Timing and structural expression of the Nevadan orogeny, Sierra Nevada, California

摘要: The Nevadan orogeny was a very short-lived event in the Late Jurassic that involved deformation of great variety rock types and Paleozoic Mesozoic terranes throughout extent Sierra Nevada. structures show variation style but relatively constant orientations. These relations can be explained by considering prior histories various terranes. Slaty cleavages tight folds are characteristic main-phase western belt island-arc volcanic rocks flysch-type sedimentary rocks. A strip phyllites greenschists along eastern edge apparently represents similar were deformed metamorphosed at greater depths, probably during underthrusting beneath central belt. metasedimentary metavolcanic shows most extreme structures, from weak, spaced to crenulation south, where polyphase formed structural basement, slaty phyllitic asymmetric isoclinal north, basement lack penetrative pre-Nevadan fabrics. Eastward-directed thrust faulting important only northern part range, intense. Triassic magmatic arc-volcanic defines core major synclinorium, contain asymmetric, folds. late phase consisting northeast-trending minor folds, also marked style, intensely developed north weakly south. regional geometry indicate on west significant crustal shortening belts. features suggest resulted collision island arc (western belt) with an andean-type (eastern situated North America.