Although provenance plays a fundamental role in establishing
sandstone mineralogy, transport processes impact the sediment as well. To
explore the potential utility of transport-associated microtextures, Sweet and Brannan
analyze the abundance of glacially and fluvially induced microtextures to
assess the role of fluvial overprint on glacially modified grains along ~188 km
of the proglacial Chitina River, SE Alaska.
The
analysis of SEM observations documents the relative proportions of glacially
induced stylus microtextures (i.e., grooves, troughs, and gouges) and fluvial
percussion-induced microtextures (i.e., v-shaped cracks and edge rounding) on
quartz grain surfaces, and compares how this ratio changes with distance
downstream. The results indicate that the glacially induced microtextures input
to the river persist downstream, but are modified progressively by traction and
saltation. This type of analysis could
be applied to ancient fluvial strata provide insights to 1) differentiate
between proglacial and nonglacial braided rivers and 2) reconstruct proglacial
paleogeography from ancient strata. Furthermore, the results clearly show that
it makes a difference how you roll.
Proportion of glacially to fluvially induced quartz grain microtextures along the Chitina River, SE Alaska, U.S.A. by Dustin E. Sweet and David K. Brannan
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