GLACIAL LAKES OF PUGET SOUND 457 



been repeatedly observed by the writer, occurring on all important 

 inlets of the Sound. Shell-bearing terraces at higher levels, though 

 rarer, have been found at about 60 and 80 feet, and in three places 

 100 feet above present tide. 



Of the marine shell-bearing terraces at the highest level, two are 

 on the west side of Hood's Canal, and one at Tumwater on Budd's 

 Inlet. On one of the Hood's Canal 100-foot terraces, the sod and 

 forest soil are literally a mass of comminuted shell fragments to the 

 depth of a few inches. The 80-foot terrace is present immediately 

 below it. 



Unless error has been made in these observations, there is here 

 conclusive evidence that at some time subj^^quent to the fresh- water 

 occupancy of Puget Sound's southern valleys, the land was 100 feet 

 lower than now. 



From the rare occurrence of the consecutively higher marine 

 terraces of Puget Sound, and from the lack of any evidence to the 

 contrary, it has been assumed that the series represents successive 

 stages in a rising of the land which has been in progress throughout 

 post-glacial time. On this supposition, the 100-foot terrace repre- 

 sents the level of sea water on first entrance into the Sound after the 

 ice retreat from its northern portion. The loo-foot gravels at Gate 

 and the loo-foot marine terraces of the Sound seem good evidence 

 that the entire region was that much lower when the greater lake of 

 Puget Sound discharged southward across the Chehalis-Sound divide 

 during the retreat of the Vashon ice sheet. This lake then was but 

 20 feet above the sea at its lowest stage. 



It is well established by the outlet channel that static water was 

 held to its levels in the southern part of the Sound by ice in Admiralty 

 Inlet during Vashon retreat. The limited amount of examination 

 thus far possible has shown four rivers of the region to possess deltas 

 at one or more levels between 120 feet and 160 feet A.T. The Des 

 Chutes River has an old delta plain in the southern part of Olympia 

 160 to 170 feet high, and the Nisqually River dissects an old delta 

 at Sherlock, three miles back from the present coast, the summit 

 plain of which is about 160 feet high. Both deltas correlate with the 

 160-foot terrace in the outlet near Black Lake. They have been 

 examined only cursorily thus far, and nothing is known concerninng 

 lower stages. 



