Braman, D. R., and L. V. Hills, 1992

Reviewed by Geoffrey Playford, Department of Earth Sciences,
The University of Queensland, Brisbane, Australia 4072

Established about a decade ago under the aegis of the Canadian Society of Petroleum Geologists and the Geological Association of Canada, the monograph series Palaeontographica Canadiana has achieved international status as a quality vehicle for publication of Canadian systematic palaeontology. The volume reviewed here is the second in the series to be devoted to a palaeopalynological topic (the first being Fensome 1987). It constitutes an updated version of a 1981 doctoral dissertation by Dennis Braman, who conducted the research under Len Hills's supervision at the University of Calgary. The study had a very substantial materials base: some 730 samples collected from six sections, well-exposed in the northwestern District of Mackenzie and contiguous northern Yukon Territory and aggregating ca. 4950 m in stratal thickness. Formations sampled comprise the sandyshaley Imperial Formation (predominantly; and including its type section) and the succeeding pebbly-conglomeratic, sandy, and shaley Tuttle Formation, of Frasnian-Famennian and Famennian-earliest Carboniferous ages respectively.

Not unexpectedly, the bulk of the text (pp. 14-41) and illustrations are occupied with detailed systematic documentation of the miospore flora (megaspores having been treated in prior works). Three new genera and 14 new species of miospores are established; the majority of the large number of other species identified had previously been reported from coeval Northern Hemisphere strata, especially of the Old Red Sandstone region. Taxonomic identifications and descriptions are more than adequately supported by good quality light micrographs of the generally well preserved microfossils. No scanning electron microscopy was evidently performed, but this is scarcely a cardinal defect in a Devonian-Carboniferous miospore study of this nature. Vertical distributions of all taxa recorded are detailed on a comprehensive double-page range chart (text-fig. 5). Seven miospore biozones (and several subzones) are delineated and are correlated with previously defined northern hemisphere zones based on miospore, megaspore, and conodont data (text-fig. 4). Occurrences of the newly instituted zones in the six litho-logged Imperial-Tuttle sections are depicted in text-fig. 6. Datings of the zones are inferred from associated conodont faunas where available and/or from relevant published palynological reports. In the latter respect, more attention might beneficially have been given to drawing comparisons with ranges of key miospore species from elsewhere, rather than simply, for the most part, suggesting gross palynozonal correlations. Only one form assignable to the Acritarcha is recorded, surprisingly so in view of the marine depositional settings postulated for much of the studied sequence.

The presentation contains commendably few blemishes. Among the latter may be noted: occasional usage of "microspore" (e.g., in text-fig. 4) in place of the more apposite term miospore; "LR" in text-fig. 5 should read LT; the unfamiliar term "echini" is utilized (p. 40) for what would conventionally be called coni or spinae; "Schultz's" (p. 13) is a misspelling of Schulze (or Schulze's). Contrary to text-fig. 5, current international agreement restricts Tournaisian (sensu stricto) to the Carboniferous system (the lower boundaries of both being coincident), with the lowermost Tournaisian of prior usage (i.e., Tn1a-lower Tn1b) now being assigned to the Famennian (=uppermost Devonian).

This publication stands as a very creditable addition to the Palaeontographica Canadiana stable. In terms of the stated aim of the research - viz., to analyze the miospore sequence and apply this in stratigraphic and sedimentological contexts - it is clear that such has been amply achieved, and the authors are to be congratulated for producing a publication of considerable interest and relevance to those concerned with Arctic Upper Palaeozoic stratigraphy, palynology, and phytogeography. In those respects, it usefully complements a recently published monograph (Ravn 1991) on younger Early Carboniferous (Visean) miospore floras from the Alaska North Slope.

The publication is obtainable from either Canadian Society of Petroleum Geologists, #505, 206 7th Ave. SW, Calgary, Alberta, T2P OW7; or Geological Association of Canada Publications, Department of Earth Sciences, Memorial University of Newfoundland, St John's, Newfoundland, A1B 3X5.

References

Fensome, R. A., 1987. Taxonomy and biostratigraphy of schizaealean spores from the Jurassic-Cretaceous boundary beds of the Aklavik Range, District of Mackenzie. Palaeontographica Canadiana, No. 4, 49 pp., 5 pls.

Ravn, R. L., 1991. Miospores of the Kekiktuk Formation (Lower Carboniferous), Endicott Field area, Alaska North Slope. American Association of Stratigraphic Palynologists, Contributions Series, No. 27, 173 pp., 29 pls.