. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography 1456 D. J. P. SWIFT, 76°00' 75° 50" 75° 40" 75° 30' 75°20' 75°10' Fig. 2.—Bathymetry of the inner shelf of southern Virginia with locations for Figs. 5, 6, and 7. From Payne, 1970. Contours in feet. Dots and bars are locations of other figures. Dashed line indicates axis of Virginia Sheif Valley. Vibracores reveal a fine-grained muddy sand; seismic profiles indicate that its stratification tends to be lenticular with prominent chann
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography 1456 D. J. P. SWIFT, 76°00' 75° 50" 75° 40" 75° 30' 75°20' 75°10' Fig. 2.—Bathymetry of the inner shelf of southern Virginia with locations for Figs. 5, 6, and 7. From Payne, 1970. Contours in feet. Dots and bars are locations of other figures. Dashed line indicates axis of Virginia Sheif Valley. Vibracores reveal a fine-grained muddy sand; seismic profiles indicate that its stratification tends to be lenticular with prominent channel- ing. The unit appears to consist of both fluvial and nearshore deposits. The overlying unit (unit C) has a radiocar- bon age ranging from 29,800 ± 800 yr to possibly as young as 20,400 ± 850 yr (Ta- ble 1). Vibracores penetrating this unit reveal laminae and thin beds of muddy sand and sandy mud. Seismic profiles indicate a rela- tively uniform, continuous stratification. The unit appears to represent a regressive near- shore sequence deposited at the end of the mid-Wisconsinan interstadial. The youngest unit (unit D, Fig. 5) is a dis- continuous sheet of fine to coarse-grained sand that is molded into the sand ridge topography seen in Figs. 2 and 3. Locally, in the axis of some troughs, it thins to a few centimeters of shelly gravel overlying unit C (Swift et al., 1971, fig. 9; Shideler et al., 1972, fig. 9). Numerous cores have been collected from this basal gravel by Powers and Kinsman, 1953. They have interpreted it as a product of the liquefaction and size sorting of seafloor sedi- ment by storm waves. However, the regional stratigraphic relationships outlined in this paper suggest that the basal gravel is more reasonably explained as a lag deposit, formed during the erosional retreat of the shoreface (Swift, 1976, p. 265-268). This three-fold stratigraphy may be inter- mittently resolved on the margins of the Vir- ginia Beach Shelf Valley (Shideler et al., 1
Size: 1860px × 1343px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionamericana, booksponsorlyrasismemb
