999 resultados para Geology--Argentina--Maps


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The Dummer Complex extends 180 km along the Precambrian - Paleozoic contact from Tamworth to Lake Simcoe. It is composed of coarse, angular Paleozoic clasts in discontinuous, pitted, hummocky deposits. Deposits are usually separated by bare or boulder strewn bedrock, but have been found in the southern drumlinized till sheet. Dummer Complex deposits show rough alignment with ice-flow. Eskers cross-cut many of the deposits. Dummer sediment subfacies are defined on the basis of dominant coarse grain size and lithology, which relate directly to the underlying Paleozoic formation. Three subglacial tills are identified based on the degree of comminution and distance of transport; the immature facies of the Dummer Complex; the mature facies of the drumlinized till sheet and; the submature facies which is transitional. Carbonate geochemistry was used for till-bedrock correlation in various grain sizes. Of the 3 Paleozoic formations underlying the Dummer Complex, the Gull River Fm. is geochemically distinctive from the Bobcaygeon and Verulam Formations using Ca, Mg, Sr, Cu, Mn, Fe and Na. The Bobcaygeon Fm. and Verulam Fm. can be differentiated using Ca and the Sr/Ca ratio. The immature facies from 1.0 phi and finer is dominated by the non-carbonate, long distance transported component which decreases slightly downice. The submature till facies contains more long distance material than the immature facies. Sr and Mn can be used to correlate the Gull River immature till facies to the underlying bedrock the other subfacies could not be distinguished from each other or their respective source formation. This method proved to be ineffective for sediments with greater than 35% non-carbonate component, due to leaching of elements by the dissolving acid.The Dummer Complex is produced subglacially , as the compressional ice encounters the permeable Paleozoic carbonates. The increased shear strength of the ice and pore pressures in the carbonates results in the basal ice zones becoming debris ladden. Cleaner ice overrides the basal debris . laden dead ice which then acts as the glacier bed. During retreat, the Simcoe lobe stagnates as flow is cut-off by the Algonquin Highlands.

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The Rankin Inlet area, on the west shore of Hudson Bay in the Northwest Territories, is in the Churchill Structural Province. Metamorphosed volcanic and sedimentary rocks, previously mapped as Archean and part of the Kaminak Group, underlie most of the area. The Rankin Inlet Group consists of greywacke, with minor conglomeratic greywacke, quartzite and dolomite, overlain by massive and pillowed basaltic flows. Gabbro sills intrude the sediments near the base of the volcanic sequence and three serpentinite sills outcrop at the base of the volcanic sequence. The sediments are in fault-contact with quartz monzonite to the south and were intruded by granitic rocks to the northwest. Two periods of folding were defined by the mapping. The first generation folds are recumbent isoclinal folds, with northwest-trending and northeast-dipping axial planes, formed through gravitational sliding. The second generation folds are symmetrically disposed about the axis of the granitic intrusion and have east-southeast trending and nearly vertical axial planes. Whole-rock analysis of 64 rock samples indicates that metasomatic alteration accompanied the intrusion of both the granitic rocks and the serpentinite. The volcanic rocks, gabbro and serpentinite were derived from a magma of oceanic tholeiitic affinities. The stratigraphic sequence and chemistry of the volcanic rocks of the Rankin Inlet Group indicate that this assemblage is correlative with the Hurwitz Group rather than the Kaminak Group and is therefore Aphebian in age.

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The Sand Creek Prospect is located within the eastern exposed margin of the Coast Plutonic Complex. The occurrence is a plug and dyke porphyry molybdenum deposit. The rock types, listed in decreasing age: 1) metamorphlc schists and gneisses; 2) diorite suite rocks - diorite, quartz diorite, tonalite; 3) rocks of andesitic composition; 4) granodiorites, coarse porphyritic granodiorite, quartzfeldspar porphyry, feldspar porphyry; and 5) lamprophyre. Hydrothermal alteration is known to have resulted from emplacement of the hornblende-feldspar porphyry through to the quartz-feldspar porphyry. Molybdenum mineralization is chiefly associated with the quartz-feldspar porphyry. Ore mineralogy is dominated by pyrite with subordinate molybdenite, chalcopyrite, covelline, sphalerite, galena, scheelite, cassiterite and wolframite. Molybdenite exhibits a textural gradation outward from the quartz-feldspar porphyry. That is, disseminated rosettes and rosettes in quartz veins to fine-grained molybdenite in quartz veins and potassic altered fractures to fine-grained molybdenite paint or 6mears in the peripheral zones. The quartz-feldspar porphyry dykes were emplaced in an inhomogeneous stress field. The trend of dykes, faults and shear zones is 0^1° to 063° and dips between 58° NW and 86* SE. Joint Pole distribution reflects this fault orientation. These late deformatior maxima are probably superimposed upon annuli representing diapiric emplacement of the plutons. A model of emplacement involving two magmatic pulses is given in the following sequence: Diorite pulse (i) dioritequartz diorite, (ii) tonalites; granodiorite pulse (iii) hornblende-fildspar microporphyry, hornblende/biotite porphyry, (iv) coarse grained granodiorite, (v) quartz-feldspar porphyry, (vi) feldspar porphyry, and (vii) lamprophyre. The combination of plutonic and coarse porphyritic textures, extensive propylitic overprinting of potassic alteration assemblages suggests that the. prospect represents the lower reaches of a porphyry system.

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The study area is situated in NE Newfoundland between Gander Lake and the north coast and on the boundary between the Gander and Botwood tectonostratigraphic zones (Williams et al., 1974). The area is underlain by three NE trending units; the Gander Group, the Gander River Ultramafic Belt (the GRUB) and the Davidsville Group. The easternmost Gander Group consists of a thick, psammitic unit composed predominantly of psammitic schist and a thinner, mixed unit of semipelitic and pelitic schist with minor psammite. The mixed unit may stratigraphically overlie the psammitic unit or be a lateral facies equivalent of the latter. No fossils have been recovered from the Gander Group. The GRUB is a terrain of mafic and ultramafic plutonic rocks with minor pillow lava and plagiogranite. It is interpreted to be a dismembered ophiolite in thrust contact with the Gander Group. The westernmost Davidsville Group consists of a basal conglomerate, believed deposited unconformably upon the GRUB from which it was derived, and an upper unit of greywacke and slate, mostly of turbidite origin, with minor limestone and calcareous sandstone. The limestone, which lies near the base of the unit, contains Upper Llanvirn to Lower Llandeilo fossils. The Gander and Davidsville Groups display distinctly different sedimentological , structural and metamorphic histories. The Gander Group consists of quartz-rich, relatively mature sediment. It has suffered three pre-Llanvirn deformations, of which the main deformation, Dp produced a major, NE-N-facing recumbent anticline in the southern part of the study area. Middle greenschist conditions existed from D^ to D- with growth of metamorphic minerals during each dynamic and static phase. In contrast, the mineralogically immature Davidsville Group sediment contains abundant mafic and ultramafic detritus which is absent from the Gander Group. The Davidsville Group displays the effects of a single penetrative deformation with localized D_ and D_ features, all of which can be shown to postdate D_ in the Gander Group. Rotation of the flat Gander S- into a subvertical orientation near the contact with the GRUB and the Davidsville Group is believed to be a Davidsville D^ feature. Regional metamorphism in the Davidsville Group is lower greenschist with a single growth phase, MS . These sedimentological, structural and metamorphic differences between the Gander and Davidsville Groups persist even where the GRUB is absent and the two units are in contact, indicating that the tectonic histories of the Gander and Davidsville Groups are distinctly different. Structural features in the GRUB, locally the result of multiple deformations, may be the result of Gander and/or Davidsville deformations. Metamorphism is in the greenschist facies. Geochemical analyses of the pillow lava suggest that these rocks were formed in a back-arc basin. Mafic intrusives in the Gander Group appear to be the result of magraatism separate from that producing the pillow lava. The Gander Group is interpreted to be a continental rise prism deposited on the eastern margin of the Late Precambrian-Lower Paleozoic lapetus Ocean. The GRUB, oceanic crust possibly formed in a marginal basin to the west, is believed to have been thrust eastward over the Gander Group, deforming the latter, during the pre-Llanvirnian, possibly Precambrian, Ganderian Orogeny. The Middle Ordovician and younger Davidsville Group was derived from, and deposited unconformably on, this deformed terrain. Deformation of the Davidsville Group occurred during the Middle Devonian Acadian Orogeny.

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Surficial sediments east of Dunnville, Ontario representing a limited deltaic/lacustrine/aeolian system are investigated with the aim of defining and interpreting their geological history by means of exarrrrning their sedimentology and interrelationships. The Folk and \oJard grain size statistics of samples fran the area were calculated. These sample parameters were e1en plotted on maps to detennine regional patterns. The strongest pattern observed was one of distinct fining to the east, away fran the sand source. Aeolian deposits were fourrl to be better sorted than the surrcunding sediments. The grain size parameter values were also plotted on bivariate graphs in an attempt to separate the samples according to depositional environment. This exercise met with little success, as rrost of the sediments sampled in the area have similar grain size parameters. This is believed to be because the sediment sources for the different environments (delta, distal delta, aeolian dune) are intimately related, to the point that nnst dunes appear to have been sourcErl fran immediately local sediments. It is FOstulated that in such a srrall sedimentological sub-system, sediments were not involved in active transport for a length of time sufficient for the rraterial to cane to equilibritnn with its transporting medium. Thus, fe..v distinctive patterns of parameters were developed that would enable one to differentiate between various environments of neposition. The i.rnTaturity of rrany dune forms and the i.Imaturity of mineralogical composition of all deposits support the above hyt:XJthesis of limited transport time. Another hypothesis proposen is that eadh geologically or geographically distinct area or "sub-system" rray have its o,.m "signature" of grain size relationships as plotted on bivariate graphs. Thus, the emphasis, concerning graphs of this type, should not be placErl on attempting to nifferentiate between various environnents of deposition, hut raB1er on investigating the interrelationships between sanples am environments within that "sub-system". Through the course of this investigation, the existence of nelta plain distributary Channels in the thesis area is SUG0ested, and the mscovery of significantly mfferent sub-units within the TUnnville dune sediments is documented. It is inferred by reference to other authors interpretations of the glacial history of the area, that the tirre of effective aeolian acti vi ty in the Dunnville area was between 12,300 to 12,100 years R.p.

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John N. Jackson was born in Nottingham, England in 1926. He developed a passion for landforms and geography from his father, a high school math and science teacher who had studied geology. During the Second World War, he served in the British Navy. He received his BA from the University of Birmingham, and a PhD from the University of Manchester. After spending a year as a visiting professor at the University of British Columbia, he was hired in 1965 as the founding head of the Geography Department at Brock University. He taught at Brock for more than 25 years, immersing himself in the geography and history of the Niagara area. He became particularly interested in the history of the Welland Canals. He authored 20 books on various topics, including land use in Niagara, the history of St. Catharines, the Welland Canal, and railways in the Niagara Peninsula. He died in 2010, at the age of 84.

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Hebes Chasma is an 8 km deep, 126 by 314 km, isolated basin that is partially filled with interior layered deposits (ILD), massive deposits of water altered strata. By analyzing the ILD’s structure, stratigraphy and mineralogy, as well as the perimeter faults exposed in the plateau adjacent to the chasma, the evolution and depositional history of Hebes Chasma is interpreted. Three distinct ILD units were found and are informally referred to as the Lower, Upper and Late ILDs. These units have differing layer thicknesses, layer attitudes, mineralogies and erosional landforms. Based on observations of the plateau, wall morphology and slump blocks within the chasma’s interior, chasma evolution appears to be controlled by cross-faults that progressively detached sections of the wall. A scenario involving the loss of subsurface volume and ash fall events is proposed as the dominant setting throughout Hebes’ geologic history.

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The goal of most clustering algorithms is to find the optimal number of clusters (i.e. fewest number of clusters). However, analysis of molecular conformations of biological macromolecules obtained from computer simulations may benefit from a larger array of clusters. The Self-Organizing Map (SOM) clustering method has the advantage of generating large numbers of clusters, but often gives ambiguous results. In this work, SOMs have been shown to be reproducible when the same conformational dataset is independently clustered multiple times (~100), with the help of the Cramérs V-index (C_v). The ability of C_v to determine which SOMs are reproduced is generalizable across different SOM source codes. The conformational ensembles produced from MD (molecular dynamics) and REMD (replica exchange molecular dynamics) simulations of the penta peptide Met-enkephalin (MET) and the 34 amino acid protein human Parathyroid Hormone (hPTH) were used to evaluate SOM reproducibility. The training length for the SOM has a huge impact on the reproducibility. Analysis of MET conformational data definitively determined that toroidal SOMs cluster data better than bordered maps due to the fact that toroidal maps do not have an edge effect. For the source code from MATLAB, it was determined that the learning rate function should be LINEAR with an initial learning rate factor of 0.05 and the SOM should be trained by a sequential algorithm. The trained SOMs can be used as a supervised classification for another dataset. The toroidal 10×10 hexagonal SOMs produced from the MATLAB program for hPTH conformational data produced three sets of reproducible clusters (27%, 15%, and 13% of 100 independent runs) which find similar partitionings to those of smaller 6×6 SOMs. The χ^2 values produced as part of the C_v calculation were used to locate clusters with identical conformational memberships on independently trained SOMs, even those with different dimensions. The χ^2 values could relate the different SOM partitionings to each other.

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UANL

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UANL