The sculpting of the Earth's surface by the processes of erosion generates particulate sediment that is transported into regions of subsidence, where it accumulates over long periods of time. Nikolas Michael and colleagues constrain the rates of erosion, transport and deposition of a system where the source regions of sediment can be confidently connected to depositional sinks. They present new results from a geological example, about 40 million years old, on the southern flank of the Pyrenean mountain chain in northern Spain. Understanding the budget of sediment from source regions to depositional sinks helps geologists to make predictions of the architecture of sedimentary rocks and of the variation in size of the sediment grains -- key factors in the exploitation of oil, gas, water and mineral resources from beneath Earth's surface.
Facies architecture of a continental, below-wave-base volcaniclastic basin: The Ohanapecosh Formation, Ancestral Cascades arc (Washington, USA)
Martin Jutzeler et al., Centre of Excellence in Ore Deposits, School of Earth Sciences, University of Tasmania, Private Bag 79, Hobart TAS 7001, Australia. Posted online ahead of print on 3 Feb. 2014; http://dx.doi.org/10.1130/B30763.1.
The Ohanapecosh Formation (32-26 million years old) consists of voluminous volcaniclastic facies that were deposited in the Ancestral Cascades, in Washington State, USA. Absence of shoreline-related facies suggests accumulation in a deep continental basin. Various volcanic sources, mostly andesitic and basaltic, are at the origin of the formation. The thickest beds are derived from entrance of pyr
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