Young convergent-margin orogens, climate, and crustal thickness-A Late Cretaceous-Paleogene Nevadaplano in the American Southwest?

The N-S-trending Andes surmount South American lithosphere above the east-descending Nazca plate. The highest mountains, underlain by similar to 70-km-thick crust, cap the Cordillera at 25 degrees S, an extremely arid region. In contrast, the precipitation-drenched fjordland at 45 degrees S is supported by similar to 35-km-thick crust. The Cascade and Sierra Nevada ranges in the western United States display comparable N-S trends and latitudinal rainfall patterns. Westerly winds supply abundant moisture to the northwest, but precipitation diminishes southward, producing increased aridity where the Sierra achieves its maximum regional elevation around Mount Whitney. Overthickened, now delaminating, similar to 42-55-km-thick crust of the southern Sierra exceeds that of the similar to 35-km-thick northern Sierra and the active Cascade arc. Contrasts in orogenic crustal thickness in California are not as marked as in the Andes because Sierran arc construction ceased near the end of Cretaceous time. Geologic, geochemical, and stable isotopic data suggest that a Nevadaplano occupied central + southern Nevada + western Utah in the rain shadow of the Late Cretaceous-Paleogene arc. The similar to 40-45-km-thick Colorado Plateau crust lies well downwind from the southern Sierra, and, depending on when it became elevated, it might represent part of a broader highland that collapsed during Neogene Basin and Range extension.