Structural Geology of the Sierra de Los Cacapas, Northeastern Baja California, Mexico, and Imperial County, California PDF Download
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Author: Frederick L. Barnard
Publisher:
ISBN:
Category : Geology
Languages : en
Pages : 380
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Author: Frederick L. Barnard
Publisher:
ISBN:
Category : Geology
Languages : en
Pages : 380
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Book Description
Author: Frederick L. Barnard
Publisher:
ISBN:
Category : Geology
Languages : en
Pages : 155
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Author: Frederick L. Barnard
Publisher:
ISBN:
Category :
Languages : en
Pages : 155
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Author: Martin Eric Siem
Publisher:
ISBN:
Category : Geochemistry
Languages : en
Pages : 488
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Mid-Tertiary to recent extension in the southern Salton Trough - northern Gulf Extensional Province has resulted in the formation of the Sierra El Mayor core complex. Structural geometries and style of deformation closely resemble those of the turtleback structures in central Death Valley, as opposed to the core complexes in southeastern California and southern Arizona. Displacement along a stacked system of detachment faults was accomplished by brittle deformation and placed unmetamorphosed late-Miocene to Pleistocene marine and non-marine sedimentary rocks on upper amphibolite facies metamorphic tectonites. The metamorphic rocks have been pervasively intruded by igneous rocks of various ages, ranging in composition from tonalites to monzogranites. Mid-miocene hydrothermal metamorphism retrograded the core rocks to greenschist facies, and clasts of these rocks are found in a syntectonic sedimentary breccia indicating that hydrothermal fluids preceded and facilitated faulting. Foliation within metamorphic rocks has been transposed and refolded into a WNW to NW trending antiform. A parallel trending antiform is defined by the dips on the uppermost detachment fault. Penetrative high-angle conjugate normal faults and fractures that are oriented perpendicular to the antiform have pervasively brecciated the rocks within the core. The maximum strain direction, as determined from the orientation of the high-angle faults beneath the upper detachment, is east-west. This is consistent with kinematic indicators that give a WNW sense of movement on the detachment faults. Orientation of the high-angle normal faults above the upper detachment indicates a more NW - directed maximum strain. The structurally lowest detachment zone exposed represents a mid-crustal shear zone upon which mid- and upper-crustal rocks were tilted and cataclastically deformed in response to the opening to the proto-Gulf. Syndepositional marine sediments were deposited directly on the uplifted shear zone. Continued extension along detachment faults tectonically thinned and removed the late-Miocene to Pliocene marine deposits and locally placed Pleistocene redbeds directly against the metamorphic basement. Subsequent high-angle normal faults that cut the detachments are considered to sole into a presently active mid crustal shear zone. Extension associated with the development of Sierra El Mayor core complex is consistent with Mid-Miocene to present Pacific-North America plate motions.
Author: Malcolm A. Love Library. Sciences and Engineering Library
Publisher:
ISBN:
Category : Geology
Languages : en
Pages : 130
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Author: Paula Jean Leier-Engelhardt
Publisher:
ISBN:
Category : Geology
Languages : en
Pages : 338
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The Sierra las Pinta is located 122 km south of Mexicali, Baja California Norte, Mexico. Paleozoic rocks are on the extreme north and south ends of the range. The Paleozoic rocks were studied to describe the stratigraphy, determine if correlations could be made between units in each area and interpret the regional tectonic implications. The section in the northern area (Area 1) is approximately 520 m thick and is divided into six units: Unit 1, calcareous siltstone and calcareous sandy siltstone; Unit 2, siltstone interbedded with calcareous rare crinoidal grainstone and rare granule conglomerates; Unit 3, graded sandy crinoidal grainstone; Unit 4, massive and normally graded beds of coarse sandstone and granule to cobble conglomerate; Unit 5, basalt flows with rare basalt conglomerate and hyalotuffs; and Unit 6, bedded chert and calcareous argillite in thrust contact with underlying units. Lophyophyllid corals and brachiopods from Unit 3 suggest a possible Carboniferous age. The section in the southern area (Area 2) is approximately 720 m thick and is divided into four units: Unit A, bedded chert and argillite; Unit B, fine sandstone, coarse siltstone and granule conglomerate debris flows, probably formed in a submarine fan environment ; Unit C, a deformed limestone and shale sequence ; and Unit D, pillow basalts and basalt flows. Based on conodonts recovered from Unit A and conodont fragments recovered from Unit C, the section is Early Devonian to Early Mississippian in age. Detailed thin section analysis suggests the terrigenous rocks from each area were derived from similar terranes and had a definite cratonal source. The lithic grain population includes quartz arenite and chert grains, no metamorphic lithic grains lithic basalts and a small but persistent percentage of volcanic grains. Minor and trace element analyses of from each area indicate the basalts were erupted during a rifting event, perhaps in a back-arc basin near a continental margin. The rocks from Area 1 and Area 2 cannot be correlated on a one-to-one basis, but could well have been deposited in the same basin. Rocks of similar provenance, age and lithologic associations are found in Baja California Norte, Sonora, and Sinaloa, and all these sections may relate to events which formed the Havallah and Schoonover sequences in Nevada.
Author: R. Gordon Gastil
Publisher: Geological Society of America
ISBN: 0813711401
Category : Science
Languages : en
Pages : 214
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Author: Richard A. Dubiskas
Publisher:
ISBN:
Category : Geology, Stratigraphic
Languages : en
Pages : 176
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Author: Matthew James Melnyk
Publisher:
ISBN:
Category : Geology, Structural
Languages : en
Pages : 190
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Author: Carl Hugh Beal
Publisher: Geological Society of America
ISBN: 0813710316
Category : Science
Languages : en
Pages : 160
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