DEPOSITIONAL SYSTEMS ON THE NEW HAMPSHIRE CONTINENTAL SHELF: FORMATION AND CONTROLLING PROCESSES

The continental shelf off northern Massachusetts, New Hampshire and southern Maine is highly complex and is composed of outcropping bedrock, tills, glacial marine sediments, sand and gravel deposits, muddier sediments further offshore, and remnants of glacial features such as eroded drumlins. In order to describe the sedimentologic and stratigraphic characteristics of the Quaternary deposits and assess the origin of major depositional features, ~1750 km of archived geophysical records, ~1200 bottom sediment samples, and 24 vibracores are being reviewed and the results synthesized in GIS environments. Based on initial analyses and previous investigations, several important depositional systems have been identified and are being studied in detail in order to assess their origin and controlling processes. The morphologic features being focused on include: 1) nearshore shoals tentatively identified as abandoned ebb tidal deltas; 2) a major sand wave field near the mouth of the Piscataqua River; 3) offshore sand bodies deposited near the Holocene lowstand; and 4) offshore eroded drumlins. The earlier work indicated several of these sites contain significant sand and gravel deposits. However, little is known concerning their origin. This presentation will discuss the results of the work concerning the major depositional systems and provide assessments of their origin.