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Thermal evolution of the Sierra Nevada: Tectonic implications of new heat flow data
Author(s) -
Saltus Richard W.,
Lachenbruch Arthur H.
Publication year - 1991
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/90tc02681
Subject(s) - geology , lithosphere , basin and range topography , basin and range province , tectonics , advection , cenozoic , tectonic uplift , structural basin , geomorphology , seismology , physics , thermodynamics
Eight new heat flow measurements in the southern Sierra Nevada constrain models of thermal evolution and lithospheric structure. Low reduced heat flows (18 to 21 mW/m²) in the southwest Sierra Nevada are consistent with previous results from the northwestern and central Sierra Nevada and extend the known region of linear heat flow‐heat production correlation an additional 150 km to the south. Isostatic residual gravity and measured rock densities are also linearly correlated in the central Sierra Nevada, suggesting a general association between the upper crustal distribution of density and heat production. The linear residual gravity‐density relation implies that isostatic residual gravity anomalies have upper crustal sources and therefore is evidence against a flexural model of Cenozoic Sierra Nevada uplift. New reduced heat flows measured in the southeast Sierra Nevada are relatively high (32 to 57 mW/m²) and correlate spatially with a region of high seismicity that includes extensional earthquake swarms; this correlation supports the view that Basin and Range extensional tectonics and associated magmatic processes are encroaching on the eastern Sierra Nevada. In the stable southwest Sierra Nevada, as in the central and northwestern Sierra Nevada, the persistence of low reduced heat flow at the surface is consistent with a thermal origin for the Cenozoic uplift of the Sierra Nevada, provided the conductive lithosphere is at least 60 to 90 km thick. Simple order‐of‐magnitude calculations show that thermal uplift models combining mechanisms such as advective warming and thinning of the mantle lithosphere, advection of basaltic magma and heat into the crust, simple thermal expansion, and eclogite‐to‐basalt phase conversion can account for the timing and amount of Cenozoic Sierra Nevada uplift. Thermal models do not need the assumptions of unusual lithospheric strength and crustal buoyancy required by mechanical models for Cenozoic uplift driven by a Mesozoic crustal root.