TY - JOUR
T1 - Where did the Arizona-Plano Go? Protracted Thinning Via Upper- to Lower-Crustal Processes
AU - Jepson, Gilby
AU - Carrapa, Barbara
AU - George, Sarah W.M.
AU - Reeher, Lauren J.
AU - Kapp, Paul A.
AU - Davis, George H.
AU - Thomson, Stuart N.
AU - Amadori, Chiara
AU - Clinkscales, Christopher
AU - Jones, Sean
AU - Gleadow, Andrew J.W.
AU - Kohn, Barry P.
N1 - Publisher Copyright:
© 2022. American Geophysical Union. All Rights Reserved.
PY - 2022/4
Y1 - 2022/4
N2 - Mesozoic-Cenozoic subduction of the Farallon slab beneath North America generated a regionally extensive orogenic plateau in the southwestern US during the latest Cretaceous, similar to the modern Central Andean Plateau. In Nevada and southern Arizona, estimates from whole-rock geochemistry suggest crustal thicknesses reached ∼60–55 km by the Late Cretaceous. Modern crustal thicknesses are ∼28 km, requiring significant Cenozoic crustal thinning. Here, we compare detailed low-temperature thermochronology from the Catalina metamorphic core complex (MCC) to whole rock Sr/Y crustal thickness estimates across southern Arizona. We identify three periods of cooling. A minor cooling phase occurred prior to ∼40 Ma with limited evidence of denudation and ∼10 km of crustal thinning. Major cooling occurred during detachment faulting and MCC formation at 26–19 Ma, corresponding to ∼8 km of denudation and ∼8 km of crustal thinning. Finally, we document a cooling phase at 17–11 Ma related to Basin and Range extension that corresponds with ∼5 km of denudation and ∼9 km of crustal thinning. During the MCC and Basin and Range extension events, the amount of denudation recorded by low-temperature thermochronology can be explained by corresponding decreases in the crustal thickness. However, the relatively limited exhumation prior to detachment faulting at ∼26 Ma recorded by thermochronology is insufficient to explain the magnitude of crustal thinning (∼10 km) observed in the whole rock crustal thickness record. Therefore, we suggest that crustal thinning of the Arizona-plano was facilitated via ductile mid- to lower-crustal flow, and limited upper-crustal extension at 50–30 Ma prior to detachment faulting and Basin and Range extension.
AB - Mesozoic-Cenozoic subduction of the Farallon slab beneath North America generated a regionally extensive orogenic plateau in the southwestern US during the latest Cretaceous, similar to the modern Central Andean Plateau. In Nevada and southern Arizona, estimates from whole-rock geochemistry suggest crustal thicknesses reached ∼60–55 km by the Late Cretaceous. Modern crustal thicknesses are ∼28 km, requiring significant Cenozoic crustal thinning. Here, we compare detailed low-temperature thermochronology from the Catalina metamorphic core complex (MCC) to whole rock Sr/Y crustal thickness estimates across southern Arizona. We identify three periods of cooling. A minor cooling phase occurred prior to ∼40 Ma with limited evidence of denudation and ∼10 km of crustal thinning. Major cooling occurred during detachment faulting and MCC formation at 26–19 Ma, corresponding to ∼8 km of denudation and ∼8 km of crustal thinning. Finally, we document a cooling phase at 17–11 Ma related to Basin and Range extension that corresponds with ∼5 km of denudation and ∼9 km of crustal thinning. During the MCC and Basin and Range extension events, the amount of denudation recorded by low-temperature thermochronology can be explained by corresponding decreases in the crustal thickness. However, the relatively limited exhumation prior to detachment faulting at ∼26 Ma recorded by thermochronology is insufficient to explain the magnitude of crustal thinning (∼10 km) observed in the whole rock crustal thickness record. Therefore, we suggest that crustal thinning of the Arizona-plano was facilitated via ductile mid- to lower-crustal flow, and limited upper-crustal extension at 50–30 Ma prior to detachment faulting and Basin and Range extension.
KW - Arizona-plano
KW - crustal thickness estimates
KW - lower-crustal flow
KW - metamorphic core complex
KW - thermochronology
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U2 - 10.1029/2021JB023850
DO - 10.1029/2021JB023850
M3 - Article
AN - SCOPUS:85128729921
SN - 2169-9313
VL - 127
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
IS - 4
M1 - e2021JB023850
ER -