DOWNWARPING ALONG JOINT PLANES AT THE CLOSE 

 OF THE NIAGARAN AND ACADIAN 1 



LANCASTER D. BURLING 



Canadian Geological Survey, Ottawa 



The upper part of the Lockport dolomite exhibits a number of 

 interesting structural features. These are not confined to the 

 Lockport, but many of them have an important bearing on the 

 physical conditions during and immediately succeeding the forma- 

 tion of the Lockport and as such deserve attention. Among the 

 most striking of these are: (i) the huge vase-like residual masses 

 of the Lockport on Flowerpot Island 2 in the Bruce Peninsula of 

 Ontario; (2) the widespread doming of the strata which Kindle 

 has described 3 as probably analogous in origin to the mud lumps 

 at the mouth of the Mississippi; (3) the arching of the strata form- 

 ing the uppermost or Eramosa beds of the Lockport dolomite in 

 Ontario, where it is ascribed in at least one instance 4 to the 

 presence of an underlying coral reef; (4) the burial of Devonian 

 rock and fossils in joints 18 feet below the present glaciated surface 

 of the Niagara limestone in Illinois; 5 (5) the anticlinal arches which 

 characterize the Lockport in the Niagara region, and which Kindle 

 and Taylor 6 ascribe to local stresses of comparatively recent date; 

 (6) the ripple-mark and other sedimentation phenomena which 

 have been described so frequently; 7 (7) the immediate super- 

 position above the Lockport of the Salina with its salt and gypsum; 8 



1 Published by permission of the Deputy Minister of Mines. 

 3 Stauffer, Geol. Surv. of Canada, Guide Book No. 5, 1913, p. 75. 



3 Amer. Jour. Sci., 4th Ser., XV (1903), 459-68. 



4 Williams, Geol. Surv. of Canada, Museum Bull. No. 20, 1915, pp. 1-2. It should 

 be noted, however, that the horizon of the Eramosa beds is below the top of the Lock- 

 port as used, for example, by Kindle and Taylor in the Niagara Folio. 



s Weller, Jour. Geol., VII (1899), 483-88. 



6 Geol. Atlas of the U.S., U.S. Geol. Survey, Niagara Folio (No. 190), 1913, p. 109. 



7 Cf. Kindle, Geol. Mag., Dec. 6, 1 (1914), 158-61. 



8 Cf. Grabau, Bull. Min. and Metal Soc. Amer., VI, No. 2 (1913), 33-44. 



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