Topographic effects of the Eastern California Shear Zone in the Mojave Desert

Abstract

Abstract. Digital elevation data were used to evaluate the topographic implications of the late Neogene Eastern California Shear Zone (ECSZ). Analysis shows that the ECSZ has directly affected >18% of the surface of the Mojave Desert block (MDB); uncertainties regarding the distribution of strain in basins suggest that the area of effect may be larger by perhaps a factor of 2. Remaining areas are likely due to Quaternary erosion or are inherited from pre-ECSZ times. Major drainages and basins of the MDB are developed along transtensional depressions within the ECSZ. These depressions established the regional and local base levels that have governed erosion by running water. Local topography is closely tied to the style of strain. Highlands of the MDB are spatially associated with (1) areas that have or are currently undergoing contractional strain associated with transpression within the ECSZ and (2) areas that lie adjacent to uplifted transpressional belts that bound the Mojave Desert (San Bernardino and San Gabriel Mountains). In contrast, lowland areas are spatially associated only with transtensional areas within the ECSZ. Examination of the topography in the transtensional areas also reveals two, distinct populations of elevation. Spatial analysis indicates that areas that have undergone the greatest local transtension associated with dextral shear are also the lowest topographically. These areas formed during the earliest phase of movement of the ECSZ (late Miocene to early Pleistocene). The second population is coextensive with recently formed transtensional basins that continue to be active.

Stateline fault system: A new component of the Miocene-Quaternary Eastern California shear zone

“…1B and 1C). Because no equivalent active structures are described in the region immediately northeast of the SFS, and because geodetic motions throughout this region are stable at the limit of detection (~0.2 mm/yr level; Bennett et al 2003), we interpret the SFS as the northeasternmost component of the Eastern California shear zone between latitudes 35° N and 37° N. It has received little attention by workers focusing on understanding the long-and short-term strain distribution in the shear zone (Bos, 2005;Dixon et al, 2003;Dixon et al, 1995;Dokka and Macaluso, 2001;Oldow, 2003), in part because, unlike other major dextral faults across this region, most of its trace is developed in poorly consolidated, late Quaternary lacustrine deposits and is therefore obscured by late Holocene erosion. We partition its trace into three primary segments separated by contractional (left) step-overs, which, from south to north, include the Mesquite, Pahrump, and Amargosa segments (Fig.…”

Can compliant fault zones be used to measure absolute stresses in the upper crust?

“…subsidence) due to CZ softening (Figures 11b and 11d). Transtension has been suggested for this region [e.g., Dokka et al , 1998; Dokka and Macaluso , 2001].…”

“…The coefficient of static friction, μ , is not known (though it is suspected to be greater than for major plate‐bounding faults [ Townend and Zoback , 2004]). Parts of the Mojave may be experiencing transtension [ Dokka et al , 1998; Dokka and Macaluso , 2001] while in other areas (i.e. the Mojave block), transpression may be dominant [ Bartley et al , 1990].…”

Precipitation trapped in datable rock-forming minerals: estimating Antarctic palaeoelevations - a discussion

“…The Antarctic Peninsula (AP), the Ellsworth Mountains (EWM) and the Transantarctic Mountains (TAM) form modern high elevation mountain ranges reaching ~2000 m in the AP, 5000 m in the EWM and ~4000 m in the TAM providing extensive snow and ice free rock outcrops. During the Mesozoic and the Cenozoic, faulting and/or shearing accompanied uplift of these three mountainous regions, making them potential very-high altitude areas propitious for the study of δD values from meteoric water trapped in rock-forming minerals for palaeoelevation reconstructions (large-scale shearing is known to be a prominent driving force for rapid mountain building and uplift to high elevations in all parts of the world and in all geological times, (England & Thomson 1984, England & Searl 1986, Molnar et al 1993, Wittlinger et al 1998, Cowgill et al 2000, Dokka & Macaluso 2001).…”