215 



THE RIVERSD ALE-UNION GROUP AT TRURO 

 AND IN THE TYPE SECTION ALONG THE 

 INTERCOLONIAL RAILWAY EAST OF TRURO* 



INTRODUCTION. 



(G. A. Young.) 



The interest attached to the Riversdale-Union series 

 does not lie directly in the structures presented by these 

 measures nor in the characters of the faunas or floras they 

 may carry. It arises from the fact that though this series 

 locally at least, is as much as 10,000 feet (3,050 m.) thick, 

 apparently is widely displayed over a considerable portion 

 of Nova Scotia, and has been studied and mapped in detail, 

 yet one group of geologists holds that the strata are of 

 Devonian age while another group contends that the 

 measures are of Carboniferous, probably Pennsylvanian, 

 age. 



The strata of the Riversdale-Union series as exposed 

 along the Intercolonial railway eastward from Truro, 

 occur in a band of so-called Devonian rocks which stretches 

 continuously from Cape Breton island on the east to near 

 Truro on the west where the band forks. One branch 

 continues in a westerly direction along the south side of 

 Minas basin to Horton Bluff near Windsor, the other band 

 parallels the north shore of Minas basin and with some 

 interruptions, extends nearly to Cape Chignecto. The 

 length of the band from Cape Breton to Horton Bluff is 

 about 180 miles (290 km.), in places it expands to a width of 

 nearly 20 miles (30 km.), in other places it contracts to a 

 breadth of only 2 or 3 miles (3-5 km.). 



Throughout their whole extent, the measures have been 

 studied by the late Hugh Fletcher and mapped by him in 

 detail on a scale of i mile to i inch. His work shows that 

 along the borders of the long band of these measures, the 

 so-called Devonian is brought into contact with representa- 

 tives of most of the geological divisions developed in Nova 

 Scotia, though for many miles at a time the strata are 

 bounded by Carboniferous beds of Mississippian age. 

 The accompanying diagram map prepared from maps of 

 Fletcher exhibits his conception of the geological relations 



*See Map — Union-Riversdale. 



