Tammy Lee Allen

Late Carboniferous strata extend from northeastern New Brunswick to western Cape Breton Island underneath the Gulf of St. Lawrence, covering an area more than 200,000 km². On Cape Breton Island, these coal-bearing strata comprise the Port Hood, Henry Island, and Inverness formations of the Cumberland Group. Onshore successions of these strata are recorded in continuously cored diamond drill holes and exposed in coastal sections in western Cape Breton Island. The upper Port Hood Formation, or the Colindale Member, contains potential petroleum source rocks in the form of coals and organic-rich shales. Based on the correlation of stratigraphic sections, the total thickness of the Colindale Member exceeds 800 m. The Colindale Member is typified by thick intervals of dark grey and black organic-rich shales containing abundant fossils (bivalves and ostracods), with intercalated fine- to medium- grained grey sandstone bodies. Other fine-grained sedimentary rocks include grey mudstones characterized by blocky peds, slickensides, and root traces; laminated grey siltstone; thin fossiliferous limestones, and thin coal seams.

Sequence stratigraphic and sedimentological studies have revealed stacked parasequences (<1-15 m) and parasequence sets (10-100m). The parasequences and sets are bound by transgressive surfaces in the form of carbonaceous and fauna-rich strata. The parasequence sets, predominantly aggradational and progradational, consist of several prograding parasequences. Correlations of parasequence sets between the three coastal sections studied are not clear, suggesting that local controls were prevalent during deposition.

Results obtained from total organic carbon (TOC) analysis and Rock Eval pyrolysis from selected sections of the Colindale Member, has determined the following. Organic matter within the sedimentary rocks of the Colindale Member is composed of Type III kerogen with admixtures of Type II kerogen (woody and cellulosic material of terrestrial plants) which is typically gas-prone. TOC values (average 2.2%) suggest the Colindale Member has a fair to good generative potential to produce hydrocarbons. A combination of thermal maturity indicators (Tmax, vitrinite reflectance, TAI) suggest that organic matter in the Colindale Member is in the early maturity stage of thermal diagenesis. Although thermal maturity results indicate that these rocks are immature in onshore areas, potential exists for more mature (within the oil window) sediments at depth. Rocks of equivalent age can be traced to a limited extent beneath the southern part of the Gulf of St. Lawrence, implying that a viable regional hydrocarbon source may occur within the Gulf, if proper seal and reservoir parameters are met.

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Pages: 207
Supervisor: Martin Gibling

Awards

1996 - American Association of Petroleum Geologists - Marilyn Atwater Memorial Grant
1995 - Award for Highest Standing in Earth Sciences Honours Class, Dalhousie University
1995 - Amoco Canada Petroleum Company Undergraduate Scholarship
1994 - Canadian Society of Petroleum Geologists Student Industry Field Trip Participant