Dissertation
THE GEOMETRY, KINEMATICS, AND TIMING OF THE CENTRAL ANDEAN THRUST BELT OF SOUTHERN BOLIVIA: A FIELD BASED TEST OF CORDILLERAN CYCLICITY
Doctor of Philosophy (PhD), Washington State University
01/2019
Handle:
https://hdl.handle.net/2376/111643
Abstract
The Andes are an ideal setting to explore orogenic wedge evolution and the cyclical tectonic processes in Cordilleran systems. However, reliable estimates of total crustal shortening and timing constraints for fold-thrust belt development are lacking in the central Andean retroarc of southern Bolivia (~21°S). We (1) estimate crustal shortening by integrating new geologic mapping to construct a balanced cross section across the Subandean zone, Interandean zone, and Eastern Cordillera; (2) develop a kinematic model for the retroarc thrust belt; and (3) estimate crustal budgets and average crustal thicknesses over the region; (4) integrate fission track and
(U-Th)/He ages from zircon and apatite to quantify the timing and rates of thrust belt propagation; (5) quantify the crustal thermal conditions and timing of a pre-Cenozoic tectonic event using Raman spectroscopy on carbonaceous materials. We estimate 337 ± 69 km (36% ± 7%) of total retroarc shortening. The thrust belt developed by emplacement of two ~10–12-km-thick basement thrust sheets that distribute slip into overlying sedimentary rocks. Our range of crustal shortening values can account for 90%–118% of the current crustal area. Cooling age data show that retroarc shortening in the Eastern Cordillera initiated at ~43 Ma. Deformation migrated eastward from ~25 to 17 Ma across the western Interandean zone but stalled for ~6 Myr. Eastward advance of deformation into the
eastern Interandean zone and Subandean zone resumed by ~11–8 Ma, which we interpret as rapid orogenic wedge expansion induced by eclogitic delamination and corresponding hinterland surface uplift at ~13 Ma. Changing climatic conditions fold-thrust belt expansion between ~8.5 to 1.5 Ma. Our data reveal space-time variations in orogenic wedge evolution consistent with models of Cordilleran cyclicity and lithospheric removal, with important additional influences of erosion, climate, and rock rheology. The peak temperature data along with low temperature cooling age data refine the timing of Paleozoic orogenesis at this latitude. Peak temperature conditions were attained during the eastward migration of a foreland basin across this region between ~420 and ~318 Ma. Erosional exhumation between ~352 and ~294 Ma was the result of eastward expansion of orogenesis during the Carboniferous Hercynian event.
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Details
- Title
- THE GEOMETRY, KINEMATICS, AND TIMING OF THE CENTRAL ANDEAN THRUST BELT OF SOUTHERN BOLIVIA: A FIELD BASED TEST OF CORDILLERAN CYCLICITY
- Creators
- Ryan Bruce Anderson
- Contributors
- Sean P Long (Advisor)Catherine M Cooper (Committee Member)Jeffrey D Vervoort (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 319
- Identifiers
- 99900581619601842
- Language
- English
- Resource Type
- Dissertation