Devonian period, sedimentary rock

The 50 million years of the Devonian Period provided sufficient time for over 11,000 feet of sedimentary rocks to accumulate in the Appalachian Basin this accumulation was controlled by pulses of tectonic uplift to the east. A similar control of a northwestern source area by intermittent tectonic movement is suggested as a source for the upper wedges (B/C) in the Michigan and Illinois Basins. The lower black shales (A) of regional type represent quiescent periods of slow deposition followed by relatively more rapid sedimentation occurring in response to uplift and erosion of source areas and to depositional restrictions caused by rising arches. The total thickness of Devonian shales in either the Michigan or Illinois Basin is less than 1000 feet, so that the sediment volume involved in these two basins is far less than in the Appalachian Basin. Thus there was ample time for... 

U ). Compounds of are deposited with the sediment because they are far less soluble than compounds of UOf. The uranium in ground water is released into solution by chemical weathering of plutonic and volcanic igneous rocks. The fixation of tetravalent uranium in sedimentary rocks of the Beacon Supergroup became possible because land-based plants that evolved during the Devonian Period provided organic matter that was buried with the sediment. 

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