Discovery of the base of the Pinal Schist and the Bear Canyon sequence below it in the eastern Metamorphic terrane of the Dos Cabezas mountains, Cochise County, Arizona
- Sonoma State Univ., Rohnert Park, CA (United States). Geology Dept.
The eastern metamorphic terrane of the Dos Cabezas mountains is underlain by Pinal Schist (PS). Recent detailed mapping along the western edge of this terrane shows that a flat planar regional unconformity (UC) bounds this Pinal body at its western stratigraphic base. Below the UC lies 8 km[sup 2] of greenschist facies metapelites and metafelsites here given the provisional name of the Bear Canyon sequence (BCS). The PS above the UC is over 10 stratigraphic km, grading from 1 km conglomerate at the base (clasts are metafelsites and metasediments with very minor quartz and granite) up into 3 km of sandstones and then pelite, all with greenschist facies overprint. Relict bedding with abundant crossbedding is common; the sequence is upright. Foliation parallels bedding. Lineation is absent. The UC itself is well exposed in two places, on both sides of Happy Camp Canyon (HCC). On the west of HCC, the surface is exposed at the mouth of Bear Canyon (NW1/4 Sec. 31, T13S R28E) striking south and then southwest about 4 km, ending in the N center of Sec. 12, T14S R27E. The unconformity and the Pinal above it lie NS 30E in the north and smoothly swing to NE 50 SE in the south. Below the UC are 6 km[sup 2] of metasandstone and metafelsites of the BCS. The metasandstone is quartz-sericite schist with strong lineation ([minus]50 S70E) in its northern km of exposure. Bedding and foliation are NS 60 E in N, and NE 70 SE in S. This schist body is intruded on the E by a dike of quartz-phyric metafelsite to 1 km wide which underlies the UC along its entire length. The felsite shows strong relict flow layering and no foliation. Flow layering is NS 90 in the N, and strikes and dips variably in the S. A 1/4 km[sup 2] metafelsite plug intrudes the schist on the W, with flow layering NE 90. The two exposures of the UC are separated by a Precambrian normal fault striking N45E and dipping moderately SE under HCC alluvial fill; it has about a km of dip slip.
- OSTI ID:
- 5341834
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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