crease near the bottom of the water column. 

 The thickness of this turbid layer was mapped 

 (fig. 5). It was thickest over the deepest part 

 of the depression between Herald Shoal and 

 the mainland. Although turbid water was pres- 

 ent over much of the inshore area shallower 

 than 30 meters, the distinct layering found in 

 deeper water was absent. 



Sediments 



Sediments ranged from muddy gravels to 

 well-sorted sands (fig. 6). Particle-size de- 

 terminations showed the following six types of 

 deposits in a distribution similar to that re- 

 ported by McManus and others (1969) : 



1. Moderately to well-sorted sand, distri- 

 buted to 90 km from Point Lay and 

 farther off'shore at the northern end of 

 the trough between Herald Shoal and the 

 mainland. 



2. Silt and clay (mud) along the eastern 

 side of the offshore depression. 



3. Muddy gravel on the east flank of Herald 

 Shoal. 



4. Sandy gravel north and east of Cape 

 Lisburne. The gravel fraction consisted 

 largely of clasts with very angular and 

 fragile shapes and pebbles of uniform 

 lithology, all of which indicate minimal 

 waterborne transport and mixing. 



5. Admixtures of items 1 through 4. 



6. Sand and gravel on the modem beach 

 almost devoid of fine material. Well- 

 rounded pebbles were randomly distri- 

 buted in all sediment types. 



The occurrence of offshore gravel cannot be 

 accounted for by modern processes. The fragile 

 shapes and angularity of individual clasts, and 

 the uniform lithologies of the gravel samples, 

 indicate only minimal transport from the 

 source areas and may indicate proximity to 

 sea-floor outcrops (McManus and others, 

 1969). 



Studies of subsurface sedimentary features 

 and the use of radiographic techniques showed 

 intensive bioturbation (fig. 7). Numerous 

 worm tubes, burrows, and even individual 

 worms were found during sectioning and ex- 

 amination (fig. 8). Other sediment-disrupting 

 organisms encountered included echinoids, 

 mollusks, gastropods, and walrus. The radio- 



graphs also show that rounded pebbles were 

 randomly distributed. 



Coastal Observations 



Some coastal observations which relate to 

 the problem of sediment supply and transport 

 along the shore were made on the barrier island 

 near Point Lay. During October, the seaward 

 beaches of the barrier island at Point Lay con- 

 sisted of a series of small (0.1 to 1 meter) 

 asymmetrical ice-gravel ridges. These appear 

 to have formed since the onset of winter by 

 freezing at higher stands of the sea (fig. 9). 

 For a distance of 1 km from the northern tip 

 of the barrier island, a series of larger (1-3 

 meters) more symmetrical ridges occurred at 

 higher elevation (figs. 9 and 10). These ap- 

 parently mark former locations of the lagoonal 

 opening and suggest a northward migration of 

 sediments along the barrier island. Five 

 samples from this island consist of a mixture 

 of sand and gravel (fig. 6). 



Sediment Transport Regime 



Current directions, orientation of ripples 

 northeast of Cape Lisburne, and the apparent 

 displacement of a turbid layer eastward toward 

 Point Lay suggest a clockwise eddy in the near- 

 bottom water: circulation similar to that de- 

 scribed by Fleming and Heggarty (1966). 

 There is, however, apparently little deposition 

 from the eddy, as the sandy bottom landward 

 of the 40-meter contour does not show any 

 increase in silt and clay content under the dis- 

 placed turbid layer. 



The turbid layer is thickest in the north- 

 western part of the study area, where water 

 from the Bering Strait was found at depth 

 (Ingham and Rutland, this Oceanographic Re- 

 port) . In studies of particle transport through 

 the Bering Strait, 125 miles to the south, 

 McManus and Smyth (1970) found high 

 turbidity and relatively high concentrations of 

 particulate matter throughout the water col- 

 umn. These data suggest that much of the 

 suspended matter in the area could be derived 

 from south of the Bering Strait. 



When near-bottom current directions are 

 superimposed on a profile of turbidity along a 

 line between Cape Lisburne and Herald Shoal 

 (fig. 11), northward vectors correlate with the 

 most pronounced zone of turbid water along 



89 



