114 PROCEEDINGS OP THE WASHINGTON MEETING 



the highlands east of Georgian Bay. It is nearly 100 feet thick, and if the 

 successive pairs of laniime be regarded as marking annual periods of deposi- 

 tion, this deposit, as I now recall it, would indicate a time of about 2,500 years 

 for its formation. It has seemed to me that laminated clays of this type are 

 particularly characteristic of deposition in association with the retreating ice- 

 sheet, and it is a striking and impressive fact to find precisely similar clays 

 greatly indurated and so closely associated with the ancient tillites. 



Mr. John L. Rich: In a bottom of an old pond I once found a deposit of 

 beautifully developed banded clays, in which the bands were marked by frag- 

 ments of leaves. In this case the banding clearly represented seasonal ac- 

 cumulation, the leaf-bearing partings corresponding to autumn and winter, 

 when the fallen leaves were being carried and deposited by the streams. 



Prof. R. B. Woodwobth said that Mr. Sayles' correlation of the banded 

 shales with the tillite beds at Squantum added another group of water-laid 

 deposits which have been identified among the ancient glacial formations 

 wherein we should expect to find the equivalents of our Pleistocene and modern 

 sand plains, kames and espars, and brick clays ; already possible examples of 

 one or another of these have been reported in Brazil and elsewhere. 



GEOLOGY OF THE LAKE IDITAROD REGION, ALASKA 

 BY PHILIP S. SMITH 



(Abstract) 



The paper describes the area! geology of the Lake Clark-Iditarod region, 

 Alaska. This region is located in southwestern Alaska, extending from the 

 Pacific Mountains to the central part of the Yukon Plateau province. The 

 rocks are dominantly sedimentary strata of Mesozoic age, but some Paleozoic 

 limestones are also exposed. Igneous rocks, both of intrusive and of effusive 

 origin, occur at a number of places, and certain of them seem to have been 

 closely associated with the deposits of commercial value, such as gold and 

 quicksilver. Unconsolidated deposits are widespread and throughout much 

 of the region mantle over and hide underlying bedrock. These deposits are 

 mainly of glacial and glaciofluviatile origin, though lacustrine, fluviatile, and 

 volcanic ash deposits are also described. 



Presented by title in the absence of the author. 



CHARACTERISTICS OF THE SOIL AND ITS RELATION TO GEOLOGY 

 BY C F. MAKBUT 



(Abstract) 



The soil is made up mainly of rock-waste. Its characteristics are of two 

 kinds: (1) those derived from the rock from which it came, or those that are 

 inherited, and (2) those impressed on it by the forces that have been acting 

 on it since its life history began, or those that are acquired. The latter char- 

 acteristics are relatively few in number and vary with many factors. The 

 conditions determining their character and strength of expression were dis- 

 cussed. 



