In general, the glacial and glaciomarine deposits lie directly upon 

 the bedrock surface, although Kaye (1961) believed that patches of coastal 

 plain sediment may occur locally in the Boston area. Oldale, Uchupi, and 

 Prada (1973) inferred the presence of extensive coastal plain sediments 

 ranging from Cretaceous to early Pleistocene age underlying the western 

 Gulf of Maine and waters off southeast Massachusetts. However, they did 

 not find evidence of such deposits within the study limits. 



The Quaternary deposits of the Boston area vary in thickness from zero 

 to over 200 feet and are thickest in the ancient bedrock valleys. In the 

 upland areas glacial drift is not thick enough in most places to obscure 

 the relief on the bedrock surface. In the Boston Lowland the bedrock 

 surface is largely buried by overlying Quaternary and Holocene sediments; 

 therefore, existing topographic features are mostly of glacial origin or 

 have formed in response to Holocene fluvial and marine processes (LaForge, 

 1932; Upson and Spencer, 1964). At the time of LaForge's comprehensive 

 geologic study of the Boston region, no pre-Wisconsin drift had been 

 identified there. He believed that some of the Pleistocene glaciomarine 

 clays probably predated Wisconsin time. Judson (1949) and Kaye (1961) 

 found drift deposits underlying Boston which they identified with pre- 

 Wisconsin glacial stages--the oldest possibly Nebraskan till. Kaye's 

 stratigraphic section based on an excavation under Boston Commons is 

 summarized in Table 1. Tentative correlation with the Pleistocene stra- 

 tigraphy of Judson (1949) and Upson and Spencer (1964) , is also included 

 in the table. 



Distribution of the surficial Quaternary glacial deposits in the Boston 

 region is mainly in the form of ground and recessional moraines, outwash 

 plains, eskers, and drumlins. Especially noteworthy are the approximately 

 180 drumlins which are concentrated mostly in the Boston Lowland. Eroding 

 drumlins situated along the coast are considered to be important sources of 

 beach and nearshore sediment. These drumlins are composed mostly of un- 

 stratified till; they range up to 1 mile in length and reach up to 150 

 feet above the surrounding terrain. Many of the drumlins abut or surround 

 highs in the bedrock surface (LaForge, 1932). 



Postglacial deposits in the Boston area consist predominantly of 

 alluvium, swamp and marsh deposits, and shoreline features. Because of 

 intensive urban development in the Boston area, landfill has also become 

 a geologically significant deposit. 



d. Pleistocene Geologic History . The record of Pleistocene glacial 

 and interglacial stages in the Boston region is fragmentary; however, 

 there is general agreement that the bulk of glacial deposits in and around 

 Boston is probably of Wisconsin age. Relationships of these deposits to 

 the standard Wisconsin substage chronology are not well known. 



At the onset of the Pleistocene there was a well-developed subaerial 

 topography and drainage pattern carved into the preexisting rocks of the 

 Boston Lowland and adjacent uplands (LaForge, 1932; Upson and Spencer, 

 1964). Presumably pre-Wisconsin continental glaciers overran the region 



