Mid-Paleozoic thrusting at the Appalachian deformation front: Port au Port Peninsula, western Newfoundland

1991 ◽  
Vol 28 (12) ◽  
pp. 1992-2002 ◽  
Author(s):  
John W. F. Waldron ◽  
Glen S. Stockmal
Keyword(s):  
Carbonate Platform ◽  
Foreland Basin ◽  
Late Ordovician ◽  
Western Boundary ◽  
Seismic Profiles ◽  
The West ◽  
Deformation Front ◽  
Middle Ordovician ◽  
Triangle Zone ◽  
Map Scale

Structures exposed on Port au Port Peninsula in western Newfoundland record the nature of the Appalachian deformation front, which forms the western boundary of the Humber tectono-stratigraphic zone. The major structures affect the Late Ordovician to Late Silurian Long Point – Clam Bank succession, but not the unconformably overlying Carboniferous rocks; they are probably of Devonian age.At the west coast of the peninsula, Long Point and Clam Bank strata are affected by both east-vergent and west-vergent structures. The basal surface of the succession is interpreted as an east-vergent thrust, forming the upper detachment of a "triangle zone," and correlates with a similarly located contact seen in offshore multichannel seismic profiles. Within the succession, east-vergent deformation zones locally duplicate the stratigraphy. West-vergent structures, including a map-scale overturned fold north of Round Head mountain, are probably younger.Farther south, Middle Ordovician foreland basin sediments are also affected by east-vergent thrusts, which have been variably rotated by west-vergent folds. In the underlying Cambrian–Ordovician platform carbonate succession, east-vergent thrusts duplicate the stratigraphy.These structures are related to telescoping of the carbonate platform and the overlying Humber Arm Allochthon during Devonian westward wedging of the structural triangle zone beneath the Long Point – Clam Bank succession. The platform succession must therefore be allochthonous, and the Humber Arm Allochthon has been transported to the west of its Late Ordovician position.

Basin development and inversion at the Appalachian structural front, Port au Port Peninsula, western Newfoundland Appalachians

1993 ◽  
Vol 30 (9) ◽  
pp. 1759-1772 ◽  
Author(s):  
John W. F. Waldron ◽  
Glen S. Stockmal ◽  
Randolph E. Corney ◽  
Sheila R. Stenzel
Keyword(s):  
Foreland Basin ◽  
Fault Scarp ◽  
Late Ordovician ◽  
The West ◽  
Western Basin ◽  
Middle Ordovician ◽  
Platform Carbonates ◽  
Palinspastic Restoration ◽  
And Inversion ◽  
Basin Boundaries

In the Humber Zone of the Newfoundland Appalachians, Cambro-Ordovician shelf and foreland basin successions are affected by Middle Ordovician (Taconian orogeny) and Devonian (Acadian orogeny) deformation. On Port au Port Peninsula the presence of the Late Ordovician to Late Silurian Long Point – Clam Bank succession allows these episodes to be separated. The Taconian foreland basin stratigraphy on Port au Port Peninsula is highly variable. On the west coast, platform carbonates are overlain by megaconglomerates of the Cape Cormorant Formation, which record progressive exposure of 1 km of the platform succession. The conglomerates are restricted to a narrow zone, consistent with derivation from a fault scarp originally immediately west of the outcrops (in palinspastic restoration). Farther east, at Victors Brook, the Cape Cormorant Formation is absent, but the overlying, almost undeformed Goose Tickle Group contains conglomerate derived both from the upper part of the platform succession and from the Taconian Humber Arm Allochthon. Southeast of Victors Brook, the top of the platform is overlain directly by scaly shales and mélange of the Humber Arm Allochthon, which includes deformed equivalents of the foreland basin succession. The distribution of conglomeratic units, the presence and configuration of faults, and the preservation of the Goose Tickle Group in the Victors Brook area imply that a fault-bounded basin developed in advance of the Humber Arm Allochthon during the Taconian orogeny. This basin is interpreted to have resulted from flexural extension of North American lithosphere. The close spatial coincidence between later Acadian structures and the Taconian basin boundaries implies that the basin-bounding faults were reactivated as thrusts and reverse faults, and that the basin underwent inversion during Acadian thrusting. The western basin-bounding fault, modified by the development of a "short cut" thrust, developed into the present-day Round Head thrust.

scholarly journals Provenance and paleogeography of post-Middle Ordovician, pre-Devonian sedimentary basins on the Gander composite terrane, eastern and east-central Maine: implications for Silurian tectonics in the northern Appalachians

2017 ◽  
Vol 53 ◽  
pp. 063-085 ◽  
Author(s):  
Allan Ludman ◽  
John T. Hopeck ◽  
Henry N. Berry IV
Keyword(s):  
Sedimentary Basins ◽  
Late Ordovician ◽  
The West ◽  
East Central ◽  
Early Devonian ◽  
Middle Ordovician ◽  
Regional Correlation ◽  
Orogenic Wedge ◽  
Connecticut Valley ◽  
Seismic Reflection Profiles

Recent mapping in eastern and east-central Maine addresses long-standing regional correlation issues and permits reconstruction of post-Middle Ordovician, pre-Devonian paleogeography of sedimentary basins on the Ganderian composite terrane. Two major Late Ordovician-Silurian depocenters are recognized in eastern Maine and western New Brunswick separated by an emergent Miramichi terrane: the Fredericton trough to the southeast and a single basin comprising the Central Maine and Aroostook-Matapedia sequences to the northwest. This Central Maine/Aroostook-Matapedia (CMAM) basin received sediment from both the Miramichi highland to the east and highlands and islands to the west, including the pre-Late Ordovician Boundary Mountains, Munsungun-Pennington, and Weeksboro-Lunksoos terranes. Lithofacies in the Fredericton trough are truncated and telescoped by faulting along its flanks but suggest a similar basin that received sediment from highlands to the west (Miramichi) and east (St. Croix).Deposition ended in the Fredericton trough following burial and deformation in the Late Silurian, but continued in the CMAM basin until Early Devonian Acadian folding. A westward-migrating Acadian orogenic wedge provided a single eastern source of sediment for the composite CMAM basin after the Salinic/Early Acadian event, replacing the earlier, more local sources. The CMAM, Fredericton, and Connecticut Valley-Gaspé depocenters were active immediately following the Taconian orogeny and probably formed during extension related to post-Taconian plate adjustments. These basins thus predate Acadian foreland sedimentation.Structural analysis and seismic reflection profiles indicate a greater degree of post-depositional crustal shortening than previously interpreted. Late Acadian and post-Acadian strike-slip faulting on the Norumbega and Central Maine Boundary fault systems distorted basin geometries but did not disturb paleogeographic components drastically.

The Ordovician brachiopod genus Bimuria from the eastern Klamath Mountains, northern California

1990 ◽  
Vol 64 (2) ◽  
pp. 200-213 ◽  
Author(s):  
A. W. Potter
Keyword(s):  
Northern Ireland ◽  
Late Ordovician ◽  
Yukon Territory ◽  
Preliminary Survey ◽  
Northern California ◽  
Klamath Mountains ◽  
The West ◽  
East Central ◽  
Middle Ordovician ◽  
Southwestern Siberia

The genus Bimuria Ulrich and Cooper, 1942, is a biogeographically important member of middle and late Ordovician brachiopod faunas of the Callahan–Gazelle area in the eastern Klamath Mountains of northern California. In middle Ordovician deposits the genus is widespread and ranges from Nevada in the west to southwestern Siberia in the east; however, in late Ordovician beds it was previously known only in Sweden and Northern Ireland. In addition to the northern California occurrence reported here, new late Ordovician occurrences are also noted in east-central Alaska–Yukon Territory and Northwest Territories. Three species of Bimuria are described, including the new species, B. californiensis.A preliminary survey of species described in the literature suggests that the ratio of the length of the dorsal adductor field to the length of the elongate area in the brachial valve decreases from middle to late Ordovician species, and thus may be of biostratigraphic value.

Origin of the Odd-twins anomaly: magnetic effect of a unique stratigraphic marker in the Appalachian foreland basin, Gulf of St. Lawrence

2002 ◽  
Vol 39 (11) ◽  
pp. 1675-1687 ◽  
Author(s):  
John WF Waldron ◽  
Jerry DeWolfe ◽  
Robert Courtney ◽  
Doris Fox
Keyword(s):  
Point Group ◽  
Foreland Basin ◽  
Late Ordovician ◽  
Magnetic Survey ◽  
Seismic Profiles ◽  
Mineral Concentration ◽  
Appalachian Orogen ◽  
Land Survey ◽  
Laurentian Margin ◽  
Appalachian Foreland

The "Odd-twins magnetic anomaly" is a pair of linear asymmetric positive anomalies located in the Gulf of St. Lawrence, over the post-Taconian, pre-Acadian foreland basin fill related to the development of the Appalachians. A marine magnetic survey allowed the anomaly to be traced close to the coast of Newfoundland, and an on-land survey identified both peaks within the area of outcrop of the Late Ordovician Long Point Group. Sandstones of high susceptibility sampled from sparse outcrops close to the locations of the anomaly peaks contain up to 0.58% magnetite. Models involving dipping sheets of sandstone having similar and slightly higher susceptibility can explain both the onshore and offshore anomaly. The magnetite is of detrital origin and represents a paleoplacer heavy mineral concentration formed in a marginal marine environment. The anomaly provides a unique tie point between the known onshore stratigraphy and the succession in the foreland basin, known only from industry seismic profiles. This tie point indicates that nearly half of the recorded subsidence of the post-Taconian foreland basin took place in the Late Ordovician, suggesting that a major event within the Appalachian orogen loaded the Laurentian margin at this time. A subsequent hiatus, representing the Early Silurian, may record thermal uplift associated with the Salinian orogeny. Renewed Late Silurian to Devonian loading and sedimentation resulted from the Acadian orogeny.

The tectonics and depositional history of the Ordovician and Silurian rocks of Notre Dame Bay, Newfoundland

1985 ◽  
Vol 22 (4) ◽  
pp. 607-618 ◽  
Author(s):  
R. J. Arnott ◽  
W. S. McKerrow ◽  
L. R. M. Cocks
Keyword(s):  
Strike Slip ◽  
Late Ordovician ◽  
Island Arc ◽  
The West ◽  
Depositional History ◽  
Middle Ordovician ◽  
The North ◽  
Lower Ordovician ◽  
History Of ◽  
Ophiolitic Rocks

In the Notre Dame Bay region, ophiolitic rocks underlie a thick sequence of Lower Ordovician volcanic-arc rocks to the north of the Lobster Cove – Chanceport Fault. Neither this fault nor the Lukes Arm – Sops Head Fault shows evidence of very large strike-slip movements, as parts of the same arc, together with much arc-derived detritus, straddle both faults. Towards the east, this arc-derived detritus becomes more distal in aspect and passes laterally into the Dunnage Mélange. During the Middle Ordovician Epoch (late Llandeilo and early Caradoc), most areas show a marked decrease in volcanic activity and in the amount of coarse detritus deposited. Coarse turbidites reappear, at different times in different areas, during the Late Ordovician. These are related to several fault-bounded basins and to movements on the Lukes Arm – Sops Head Fault. Many of these faults, particularly in the east, are marked by olistostromes, several of which can be dated by fossils as Late Ordovician and Early Silurian. The whole region, between the Reach Fault on the east and the Baie Verte – Brompton Line on the west, has a stratigraphic unity. If it has been moved by strike slip relative to the Long Range, then any such fault must lie to the west of the Baie Verte – Brompton Line. The interpretation of an Early Ordovician island arc moving above an easterly directed subduction zone is in accord with both the geochemical and palaeontological evidence. The Notre Dame Bay region may have been converted into a transform-dominated margin in the Late Ordovician and Early Silurian in a manner analogous to the oblique slip tectonic regimes of the Californian and New Zealand margins during the Tertiary, with a precursor of the Reach Fault marking the edge of the continent after the Notre Dame island arc had collided with North America.

Darriwilian graptolites of the Hamburg succession (Dauphin Formation), Pennsylvania, and their geologic significance

2005 ◽  
Vol 42 (5) ◽  
pp. 791-813 ◽  
Author(s):  
G Robert Ganis
Keyword(s):  
Foreland Basin ◽  
Late Ordovician ◽  
Middle Ordovician ◽  
Taconic Orogeny ◽  
Age Range

Graptolites from the Dauphin Formation in the allochthonous Hamburg succession of the Appalachians in Pennsylvania, USA, are late Darriwilian (Da) 3 to early Da 4 age (Middle Ordovician); this age range constrains the timing of the latest depositional episode before the terrane was tectonically mobilized. These rocks were emplaced into the Martinsburg foreland basin of Laurentia during the Taconic orogeny in the early Caradoc (Late Ordovician). Nineteen taxa are described defining a narrow biostratigraphic interval. Among the characteristic fauna collected from of the Da 4 Zone are Pterograptus elegans Holm, Cryptograptus schaeferi Lapworth, Hustedograptus teretiusculus (Hisinger) ?, Haddingograptus oliveri (Bouček), Glossograptus hincksii (Hopkinson), Pseudophyllograptus angustifolius s.l. (J. Hall), and Archiclimacograptus cf. riddellensis (Harris). Tetragraptus cf. erectus Mu et al. found with the above suggests a level low in the Da 4 Zone and a limited occurrence of Bergstromograptus crawfordi (Harris) may indicate some strata within the Da 3 Zone. Proposed new forms include Pseudotrigonograptus ? ricardo sp. nov., and at least two reteograptids. Four examples of Kalpinograptus and Kalpinograptus ? may be new.

Carbonate platform to foreland basin: revised stratigraphy of the Table Head Group (Middle Ordovician), western Newfoundland

1990 ◽  
Vol 27 (1) ◽  
pp. 14-26 ◽  
Author(s):  
Sheila R. Stenzel ◽  
Ian Knight ◽  
Noel P. James
Keyword(s):  
Carbonate Platform ◽  
Foreland Basin ◽  
Black Shales ◽  
Head Group ◽  
Western Margin ◽  
Middle Ordovician ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Three Stages ◽  
Uplift And Erosion

Carbonates of the Table Head Group and associated strata were deposited along the western margin of a foreland basin during initial stages of the Taconian Orogeny and record collapse and cannibalization of a long-lived carbonate platform. The stratigraphy of Klappa, Opalinski, and James is here revised to reflect better understanding of lithologic units within this complex tectono-stratigraphic assemblage. The Table Head Group now contains only three formations: the Table Point and Table Cove formations, as originally defined, and the Cape Cormorant Formation, redefined and restricted to western Port au Port Peninsula. Black Cove Formation shales are removed from the Table Head. Distinctive conglomerates once placed in the Cape Cormorant are now recognized as separate units within the overlying flysch and called the Daniel's Harbour Member.The foreland basin developed in three stages: (1) fragmentation, uplift, and erosion of the platform and subsequent deposition of shallow-water limestones (Table Point) on a tectonically unstable shelf; (2) foundering of platform blocks and deposition of deep-water-slope carbonates (Table Cove), basinal black shales (Black Cove), or conglomerates of older shelf carbonates shed from submarine cliffs (Cape Cormorant); and (3) siliciclastic sedimentation interrupted by sediment gravity flows of Table Head clasts shed from submarine escarpments (Daniel's Harbour).

Nucularcidae: a new family of palaeotaxodont Ordovician pelecypods (Mollusca) from North America and Australia

2007 ◽  
Vol 44 (10) ◽  
pp. 1479-1501 ◽  
Author(s):  
John Pojeta Jr. ◽  
Christopher A Stott
Keyword(s):  
New Species ◽  
Type Species ◽  
New Genus ◽  
Late Ordovician ◽  
Eastern Canada ◽  
Middle Ordovician ◽  
New Family ◽  
Central Australia ◽  
Northeastern Usa ◽  
Subjective Synonym

The new Ordovician palaeotaxodont family Nucularcidae and the new genus Nucularca are described. Included in Nucularca are four previously described species that have taxodont dentition: N. cingulata (Ulrich) (the type species), N. pectunculoides (Hall), N. lorrainensis (Foerste), and N. gorensis (Foerste). All four species are of Late Ordovician (Cincinnatian Katian) age and occur in eastern Canada and the northeastern USA. Ctenodonta borealis Foerste is regarded as a subjective synonym of Nucularca lorrainensis. No new species names are proposed. The Nucularcidae includes the genera Nucularca and Sthenodonta Pojeta and Gilbert-Tomlinson (1977). Sthenodonta occurs in central Australia in rocks of Middle Ordovician (Darriwilian) age. The 12 family group names previously proposed for Ordovician palaeotaxodonts having taxodont dentition are reviewed and evaluated in the Appendix.

Middle Ordovician Table Head Group of western Newfoundland: a revised stratigraphy

1980 ◽  
Vol 17 (8) ◽  
pp. 1007-1019 ◽  
Author(s):  
Colin F. Klappa ◽  
Paul R. Opalinski ◽  
Noel P. James
Keyword(s):  
Carbonate Platform ◽  
Head Group ◽  
Group Status ◽  
Middle Ordovician ◽  
Iapetus Ocean ◽  
Lower Ordovician ◽  
Head Formation ◽  
New Formation

Lithostratigraphic nomenclature of early Middle Ordovician strata from western Newfound land is formally revised. The present Table Head Formation is raised to group status and extended to include overlying interbedded terrigenoclastic-rich calcarenites and shales with lime megabreccias. Four new formation names are proposed: Table Point Formation (previously lower Table Head); Table Cove Formation (previously middle Table Head); Black Cove Formation (previously upper Table Head); and Cape Cormorant Formation (previously Caribou Brook formation). The Table Point Formation comprises bioturbated, fossiliferous grey, hackly limestones and minor dolostones; the Table Cove Formation comprises interbedded lime mudstones and grey–black calcareous shales; the Black Cove Formation comprises black graptolitic shales; and the Cape Cormorant Formation comprises interbedded terrigenoclastic and calcareous sandstones, siltstones, and shales, punctuated by massive or thick-bedded lime megabreccias. The newly defined Table Head Group rests conformably or disconformably on dolostones of the Lower Ordovician St. George Group (an upward-migrating diagenetic dolomitization front commonly obscures the contact) and is overlain concordantly by easterly-derived flysch deposits. Upward-varying lithologic characteristics within the Table Head Group result from fragmentation and subsidence of the Cambro-Ordovician carbonate platform and margin during closure of a proto-Atlantic (Iapetus) Ocean.

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