Glenn R. Sharman and colleagues present a synthesis of new and existing radiometric ages of individual sand grains (zircon) from sandstone that was deposited between 100 and 40 million years ago in ocean basins along the western margin of North America (Oregon, California, and Baja California). Their study shows how the source of the sand changed over time in response to plate tectonics. In particular, an episode of low-angle plate subduction and associated oceanic plateau collision with southern California had a major influence on how landscapes evolved along the western margin of North America. For example, Sharman et al. show that rivers that emptied into the paleo-Pacific ocean migrated eastward over time in response to a redistribution of topography along the margin following oceanic plate collision.
Timing and significance of gabbro emplacement within two distinct plutonic domains of the Peninsular Ranges batholith, southern and Baja California
D.L. Kimbrough et al., Dept. of Geological Sciences, San Diego State University, San Diego, California 92182-1020, USA. Published online on 30 July 2014; http://dx.doi.org/10.1130/B30914.1.
Evaluating the crucial role postulated for mantle-derived mafic magmas in the formation of Cordilleran continental batholiths requires well-determined igneous crystallization ages from gabbro intrusions as well as petrologic data reflecting possible mantle source heterogeneities and/or variations in subcrustal processes. This paper by David L. Kimbrough and colleagues establishes the chronological framework for gabbro emplacement in one of the best known Cordilleran batholith of the Americas, the Peninsular Ranges batholith southern and Baja California, and thereby contributes to fundamental questions related to the formation of continental crust.
Three-dimensional (3-D) finite strain at the central A
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Geological Society of America