DEPOSITION OF OOID SHOALS MARGINAL TO THE LATE CAMBRIAN PROTO-ATLANTIC (IAPETUS) OCEAN IN NEW YORK AND ALABAMA; INFLUENCE ON THE INTERIOR SHELF

1984 ◽  
pp. 2-19 ◽  
Author(s):  
LINDA RAINE STERNBACH ◽  
GERALD M. FRIEDMAN
Keyword(s):  
New York ◽  
Late Cambrian ◽  
Iapetus Ocean

scholarly journals Reconstruction of the enigmatic Late Cambrian Climactichnites

1992 ◽  
Vol 6 ◽  
pp. 321-321 ◽  
Author(s):  
E.L. Yochelson ◽  
M. Parrish
Keyword(s):  
New York ◽  
Cross Section ◽  
Individual Variation ◽  
Short Distance ◽  
Loose Sand ◽  
Desiccation Cracks ◽  
Late Cambrian ◽  
Anterior Flap ◽  
Considerable Individual Variation ◽  
Early Late

Climactichnites Logan, 1860, is known only from its large trail up to 20 cm in width, a trace superficially resembling a rope ladder. Prominent lateral ridges are parallel throughout the length of the trail; they may be smooth and hemispherical in cross-section or crenulated, much like a pie crust. Between these ridges is a series of raised dune-like bars and furrows dug into the substrate. The bars and furrows show considerable individual variation between trails and also variation along a trail. Ovoid impressions are known which occur at the start of trails. The posterior of these impressions is well rounded; the anterior is triangular, and for a short distance from the impression, the trail is developed on only one side. One exceptionally preserved impression shows curved, closely spaced, fine lines parallel to the posterior.The trails are found only in sandstone, and where they are present, they are abundant. Slightly equivocable evidence indicates a Dresbachian (early Late Cambrian) age for the occurrences in New York, Missouri, and Wisconsin; trails in Ontario and Quebec are less certainly dated. Desiccation cracks and air escape hole suggest that the trail was fully exposed to the atmosphere.From this data, a large number of sketches were made to reconstruct an animal able to make such a trail. Each attempt produced new speculation on the morphology. In the final rendition, the animal is bilaterally symmetrical, broad and low. The integument is tough, and the sole bears a subcentral mouth anteriorward. Lateral flaps scraped and compressed damp sand to make the parallel ridges. The anterior was strongly musculated and thin. This anterior flap grasped the sediment, alternating on either side of the animal to pull the form forward when the lateral flaps were relaxed. Curved rows of cilia on the posterior moved loose sand into dunes between the furrows formed by the anterior flaps.This reconstruction is like that of no other animal known in the Vendian or the Phanerozoic.

scholarly journals Suprasubduction zone ophiolite fragments in the central Appalachian orogen: Evidence for mantle and Moho in the Baltimore Mafic Complex (Maryland, USA)

Geosphere ◽  
2021 ◽  
Author(s):  
George L. Guice ◽  
Michael R. Ackerson ◽  
Robert M. Holder ◽  
Freya R. George ◽  
Joseph F. Browning-Hanson ◽  
...  
Keyword(s):  
New York ◽  
Tectonic Evolution ◽  
Mineral Chemistry ◽  
Bulk Rock ◽  
Suprasubduction Zone ◽  
Tectonic Processes ◽  
Iapetus Ocean ◽  
Mantle Peridotites ◽  
Mafic Complex ◽  
Appalachian Orogen

Suprasubduction zone (SSZ) ophiolites of the northern Appalachians (eastern North America) have provided key constraints on the fundamental tectonic processes responsible for the evolution of the Appalachian orogen. The central and southern Appalachians, which extend from southern New York to Alabama (USA), also contain numerous ultra- mafic-mafic bodies that have been interpreted as ophiolite fragments; however, this interpretation is a matter of debate, with the origin(s) of such occurrences also attributed to layered intrusions. These disparate proposed origins, alongside the range of possible magmatic affinities, have varied potential implications for the magmatic and tectonic evolution of the central and southern Appalachian orogen and its relationship with the northern Appalachian orogen. We present the results of field observations, petrography, bulk-rock geochemistry, and spinel mineral chemistry for ultramafic portions of the Baltimore Mafic Complex, which refers to a series of ultramafic-mafic bodies that are discontinuously exposed in Maryland and southern Pennsylvania (USA). Our data indicate that the Baltimore Mafic Complex comprises SSZ ophiolite fragments. The Soldiers Delight Ultramafite displays geochemical characteristics—including highly depleted bulk-rock trace element patterns and high Cr# of spinel—characteristic of subduction-related mantle peridotites and serpentinites. The Hollofield Ultramafite likely represents the “layered ultramafics” that form the Moho. Interpretation of the Baltimore Mafic Complex as an Iapetus Ocean–derived SSZ ophiolite in the central Appalachian orogen raises the possibility that a broadly coeval suite of ophiolites is preserved along thousands of kilometers of orogenic strike.

Stratigraphy and lithogeochemistry of rocks from the Nugget Pond Deposit area, Baie Verte Peninsula, Newfoundland

2021 ◽  
Author(s):  
C Mueller ◽  
S J Piercey ◽  
M G Babechuk ◽  
D Copeland
Keyword(s):  
Gold Mineralization ◽  
Sedimentary Rocks ◽  
Mafic Rocks ◽  
Basaltic Rocks ◽  
Late Cambrian ◽  
Lower Unit ◽  
Iapetus Ocean ◽  
Post Archean Australian Shale ◽  
Clastic Sedimentary ◽  
Ocean Ridge

Stratigraphic and lithogeochemical data were collected from selected drill core from the Nugget Pond gold deposit in the Betts Cove area, Newfoundland. The stratigraphy consists of a lower unit of basaltic rocks that are massive to pillowed (Mount Misery Formation). This is overlain by sedimentary rocks of the Scrape Point Formation that consist of lower unit of turbiditic siltstone and hematitic cherts/iron formations (the Nugget Pond member); the unit locally has a volcaniclastic rich-unit at its base and grades upwards into finer grained volcaniclastic/turbiditic rocks. This is capped by basaltic rocks of the Scrape Point Formation that contain pillowed and massive mafic flows that are distinctively plagioclase porphyritic to glomeroporphyritic. The mafic rocks of the Mount Misery Formation have island arc tholeiitic affinities, whereas Scrape Point Formation mafic rocks have normal mid-ocean ridge (N-MORB) to backarc basin basalt (BABB) affinities. One sample of the latter formation has a calc-alkalic affinity. All of these geochemical features are consistent with results and conclusions from previous workers in the area. Clastic sedimentary rocks and Fe-rich sedimentary rocks of the Scrape Point Formation have features consistent with derivation from local, juvenile sources (i.e., intra-basinal mafic rocks). The Scrape Point Formation sedimentary rocks with the highest Fe/Al ratios, inferred to have greatest amount of hydrothermally derived Fe, have positive Ce anomalies on Post-Archean Australian Shale (PAAS)-normalized trace element plots. These features are consistent with having formed via hydrothermal venting into an anoxic/ sub-oxic water column. Further work is needed to test whether these redox features are a localized feature (i.e., restricted basin) or a widespread feature of the late Cambrian-early Ordovician Iapetus Ocean, as well as to delineate the role that these Fe-rich sedimentary rocks have played in the localization of gold mineralization within the Nugget Pond deposit.

Palaeo-oceanography and biogeography in the Tremadoc (Ordovician) Iapetus Ocean and the origin of the chemostratigraphy of Dictyonema flabelliforme black shales

1989 ◽  
Vol 126 (1) ◽  
pp. 19-27 ◽  
Author(s):  
P. Wilde ◽  
M. S. Quinby-Hunt ◽  
W. B. N. Berry ◽  
C. J. Orth
Keyword(s):  
New York ◽  
New Brunswick ◽  
Hydrothermal Activity ◽  
Black Shales ◽  
Elemental Content ◽  
Geochemical Signature ◽  
Iapetus Ocean ◽  
Saint John ◽  
High Concentrations ◽  
Major Surface

AbstractHigh concentrations of vanadium, molybdenum, uranium, arsenic, antimony with low concentrations of manganese, iron and cobalt heretofore restricted to Dictyonema flabelliforme-bearing Tremadoc black shales in Balto-Scandia, have been found in coeval black shales in the Saint John, New Brunswick area. Prior palaeogeographic reconstructions place these areas about 400 km. apart in high southern latitudes in the Iapetus Ocean, with New Brunswick in proximity to Avalonia (southeastern Newfoundland). These geochemical similarities are not found in coeval Tremadoc black shales of Bolivia, New York, Quebec, Wales, and Belgium. Palaeo-oceanographic reconstructions of Iapetus support the proximity of Balto-Scandia and the Saint John area during the early Tremadoc and Gee'sx (1981) suggestion that the signature is a feature of eastern Iapetus. Furthermore, first-order modelling of the major surface currents and related primary productivity in the Tremadoc Iapetus Ocean explain the apparent wide latitudinal range of D. flabelliforme (Fortey, 1984) and the anomalous trace metal content of certain black shales of that time. Variations in the elemental content of these black shales is produced by oceanographic and geologic conditions unique to the geographic site. The distinctive Balto-Scandic geochemical signature resulted from the coincidence of anoxic waters transgressing the shelf at latitudes of high organic productivity at the polar Ekman planetary divergence. This produces the conditions for concentrations of V, U, and Mo in the shales. Metal enriched anoxic bottom waters produced by leaching of volcanics or through hydrothermal activity may be the source of the other enhanced signature elements such as As and Sb. The absence of this geochemical signature in younger non-D. flabelliforme Tremadoc and later black shales in Balto-Scandia and other areas suggests that the closing of Iapetus moved the depositional sites into less productive oceanic areas.

Chapter 19 Regional context and tectonostratigraphic framework of the early–middle Paleozoic Caledonide orogen, northwestern Sweden

2020 ◽  
Vol 50 (1) ◽  
pp. 481-494 ◽  
Author(s):  
David G. Gee ◽  
Michael B. Stephens
Keyword(s):  
Foreland Basin ◽  
Metasedimentary Rocks ◽  
Mafic Intrusions ◽  
Late Cambrian ◽  
Iapetus Ocean ◽  
Nappe Complex ◽  
Middle Paleozoic ◽  
Thrust Sheets ◽  
Seve Nappe Complex ◽  
Augen Gneiss

AbstractThe Scandian mountains in northwestern Sweden are dominated by the eastern part of the Scandinavian Caledonides, an orogen that terminated during the middle Paleozoic with Himalayan-style collision of the ancient continents of Baltica and Laurentia. In this foreland region, far-transported higher allochthons from an exotic continental margin (Rödingsfjället Nappe Complex) and underlying mostly oceanic-arc basin character (Köli Nappe Complex) were emplaced at least 700 km onto the Baltoscandian margin of Baltica. The thrust sheets below the Iapetus Ocean terranes were derived from the transition zone to Baltica (Seve Nappe Complex), comprising mainly siliciclastic metasedimentary rocks, hosting abundant metamorphosed c. 600 Ma mafic intrusions. They preserve evidence of subduction (eclogites, garnet peridotites and microdiamonds in host paragneisses), starting in the late Cambrian; exhumation continued through the Ordovician. Underlying allochthons derived from the outer margin of Baltica are less-metamorphosed Neoproterozoic sandstone-dominated successions, also intruded by Ediacaran dolerite dykes (Särv Nappes); they are located tectonically above similar-aged metasandstone and basement slices, devoid of dykes (Offerdal and Tännäs Augen Gneiss nappes and equivalents). Lowermost allochthons (Jämtlandian Nappes and equivalents), from the inner Baltoscandian margin, provide evidence of Cryogenian rifting, Ediacaran–Cambrian drifting and platformal sedimentation, followed by foreland basin development in the Ordovician and Silurian.

scholarly journals Evidence for a late Cambrian juvenile arc and a buried suture within the Laurentian Caledonides of Scotland: Comparisons with hyperextended Iapetan margins in the Appalachian Mountains (North America) and Norway

Geology ◽  
2019 ◽  
Vol 47 (8) ◽  
pp. 734-738 ◽  
Author(s):  
M. Dunk ◽  
R.A. Strachan ◽  
K.A. Cutts ◽  
S. Lasalle ◽  
C.D. Storey ◽  
...  
Keyword(s):  
Appalachian Mountains ◽  
Calc Alkaline ◽  
Passive Margins ◽  
Late Cambrian ◽  
Iapetus Ocean ◽  
Mineral Assemblages ◽  
Thrust Sheets ◽  
Late Neoproterozoic ◽  
Laurentian Margin ◽  
Tectonic Slice

Abstract Uranium-lead (U-Pb) zircon dating establishes a late Cambrian (Drumian) protolith age of 503 ± 2 Ma for a trondhjemitic gneiss of the calc-alkaline Strathy Complex, northern Scottish Caledonides. Positive εHf and εNd values from trondhjemitic gneisses and co-magmatic amphibolites, respectively, and an absence of any inheritance in zircon populations support published geochemistry that indicates a juvenile origin distal from Laurentia. In order to account for its present location within a stack of Laurentia-derived thrust sheets, we interpret the complex as allochthonous and located along a buried suture. We propose that a microcontinental ribbon was detached from Laurentia during late Neoproterozoic to Cambrian rifting; the intervening oceanic tract closed by subduction during the late Cambrian and formed a juvenile arc, the protolith of the Strathy Complex. The microcontinental ribbon was reattached to Laurentia during the Grampian orogeny, which transported the Strathy Complex as a tectonic slice within a nappe stack. Peak metamorphic conditions for the Strathy Complex arc (650–700 °C, 0.6–0.75 GPa) are intermediate in pressure between those published previously for Grampian mineral assemblages in structurally overlying low-pressure migmatites (670–750 °C, <0.4 GPa) that we deduce to have been derived from an adjacent backarc basin, and structurally underlying upper amphibolite rocks (650–700 °C, 1.1–1.2 GPa) that we interpret to represent the partially subducted Laurentian margin. This scenario compares with that of the northern Appalachian Mountains and Norway where microcontinental blocks are interpreted to have their origins in detachment from passive margins of the Iapetus Ocean during Cambrian rifting and to have been re-amalgamated during Caledonian orogenesis.

Epeirogenic transgression near a triple junction: the oldest (latest early–middle Cambrian) marine onlap of cratonic New York and Quebec

2009 ◽  
Vol 146 (4) ◽  
pp. 552-566 ◽  
Author(s):  
ED LANDING ◽  
LISA AMATI ◽  
DAVID A. FRANZI
Keyword(s):  
New York ◽  
Triple Junction ◽  
Early Cambrian ◽  
Normal Faulting ◽  
Cooling History ◽  
Middle Cambrian ◽  
Iapetus Ocean ◽  
Rapid Accumulation ◽  
Late Stages ◽  
Middle Proterozoic

AbstractThe discovery of a fossiliferous interval (Altona Formation, new unit) under the Potsdam Formation requires a new geological synthesis of a large part of the northeast Laurentian craton. Potsdam sandstones can no longer be regarded as the oldest sedimentary unit on the middle Proterozoic Grenville orogen in northern New York and adjacent Quebec and Ontario. The thickest Potsdam sections (to 750 m) in the east Ottawa–Bonnechere aulocogen have been explained by deposition with normal faulting possibly associated with Ediacaran rifting (c. 570 Ma) that led to formation of the Iapetus Ocean. However, sparse trilobite faunas show a terminal early Cambrian–middle middle Cambrian age of the Altona, and indicate much later marine transgression (c. 510 Ma) of the northeast Laurentian craton. Altona deposition was followed by rapid accumulation of lower Potsdam (Ausable Member) sandstone in the middle–late middle Cambrian. The Altona–Ausable succession is probably conformable. The Altona is a lower transgressive systems tract unit deposited on the inner shelf (sandstone, reddish mudstone, and carbonates) followed by aggradation and the deposition of highstand systems tract, current cross-bedded, in part terrestrial(?), feldspathic Ausable sandstone. Unexpectedly late Altona transgression and rapid Ausable deposition may reflect renewed subsidence in the Ottawa–Bonnechere aulocogen with coeval (terminal early Cambrian) faulting that formed the anoxic Franklin Basin on the Vermont platform. Thus, the oldest cover units on the northeast New York–Quebec craton record late stages in a cooling history near an Ediacaran triple junction defined by the Quebec Reentrant and New York Promontory and the Ottawa–Bonnechere aulocogen.

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