| Résumé | (disponible en anglais seulement)
Studies of eastern Canadian offshore palynomorph assemblages were first conducted on rocks from shallow core holes drilled on the Grand Banks in 1965 by Pan
American Petroleum Corporation and Imperial Oil Enterprises. The first exploration-well samples were obtained in 1966. Palynological studies at the Atlantic Geoscience Centre (now Geological Survey of Canada Atlantic - GSCA) began in 1971 and are
ongoing. Initially, micropaleontological and nannofossil studies were also undertaken, but palynology increasingly became the focus at GSCA. Palynology of east-coast sections has also been carried out at the Geological Survey of Denmark and Greenland
in conjunction with work on the western Greenland Margin; at universities, notably Memorial in Newfoundland, and more recently at Saint Mary's in Halifax; and in industry, often in collaboration with government and academia. Biostratigraphy has been
the primary focus, and zonation schemes for some regions were proposed in the 1970s; recently, the approach has concentrated on event stratigraphy. Paleoenvironmental studies have also become increasingly important. Taxonomy of east coast palynomorph
assemblages lagged behind many similar areas, the first work appearing in 1986. However, several major monographs have been published recently, as well as a 'PalyAtlas', which facilitates taxon recognition.
Canada's east coast, from Nova Scotia to
Nunavut, is bounded by a huge continental margin, spanning about 40 degrees of latitude and ranging up to several hundred kilometres in width. It developed as a passive margin following the break up of Pangea, and incorporates a series of sedimentary
basins with Upper Triassic to Quaternary strata. Palynology has played a major role in providing a temporal framework for these basins, mainly facilitated by samples collected from over 600 wells drilled in the search for hydrocarbons. The
sedimentary rocks and palynomorph assemblages that the wells contain reflect the evolving tectonic and paleoenvironmental setting of the margin. In the south, the oldest rocks, of Late Triassic to Early Jurassic age, occur in rift basins. One is the
Fundy Basin, with extensive onshore outcrops; others, fully offshore, are buried beneath younger rocks on the Scotian Margin. During this early Mesozoic interval, deposition occurred under warm, dry subtropical, mainly non-marine conditions.
Palynomorph recovery in the predominantly red-bed and evaporite deposits is sparse, and assemblages consist mostly of miospores, including Classopollis and Echinitosporites; these assemblages are not easy to correlate with those from other
regions.
Sea-floor spreading in the nascent Atlantic began around the Early/Middle Jurassic boundary, with more marine conditions heralding an increasing diversity of dinoflagellate cysts (dinocysts) during the later Jurassic on the Scotian Margin
and southern Grand Banks, off Newfoundland. Both areas had interfingering carbonate platform and deltaic systems in the Middle Jurassic through Early Cretaceous, which allow both miospores and dinocysts to be used for stratigraphic and
paleoenvironmental control. Coeval pockets of non-marine Lower Cretaceous strata, some with rich miospore assemblages, are unexpected components of the onshore, mostly Paleozoic geology of the Maritimes.
As an extension of Tethys, the North
Atlantic Ocean opened initially along a southwest-northeast axis between Nova Scotia and Morocco. However, in the middle Cretaceous a northwest-southeast spreading axis began to develop between the northeastern Newfoundland margin and western Europe,
and continued to extend north to develop rift basins between what are present-day Labrador and Nunavut to the east and Greenland to the west, to produce the Labrador-Baffin Seaway. As farther south (albeit about 100 million years earlier there), the
oldest sediments in the Labrador-Baffin Seaway were non-marine, reflected in the miospore-dominated assemblages. In the Cretaceous progressed, and into the Paleogene, seawater flooded into the Labrador-Baffin Seaway, and the resultant strata contain
rich dinocyst assemblages. One especially distinct event is the acme of the dinocyst Apectodinium at the Paleocene/Eocene boundary in one of the southernmost wells on the Labrador Shelf.
To the north, important deposits of Cretaceous and Paleogene
age occur onshore, notably on Bylot Island, as well as offshore. The palynomorph assemblages in the Bylot Island sediments, which are of Cretaceous-Paleocene age, show distinct provincialism correlatable with high latitude assemblages of the Southern
Hemisphere in the Late Cretaceous. Farther south, on the Scotian Margin and Grand Banks, Paleogene deposits contain rich dinocyst assemblages, commonly dominated by areoligeraceans. Climatic cooling and generally shallower seas during the Neogene are
reflected in the palynomorph assemblages, especially in the content of pollen species.
Overall, palynology has made a major contribution to our understanding of offshore (and some onshore) eastern Canadian Mesozoic-Cenozoic successions; and
palynologists in eastern Canada have made a significant international contribution to the discipline. |