Craig Burns

B. Sc. Honours Thesis

Stratigraphy of the Halifax Group - Goldenville Group Transition (GHT) of the Meguma Supergroup at Caribou Gold District (Drillcore LL81-5A), Nova Scotia

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Drillcore LL81-5A, recovered from the Caribou gold district, Halifax County, Nova Scotia, by Sherritt Gordon Mines Ltd. in 1980, is a 625.40 m-long continuous section of the Cambro-Ordovician Meguma Supergroup, representing 500 stratigraphic metres of the transition between the older, sandy Goldenville Group and the overlying, shaly, Halifax Group (GHT). This core presents an unusually long section of the upper part of the GHT. which appears to exert significant control on trace metal concentration in the Meguma Supergroup. the purpose of this study is to characterize the geology of drillcore LL81-5A, which should promote a better local and regional understanding of the GHT.

Three conformable stratigraphic units are noted in LL81-5A. In order of decreasing age, these are: Unit A (36 stratigraphic metres)- fining upward sequences of massive, carbonate-rich, medium grained metawacke and silty slate; Unit B ( 113 m stratigraphic metres~ interbedded manganiferous, chloritic, meta-argillites and metasiltstones and Unit C ( 351 stratigraphic metres)- fining upward sequences of metasiltstones and carbonaceous slates similar to base-cut-out Bouma sequences, with locally abundant convoluted stratification, load casts and ball and pillow structures. These units correspond to undivided Goldenville Group and Moshers Island and Cunard formations of the Halifax Group, respectively. These sequences are interpreted as turbidity current deposits.

Unit B meta-argillites host a trace metal assemblage that includes Ba, Pb, Zn, Ni, As and Mo, and are significantly enriched in MnO relative to other lithologies studies in LL81-5A. Unit C slates contain a trace metal assemblage of Ba, Rb, Sr, V, Cr, Sc, Cs, La, Ce and U and are interpreted as metalliferous black slates. Unit A metawackes are depleted in most trace metals relative to these lithologies, while Unit C metasiltstones contain average concentrations of most trace metals relative to these other lithologies.

Decreasing grain size and an increasing carbonaceous material, manganese and trace metal influence through the GHT in LL81-5A, implies deposition within a progressively anoxic, coarse-sediment-starved basin.

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Pages: 152
Supervisor: Marcos Zentilli