This thesis presents a method for detailed landscape presentation. The method incorporates both fieldwork-based comprehensive geomorphological description and digital data handling and thus contributes in filling the gap between traditional geomorphological mapping and modern geomorphological studies performed in Geographic Information Systems (GIS). The main part of the thesis relates to development of a new detailed geomorphological mapping system, constructed to be easy to use and yet present a large amount of geomorphological information. The legend of the mapping system has successfully been applied to various types of landscapes, mapped at various scales between 1:5,000 and 1:50,000 without any modifications needed. The information presented in the map is based on simple descriptive criteria and thus the subjectivity is kept low, which enables a broad field of usage. In parallel with the mapping system a GIS-based geomorphological database has been developed. The structure and data presentation of the new mapping system allows for easy transformation of the data to form part of this database. The selected format of the GIS database is the ESRI ArcGIS®, Personal geodatabase. In the development of the geomorphological mapping system four field areas have been mapped in central (Bonäs, Risa and Liden) and northern Sweden (Tarfala). In addition the new legend has been adapted to a field area situated in Vorarlberg, Austria (Upper Gamperdona valley). In relation to the Tarfala field area an added issue of the project has been to give insights in the effects of physical and chemical weathering on various rock types to see if this can be detected in materials and landforms. The results from this study point at that resistance towards weathering vary among rocks even though they are of same rock type.

The upper Llandovery succession across the Jupiter-Chicotte formational contact on Anticosti Island, Québec, allows us to study the sediment dynamics and stratigraphic architecture of a storm-dominated, carbonate ramp. The Anticosti paleotropical ramp was slowly subsiding and recording significant changes in sea level in a far field glacial setting during the early Telychian. Three facies associations, grouping nine facies, are recognized along the E-W outcrop belt, and from top to bottom as the: (FA-1) encrinitic carbonate facies, (FA-2) mixed siliciclastic and carbonate facies, and (FA-3) non-encrinitic carbonate facies. These mid to outer ramp sediments represent deposition mostly from episodic, high-energy storm events as evidenced by hummocky cross-stratification, large wave ripples, gutter casts, and wave-enhanced sediment-gravity flow deposits. Spatial and temporal changes in siliciclastic content imply basin margin depositional environments in the eastern sections and change in climate regime from arid to humid conditions. The Chicotte deposition marks a major faunal change with the domination of crinoids triggered by increasing siliciclastic supply, rapid sea level fluctuations and change in substrates. The recognition of one major transgressive-regressive (TR) sequence subdivided in distinct meter-scale cycles allows a high resolution E-W correlation. The development of the TR sequence and meter-scale cycles is driven by glacio-eustacy where the main sequence is 4th order (~400 Ky) with superimposed meter-scale cycles that are 5th and/or 6th order (~100 Ky). Nevertheless, erosional capping surfaces within the more proximal tempestites represent ancient rocky shorelines that developed during forced sea level falls. In order to explain this stratigraphic architecture, a carbonate open-ramp model is proposed with a concave-up profile and a narrow and steep inner ramp in equilibrium with a high-energy coastline.

High resolution sampling was performed along the &Uuml / z&uuml / ml&uuml / Formation exposed near the YeniceSihlar village of Mudurnu (Bolu). Field and thin-section analyses showed that the &Uuml / z&uuml / ml&uuml / Formation is composed of cm to m scale cycles of 4th and 5th order. The 4th order cycles are equivalencies of parasequences and have 0.4 Ma average duration. 5th order cycles are interpreted as episodic. Upper Albian (OAE1c or OAE1d) and Cenomanian/Turonian (OAE2) anoxic events are observed as black shale levels in the studied section. Position of black shale levels is interpreted using cyclostratigraphy and sequence stratigraphy. Four types of cycle are determined. A and B-type cycles are placed in transgressive and Highstand System Tract. C and D-type cycles are placed in Lowstand System Tract. Two type 3 and one type 1 sequence boundaries are recorded. The boundary between the Soguk&ccedil / am Limestone and the &Uuml / z&uuml / ml&uuml / Formation is interpreted as the first type 3 sequence boundary. The second one separates the &Uuml / z&uuml / ml&uuml / Formation and the Yenipazar Formation and is observed at the top of the section. Type 1 boundary is represented by a conglomeratic level in the middle of the succession. Provenance analysis of sandstones indicates that during the Cenomanian the source area changed from magmatic arc setting to continental setting.

Quartz and orthopyroxene in mafic rocks are commonly observed to be surrounded by fringes of granular pyroxene, and of olivine and clinopyroxene, respectively. This study reproduces the conditions of formation of these textures, and investigates their origins, kinetics and phase relations. Pieces of silica glass or crystals of orthopyroxene were dissolved into tholeiitic and slightly alkaline basalts, suspended from wire loops in an atmospheric pressure quenching furnace, and run for 10 minutes to 32 days at subliquidus temperatures between 1120° and 1190°C and oxygen fugacities close to the QFM buffer. Polished sections of charges were examined primarily by backscattered electron imagery and by microprobe analysis. The textures developed in silica dissolution experiments consist of fringes of elongate skeletal pyroxenes radially arranged around the silica. The pyroxenes first nucleate on the surface of the silica. As dissolution continues, growth continues mostly on existing crystals, rather than by the nucleation of additional crystals. Dissolution rates for silica range from 2.8*10⁻¹¹ to 4.4*10⁻¹⁰ms⁻¹, and are time-independent until growth of the pyroxene fringe hinders transport processes in the melt. This causes dissolution to slow down, until it ceases altogether after 3 to 8 days. A silica-rich layer of melt forms around the surface of charges run at higher temperatures, suggesting that convection driven by variations in surface tension may operate in the charges. The textures developed in orthopyroxene dissolution experiments consist of granular olivines, some of which nucleate on the pyroxene surface, whereas others nucleate within the pyroxene as a result of the decomposition of included phases. With time, olivine crystals become connected and form complex grain shapes. Dissolution rates for orthopyroxene range from 1.7*10⁻¹¹ to 1.2*10⁻⁹ ms⁻¹. At higher temperatures dissolution rates are constant, but at lower temperatures dissolution is time-dependent. Unlike silica dissolution, orthopyroxene dissolution does not cease as a result of continued neocryst growth hindering melt transport, indicating that the fringe remains permeable. For both systems, the neocryst compositions are strongly dependent on the chemistry of the melt formed at the interface between the dissolving crystal and the bulk melt, and the neocrysts may be metastable with respect to the bulk melt. Chemical equilibration of olivine neocrysts with time is observed for longer experiments. Textural equilibration of olivine grains occurs by the processes of liquid-phase sintering in runs longer than 12 hours. Subliquidus dissolution data are applied to textures from natural samples collected from dykes, lava flows and lava lakes, to estimate the residence time of reacted crystals; values range from 0.6 to 208 days for reacted quartz, and from 0.7 to 462 days for reacted orthopyroxenes. The rates of cooling of the magma and the size of the magma body in which the reaction occurred are also estimated.

No description available.

The Xigaze forearc basin in southern Tibet, one of the largest and best-preserved forearc basins on Earth, records upper-plate processes active prior to and following the inter-continental collision between India and Asia. However, the understanding of the timing and mechanisms of forearc development and its evolution following collision is spatially and temporally limited. Fundamental questions remain concerning how the basin formed, its paleogeography prior to collision, its subsidence history and the thermal history of the basin following the initial and ongoing continent-continent collision. Answering these questions is important to reconstructing upper plate dynamics during active subduction of oceanic and continental lithosphere. This dissertation addresses the Early Cretaceous to Pliocene history of the Xigaze forearc, using field mapping, sedimentology, sandstone modal petrography, geohistory analysis, U-Pb detrital zircon geochronology, and low-temperature thermochronology (apatite and zircon (U-Th/He)). Appendix A documents the sedimentology and stratigraphy of Lower Cretaceous to Paleocene strata to identify the relationship between the Yarlung-Tsangpo ophiolite and Xigaze forearc basin, reconstruct the sedimentary environments of the southern margin of Asia during the initial to middle stages of forearc deposition, and use the basin history to evaluate the mechanisms controlling forearc subsidence. In Appendix B, analysis of Eocene sedimentary strata, the youngest preserved in the forearc basin, constrains the timing of collision between Asia and the Tethyan Himalaya (India) to be no later than 58-54 Ma based on the similarity of the U-Pb detrital zircon age spectra and sandstone compositions between the Xigaze forearc and strata deposited atop the passive margin of the Tethyan Himalayan at that time. Apatite and zircon (U-Th)/He thermochronologic results in Appendix C constrain the maximum burial temperature of the basin following collision to ~140-200 °C, which corresponds to depths attainable by sedimentation in the forearc and a Paleogene forearc successor basin. This integrated dataset also identifies the initial stage of post-collisional exhumation during the Early Miocene (~ 20-15 Ma), followed by accelerated cooling during the Late Miocene to Early Pliocene (~ 10-4 Ma). These results suggest the presence of a paleo-Yarlung River and/or intensification of the Asian monsoon during the Early to Late Miocene. The Pliocene cooling signal is the youngest reported to date along the IYSZ and likely reflects increased river incision of the Yarlung-Tsangpo driven by accelerated orogen-parallel extension across structures which cross-cut the IYSZ. Robust interpretation of thermochronologic data requires knowledge about the geologic factors and intrinsic properties of the minerals. Appendix D of this dissertation examines intragranular zonation as a source of anomalously young zircon (U-Th)/He ages from leucogranites that intrude Greater Himalayan Sequence rocks at Ronbguk Valley, north of Mt. Everest. Depth profile laser ablation ICP-MS analysis was used to quantify the U-Th concentration profiles of a series of zoned, single, whole zircon grains and to apply a grain specific zonation-dependent age correction. Zircon grains corrected for zonation yield zircon He ages of 15-17 Ma, in agreement with AFT, ZFT and mica ⁴⁰Ar/³⁹Ar ages from the region. This study highlights the importance of characterizing intragranular zonation, especially in complex, zoned zircons that are typical of crustal melts and high-grade metamorphic rocks. Appendix E synthesis the results from Appendices A-C in the context of a global comparison with other ancient and preserved forearc basins. Results from the Xigaze forearc basin are compared to general models for forearc basin formation, subsidence trends, and preservation. The results show similarities between the Xigaze forearc basin and modern forearc basins, such as the Japan forearc off Honshu Island. The mechanisms driving tectonic subsidence are addressed, but remain an area of frontier research in continental dynamics.

Στόχος της εργασίας ήταν η ιζηματολογική και γεωχημική ανάλυση των νεογενών ιζημάτων της νήσου Κρήτης στο νότιο τμήμα, της λεκάνης της Μεσσαράς , με απώτερο σκοπό να μελετηθούν τα αποθετικά τους περιβάλλοντα, οι συνθήκες σχηματισμού τους, η γεωδυναμική εξέλιξη της περιοχής καθώς και ο εντοπισμός και αξιολόγηση πιθανών μητρικών πετρωμάτων υδρογονανθράκων. / --

Sedimentological analyses of sediment traps and 289 years (1717-2006) of varved sediments from Shadow Bay (60.01°N, 159.18°W), Lake Chauekuktuli were compared to available hydrometeorological data in order to investigate basin response to hydroclimatic variability in southwest Alaska. On a subannual timescale, the characteristics of the coarse basal unit typical of clastic varves were controlled by spring snowmelt and runoff, while the fine-grained cap was shaped by fall and winter conditions. Coarse subannual laminations within the clay cap were associated with autumn storm activity and winter warming events brought about by the interplay between regional maritime and continental air masses. Biogenic silica (BSi) profiles show two annual peaks in siliceous algal deposition; the first occurred at the end of the spring freshet, the second in the late summer. On an annual timescale, varve thickness was dependent on total annual discharge (r2=0.75, n=43, p<0.0001), while maximum annual grain size was determined to be dependent on both maximum spring discharge (r2=0.63, n=43, p<0.0001) and total annual discharge (r2=0.61, n=43, p<0.0001). On interannual timescales, relationships between climate variables (temperature, precipitation, North Pacific (NP) and Pacific Decadal Oscillation (PDO) indices) and both regional discharge and varve thickness were insignificant. When the same data sets were analyzed on multidecadal timescales, regime shifts in varve thickness and total annual discharge coherent with shifts in NP and PDO indices were identified. Periods of increased varve thickness and total annual discharge were associated with warm PDO phases and a strengthened Aleutian Low. The 289-year varve record was used to reconstruct PDO dynamics prior to 1900. Multidecadal shifts were apparent throughout the 19th century, but were absent in the 18th century. This study provides insight into the linkages between regional climate, physical and biological deposition, and can be used to improve the interpretation of seasonal and annual-scale paleoclimate reconstructions for basins similar to Shadow Bay. This study also sheds light on the nature of multidecadal climate variability in the Pacific Northwest region prior to the instrumental record. / Thesis (Master, Geography) -- Queen's University, 2008-09-23 14:13:32.943

Within the middle McMurray exposures along the Steepbank River (Steepbank River Outcrops 3 and 4), nine recognized facies can be divided into three genetically related groups: sand-dominated facies, inclined heterolithic stratification (IHS) facies and mixed heterolithic facies. Together, these facies are interpreted to represent a fluvially dominated, tidally influenced point bar that experienced strong seasonal variation in river discharge. Annual fluctuations between river-flood stage and low-flow stage are responsible for the deposition of fluvially dominated sand beds alternating with brackish, tidally influenced mud beds that cover the point-bar surface as members of the various IHS facies. The dichotomy of fluvially dominated sand deposition and brackish-water ichnology of the mud beds represents the annual migration in position of the tidal and salinity nodes caused by fluctuations in fluvial discharge. Recognition of metre-scale cycles (MSCs) of alternating sandier and muddier intervals within the IHS facies imply that decadal climate cycles, likely caused by fluctuations in ocean and/or solar dynamics, influenced point-bar deposition. These MSC packages are defined by an upward decrease in sand-bed thickness, an upward increase in mud-bed frequency, and an upward increase in bioturbation intensity, all occurring on a metre scale. MSCs are an important architectural element of these large-scale tidal-fluvial point bars because they are predictable, repeatable and continuous around the point bar. Analysis of paleocurrents relative to inclined-heterolithic-stratification bedding planes indicates that bend-flow modifications (BFMs) were effective in redistributing flow around the point bar. Furthermore, this suggests that Outcrop 3 is representative of an upstream-to-bend-apex transition within a large-scale point-bar planform. Recognition of multiple channels at Outcrop 4 was based on large-scale erosional truncation, IHS bed-orientation changes, large cumulative thicknesses of the middle McMurray, thick sand-package thicknesses, changes in relative scale of sedimentary structures, and the occurrence of large mud clasts. Similarities in depositional expression between channels suggest autogenic channel stacking (within-valley stacking), rather than the stacking of separate valleys. Finally, discordant paleocurrents within the basal sand-dominated facies are likely representative of amalgamated channel-bottom facies from several generations of channel. This suggests that only the upper intervals of basal sand-dominated facies are genetically linked to the overlying IHS facies. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2012-01-30 13:25:32.53

No description available.