Abstract
The Upper Ordovician (Edenian) Lindsay Formation of the Ottawa Embayment represents the final stage of carbonate platform development in the Taconic foreland periphery inboard of the northern Appalachian orogen. The succession overlies a narrow (~60 km) axis of a Neoproterozoic Laurentian rift extending across the Grenville orogen. The Lindsay Formation consists of a lower heavily bioturbated skeletal limestone that represents a warm-water shoal facies following an underlying outer ramp stratigraphy, and an upper division of renewed deep-water deposition with organic-rich shale and fossiliferous lime mudstone. Pyritic deep-water black shale of the westerly advancing Taconic foreland basin disconformably overlies this platform succession. Stratigraphic correlation through the central embayment identifies likely synsedimentary faults and seaward-directed erosion bounding the Lindsay Formation in a region of older Ordovician faults and a change in the lithotectonic character of the crystalline basement. The Late Ordovician shallowing and localization of structural/erosional features are interpreted to record a structural hinge: a local accommodation to, first, foreland periphery uplift, then rapid subsidence related to westerly diachronous foreland subsidence through the platform interior. Spatial association of structures of differing ages suggests that reactivation of inherited weakened crust influenced Late Ordovician sedimentary patterns.
Highlights
IntroductionIn the northern Appalachian orogen, Middle to Upper Ordovician stratigraphic successions of the Taconic foreland document westerly (in today’s coordinates) diachronous foundering of a once prolific shallow-water carbonate platform in response to advancing foreland-basin sedimentation [1,2,3,4].Collapse of the platform margin was not uniform but aided by local structure (faults, synsedimentary folds), areas of abrupt subsidence, and possible mass wasting [3,5,6,7]
In the northern Appalachian orogen, Middle to Upper Ordovician stratigraphic successions of the Taconic foreland document westerly diachronous foundering of a once prolific shallow-water carbonate platform in response to advancing foreland-basin sedimentation [1,2,3,4].Collapse of the platform margin was not uniform but aided by local structure, areas of abrupt subsidence, and possible mass wasting [3,5,6,7]
The Upper Ordovician (Edenian) Lindsay Formation is the final stage of a foreland platform succession in the Ottawa Embayment, an erosional remnant of the foreland periphery inboard of the Sutton Mountains salient [8] (Figure 1)
Summary
In the northern Appalachian orogen, Middle to Upper Ordovician stratigraphic successions of the Taconic foreland document westerly (in today’s coordinates) diachronous foundering of a once prolific shallow-water carbonate platform in response to advancing foreland-basin sedimentation [1,2,3,4].Collapse of the platform margin was not uniform but aided by local structure (faults, synsedimentary folds), areas of abrupt subsidence, and possible mass wasting [3,5,6,7]. In the northern Appalachian orogen, Middle to Upper Ordovician stratigraphic successions of the Taconic foreland document westerly (in today’s coordinates) diachronous foundering of a once prolific shallow-water carbonate platform in response to advancing foreland-basin sedimentation [1,2,3,4]. Similar local structure, and related erosion were associated with the platform-to-basin transition inboard (~200 km) of the Laurentian paleomargin and western structural limit of the Appalachian orogen. The Upper Ordovician (Edenian) Lindsay Formation is the final stage of a foreland platform succession in the Ottawa Embayment, an erosional remnant of the foreland periphery inboard of the Sutton Mountains salient [8] (Figure 1). Erosional limits of basins are shown by the heavy black line.
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