Single grain heavy mineral provenance of garnet and amphibole in the Surveyor fan and precursor sediments on the Gulf of Alaska abyssal plain - Implications for climate-tectonic interactions in the St. Elias orogen

A shift in heavy mineral composition during the Miocene, predating the onset of glaciation, points to a tectonically-induced change in erosion centers and sediment transport, probably caused by the rise of the St. Elias Mountains. Garnet and amphibole data suggest the Chugach metamorphic complex is the main sediment source, implying input to the Surveyor fan from sources relatively far in the north during the Miocene. Changing provenance signals from the Miocene to Pliocene suggest rising input from the lower grade metamorphic areas at the southern flanks of the orogen, indicating the advance of glaciers to the tidewater line, providing material from this flanking region. Higher input from the Chugach metamorphic complex in all Pleistocene sediments suggests the Northern Hemisphere glaciation at the Plio-Pleistocene boundary caused erosion and sediment yield from the interior of the orogen. Climatic changes at the mid-Pleistocene transition did not cause significant changes in the provenance signal.