linkedin post 2019-01-19 05:59:50

TECTONICS. “Before the plate tectonic revolution, the missing sediments from Walcott’s “Lipalian interval” were generally expected to reside in the ocean basins; their absence, along with the young age of the ocean crust, was considered a significant point of evidence in favor of seafloor spreading and plate tectonics. In a plate tectonic model, much sediment accumulated on the oceanic crust is consumed by subduction—presently at a rate of about 1.65 km3/y. Due to its low density and fusibility, however, subducted sediment in the mantle wedge is often incorporated into new arc magmas; consequently, a chemical or isotopic signature of subducted sediment (if sufficiently voluminous) may be preserved within the igneous record.”

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