The Late Precambrian cover sequence in the Blue Ridge of central Virginia includes rocks of the Moneta Formation and the overlying Lynchburg Group. The Moneta Formation comprises arnphibolites, felsites and biotite gneisses that unconformably overlie the Grenville basement. The Lynchburg Group in central Virginia is divided into three formations. Lynchburg I is made up of massive to thick bedded coarse-grained feldspathic arenites and conglomerates, which are interpreted as slope-apron deposits. Lynchburg IT contains mainly medium to fine grained feldspathic arenites and graphitic schist (black shales) with subordinate conglomeratic rocks. These are believed to be channelized submarine fan turbidites formed in an anoxic environment. Lynchburg ill consists of fine to medium grained feldspathic quartz arenites and a minor amount of conglomeratic rocks, which are considered to be channelized submarine turbidites with a more open marine environment and wider shelf. Three metamorphic facies and two deformation events are recognized in the cover sequence of the study area. The current tectonic models tend to view most of the mafic-ultramafic rocks and the host sedimentary rocks of the Lynchburg as ophiolitic melange, thus creating a suture, of Precambrian to Ordovician age. Detailed field mapping shows that the Lynchburg Group does not have the characteristics of melange and the mafic-ultramafic rocks in it do not resemble ophiolite. Rather, the cover sequence is related to the Late Precambrian Iapetan rifting event. Some tectonomagmatic discriminant diagrams have been used to support the current tectonic model and they are considered one of the most important arguments for ophiolites. These diagrams were tested by plotting samples from Jurassic rift basalts-diabases of eastern North America (ENA). The ENA samples, as well as the post Grenville mafic rocks in the Blue Ridge, tend to plot outside the within-plate field. It is clear that geochemical data alone may give a wrong tectonic classification, and that a knowledge of field relations is of paramount importance for interpretation. / Ph. D.

Siliciclastic sediments of the Proterozoic Uncompahgre Group can be subdivided into stratigraphic units of quartzite (Q) and pelite (P); these units include a basal, fining- and thinning-upward retrogradational sequence (Q1-P1) that records the transition from an alluvial to a shallow-marine setting. Overlying the basal sequence are three thickening- and coarsening-upward progradational sequences (P2-Q2, P3-Q3 and P4-Q4) that were influenced by tide-, storm- and wave-processes. The progradational units are subdivided into the following facies associations in a vertical sequence. Outer-to inner-shelf mudstones, Bouma sequence beds and storm beds of association A are succeeded by inner-shelf to shoreface cross-stratified sandstones of association B. Conglomerates and cross-bedded sandstones of upper association B represent alluvial braid-delta deposits. Tidal cross-bedded facies of the inner shelf/shoreface (association C) gradationally overlie association B. Interbedded within the tidal facies in upper association C are single pebble layers or <1 m-thick conglomerate beds and trough cross-bedded pebbly sandstones. Single pebble layers could be due to storm winnowing whereas conglomerates and pebbly sandstones may record shoaling to an alluvial/ shoreface setting. A temporally separated storm/alluvial and tidal shelf model best explains the origin and lateral distribution of facies in the progradational sequences. The presence of smaller progradational increments in the mudstone dominated units (P3) and the recurrence of facies associations in the thick quartzite/conglomerate units (Q2, Q3, Q4) suggests that external cyclic factors controlled sedimentation. A composite relative sea level curve integrating glacio-eustatic oscillations and long-term subsidence may account for the evolution of the thick progradational sequences of the Uncompahgre Group. Sedimentary rocks of the Uncompahgre Group have been subjected to polyphase deformation and greenschist facies metamorphism. Phase 1 structures (localized to the West Needle Mountains) include bedding-parallel deformation zones, F₁ folds and an S₁ cleavage. Phase 2 coaxial deformation resulted in the development of upright, macroscopic F₂ folds and an axial-planar crenulation cleavage, S₂. In addition basement-cover contacts were folded. Phase 3 conjugate shearing generated strike-parallel offset in stratigraphic units, a macroscopic F₃ fold, and an S₃ crenulation cleavage. In addition, oblique-slip, reverse faults were activated along basement-cover contacts. The Uncompahgre Group unconformably overlies and is inferred to be parautochthonous upon ca. 1750 Ma gneissic basement that was subjected to polyphase deformation (D_B) and amphibolite facies metamorphism. Basement was intruded by ca. 1690 Ma granitoids. Deformation of gneissic and plutonic basement together with cover (D_BC) postdates deposition of the Uncompahgre Group. The structural evolution of the Uncompahgre Group records the transition from a ductile, north-directed, fold-thrust belt to the formation of a basement involved “megamullion" structure which was subjected to conjugate strike-slip faulting to accommodate further shortening. D_BC deformation may be analogous to the deep foreland suprastructure of an orogenic belt that developed from ca. 1690 to 1600 Ma in the southwestern U.S.A .. / Ph. D.

Growth strata analysis and detrital-zircon geochronology are useful applications of stratigraphy to tectonic problems. Whereas both tools can contribute to kinematic analyses of supracrustal rock bodies, growth strata are also useful for analyzing the influence of tectonics on stratigraphic architecture. This study reports: 1) a conceptual model for growth strata development; 2) stratigraphic and kinematic analyses of growth strata architectures from growth structures in southeastern Utah, the Gulf of Mexico, and northeastern Spain; and 3) the detrital-zircon geochronology of the Salinian block of central coastal California. Kinematic sequence stratigraphy subdivides growth strata into kinematic sequences that are separated by kinematic sequence boundaries. Kinematic sequences can be further partitioned into kinematic domains based on the termination patterns of strata within a kinematic sequence. Salt- related fluvial growth strata from the Gulf of Mexico and southeastern Utah contain stratigraphic architectures that are unique to different kinematic domains. Offlap kinematic domains contain fluvial strata indicative of high slopes, low accommodation rates, and strong structural influence on paleocurrent direction. Onlap kinematic domains contain fluvial strata indicative of moderate slopes, high accommodation rates, and decreased structural influence on paleocurrent direction. The stratigraphic architecture of alluvial -fan thrust -belt growth strata in northeastern Spain does not display a marked correlation with kinematic domain, and is most easily interpreted using existing models for autocyclic alluvial -fan evolution. Detrital- zircon (U -Pb) geochronologic data from basement and cover rocks of Salinia suggest that Salinia originated along the southwestern margin of North America, likely in the vicinity of the Mojave Desert. The presence of Neoproterozoic and Late Archean detrital zircons in Salinian basement rocks also suggest that Salinian sediments were recycled from miogeoclinal sediments of the western margin of North America.

No description available.

Sur la Plate-forme Est Européenne (PEE), des sédiments silicoclastiques néoprotérozoïques ont livré une faune animale édiacarienne type dans le bassin de Podolya. Sa géologie montre un domaine marin littoral et indiquent que cette faune vivait dans la zone euphotique. Situé en bordure du Bouclier Ukrainien, le bassin est resté à l'abri des événements tectoniques et sa subsidence a été faible, ce qui explique l’absence de métamorphisme et de processus liés à la diagenèse d’enfouissement. Ces conditions ont permis la préservation des fossiles d’animaux et des minéraux argileux. Ainsi, quatre couches riches minéraux interstratifiés (IS) ont permis d’identifier des bentonites i.e. des produits pyroclastiques altérés. Les zircons de la bentonite la plus récente, qui coiffe les niveaux fossilifères, ont été datés (238U/206Pb) à 557-555 Ma ; le macrobiota édiacarien de Podolya est donc plus âgé. De plus, les variations de teneurs en kaolinite dans la pile sédimentaire indiquent que le continent Baltica voisin (actuelle PEE), source du détritisme, a connu une succession de climats tempéré-chaud-tempéré. En accord avec les données paléomagnétiques, Baltica a donc migré depuis les hautes vers les basses latitudes avant d’amorcer un mouvement rétrograde. Les strates fossiles pauvres en kaolinite peuvent être corrélées avec une position de Baltica en latitude élevée, près de la bordure nord de Rodinia et du continent Avalon.Nos résultats permettent de situer les fossiles édiacariens de l'Ukraine sur l'échelle biochronostratigraphique mondiale, et de mieux comprendre les relations spatio-temporelles du biote de Podolya par rapport aux autres macrofaunes situées à proximité de Baltica à cette époque. Les nouvelles données et les morphologies primitives des fossiles de Podolya – d’ordinaire uniquement comparées à celles de la Mer Blanche (Russie) pourraient expliquer la ressemblance phylogénique entre le biote édiacarien d’Ukraine et certains macrofossiles d'Avalon. / On the East European Platform (EEP), Neoproterozoic siliciclastic sediments have revealed a typical animal fauna of Ediacaran in the Podolya basin. The geological data are typical of marine tidal domain and suggest that this fauna lived under a water depth that did not exceed the euphotic zone. After this period, the basin, located on the edge of the Ukrainian Shield, has remained safe from tectonic events and its subsidence was low, which explain that these deposits are unmetamorphosed and unaffected by processes of burial diagenesis. These conditions allowed both the preservation of animal fossils and argillaceous minerals. Thus, four levels rich in IS mixed-layers could be identified as bentonites, altered pyroclastic products. Zircons of the youngest bentonite, which caps the fossiliferous levels, have been dated (238U/206Pb ratio) to 556±1 Ma, so Podolya's ediacaran macrobiota is of older age. Moreover, the variations of the kaolinite content in sedimentary pile indicates the neighboring mainland of the Baltica micro-continent (current EEP), source of the detritism, has been subjected to temperate-warm-temperate climate cycle. According to the paleomagnetic data, this shows that Baltica migrated from high to low latitudes and followed a retrograde motion. The kaolinite-poor fossil stratas can be correlated with high latitude position of Baltica, close to the northern border of Rodinia and of Avalon micro-continent. Our results make it possible to better situate the Ediacarian fossils of Ukraine in relation to the global biochronostratigraphic scale, but also to better understand the spatial and temporal relationships of Podolya’s ediacaran biota compared to other faunas located in the vicinity of Baltica at this time. The new data and primitive morphologies of Podolya's fossils – usually compared to the only fossils of White Sea (Russia) might explain why Ediacaran biota from Podolya Basin has more phylogenic resemblance to some Avalon’s macrofossils.

Bibliography: leaves 137-158 / 158 leaves, [8] leaves of plates : ill., maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1987

The rock art that is found in the region of Reindeer Lake, Saskatchewan is part of a larger category of rock art known as the Shield Rock Art Tradition. At present, there are more than 400 known and recorded rock art sites throughout the Canadian Shield region. These sites are found over an extensive geographical area and can be found from south-western Quebec across the Shield westward, up to north-western Saskatchewan. The majority of these rock art sites are comprised of imagery that has been painted on rock surfaces. The rock art sites at Reindeer Lake, or panels as they are called, depict a variety of symbols and characters that portray humans, animals, anthropomorphs, ceremonies and motifs of a spiritual nature. A variety of explanations have been proposed as to the function and meaning of rock art in general. Among the more accepted explanations are that rock art paintings were created by shamans; that they depict dreams or visions of an individual seeking medicine or participating in a vision quest/puberty rites; that they are a form of hunting magic whereby the author in capturing the animal in a painting assures capture of the animal in life; or that they serve as markers for travellers. Regardless of function and meaning, all of the rock art sites on Reindeer Lake are of immense heritage value and should be regarded as sacred locations. Very little is known about the rock art in the Reindeer Lake regions. Before any significant analyses of their meaning can be conducted, they must first be relocated and properly documented. At present there are only a very small number of publications that document or mention the Reindeer Lake rock art. This thesis surveys the rock art of Reindeer Lake, Saskatchewan. It discusses the general nature of pictographs from the Shield Rock Art Tradition and how the panels at Reindeer Lake fit into the overall scheme, and applies a systematic method to the recording and analysis of pictographs using a contextual approach. Although the primary focus is on recording the painted imagery, the specific context of each panel as well as the surrounding landscape is also considered. Recording these ancient rock art sites using a proper systematic method has ensured that this significant element of Aboriginal culture will endure not only for future research, but also for the benefit of future generations of the local Cree people.

The rock art that is found in the region of Reindeer Lake, Saskatchewan is part of a larger category of rock art known as the Shield Rock Art Tradition. At present, there are more than 400 known and recorded rock art sites throughout the Canadian Shield region. These sites are found over an extensive geographical area and can be found from south-western Quebec across the Shield westward, up to north-western Saskatchewan. The majority of these rock art sites are comprised of imagery that has been painted on rock surfaces. The rock art sites at Reindeer Lake, or panels as they are called, depict a variety of symbols and characters that portray humans, animals, anthropomorphs, ceremonies and motifs of a spiritual nature. A variety of explanations have been proposed as to the function and meaning of rock art in general. Among the more accepted explanations are that rock art paintings were created by shamans; that they depict dreams or visions of an individual seeking medicine or participating in a vision quest/puberty rites; that they are a form of hunting magic whereby the author in capturing the animal in a painting assures capture of the animal in life; or that they serve as markers for travellers. Regardless of function and meaning, all of the rock art sites on Reindeer Lake are of immense heritage value and should be regarded as sacred locations. Very little is known about the rock art in the Reindeer Lake regions. Before any significant analyses of their meaning can be conducted, they must first be relocated and properly documented. At present there are only a very small number of publications that document or mention the Reindeer Lake rock art. This thesis surveys the rock art of Reindeer Lake, Saskatchewan. It discusses the general nature of pictographs from the Shield Rock Art Tradition and how the panels at Reindeer Lake fit into the overall scheme, and applies a systematic method to the recording and analysis of pictographs using a contextual approach. Although the primary focus is on recording the painted imagery, the specific context of each panel as well as the surrounding landscape is also considered. Recording these ancient rock art sites using a proper systematic method has ensured that this significant element of Aboriginal culture will endure not only for future research, but also for the benefit of future generations of the local Cree people.

M.Sc. (Geology) / The main objective of this study was to characterize the North Break Zone of the Otavi Mountain Land, Namibia in terms of stratigraphy and petrography and to investigate its relationship with the Tsumeb ore body and other mineralized prospects in the immediate vicinity of Tsumeb. The Late Proterozoic Otavi carbonate platform sequence is famous for its base metal deposits. The North Break Zone is a stratabound zone of sporadic mineralization, brecciation and silicification occurring in the lower part of Iithozone T6 of the Hoffenberg Formation (Tsumeb Subgroup). It intersects the pipe-like Tsumeb Cu-Pb-Zn-Ag ore body at a depth of about 900m below surface. Where the North Break Zone intersects the Tsumeb ore body large massive ore associated with calcitized dolomite, dolomite breccia as well as feldspathic sandstone lenses occur. These features extend along strike and dip outside the normal dimensions of the Tsumeb ore body. The genesis of the Tsumeb ore body is poorly understood. The conventional model is that meteoric fluids circulated through the so-called North Break Zone paleo-aquifer, dissolving carbonate and giving rise to solution collapse and eventually the creation of the Tsumeb karst pipe. However, no direct evidence is available to support this model. This study was devised to critically evaluate the relationship between the North Break Zone and formation of the Tsumeb ore body. The study entailed field mapping, detailed sampling of the stratigraphic sequence and ore bodies, white light, reflected light, UV/blue light and cathodoluminescence petrography. Cathodoluminescence proved to be the most effective petrographic tool for differentiating various carbonate phases. The North Break Zone is defined as a 10 to 14m thick chert free oolitic to intraclastic dolomitic grainstone, stromatolite and mudstone unit, in which discontinuous lenses of mineralized secondary quartz are present. It is interbedded with dark grey cherty micritic dolomite of Lithozone T6 of the HOffenberg Formation. Minor calcification, Cu-Pb-Zn mineralization and manganese and iron enrichment are associated with the quartz-rich bodies. The mineralized quartz bodies are only present up to 2.5km to the west and 2.6km to the east of the Tsumeb ore body. The petrographic study indicated that 1) the epigenetic sequence of carbonate alteration, precipitation of new carbonate phases and mineralization is virtually identical in all Cu-Pb-Zn occurrences and 2) that the mineralization is closely associated with Mn-bearing brightly luminescent (CL) carbonates. Earlier Cu-Pb-Zn sulphide mineralization is associated with Mn-bearing bright red luminescent sparry dolomite (dolomite IIIB). Late stage Cu-arsenate, oxide and silicate mineralization is associated with an episode of Mn-bearing bright yellow luminescent calcite (calcite II) which also causes dolomitization of the associated dolomites. A very simple paragenetic model of mineralization is proposed. The earliest is defined by pre-mineralization calcite (calcite I) vein formation with associated dolomitization. This phase is followed by deposition of kerogen luminescent Mn-bearing dolomite IIIB - quartz and Cu-Pb-Zn sulphides representing the main mineralization event. It is followed by a late mineralization event composed of Mn-bearing calcite (calcite II) with associated Cu-arsenates, oxides and silicates. Supergene alteration is represented by the precipitation of very late stage non-luminescent Mn and Fe-poor calcite (calcite III) and quartz without any associated Cu-Pb-Zn mineralization. The sequence of mineralization is explained by the evolution of a single hydrothermal fluid, from relatively cold to hot and then back to cold, during a major period of fluid migration through the carbonate platform sequence. The North Break Zone probably never acted as a paleo-aquifer for fluids that formed the Tsumeb ore body. Rather hydrothermal fluids moved from the Tsumeb ore body into the North Break Zone. Hydrothermal fluids may have been derived from the Damara orogen to the south of Tsumeb during a period of tectonic loading and thrust deformation.

Within the area under consideration there are two great series of strata. The lower one is known as the Purcell-Belt Series and is divided into two main groups. A widespread unconformity separates the Purcell Series from the younger and overlying Windermere Series. The Lower Purcell-Belt group consists of the Aldridge-Prichard, Creston-Ravalli, Kitchener-Wallace, and Siyeh-Striped Peak. They were deposited under marine conditions from the erosion of a western Precambrian Cascadia. The Upper Purcell-Belt group consists of the Dutch Creek, Mount Nelson and their equivalents in Canada and the Missoula Group of Montana and possibly the Priest River group of Washington. This group is separated from the Lower Purcell by a period of diastrophism marked by the intrusion of Purcell sills and the extrusion of Purcell lavas. The Upper Purcell-Belt sediments were derived from the positive areas as a result of the preceding crusted disturbance. The Purcell-Belt times were closed by large scale orogeny called the "Purcell Uplift". The north-south trending belt of Purcell mountains formed a landmass which greatly affected lower Palaeozoic stratigraphy. This positive area is commonly referred to as the "Montana Island". The Precambrian portion of the Windermere Series includes the Toby-Shedroof conglomerate, Irene Deola volcanics and the Horsethief Creek-Monk formations. The clastic formations were derived from the Purcell Mountains and deposited on their western flank. Marine conditions arose during Horsethief Creek times. The Cambrian portion of the Windermere Series was deposited in a north-south trending geosynclinal trough which extended from the Metaline quadrangle to the Field-Golden area of the Rocky Mountains and probably beyond. It includes the lower quartzitic Hamill Group and the overlying limy and argillaceous Lardeau group. They were deposited as the shoreline transgressed south and east over the "Montana Island" and reduced it from one of high relief to one of low relief. Stages of emergence and resumed sedimentation are indicated, by upper formations of the Lardeau group. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate