http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
kinematics and deformation of a thrust sheet over frontal-transverse ramps
Map-view curves in thrust-fault traces are common in fold-and-thrust belts. Frontal-transverse-frontal ramp geometries are typically the reason. However, not all curves in thrust-fault traces can be related directly to such footwall ramps. Possible end-member mechanisms that can explain curves in fault traces may include: (1) erosional retreat of the trace of a structurally higher thrust sheet on the margins of a footwall culmination, (2) differential displacement along strike, and (3) propagation of thrust faults around footwall obstacles. Both the spatial extent of the transverse structures and the distribution of strain within thrust sheets produced by each of the above mechanisms will be different. Characterization of a typical curve in a thrust trace was carried out in the Miaoli-Cholan area of the western Taiwan Foothills belt. The Sani thrust shows an array of frontal-transverse ramps with an average 20° dip. The emplacement of the Sani thrust sheet was in part impeded by synchronous uplift of the footwall Chuhuangkeng anticline. As a result, the curved Sani thrust may be attributable to both along-strike differential displacement and erosion. High maximum shortening strains (10%) recorded by calcite twin lamellae in the restrained portion of the Sani thrust sheet further support this hypothesis. Clay model experiments were performed to, (1) investigate the role of three-dimensional footwall geometry on hanging-wall deformation and, (2) complement field observations and theoretical analyses. Two model configurations were used to simulate footwall-buttress and curved-origin models. Results of clay models indicate that both deformation style and degree of deformation are dependent upon ramp dip and the amount of displacement. Subtle variations in experimental conditions (such as displacement rate), and in footwall geometry (such as sharpness of ramp intersections, the length and attitude of the transverse ramp) significantly change the distribution and quantity of, and displacement on, deformation features seen in map view. Localized deformation features such as oblique normal faults, simple shear in the plane of detachment and deflections of displacement paths indicate that non-transport-parallel strains can occur near a transverse ramp.
Contains two folded maps in back pocket.