” * ‘ F, < cores vce ot . ; thea tht e . ; : a ee cate Oe ae ih Ree as ane Nga ite Saini alae A net dad 7375 years (4). Cores of the sea floor in the Gulf of Mexico off Texas include a transgressive salt-marsh and freshwater peat whose seaward limit at about 25 m has been dated by radio- Reports carbon at 10,200 years (5). Dates for many freshwater peats encountered in borings of the Mississippi Delta have been reported (6). Bridge borings off western Australia penetrated fresh- water peat, at 21 m, having an age of 9850 years (7), Other bridge borings Freshwater Peat on the Continental Shelf Abstract. Freshwater peats from the continental shelf off northeastern United States contain the same general pollen sequence as peats from ponds that are above sea level and that are of comparable radiocarbon ages. These peats indicate that during glacial times of low sea level terrestrial vegetation covered the region that is now the continental shelf in an unbroken extension from the adjacent land areas to the north and west. Evidence of sea levels lower than the present level has long been pro- vided by submerged intertidal or shallow-water topography, sediments, fauna, one that is related to the low sea levels is deeply submerged peat, especially that of freshwater bogs. These deep deposits are much older than the well- and flora. So many examples of these features are known throughout the known peat and tree stumps that are the continental shelves that they must denote eustatic changes of sea level rope. One is Dogger Bank in the English Channel (/), where a sample from 39 m has been dated, by the radiocarbon method, as 9300 years old (2); another ts in the Baltic Sea (3), where a deposit at 35 to 37 m dates from world in the narrow depth range of recent enough to have been associated with Pleistocene glaciation. One of the most interesting sedi- ments on the continental shelf and common just beyond the shoreline. The longest-known examples are off Eu- off British Guiana reached freshwater peat, which had an age of 8590 years. at 20 m (8). Freshwater peat cored in Malacca Strait, off Malaya, at a depth of 27 m has been dated at 10,000 years (9); similar peats containing the bivalve Cyclina have been dredged from 50 to 80 m in Naruto Strait, an entrance to the Inland Sea of Japan, and others containing large palm trees have been observed in Toyama Bay, Japan (0). Submerged soils rich in organic debris, and about 12,000 years old, have also been cored off Nigeria (71) and elsewhere. Hence, freshwater, as well as salt-marsh, peats are widely distributed on the continental shelves of the world. In 1964 a large mass of peat was recovered by Captain Norman Lepire . fiPorttand) ~——s 199 KM TEa iar 7 “ee Q* Fig. 1. Positions of peat samples (closed circles) and of near-intertidal oyster shells (open circles} on the continental shelf and in coastal areas from New England south to Cape Hatteras. Sources of data are listed in Teble 1; contours te in Meiers. Cross- hatching denotes the area of the more detailed Fig. ?. oe NTT anrD s4act 1301