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- Title
Along-strike variations in Furongian through Ordovician sedimentation and diachronous deformation within the northern Appalachians: Role of inherited margin geometry and colliding arcs.
- Authors
WHITE, SHAWNA; WALDRON, JOHN W. F.
- Abstract
Within the northern Appalachians, the deformed Laurentian margin and foreland basins show lateral variability in basin geometry, sediment provenance, and deformation timing. Although the margin is well-studied, inconsistencies in time scales, tectonic nomenclature, and sparse geochronological datasets have rendered it difficult to achieve an orogen-wide synthesis of the margin and overlying forelands' variability. To remedy this issue, biostratigraphic and isotopic data are placed on a common timescale. Using the replotted geological data, we focus on Cambrian through Ordovician orogenic events recorded in the Northern Appalachians to generate orogen-scale correlations. Earliest Taconian deformation is associated with arc-continent collision at off-margin microcontinents, confirmed by simultaneous margin deformation (recorded in the peri-Laurentian realm) and passive margin sedimentation (recorded in autochthonous and allochthonous rocks of the Laurentian realm). This deformation was strongly diachronous, occurring in the Furongian in Newfoundland and the Early to Middle Ordovician within the Québec Embayment, as was subsequent Taconic Seaway closure. In Newfoundland, closure began at ~ 470 Ma, resulting in obduction of allochthons above the margin. In Québec closure began at ~ 461 Ma and allochthon emplacement continued until ~450 Ma. In New England the seaway closed ~ 455 Ma. Pro-arc foreland basins developed in the Middle Ordovician in Newfoundland, but not until Late Ordovician in Québec. Diachronous subduction polarity reversal, occurring first in Newfoundland (~460 Ma) and later in Québec (~450 Ma), resulted in simultaneous westward and eastward subduction at different places along the margin leading to a unique hybrid basin (pro and retro-arc) in Newfoundland, analogous to the current position of the Akimeugah Basin on the northern Australian Plate. All major episodes of deformation, attributed to the Taconian orogeny in the northern Appalachians, were diachronous. Diachronous deformation resulted from irregularity of the Laurentian margin, distribution of off-margin microcontinents, and/or geometry of colliding arcs and microcontinents.
- Subjects
NEWFOUNDLAND &; Labrador; APPALACHIAN Mountains; QUEBEC (Quebec); ROCK deformation; SEDIMENTATION &; deposition; GEOMETRY; SUBDUCTION; OROGENY; SEDIMENTS; EDIACARAN fossils
- Publication
Atlantic Geoscience, 2023, Vol 59, p72
- ISSN
2564-2987
- Publication type
Article
- DOI
10.4138/atlgeo.2023.002