DIFFERENT PROVINCES OF NORTH AMERICA IN LATE PALEOZOIC TIME 55 



It is only the upper two of these that need be considered as being within 

 the time which would include the evolution of life at the close of the Paleo- 

 zoic, but they are so clearly a continuum of the lower formations that a clear 

 understanding of their significance demands a comprehension of the whole 

 post-Mississippian-Joggins series. The Joggins section reveals the structure 

 and deposits of the great Cumberland Basin, which extends from the Cobe- 

 quid Hills on the south to the Minudie Anticlinorum on the north, and 

 from Chignecto Bay to the Pictou Basin, with only minor interrupting folds. 



The Mississippian, Windsor formation, consists of brick-red micaceous 

 shale (1,024 feet), brick-red sandstone (209 feet), reddish sandstone (36 

 feet), greenish gray sandstone with comminuted plant remains (156 feet), 

 and greenish gray lenses of concretionary limestone (88 feet) ; total 1,693 feet. 



Bell described the Windsor series as follows:^ 



"The fauna of the marine dolomitic limestones of the Windsor series at the 

 base of the Joggins section indicates broad, clear-water, shallow, and warm seas. 

 The succeeding and widely distributed deposits of gypsum were undoubtedly 

 accumulated in shallow pans of the sea under a subarid and probably warm 

 climate. The interbedded and overlying red shales and marls, barren of life, 

 with an abundance of mud-cracks and ripple-marks, together with the general 

 unleached condition expressed by the calcareous concretions and high alkali 

 content, denote similar climatic conditions and a general retreat of the sea, 

 followed by estuaries or wholly fresh-water deposition. The environmental 

 conditions at this time appear to have been especially favourable for the forma- 

 tion of fresh-water subaqueous delta deposits, adjacent to very shallow seas, 

 having had, it is thought, the forms of narrow but long basins, situated between 

 mountain masses that had their origin in Devonian times. 



"A complete withdrawal of the sea with consequent relative uplift of the land 

 prevented further deposition in this area, but possibly an extensive period of 

 erosion again brought about conditions favourable for fluvial deposition early in 

 Pennsylvanian time — conditions which seemingly persisted to the beginning of 

 the Permian time, as no truly marine or even estuarine fauna occurs in the Coal 

 Measures of the Joggins area. 



"The sediments of the millstone grit were laid down under more fluvial 

 conditions, an environment attested by the presence of occasional coal seams, 

 the increasing importance of dark to black shales, and the lighter coloured, though 

 still imperfectly leached, sandstones. The interbedded red shales, barren of 

 fossils, may represent the muds of fluvial flood flats, that subsequently were 

 oxidized subaerially, while the irregular lenticular beds of concretionary limestone 

 associated with the grey sandstones apparently add their evidence in favour of 

 fluvial conditions and a warm climate. 



"During the early Coal Measures the strata were laid down under more 

 fluvial and swamp conditions, as expressed by the many thin coal seams, the 

 predominant dark shales, and the more perfectly leached sandstones. 



"In later Coal Measure time there is no evidence for a continued abundance 

 of water, as the red-shale beds indicate seasons of aridity when all the carbon- 



^ Bell, W. G., Summary Report of the Geological Survey Branch of the Department of 

 Mines for 1911, Ottawa, p. 331, 1912. 



