Timing of Orogenic Events in the U.S. Appalachians

Osberg, Philip H.

doi:10.1007/978-94-009-7239-1_31

Cited by 9 publications

(4 citation statements)

References 29 publications

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“…5). There are also blocks of older units such as the Chain Lakes massif in the N Appalachians (Boone 1973, Naylor 1975, Osberg 1983, p. 317), which Boudette (1981 suggested is an allochthonous fragment. Zen (1983) considered this massif and fragments of Avalonian terranes as non-American and inserted a separating suture in the N Appalachians (a on Fig.…”

Section: N Americamentioning

confidence: 98%

Early deformation in the Caledonian-Appalachian orogen

Rast

Sturt

Harris

1988

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Summary Deformation isotopically dated at 1100–1000 Ma has been recorded in the Moine rocks of N Scotland and may be related to the latest stages of Grenville orogenesis of N America. Late Precambrian orogenesis is widely recorded in the dispersed fragments of Avalonia particularly in the eastern Appalachians, eastern Newfoundland and southern Britain. Localized evidence for late Cambrian-early Ordovician orogenesis is forthcoming in the Appalachians (Penobscot) in Scandinavia (Finnmarkian) and in Scotland and Ireland (Grampian).

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Section: N Americamentioning

confidence: 98%

Early deformation in the Caledonian-Appalachian orogen

Rast

Sturt

Harris

1988

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“…Lower Silurian strata near Calais, Maine, rest on Tremadoc beds, but there is little or no structural disparity between the rocks on each side of this contact (Osberg 1983). Some alkalic anorogenic pluton igneous activity involved the emplacement of the Cape Ann and Quincy granites in E Massachusetts during the Late Ordovician but there is no evidence for Taconian deformation (Skehan & Murray 1980).…”

Section: New England-new York Appalachiansmentioning

confidence: 99%

“…Interpretation of the deformational history in this area is further complicated by the effects of subsequent Acadian and/or Alleghenian deformation (Drake 1980). Radiometric data from rocks in this part of the Piedmont seem to favour early Palaeozoic but pre-Taconian (pre-480 Ma) deformation (Osberg 1983). Small granite bodies and associated pegmatites transect previously metamorphosed and multiply-deformed rocks in the Potomac River allochthon (Drake 1980) of the Glenarm Terrane near Washington, DC.…”

Section: Central Appalachiansmentioning

confidence: 99%

“…Although there may have been continuous deposition through the time of Taconian deformation in places in Maine, there is also evidence for Taconian deformation where Silurian rocks rest unconformably on Ashgill rocks. Osberg (1983) suggested that Penobscotian effects may be present southward along the Bronson Hill anticlinorium. Robinson (cited by Robinson & Hall 1980) identified a conglomerate at the base of the middle Ordovician Ammonoosuc volcanics in the Bronson Hill anticlinorium in Massachusetts which supports the interpretation that the Ammonoosuc and associated Partridge Formation probably unconformably overlie gneisses in the core of this anticlinorium (Thompson et al 1968).…”

Section: New England-new York Appalachiansmentioning

confidence: 99%

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Timing of Ordovician deformation in the Caledonian-Appalachian orogen

Hall¹,

Roberts²

1988

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Summary Evidence for Ordovician deformation is variably present throughout the Caledonides. The Grampian (late Cambrian-early Ordovician) and Taconian (middle to late Ordovician) major orogenies occurred during this time period and involved plutonism and metamorphism as well as deformation. The Taconian is particularly important in N America, whereas the Grampian (Penebscot), although locally identified, seems less important. Conversely, the Grampian appears to be more important in Scotland and in Scandinavia, where it is termed the Finnmarkian and constituted a major orogenic phase. Subduction and oceanic closure seems to have been an important Ordovician process, as indicated by abundant ophiolites. In Scandinavia the principal phase of thrust emplacement of the ophiolites occurred in the early to middle Ordovician. Major deformation in central E Greenland is of late Ordovician age.

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Disentangling Middle Paleozoic sea level and tectonic events in cratonic margins and cratonic basins of North America

Bond¹,

Kominz²

1991

J. Geophys. Res.

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The cratonic margins and basins of North America contain evidence of distinct changes in relative sea level, one of the most intriguing of which occurred in middle Paleozoic time. The change in relative sea level began in Frasnian time (Late Devonian) and continued through Visean time (Middle Mississippian) in the Cordilleran miogeocline, in the Southern Oklahoma Aulacogen, in the Appalachian miogeocline and in the Michigan, Illinois, and Williston basins. The synchroneity and wide geographic distribution of this event are striking and would seem to argue for an eustatic mechanism. An estimate of the middle Paleozoic sea level rise relative to the stable craton in Iowa suggests that while a large sea level rise occurred, it is smaller than the magnitude of subsidence in the cratonic basins and margins. Flexural foreland basin models do not appear to account for the all of the events in the cratonic margins, and thermal subsidence mechanisms do not seem appropriate for the subsidence in the cratonic basins. The middle Paleozoic stratigraphic record from the North American craton and its margins, therefore, poses a basic problem of identifying a mechanism for producing a large‐amplitude rise in sea level relative to the stable craton at the same time as a synchronous onset of tectonic subsidence in widespread basinal and marginal settings of diverse tectonic origin. One plausible mechanism for the tectonic subsidence in the basins and margins is a pulse of intraplate compressive stress. The origin of the large sea level rise relative to the stable craton could reflect an unusually large eustatic sea level change, but we cannot eliminate the possibility of a small component of subsidence or change in dynamic topography of the North American craton. The synchroneity of the sea level rise relative to the craton with the subsidence of basins and margins may be fortuitous, but it is also predicted by recent mantle convection models for the early stages of accretion of supercontinents.

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Timing of Orogenic Events in the U.S. Appalachians

Cited by 9 publications

References 29 publications

Early deformation in the Caledonian-Appalachian orogen

Early deformation in the Caledonian-Appalachian orogen

Timing of Ordovician deformation in the Caledonian-Appalachian orogen

Disentangling Middle Paleozoic sea level and tectonic events in cratonic margins and cratonic basins of North America

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