June GEOSPHERE media highlights( Boulder CO USA The June issue of GE...)

Boulder, CO, USA The June issue of GEOSPHERE, published by the Geological Society of America, is now available online. Topics of interest include common ground in the disagreement between mantle plume and lithospheric mantlelower crust delamination models; a USGS Great Basin Paleontological Database filled with 150 years of fossil data; laser rangefinders versus terrestrial laser scanners and digital cameras in three-dimensional modeling; and contaminant sources of northern Mexico's Rio Conchos, including the effects of human activities.

A plume-triggered delamination origin for the Columbia River Basalt Group

Victor E. Camp, Dept. of Geological Sciences, San Diego State University, 5500 Campanile Drive, San Diego, California 92182-1020, USA; and Barry B. Hanan.

Continental flood-basalt provinces are the source of a vigorous ongoing debate in the geological sciences. The traditional model to explain these vast outpourings of basaltic lava is to attribute their origin to the rapid melting of large plumes derived from the Earth's deep mantle. The efficacy of this model has been questioned recently by nonplume advocates, many of whom prefer to attach the origin of these provinces to a model of delamination of the Earth's lithospheric mantle and lower crust. The two models, however, are not mutually exclusive. Here, we describe a model of plume-triggered delamination for the origin of the Columbia River Basalt Group, the youngest, best preserved, and mostly intensely studied flood-basalt province on Earth. We demonstrate that such a model satisfies primary constraints on source melting, generating a chronological sequence of melting events consistent with the stratigraphic record of chemical change through time. The tectonic environment of melting is similar to that of recent numerical models that generate a cross-section of surface uplift and deformation that is identical to that in the Columbia River Basalt Group sou
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