scholarly journals East-derived strata in the Methow basin record rapid mid-Cretaceous uplift of the southern Coast Mountains batholith

2014 ◽  
Vol 51 (4) ◽  
pp. 339-357 ◽  
Author(s):  
Kathleen D. Surpless ◽  
Zachary T. Sickmann ◽  
Trevor A. Koplitz
Keyword(s):  
North American ◽  
Large Scale ◽  
Washington State ◽  
Eastern Coast ◽  
Sediment Sources ◽  
Coast Mountains ◽  
The North ◽  
North American Craton ◽  
Continental Interior ◽  
Sandstone Petrography

The Jurassic–Cretaceous Methow basin of northern Washington State and southern British Columbia forms an overlap sequence linking several small tectonostratigraphic terranes. Sandstone petrography, sandstone and mudrock geochemistry, and detrital zircon U–Pb age and Hf analysis of mid-Cretaceous, east-derived Methow strata together document a remarkably uniform provenance signature that suggests proximal, abundant, and unchanging sediment sources throughout deposition. The eastern belt of the Coast Mountains batholith, intruded into Stikine and related inboard terranes of the Intermontane superterrane, along with Jurassic and Cretaceous plutons of the westernmost Okanogan Range, provide the best match to the provenance signature of east-derived sediment in the Methow basin during the mid-Cretaceous. Furthermore, the Cretaceous and Jurassic plutons of the eastern Coast Mountains batholith and western Okanogan Range were rapidly uplifted to provide the substantial thickness of sediment in the Methow basin, and they must have acted as a topographic barrier that effectively prevented sediment derived from the continental interior from reaching the basin. This uplift of a proximal eastern source occurred during regional late Early Cretaceous sinistral transpression and resulted in subsidence of the Methow trough and rapid deposition of east-derived strata in the Methow basin. Because Methow sediment sources apparently did not include the North American interior, the extent of post-depositional large-scale translation relative to the North American craton of the Methow basin with its proximal, eastern sources cannot be unequivocally determined.

New 42 Ma cratonic North American paleomagnetic pole from the Yukon underscores another Cordilleran paleomagnetism-geology conundrum

2003 ◽  
Vol 40 (10) ◽  
pp. 1321-1334 ◽  
Author(s):  
David TA Symons ◽  
Philippe Erdmer ◽  
Phil JA McCausland
Keyword(s):  
North American ◽  
Magnetic Polarity ◽  
Eastern Coast ◽  
The North ◽  
Normal Polarity ◽  
Reversed Polarity ◽  
North American Craton ◽  
Host Rocks ◽  
Pacific Plate Subduction ◽  
Plate Subduction

Eocene posttectonic plutons of the Beaver River alkalic complex in southeastern Yukon intruded Devonian–Mississippian and Triassic sandstones in the Foothills of the Canadian Cordillera. A paleomagnetic collection of 27 sites from three separate plutons produced 326 specimens that were analyzed using alternating field and thermal step demagnetization methods. The A component characteristic remanent magnetization (ChRM) resides in magnetite with normal polarity in the 42.6 ± 0.8 Ma Beaver River pluton, reversed polarity in the 42.1 ± 0.7 Ma Larson Creek East pluton, and both polarities in the 41.3 ± 0.4 Ma Larson Creek West pluton, corresponding with magnetic polarity chrons 20n, 19r, and the boundary between chron 19r and 18n, respectively. The ChRMs of the plutons are indistinguishable (2σ) with a mean for the 42.0 ± 0.5 Ma complex of D = 158.8°, I = –73.1° (N = 21 sites, α95 = 3.0°, k = 116.8). A positive paleomagnetic contact test shows the A component to be primary, and the poorly isolated B component suggests the host rocks for Larson Creek West are Early to Middle Devonian. The paleopole for the Beaver River complex at 79.2°N, 145.8°E (N = 21, dp = 4.8°, dm = 5.4°; Q = 7) is concordant with interpolated 42 Ma reference poles for the North American craton. In contrast, paleopoles from the accreted Intermontane and eastern Coast Belt terranes record clockwise rotations of 24° ± 10° (Eocene) and 13° ± 5° (Oligocene–Pliocene), indicating that the allochthonous Intermontane terranes have been progressively driven ~240 ± 120 km eastwards up and over pericratonic and cratonic North American lower crust by Pacific plate subduction since the mid-Eocene.

Paleomagnetism of the Clam Bank Formation and paleolatitude estimates for western Newfoundland

1993 ◽  
Vol 30 (4) ◽  
pp. 776-786
Author(s):  
G. Murthy ◽  
R. Pätzold
Keyword(s):  
North American ◽  
Early Paleozoic ◽  
The North ◽  
Northerly Direction ◽  
Deformation Event ◽  
Recent Origin ◽  
Component C ◽  
Acadian Orogeny ◽  
North American Craton ◽  
Devonian Age

The Pridolian Clam Bank Formation around Lourdes Cove on the Port au Port Peninsula, western Newfoundland, underwent deformation during the Acadian orogeny. As a result, some of the beds were overturned, but the stratification planes can be accurately determined everywhere. Paleomagnetic studies of the Clam Bank Formation have yielded three well-defined components of magnetization, all acquired subsequent to the deformation event: component A with D = 337.3°, I = −28.3°, (N = 16 sites, k = 25.3, α95 = 7.5°), with a corresponding paleopole at 23.2°N, 145.0°E (dp, dm = 4.5°, 8.2°); component B with D = 172.9°, I = 5.7° (N = 35 specimens, k = 10.2, α95 = 6.4°), with a corresponding paleopole at 38.2°N, 130.1°E (dp, dm = 3.2°, 6.4°); component C with D = 350.4°, I = 69.8° (N = 33 specimens, k = 8.9, α95 = 8.9°). A pre-Mesozoic origin of the A and B components is indicated by the presence of normal and reversed components in specific sites; by the lack of correspondence between the A and B paleopoles and the Mesozoic and later pole positions from the Appalachians and the North American craton; and by agreement with Paleozoic poles from the region. The A component was probably acquired immediately after deformation during the Acadian orogeny. The B component is probably a chemical remanence that was acquired during Permo-Carboniferous (Kiaman) time. The C component is of recent origin, probably acquired in the present Earth's field. Paleomagnetic data from western Newfoundland are used in a localized setting to construct a paleopole sequence and to estimate paleolatitudes for western Newfoundland during the Paleozoic. Keeping in mind the paucity of data for Siluro-Devonian age from this region, western Newfoundland seems to have been at its southernmost position at the end of the Ordovician and to have occupied equatorial latitudes during the Permo-Carboniferous. The paleolatitude trend suggests that this block, which is part of the North American craton, moved in a southerly direction during the early Paleozoic and in a northerly direction during the middle and late Paleozoic.

scholarly journals Impacts of Large-Scale Circulation on Urban Ambient Concentrations of Gaseous Elemental Mercury in New York, USA

2017 ◽  
Author(s):  
Huiting Mao ◽  
Dolly Hall ◽  
Zhuyun Ye ◽  
Ying Zhou ◽  
Dirk Felton ◽  
...  
Keyword(s):  
New York ◽  
North American ◽  
Large Scale ◽  
Measurement Data ◽  
Elemental Mercury ◽  
Urban Site ◽  
Large Scale Circulation ◽  
Gaseous Elemental Mercury ◽  
The North ◽  
The Impact

Abstract. The impact of large-scale circulation on urban gaseous elemental mercury (GEM) was investigated through analysis of 2008–2015 measurement data from an urban site in New York City (NYC), New York, USA. Distinct annual cycles were observed in 2009–2010 with mixing ratios in warm seasons (i.e. spring–summer) 10–20 ppqv (~ 10 %–25 %) higher than in cool seasons (i.e. fall–winter). This annual cycle was disrupted in 2011 by an anomalously strong influence of the North American trough in that warm season and was reproduced in 2014 with annual amplitude enhanced up to ~ 70 ppqv associated with a particularly strong Bermuda High. North American trough axis index (TAI) and intensity index (TII) were used to characterize the effect of the North American trough on NYC GEM especially in winter and summer. The intensity and position of the Bermuda High had a significant impact on GEM in warm seasons supported by a strong correlation (r reaching 0.96, p 

scholarly journals Typology and nuance: relativization

2020 ◽  
pp. 104-130
Author(s):  
Marianne Mithun
Keyword(s):  
North American ◽  
Large Scale ◽  
Relative Clauses ◽  
Spontaneous Speech ◽  
The Other ◽  
Stages Of Development ◽  
Linguistic Typology ◽  
The North

Much of linguistic typology is inherently categorical. In large-scale typological surveys, grammatical constructions, distinctions, and even variables are typically classified as present, absent, or embodying one of a set of specified options. This work is valuable for a multitude of purposes, and in many cases such categorization is sufficient. In others, we can advance our understanding further if we take a more nuanced approach, considering the extent to which a particular construction, distinction, or variable is installed in the grammar. An important tool for this approach is the examination of unscripted speech in context, complete with prosody. This point is illustrated here with Mohawk, an Iroquoian language indigenous to the North American Northeast. As will be seen, the two types of construction which might be identified as relative clauses are emergent, one less integrated into the grammar than the other. Examination of spontaneous speech indicates that the earliest stages of development are prosodic, as speakers shape their messages according to their communicative purposes at each moment.

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.

scholarly journals The origin of till sequences by subglacial sediment deformation beneath mid-latitude ice sheets

1996 ◽  
Vol 22 ◽  
pp. 75-84 ◽  
Author(s):  
G. S. Boulton
Keyword(s):  
North American ◽  
Large Scale ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Erosion And Deposition ◽  
The North ◽  
Sediment Deformation ◽  
Source Materials ◽  
The Last Glacial

A theory of erosion and deposition as a consequence of subglacial sediment deformation over beds of unlithified sediment is reviewed and applied to large-scale till sequences formed on the southern flanks of the North American and British and European ice sheets during the last glacial cycle. The distribution of till thickness, till lithology in relation to source materials and intra-till erosion surfaces along a flowline in the Michigan lobe of the North American ice sheet are shown to be compatible with the deformational theory but not with other modes of till genesis. It is then demonstrated, in the case of the British ice sheet, how the assumption of a deformational origin for tills can be used to infer time-dependent patterns of ice-sheet dynamic behaviour. By reference to an example from the Netherlands, it is argued that many till sequences interpreted as melt-out tills are more likely to have formed by subglacial sediment deformation.

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