科研之友
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摘要
Constructing an accurate kinematic model for crustal thickening in the central Andes is hampered by the inability of 2-D balanced cross sections to resolve the 3-D displacement field within the poorly studied orocline core. This study presents new structural and thermochronometer data from the orocline axis in the central Andes that constrains the magnitude and timing of deformation through (1) a balanced cross section quantifying shortening perpendicular to strike, (2) field observations that constrain translational displacements parallel to strike, and (3) thermochronology that brackets the age of exhumation and deformation. Mapping results show that north directed, right-lateral motion has been accommodated on at least one major strike-slip fault in the Eastern Cordillera (EC). Shortening perpendicular to fault strike is similar to 179km (41%) for the EC and inter-Andean zone (IA) and similar to 86km (39%) for the sub-Andes (SA). Apatite fission track cooling ages indicate rapid EC/IA exhumation from 46 to 18Ma and 15 to 0Ma in the SA. Zircon and apatite (U-Th)/He ages show that rapid exhumation began 10-5Ma in the SA. These results are integrated with existing paleomagnetic and GPS rotation data in map view reconstructions to quantify the magnitude of translational faulting related to oroclinal bending. The reconstructions suggest that at least 85km of north directed translational displacement has been accommodated within the orocline core. Orogen-parallel displacement and vertical axis rotations have focused crustal thickening at the orocline core and facilitated development of a high-elevation plateau, suggesting a genetic link between large-scale oroclines and plateaus.
- 出版日期2013-9
