Geology of the Nemo Lakes belt, northern Valhalla Range, southeast British Columbia

1981 ◽  
Vol 18 (5) ◽  
pp. 944-958 ◽  
Author(s):  
Randall R. Parrish
Keyword(s):  
British Columbia ◽  
Large Scale ◽  
Phase 1 ◽  
Normal Fault ◽  
Columbia River ◽  
Ultramafic Rocks ◽  
Phase 2 ◽  
Metasedimentary Rocks ◽  
The North ◽  
Gneiss Complex

High-grade metasedimentary rocks, probably of both early Paleozoic and late Paleozoic – Triassic ages, underlie an area termed the Nemo Lakes belt between Slocan and Arrow Lakes in the northern Valhalla Range, southeastern British Columbia. The rocks have experienced two possibly related periods of major folding. Phase 1, accompanied and outlasted by metamorphism at P–T conditions of 5.0–6.8 kbar (500–680 MPa) and 630–680 °C, involved emplacement of ultramafic rocks, major faulting, and folding. Phase 2 involved large-scale inclined to upright folds which were dominantly south-verging, deforming the phase 1 fabric. Both phases probably occurred in the Middle to Late Jurassic, as part of the Columbian Orogeny.Rocks lithologically and structurally similar to those of the Nemo Lakes belt are found across the Rodd Creek fault near the Columbia River and extend the general continuity of the belt into the Shuswap metamorphic complex.Plutonic rocks, some of which bracket the movement on the Rodd Creek fault, the southern extension of the Columbia River fault zone, range in age from Middle Jurassic to EoceneIn the valley of Slocan Lake, a major normal fault is postulated on structural and metamorphic grounds and may be related to the north–south arching of the Valhalla gneiss complex. It is suggested that this arching and uplift, which followed phase 2 deformation, produced both the fault and a zone of cataclasis on the eastern side of the complex, and gave rise to its domal shape.

Stratigraphy and structure of the Kootenay Arc in the Riondel area, southeastern British Columbia

1977 ◽  
Vol 14 (10) ◽  
pp. 2301-2315 ◽  
Author(s):  
Trygve Höy
Keyword(s):  
Root Zone ◽  
Phase 1 ◽  
Small Scale ◽  
Reverse Fault ◽  
Lake Area ◽  
Phase 2 ◽  
The West ◽  
Lower Paleozoic ◽  
Metasedimentary Rocks ◽  
The North

The succession of metasedimentary rocks in the Riondel area is correlated with a Hadrynian–Cambrian sequence established in the Duncan Lake area to the north and the Salmo area to the south. The succession includes phyllite, schist, and quartz-pebble conglomerate of the Horset hie f Creek Group; quartzite, siltstone, and schist of the Hamill Group; calcareous schist of the Mohican Formation; and a prominent marble, the Badshot Formation. The youngest metasedimentary rocks include para-amphibolite, calc-silicate gneiss, and pelitic schist of the Lardeau Group.A lower Paleozoic succession of metasedimentary locks in the western part of the Riondel area forms a large overturned panel which is the lower limb of a phase 1 recumbent anticline, the 'Riondel nappe'. The root zone of the nappe is inferred to lie beneath a west-dipping reverse fault, the 'West Bernard fault', which separates the inverted panel of rocks on the west from the right-way-up panel in the east. Tight to isoclinal north–south trending phase 2 folds with upright to west-dipping axial surfaces and sub-horizontal fold axes are superposed on the Riondel nappe. Small-scale, south westerly trending phase 3 warps and open folds are overprinted on the limps of the older folds.The age of the Riondel nappe cannot be positively determined. It is assumed to have developed during the Caribooan orogeny in Devono-Mississippian (?) time and subsequently to have been deformed by phase 2 folding and associated faulting in middle Jurassic to early Cretaceous time.

scholarly journals Tilt and strain change during the explosion at Minami-dake, Sakurajima, on November 13, 2017

2021 ◽  
Author(s):  
Kohei Hotta ◽  
Masato Iguchi
Keyword(s):  
Ground Deformation ◽  
Large Strain ◽  
Phase 1 ◽  
Small Strain ◽  
Phase 2 ◽  
The North ◽  
Strombolian Eruption ◽  
Strain Change ◽  
Tilt Change

Abstract We herein propose an alternative model for deformation caused by an eruption at Sakurajima, which have been previously interpreted as being due to a Mogi-type spherical point source beneath Minami-dake. On November 13, 2017, a large explosion with a plume height of 4,200 m occurred at Minami-dake. During the three minutes following the onset of the explosion (November 13, 2017, 22:07–22:10 (Japan standard time (UTC+9); the same hereinafter), phase 1, a large strain change was detected at the Arimura observation tunnel (AVOT) located approximately 2.1 km southeast from the Minami-dake crater. After the peak of the explosion (November 13, 2017, 22:10–24:00), phase 2, a large deflation was detected at every monitoring station due to the continuous Strombolian eruption. Subsidence toward Minami-dake was detected at five out of six stations whereas subsidence toward the north of Sakurajima was detected at the newly installed Komen observation tunnel (KMT), located approximately 4.0 km northeast from the Minami-dake crater. The large strain change at AVOT as well as small tilt changes of all stations and small strain changes at HVOT and KMT during phase 1 can be explained by a very shallow deflation source beneath Minami-dake at 0.1 km below sea level (bsl). For phase 2, a deeper deflation source beneath Minami-dake at a depth of 3.3 km bsl was found in addition to the shallow source beneath Minami-dake which turned inflation after the deflation obtained during phase 1. However, this model cannot explain the tilt change of KMT. Adding a spherical deflation source beneath Kita-dake at a depth of 3.2 km bsl can explain the tilt and strain change at KMT and the other stations. The Kita-dake source was also found in a previous study of long-term ground deformation. Not only the deeper Minami-dake source MD but also the Kita-dake source deflated due to the Minami-dake explosion.

Origin of the Tulameen ultramafic-gabbro complex, southern British Columbia

1969 ◽  
Vol 6 (3) ◽  
pp. 399-425 ◽  
Author(s):  
D. C. Findlay
Keyword(s):  
British Columbia ◽  
Internal Structure ◽  
Fractional Crystallization ◽  
Volcanic Rocks ◽  
Age Determination ◽  
Upper Triassic ◽  
Ultramafic Rocks ◽  
Metasedimentary Rocks ◽  
Gabbroic Intrusion

The Tulameen Complex is a composite ultramafic-gabbroic intrusion that outcrops over 22 sq. mi. (57 km2) in the Southern Cordillera of British Columbia. The complex intruded Upper Triassic metavolcanic and metasedimentary rocks of the Nicola Group, and on the basis of geologic relations and a K–Ar age determination (186 m.y.) is tentatively dated as Late Triassic.The principal ultramafic units — dunite, olivine clinopyroxenite, and hornblende clinopyroxenite — form an elongate, non-stratiform body whose irregular internal structure is best explained by deformation contemporaneous with crystallization of the rocks. The derivation of the ultramafic rocks is attributed to fractional crystallization of an ultrabasic magma. The gabbroic mass, which consists of syenogabbro and syenodiorite, partly borders and partly overlies the ultramafic body and was apparently intruded by it.The ultramafic and gabbroic parts of the complex probably formed from separate intrusions of different magmas, but the two suites have sufficient mineralogical and chemical features in common to indicate an ultimate petrogenic affinity of the magmas. Comparison of the Tulameen rocks with nearby intrusions of the same general age, in particular the Copper Mountain stock, suggests that they are members of a regional suite of alkalic intrusions. The possibility is also raised that these intrusions may be comagmatic with the Nicola volcanic rocks.

scholarly journals The country rocks of Devonian magmatism in the North Patagonian Massif and Chaitenia

2018 ◽  
Vol 45 (3) ◽  
pp. 301 ◽  
Author(s):  
Francisco Hervé ◽  
Mauricio Calderón ◽  
Mark Fanning ◽  
Robert Pankhurst ◽  
Carlos W. Rapela ◽  
...  
Keyword(s):  
Metamorphic Grade ◽  
Oceanic Island ◽  
Detrital Zircons ◽  
Island Arc ◽  
Ultramafic Rocks ◽  
The West ◽  
Metasedimentary Rocks ◽  
The North ◽  
The Andes ◽  
Late Neoproterozoic

Previous work has shown that Devonian magmatism in the southern Andes occurred in two contemporaneous belts: one emplaced in the continental crust of the North Patagonian Massif and the other in an oceanic island arc terrane to the west, Chaitenia, which was later accreted to Patagonia. The country rocks of the plutonic rocks consist of metasedimentary complexes which crop out sporadically in the Andes on both sides of the Argentina-Chile border, and additionally of pillow metabasalts for Chaitenia. Detrital zircon SHRIMP U-Pb age determinations in 13 samples of these rocks indicate maximum possible depositional ages from ca. 370 to 900 Ma, and the case is argued for mostly Devonian sedimentation as for the fossiliferous Buill slates. Ordovician, Cambrian-late Neoproterozoic and “Grenville-age” provenance is seen throughout, except for the most westerly outcrops where Devonian detrital zircons predominate. Besides a difference in the Precambrian zircon grains, 76% versus 25% respectively, there is no systematic variation in provenance from the Patagonian foreland to Chaitenia, so that the island arc terrane must have been proximal to the continent: its deeper crust is not exposed but several outcrops of ultramafic rocks are known. Zircons with devonian metamorphic rims in rocks from the North Patagonian Massif have no counterpart in the low metamorphic grade Chilean rocks. These Paleozoic metasedimentary rocks were also intruded by Pennsylvanian and Jurassic granitoids.

scholarly journals Observation of ENSO linked changes in the tropical Atlantic cloud vertical distribution using 14 years of MODIS observations

2019 ◽  
Author(s):  
Nils Madenach ◽  
Cintia Carbajal Henken ◽  
René Preusker ◽  
Odran Sourdeval ◽  
Jürgen Fischer
Keyword(s):  
Vertical Distribution ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Phase 1 ◽  
Tropical Atlantic ◽  
Phase 2 ◽  
High Cloud ◽  
La Nina ◽  
Linear Decrease

Abstract. 14 years (September 2002 to September 2016) of Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) monthly mean cloud data is analyzed to identify possible changes of the cloud vertical distribution over the Tropical Atlantic Ocean (TAO). For the analysis multiple linear regression techniques are used. Within the investigated period, no significant trend in the domain-averaged cloud vertical distribution was found. In terms of linear changes, two major phases (before and after November 2011) in the time-series of the TAO domain-average Cloud Top Height (CTH) and High Cloud Fraction (HCF) can be distinguished. While phase 1 is dominated by a significant linear increase, phase 2 is characterized by a strong, significant linear decrease. The observed trends were mainly caused by the El Niño Southern Oscillation (ENSO). The increase in CTH and HCF in phase 1, was attributed to the transition from El Niño (2002) to La Niña (2011) conditions. The strong decrease in phase 2, was caused by the opposite transition from a La Niña (2011) to a major El Niño event (2016). A comparison with the large scale vertical motion ω at 500 hPa obtained from ERA-Interim ECMWF Re-Analyses and the Nino3.4-Index indicates that the changes in HCF are induced by ENSO linked changes in the large scale vertical upward movements over regions with strong large scale ascent. A first comparison with the DARDAR data set, which combines CloudSat radar and CALIPSO lidar measurements, shows qualitatively good agreements for the interannual variability of the high cloud amount and its linear decrease in phase 2.

Evolution of the Slocan Syncline in south-central British Columbia

1968 ◽  
Vol 5 (4) ◽  
pp. 851-872 ◽  
Author(s):  
John V. Ross ◽  
P. Kellerhals
Keyword(s):  
British Columbia ◽  
Phase 1 ◽  
Granite Gneiss ◽  
Phase 2 ◽  
Phase 3 ◽  
The Core ◽  
South Central ◽  
Deformation Phase ◽  
Facies Metamorphism ◽  
The One

The Slocan Syncline, located in the center of the Kootenay Arc, south-central British Columbia, is outlined in its core by deformed Triassic sediments—the Slocan Group. These deformed sediments were originally deposited unconformably into a synform developed on the upward-facing limb of a recumbent, eastward-closing anticline, comprising Paleozoic and older rocks.The first phase of deformation resulted in the development of a recumbent anticline closing to the east. This anticline involved a sequence of rocks ranging in age from Windermere (late Precambrian—Horsethief Creek Group) up to Permian (Milford Group) and was originally developed along almost horizontal axes contained in an axial-plane having a shallow westerly dip. The core of this anticline contains granite gneiss, having a history pre-dating the deposition of the Horsethief Creek Group, which is in imbricate relation with the gneiss.Later, phase 2 deformation refolded this recumbent anticline into a synform and a westerly complementary antiform along shallow southeasterly axes contained within axial planes dipping southwesterly at about 45 degrees. Amphibolite-facies metamorphism (the "Shuswap Metamorphism") accompanied these phases of deformation and culminated in phase 2 time. Phase 1 and phase 2 deformation and metamorphism ate dated at post-Milford Group (Permian) and pre-Slocan Group (Triassic).Slocan Group (Triassic) sediments were deposited into the phase 2 synform, whose limbs consist of variable older rocks. A later non-metamorphic deformation, phase 3, along southeasterly striking axial planes dipping steeply to the northeast tightened the earlier phase 1 anticline and the phase 2 synform, and produced the Slocan Syncline. The Triassic sediments exhibit only phase 3 structures and are cut by the Nelson batholith dated at 171 × 106 years (Early Jurassic). Phase 3 deformation is then dated at post-Triassic and pre-Early Jurassic.Structural and stratigraphic evidence suggests that the phase 1 recumbent anticline herein described is but one of a set of nappes disposed structurally above and below the one presently described, and that the Kootenay Arc is an old structure perhaps resulting from interference of phase 1 and phase 2 deformations.

Development of New Design Fatigue Curves in Japan: Discussion of Best-Fit Curves Based on Large-Scale Fatigue Tests of Carbon and Low-Alloy Steel Plates

2018 ◽  
Author(s):  
Masahiro Takanashi ◽  
Hiroshi Ueda ◽  
Toshiyuki Saito ◽  
Takuya Ogawa ◽  
Kentaro Hayashi
Keyword(s):  
Large Scale ◽  
Phase 1 ◽  
Fatigue Curve ◽  
Fatigue Tests ◽  
Steel Plates ◽  
Phase 2 ◽  
Test Results ◽  
Low Alloy Steel ◽  
Best Fit ◽  
Deep Crack

In Japan, the Design Fatigue Curve (DFC) Phase 1 and Phase 2 subcommittees were organized under the Atomic Energy Research Committee in the Japan Welding Engineering Society and have proposed new design fatigue curves for carbon, low-alloy, and austenitic stainless steels. To confirm the validity of the proposed design fatigue curves, a Japanese utility collaborative project was launched. In this project, fatigue tests were conducted on large-scale and small-sized specimens, and the test data were provided to the DFC Phase 2 subcommittee. This paper discusses the best-fit curves proposed by the DFC Phase 1 subcommittee, focusing on the results of large-scale fatigue tests for carbon steel and low-alloy steel plates. The fatigue test results for large-scale specimens were compared with the best-fit curve proposed by the DFC Phase 1 subcommittee. This comparison revealed that the fatigue lives given by the proposed curves correspond to those of approximately 1.5–4.0-mm-deep crack initiation in large-scale specimens. In this program, fatigue tests with a mean strain were also carried out on large-scale specimens. These tests found that the fatigue lives were almost equivalent to those of approximately 4.4–7.0-mm-deep crack initiation in large-scale specimens. In determining a design fatigue curve, strain-controlled tests are usually performed on small-sized specimens, and the fatigue life is then defined by the 25% load drop. It is reported that the cracks reach nearly 3–4-mm depth under those 25% drop cycles. The test results confirm that the fatigue lives of large-scale specimens agree with those given by the best-fit curve for carbon and low-alloy steels, and no remarkable size effects exist for the crack depths compared in this study.

The North American Multimodel Ensemble: Phase-1 Seasonal-to-Interannual Prediction; Phase-2 toward Developing Intraseasonal Prediction

2014 ◽  
Vol 95 (4) ◽  
pp. 585-601 ◽  
Author(s):  
Ben P. Kirtman ◽  
Dughong Min ◽  
Johnna M. Infanti ◽  
James L. Kinter ◽  
Daniel A. Paolino ◽  
...  
Keyword(s):  
North American ◽  
Phase 1 ◽  
Phase 2 ◽  
Multimodel Ensemble ◽  
The North ◽  
North American Multimodel Ensemble

Structural and metamorphic relationships between the Mount Ida and Monashee Groups at Mara Lake, British Columbia

1982 ◽  
Vol 19 (2) ◽  
pp. 288-307 ◽  
Author(s):  
Kent C. Nielsen
Keyword(s):  
British Columbia ◽  
Large Scale ◽  
Ductile Deformation ◽  
Late Triassic ◽  
Second Phase ◽  
The West ◽  
Late Mesozoic ◽  
The North ◽  
Phase Deformation ◽  
Metamorphic Core

Mara Lake, British Columbia straddles the boundary between the Monashee Group on the east and the Mount Ida Group on the west. Correlation of units across the southern end of Mara Lake indicates lithologic continuity between parts of the groups. Both groups have experienced four phases of deformation. Phases one and two are tight and recumbent, trending to the north and to the west, respectively. Phases three and four are open to closed and upright, trending northwest and northeast, respectively. Second-phase deformation includes large-scale tectonic slides that separate areas of consistent vergence. Slide surfaces are folded by third- and fourth-phase structures and outline domal outcrop patterns. Metamorphic grade increases from north to south along the west side of Mara Lake. Calc-silicate reactions involving the formation of diopside are characteristic. From west to east increasing grade is evident in the reaction of muscovite + quartz producing sillimanite + K-feldspar + water. These prograde reactions are related to relative position in the second-phase structure. The highest grade is located near the lowest slide surface. Greenschist conditions accompanied phase-three deformation. Fourth phase is characterized by hydrothermal alteration, brittle fracturing, and local faulting. First-phase deformation appears to be pre-Late Triassic whereas second and third phases are post-Late Triassic and pre-Cretaceous. The fourth phase is part of a regional Tertiary event. The third folding event is correlated with the development of the Chase antiform and the second-phase folding is related to the pervasive east–west fabric of the Shuswap Complex. The timing of these events indicates that the metamorphic core zone of the eastern Cordillera was relatively rigid during the late Mesozoic foreland thrust development. Ductile deformation significantly preceded thrusting and developed a fabric almost at right angles to the trend of the thrust belt.

scholarly journals Middle to Late Devonian–Carboniferous collapse basins on the Finnmark Platform and in the southwesternmost Nordkapp basin, SW Barents Sea

Solid Earth ◽  
2018 ◽  
Vol 9 (2) ◽  
pp. 341-372 ◽  
Author(s):  
Jean-Baptiste P. Koehl ◽  
Steffen G. Bergh ◽  
Tormod Henningsen ◽  
Jan Inge Faleide
Keyword(s):  
Shear Zone ◽  
Fault Zone ◽  
Large Scale ◽  
Barents Sea ◽  
Normal Fault ◽  
Early Carboniferous ◽  
Normal Displacement ◽  
Late Devonian ◽  
The North ◽  
Caledonian Orogeny

Abstract. The SW Barents Sea margin experienced a pulse of extensional deformation in the Middle–Late Devonian through the Carboniferous, after the Caledonian Orogeny terminated. These events marked the initial stages of formation of major offshore basins such as the Hammerfest and Nordkapp basins. We mapped and analyzed three major fault complexes, (i) the Måsøy Fault Complex, (ii) the Rolvsøya fault, and (iii) the Troms–Finnmark Fault Complex. We discuss the formation of the Måsøy Fault Complex as a possible extensional splay of an overall NE–SW-trending, NW-dipping, basement-seated Caledonian shear zone, the Sørøya–Ingøya shear zone, which was partly inverted during the collapse of the Caledonides and accommodated top–NW normal displacement in Middle to Late Devonian–Carboniferous times. The Troms–Finnmark Fault Complex displays a zigzag-shaped pattern of NNE–SSW- and ENE–WSW-trending extensional faults before it terminates to the north as a WNW–ESE-trending, NE-dipping normal fault that separates the southwesternmost Nordkapp basin in the northeast from the western Finnmark Platform and the Gjesvær Low in the southwest. The WNW–ESE-trending, margin-oblique segment of the Troms–Finnmark Fault Complex is considered to represent the offshore prolongation of a major Neoproterozoic fault complex, the Trollfjorden–Komagelva Fault Zone, which is made of WNW–ESE-trending, subvertical faults that crop out on the island of Magerøya in NW Finnmark. Our results suggest that the Trollfjorden–Komagelva Fault Zone dies out to the northwest before reaching the western Finnmark Platform. We propose an alternative model for the origin of the WNW–ESE-trending segment of the Troms–Finnmark Fault Complex as a possible hard-linked, accommodation cross fault that developed along the Sørøy–Ingøya shear zone. This brittle fault decoupled the western Finnmark Platform from the southwesternmost Nordkapp basin and merged with the Måsøy Fault Complex in Carboniferous times. Seismic data over the Gjesvær Low and southwesternmost Nordkapp basin show that the low-gravity anomaly observed in these areas may result from the presence of Middle to Upper Devonian sedimentary units resembling those in Middle Devonian, spoon-shaped, late- to post-orogenic collapse basins in western and mid-Norway. We propose a model for the formation of the southwesternmost Nordkapp basin and its counterpart Devonian basin in the Gjesvær Low by exhumation of narrow, ENE–WSW- to NE–SW-trending basement ridges along a bowed portion of the Sørøya-Ingøya shear zone in the Middle to Late Devonian–early Carboniferous. Exhumation may have involved part of a large-scale metamorphic core complex that potentially included the Lofoten Ridge, the West Troms Basement Complex and the Norsel High. Finally, we argue that the Sørøya–Ingøya shear zone truncated and decapitated the Trollfjorden–Komagelva Fault Zone during the Caledonian Orogeny and that the western continuation of the Trollfjorden–Komagelva Fault Zone was mostly eroded and potentially partly preserved in basement highs in the SW Barents Sea.

Sign in / Sign up

Export Citation Format

Share Document