PLEISTOCENE-HOLOCENE SEDIMENTS INTERPRETED 

 BY SEISMIC REFRACTION AND WASH-^BORE SAMPLING, 

 PLUM IS LAND -CASTLE NECK, MASSACHUSETTS 



by 



Eugene G. Rhodes 



I . INTRODUCTION 



The shoreline of northeastern Massachusetts is dominated by exten- 

 sive barrier beaches. This study attempts to reconstruct the three- 

 dimensional stratigraphic framework of these deposits. The Pleistocene 

 and Holocene stratigraphy of Castle Neck and the southern third of Plum 

 Island, the two largest barrier beaches in this area (Figure 1), was 

 determined by wash-bore and seismic refraction methods. 



Thoreau vividly described this part of the New England coast in the 

 1840's: 



"It is a mere sandbar exposed, stretching nine miles parallel 

 to the coast, and, exclusive of the marsh on the inside, rare- 

 ly more than half a mile wide. ...The island for its whole 

 length is scalloped into low hills, not more than twenty feet 

 high, by the wind, and excepting a faint trail on the edge of 

 the marsh, is as trackless as Sahara. ...I have walked down 

 the whole length of its broad beach at low tide, at which time 

 alone you can find a firm ground to walk on, and probably 

 Massachusetts does not furnish a more grand and dreary walk. 

 ...A solitary stake stuck up, or a sharper sand hill than 

 usual, is remarkable as a landmark for miles; while for music 

 you can hear only the ceaseless sound of the surf, and the 

 dreary peep of the beach birds." 



from Henry David Thoreau, A Week on the Concord and Merrimack 

 Rivers . 



The 3-mile expanse of dunes and beach south of Plum Island, which 

 comprises Castle Neck, could also have been the object of Thoreau 's 

 description. Much of Plum Island is now controlled by the Parker River 

 Wildlife Refuge. Castle Neck is a recreation area held by the Trustees 

 of Reservations, Milford, Mass. Both areas have been subjected to agri- 

 culture and other manmade modifications since colonial times. Yet, today 

 they are two of the least disturbed sand bodies on the New England coast. 



Much of Plum Island and most of Castle Neck have been allowed to 

 undergo uninterrupted natural modifications in response to the environ- 

 ment. For this reason the area provides an excellent outdoor laboratory 

 for this type of project. 



