652 EDWARD STEIDTMANN 



Timiskaming series — slate, graywacke, quartzite conglomerate, and schistose 

 derivatives 

 Igneous — Feldspar porphyry — relation to Timiskaming uncertain — 



intrudes Keewatin 

 Intrusive contact 

 Keewatin — ^Amygdaloidal and ellipsoidal basalt, diabase, serpentine, iron 

 formation, and breccia, with metamorphosed equivalents 



The gold occurs as free gold and as tellurides in quartz veins 

 cutting Keewatin and Timiskaming rocks. The veins contain high- 

 temperature minerals, viz., pyrrhotite and tourmaline. 



Kindle and Burling^ conclude that the escarpment of pre- 

 Cambrian rocks which overlooks the plain of Paleozoic sediments 

 north of the Ottawa and St. Lawrence rivers is due to normal 

 faulting, the sediments being on the downthrow side. The facts 

 which indicate this are : {a) the presence of Paleozoic outliers rest- 

 ing on a hummocky surface of pre-Cambrian rock north of the 

 escarpment, the corresponding Paleozoic beds south of the escarp- 

 ment being about seven hundred feet lower, {h) the extreme 

 regularity of the escarpment, {c) the absence of Paleozoic re-entrants 

 along the escarpment, {d) the lack of clastic material from the lime- 

 stone adjacent to the pre-Cambrian rocks of the escarpment, 

 (e) the dissimilarity of the escarpment features with other nearby pre- 

 Cambrian borders where normal erosion has even yielded an escarp- 

 ment of Paleozoic rocks, (/) the escarpment is at the northern border 

 of a zone in which subsidence or normal faulting is characteristic. 



Knight^ finds the following succession of pre-Cambrian rocks 



in the Thessalon area on the north shore of Lake Huron to the 



west of Killarney. This is the original Huronian area of Logan. 



Diabase dikes intersecting Nipissing 

 Keweenawan — D iabase 

 Intrusive contact 



Nipissing diabase, simUar to that at Cobalt and Gowganda — 

 shows local gradations into pink micro pegmatite. Thessalon 

 greenstone, a fine-grained basal sometimes amygdaloidal 

 Intrusive contact 



^ E. M. Kindle and L. D. Burling, "Structural Relations of the Pre-Cambrian 

 and Paleozoic Rocks North of the Ottawa and St. Lawrence Valleys," Canada Geol. 

 Surv. Mus. Bull. No. 18 (1915), 23 pp., 2 pis., 6 figs. 



= C. W. Knight, "The North Shore of Lake Huron," Ontario Bur. Mines, Ann. 

 RepL, Vol. XXIV (1915), Part I, pp. 216-41, 13 figs. 



