Overturned Nicola and Ashcroft strata and their relation to the Cache Creek Group, Southwestern Intermontane Belt, British Columbia

1978 ◽  
Vol 15 (1) ◽  
pp. 99-116 ◽  
Author(s):  
William B. Travers
Keyword(s):  
Lower Jurassic ◽  
Upper Triassic ◽  
Late Triassic ◽  
Turbidity Currents ◽  
Alkaline Magmatism ◽  
Thick Section ◽  
Calc Alkaline ◽  
The West ◽  
Early Mesozoic ◽  
Eastern Edge

The Lower Jurassic, Ashcroft Formation contains a thick section of carbonaceous marine shale and a few graded sandstones. Along the south and east margins of the Ashcroft Basin, Ashcroft strata rest unconformably on calc-alkaline and alkaline volcanic flows and sediments of the Upper Triassic, Nicola Group. On the west margin Nicola and Ashcroft strata lie against mélange of the Cache Creek Group. This contact is faulted in some places, but it may be a depositional unconformity elsewhere.South of Cache Creek village, overturned allochthons of Nicola strata were placed on top of Ashcroft beds in Early Jurassic time before Ashcroft sediments were lithified. Turbidity currents flowed southeast contemporaneous with sliding or thrusting of allochthons.Near the Guichon Creek Batholith, the Ashcroft Formation contains a disconformity that separates Sinemurian–Pliensbachian from Callovian strata. However, in the western part of the Ashcroft basin strata appear continuous from Sinemurian–Pliensbachian to Callovian. The Guichon Creek Batholith was emplaced into Nicola strata along the eastern edge of the Ashcroft Basin about 200 Ma ago (late Sinemurian*) and was quickly unroofed to provide granitic debris to the basin.The Ashcroft Basin appears to have been an early Mesozoic outer arc basin. It formed seaward of calc-alkaline magmatism and landward of and possibly on top of a mélange. Middle or Late Triassic radiolaria found in the Cache Creek show that deformation of the mélange took place as late as Late Triassic time. Arc-directed thrusting and sliding may be gravity processes due to elevation of the outer arc ridge during subduction.

The geology and evolution of the Pinchi Fault Zone at Pinchi Lake, central British Columbia

1977 ◽  
Vol 14 (6) ◽  
pp. 1324-1342 ◽  
Author(s):  
I. A. Paterson
Keyword(s):  
Fault Zone ◽  
Subduction Zones ◽  
High Pressures ◽  
Metamorphic Grade ◽  
Fault System ◽  
Late Triassic ◽  
Transform Fault ◽  
The West ◽  
Early Mesozoic ◽  
Complex Fault

At Pinchi Lake, the Pinchi Fault Zone separates the early Mesozoic Takla Group to the east from the late Paleozoic Cache Creek Group to the west. Between these regions a complex fault system involves a series of elongate fault-bounded blocks of contrasting lithology and metamorphic grade. These blocks consist of: (a) highly deformed aragonite–dolomite limestone and blueschist, (b) pumpellyite–aragonite greenstone, (c) a harzburgite–gabbro–diabase–basalt ophiolite sequence, (d) serpentinized alpine ultramafite, and (e) Cretaceous (?) conglomerate. The blueschist probably formed at 8–12 kbar (8 × 105–12 × 105 kPa) and 225–325 °C during a penetrative early deformation which was closely followed by a later deformation associated with a Late Triassic uplift and cooling event. The ophiolite sequence is overlain by Late Triassic sediments which locally contain aragonite suggesting that at least part of the Takla Group may have also undergone high pressure – low temperature metamorphism.The evolution of the 450 km fault zone is discussed and a model is proposed which involves right lateral transform faulting on the Pinchi Fault and underthrusting along northerly dipping subduction zones during the Late Triassic. The blueschist formed at high pressures in such a subduction zone and leaked to the surface in zones of low pressure along an active transform fault.

Revised stratigraphy of the Takla Group, north-central British Columbia

1977 ◽  
Vol 14 (2) ◽  
pp. 318-326 ◽  
Author(s):  
J. W. H. Monger ◽  
B. N. Church
Keyword(s):  
British Columbia ◽  
Sedimentary Rocks ◽  
Lower Jurassic ◽  
Upper Triassic ◽  
Late Triassic ◽  
North Central ◽  
Volcaniclastic Rocks ◽  
Jurassic Rocks

The Takla Group of north-central British Columbia as originally defined contained volcanic and sedimentary rocks of Late Triassic and Jurassic ages. As redefined herein, it consists of three formations in the McConnell Creek map-area. Lowest is the Dewar Formation, composed of argillite and volcanic sandstone that is largely the distal equivalent of basic flows and coarse volcaniclastic rocks of the Savage Mountain Formation. These formations are overlain by the volcaniclastic, basic to intermediate Moosevale Formation. These rocks are Upper Triassic (upper Karnian and lower Norian). They are unconformably overlain by Lower Jurassic rocks of the Hazelton Group.

scholarly journals Late Triassic (Tuvalian – Carnian, Tropites subbullatus/Anatropites spinosus zones) ostracods from Monte Gambanera (Castel di Iudica, Central-Eastern Sicily, Italy)

2020 ◽  
Vol 191 ◽  
pp. 36
Author(s):  
Sylvie Crasquin ◽  
Francesco Sciuto ◽  
Agatino Reitano ◽  
Rosa Maria Coco
Keyword(s):  
Upper Triassic ◽  
Late Triassic ◽  
The West ◽  
West Side ◽  
Central Eastern ◽  
First Time

Ostracod associations coming from the Upper Triassic (Tropites subbullatus/Anatropites spinosus zones of the Tuvalian substage) clays and sandstones of the Mufara Formation outcropping along the west side of Monte Gambanera (Castel di Iudica, central-eastern Sicily) have been analysed for the first time. The specimens are relatively abundant, silicified, well preserved and often preserved as complete carapaces. Over 200 specimens have been determined. They belong to the families Healdiidae, Bairdiidae, Bythocyprididae, Acratiidae, Cytheruridae, Limnocytheridae, Candonidae, Cavellinidae, Polycopidae and Thaumatocyprididae. Thirty-seven species are identified of which nine species are new: Hungarella forelae n.sp., Hungarella siciliiensis n.sp., Bairdia andrecrasquini n.sp., Bairdia gambaneraensis n.sp., Ptychobairdia iudicaensis n.sp., Ptychobairdia leonardoi n.sp., Petasobairdia jeandercourti n.sp., Kerocythere dittainoensis n.sp. and Mockella barbroae n.sp.

scholarly journals A revision of the early neotheropod genus Sarcosaurus from the Early Jurassic (Hettangian–Sinemurian) of central England

2020 ◽  
Vol 191 (1) ◽  
pp. 113-149 ◽  
Author(s):  
Martín D Ezcurra ◽  
Richard J Butler ◽  
Susannah C R Maidment ◽  
Ivan J Sansom ◽  
Luke E Meade ◽  
...  
Keyword(s):  
Type Species ◽  
Lower Jurassic ◽  
Upper Triassic ◽  
Early Jurassic ◽  
Late Triassic ◽  
Valid Species ◽  
Character State ◽  
New Information ◽  
Evolutionary Radiation ◽  
Nomina Dubia

Abstract Neotheropoda represents the main evolutionary radiation of predatory dinosaurs and its oldest records come from Upper Triassic rocks (c. 219 Mya). The Early Jurassic record of Neotheropoda is taxonomically richer and geographically more widespread than that of the Late Triassic. The Lower Jurassic (upper Hettangian–lower Sinemurian) rocks of central England have yielded three neotheropod specimens that have been assigned to two species within the genus Sarcosaurus, S. woodi (type species) and S. andrewsi. These species have received little attention in discussions of the early evolution of Neotheropoda and recently have been considered as nomina dubia. Here, we provide a detailed redescription of one of these specimens (WARMS G667–690) and reassess the taxonomy and phylogenetic relationships of the genus Sarcosaurus. We propose that the three neotheropod specimens from the Early Jurassic of central England represent a single valid species, S. woodi. The second species of the genus, ‘S. andrewsi’, is a subjective junior synonym of the former. A quantitative phylogenetic analysis of early theropods recovered S. woodi as one of the closest sister-taxa to Averostra and provides new information on the sequence of character state transformations in the lead up to the phylogenetic split between Ceratosauria and Tetanurae.

scholarly journals Biomarker distributions and depositional environments of continental source rocks in Sichuan Basin, SW China

2020 ◽  
Vol 38 (6) ◽  
pp. 2296-2324
Author(s):  
Siqin Huang ◽  
Guosheng Xu ◽  
Fanghao Xu ◽  
Wei Wang ◽  
Haifeng Yuan ◽  
...  
Keyword(s):  
Sichuan Basin ◽  
Lower Jurassic ◽  
Upper Triassic ◽  
Depositional Environments ◽  
Source Rocks ◽  
Late Triassic ◽  
Ms Analysis ◽  
Continental Source ◽  
The Sichuan Basin ◽  
Tricyclic Terpanes

In order to study the distributions of the biomarker of the continental source rocks in the Sichuan Basin, 71 source rock samples were collected from the Upper Triassic-Lower Jurassic strata in different regions. The n-alkanes, isoprenoids, terpane, sterane, sesquiterpenes, caranes and aromatics in the extracts were analyzed in detail. GC-MS analysis has been conducted to analyze the biomarker of the continental source rocks. The results of GC-MS analysis indicate that the Upper Triassic source rocks are high in the content of extended tricyclic terpanes, pristane, phytane, gammacerane, C28 regular sterane and carotene. However, they are low in content of rearranged compounds. The ratio of Pr/Ph is less than 1, with the characteristics of tricyclic terpane C21 > C23. The Lower Jurassic source rocks are extremely low in content (even zero) of extended tricyclic terpanes, pristane, phytane, gammacerane, C28 regular sterane and carotene, and high in content of rearranged compounds. The ratio of Pr/Ph is more than 1, with tricyclic terpane C21 > C23. These characteristics are still preserved after maturation. Moreover, during the sedimentation of the source rocks of T3x2–T3x3 members, the supply of continental plants was low (TAR < 1, with regular sterane C27 > C29, 1-MP/9-MP < 1). The source rocks of T3x5 member were low in salinity (slightly low content of gammacerane and carotene), being different significantly from the other Upper Triassic source rocks. In addition, during the sedimentation of the source rocks of J1dn Member, the supply of continental plants was also low (regular sterane C27 > C29, 1-MP/9-MP < 1), being quite different from that of J1l member. Through analysis of the difference in biomarkers, it is indicated that the sedimentary environment had changed from anoxic and brackish water during the Late Triassic to oxygen-rich and freshwater during the Early Jurassic in the Sichuan Basin. During this process, the types of organic matters had changed for several times.

scholarly journals The Early Mesozoic Cordilleran arc and Late Triassic paleotopography: The detrital record in Upper Triassic sedimentary successions on and off the Colorado Plateau

Geosphere ◽  
2013 ◽  
Vol 9 (3) ◽  
pp. 602-613 ◽  
Author(s):  
N.R. Riggs ◽  
S.J. Reynolds ◽  
P.J. Lindner ◽  
E.R. Howell ◽  
A.P. Barth ◽  
...  
Keyword(s):  
Colorado Plateau ◽  
Upper Triassic ◽  
Late Triassic ◽  
Early Mesozoic

scholarly journals The Upper Triassic deposits of the west Bangong-Nujiang suture zone and their paleogeographic implications

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Guichun Wu ◽  
Zhansheng Ji ◽  
Gary G. Lash ◽  
Jianxin Yao
Keyword(s):  
Central Region ◽  
Upper Triassic ◽  
Suture Zone ◽  
Late Triassic ◽  
Upper Permian ◽  
The West ◽  
Apparent Lack ◽  
Sedimentary Succession ◽  
Depositional Setting ◽  
Qiangtang Terrane

AbstractThe Bangong-Nujiang Suture Zone (BNSZ) of Tibet (Xizang) has been interpreted to represent a relic of the Bangong-Nujiang Ocean. However, the existence of this ocean during Triassic time remains a point of contention. A sedimentary succession spanning the Upper Permian through Triassic described from the central BNSZ suggests that the Lhasa and South Qiangtang terranes were contiguous thus negating the existence of a terrane-separating ocean during Triassic time. However, the apparent lack of Triassic deposits in the west BNSZ has called into question the existence of Triassic deposits in the central region of the BNSZ. Our biostratigraphic work in the Wuga Formation of the Gaize area has yielded abundant Norian conodonts thus confirming the existence of Upper Triassic deposits in the west BNSZ. The clastic deposits of the Wuga Formation are herein interpreted to be of Rhaetian age. Moreover, intercalated limestone and chert are termed the Dongnale Formation of Norian age. The Norian to Rhaetian succession can be correlated with strata of the central BNSZ as well as with deposits of the Lhasa Terrane and the South Qiangtang Terrane. Similar stratigraphies among these regions through the Late Triassic suggests a shared depositional setting and that the BNSZ was not an ocean in Norian and Rhaetian time.

scholarly journals The Upper Triassic - Lower Jurassic Vinding and Gassum Formations of the Norwegian-Danish Basin

1978 ◽  
Vol 3 ◽  
pp. 1-26
Author(s):  
Finn Bertelsen
Keyword(s):  
Lower Jurassic ◽  
Upper Triassic ◽  
Late Triassic ◽  
North German Basin ◽  
Sea Level Changes ◽  
Northern Margin ◽  
The North ◽  
Tectonic Events ◽  
Near Shore ◽  
German Basin

The late Triassic-early Jurassic Vinding and Gassum Formations are redefined and mapped within the Norwegian-Danish Basin. The Vinding Formation is a brackish marine shallow water deposit restricted to the Danish Subbasin. It is of late Norian-Rhaetian age. The Gassum Formation is a fluvio-deltaic to near-shore marine, arenaceous deposit carried from north and east into the basin. Its upper part is diachronous, ranging in age from Rhaetian in the basin center to late Sinemurian in the northern margin. It is proposed that the Ullerslev Formation is repealed. The parallelism between the course of sedimentation in the Norwegian-Danish Basin, the North German Basin and the Polish Basin indicates eustatic sea level changes to be of greater importance than local tectonic events.

THE PETROLEUM GEOLOGY OF THE OUTER DAMPIER SUB-BASIN

1978 ◽  
Vol 18 (1) ◽  
pp. 13
Author(s):  
A. Crostella ◽  
M. A. Chaney
Keyword(s):  
Middle Jurassic ◽  
Upper Cretaceous ◽  
Lower Jurassic ◽  
Upper Triassic ◽  
Petroleum Geology ◽  
Late Triassic ◽  
Well Data ◽  
Western Australian ◽  
Outer Area ◽  
Outer Section

The Dampier Sub-basin represents the northern part of a depositional downwarp along the Western Australian coast within the greater Carnarvon Basin. The sub-basin can be separated into an inner and outer section by the depositional Lewis Trough, which drilling and seismic results indicate to have been active since at least earliest Jurassic times.The Dampier Sub-basin originated as an intracratonic depocentre at the end of the Carboniferous and has developed progressively into a marginal basin at the present day. The oldest sediments penetrated to date in the outer area are fluviatile Upper Triassic clastics. Well data have shown that sedimentation continued without a break from the Late Triassic until the late Middle Jurassic, with gradually increasing marine influences. This phase of deposition was terminated by uplift in the Early Callovian, resulting in the emergence of various parts of the basin. These areas were transgressed at different stages, but by the late Early Cretaceous a marine environment was firmly established over the whole region.Eleven hydrocarbon accumulations have been discovered to date in the Outer Dampier Sub-basin where the primary hydrocarbon generating section is believed to consist of pre- Upper Cretaceous shales, particularly in the Lewis Trough. The feature of major relevance to the petroleum geology is the Rankin Platform where the main discoveries occur in Triassic to Lower Jurassic reservoirs. Trapping is provided primarily by the drape and differential compaction of Cretaceous shales over the pre-tectonic horsts, but the water level in individual fields appears to depend on a combination of both drape and fault trapping. In the Angel Field, on the Madeleine Trend, hydrocarbons occur in Tithonian sands within a fold structure sealed by conformable Cretaceous shales.

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