The historic river crossing of Lee's Ferry marks an important and heavily debated geologic transition from the steep Grand Canyon downstream to the broader Canyonlands of the central Colorado Plateau upstream. New data from the spectacular suite of river terraces here allow Joel L. Pederson and colleagues to reconstruct the recent geologic history of the Colorado River. Results indicate a strong response to climate drivers that is superimposed upon an overall incision rate of ~350 meters per million years (~35 cm per thousand years). This very well-constrained and surprisingly healthy incision rate is greater than that recorded downstream in Grand Canyon, yet is somewhat slower than rates upstream in the central Colorado Plateau, revealing an overall bull's-eye pattern of rapid incision in the central Colorado Plateau. This pattern does not match recently proposed sources of uplift along the southwestern flank of the plateau. Instead, Pederson and colleagues suggest this incision bull's-eye is primarily set by isostatic rebound from the deep and broad erosion of weak rocks in the central plateau, which is in turn driven by the propagating response to the geologically recent integration of the Colorado River off the plateau in the Grand Canyon region.
Establishment of euxinic conditions in the Holocene Black Sea Sebastian Eckert et al., Mikrobiogeochemie, Institut fr Chemie und Biologie des Meeres (ICBM), Carl von Ossietzky Universitt, Postfach 2503, D-26111 Oldenburg, Germany. Posted online 7 Feb. 2013; http://dx.doi.org/10.1130/G33826.1.
The Black Sea forms the largest ocean basin on Earth, which is completely devoid of oxygen below 150-200 m water depth. About 9,000 years ago -- during the Holocene sea level rise -- Mediterranean seawater spilled into the Black Sea fresh-water
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Geological Society of America