DISCUSSION OF “SUMMARIES OF PRE-CAMBRIAN 
LITERATURE OF NORTH AMERICA,” BY 
EDWARD STEIDTMANN 
TERENCE T. QUIRKE 
University of Illinois 
The recent ‘““Summaries of Pre-Cambrian Literature of North 
America” by Professor Edward Steidtmann’ bring up points to 
which certain contributions and corrections should be made. He 
states that, 
(1) . . . . the pre-Cambrian rocks northeast of Lake Huron show one con- 
spicuous unconformity, and above the conspicuous unconformity are two series 
of slightly metamorphosed, dominantly clastic sediments, separated by an 
inconspicuous unconformity. (2) The lower one, the Bruce series, locally 
contains tillites. The upper series is generally known as the Cobalt series. 
(3) At Killarney, on the north shore of Lake Huron, Collins has found that 
the Bruce and possibly the Cobalt series are intruded by Killarney granite, 
and in this locality they assume many of the characteristics of the older series, 
the Timiskaming.” 
In regard to the so-called ‘inconspicuous unconformity,”’ 
Steidtmann followed Coleman (1915) and Miller and Knight 
(t915).4 Later work by Collins’ shows that in the region southeast 
of McCabe Lake, north of Cutler, erosion removed the Serpent 
quartzite, the Espafiola group, the Bruce conglomerate, and part 
of the Mississagi formation, amounting to the greater part of the 
Bruce series, previous to deposition of the Cobalt series. In 1914 
he showed that the erosion interval amounted to thousands of 
t Jour. Geol., Vol. XXVIII (1920), pp. 643-58. 
2 [bid., p. 643. The numbers have been inserted by the writer. 
3 A. P. Coleman, Problems of American Geology, pp. 81-161. Quoted by Edward 
Steidtmann, op. cit., p. 647. 
4W. G. Miller and C. W. Knight, Jour. Geo!., Vol. XXIII (1915), pp. 585-909. 
Quoted by Edward Steidtmann, oP. cit., p. 656. 
5 W. H. Collins, report in preparation. 
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