PART 6.— STRATIGRAPHY 2 



B.— Stratigraphy and Correlation of the Credit River Section 



By W. S. Dyer 



Introduction 



The strata exposed on the Credit river between Lake Ontario and Meadow- 

 vale, as pointed out in Part V of this series, belong in ascending order to the 

 Humber and Credit members of the Dundas formation ; the Erindale, Streetsville, 

 and Meadowvale members of the Richmond formation; and the Queenston, a 

 red shaly member of the Richmond, probably representing an estuarine phase 

 of the latter formation. 



With the exception of the overlying Queenston shales, the rocks consist of 

 grey to blue or brown fissile shales with interstratified beds of harder rock which 

 vary in composition from pure crystalline limestone to impure calcareous sand- 

 stone or arenaceous shales. The rocks indicate deposition in comparatively 

 shallow water as attested by the ripr3ie marks which are frequently seen, as 

 well as by the discontinuity of the limestone and other hard layers. 



The rocks of the Dundas formation, as exposed on the Credit, are very 

 similar to those of the same formation as exposed in the Humber valley to the 

 east and form a direct upward extension of these rocks. They are largely of 

 shale, there being on the average one foot of hard rock to six feet of shale. The 

 Dundas formation on the whole is much less fossiliferous than the Richmond, 

 as many feet of shale are entirely devoid of fossils, which, nevertheless, are 

 found in abundance in the limestone at two rather distinct horizons. 



The Richmond . formation rests conformably on the Dundas formation 

 without any apparent change in the lithological character of the rocks; the 

 faunal break, however, is distinct. The Erindale member of the Richmond is 

 very similar lithologically to the Dundas formation, but the Streetsville member 

 differs considerably in that it contains more limestone. The lower part of the 

 Meadowvale is also limy, but the upper part of this member consists largely 

 of shale. 



In both formations on the Credit, very few of the fossils are found in the 

 shale, although they nearly always occur in profusion in the limestone layers. 

 With regard at least to the lower or Dundas formation, this paucity of fossils 

 in the shale is rather surprising, as the similar shales on the Don and Humber 

 rivers at Toronto are usually very rich in fossils. 



The continuity of the section on the Credit river is interrupted very little. 

 The chief unexposed interval is of 50 feet and occurs in the unfossiliferous zone 

 of the Humber member. At this horizon, near the Mississauga golf links, the 

 river drops very little and there are no rock outcrops. 



The following table indicates the detailed subdivision of the rocks of the 

 Credit river, together with an approximate correlation with those of the Ohio 

 valley. 



2 See footnote, page 3. 



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