Στόχος της εργασίας ήταν η μελέτη της τεκτονικής και της ιζηματογένεσης της περιοχής, με απώτερο σκοπό να μελετηθεί η δράση των ενεργών ρηγμάτων που υπάρχουν στην παράκτια ζώνη του Κορινθιακού κόλπου στα δυτικά της πόλης της Κορίνθου καθώς και η διαφοροποίηση που αυτά προκαλούν στην απόθεση των ιζημάτων της περιοχής. / --

No description available.

Cassini spacecraft images of Enceladus' surface have revealed diverse terrains---some heavily cratered, others almost devoid of craters, and even some with ridges and fractures. We have documented crater morphologies in regions for which high-resolution data are available (140 to 360 W and 90 S to 60 N). The south polar region shows a dearth of craters, in sharp contrast to the heavily cratered northern latitudes. Tectonized regions such as Sarandib and Diyar Planitiae also have low crater densities. Viscously relaxed craters are found in the apparently young regions of the anti-Saturnian and trailing hemispheres, as well as in the older, upper northern latitudes. By modeling the viscoelastic relaxation of craters on Enceladus using TEKTON, a finite-element code, we predict large geographical variation in heat flow and a complicated thermal history on Enceladus. Our results are consistent with the planitiae being older examples of the South Polar Terrain, supporting a satellite-reorientation hypothesis.

A thorough understanding of Tibetan Plateau growth requires knowledge of the geological evolution of the Tibetan terranes as they were accreted to the Eurasian margin during the Phanerozoic. This dissertation research addresses the tectonic evolution of the southernmost of these, the Lhasa terrane of Tibet from the Late Jurassic to Eocene. The data and insights presented herein are the result of extensive geologic fieldwork in the northern and central Lhasa terrane of Tibet. In this work I present new geologic mapping and thermochronologic data that reveals a terrane scale passive roof thrust belt in the northern Lhasa terrane that accommodates significant upper crustal shortening without exhuming basement rocks. Through the development of a geospatially referenced database of igneous crystallization ages, I show that Cretaceous magmatism on the Lhasa terrane was not static, but exhibited significant temporal-spatial migrations. I interpret these movements as the result of variations in Neo-Tethyan slab dip and suggest that these variations are a major factor in shaping the Cretaceous tectonics of the Lhasa terrane. Finally, I present the Cretaceous-Eocene tectonic evolution of the Lhasa terrane that shows that the Lhasa terrane was above sea level and likely had attained significant elevation prior to the accretion of India to Eurasia and that the development of the high elevation Plateau developed outward from a central core, rather than from south to north as is commonly thought. These insights refute the widely held view that the Tibetan Plateau is the result of the Cenozoic Indo-Asian collision.

Syn-convergent low-angle normal-sense detachments (LANDs) are found in many orogens around the world. However, those tectonic processes which result in their formation are little known. The South Tibetan detachment system (STDS) is the best-studied example worldwide of a syn-convergent LAND, and formed in the Miocene due to the continental collision of India and Asia. In Bhutan, eastern Himalaya, the STDS is duplicated. Here I investigate the tectonic history of the inner STDS and particularly the outer STDS in Bhutan, to determine whether the duplicated STDS can be explained by or used to constrain models of Himalayan orogenesis. A range of geochronometric, thermochronologic, petrologic, structural, thermobarometric, thermometric, and isotopic tools are used to constrain: the onset and cessation of motion on the outer STDS; the cessation of motion on the inner STDS; the peak metamorphic conditions in the hanging wall and footwall of the outer STDS; the pressure-temperature-time paths of tectonites in the hanging wall and footwall of the outer STDS; the structural history of the hanging wall rocks of the outer STDS, and; the paleogeographic affinity of the hanging wall rocks of the outer STDS. The results of these studies are compared to thermo-mechanical models of Himalayan- type continental collision. Similarities in model predictions of the type and timing of structures, peak metamorphic conditions of hanging wall and footwall tectonites, pressure-temperature-time paths, and other regional tectonic observations lead to two main conclusions. 1. The STDS is a system of three main types of LANDs: those that formed during channel flow of low-viscosity mid-crustal rocks, those that formed by extrusion of cooled channel rocks to the surface, and those that formed by destabilization of the upper crust above a dome of mid-crustal channel rocks. 2. The STDS was duplicated by underthrusting of a crustal ramp into the Himalayan orogen since early Miocene. The underthrusting led to extrusion of a dome of weak mid-crustal above a previously-extruded channel. The crustal ramp may be local to the eastern Himalaya due to higher convergence and/or erosion rates, or due to local underthrusting of relatively strong crust behind weaker crust.

No description available.

Understanding the development of the Himalaya is critical to elucidating continental collisional processes. The Greater Himalayan sequence (GHS), the exhumed mid-crust of the Himalayan orogen, records the tectonometamorphic evolution of the Himalaya from its deep hinterland to its foreland. The GHS in central Nepal and adjacent Tibet is deformed pervasively; quartz c-axis orientation fabrics from across the GHS indicate that it was deformed at high temperatures (~550-650˚C). The asymmetries of these quartz c-axis fabrics confirm field observations that define a reversal in shear sense from top-south shear near the bottom and middle of the GHS to top-north shear near the top of the package proximal to the South Tibetan detachment system (STDS). Estimates of mean kinematic vorticity from across the GHS indicate a pure shear contribution between 33% and 67%. U-Pb geochronologic data from the upper GHS exposed in the Changgo culmination in south Tibet indicate that melt crystallization and metamorphism related to crustal thickening occurred at ca. 35 Ma and was succeeded by a second metamorphic episode and syn-kinematic voluminous anatexis at ca. 22 Ma. The upper GHS was thinned vertically by 50% and extended horizontally during and immediately after the second metamorphic event, in a manner typical of the deep hinterland regions of orogens. In central Nepal, the ductile lateral extrusion of the upper GHS between the Main Central thrust (MCT) below and STDS above ceased by ~19 Ma. The cessation of lateral extrusion followed the collapse of the orogenic wedge and a reduction in the gravitational potential necessary to drive the propagation of deformation southwards towards the foreland. To restore the geometry of the wedge, deformation stepped out-of-sequence into southern Tibet, with the exhumation of the Changgo culmination and the North Himalayan antiform, before migrating incrementally back toward the foreland. Subsequently, the MCT migrated downward structurally adding material to the lower GHS as thrust slices, characteristic of foreland-style deformation. Thus, the transition between the upper and lower GHS in central Nepal records the transition from hinterland-style deformation to foreland-style deformation. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2009-04-13 11:48:45.702

No description available.

The Waipara – Kowai groundwater allocation zones (referred to as zones) are located 50 kilometers north of Christchurch. Land use in the Waipara zone has evolved from dry land farming towards horticultural and irrigated pastoral farming, and as such the demand for groundwater resources has increased significantly. Recent 14C age dating has shown that deep wells tap >1000 years old water, raising concerns about possible resource mining. The Kowai groundwater allocation zone has had minimal regional hydrogeological investigations and previously little is known about the groundwater resources here. The Waipara – Kowai groundwater allocation zones are located near obliquely convergent plate margin and the Porters Pass Fault System. Recent (early Quaternary) deformation has been noted by workers along margins and associated with emerging structures within basins. These emerging faults and folds within the basin are acting as hydrological barriers, hindering the passage of groundwater within the basin. A geomorphic map was constructed for this study based on existing soils maps, limited field soil surveys and morphometric analysis. Nine geomorphic surfaces are described, with inferred ages of modern to >73 ka. The geomorphic investigation revealed that the Kowai groundwater allocation zone surface is stepped, with increasing thickness of loess up gradient on the downlands. Near the coast there is intercalated terrestrial and marine sediments, to the west overlying the Kowai Formation are small alluvial fans. In the Waipara Basin the Waipara fan dominates the central portion of the basin, with smaller fluvial and alluvial fans building out from the margins. Groundwater recharge was investigated using chemical, isotopic, water level observations and a simple water balance. It was found that in the Kowai zone the major recharge sources were the rainfall, losses from the rivers and streams. The southern region of the Waipara zone is recharged by rainfall with small contributions from the Kowai River (North Branch). In the South region of the Waipara Basin groundwater recharge is derived from rainfall and losses from streams. The groundwater systems are conceptualized as being topographically driven, with slope – basin floors interactions being an important source of groundwater recharge.

An improved method has been developed for carrying out 2-plate reconstructions, in which fracture zone locations are fitted to synthetic flowlines and magnetic anomaly picks are rotated and fitted to great circles representing other, not necessarily conjugate, anomaly isochrons. This enables the determination of finite rotation poles for regions with sparse data coverage, or where much of one or both plates has been subducted. Misfits and partial derivatives are calculated for each type of data, and combined in a single iterative inversion, allowing the direct calculation of confidence intervals. This method is then extended to a 3-plate reconstruction, taking closure into consideration. The South American - African - Antarctic plate system is then studied. Fracture zone locations are identified from a gravity map constructed from GEOSAT altimeter data, and magnetic anomalies are identified from ship profiles. Two-plate reconstructions are carried out for each plate pair, giving good fits to the observed data, and then all three datasets are combined in a 3-plate reconstruction. Comparison of the results reveals a discontinuity in spreading in the Weddell Sea, believed to be related to pseudo-asymmetric spreading caused by ridge re-organisation in the Paleocene and early Eocene. A revised 3-plate inversion, taking this discontinuity into account, produces an internally consistent set of poles, indicating a closed 3-plate system since anomaly 34 (83Ma), with no evidence for a Malvinas Plate extending into the Weddell Sea in the Late Cretaceous. Disruption to the system from anomaly 32 (71Ma) until anomaly 24 (52Ma), appears to be related to the collision of Africa with Eurasia. A study of the past motion, configuration and stability of the Bouvet Triple junction suggests that for the majority of the past 50Ma it has been in a RFF configuration, in theory considerably less stable than RRR, the other possible configuration.