Palynology of the Windsor Group (Mississippian) in a borehole at Stewiacke, Shubenacadie Basin, Nova Scotia

Abstract

A palynological investigation of core samples from borehole SB-1 at Stewiacke, Nova Scotia, suggests that three miospore zones may be recognized. In terms of Bell's macrofaunal zonation, assemblage-zone I occurs in Lower Windsor subzones A and B, assemblage-zone II occurs in Upper Windsor subzones C, D, and E, and assemblage-zone III occurs in argillaceous beds containing intercalations of gypsum, which overlie the uppermost marine carbonate of the Upper Windsor subzone E. Slight differences distinguish miospore assemblages in macrofaunal subzones A and B, but the differences may be partly, or wholly, the result of reworking from the Horton Group. Preservation is very poor in the lower part of subzone A. Consequently, assemblages from these beds have been assigned only tentatively to assemblage-zone I(?).Tentative biostratigraphic correlation of the proposed miospore zones with the British Viséan suggests that assemblage-zone I is no older, and may be younger, than the upper part of the Upper Caninia (C2S1) Zone; assemblage-zone II possibly is similar in age to the Lower Dibunophyllum (D1) Zone; and assemblage-zone III is probably no older than the Upper Dibunophyllum (D2) Zone, although it may be younger. However, there is no palynological evidence to indicate that it is younger than the Upper Posidonia (P2) Zone of late Viséan age.The nature and thermal alteration of the organic matter suggest a source-rock potential for liquid hydrocarbons, but this potential is reduced by the abundance of halite, gypsum and (or) anhydrite in the succession.