

Modifications:	Geologic Province:	Dominant Lithology:
Named	Klamath Mountains province	Schist

Summary:
Named for Abrams post office, Coffee Creek quad, Trinity Co, CA. [No stratotype designated] Composed of thin folia of dull colored muscovite (gray, light brown, yellow, dull red) separated by irregular layers of white quartz, representing the original laminae. Very highly siliceous throughout. Is of sedimentary origin, being originally argillaceous sandstone beds in part finely laminated. Is about 1000 ft thick in upper Coffee Creek section but may be thicker at Bully Choop. Structurally underlies Salmon Hornblende Schist. Believed to be Algonkian rather than Cambrian or Silurian.

Summary of Citation: Abrams

Publication:
MacDonald, D.F., 1913, Notes on the gold lodes of the Carrville
   district, Trinity County, California, IN Contributions to
   economic geology, 1911: U.S. Geological Survey Bulletin,
   530-A, p. 9-41

Usage in Publication:
Abrams formation*

Modifications:	Geologic Province:	Dominant Lithology:
Redescribed	Klamath Mountains province	Schist Limestone

Summary:
Abrams mica schist of Hershey (1901) referred to as Abrams formation. Is described as grayish muscovite schist containing irregular bands of white quartzose material and locally some thin layers of blue and white crystalline limestone.

Summary of Citation: Abrams

Publication:
Hinds, N.E.A., 1932, Paleozoic eruptive rocks of the southern
   Klamath Mountains, California: University of California
   Publications in Geological Sciences, v. 20, no. 11, p.
   375-410

Usage in Publication:
Abrams formation*

Modifications:	Geologic Province:	Dominant Lithology:
Age modified	Klamath Mountains province

Summary:
Age changed from Algonkian age as suggested by Hershey (1901) to pre-Middle Silurian and probably pre-Silurian. [no basis given for age change] Siskiyou terrane includes Abrams and Salmon formations.

Summary of Citation: Abrams

Publication:
Mack, Seymour, 1958, Geology and ground-water features of Scott
   Valley, Siskiyou County, California: U.S. Geological Survey
   Water-Supply Paper, 1462, 98 p., (incl. geologic map, scale
   1:62,500)

Usage in Publication:
Abrams mica schist*

Modifications:	Geologic Province:	Dominant Lithology:
Age modified	Klamath Mountains province

Summary:
Thick series of metasedimentary rocks, dominantly quartz-mica schist, which is overlain unconformably by Salmon hornblende schist. Hinds (1932) introduced term Siskiyou terrane to include Abrams and Salmon schists. Exact stratigraphic position of rocks composing Siskiyou terrane is not known. Abrams and Salmon are oldest formations in area of this report [Scott Valley]. In northern and western parts of area, they are overlain unconformably by several thousand feet of greenstone and greenstone schist possibly correlative with Devonian(?) Copley greenstone of southern Klamath Mountains. In southern part of mountains surrounding Scott Valley, Chanchelulla(?) formation of probable Silurian age lies unconformably on Abrams and Salmon schists. Present evidence indicates only that Abrams and Salmon schists can be adjudged with certainty to be pre-Silurian age. Assignment to Precambrian or lower Paleozoic would be extremely tenuous.

Summary of Citation: Abrams

Publication:
Irwin, W.P., 1960, Relations between Abrams Mica Schist and
   Salmon Hornblende Schist in Weaverville quadrangle, California,
   IN Short papers in the geological sciences; Geological Survey
   research 1960: U.S. Geological Survey Professional Paper,
   400-B, p. B315-B316

Usage in Publication:
Abrams mica schist*

Modifications:	Geologic Province:	Dominant Lithology:
Mapped	Klamath Mountains province

Summary:
Geologic mapping in Weaverville quadrangle indicates that (1) structure of metamorphic rocks in that quadrangle is synclinoral and Abrams mica schist overlies Salmon hornblende schist, (2) Abrams is probably younger, rather than older, than Salmon, and (3) marble lenses are of stratigraphic significance in that they are chiefly in lower part of Abrams.

Summary of Citation: Abrams

Publication:
Davis, G.A. and Lipman, P.W., 1962, Revised structural sequence
   of pre-Cretaceous metamorphic rocks in the southern Klamath
   Mountains: Geological Society of America Bulletin, v. 73,
   no. 12, p. 1547-1552

Usage in Publication:
Abrams mica schist*

Modifications:	Geologic Province:	Dominant Lithology:
Abandoned	Klamath Mountains province

Summary:
Authors abandoned the name Abrams formation of Hershey (1901) because these rocks, as previously mapped, both underlie and overlie the unit they term the Salmon formation. They propose the name Grouse Ridge formation for the upper unit above the Salmon and Stuart Fork formation for the lower unit below the Salmon to replace their abandoned Abrams formation.

Summary of Citation: Abrams

Publication:
Irwin, W.P., 1963, Preliminary geologic map of the Weaverville
   quadrangle, California: U.S. Geological Survey Miscellaneous
   Field Studies Map, MF-275, 1 sheet, scale 1:62,500

Usage in Publication:
Abrams mica schist*

Modifications:	Geologic Province:	Dominant Lithology:
Mapped	Klamath Mountains province

Summary:
Mapped in Weaverville 15' quad, Trinity Co, CA. ["Braced on map explanation as pre-Jurassic in age. No age revision implied."] Map explanation indicates unit may be equivalent to Grouse Ridge Formation of Davis and Lipman (1962).

Summary of Citation: Abrams

Publication:
Lanphere, M.A. and Irwin, W.P., 1965, Carboniferous isotopic
   age of the metamorphism of the Salmon Hornblende Schist and
   Abrams Mica Schist, southern Klamath Mountains, California,
   IN Geological Survey research 1965: U.S. Geological Survey
   Professional Paper, 525-D, p. D27-D33

Usage in Publication:
Abrams Mica Schist*

Modifications:	Geologic Province:	Dominant Lithology:
Age modified Isotopic dating	Klamath Mountains province

Summary:
K-Ar ages on muscovite from Abrams Mica Schist range from 329 +/-13 to 309 +/-12 Ma [Carboniferous], i.e., the apparent age of metamorphism. Shown on figure sketch map of southern Klamath Mountains area.

Summary of Citation: Abrams

Publication:
Irwin, W.P., 1966, Geology of the Klamath Mountains province,
   IN Bailey, E.H., ed., Geology of northern California: California
   Division of Mines and Geology Bulletin, no. 190, p. 19-38

Usage in Publication:
Abrams mica schist*

Modifications:	Geologic Province:	Dominant Lithology:
Areal limits Reinstated	Klamath Mountains province

Summary:
Abrams Mica Schist of Hershey (1901) restricted to exclude rocks structurally underlying the Salmon Hornblende Schist. As thus restricted Abrams structurally overlies the Salmon and is synonymous with the Grouse Ridge Formation of Davis and Lipman (1962). Rocks structurally underlying the Salmon are reassigned to the Stuart Fork Formation of Davis and Lipman (1962). "Rocks named the Stuart Fork may have been included by Hershey (1901) in his Abrams, but the exclusion of this small patch should not seriously redefine the Abrams; therefore, name, Abrams, should not have been abandoned by Davis and Lipman (1962) (oral commun., W.P. Irwin, 10/18/65). Davis and Lipman (1962, p. 1548) suggest abandoning name Abrams as a result of rejection of two possible redefinitions, one of which involves required exclusion of "Hershey's type locality, the Abrams post office.." Irwin states, verbally, that Hershey (1901, p. 227) applied name Abrams, derived from the then-existing Abrams post office in that area, to rocks in upper Coffee Creek region, the lithology of which Hershey then describes. No type locality was given by Hershey, a requirement not yet established for names in early reports. Certainly, says Irwin, Hershey never meant to apply stratigraphic name to Recent alluvium underlying post office site, given by Davis and Lipman as at Upper Nash Mine and shown on Coffee Creek quad, NE 1/4, NE 1/4 sec.31,T38N,R9W. [see Lanphere & Irwin, 1987]

Summary of Citation: Abrams

Publication:
Lanphere, M.A. and Irwin, W.P., 1968, Age of primary metamorphism
   of the Abrams Mica Schist, Klamath Mountains, California
   [abs.], IN GSA abstracts for 1966: Geological Society of
   America Special Paper, 101, p. 118

Usage in Publication:
Abrams Mica Schist*

Modifications:	Geologic Province:	Dominant Lithology:
Age modified Isotopic dating

Summary:
Sr-Rb ages from Abrams Mica Schist indicate age of first metamorphism is approximately 340 Ma (early Carboniferous) which is believed to be more reliable than previous K-Ar ages of 330 to 310 Ma.

Summary of Citation: Abrams

Publication:
Lanphere, M.A., Irwin, W.P. and Hotz, P.E., 1968, Isotopic age
   of the Nevadan Orogeny and older plutonic and metamorphic
   events in the Klamath Mountains, California: Geological
   Society of America Bulletin, v. 79, no. 8, p. 1027-1052

Usage in Publication:
Abrams Mica Schist*

Modifications:	Geologic Province:	Dominant Lithology:
Age modified Isotopic dating	Klamath Mountains province

Summary:
Age of primary metamorphism of Abrams Mica Schist is approximately 380 Ma (Devonian).

Summary of Citation: Abrams

Publication:
Lanphere, M.A., Irwin, W.P. and Hotz, P.E., 1969, Geochronology
   of crystalline rocks in the Klamath Mountains, California
   and Oregon [abs.]: Geological Society of America Abstracts
   with Programs, pt. 3, Cordilleran Section, p. 34

Usage in Publication:
Abrams Mica Schist*

Modifications:	Geologic Province:	Dominant Lithology:
Age modified	Klamath Mountains province

Summary:
[Age of metamorphism of Abrams Mica Schist changed from Carboniferous to Devonian]

Summary of Citation: Abrams

Publication:
Hotz, P.E., Thurber, H.K., Marks, L.Y. and Evans, R.K., 1972,
   Mineral resources of the Salmon-Trinity Alps Primitive Area,
   California, with a section on an aeromagnetic survey and
   interpretation by Andrew Griscom, IN Studies related to
   wilderness; primitive areas: U.S. Geological Survey Bulletin,
   1371-B, p. B1-B267, (incl. geologic map, scale 1:125,000)

Usage in Publication:
Abrams Mica Schist*

Modifications:	Geologic Province:	Dominant Lithology:
Age modified	Klamath Mountains province

Summary:
Age of Abrams Mica Schist revised from Devonian to Devonian or older Paleozoic. [However paper cites age from Lanphere and others (1968) as Devonian.]

Summary of Citation: Abrams

Publication:
Irwin, W.P., 1977, Review of Paleozoic rocks of the Klamath
   Mountains, IN Stewart, J.H., Stevens, C.H., and Fritsche,
   A.E., eds., Paleozoic paleogeography of the western United
   States; Pacific Coast paleogeography symposium I: Society of
   Economic Paleontologists and Mineralogists, Pacific Section,
   Pacific Coast Paleogeography Symposium, 1, Bakersfield, CA,
   April 22, 1977, p. 441-454

Usage in Publication:
Abrams Mica Schist*

Modifications:	Geologic Province:	Dominant Lithology:
Age modified	Klamath Mountains province

Summary:
Age of Abrams Mica and Salmon Hornblende Schists revised from Devonian or older Paleozoic to: Devonian.

Summary of Citation: Abrams

Publication:
Lanphere, M.A. and Irwin, W.P., 1987, In search of the Abrams
   Post Office: California Geology, v. 40, no. 5, p. 99-103

Usage in Publication:
Abrams Schist*

Modifications:	Geologic Province:	Dominant Lithology:
Redescribed Overview	Klamath Mountains province

Summary:
Unit renamed the Abrams Schist in accordance with art. 30b of the 1983 North American Stratigraphic Code.