1 62 /. HARLEN BRETZ 



These hills are bounded on the east and northwest sides by low, 

 wide valleys which constituted the two chief routes of glacial water 

 discharge from the basin of Puget Sound. The Olympic foothills 

 rise farther northwest in the main Olympic Range. At the time 

 of greatest extent of the ice, the northern slope of the Black Hills 

 was overridden and a lobe extended down on either side, the hills 

 determining a broad re-entrant in the ice front. 



II. PREVIOUS WORK ON THE MORAINE 



In a general way, the glacial drift in Puget Sound has long 

 been known to terminate some distance south of Olympia, and 

 the gravel plains have been commonly recognized as outwash 

 deposits from the ice. No detailed work, however, has been done 

 in the region except by Willis and Smith on the Tacoma quad- 

 rangle. 1 Here the contact between Pleistocene deposits from the 

 glaciers of the Cascades and Mt. Rainier and the Puget Sound 

 drift has been traced along the northwest flank of the volcano to 

 the southern edge of the quadrangle. 



Warren Upham has described, 2 from a hasty reconnaissance, 

 what he believed to be the terminal moraine lying between the 

 base of Mt. Rainier and the Black Hills. He interpreted the 

 remarkable gravel mounds of the outwash plains of the region as 

 morainic topography of peculiar type. 



No observer, so far as the writer is aware, has previously noted 

 the existence of the western lobe of the glacier, lying between the 

 Olympic Mountains and the Black Hills. . 



III. MORAINE COURSE ACROSS THE GEOSYNCLINE 



The westernmost geosyncline of North America is regarded 

 by stratigraphers as finding its representative on the Washington 

 coast in the Puget Sound depression. Were it not for the accident 

 .of glaciation, this structural valley would today embrace a broad 

 inland sea, but the thick drift deposit constitutes a filling sufficient 

 to maintain most of the surface above sea-level. The terminal 



1 Bailey Willis and G. O. Smith, "Tacoma Folio, No. .54," U.S. Geol. Survey. 



2 Warren Upham, "Glacial and Modified Drift in Seattle, Tacoma and Olympia," 

 American Geologist, XXIV, No. 4. 



