I 1^ V S. SHALER— -DEPOSITS "l EASTERN MASSACHUSETTS. 



foldings of the Carboniferous rocka in the neighboring Narragansett basin. 

 The only evidence on this point is thai above cited from tin- locality at 

 Marshfield. This locality is situated at the northeastern extremity of the 



at Narragansett synclinorium. The presumably Cretaceous beds at this 

 point are deposited in a great pocket formed by a long-continued land erosion 

 in the granitic rocks which occupy the anticlinal node at the northeastern 

 end of the Narragansett basin. The fact that this anticlinal district has 

 suffered no considerable dislocation is in a certain though insufficient way 

 evidence that the neighboring synclinorium was nol disturbed during the 

 period of the Martha's Vineyard dislocations. 



It seems to me clear that a very considerable geological time has elapsed 

 since the disturbances of the Vineyard Beries were brought about. This is 

 -how n by two classes of evidence: In the first place, on the north Bhore of 

 the island we have, as is indicated in the section at Cape Higgon, an ex- 

 tended Beries of deposits to a greal extent composed of unatratified materials 

 worn from the older rocks which lie iii nearly horizontal attitude- against 



the upturned strata of earlier age. The tim scupied for the erosion and 



deposition of these sediments musl have been considerable. Next, we note 

 the tact that the Burface of the island has a strongly accented topography 

 incised upon the beds of Cretaceous and Ternary age, which was in good 

 part, at least, developed after the deposition of the last -mentioned horizontal 

 accumulations. The considerable width of the valleys in relation to the 

 remaining upland- clearly indicates that the base-leveling process went on 

 for a long time. Yet further evidence of the same nature is afforded by the 

 insulated character of the Martha's Vineyard elevation. It is clear that a 

 deep valley was formed between this elevation and the Bhore line of the 

 continent to the northward. It is not likely thai any considerable part of 

 this excavation was accomplished during the last ice period, for the reason 

 that the Martha'.- Vineyard area was very little eroded during the glacial 



time. These points have in the main been noted in my report <>n the island 



of Martha'.- Vineyard, bul t heir importance is now more evident than before. 

 The evidence in this way obtained appears to indicate thai while the last 

 disturbances of an orogenic nature which have affected the Vineyard series 

 are of relatively recenl geological time, the period which elapsed unce their 

 conclusion and before the coming of the last ice-sheet was really great. 

 Although the evidence can noi be fairly presented in a numerical way, it seems 

 to in- . considering the' amount of erosion as well a- the remaining evidence 

 of depositional work, that the time intervening between the close of the 

 Vineyard movements and the beginning of the later glacial period must 

 have been at least twenty time- a- long a- thai which ha- elapsed since the 

 departure of t he ice from this Held. 



In the before-mentioned report on the geology of Martha's Vineyard I have 



