Fig 5 - uploaded by Walter A. Barnhardt
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Shaded-relief bathymetric map overlain with contours of buried R1 surface (same area as Fig. 2). Depths to the R1 surface are based on a velocity of 1,500 m/s in both water and sediment
Source publication
High-resolution, seismic-reflection data elucidate the late Quaternary development of the largest coral-reef complex in the
main Hawaiian Islands. Six acoustic facies were identified from reflection characteristics and lithosome geometry. An extensive,
buried platform with uniformly low relief was traced beneath fore-reef and marginal shelf environ...
Citations
composition of sand grains from the beaches, reef flat, and fore reef of south Molokai, Hawaii, provides key information about the origin and transport history of sediment on the reef and adjacent beach. The most common grain types include coralline algae, coral, chemically altered carbonate, and siliciclastic grains. Minor components include algal plates (Halimeda), mollusk fragments, and foraminifera; in selected areas, these components are abundant. Similarities in composition indicate that sand grains are freely transported between the beach and the reef-flat environments, whereas the fore reef has limited exchange of sand with either the beach or the reef flat. Overall, the calcium carbonate fraction of the sand, silt, and clay increases with distance offshore from 400 to 650 in, where the percentages plateau and remain relatively stable across the fore reef. The calcium carbonate content of bottom sediment indicates that sand transport on the reef flat is generally shore parallel with little shore-normal movement. This study has implications for management of beaches and coastal resources along fringing coral reefs in that it documents the effectiveness of the wide reef flat and reef crest in blocking sand transport with the fore reef. It also indicates that sediment introduced to the inner reef flat is not quickly dispersed seaward and therefore has a relatively high residence time in that setting.
