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TitleSand-type variation in an onshore analogue to the North Baffin Fan: petrographic trends in the Cretaceous-Paleogene sandstones of Bylot Island, northwest Baffin Bay
AuthorSmyth, H; Haggart, J W; Hyden, F; Burden, E; Wielens, H
SourceCanadian Arctic Islands Project 2013-15; CASP Report 11, CASP.CAI2013-15.11, 2017 p. 143
Alt SeriesEarth Sciences Sector, Contribution Series 20150370
AreaBylot Island; Baffin Bay
Subjectssedimentology; fans; petrography; petrographic analyses; North Baffin Fan; Cretaceous
ProgramGEM2: Geo-mapping for Energy and Minerals Baffin Project Management
Released2017 03 01
AbstractCretaceous and Paleogene sedimentary strata exposed on Bylot Island and northeastern Baffin Island, Nunavut, Canadian Arctic, are proximal equivalents of those found within the offshore Lancaster Sound and the North Baffin Fan system in northwest Baffin Bay. Petrographic analysis of the outcropping sandstones has yielded valuable data on sandstone composition, sediment provenance indicators, and hydrocarbon reservoir potential, all of which will aid prediction of these factors in the offshore.
Cretaceous-Paleogene strata of Bylot Island have been correlated previously with the Hassel Formation (Kh), the Kanguk Formation (Kk), and the Eureka Sound Formation (Te). Samples collected from these strata were examined for petrographic data and several important trends are recognized. Firstly, the cleanest, most compositionally and texturally mature sandstones, are of late Early Cretaceous (Albian) to earliest Paleogene age. These are the Hassel Formation (Kh), Kanguk (Kk1 and Kk2), and lower Eureka Sound Formation (Te1) sandstones. The sandstones are medium-grained and typically quartz-rich (plutonic and sedimentary sources), with variable abundances of weathered and corroded alkali feldspar and felsic plutonic lithic fragments. Moderate to excellent porosity and permeability is observed in the sandstones, leading to the prediction of good reservoir quality. In all of the sections examined, there is a significant shift in sandstone compositional and textural maturity within the younger Paleog Eureka Sound Formation, between members Te1 and Te2. The sandstones of Te2 are finer grained, and show an increase in abundance of feldspar, which, unlike the underlying sandstones, comprises fresh alkali and plagioclase feldspar. These sandstones have the poorest reservoir quality. Following the deposition of Te2 sands there is an apparent gradual shift towards more compositionally and texturally-mature sandstones (Te3) and associated reduction in abundance of plagioclase feldspar.
We propose that the Eureka Sound Te2 sandstones are derived, in part, from a fresh basic magmatic source, and have poor hydrocarbon reservoir potential, whereas the underlying sandstones (Kh, Kk1, Kk2 and Te1) are likely derived from recycled sedimentary and local cratonic sources and have better reservoir potential. Feldspar dissolution is a common feature of the lower part of the succession and is an important mechanism for generation of secondary porosity and enhancement of reservoir potential.
Summary(Plain Language Summary, not published)
The authors studied samples of sandstone rocks of Cretaceous-Paleogene age (110-58 million years ago) collected from onshore Bylot Island and Baffin Island in northeast Nunavut in order to assess their potential as petroleum reservoir rocks. To have good reservoir potential, such rocks need to have high levels of porosity and permeability, and without much clay content filling up the open spaces between the sedimentary rock grains. The authors found that the older rocks in the succession have good reservoir potential, while the younger rocks have poor to moderate reservoir potential.

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