A slice of basement in the western margin of the Appalachian orogen, Saint-Malachie, Quebec

1978 ◽  
Vol 15 (8) ◽  
pp. 1242-1249 ◽  
Author(s):  
A. Vallières ◽  
C. Hubert ◽  
C. Brooks
Keyword(s):  
Shallow Water ◽  
Volcanic Rocks ◽  
Mobile Belt ◽  
Isotopic Age ◽  
Western Margin ◽  
Appalachian Orogen ◽  
Internal Domain

Slivers of gneisses and amphibolites (termed the Sainte-Marguerite Complex) having a minimum isotopic age of 900 Ma are interpreted to represent thrust slices of Grenvillian-type basement within the western margin of die internal domain of the Appalachian orogen. These slices constitute the basement to a series of spilitized volcanic rocks and interbedded shallow-water sandstones (termed the Montagne de Saint-Anselme Formation) which are interpreted to be Precambrian to Cambrian(?) rift-related precursors to the filling of the Appalachian mobile belt.

Origin and orogenic role of the Chain Lakes massif, Maine and Quebec

2006 ◽  
Vol 43 (3) ◽  
pp. 339-366 ◽  
Author(s):  
C C Gerbi ◽  
S E Johnson ◽  
J N Aleinikoff
Keyword(s):  
Volcanic Rocks ◽  
Metamorphic Event ◽  
Early Paleozoic ◽  
Western Margin ◽  
Middle Ordovician ◽  
Volcanic Sequence ◽  
Iapetus Ocean ◽  
Appalachian Orogen ◽  
New Interpretation

The Chain Lakes massif has long been an enigmatic component of the Appalachian orogen, but new structural, microstructural, and geochronological information provides the basis for the following new interpretation of the massif and its history. In the early Paleozoic, sediments and volcanic rocks from Laurentia or a Laurentian-derived microcontinent were deposited in a fore-arc basin on the western margin of the Iapetus ocean. Following intrusion of arc-related magmas, the sedimentary–volcanic sequence was heated sufficiently to melt in place, resulting in stratigraphic disaggregation and diatexite formation. We dated monazite growth from this metamorphic event at 469 ± 4 Ma. Although some melt may have left the system, much remained, including water dissolved in the melt. Upon crystallization, this water drove thorough retrogression of the massif, causing pervasive pseudomorphism of porphyroblasts. With cooling and crystallization, the Chain Lakes massif became sufficiently rigid that it was not significantly deformed during the Middle Ordovician through Devonian stages of Appalachian orogenesis involving the arrival of several peri-Gondwanan microcontinents.

Regionally continuous Miocene rhyolites beneath the eastern Snake River Plain reveal localized flexure at its western margin: Idaho National Laboratory and vicinity

2020 ◽  
Vol 57 (3) ◽  
pp. 241-270
Author(s):  
Kyle L. Schusler ◽  
David M. Pearson ◽  
Michael McCurry ◽  
Roy C. Bartholomay ◽  
Mark H. Anders
Keyword(s):  
Volcanic Rocks ◽  
Snake River Plain ◽  
North American Plate ◽  
Snake River ◽  
Trace Element Geochemistry ◽  
Deep Borehole ◽  
Age Progression ◽  
Western Margin ◽  
Silicic Volcanic ◽  
River Plain

The eastern Snake River Plain (ESRP) is a northeast-trending topographic basin interpreted to be the result of the time-transgressive track of the North American plate above the Yellowstone hotspot. The track is defined by the age progression of silicic volcanic rocks exposed along the margins of the ESRP. However, the bulk of these silicic rocks are buried under 1 to 3 kilometers of younger basalts. Here, silicic volcanic rocks recovered from boreholes that penetrate below the basalts, including INEL-1, WO-2 and new deep borehole USGS-142, are correlated with one another and to surface exposures to assess various models for ESRP subsidence. These correlations are established on U/Pb zircon and 40Ar/39Ar sanidine age determinations, phenocryst assemblages, major and trace element geochemistry, δ18O isotopic data from selected phenocrysts, and initial εHf values of zircon. These data suggest a correlation of: (1) the newly documented 8.1 ± 0.2 Ma rhyolite of Butte Quarry (sample 17KS03), exposed near Arco, Idaho to the upper-most Picabo volcanic field rhyolites found in borehole INEL-1; (2) the 6.73 ± 0.02 Ma East Arco Hills rhyolite (sample 16KS02) to the Blacktail Creek Tuff, which was also encountered at the bottom of borehole WO-2; and (3) the 6.42 ± 0.07 Ma rhyolite of borehole USGS-142 to the Walcott Tuff B encountered in deep borehole WO-2. These results show that rhyolites found along the western margin of the ESRP dip ~20º south-southeast toward the basin axis, and then gradually tilt less steeply in the subsurface as the axis is approached. This subsurface pattern of tilting is consistent with a previously proposed crustal flexural model of subsidence based only on surface exposures, but is inconsistent with subsidence models that require accommodation of ESRP subsidence on either a major normal fault or strike-slip fault.

Paleomagnetism of the Lawrenceton Formation volcanic rocks, Silurian Botwood Group, Change Islands, Newfoundland

1989 ◽  
Vol 26 (2) ◽  
pp. 296-304 ◽  
Author(s):  
Julie E. Gales ◽  
Ben A. van der Pluijm ◽  
Rob Van der Voo
Keyword(s):  
North American ◽  
Volcanic Rocks ◽  
Mobile Belt ◽  
Structural Mapping ◽  
Polar Wander ◽  
The North ◽  
Apparent Polar Wander Path ◽  
Paleomagnetic Study ◽  
North American Craton

Paleomagnetic sampling of the Lawrenceton Formation of the Silurian Botwood Group in northeastern Newfoundland was combined with detailed structural mapping of the area in order to determine the deformation history and make adequate structural corrections to the paleomagnetic data.Structural analysis indicates that the Lawrenceton Formation experienced at least two folding events: (i) a regional northeast–southwest-trending, Siluro-Devonian folding episode that produced a well-developed axial-plane cleavage; and (ii) an episode of local north-trending folding. Bedding – regional cleavage relationships indicate that the latter event is older than the regional folding.Thermal demagnetization of the Lawrenceton Formation yielded univectorial southerly and shallow directions (in situ). A fold test on an early mesoscale fold indicates that the magnetization of the Botwood postdates this folding event. However, our results, combined with an earlier paleomagnetic study of nearby Lawrenceton Formation rocks, demonstrate that the magnetization predates the regional folding. Therefore, we conclude that the magnetization occurred subsequent to the local folding but prior to the period of regional folding.While a tectonic origin for local folding cannot be entirely excluded, the subaerial nature of these volcanics, the isolated occurrence of these folds, and the absence of similar north-trending folds in other areas of eastern Notre Dame Bay suggest a syndepositional origin. Consequently, the magnetization may be nearly primary. Our study yields a characteristic direction of D = 175°, I = +43°, with a paleopole (16°N, 131 °E) that plots near the mid-Silurian track of the North American apparent polar wander path. This result is consistent with an early origin for the magnetization and supports the notion that the Central Mobile Belt of Newfoundland was adjacent to the North American craton, in its present-day position, since the Silurian.

Sedimentology of the Partry Series in the Partry Mountains, Co. Mayo, Eire

1967 ◽  
Vol 104 (6) ◽  
pp. 585-607 ◽  
Author(s):  
John McManus
Keyword(s):  
Shallow Water ◽  
Marine Environment ◽  
Volcanic Rocks ◽  
Sedimentary Structures ◽  
Welded Tuff ◽  
Water Origin ◽  
Red Bed

AbstractThe Lettereeneen fault, a newly recognized structure, brings the Mweelrea and Maumtrasna Groups of the Partry Series (Caradocian-Llandeilian age) into contact. The stratigraphy of the Mweelrea Group, of red bed facies, is followed from the presence of welded tuff horizons; no such markers exist in the Maumtrasna Group which lies unconformably upon the former.Sedimentary structures of shallow water origin occur in each group. Three types of conglomerate recognized in the area are examined. The immature feldspathic sandstones increase in arkosity upwards.A proluvial or proluvio-marine environment of deposition is suggested, with debris derived from an eastward extension of the metamorphosed Dalradian rocks of the Connemara Cordillera and foothills of sedimentary and volcanic rocks.

An improved velocity model for the crust and upper mantle along the central mobile belt of the Newfoundland Appalachian orogen and its offshore extension

1998 ◽  
Vol 35 (11) ◽  
pp. 1238-1251 ◽  
Author(s):  
Deping Chian ◽  
François Marillier ◽  
Jeremy Hall ◽  
Garry Quinlan
Keyword(s):  
Upper Mantle ◽  
Lower Crust ◽  
Velocity Structure ◽  
Sedimentary Basins ◽  
Velocity Model ◽  
Mobile Belt ◽  
Wide Angle ◽  
Crust And Upper Mantle ◽  
Angle Data ◽  
Appalachian Orogen

New modelling of wide-angle reflection-refraction data of the Canadian Lithoprobe East profile 91-1 along the central mobile belt of the Newfoundland Appalachian orogen reveals new features of the upper mantle, and establishes links in the crust and upper mantle between existing land and marine wide-angle data sets by combining onshore-offshore recordings. The revised model provides detailed velocity structure in the 30-34 km thick crust and the top 30 km of upper mantle. The lower crust is characterized by a velocity of 6.6-6.8 km/s onshore, increasing by 0.2 km/s to the northeast offshore beneath the sedimentary basins. This seaward increase in velocity may be caused by intrusion of about 4 km of basic rocks into the lower crust during the extension that formed the overlying Carboniferous basins. The Moho is found at 34 km depth onshore, rising to 30 km offshore to the northeast with a local minimum of 27 km. The data confirm the absence of deep crustal roots under the central mobile belt of Newfoundland. Our long-range (up to 450 km offset) wide-angle data define a bulk velocity of 8.1-8.3 km/s within the upper 20 km of mantle. The data also contain strong reflective phases that can be correlated with two prominent mantle reflectors. The upper reflector is found at 50 km depth under central Newfoundland, rising abruptly towards the northeast where it reaches a minimum depth of 36 km. This reflector is associated with a thin layer (1-2 km) unlikely to coincide with a discontinuity with a large cross-boundary change in velocity. The lower reflector at 55-65 km depths is much stronger, and may have similar origins to reflections observed below the Appalachians in the Canadian Maritimes which are associated with a velocity increase to 8.5 km/s. Our data are insufficient for discriminating among various interpretations for the origins of these mantle reflectors.

scholarly journals Comparative Study on the Open Boundary Conditions of Shallow Flows

10.29007/pf1g ◽  
2018 ◽  
Author(s):  
Jaeyoung Jung ◽  
Jin Hwan Hwang
Keyword(s):  
Boundary Conditions ◽  
Comparative Study ◽  
Shallow Water ◽  
Shallow Water Equations ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
Shallow Flows ◽  
Incoming Information ◽  
Physical Phenomena ◽  
Internal Domain

In order to accurately simulate physical phenomena, appropriate boundary conditions must be implemented. Where some information propagate along the characteristic curves as in the hyperbolic system such as shallow water equations (SWEs), open boundary conditions (OBCs) must be designed so that such an event should also be maintained even at the boundaries. In other words, OBCs of SWEs must pass information out of the domain and receive the incoming information without any numerical distortion. If OBCs do not reflect the characteristics of SWE, errors will occur and contaminate the information in the internal domain. This study compares several OBCs based on the hyperbolic characteristics of SWE and shows that OBCs derived using hyperbolic characteristic performs better in the several OBCs.

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