Fkbkuaey 12, 1897.] 



SCIENCE. 



263 



CUBBENT NOTES ON PHYSIOGRAPHY. 

 NORTHWESTERN OREGON. 



A GEOLOGICAL reconnoissance in north- 

 western Oregon by J. S. Diller (17th Ann. 

 Eep. r. S. Geol. Survey, 1896, 1-80) gives 

 new examples of mountains resulting from 

 the dissection of peneplains. The Coast 

 range in this district, consisting of inclined 

 Miocene and older formations, shows up- 

 lands, bevelled across the tilted strata in 

 gently sloping plains at various altitudes, 

 as if the product of erosion at successive 

 levels. A number of small monadnocks 

 rise above the upper plain, and the narrow 

 valleys of the streams are incised beneath 

 the lowest. The relations of the different 

 peneplains are not fully worked out. Dur- 

 ing the lower stand of the region, when the 

 peneplanation was accomplished, Willa- 

 mette valley of to-day was a drowned val- 

 ley, like the existing Puget sound ; and it 

 is now floored with the sediments of that 

 submergence. The sediments contain ice- 

 rafted boulders, thought to be derived from 

 the glaciers of the neighboring Cascade 

 range on the east, then more extensive than 

 now, in spite of the lower stand of the land. 

 During emergence two of the stronger riv- 

 ers seem to have maintained transverse 

 courses across the rising peneplain (the 

 Coast range), so that they now gather 

 headwaters in Willamette valley. Old sea 

 cliffs and beaches at various levels on the 

 western slope of the Coast range record 

 pauses during emergence ; similar pauses 

 are indicated by terraces along the river 

 valleys. The movement of elevation con- 

 tinued until a five-mile belt of the existing 

 sea bottom was added to the land ; the evi- 

 dence of this being found in the extension 

 of river channels seaward from their pres- 

 ent mouths, as determined by Coast Survey 

 soundings under Davidson. Subsidence to 

 the present altitude has drowned the rivers 

 a number of miles up stream, letting the 

 tide far inland. The present shore line is 



sub-mature ; alternating between bold rocky 

 headlands not yet cut back to a graded out- 

 line, and long, smoothly curved beaches of 



concave outline towards the sea. 

 J" 



GLACIAL DEPOSITS OF INDIANA. 



Under the above title, Frank Leverett, 

 who has for some years past carried on field 

 studies of the drift under the direction of 

 Professor Chamberlain, gives a summary of 

 his results for a central state (Inland Edtc- 

 cator, August, 1896, 24-32); the essay being 

 one of a series designed by Professor Chas. 

 Dryer, of the State Normal School at Terre 

 Haute, for the edification of local teachers. 

 Leverett states that the border of the drift, 

 as indicated on his outline map, needs cor- 

 rection, for repeated observations have con- 

 vinced him that it extends further south- 

 ward than is indicated on Wright's map of 

 the glacial boundary (Bull. 58, U. S. Geol. 

 Surv.). The succession of glacial deposits 

 and associated loess beds, with interglacial 

 soils, is briefly described and the chief mo- 

 raines are mapped. The terminal moraine 

 of the Wisconsin (third) stage of glaciation 

 is a broad ridge generally twenty feet high. 

 Within the space of half a dozen steps one 

 may pass from loess-covered tracts of earlier 

 drift to the bouldery drift of this later inva- 

 sion. There is an accompanying change of 

 soil color and composition, from ashy (loess) 

 to black (drift), of a great agricultural 

 importance. Certain prominent moraines 

 near the western boundary (Benton and 

 Warren counties) are overridden by trans- 

 verse or unconformable bouldery moraines. 

 A temporary lake, apparently enclosed by 

 ice on the east and north, explains the 

 sands spread over the northwestern coun- 

 ties. 



If the geographical aspects of the drift, 

 both as to form and occupation, could be 

 more fully stated by Mr. Leverett in an- 

 other article, better work by local teachers 

 would be still further promoted. 



