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.

An enigmatic blastozoan echinoderm fauna from central kentucky

2009 ◽  
Vol 83 (5) ◽  
pp. 739-749 ◽  
Author(s):  
Colin D. Sumrall ◽  
Carlton E. Brett ◽  
Troy A. Dexter ◽  
Alexander Bartholomew
Keyword(s):  
North America ◽  
Northwest Territories ◽  
Middle Devonian ◽  
Fossil Record ◽  
Foreland Basin ◽  
Late Ordovician ◽  
Upper Devonian ◽  
Range Extension ◽  
First Report ◽  
Appalachian Foreland

A series of small road cuts of lower Boyle Formation (Middle Devonian: Givetian) near Waco, Kentucky, has produced numerous specimens of three blastozoan clades, including both “anachronistic” diploporan and rhombiferan “cystoids” and relatively advanced Granatocrinid blastoids. This unusual assemblage occurs within a basal grainstone unit of the Boyle Limestone, apparently recording a local shoal deposit. Diploporans, the most abundant articulated echinoderms, are represented by a new protocrinitid species, Tristomiocystis globosus n. gen. and sp. Glyptocystitoid rhombiferans are represented by isolated thecal plates assignable to Callocystitidae. Three species of blastoids, all previously undescribed, include numerous thecae of the schizoblastid Hydroblastus hendyi n. gen. and sp., the rare nucleocrinid Nucleocrinus bosei n. sp., and an enigmatic troosticrinid radial. The blastoid Nucleocrinus is typical for the age; however, the callocystitid, schizoblastid, and protocrinitid are not. Hydroblastus is the oldest known schizoblastid. Middle and Upper Devonian callocystitids have been previously reported only from Iowa and Michigan USA with unpublished reports from Missouri USA and the Northwest Territories, Canada. This occurrence is thus the first report of a Middle Devonian rhombiferan from the Appalachian foreland basin. Tristomiocystis is the first known protocrinitid in North America and the only protocrinitid younger than Late Ordovician. This occurrence thus represents a range extension of nearly 50 million years for protocrinids. This extraordinary sample of echinoderms in a Middle Devonian limestone from a well-studied area of North America highlights the incompleteness of the known fossil record, at least in fragile organisms such as echinoderms.

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.

Platform drowning leading to cool-water carbonate deposition: evolution of a Late Ordovician (Turinian–Chatfieldian) mixed-sediment platform within the Taconic orogen (Long Point Group, Newfoundland Appalachians)

2018 ◽  
Vol 55 (9) ◽  
pp. 1036-1062 ◽  
Author(s):  
George R. Dix ◽  
Elliott T. Burden
Keyword(s):  
Point Group ◽  
High Energy ◽  
Late Ordovician ◽  
Coarse Grained ◽  
Carbonate Production ◽  
Cool Water ◽  
Platform Drowning ◽  
Mixed Sediment ◽  
Laurentian Margin ◽  
Water Carbonate

Late Ordovician (Turinian–Chatfieldian) drowning of a mixed carbonate–siliciclastic platform within the Taconic Orogen (Newfoundland Appalachians) is recorded by net deepening of an initial warm, shallow-water platform succession (Lourdes Formation) culminating in a metre-scale thick condensed interval that characterizes a drowning succession punctuated by storm deposits. Composition of transported material suggests that seaward drowning was coupled with back-stepping of a high-energy carbonate factory related to hinterland uplift and erosion that would eventually lead to drowning of the outer platform beneath marine-transported siliciclastic sediments (Winterhouse Formation). In the new offshore shelf setting, a sparse reciprocal stratigraphy of fine- to very coarse-grained phosphatic carbonate and mixed sediment is interpreted to document gravity-flow deposition downgradient from either a sustained or episodically developed high-energy cool-water carbonate source along the inner shelf. Transported carbonate was cemented rapidly at temperatures no warmer than 16 °C–23 °C, possibly within a seasonal oceanic thermocline. An upsection decrease in abundance of carbonate by the early Edenian is associated with a dramatic increase in siliciclastic supply. The Turinian–Edenian succession of platform drowning, oceanographic transition to cool-water carbonate production, and, later, its termination by increased siliciclastic supply reflects a first-order tectonic control proximal to uplift within the Taconic Orogen. Similar structural and oceanographic changes along the contemporary distal Laurentian margin provides the basis, with improved biostratigraphic control, for future analysis of the significance of proximal–distal stratigraphies in response to regional foreland tectonism.

scholarly journals Application of Foreland Basin Detrital‐Zircon Geochronology to the Reconstruction of the Southern and Central Appalachian Orogen

2010 ◽  
Vol 118 (1) ◽  
pp. 23-44 ◽  
Author(s):  
Hyunmee Park ◽  
David L. Barbeau Jr. ◽  
Alan Rickenbaker ◽  
Denise Bachmann‐Krug ◽  
George Gehrels
Keyword(s):  
Detrital Zircon ◽  
Foreland Basin ◽  
Zircon Geochronology ◽  
Detrital Zircon Geochronology ◽  
Appalachian Orogen

Westward propagation of thrusts in the external Western Alps (France) reappraised from an updated chronostratigraphy of the Miocene Molasses

2021 ◽  
Author(s):  
Amir Kalifi ◽  
Philippe-Hervé Leloup ◽  
Philippe Sorrel ◽  
Albert Galy ◽  
François Demory ◽  
...  
Keyword(s):  
Multidisciplinary Approach ◽  
Foreland Basin ◽  
Western Alps ◽  
Seismic Profiles ◽  
Stratigraphic Framework ◽  
Basin Scale ◽  
Deformation Kinematics ◽  
Westward Migration ◽  
External Part ◽  
Tectonics And Sedimentation

<p>The fact that the western Alps Miocene foreland basin succession is poorly dated impacts directly our understanding of the deformation kinematics of that part of the external part of the Alpine belt (France). Here we propose a multidisciplinary approach aiming at building a robust tectono-stratigraphic framework of the Miocene deposits at the basin scale (northern subalpine massifs, southern Jura, Royans, Bas-Dauphiné and La Bresse basins). Sr isotopes stratigraphy combined with magnetostratigraphy and biostratigraphy enable sequence stratigraphy subdivisions S1 to S8 between the Upper Aquitanian (-21 Ma) and the Tortonian (-9 Ma) dated with a precision <0.5 Ma. These results highlight four different palaeogeographical domains during the Miocene: (i) the oriental domain with depositional sequences S1a to S3 (~21.3 to 15Ma), (ii) the median domain, in which sequences S2, S3, S4 and S5 occurred (~17.8 to 14Ma), (iii) the occidental domain with sequences S2 to S8 (~17.8 to ~9.5Ma); and (iv) the Bressan domain, in which sequences S6 to S8 are found (~ 11.5 to ~9.5Ma).</p><p>This revised chronostratigraphy was complemented with a structural and tectono-sedimentary study based on new fieldwork data and a reappraisal of regional seismic profiles, allowing to highlight five major faults zones (FZ). It appears that the oriental, median and occidental paleogeographical domains are delineated by FZ1, FZ2 and FZ3, therefore suggesting a strong interplay between tectonics and sedimentation. Evidences of syntectonic deposits and a westward migration of the depocenters impart the following deformation chronology : a Oligocene compressive phase (P1) corresponding to thrusting above FZ1 rooted east (above) Belledonne, which generated reliefs that limited the early Miocene transgression to the east; an Early- to Middle Miocene W-WNW/E-ESE-directed compressive phase (P2) involving the Belledonne massif basal thrust, which between 18.05 +/- 0.15 Ma and 12Ma successively activated the Salève thrust fault, and the FZ2 to FZ5 from east to west. P2 deeply impacted the Miocene palaeogeographical evolution by a rapid westward migration of depocenters in response to the exhumation of piggy-back basins above the growing fault zones; a last Tortonian phase (P3), less well constrained, apparently implied a significant uplift in the subalpine massifs, combined with the activation of the frontal Jura thrust.</p>

scholarly journals Multimineral Fingerprinting of Transhimalayan and Himalayan Sources of Indus-Derived Thal Desert Sand (Central Pakistan)

Minerals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 457 ◽  
Author(s):  
Wendong Liang ◽  
Eduardo Garzanti ◽  
Sergio Andò ◽  
Paolo Gentile ◽  
Alberto Resentini
Keyword(s):  
Relative Proportion ◽  
Foreland Basin ◽  
Sediment Supply ◽  
Heavy Mineral ◽  
Mineral Species ◽  
Provenance Analysis ◽  
Indus River ◽  
Mineral Concentration ◽  
River Sand ◽  
Desert Sand

As a Quaternary repository of wind-reworked Indus River sand at the entry point in the Himalayan foreland basin, the Thal Desert in northern Pakistan stores mineralogical information useful to trace erosion patterns across the western Himalayan syntaxis and the adjacent orogenic segments that fed detritus into the Indus delta and huge deep-sea fan throughout the Neogene. Provenance analysis of Thal Desert sand was carried out by applying optical and semi-automated Raman spectroscopy on heavy-mineral suites of four eolian and 11 fluvial sand samples collected in selected tributaries draining one specific tectonic domain each in the upper Indus catchment. In each sample, the different types of amphibole, garnet, epidote and pyroxene grains—the four dominant heavy-mineral species in orogenic sediment worldwide—were characterized by SEM-EDS spectroscopy. The chemical composition of 4249 grains was thus determined. Heavy-mineral concentration, the relative proportion of heavy-mineral species, and their minerochemical fingerprints indicate that the Kohistan arc has played the principal role as a source, especially of pyroxene and epidote. Within the western Himalayan syntaxis undergoing rapid exhumation, the Southern Karakorum belt drained by the Hispar River and the Nanga Parbat massif were revealed as important sources of garnet, amphibole, and possibly epidote. Sediment supply from the Greater Himalaya, Lesser Himalaya, and Subhimalaya is dominant only for Punjab tributaries that join the Indus River downstream and do not contribute sand to the Thal Desert. The detailed compositional fingerprint of Thal Desert sand, if contrasted with that of lower course tributaries exclusively draining the Himalaya, provides a semi-actualistic key to be used, in conjunction with complementary provenance datasets and geological information, to reconstruct changes in paleodrainage and unravel the relationship between climatic and tectonic forces that controlled the erosional evolution of the western Himalayan-Karakorum orogen in space and time.

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