188 A. P. Coleman. — Lower Huronian Ice Age. 



Devonian if not older.* In 1906 Rogers described a still more 

 ancient glacial formation in the Griquatown series of Hay, 

 where striated bowlders occur in a very hard matrix, from 

 which they slowly weather out. Two of these stones kindly 

 sent me by Mr. Rogers are, as I can testify, thoroughly glacial 

 in appearance. The Griquatown series is certainly older than 

 the Cape rocks, apparently Cambrian or Precambrian. f If 

 Precambrian, the series mnst come near the upper limit, since 

 there are apparently three other series beneath it, the Camp- 

 bell Rand, the Kheiss, and the Namaqualancl schists. It 

 occupies perhaps about the position of the Keweenawan in 

 America. 



Since this paper was prepared a very interesting article by 

 E. H. L. Schwarz on " The Three Paleozoic Ice Ages of South 

 Africa" has appeared.:}: Schwarz was associated with Rogers 

 in at least part of the work and is convinced of the glacial 

 character of the lower deposits. This account of them agrees 

 with Rogers' papers cited above, but gives more details. 



'In an excellent paper before the recent Geological Congress 

 Prof. David described ancient glacial deposits, probably of 

 Cambrian age, in Australia and India, and showed some 

 very glacial-looking material from Australia, but I have seen 

 no printed copy of his paper. 



From the foregoing references it will be seen that Cam- 

 brian or possibly late Precambrian glacial deposits have been 

 found in various places in both hemispheres in latitudes from 

 70° to 30°. If they all belong to one period the refrigeration 

 must have been widespread, and one can hardly account for 

 them all as due to local mountain glaciers. 



For several years it has seemed to me very probable that 

 there was a still more ancient ice age. at the beginning of the 

 Lower Huronian in the Archean as defined in Canada or the 

 Archeozoic or lowest Algonkian as defined by various Amer- 

 ican geologists. The so-called Huronian "slate conglomer- 

 ate" of Ontario has attracted attention ever since Logan and 

 Murray mapped and described it in the typical region north 

 of Lake Huron nearly fifty years ago. Good descriptions of it 

 are given by Logan in the 1863 report of the Canadian Geo- 

 logical Survey ; where he refers to the different kinds of rock 

 enclosed as pebbles or bowlders, granite, felsite, certain green- 

 stones and jasper, for example ; and describes the matrix as 

 sometimes slaty, sometimes more quartzitic or like diorite or 

 greenstone: At present the matrix would generally be called 



* Trans. S, African Phil. Soc, vol. xvi, part 1, May, 1905. 

 f Trans. Geol. Soc. S. Africa, vol. ix, 1906 ; The Campbell Rand and 

 Griquatown series in Hay, pp. 8 and 9. 

 % Jour. Geol., vol. xiv, No. 8, pp. 683-691. 



