HR: 11:10h
AN: U52A-04 INVITED     [Abstracts]
TI: Surface Uplift History of the Central Andes: Implications for the Growth of Orogenic Plateaus
AU: * Garzione, C N
EM: garzione@earth.rochester.edu
AF: Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, United States
AU: Hoke, G D
EM: gdhoke@earth.rochester.edu
AF: Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, United States
AU: Libarkin, J C
EM: libarkin@msu.edu
AF: Department of Geological Sciences, Michigan State University, East Lansing, MI 48824, United States
AU: MacFadden, B J
EM: bmacfadd@flmnh.ufl.edu
AF: Florida Museaum of Natural History, University of Florida, Gainesville, FL 32611, United States
AU: Withers, S
EM: sauniaw@gmail.com
AF: Department of Geological Sciences, Ohio University, Athen, OH 45701, United States
AB: Sedimentation, paleoelevation, and incision histories provide important constraints on the timing and magnitude of regional surface uplift of mountain belts that point to specific processes that led to surface uplift. The sedimentary record and stable isotopic compositions of carbonates are used to reconstruct the late Miocene subsidence history, paleoenvironment, and paleoelevation of the northern Altiplano basin. Multiple paleoelevation proxies, including paleoleaf physiognomy, δ¹⁸O paleoaltimetry, and Δ₄₇ paleothermometry, suggest that the Altiplano rose by 2.5±0.5 km to 3.5±0.5 km to its current elevation between ~10 and 7 Ma. Geomorphic evidence from widespread, low-relief paleosurfaces on both the eastern and western flanks of the Andes also shows that the onset of rapid incision of paleosurfaces occurred between ~10 and 6.5 Ma over the entire width of the mountain belt and over at least 5° latitude. Stream profile analysis of the drainage systems that incise these paleosurfaces has been inferred to reflect ~1 to 2 km of surface uplift of the flanks of the Andes. Combining geomorphic evidence with paleoelevation constraints, the paleotopographic evolution of the Andes is reconstructed over the late Miocene. Late Miocene regional surface uplift requires the removal of mantle lithosphere as the dominant geodynamic mechanism for raising the plateau during this time. However, crustal thickening and redistribution of crust by erosion/sedimentation and/or lower crustal flow set the limit of surface uplift. Regional surface uplift of the Andean plateau in the late Miocene predicts a decrease in the horizontal deviatoric stress in the plateau that is consistent with observations of upper crustal shortening, sedimentation rates, and magmatism in the plateau. Shortening ceased across the plateau between 10 and 7 Ma, coincident with widespread ignimbrite eruptions and an abrupt decrease in sedimentation rates. The combination of geodynamic processes that appear to have occurred in the Andes in late Miocene time, including removal of high density lower lithosphere and redistribution of crust by erosion/sedimentation and flow of low density middle-lower crust, are likely mechanisms for building broad, flat, high elevation plateaus in convergent tectonic settings.
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8169 Sedimentary basin processes
DE: 8177 Tectonics and climatic interactions
SC: Union [U]
MN: 2007 Joint Assembly