Geology and U–Pb geochronology of the Klondike District, west-central Yukon Territory

1990 ◽  
Vol 27 (7) ◽  
pp. 903-914 ◽  
Author(s):  
J. K. Mortensen
Keyword(s):  
Large Body ◽  
Yukon Territory ◽  
Geological Mapping ◽  
Late Triassic ◽  
Second Phase ◽  
Small Bodies ◽  
Thrust Faulting ◽  
New Information ◽  
Metavolcanic Rocks ◽  
Thrust Sheets

Geological mapping and U–Pb geochronology of the Klondike District provide new information on the nature and evolution of the Yukon–Tanana terrane (YTT) in western Yukon. The area is underlain by a sequence of thrust panels of regional extent. A continuously mappable sequence of interlayered metasedimentary and metavolcanic rocks is intruded by a variety of deformed metaplutonic rocks within two of these thrust sheets. Layering in the metasediments and metavolcanics is considered to be at least in part transposed stratigraphy. Small bodies of greenstone and altered ultramafic rocks thought to be part of the Slide Mountain terrane occur discontinuously along the thrust faults.U–Pb age determinations indicate that the uppermost thrust panel (assemblage I), which underlies much of the Klondike District, consists largely of metamorphosed, mid-Permian felsic plutonic, subvolcanic, and tuffaceous rocks. Beneath assemblage I is a second thrust panel (assemblage II), also of large areal extent, of mid-Paleozoic or older metasedimentary and mafic and felsic metavolcanic rocks, intruded by a large body of latest Devonian – Early Mississippian granitic augen orthogneiss. U–Pb analyses of zircon from the orthogneiss reflect both lead loss and a significant inherited zircon component. A third structural unit (assemblage III), which consists mainly of carbonaceous schist and phyllite, crops out in the northern part and along the southwestern edge of the study area, where it underlies both assemblages I and II.The earliest stage of deformation and metamorphism that affected the area (F1) produced the pervasive recrystallization fabric characteristic of all of the metamorphic rocks in assemblages I, II, and III, and occurred between mid-Permian and Late Triassic time. Thrust faulting, presumed to be northerly or northeasterly directed, postdates Late Triassic but predates mid-Cretaceous. The second phase of deformation (F2) was either synchronous with or later than thrust faulting. Monazite ages for the augen orthogneiss indicate that at least local metamorphism and (or) deformation lasted until Early Cretaceous time.Close similarities between composition, U–Pb ages, as well as timing and style of deformation, documented in the Klondike District and observed elsewhere in the YTT in southeastern Yukon and east-central Alaska suggest that much of the YTT either evolved as a single entity or else shared a very similar history.

Geological setting and tectonic significance of Mississippian felsic metavolcanic rocks in the Pelly Mountains, southeastern Yukon Territory

1982 ◽  
Vol 19 (1) ◽  
pp. 8-22 ◽  
Author(s):  
James K. Mortensen
Keyword(s):  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Yukon Territory ◽  
Early Tertiary ◽  
Metavolcanic Rocks ◽  
Extensional Tectonic ◽  
Tectonic Significance ◽  
Show Evidence ◽  
Thrust Sheets ◽  
Local Geology

The central Pelly Mountains in southeastern Yukon Territory consist of imbricate thrust sheets, which have undergone syn- and post-thrusting deformation and metamorphism. The local geology is further complicated by the intrusion of Late Cretaceous batholiths, and by strike-slip faulting related to the Tintina Fault, a major northwest-trending transcurrent fault of latest Cretaceous or early Tertiary age. This faulting disrupts the northeast edge of the study area.Upper Devonian and Mississippian strata are present in at least two of the structural packages, but the Mississippian metavolcanic rocks occur only in the lowermost package. Rb–Sr geochronology indicates a mid-Mississippian age for the igneous suite. The volcanic rocks consist of volcaniclastic material with minor interbedded flows, and were deposited in a submarine environment. Several coeval and cogenetic syenite and trachyte domes and small stocks are the remains of vent areas. Although the volcanic rocks are all highly altered and show evidence of widespread chemical mobility, trace element data indicate that the rocks are metaluminous trachytes, most closely resembling peralkaline volcanics generated in extensional environments. This suggestion of a predominantly extensional tectonic setting in mid-Mississippian time in the Pelly Mountains is consistent with recent tectonic syntheses for the area.

scholarly journals Genetic testing of dogs predicts problem behaviors in clinical and nonclinical samples

2020 ◽  
Author(s):  
Isain Zapata ◽  
M. Leanne Lilly ◽  
Meghan E. Herron ◽  
James A. Serpell ◽  
Carlos E. Alvarez
Keyword(s):  
Body Size ◽  
Problem Behaviors ◽  
Small Body ◽  
Community Sample ◽  
Large Body ◽  
Second Phase ◽  
Logistic Regression Models ◽  
Individual Level ◽  
Increased Risk ◽  
Phenotype Data

AbstractVery little is known about the etiology of personality and psychiatric disorders. Because the core neurobiology of many such traits is evolutionarily conserved, dogs present a powerful model. We previously reported genome scans of breed averages of ten traits related to fear, anxiety, aggression and social behavior in multiple cohorts of pedigree dogs. As a second phase of that discovery, here we tested the ability of markers at 13 of those loci to predict canine behavior in a community sample of 397 pedigree and mixed-breed dogs with individual-level genotype and phenotype data. We found support for all markers and loci. By including 122 dogs with veterinary behavioral diagnoses in our cohort, we were able to identify eight loci associated with those diagnoses. Logistic regression models showed subsets of those loci could predict behavioral diagnoses. We corroborated our previous findings that small body size is associated with many problem behaviors and large body size is associated with increased trainability. Children in the home were associated with anxiety traits; illness and other animals in the home with coprophagia; working-dog status with increased energy and separation-related problems; and competitive dogs with increased aggression directed at familiar dogs, but reduced fear directed at humans and unfamiliar dogs. Compared to other dogs, Pit Bull-type dogs were not defined by a set of our markers and were not more aggressive; but they were strongly associated with pulling on the leash. Using severity-threshold models, Pit Bull-type dogs showed reduced risk of owner-directed aggression (75th quantile) and increased risk of dog-directed fear (95th quantile). Our findings have broad utility, including for clinical and breeding purposes, but we caution that thorough understanding is necessary for their interpretation and use.

scholarly journals The evolution of the Triassic-Jurassic Maliac oceanic lithosphere: insights from the supra-ophiolitic series of Othris (continental Greece)

2015 ◽  
Vol 186 (6) ◽  
pp. 399-411 ◽  
Author(s):  
Jacky Ferrière ◽  
Frank Chanier ◽  
Peter O. Baumgartner ◽  
Paulian Dumitrica ◽  
Martial Caridroit ◽  
...  
Keyword(s):  
Continental Crust ◽  
Late Jurassic ◽  
Structural Data ◽  
Oceanic Lithosphere ◽  
Late Triassic ◽  
Major Result ◽  
Data Set ◽  
Thrust Sheets ◽  
Sedimentary Succession ◽  
Major Reference

AbstractMajor ophiolitic thrust sheets are widespread within the internal Hellenides, particularly in the Pelagonian domain (Greece and Albania). The ophiolitic sheets are notably well exposed in western Othris mountains of continental Greece. In that area, the structural stacking of oceanic nappes obducted in the Jurassic is particularly well constrained. New sedimentological and structural data from recently studied outcrops, together with new micro-paleontological data, allow to reconsider the architecture of the ophiolitic nappes and their evolution in the Othris mountains. Our new data set includes notably the description of a Mid-Late Jurassic sedimentary succession, from basal litharenites and radiolarites to syn-obduction mélange, on top of the uppermost Mega Isoma ophiolitic Unit. These results are crucial in the perspective of constraining the Jurassic contractional evolution of the Maliac Ocean from the beginning of the subduction and intra-oceanic obduction to the final obduction on the Pelagonian continental crust. Another major result concerns the dating of primary conformable series of Middle and Late Triassic age on top of the pillow-lavas of the Fourka unit. Since this lava unit, with MORB affinities, is one of the syn-obduction Jurassic nappes, we propose that this very large Fourka nappe represents the major reference unit of the initial (Triassic) Maliac oceanic crust.

Walcot Gibson 1864-1941

1943 ◽  
Vol 4 (12) ◽  
pp. 271-275
Keyword(s):  
East Africa ◽  
Geological Structure ◽  
Geological Mapping ◽  
Geological Survey ◽  
Intimate Contact ◽  
The North ◽  
South Wales ◽  
New Information ◽  
Original Survey ◽  
The One

Walcot Gibson was born at Bromsgrove, Worcestershire, on 24 August 1864. His father was a bank manager from the north country and his mother was Cornish, and they had three sons and one daughter. Gibson was educated at the Bromsgrove School and about 1882 went to Mason College, Birmingham, now the University of Birmingham. Charles Lapworth who had distinguished himself by his great researches in the south of Scotland had just been appointed to the chair of Geology at Mason College and thirty-one years later (1913) he records that Gibson was his first geological pupil. His interest in geology and geological mapping was developed by intimate contact with Lapworth and was sustained by a coterie of ardent amateur geologists, among them Joseph Landon, Fred Cullis and C. J. Gilbert. This period clearly determined Gibson’s choice of a career. After a course at the Royal College of Science he set out in 1889 on Lapworth’s advice for South Africa where he was engaged for two years on mineral surveys in the Rand goldfields and elsewhere. From there he moved to East Africa where he was engaged for another two years on mineral surveys for the East Africa Company. He returned to this country an experienced geologist and surveyor and in 1893 he joined H.M. Geological Survey in which service he remained for thirty-two years until his retirement in 1925. This was an important period in the history of the Geological Survey for owing to strong representations that the old Survey had become obsolete both in topography and geology, the House of Commons in 1891 sanctioned a resurvey of the great South Wales Coalfield on the scale of six inches to the mile. The first mapping of that field initiated by Logan and de la Beche was on the one-inch scale and was completed about 1845, the year in which the Geological Survey was transferred from the Board of Ordnance. The enormous developments which had taken place since the original survey had far outstripped the knowledge of the geological structure of the field and new information had become urgently necessary.

Neotethyan evolution of eastern Greece (Pagondas Mélange, Evia island) inferred from radiolarian biostratigraphy and the geochemistry of associated extrusive rocks

2001 ◽  
Vol 138 (3) ◽  
pp. 345-363 ◽  
Author(s):  
TANIEL DANELIAN ◽  
ALASTAIR H. F. ROBERTSON
Keyword(s):  
Shallow Water ◽  
Carbonate Platform ◽  
Ocean Basin ◽  
Passive Margin ◽  
Late Triassic ◽  
Geochemical Data ◽  
Chemical Compositions ◽  
Similar Chemical ◽  
Thrust Sheets ◽  
Age Range

This paper presents new radiolarian biostratigraphic and igneous/metamorphic geochemical data for a Mesozoic volcanic–sedimentary mélange on the island of Evia (Euboea or Evvoia), eastern Greece. This mélange includes dismembered thrust sheets and blocks of radiolarian chert and basalt. Biostratigraphic age data show that radiolarites interbedded with basalt-derived, coarse clastic sediments near the base of a coherent succession were deposited in Middle and Late Triassic time (Late Ladinian–Carnian, Norian?). Geochemical evidence shows that associated extrusive rocks, of inferred Triassic age, range from ‘enriched’ alkaline basalts, to ‘transitional’ basalts, and more ‘depleted’ mid-ocean ridge-type basalts. Amphibolite facies meta-basalts from the metamorphic sole of the over-riding Evia ophiolite exhibit similar chemical compositions. Both the basalts and the meta-basalts commonly show an apparent subduction-related influence (e.g. relative Nb depletion) that may have been inherited from a previous subduction event in the region. The basalts are interpreted to have erupted during Middle–Late Triassic time (Late Ladinian–Carnian), related to initial opening of a Neotethyan ocean basin adjacent to a rifted continental margin. Radiolarites located stratigraphically higher in the coherent succession studied are dated as Middle Jurassic (Late Bathonian–Early Callovian). Similar-aged radiolarites are depositionally associated with ophiolitic rocks (including boninites), in some other areas of Greece and Albania. During initial ocean basin closure (Bajocian–Bathonian) the adjacent shallow-water carbonate platform (Pelagonian zone) disintegrated to form basins in which siliceous sediments were deposited and highs on which shallow-water carbonates continued to accumulate. This facies differentiation is seen as a response to crustal flexure as the Neotethyan ocean began to close. The over-riding Pagondas Mélange and other similar units in the region are interpreted as accretionary prisms related to subduction of Neotethyan oceanic crust in Middle–Late Jurassic time. These mélanges were emplaced, probably diachronously during Oxfordian–Kimmeridgian time, when the passive margin collapsed, creating a foredeep ahead of advancing thrust sheets of mélange and ophiolites.

The Northern Sea Route, 1999–2000

Polar Record ◽  
2001 ◽  
Vol 37 (203) ◽  
pp. 329-336 ◽  
Author(s):  
Lawson W. Brigham
Keyword(s):  
Large Body ◽  
Arctic Sea Ice ◽  
Decision Makers ◽  
Russian Arctic ◽  
Shipping Company ◽  
Marine Transport ◽  
Northern Sea Route ◽  
New Information ◽  
Arctic Sea ◽  
Dominant Operator

AbstractAt the end of the twentieth century, Russia's Northern Sea Route (NSR) has functioned primarily as a domestic marine transport system with Murmansk Shipping Company as the dominant operator and facilitator. Total cargo along the NSR in 1999 was 1.58 million tons; during 1997–99 no through transit cargo was carried on the NSR. The International NSR Programme (INSROP), backed by Japanese, Norwegian, and Russian interests, concluded in November 1999 with a key user conference in Oslo. The six-year (1993–99) INSROP effort produced a large body of new information about the NSR and Russian Arctic that decision-makers will find valuable in planning future ventures in the region. Concerns have been expressed in Russia for the ageing icebreaker fleet that has been the backbone of all NSR operations since the 1950s. Several nuclear icebreakers have been refuelled and, although detailed plans for a replacement fleet of nuclear and diesel-electric ships have been developed, financing has not been identified. As Arctic sea ice continues to decline in extent and thickness, the impacts on future NSR operations will be significant considerations for future operations.

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.

Geological mapping of the 1985 Chinese—British Tibetan (Xizang—Qinghai) Plateau Geotraverse route

1988 ◽  
Vol 327 (1594) ◽  
pp. 287-305 ◽  
Keyword(s):  
Strike Slip ◽  
Geological Mapping ◽  
Strike Slip Fault ◽  
Fault System ◽  
Late Triassic ◽  
Clastic Rocks ◽  
The North ◽  
Opposite Sequence ◽  
Geological Map ◽  
Qiangtang Terrane

The 1:500,000 coloured geological map of the traverse route combines observations from the Geotraverse, previous mapping, and interpretation of orbital images. The position of all localities visited by Geotraverse participants and basic geological data collected by them along the traverse route are shown on a set of maps originally drawn at 1:100,000 scale, reproduced on microfiche for this publication. More detailed mapping, beyond a single line of section, was achieved in five separate areas. The relationships between major rock units in these areas, and their significance, are outlined in this paper. Near Gyanco, (Lhasa Terrane) an ophiolite nappe, apparently connected with outcrops of ophiolites in the Banggong Suture about 100 km to the north, was under thrust by a discontinuous slice of Carboniferous—Permian clastic rocks and limestone, contrary to a previous report of the opposite sequence. At Amdo, a compressional left-lateral strike-slip fault zone has modified relationships along the Banggong Suture. Near Wuli, (northern Qiangtang Terrane) limited truncation of Triassic strata at the angular unconformity below Eocene redbeds demonstrates that most of the folding here is of Tertiary age. The map of the nearby Erdaogou region displays strong fold and thrust-shortening of the Eocene redbeds, evidence of significant crustal shortening after the India- Asia collision began. In the Xidatan-Kunlun Pass area, blocks of contrasting Permo—Triassic rocks are separated by east-trending faults. Some of these faults are ductile and of late Triassic — early Jurassic age, others are brittle and part of the Neogene—Quaternary Kunlun leftlateral strike-slip fault system. Some more significant remaining problems that geological mapping might help to solve are discussed briefly, including evidence for a possible additional ophiolitic suture within the Qiangtang Terrane.

scholarly journals The first juvenile specimens of Plateosaurus engelhardti from Frick, Switzerland: Isolated neural arches and their implications for developmental plasticity in a basal sauropodomorph

2014 ◽  
Author(s):  
Rebecca Hofmann ◽  
P. Martin Sander
Keyword(s):  
Body Size ◽  
Developmental Plasticity ◽  
Large Body ◽  
Late Triassic ◽  
Poor Correlation ◽  
Time Averaging ◽  
Large Body Size ◽  
Alternative Hypotheses ◽  
Histological Data ◽  
Multiple Species

The dinosaur Plateosaurus engelhardti is the most abundant dinosaur in the Late Triassic of Europe and the best known basal sauropodomorph. Plateosaurus engelhardti was one of the first sauropdomorph dinosaurs to display a large body size. Remains can be found in the Norian stage of the Late Triassic in over 40 localities in Central Europe (France, Germany, Greenland and Switzerland). Since the first discovery of P. engelhardti no juvenile specimens of this species had been found. Here we describe the first remains of juvenile individuals, isolated cervical and dorsal neural arches. These were separated postmortem from their respective centra because of unfused neurocentral sutures. However the specimens share the same neural arch morphology found in adults. Morphometric analysis suggests a body lengths of the juvenile indivduals that is greater than those of most adult specimens. This supports the hypothesis of developmental plasticity in Plateosaurus engelhardti that previously had been based on histological data only. Alternative hypotheses for explaining the poor correlation between ontogenetic stage and size in this taxon are multiple species or sexual morphs with little morphological variance or time-averaging of individuals from populations differing in body size.

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