Geological occurrence and geochemistry of some oil shows in Nova Scotia

The occurrence and organic geochemistry of six bitumens from two different regions of Nova Scotia are discussed. Five of the samples are from the Lake Ainslie area of western Cape Breton, where oil seeps have been described since 1864. Many wells were drilled in this area from 1869 to present and although most encountered oil shows, no commercial discoveries were made. The oil seeps are either associated with upper Horton Group (Ainslie Formation) or basal Windsor Group (Macumber Formation) sediments. The biomarker distributions of the samples are similar to Stoney Creek oils and their lacustrine carbonate source rock (Albert Shale) of the Moncton Subbasin, New Brunswick. Thus the source rock of the Lake Ainslie bitumens is also interpreted to be a carbonate deposited in a lacustrine setting, probably within the Strathlorne Formation. A bitumen from the Canadian Salt Company Ltd. salt mine at Pugwash on the southern shore of Northumberland Strait was also analyzed. This was a sample of an oil seep that accumulated in one level of the mine within Windsor Group evaporites. The biomarker distributions of this sample are consistent with a source rock deposited under high salinity conditions, suggesting the source rock is an organic-rich interval within the Windsor Group evaporites.