UNION AND RIVERSDALE FORMATIONS OF NOVA SCOTIA 533 



The fourth paper was the following : 



MESO-CARBONIFEROUS AGE OF THE UNION AND RIVERSDALE FORMATIONS, 



NOVA SCOTIA 



BY H. M. AMI 



[Abstract] 



For many* years it was taken for granted that the high]}' fossiliferous beds of 

 carbonaceous shales, etcetera, known as " the fern ledges " of New Brunswick were 

 of Devonian age, although the character of the flora, even at first sight, is one of 

 decidedly Carboniferous facies. The eighty or more species representing the flora 

 of that period are preeminently Carboniferous, and recently Dr David White has 

 recorded no less than seventeen species of Pottsville forms which came originally 

 from the "fern ledges." The Lancaster formation of the author was defined as 

 that series of strata which held this very characteristic flora, and it is capped by 

 another Carboniferous formation consisting of red shales and conglomerates, with 

 but few species occurring therein ; to which formation the designation Mispeck 

 formation of New Brunswick was applied. These two formations, the Lancaster 

 and the Mispeck, find their equivalents in the Union and Riversdale of Nova 

 Scotia, which Sir William Dawson always held to be of Middle Carboniferous age 

 (Middlestone grit). 



The main argument advanced by those who held that these four Middle Carbon- 

 iferous formations were " Devonian " was based on the supposition that the Lower 

 Carboniferous limestones rested unconformably on these same or equivalent 

 formations. 



In two of the crucial localities in Nova Scotia visited by the writer some time 

 ago, where Carboniferous shale rested unconformably on shales, etcetera, it has 

 been ascertained beyond a doubt that in one instance (at West bay, near Partridge 

 island and Parrsboro, in Cumberland county, Nova Scotia) the Carboniferous lime- 

 stone proved, on examination of the organic remains entombed in them, to be of 

 true and undoubted Upper Carboniferous age and not Lower Carboniferous, while 

 in the other instance (in the MacArras Brook region of Nova Scotia, where the 

 "Lower Carboniferous" strata rested unconformably on the so-called " rocks of 

 Union," or Union formation) the writer finds that the subjacent strata are in no 

 sense equivalent to the rocks of the Union formation at all (as they are developed 

 at the type locality near Union station, on the Intercolonial railway, just below 

 Riversdale). The Lower Carboniferous strata at MacArras brook rest unconform- 

 ably on the upturned edges of the lowest Devonian of that region, as the fossil 

 evidence obtained very clearly showed.* The Knoydart formation of Eo-Devonian 

 age, as seen and developed at MacArras brook, contains a fauna which is so nearly 

 allied and identical with that of the lower " Old Red Sandstone " strata of Scotland 

 and Great Britain generally that the two can very well be classed as homotaxial 

 and belonging to the same period in the history of the earth's crust — an horizon 

 or formation which had not been previously recorded in America, and which 

 nevertheless occupies a definite position, not at the summit of the Devonian, as 

 some geologists would have us believe, but indeed at the very bottom of the system 

 or division of the time-scale. 



*See Bull. Geol. Soc. Am., vol. 12, 1901, pp. 301-312, pi. 26. 



