Taconian Sedimentary Basins of the Appalachians

Diecchio, Richard J.

doi:10.4095/132191

Cited by 6 publications

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“…One of the earliest phases of Taconian subduction and associated foreland basin development appears to have occurred during early Middle Ordovician time in Newfoundland (Diecchio, 1991). The stratigraphic sequence represented by the Table Head Group is interpreted to have been deposited in a deep foreland basin apparently associated with thrust-loading during Whiterockian time (Jacobi, 1981;Cawood et al, 1988).…”

Section: Tectonic Setting and Origin Of K-bentonitesmentioning

confidence: 92%

“…There is a growing trend, however, to differentiate between the various episodes of Taconian deformation that occurred along the eastern margin of Laurentia (Drake et al, 1989). The temporal and spatial distribution of Ordovician deep foreland basin sequences in the central and southern Appalachians and along the western margin of the northern and Maritime Appalachians suggests that the orogeny occurred in several diachronous tectophases related to different convergence centers (Shanmugam and Lash, 1982;Diecchio, 1991;Ettensohn, 1991). The foreland basins are believed to have formed by thrust-loading during subduction (Jacobi, 1981;Quinlan and Beaumont, 1984;Lash, 1987).…”

Section: Tectonic Setting and Origin Of K-bentonitesmentioning

confidence: 95%

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Ordovician K-bentonites of eastern North America

Kolata¹,

Huff²,

Bergström³

1996

Ordovician K-Bentonites of Eastern North America

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Section: Tectonic Setting and Origin Of K-bentonitesmentioning

confidence: 92%

Section: Tectonic Setting and Origin Of K-bentonitesmentioning

confidence: 95%

Ordovician K-bentonites of eastern North America

Kolata¹,

Huff²,

Bergström³

1996

Ordovician K-Bentonites of Eastern North America

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“…Along the length of the Taconic orogen in eastern North America, an Upper Ordovician carbonate platform succession (the Trenton Group, and its equivalent) is succeeded by local deep-water shale basins (Diecchio, 1991). In eastern Ontario, Canada, the platform-tobasin succession is recorded by the Lindsay and Billings formations (Fig.…”

Section: Stratigraphic Frameworkmentioning

confidence: 99%

Petrology and potential tectonic significance of a K-bentonite in a Taconian shale basin (eastern Ontario, Canada), northern Appalachians

2005

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A 6 cm thick K-bentonite, herein defined as the Russell Bed, occurs in an Upper Ordovician deep-basin shale succession in eastern Ontario, Canada, forming part of the distal Taconic foreland in eastern North America. The bed lies within the pygmaeus graptolite Biozone, which is about 451 to 452 Ma in age. Although some bentonites are reported from this interval in eastern North America, we are reporting the first set of compositional data for a bentonite of this age. Gamma-log correlation identifies a potential minimum distribution area of < 2 × 10 5 km 2 for the K-bentonite, covering part of southern Quebec, New York State and eastern Ontario. The deposit coincides with the first influx of distal turbdites into this shale basin, associated with Taconic flysch, and simultaneous abrupt ventilation of the once anoxic deep-water basin, which had formed initially after foundering of the Upper Ordovician carbonate platform. Concurrent intrabasinal extinction of several graptolite species suggests that change in sedimentation, palaeoceanography and volcanism were linked to a regional external process. Compositionally, the bentonite is distinct from the older Ordovician platform deposits in eastern North America. The deposit contains abundant titaniferous phlogopite with 1.6 % BaO, fluoroapatite with 2.5 % F, and dynamically shaped glass spherules now altered to clay. The spherules and clay matrix constitute 45 % of the bed and, compositionally, define an illite (> 90 %)smectite (I/S) structure with about 7.5 % K 2 O %. Age-dating by Ar-Ar analysis of the phlogopite crystals yielded a younger than expected (440-445 Ma) age. This difference, along with evidence of localized chloritization of phlogopite, likely reflects known post-Ordovician hydrothermal activity within the basin. On the basis of several geochemical proxies, the magmatic source of the Russell K-bentonite falls within the trachyandesite field and was Ba-enriched. Comparison of geochemistry and mineralogy with older, Middle to Late Ordovician and younger Early Silurian K-bentonites within the Taconic orogen along eastern Laurentia and Baltica reveals that the potential source magma for the Russell Bed was more mafic, more alkaline, and less fractionated than sources typical of older (platform) bentonites. Instead, it is more similar to the younger Llandovery bentonites of Scandinavia and Scotland. It remains uncertain if it signals local or regional compositional change in volcanic source in the northern Appalachians.

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“…Bradley, 1989; Finney et al , 1996). In the Blountian depocentre in Tennessee (Thomas, 1977), black shales overlie carbonate‐ramp deposits and grade upward into a coarsening‐upward turbidite succession, reflecting drowning of the foreland plate and sediment dispersal from an orogenic terrain to the east (Shanmugam & Walker, 1978, 1980; Shanmugam & Lash, 1982; Diecchio, 1991). Despite the general southwestward thinning and truncation of the clastic wedge into the study area (Thomas et al , 2002), correlation of graptolite zones indicates earlier deposition of basal synorogenic siliciclastic deposits on the southwest than in the depocentre (Bradley, 1989; Finney et al , 1996).…”

Section: Regional Settingmentioning

confidence: 99%

Distinguishing fault reactivation from flexural deformation in the distal stratigraphy of the Peripheral Blountian Foreland Basin, southern Appalachians, USA

Bayona

Thomas

2003

Basin Research

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Reactivation of intraplate structures and weak zones within the foreland lithosphere disrupt the modelled geometry and pattern of migration of the flexural wave in foreland basins. In the southern Appalachians (USA), the Middle Ordovician unconformity, irregular Middle Ordovician distal foreland deposition and backstepping of Middle–lower Upper Ordovician carbonate strata have been related to migration of the flexural wave. However, integration of stratigraphy, tectonic subsidence history and composition of palinspastically restored distal foreland strata, using a map of subsurface basement structures as reference, allows us to distinguish an early event of inversion from two events of flexural migration. Sections restoring at very short distances outside the boundaries of a former basement graben have the youngest passive‐margin strata preserved beneath Middle Ordovician (∼466 Ma) peritidal to deep lagoonal carbonates with gravel‐size chert clasts. In contrast, sections restoring inside the graben record >470 m of truncation of pre‐Middle Ordovician passive‐margin strata, late onset of deposition (∼456 Ma), and subaerial features in carbonate and siliciclastic strata. The lacuna geometry and early patterns of distal foreland uplift and carbonate deposition indicate that inversion of a basement graben in response to Middle Ordovician convergence, rather than a migrating or semi‐fixed forebulge, was the primary control on the early evolution of the distal foreland. Drowning of the carbonate platform in more proximal settings, northeastward onset of deposition on upthrown blocks, and thick accumulation of carbonates in downthrown blocks record northwestward and northeastward flexural wave migration at the Middle–Late Ordovician boundary. In early Late Ordovician, the overall shoaling of carbonate and siliciclastic depocentres and the rise of tectonic subsidence curves indicate hinterlandward migration of flexural uplift. Both events of flexural migration were accompanied by influx of volcanic ash and synorogenic sediments.

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Taconian Sedimentary Basins of the Appalachians

Cited by 6 publications

References 0 publications

Ordovician K-bentonites of eastern North America

Ordovician K-bentonites of eastern North America

Petrology and potential tectonic significance of a K-bentonite in a Taconian shale basin (eastern Ontario, Canada), northern Appalachians

Distinguishing fault reactivation from flexural deformation in the distal stratigraphy of the Peripheral Blountian Foreland Basin, southern Appalachians, USA

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