September Geology and GSA Today media ...( Boulder CO USA - GEOLOGY topics reac...)

Boulder, CO, USA - GEOLOGY topics reach deep into Earth and far into spacefrom magma and plate tectonics to cosmic dust and asteroidsand touch on the intricate details of our planet, including a 1200-year record of corals and coral reef health and the wealth of climate change information found in both bat guano and Chinese loess. The GSA TODAY article studies the end-Permian mass extinction in the marine realm, examining long-term environmental stress and recovery.

Ups and downs of the Mississippi Delta

Michael Blum et al., Dept. of Geology and Geophysics, E235 Howe-Russell Geosciences Complex, Louisiana State University, Baton Rouge, Louisiana 70803, USA. Pages 675-678. NSF funding received.

Blum et al.'s recent research suggests the Mississippi delta has a complex history of vertical motion that reflects the response of Earth's crust to large-scale erosion during the ice age and deposition during more recent times. Erosion of the lower Mississippi valley and delta region during the last ice age removed a large mass of sedimentthis would have resulted in large-scale uplift of the delta region and adjacent Gulf of Mexico shorelinewhereas deposition during the last few thousand years has resulted in replacement of that mass and in large-scale subsidence. The subsidence part of this cycle is ongoing and contributes to the modern-day land surface subsidence problem in the delta region. Recognition of this cyclical pattern of uplift and subsidence has a number of implications for understanding coastal evolution and sea-level change, as well as the evolution of large delta systems elsewhere.

Mantle upwelling, magmatic differentiation, and the meaning of axial depth at fast-spreading ridges

Douglas Toomey and Emilie Hooft, 1272 Geological Sciences, University of Oregon, Eugene, Oregon 97403-1272, USA. Pages 679-682. NSF funding received.

Since the first systematic mapping of the
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