Itinerary 15 



The course of the Old Crow River was ascended about one hun- 

 dred and seventy miles by following its winding series of incredible 

 and complicated curves, though the extreme point reached was 

 estimated to be not over half that distance from the mouth of the 

 river in a straight line. Along their southern margin the uncon- 

 solidated deposits that fill the Old Crow Basin present at first a 

 terrane such as is to be expected along the shore of a lake. Con- 

 siderable thicknesses of gravels and sands were noted for about 

 fifteen miles, until passing more towards the center of the basin 

 area the sediments changed to homogeneous gray clays in which 

 gravel was totally absent, and where only small quantities were occa- 

 sionally observed on the bars associated with fragments of fossil 

 mammal bones that have been deposited during spring floods by 

 floating ice from the headwaters of the river. As the course of the 

 river winds through these frozen silts it generally presents bold 

 escarpments along the concave sides of the curves, with muddy bars 

 overgrown by dense thickets of willows opposite. It is on the 

 tops of these high silt blufifs the beds of elevated ice are exposed 

 and their more recent relation to the silts themselves so clearly 

 demonstrated. 



These ice-beds are not extensive sheets covering large areas but 

 rather restricted masses, rarely exposing over one-half mile of con- 

 tinuous ice, that appear to be frozen ponds, ox-bow, or other lakes, 

 that remained in the low parts of the undulating surface of the lake 

 bottom when it was drained. As their mode of origin and forma- 

 tion will be discussed later we may pass them with the statement 

 that the Old Crow Basin presents this phase of elevated Pleistocene 

 silts with ice on top developed to a greater extent than the writer 

 has seen or read of anywhere else. Beds of ice were observed as 

 far as we were able to ascend the Old Crow River, They appeared 

 on top of the banks, always at elevations of one hundred or more 

 feet above the stream, for a distance of more than one hundred 

 miles along the stream and no doubt continue to the northern limit 

 of the basin. The ice varies greatly in color, structure and thick- 

 ness. Some is of a brownish hue having much the same color as 

 peat water and containing quantities of comminuted vegetable mat- 

 ter, in some parts distributed evenly through the mass, and at other 

 places concentrated in thin layers like sheets of paper between thick- 

 nesses of clear ice. Some is whitish and granular, especially at 

 its surface, and often contains numerous cavities of gas bubbles. 

 At other places masses of green and blue ice were observed. In some 

 exposures all three kinds of ice are associated within one hundred 



