Abstract

Fourier analysis of quartz grain shapes across the shelf and adjacent beach-littoral system distinguished: a beach-littoral zone, an inner zone (inner shelf), and an outer zone (mid and outer shelf). The basis is the proportion of type 1 (abraded) and type 2 (irregular) sand present. The inner shelf averages 45 percent type 2 sands (similar to the beach sands). The outer zone (mid and outer shelf) contains the lowest proportions (averaging 15%) of type 2 sand, suggesting a multicycle abrasion history. The boundary between the inner and outer zones is sharp and may represent the seaward limit of dominantly glaciofluvial sediment. The beach-littoral zone off eastern Long Island has the widest variation in relative proportions of shape types (35-95% type 2 sand). Within this zone two sources are indicated: the partially abraded sands (50% type 2 associated with the beach), and highly irregular glaciofluvial sands (95% type 2) of glaciofluvial substrate underlying the beach facies. The crest of the longshore bar contains samples containing a wide range in proportions of these sand types, implying episodes of both seaward transport onto the bar crest as well as landward transport from a glaciofluvial substrate exposed just seaward of the beach-littoral bar.--Modified journal abstract.

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