PLEISTOCENE.
The present glaciated pre-Cambrian surface is scantily covered by unconsolidated glacial sands and gravel which are being collected by natural agencies from the hills and more elevated parts into the depressions. As a consequence the hills are bare, while the valleys and ravines are soil-filled and support a strong forest growth. Neither sand nor gravel show signs of stratified arrangement. They play an unimportant part in the topographical appearance of the country; the only elevation composed of such materials being a small gravel hill to the east of Porphyry lake. Between that point and the hills near Mosher lake is a considerable extent of flat sandy country, the gentle contour of which contrasts with that of the surrounding hills.
A rather peculiar low apron of sand occupies the very end of the peninsula between Duncan lake and the West branch. It is of small extent, and is probably due to river deposition, the West branch at this point being sluggish and the surface of the sand showing indications of shifting stream beds.
An extensive area of sand lies at the end of Duncan lake, from whence it extends northward for several miles, also westward and south-westward toward the 550 foot hill shown on the map. Seen from any neighbouring hill this plain appears flat in comparison with the ordinary surface of the country. It consists of a fine, yellowish, unstratified sand. The several brooks crossing it are distinguished from those of other parts of the country by their tortuous courses which are constantly changing, and which render them unfit for canoe travel. The shallow character and sandy shores at the north end of Duncan lake have been caused largely by the transportation of sand into it by these brooks.
Glacial boulders are scattered over the whole district.