HR: 1340h
AN: T53B-1423    [Abstracts]
TI: 3-D critical taper wedge mechanics of two low-taper wedges: a comparison of modeled wedge strength and structural styles
AU: * Guzofski, C A
EM: guzofski@fas.harvard.edu
AF: Harvard University, Dept of Earth and Planetary Sciences 20 Oxford St., Cambridge, MAs 02138 United States
AU: Shaw, J H
EM: shaw@eps.harvard.edu
AF: Harvard University, Dept of Earth and Planetary Sciences 20 Oxford St., Cambridge, MAs 02138 United States
AU: Bilotti, F
EM: frank.bilotti@chevron.com
AF: Chevron Energy Technology Company, 1500 Louisiana St., Houston, TX 77003 United States
AU: Corredor, F
EM: corredor@fas.harvard.edu
AF: Harvard University, Dept of Earth and Planetary Sciences 20 Oxford St., Cambridge, MAs 02138 United States
AB: Using a new implementation of critical taper wedge mechanics, we investigate the relationship between structural styles and calculated mechanical strength properties in two unique fold and thrust belts. Through the analysis of regional seismic reflection profiles and detailed bathymetric data, we define the wedge taper geometry of the fold and thrust belts and delineate various three-dimensionally varying internal strength parameters, including frictional coefficients and density. We subsequently calculate other strength parameters, including fluid pressures, and compare these with structural features and styles imaged in the seismic reflection data. We utilize this approach to investigate and compare the compressive toe of the Niger Delta and the Southern Caribbean accretionary prism of Colombia. Both fold and thrust belts have a regional detachment that dips down toward the continent, while imbricate thrust faulting builds a bathymetric slope that dips away from the shelf, defining an internally deforming wedge. This fold and thrust belt geometry is consistent with a Coulomb critical taper wedge model, where an influx of sediments causes the wedge to internally deform, thus maintaining its critical taper angle. In the case of the Southern Caribbean accretionary prism deformation results from the collision of the Caribbean and South American plates, while in the Niger Delta, deformation is driven by gravitational collapse of the shelf sediments. While the driving mechanisms in these wedges are therefore quite different, the fold and thrust belts share many similarities including a low angle taper, which is likely controlled by the fact that they both have a weak basal detachment. We present evidence that in both fold and thrust belts, regions where the basal detachment is calculated to be stronger (lower calculated fluid pressures) we see increased imbrication and shortening above the basal detachment. This is in contrast to regions where the basal detachment is calculated to be weaker (higher calculated fluid pressures) where we see broader structures and more distributed or ductile deformation above the basal detachment.
DE: 8005 Folds and folding
DE: 8020 Mechanics, theory, and modeling
DE: 8104 Continental margins: convergent
DE: 8108 Continental tectonics: compressional
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Tectonophysics [T]
MN: Fall Meeting 2005