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The AAPG/Datapages Combined Publications Database

CSPG Bulletin


Bulletin of Canadian Petroleum Geology
Vol. 41 (1993), No. 3. (September), Pages 307-324

Petrographic Study of Marginal Sediments from the Elk Point Group of Northwestern Alberta, Canada

M. Khanna, E.K. Walton, M.S. Shawa,


Primary mineralogy of the sandstones in the Devonian Elk Point Group was dictated by a predominantly granitic source area with minor metamorphic and volcanic components. Extensive diagenesis involved dissolution of feldspars and lithoclasts, precipitation of quartz, and a second phase of dissolution of feldspar, lithoclasts and quartz. Analysis of the clay fraction shows an absence of significant amounts of kaolinite but an abundance of illite and chlorite. Later, authigenic calcite and dolomite precipitated in Elk Point sandstones, which were subsequently further cemented by anhydrite.

Cementation, especially by quartz, has considerably reduced the porosity in many places. Regional variation in porosity is marked by high variability on meso- and micro-scales.

Authigenic calcite and dolomite are significant components but were subjected to dissolution before a phase of anhydrite growth. Partial dissolution of anhydrite is evidence of the last event. Periods of flushing by meteoric-water affected early stages of diagensis with evaporitic brines prominent in mesogenesis.


La mineralogie primaire des gres du groupe Elk Point devonien fut dictee par une region source principalement granitique avec des composantes metamorphique et volcanique mineures. Une evolution diagenetique considerable comprit la dissolution des fedlspaths et lithoclastes, la precipitation de quartz, et une seconde phase de dissolution des feldspaths, lithoclastes et quartz. L'analyse de la fraction argilleuse revele que la daolinite est absente en quantite significative mais que l'illite et la chlorite sont abondantes. Ulterieurement, de la calcite et de la dolomite authigenes precipiterent dans les gres d'Elk Point, qui furent ensuite cimentes par de l'anhydrite.

La cimentation, particulieerment par le quartz, a considerablement reduit la porosite a plusieurs endroits. La variation regionale de la porosite est marquee par une grande variabilite a l'echelle microscopique et a l'echelle mesoscopique.

La calcite et la dolomite authigenes sont des composantes significatives mais furent soumises a de la dissolution avant la phase de croissance de l'anhydrite. Le dernier evenement est la dissolution partielle de l'anhydrite. Des periodes de percolation d'eau meteorique influencerent les etapes precoces de la diagenese, alors que des saumures evaporitiques dominerent la mesogenese.

Traduit par Patrice de Caritat

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