rOSSILIFEROUS MARINE CLAYS 543 



ferences in elevation and topography from the low-level clays. Along the 

 coast, the latter, at Lynn and Salem in Massachusetts, Portsmouth and 

 Dover in New Hampshire, and at Eliot, York, Saco, Portland, Brunswick, 

 Eockland, Bluehill, Milbridge, Addison, and Lubec in Maine, consist of 

 broad clay plains of elevations ranging from 20 to 80 feet above tide. 

 These plains are commonly but slightly eroded and their upper surfaces 

 have a very "recent looking" topography. Sometimes the clay is over^ciiri 

 by stratified sand, but no till and but very little gravel is found on it. 

 TJiese plains are l}elieved to be of late Wisconsin age. 



One of the strUfing features noticeable regarding the clays in general, 

 however, is the great range in their maximum elevation at different locali- 

 ties. Along the greater part of the Maine coast and in the Kennebec, 

 Penobscot, and other large valleys they present striking differences in 

 elevation. At Boston this level is but a few feet above tide; at Saugus 

 and Danvers, Massachusetts, it is 60 feet; at Ipswich not over 60 feet; at 

 Amesbury and Haverhill, in the Merrimac valley, 70 to 80 feet; at 

 Exeter, New Hampshire, 100 feet; at jSTorth Berwick, Maine, 120 feet; at 

 Westbrook, 150 feet; at North Yarmouth and Gray, 180 feet; at Lisbon 

 and Lewiston, in the Androscoggin valley, 200 feet; at Gardiner, in the 

 Kennebec vallej^, 200 feet. Thus, from Boston to the Kennebec, there is 

 a fairly uniform rise toward the northeast. 



In the Kennebec valley the clays can be traced, with short breaks, from 

 less than 100 feet above tide at Bowdoinham to 200 feet at Gardiner, 220 

 feet south of Augusta, 320 feet west of Augusta, 200 feet at Vassalboro, 

 and 180 feet at Waterville. As far up the valley as Skowhegan marine 

 fossils were found by Jackson and Packard. Beyond there the clays oceur 

 up to 200 feet at Forridgewock, 300 feet at Madison, and 380 feet 

 north of Solon; but these may be in part of fluvial or glacio-fluvial 

 origin. The apparent rise inland was at first thought to be significant 

 and to corroborate a recent differential elevation of the interior relative 

 to the coastal regions, a theory which was first postulated by De Geer 

 in 1892* and which was indicated by the 500-foot elevations of the 

 "Leda clay" in the Saint Ijawrence valley. 



Abundant observations, however, showed that the highest elevations 

 occiir most abundantly in regions more or less protected from erosion, and 

 nevertheless are more eroded than the exposed clays along the coast and 

 the lower river valleys. Supplementary to this was the discovery, in a 

 number of spots protected from erosion on some of the islands of the 

 Maine coast, of patches of marine clay above 200 feet. On North Haven 



* Baron Girard De Geer : On Pleistocene changes of level in eastern North Amerlck. 

 Proc. Boston Soc. Nat. Hist., vol. xxv, pp. 454-477. 



