Lower Carboniferous ostracodes from the Maritimes Basin of eastern Canada: A review
DOI:
https://doi.org/10.4138/1671Abstract
Lower Carboniferous ostracode assemblages of marine affinity occur in sediments of the Codroy Group in southwestern Newfoundland and the Windsor Group in central Nova Scotia. Three ostracode assemblages are defined from Nova Scotia and five from Newfoundland. The assemblages are described from biohermal and non-biohermal limestones and fine-grained sihciclastic lithologies. The assemblages can be characterised by their responses to varying degrees of physiological stress, and are dominated by members of the Paraparchitacea, although bairdiaceans, hoDinomorph and kirkbyacean palaeocopids and kloedenellaceans may be locally abundant. In the Maritimes Basin, the combined effects of tectonism, eustatic fluctuation and a semi-arid climate resulted in palaeoenvironments that were characterised by low temporal and spatial stability. As a consequence, total ostracode species richness relative to individual species abundances was low, and often expressed in the development of low grade communities that were controlled more by physical (allogenic) rather than biological (autigenic) parameters. Under these conditions the eurytopic paraparchitaceans were capable of producing large populations in physically harsh palaeoenvironments, whereas die more stenotopic bairdiaceans and palaeocopes only occurred when conditions were favourable. R᳧SUM᳧ Les sdiments des groupes de Codroy (sud-ouest de Terre-Neuve) et de Windsor (centre de la Nouvelle-᳧cosse) renferment des assemblages d'Ostracodes, ᳲ affinity marine, du Carbonifᳺre infrieur. On reconnait trois assemblages en Nouvelle-᳧cosse et cinq ᳲ Terre-Neuve. Ces assemblages proviennent de calcaires (biohcrmaux ou non) et de lithologies siliciclastiques ᳲ grain fin. On peut caractriser ces assemblages par leurs re'ponses aux divers degre de stress physiologique. On y note la prlominance des reprentants des Paraparchitacea malgr l'abondance locale des bairdiacs, des palocopid hollinomorphes et kirkbyaces ainsi que des kloedenellacs. Dans le Bass in des Maritimes, la conjonction de divers facteurs (tectonisme, fluctuations eustatiques, climat semi-aride) se traduisit par des palomilieux caracteriss par une stabilit spatiale et temporelle faible. En consquence, larichesse spcifique totale des Ostracodes tait basse par rapport aux abondances spifiques individuelles et s'exprimait souvent part le dveloppement de communauts immatures controles par des parametres plus physiques (allogenes) que biologiques (autogenes). Dans ces conditions, les paraparchitacs eurytopiques pouvaient peupler abondamment les palomilieux physiquement exigeants, alors que les bairdiace's et les palocopes (qui taient plus stnotopiques) n'aienl prsents que dans des biotopes favorables. [Traduit par le journal]Downloads
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