Taxonomy of Ordovician ostracodes from western Newfoundland, Anticosti Island and the St. Lawrence Lowlands of Québec

• Main Author: Pitman, David John
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1991
• Subjects: Canada; Table Head; Long Point; Newfoundland
• Online Access: https://research.library.mun.ca/6902/; https://research.library.mun.ca/6902/1/DavidJohnPitman.pdf; https://research.library.mun.ca/6902/3/DavidJohnPitman.pdf

The results of an investigation of Middle and Upper Ordovician ostracodes from southeastern Canada are reported. Sixty-two samples were collected from the Table Head and Long Point groups, western Newfoundland, the Jolliet Group, Anticosti Island, and the Trenton Group, St. Lawrence Lowlands. These yielded over 2600 moderately to well-preserved ostracodes. The Carter Collection, an existing collection of ostracodes from the Lowlands, was also examined. During the research, a series of difficulties were encountered in obtaining the faunas, interpreting their taxonomy, and understanding their paleoenvironmental implications. -- In the sections studied, Ordovician ostracodes occurred sporadically and were often rare or absent. All the collections were obtained by washing soft shales or by vibra-tool preparation of indurate limestones; selection of samples that can be readily processed is essential. Ordovician ostracode taxonomy is often confusing; many species are narrowly defined and allow little morphological variation. In this study, the taxonomy of a number of species is revised and a number of existing species are re-interpreted as synonyms. Fifty-four species representing forty genera are described and illustrated. No new species are established, because the current species are either already described in the literature, or could only be identified at the generic level because of a lack of well-preserved material. -- Although faunal composition, abundance and diversity arc directly influenced by the paleoenvironment, it is difficult to develop ostracode-based criteria for the elucidation of Ordovician paleoenvironments. Observations made during this study indicate that sea-level changes and water depth were strong controls on the nature of Ordovician ostracode faunas. In the Lourdes Formation, western Newfoundland and the Ellis Bay Formation, Anticosti Island, marked increases in faunal diversity and the rates of speciation can be directly correlated with transgressive events that increased the shelf area and ...