A Late Silurian (Pridolian) age for the Eastport Formation, Maine: a review of the fossil, stratigraphic, and radiometric-age data

Authors

  • Lisa Churchill-Dickson Maine State Museum, 83 State House Station, Augusta, ME 04333-0083, USA <paleo@gwi.net>

DOI:

https://doi.org/10.4138/1038

Abstract

The Eastport Formation is part of a larger volcaniclastic sequence (the Coastal Volcanic Belt) that extends from Massachusetts, USA, into New Brunswick, Canada. It represents a portion of Avalonia that was accreted to Laurentia during the Acadian orogeny. For more than thirty years the age of this formation has been regarded as Early Devonian (Lochkovian or Pragian) based on a new and yet undescribed ostracode genus. However, careful analysis of the fossil data indicates a Late Silurian (Pridolian) age for the fauna, and shows that the evidence used to assign a Devonian age should have been regarded as provisional. This interpretation is additionally strengthened by local stratigraphy and recent radiometric dating, both of which support a Late Silurian age for the Eastport Formation. RÉSUMÉ La Formation d'Eastport fait partie d'une séquence volcanoclastique plus importante (ceinture volcanique Côtière) qui s'étend du Massachusetts, aux États-Unis, jusqu'à l'intérieur du Nouveau-Brunswick, au Canada. Elle représente une partie du continent avalonien qui s'était accrétionné au continent laurentien pendant l'orogenèse acadienne. Pendant plus d'une trentaine d'années, on a considéré que cette formation remontait au Dévonien précoce (Lochkovien ou Praguien) en se basant sur un nouveau genre d'ostracode encore non décrit. Une analyse attentive des données relatives au fossile révèle toutefois que la faune remonte au Silurien tardif (Pridolien) et montre que les observations utilisées pour l'attribution d'un âge dévonien auraient dû être considérées comme provisoires. Cette interprétation se trouve par ailleurs renforcée par la stratigraphie locale et une datation isotopique récente, qui appuient toutes deux la datation de la Formation d'Eastport à l'époque du Silurien tardif. [Traduit par la rédaction.]

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Published

2004-10-10

How to Cite

Churchill-Dickson, L. (2004). A Late Silurian (Pridolian) age for the Eastport Formation, Maine: a review of the fossil, stratigraphic, and radiometric-age data. Atlantic Geoscience, 40(2/3). https://doi.org/10.4138/1038

Issue

Vol. 40 No. 2/3 (2004)

Section

Articles

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