Strain variation in thrust sheets across the sevier fold-and-thrust belt (Idaho-Utah-Wyoming): implications for section restoration and wedge taper evolution

Spatial and Temporal Variation in Penetrative Strain During Compression: Insights From Analog Models

“…The strain axes for the accumulated penetrative strain were found to be a reasonable approximation to the incremental strain axes, however (Tapp and Wickham, 1987). The amount of penetrative strain accommodated in a given region is also affected by variations in lithology of the overburden, the presence and specific rheology of any detachment layers, and the dip of the base of the deforming wedge, as well as the relative location within the orogen (Mitra, 1994;Whitaker and Bartholomew, 1999;Couzens-Schultz et al, 2003;Koyi and Vendeville, 2003;Sans et al, 2003;Koyi et al, 2004;Nilforoushan and Koyi, 2007;Weil and Yonkee, 2009). Penetrative strain features can be found up to 1200 km from the active plate margin (Craddock and van der Pluijm, 1989).…”

“…Mitra (1994) showed that the internal strain within thrust sheets is inhomogeneous, increasing from the front to the back of the thrust sheet, and it is independent of the translation of the sheet. Mitra (1994) further showed that internal strains in the frontal thrust sheets are smaller than the internal strains in the hinterland thrust sheets. Typically, the development of penetrative strain-related features is considered to be a process that occurs early in the deformation process, before the development of macroscale structures (e.g., Geiser and Engelder, 1983;Mitra and Yonkee, 1985;Wiltschko et al, 1985;Henderson et al, 1986;Dean et al, 1988;Tavarnelli, 1997;Whitaker and Bartholomew, 1999;Weil and Yonkee, 2009), sometimes with a relationship to the developing thrust ramp (Fischer and Coward, 1982).…”

“…Measured amounts of penetrative strain range from 2% to 30%, where the larger end of this range may form a significant component of the total shortening (Engelder and Engelder, 1977;Engelder, 1979;Mitra and Yonkee, 1985;Wiltschko et al, 1985;Craddock and van der Pluijm, 1989;Mitra, 1994;Whitaker and Bartholomew, 1999;Sans et al, 2003;Koyi et al, 2004;Weil and Yonkee, 2009). Penetrative strain amount appears to decay away from the developing thrust front (Craddock and van der Pluijm, 1989;Koyi, 1995).…”

“…The amount of penetrative strain is variable in time and space (e.g., Beutner and Charles, 1985;Groshong and Epard, 1994;Mitra, 1994;Epard and Groshong, 1995;Koyi, 1995;Weil and Yonkee, 2009). Mitra (1994) showed that the internal strain within thrust sheets is inhomogeneous, increasing from the front to the back of the thrust sheet, and it is independent of the translation of the sheet. Mitra (1994) further showed that internal strains in the frontal thrust sheets are smaller than the internal strains in the hinterland thrust sheets.…”

“…Deformation of a thrust sheet can be described in terms of a bulk translation, a bulk rotation, and an amount of internal strain (e.g., Mitra, 1994;Yonkee and Weil, 2010;Sussman et al, 2012). An underestimate of any of these components leads to an underestimate of the total shortening.…”