HR: 1340h
AN: T23C-1535    [Abstracts]
TI: Using the Foreland Basin Record to Constrain Orogenic Evolution: Examples from the Alps, Andes and North America Cordillera
AU: * Carrapa, B
EM: bcarrapa@uwyo.edu
AF: University of Wyoming, Department of Geology and Geophysics, 1000 East University Avenue, Laramie, WY 82070, United States
AU: DeCelles, P G
EM: decelles@email.arizona.edu
AF: University of Arizona, Department of Geosciences, Gould-Simpson Bldg. 331, Tucson, AZ 85721, United States
AU: Gupta, S
EM: s.gupta@imperial.ac.uk
AF: Imperial College of London, Department of Earth Science and Engineering, South Kensington Campus, London, SW7 2AZ, United Kingdom
AU: Sudo, M
EM: msudo@geo.uni-potsdam.de
AF: University of Potsdam, Karl-Liebknecht-Strasse 24, Golm-Potsdam, 14476, Germany
AB: Foreland basin deposits are a unique archive of information regarding the nature of the rocks once present in the hinterland and the processes responsible for erosion, deformation and deposition within the source-sink coupled system. Different thermochronometers, because of their different closure temperatures, can answer different but complementary questions when applied to foreland basin strata. Detrital ⁴⁰Ar/³⁹Ar on white micas from the peripheral Alpine foreland deposits highlight important differences in the rates of erosion between the retro-wedge (Po Plain foreland basin: NW Italy) and the pro-wedge (Bârreme wedge-top basin: SE France). Whereas ⁴⁰Ar/³⁹Ar ages from the Po Plain (pro-wedge) document fast Eocene-Oligocene erosion coherent with active tectonic deformation and high-grade metamorphism, ⁴⁰Ar/³⁹Ar ages from the Bârreme Basin (retro-wedge) show that Eocene-Oligocene foreland deposits were mainly derived from sedimentary cover that did not experience enough tectonic burial and erosion during the Alpine orogeny. This documents how orogenic growth can be strongly asymmetric putting important constraints on numerical modeling input parameters. Detrital ⁴⁰Ar/³⁹Ar ages on white micas from the Tertiary retroarc foreland basin within the central Andes constrain sediment provenance and pre-Tertiary (360-390 Ma) cooling. Apatite fission track (AFT) ages can instead constrain Tertiary rapid erosion (0.4 to >1mm/yr) and show that during the Eocene the foreland basin was receiving material from a growing orogenic wedge. The fact that AFT ages are not reset after deposition combined with the progressive shallowing upward of the foreland stratal dip suggests syn-depositional deformation and structural growth within a wedge-top depozone. Detrital AFT ages from the North America Cordilleran retroarc foreland basin deposits are younger than the depositional age of the hosting strata documenting total annealing (i.e., T > ca. 110° C) owing to significant burial after deposition. The AFT ages in this case record cooling and erosion during forelandward propagation of the Absaroka and Hogsback thrusts. AFT ages from the Frontier (78.9 ± 4.6 Ma), Gannett (63.6 ± 4.1 Ma), and Morrison (58.6 ± 6.5 Ma) Formations thus constrain the timing of thrusting. Detrital thermochronology applied to foreland basin deposits has proven to be successful in tackling key geological issues such as the relationships between tectonics and erosion by constraining provenance, rates and patterns of erosion and deformation both within the hinterland and foreland regions.
DE: 1140 Thermochronology
DE: 8005 Folds and folding
DE: 8104 Continental margins: convergent
DE: 8169 Sedimentary basin processes
DE: 8175 Tectonics and landscape evolution
SC: Tectonophysics [T]
MN: 2007 Fall Meeting