74 PROCEEDINGS OF THE WASHINGTON MEETING 



the Detroit River series. The question involved is not confined to the Detroit 

 River region alone, but is contingent on observed conditions over the whole 

 southwestern part of Ontario, as well as much of Ohio, and which conditions 

 are undoubtedly similar to those in other adjoining States to the west. Near 

 the eastern end of Lake Erie the relation of the Onondaga to the Silurian is 

 one of unconformity (disconformity). This is well illustrated in the outcrops 

 at Buffalo and to the westward in Ontario. There are, however, two distinct 

 erosion periods represented at or near the base of the Onondaga. One of these 

 preceded and the other followed the Oriskany sandstone. 5 It is probable that 

 it was the latter of these that scattered the sands of Oriskany origin over a 

 much wider region than that originally covered by the formation itself. This 

 is indicated by the fact that none of the sandy remnants at the base of the 

 Onondaga, west of North Cayuga township, in Ontario, carry even the slightest 

 trace of Oriskany fossils. At most places a well developed basal conglomerate 

 may be found in the lowest Onondaga beds, but occasionally it is rather im- 

 perfectly formed or sometimes entirely wanting. Even in such cases, however, 

 not one of the Ontario contacts, and few, if any, of those in Ohio thus far 

 examined, is without abundant evidence of the erosion period that intervened 

 between the formations in contact. Near Springvale this is abundantly shown 

 by the reworked beds of Oriskany, that now contain an Onondaga fauna, and 

 the widened cracks in, the pre-Oriskany dolomites, which are now filled with 

 sand to a depth of several feet below the contact. At Goderich, Ontario, the 

 basal conglomerate of the Onondaga limestone is especially well developed. 

 Pebbles of the Upper Monroe as large as a man's fist are mingled with 

 Onondaga corals, brachiopods, trilobites, etcetera, in an arenaceous limestone 

 which rests on an uneven surface of Monroe. In the early days of the 

 Goderich salt industry Mr. Attrill drilled a test well near the Lake Huron 

 shore, across the Maitland River from Goderich. In reporting on the results 

 of this experiment, Dr. T. Sterry Hunt says : "We now come to the considera- 

 tion of an unexpected result of the examination of the cores from the Goderich 

 boring, namely, the occurrence beneath 27S feet of beds, chiefly dolomite, 

 which, according to the Geological Survey, underlie the Oorniferous (Onon- 

 daga) limestone of the region, of not less than 276 feet, chiefly of gray, non- 

 magnesian. coralline limestone, abounding in chert and seeming like a repeti- 

 tion of the Oorniferous (Onondaga). Beneath this lower fossiliferous lime- 

 stone, it will be noted, are dolomites with gypsum, succeeded by variegated 

 marls, with an aggregate thickness of not less than :>64 feet before reaching 

 the saliferous strata, which latter have been penetrated 520 feet without reach- 

 ing the underlying Guelph formation. Prof. James Hall, who has kindly ex- 

 amined such specimens of the corals as I have obtained from the limestone, 

 recognizes in them two species of Favositcs, Favosites ivinchelli and Favosites 

 emmonsi, together with a section of Accrvularia <>r Dipfoyphyllum-" e This fos- 

 siliferous horizon is undoubtedly a part of the Detroit River series and very 

 probably includes the Amherstburg dolomite and the Anderdon. as these beds 

 outcrop about 35 miles farther north. The interesting point here is that it 

 lies 278 feet below the base of the Onondaga, and that this latter has a well 



5 Bull. Geol. Soc. Am., vol. 23, 1912, p. 373 ; also Geol. Survey Canada, Memoir 34, 

 1915, p. 60 and pi. iii. 



8 Geol. Survey of Canada, Rept. Prog, for 1876-1S77 (187S), p. 242. 



