OEOLOGlO HISTORY OF THE AREA 321 



Florida ; so that the climate around Waterville at the time of the deposi- 

 tion of the clays could not have been very different from what it is at 

 the present time. 



The mollusks indicate, in general, cold v^^ater influenced by melting ice, 

 while the plants indicate a warmer climate — not colder than Maine today. 

 This mean^ that the upper river valleys still contained remnants of 

 glaciers, thus cooling the waters — corroborating the evidence of the ice- 

 borne boulders of the clay — while the climate on the Jand liad wai-med 

 up, permitting the return of plants from tbe south. 



Geologic History of th'e Area 



This region, before the advance of the ice, had reached a stage of 

 erosional maturity. The wide valleys, which border the present rejuve- 

 nated streams and lie between narrow ridges or knol)s of slate rock, bear 

 abundant witness of this fact. The absence of sedimentary deposits l)e- 

 tween tbe supposed Eo-Paleozoic slates and the Pleistocene sands, gravels, 

 etcetera, would in itself point to a long-continued erosiou interval. 



Then came the odaciation, covering the highest hills of the area, wear- 

 ing off their soil, striating and polisbing the resultant rock surface. 'Idiis 

 is clearly seen wherever ledge is exposed. As tbo ice letreated, the surface 

 was moie or less covered with a sheet of till, and this is uow lieing eroded. 



I'his completes tbe history of this immediate area, so far as land 

 about IGO feet above sealevel is concerned. Below this level, in tlie valley 

 hottoms, a more complicated history is revealed, 'i'he pei'iod when the 

 ice covered the region is represented by the ground moraine of the liiglier 

 elevations and the fluvio-glacial deposits of the valleys. As tbe ice re- 

 treated tbe esker deposits were exposed and subjected to erosion. After 

 a comparatively short erosive interval the land was submerged. Tbe en- 

 croaching sea picked out the finer particles froui the eskei- gravel and 

 spread them over its slope and the adjoining area. As the sea gradually 

 became deeper the gravels were covered and clays collected in the (piiet 

 waters of the estuary. In' these waters flourished an alumdant fauna 

 nearly identical with that living off the coast at the present day, while 

 the land surface nourished a vegetation which, in respect to the limited 

 flora known, was similar to forms still inhabiting this region. 



Icebergs floating down the estuary dropped occasional boulders, which 

 were gradually covered by the clay. These icebergs may have come from 

 the retreating ice-sheet, but because of the lack of decided Arctic affinities 

 in the marine fauna it seems more than likely that the estuary was not 

 fed by the floods of cold water which would come fi-om this, but rather 

 from smaller, local glaciers j)ersisting in the bigh land toward the sources 



