Nd–Sr isotopic constraints on the interactions of the Intermontane Superterrane with the western edge of North America in the southern Canadian Cordillera

1995 ◽  
Vol 32 (10) ◽  
pp. 1740-1758 ◽  
Author(s):  
Dipak K. Ghosh
Keyword(s):  
North American ◽  
Late Jurassic ◽  
Crustal Contamination ◽  
Late Triassic ◽  
Western Boundary ◽  
Canadian Cordillera ◽  
Isotopic Compositions ◽  
The North ◽  
Tectonic History ◽  
Early Tertiary

Sr and Nd isotopic compositions of the late Paleozoic metavolcanics and Late Triassic to early Tertiary granitoids from four magmatic episodes in the southern Canadian Cordillera from the Kootenay Arc to the Fraser Fault have been used to (i) identify the sources of these rocks, (ii) constrain the compressive tectonic history from Middle Jurassic to Paleocene, and (iii) constrain the western boundary of the basement in this region. The 215–190 Ma old primitive granitoids (εNd = +3.1 to 8.7; 87Sr/86Sr = 0.7028 − 0.7043) of the Late Triassic and Early Jurassic magmatic episode were emplaced in the Paleozoic oceanic crust of Quesnellia (εNd = +2.9 to +9.3) prior to its obduction over the basement. In contrast, during the younger magmatic episodes (Middle–Late Jurassic, Cretaceous, and early Tertiary), the granitoids from western Quesnellia show primitive isotopic compositions, and those from eastern Quesnellia show eastward-increasing crust-contaminated compositions. The contaminated characters of the Middle–Late Jurassic (180–150 Ma) granitoids from eastern Quesnellia (εNd = +2.8 to −9.1; 87Sr/86Sr = 0.7041 − 0.7083) suggest that by 180 Ma, the eastern part of Quesnellia obducted over the North American cratonic basement by an amount of about 100 km (Eocene extension corrected) measured from westward shifts of the Nd and Sr isopleths. The eastward-increasing crustal-contamination patterns in the Cretaceous (120–80 Ma) and the Paleocene igneous rocks also show westward shifts of these isopleths by 20 and 70 km, respectively. Thus, we observe that a total 190 km of obduction took place, this amount is similar to the amount of shortening measured in the Rocky Mountains Fold and Thrust Belt, and the western boundary of the North American basement presently lies at least 25–75 km east of the Fraser Fault.

New fission-track results from the northern Chiapas Massif area, SE Mexico: trying to reconstruct its complex thermo-tectonic history

2018 ◽  
Vol 35 (1) ◽  
pp. 79-92 ◽  
Author(s):  
Fanis Abdullin ◽  
Luigi Solari ◽  
Carlos Ortega-Obregón ◽  
Jesús Solé
Keyword(s):  
North American ◽  
Fission Track ◽  
Source Area ◽  
North American Plate ◽  
Late Triassic ◽  
Published Data ◽  
Tectonic Event ◽  
Southern Mexico ◽  
The North ◽  
Tectonic History

The Chiapas Massif Complex, which represents the crystalline basement of the southern Maya block within the North American plate, records numerous thermo-tectonic and magmatic events that occurred in southern Mexico at least since the late Mesoproterozoic. The present study was performed across the northern Chiapas Massif region to reconstruct its complex thermo-tectonic history from Mesozoic to present times. Basement samples and sandstones of the San Ricardo Formation derived from the Chiapas Massif Complex source area were analyzed by in situ apatite fission-track dating. The new fission-track results obtained in this study, together with previously published data, indicate that the Chiapas Massif Complex, or rather the whole Maya terrane, have experienced a complex long-term geodynamic evolution with at least five post-Permian tectonic and magmatic events: (1) a Late Triassic cooling event, likely related to the initial breakup of Pangea; (2) Early Jurassic volcanism that can be linked to the Nazas volcanic arc; (3) a Middle Jurassic tectonic event that was triggered by continental rifting at the beginning of the opening of the Gulf of Mexico; (4) a Late Cretaceous to Paleocene orogeny that may actually represent the southernmost continuation of the Laramide sensu lato which affected central and northern Mexico; and (5) the middle–late Miocene Chiapanecan event that is tectonically controlled by the interaction of the North American, Caribbean, and Cocos plates. This interpretation could be useful towards a better understanding of the geological history of southern North America. Some recommendations on sampling and analytical strategies are also given for consideration in further thermochronological studies in Chiapas.

Lithospheric processes and products in the southern Canadian Cordillera: a Lithoprobe perspective

1995 ◽  
Vol 32 (10) ◽  
pp. 1803-1824 ◽  
Author(s):  
Frederick A. Cook
Keyword(s):  
North America ◽  
North American ◽  
Time Interval ◽  
Canadian Cordillera ◽  
Plate Convergence ◽  
The North ◽  
Early Tertiary ◽  
Fracture Systems ◽  
North American Craton ◽  
Oceanic Plates

Analyses of Lithoprobe and other data from southwestern Canada provide new insights on how this portion of the Cordillera formed during plate convergence along the western margin of North America. Crustal rocks are detached from their mantle lithosphere, which must have been consumed during subduction. Detachment occurred at or near the base of the crust beneath the Intermontane and (or) Omineca belts, probably along the tips of tectonic wedges while the rocks were still outboard of the relatively cool, mechanically rigid, North American craton. During the Late Cretaceous and early Tertiary, rotation of detached rocks caught between the North American craton and the oceanic plates accounts for some apparently conflicting results between paleomagnetic data that indicate large northward translation of rocks in the western Cordillera, and regional geological features that appear to preclude comparable amounts of translation of rocks in the eastern Cordillera during the same time interval. Transpression associated with rotation in the Foreland and Omineca belts ceased by the early Tertiary because detached allochthonous rocks of the crust became mechanically attached to, and thus physically part of, North America. Continued plate convergence led to regional transtensional shearing and associated crustal extension in the southern Canadian Cordillera, and perhaps as far inboard as northern Montana, where coeval magmatism was probably associated with new, or reactivation of ancient, lithosphere-penetrating fracture systems.

Tectonic interpretation of west-verging folds in the Selkirk Allochthon of the southern Canadian Cordillera

1988 ◽  
Vol 25 (2) ◽  
pp. 292-300 ◽  
Author(s):  
Richard L. Brown ◽  
Larry S. Lane
Keyword(s):  
North American ◽  
Late Jurassic ◽  
Shear Zones ◽  
Canadian Cordillera ◽  
Fundamental Change ◽  
The West ◽  
The North ◽  
North American Craton ◽  
Tectonic Slice ◽  
Tectonic Interpretation

The Selkirk Allochthon, a composite tectonic slice composed of North American paleocontinental-margin deposits and more distal, possibly marginal-basin "suspect terrane," was displaced eastward toward the craton in the Late Jurassic and Late Cretaceous.The Carnes Nappe, a major west-verging recumbent anticline within the Selkirk Allochthon, is considered the southern continuation of Scrip Nappe, which in the Monashee Mountains has an inverted limb length of 50 km. The west-verging nappe and associated structures are interpreted as having originated in the Early to Middle Jurassic during accretion of western allochthonous terranes and prior to eastward displacement of the Selkirk Allochthon.The reversal from westward vergence away from the North American craton to eastward vergence is considered as marking a fundamental change in the evolution of the orogenic belt and may reflect a transition from underthrusting of western allochthonous terranes on blind-shear zones to east-directed breakthrough thrusts.

New multituberculate mammal from the Early Cretaceous of eastern North America

2013 ◽  
Vol 50 (3) ◽  
pp. 315-323 ◽  
Author(s):  
Richard L. Cifelli ◽  
Cynthia L. Gordon ◽  
Thomas R. Lipka
Keyword(s):  
North America ◽  
Iberian Peninsula ◽  
Early Cretaceous ◽  
North American ◽  
Lower Cretaceous ◽  
Late Jurassic ◽  
Relative Length ◽  
Central Position ◽  
Eastern North America ◽  
The North

Multituberculates, though among the most commonly encountered mammalian fossils of the Mesozoic, are poorly known from the North American Early Cretaceous, with only one taxon named to date. Herein we describe Argillomys marylandensis, gen. et sp. nov., from the Early Cretaceous of Maryland, based on an isolated M2. Argillomys represents the second mammal known from the Arundel Clay facies of the Patuxent Formation (Lower Cretaceous: Aptian). Though distinctive in its combination of characters (e.g., enamel ornamentation consisting of ribs and grooves only, cusp formula 2:4, presence of distinct cusp on anterobuccal ridge, enlargement of second cusp on buccal row, central position of ultimate cusp in lingual row, great relative length), the broader affinities of Argillomys cannot be established because of non-representation of the antemolar dentition. Based on lack of apomorphies commonly seen among Cimolodonta (e.g., three or more cusps present in buccal row, fusion of cusps in lingual row, cusps strongly pyramidal and separated by narrow grooves), we provisionally regard Argillomys as a multituberculate of “plagiaulacidan” grade. Intriguingly, it is comparable in certain respects to some unnamed Paulchoffatiidae, a family otherwise known from the Late Jurassic – Early Cretaceous of the Iberian Peninsula.

Systematics and Paleoecology of Norian (Late Triassic) Bivalves from a Tropical Island Arc: Wallowa Terrane, Oregon

1987 ◽  
Vol 61 (S22) ◽  
pp. 1-83 ◽  
Author(s):  
Cathryn R. Newton ◽  
Michael T. Whalen ◽  
Joel B. Thompson ◽  
Nienke Prins ◽  
David Delalla
Keyword(s):  
North American ◽  
Island Arc ◽  
Late Triassic ◽  
Small Scale ◽  
Long Distance ◽  
Tropical Island ◽  
North American Cordillera ◽  
The North ◽  
Wallowa Terrane ◽  
Hells Canyon

Early Norian silicified bivalves from Hells Canyon in the Wallowa terrane of northeastern Oregon are part of a rich molluscan biota associated with a tropical island arc. The Hells Canyon locality preserves lenses of silicified shells formed as tempestites in a shallow subtidal carbonate environment. These shell assemblages are parautochthonous and reflect local, rather than long-distance, transport. Silicification at this locality involved small-scale replacement of original calcareous microstructures, or small-scale replacement of neomorphosed shells, without an intervening phase of moldic porosity. This incremental replacement of carbonate by silica contrasts markedly with void-filling silicification textures reported previously from silicified Permian bivalve assemblages.The bivalve paleoecology of this site indicates a suspension feeding biota existing on and within the interstices of coral-spongiomorph thickets, and inhabiting laterally adjacent substrates of peloidal carbonate sand. The bivalve fauna is ecologically congruent with the reef-dwelling molluscs associated with Middle Triassic sponge-coral buildups in the Cassian Formation of the Dolomites (Fuersich and Wendt, 1977). Hells Canyon is a particularly important early Norian locality because of the diversity of substrate types and because the site includes many first occurrences of bivalves in the North American Cordillera. These first occurrences include the first documentation of the important epifaunal families Pectinidae and Terquemiidae in Triassic rocks of the North American Cordillera.The large number of biogeographic and geochronologic range extensions discovered in this single tropical Norian biota indicates that use of literature-based range data for Late Triassic bivalves may be very hazardous. Many bivalve taxa formerly thought to have gone extinct in Karnian time have now been documented from Norian strata in this arc terrane. These range extensions, coupled with the high bivalve species richness of the Hells Canyon site, suggest that the Karnian mass extinction in several literature-based compilations may be an artifact of incomplete sampling. Even for the Norian, present compilations of molluscan extinction may have an unacceptably large artifactual component.Thirty-five bivalve taxa from the Hells Canyon locality are discussed. Of these, seven are new: the mytilid Mysidiella cordillerana n. sp., the limacean Antiquilima vallieri n. sp., the true oyster Liostrea newelli n. sp., the pectinacean Crenamussium concentricum n. gen. and sp., the unioid Cardinioides josephus n. sp., the trigoniacean Erugonia canyonensis n. gen. and sp., and the carditacean Palaeocardita silberlingi n. sp.

Late Triassic orogenic assembly of the Tibetan Plateau: constraints from magmatism and metamorphism in the east Lhasa terrane

2021 ◽  
Author(s):  
Yanfei Chen ◽  
Zeming Zhang ◽  
Richard M Palin ◽  
Zuolin Tian ◽  
Hua Xiang ◽  
...  
Keyword(s):  
Crustal Thickening ◽  
Late Triassic ◽  
The Tibetan Plateau ◽  
Plate Convergence ◽  
Lhasa Terrane ◽  
The North ◽  
Tectonic History ◽  
Peak Metamorphism ◽  
Tethys Ocean ◽  
Lower Crustal

Abstract The early Mesozoic evolution of the Lhasa terrane, which represents a major component of the Himalayan-Tibetan orogen, remains highly controversial. In particular, geological units and events documented either side of the eastern Himalayan syntaxis (EHS) are poorly correlated. Here, we report new petrological, geochemical and geochronological data for co-genetic peraluminous S-type granites and metamorphic rocks (gneiss and schist) from the Motuo–Bomi–Chayu region of the eastern Lhasa terrane, located on the eastern flank of the EHS. Zircon U–Pb dating indicates that these units record both Late Triassic magmatic (216–206 Ma) and metamorphic (209–198 Ma) episodes. The granites were derived from a Paleoproterozoic crustal source with negative zircon εHf(t) values (–5.5 to –16.6) and TDM2 model ages of 1.51–1.99 Ga, and are interpreted to have formed by crustal anatexis of nearby metasediments during collisional orogeny and crustal thickening. The gneisses and schists experienced similar upper amphibolite-facies peak metamorphism and associated partial melting, followed by decompressional cooling and retrograde metamorphism. These rocks were buried to lower-crustal depths and then exhumated to the surface in a collisional orogenic setting during plate convergence. From comparison of these data to other metamorphic belts with similar grades and ages, and association of coeval granitic magmatism widespread in the central-east Lhasa terrane, we propose that the studied co-genetic magmatism and metamorphism in the Motuo–Bomi–Chayu region records Late Triassic accretion of the North Lhasa and South Lhasa terranes, which represents the first evidence of the Paleo-Tethys ocean (PTO) closure in this part of Asia. These data provide new constraints on the spatial and temporal evolution of the Paleo-Tethyan Wilson Cycle and provide a ‘missing link’ to correlate the geology and tectonic history of the Lhasa terrane continental crust on either side of the EHS.

Significance of radiolarian age data to the Mesozoic tectoni and sedimentary evolution of the northern Pindos Mountains, Greece

1992 ◽  
Vol 129 (4) ◽  
pp. 385-400 ◽  
Author(s):  
Gregory Jones ◽  
Patrick de Wever ◽  
Alastair H. F. Robertson
Keyword(s):  
Late Jurassic ◽  
Ocean Basin ◽  
Late Triassic ◽  
Reduced Form ◽  
Sedimentary Evolution ◽  
Early Tertiary ◽  
Clastic Sediments ◽  
Marine Carbonates ◽  
Significant Compression ◽  
Two Phases

AbstractRadiolarians were extracted from siliceous sediments of the northern Pindos Mountains, in an attempt to establish the chronology of tectonic and stratigraphic events related to the evolution of the Pindos ocean basin. Three separate phases of siliceous sedimentation were identified: (i) (mid-) late Triassic; (ii) mid-late Jurassic and (iii) mid-late Cretaceous. The first two phases are also known from the Pindos and Sub-Pelagonian zones of southern and central Greece, and elsewhere in the Dinarides andHellenides. However, the occurrence of Cretaceous radiolarites in the west central Tethyan region is somewhat unusual. Field observations suggest thatfrom the mid-late Triassic through to the mid Jurassic, radiolarites were deposited on volcanic basement, or were interbedded with sediments associated with the late rifting/spreading stages in the development of the Pindos ocean. Radiolarites of mid-late Jurassic age are commonly interbedded with clastic sediments of ophiolitic derivation. This coincides with a phase of significant compression within the Hellenides, which caused intra-oceanic deformation of the Pindos ophiolite. The ophiolite was subsequently emplaced onto the margin of the Pelagonian microcontinent in latest Jurassic time (Kim-meridgian-early Tithonian), as evidenced by transgressive marine carbonates. However, the Pindos basin survived in reduced form until the early Tertiary, allowing radiolarites to accumulate again within Cretaceous post-tectonic clastic sequences.

Myggbukta and Kap Broer Ruys: the most northerly of the East Greenland Tertiary igneous centres(?)

1984 ◽  
Vol 48 (348) ◽  
pp. 323-343 ◽  
Author(s):  
B. G. J. Upton ◽  
C. H. Emeleus ◽  
R. D. Beckinsale ◽  
R. M. Macintyre
Keyword(s):  
North Atlantic ◽  
Crustal Contamination ◽  
Silica Content ◽  
Dyke Swarm ◽  
Central Volcano ◽  
Crustal Anatexis ◽  
Basic Dyke ◽  
The North ◽  
Early Tertiary ◽  
Small Rise

Abstract The Myggbukta Complex is a shallowly dissected central volcano superimposed on the early Tertiary Plateau Basalts of NE Greenland. This, and the Kap Broer Ruys centre, 30 km to the east, appear to be the most northerly central complexes of the North Atlantic Tertiary Province. The Myggbukta Complex comprises a suite of extrusions and minor intrusions ranging from picritic basalt to potassic rhyolite: most of the suite appears related by relatively low pressure (< 10 kbar) crystal fractionation. A small rise in initial 87Sr/86Sr (0.70593) with silica content is attributed to minor contamination through crustal anatexis. A basic dyke-swarm associated with the complex, precedes it and shows more limited differentiation. The basalts of the dyke-swarm and the Myggbukta Complex are genetically intimately related to the lavas forming the upper part of the earlier plateau basalt succession (UPLS). It is proposed that a large shield volcano developed some 100 km west of the developing spreading centre (Mohns/Aegir ridge), of which the UPLS, the dyke-swarm and the Myggbukta Complex represent three successive evolutionary stages. A generalized increase in differentiation through time can be recognized from one stage to the next. The acid intrusions of the Kap Broer Ruys area are probably also largely residues of basalt fractionation like their Myggbukta counterparts. However, higher initial 87Sr/86Sr ratios (0.70625–0.71034) imply a greater degree of crustal contamination.

Sign in / Sign up

Export Citation Format

Share Document