Footwall topographic development during continental extension

Abstract

[1] We examine the progressive development of footwall topography associated with a set of active normal faults in the northeastern Basin and Range Province of the western United States. Fault length and displacement increase monotonically from northeast to southwest in the study area, allowing us to track both variations in footwall morphology with increasing displacement and along-strike changes in morphology on a single fault. We show that patterns of catchment area, footwall relief, and catchment outlet spacing vary predictably and are related to the growth of the range-bounding normal fault array. In this semiarid region, full parsing of footwall drainage area and removal of antecedent topography do not occur until fault arrays grow beyond two crustal-scale segments. Multiple-segment faults with lengths of up to 150 km have footwall relief that is limited to $1000 m in the center of the footwall and that decays to zero at the fault tips over a length scale of $15 km. We hypothesize that this relatively uniform footwall relief is erosionally limited and reflects the efficacy of surface processes in removing footwall material in the center of the footwall. If the fault array grows by relatively steady propagation of the tips, we suggest that the 15 km length scale required to reach uniform relief is related to a timescale of relief generation by the fault tip propagation rate. While such propagation rates are poorly known, an average rate of 10 mm yr À1 would imply footwall relief generation over a timescale of $1 Myr.

Small valley glaciers and the effectiveness of the glacial buzzsaw in the northern Basin and Range, USA

“…Fault initiation and uplift occurred at~6 Ma for the Lost River, Lemhi, and Beaverhead faults, and each range-front fault is divided along-strike into six fault segments (Densmore et al, 2005). In a series of studies Densmore et al (2004Densmore et al ( , 2005Densmore et al ( , 2007 investigated relationships between fault development and footwall topography in each range, and concluded that, away from the developing southern fault tips, footwall relief remains relatively constant and is limited by colluvial processes on steep threshold hillslopes.…”

Gravitational slope deformation, not neotectonics: Revisiting the Nordmannvikdalen feature of northern Norway

“…Normal faults (and in Kåfjord, many gravitationally failing rock hillsides; see Henderson et al, 2011) exhibit a distinctive and diagnostic morphology (e.g., Dawers et al, 1993;Destro, 1995;Burbank & Anderson, 2001;Densmore et al, 2004). They have no scarp at the tip (the point past which surface rupture has not propagated) and rise to a maximum scarp height near the midpoint of the ruptured segment.…”

Some remarks on the earthquakes of Fennoscandia: A conceptual seismological model drawn from the perspective of hyperextension

“…2) to the Scandinavian onshore topographic envelope along 234 profiles oriented parallel to the direction of tectonic transport and confirmed the correlation between crustal thinning and rifted margin escarpment elevation for Scandinavia. They also documented the geometric relationships between crustal taper and hinterland river drainages, proximal domain brittle fault fabrics, and juxtaposed landscapes that are predicted by the simple principles of tectonic geomorphology (e.g., Leeder & Gawthorpe, 1987;Leeder & Jackson, 1993;Gawthorpe & Leeder, 2000;Burbank & Anderson, 2001;Densmore et al, 2004). Redfield & Osmundsen (2013) suggested that footwall uplift, driven by erosion and deposition and governed by the thinning gradient, was responsible for much of Scandinavia's Cenozoic topographic rejuvenation.…”