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The AAPG/Datapages Combined Publications Database

Journal of Sedimentary Research (SEPM)

Abstract


Journal of Sedimentary Petrology
Vol. 42 (1972)No. 2. (June), Pages 425-433

Roundness-Mineralogical Relations of Some Intertidal Sands

R. J. Balazs (2), George DeVries Klein

ABSTRACT

Medium to coarse-grained arkosic sands on an intertidal sand body in the Minas Basin, Bay of Fundy, Nova Scotia, show texturally supermature rounding. Average roundness is 0.49; eighty-six percent of all quartz grains are characterized by rounding in excess of 0.35. Quartz sand not only shows higher values of roundness (mean of 0.53) than associated orthoclase, plagioclase and recognizable rock fragments, but also shows a decrease in roundness with decreasing particle size. These intertidal sands are characterized also by higher values of roundness than their parent material (Triassic sandstone and basalt, and Pleistocene fluvioglacial drift).

The higher degree of roundness of the intertidal sands is attributed to predicted high rates of grain collission known to occur during bedload transport by tidal currents. Intertidal sand bodies are characterized by equilibrium sand transport patterns through alternating flood-dominated and ebb-dominated portions of the sand body. As a consequence, a long distance of grain transport is predicted within a limited geographic area in response to such a transport mode. This limited geographic area may be located close to source terrains. High values of roundness therefore are a consequence of prolonged abrasion on such sand bodies.

In comparison to known values of fluvial, beach, inland dune and coastal dune sands, intertidal sands are characterized by higher roundness values. High roundness values, associated with other sedimentary features, may indicate a similar transport history.


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