. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography BED FORMS 171. 15 20 25 30 35 40 M«an flow velocity (cm/sec) FIGURE 12. The mean transverse spacing of parting lineations as a junction of mean flow velocity and flow depth. From Allen (1970). dreds of meters (Allen, 1968a). They are best observed by means of sidescan sonar (Figs. 13 and 14). The large- scale patterns are characteristic of shelves with strong tidal flows (Kenyon, 1970); see Fig. 15. Sand ribbons and longitudinal furrows are probably
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography BED FORMS 171. 15 20 25 30 35 40 M«an flow velocity (cm/sec) FIGURE 12. The mean transverse spacing of parting lineations as a junction of mean flow velocity and flow depth. From Allen (1970). dreds of meters (Allen, 1968a). They are best observed by means of sidescan sonar (Figs. 13 and 14). The large- scale patterns are characteristic of shelves with strong tidal flows (Kenyon, 1970); see Fig. 15. Sand ribbons and longitudinal furrows are probably the most common mesoscale bed form on the continental shelf, being widely distributed on both shelves dominated by tidal flows (Kenyon, 1970; Belderson et al., 1972) and storm-domi- nated shelves (Newton et al., 1973; McKinney et al., 1974); see Fig. 14. Unpublished data of the Atlantic Oceanographic and Meteorological Laboratories, Mi- ami, Florida, show them to be characteristic of large sectors of the Middle Atlantic Bight. Relief is negligible relative to width. Kenyon would restrict the term "sand ribbon" to features having length-to-width ratios of 1 :40 and refers to shorter, broader features as elongate sand patches, but the distinction seems arbitrary. Unlike parting lineation ridges, sand ribbons tend to consist of streamers of finer sand in transit over a coarser substrate which may, in fact, be a gravel. A continuum may exist between a sand ribbon pattern of sand and gravel streets of equal width, to a "longitudinal furrow" pattern (Stride et al., 1972; Newton et al., 1973) in which widely spaced, elongate erosional windows in a thin sand sheet reveal a coarser substrate. Ribbon width relative to the width of the interribbon zone does not appear to be simply a function of the height of a sinus- oidal surface of sand layer over a coarser substrate, since the windows in profile are notchlike affairs separated by flat plateaulike zones (Fig. 16).
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