Η παρούσα διπλωματική εργασία ασχολείται με την τεκτονική ανάλυση, τη μελέτη δηλαδή της παραμόρφωσης σε όλες τις κλίμακες παρατήρησης, των μεταμορφωμένων σχηματισμών υψηλών πιέσεων που απαρτίζουν τον βόρειο-ανατολικό τμήμα της νήσου Άνδρου. Βασικός στόχος αποτέλεσε η περιγραφή των γεωλογικής δομής του τμήματος αυτού, μέσω, τόσο της χαρτογράφησης των λιθολογιών, όσο και της περιγραφής των βασικών δομών παραμόρφωσης. / The present thesis deals with the structural analysis, the study, in other words, of deformation, in all scales of observation,of the HP metamorphosed formations that occure in the north-eastern part of Andros island. Fundamental objective of this study was the geological description of this specific part, via, not only mapping of the lithologies, but also the description of basic deformation structures.

Η παρούσα πτυχιακή εργασία πραγματεύεται την χαρτογράφηση της ευρύτερης περιοχής της Χερρονήσου της νήσου Σίφνου και την περιγραφή της δομής του τεκτονικού καλύμματος των κυανοσχιστολίθων. / This project deals with the mapping of wider region of Cherronisos of island Siphnos and the description of structure of Blueschist unit.

Στην παρούσα εργασία γίνεται χαρτογράφηση και τεκτονική ανάλυση του τεκτονικού ράκους του Γερόλεκα όπου παρατίθενται πετρώματα της Ζώνης Παρνασσού και της Ζώνης Βοιωτίας. / On this bachelor thesis we present the results of geological mapping and structural analysis that was elaborated in the area of Gerolekas which is occupied by rocks of Parnassos Zone.

Η εργασία αυτή έγινε με σκοπό την εφαρμογή μορφοτεκτονικών κριτηρίων για τον ποσοτικό και ποιοτικό καθορισμό της τεκτονικής ενεργότητας των δύο μεγάλων προπόδων οροσειράς (mountain range front) που αναπτύσσονται στις δυτικές παρυφές του Αργολικού Πεδίου, ΒΔ της πόλης του Άργους, και η σύγκριση των τιμών των γεωμορφολογικών δεικτών που μετρήθηκαν με την βοήθεια ψηφιακών μοντέλων εδάφους διαφορετικής ανάλυσης (resolution) για την εξαγωγή συμπερασμάτων σχετικά με την ακρίβεια της κάθε μεθόδου. Αφορμή υπήρξε η διαρκώς αυξανόμενη ενασχόληση φοιτητών (προπτυχιακών και μεταπτυχιακών) με ψηφιοποίηση τοπογραφικών χαρτών για δημιουργία Ψηφιακών Μοντέλων Εδάφους (DTM) – μια διαδικασία επίπονη και εξαιρετικά χρονοβόρα – παρότι δεδομένα διατίθενται εύκολα μέσω διαδικτύου (NASA) για DTM για όλο τον κόσμο με σχετικά καλή ανάλυση. Οι δύο πρόποδες είναι συνεχόμενοι αλλά παρουσιάζουν διαφορετική διεύθυνση με τον πρώτο να έχει διεύθυνση ΒΒΔ-ΝΝΑ και μήκος περίπου 6,5 km και τον δεύτερο ΔΒΔ-ΑΝΑ ενώ έχει μήκος περίπου 12,5 km. Για την ανάλυση της ενεργότητας των πρόπoδων οροσειράς εφαρμόστηκαν οι κατάλληλοι γεωμορφολογικοί δείκτες, όπως ο δείκτης της κατά βάθος και κατά πλάτος διάβρωσης χειμάρρων ή λόγος πλάτους προς ύψους κοιλάδας (Ratio of valley-floor width to valley height index, Vf) και ο δείκτης ευθυγράμμισης του πρόποδα (Mountain front sinuosity index, Smf) ενώ παράλληλα εξετάστηκαν και άλλοι γεωμορφολογικοί δείκτες όπως ο δείκτης Μήκους – κλίσης ρέμματος (Stream-length gradient index, SL) και ο δείκτης Υψομετρικής καμπύλης-Υψομετρικού ολοκληρώματος (Hypsometric Curve / Hypsometric Integral). Για την μέτρηση των τιμών των δεικτών χρησιμοποιήθηκαν δύο ψηφιακά μοντέλα εδάφους διαφορετικής ανάλυσης (resolution) που αναπτύχθηκαν με διαφορετικές μεθοδολογίες, ένα λεπτομερές από ψηφιοποίηση τοπογραφικών χαρτών κλίμακας 1:5000 της ΓΥΣ και ένα πιο προσεγγιστικό χαμηλότερης ανάλυσης από δορυφορικά δεδομένα SRTM, με την βοήθεια λογισμικών GIS. Τα αποτελέσματά συγκρίθηκαν με την βοήθεια διαγραμμάτων. Όσον αφορά το ζήτημα της ενεργότητας της προπόδων οροσειράς από τα αποτελέσματα των μετρήσεων προκύπτει ότι αυτοί είναι ενεργοί καθώς παρουσιάζουν χαμηλές τιμές του δείκτη Vf και Smf. Οι τιμές τους (μετρημένες από το λεπτομερές Ψ.Μ.Ε.) κυμαίνονται από 0,0531 μέχρι 0,7668 (Vf) και 1,3645 (Smf) για τον πρώτο πρόποδα και από 0,02 μέχρι 9,3 (Vf) και 1,3526 (Smf) για τον δεύτερο πρόποδα. Επίσης με την βοήθεια του δείκτη SL εντοπίστηκαν δύο σημεία που σε συνδυασμό με την τοπογραφία υποδεικνύουν πιθανά ενεργά ρήγματα που δεν έχουν χαρτογραφηθεί. Η χρησιμοποίηση του δείκτη του υψομετρικού ολοκληρώματος κατατάσσει την λεκάνη του χειμάρρου Ξηριά, που βρίσκεται πίσω από τον πρώτο πρόποδα, στο ‘στάδιο ωριμότητας’, κάτι που φαινομενικά έρχεται σε αντίθεση με τους υπόλοιπους δείκτες αλλά μάλλον οφείλεται στην μορφολογική διαμόρφωση της λεκάνης πίσω από τον πρόποδα που σχετίζεται περισσότερο από τεκτονικές και όχι από διαβρωτικές διεργασίες. Όσον αφορά την σύγκριση των αποτελεσμάτων που προκύπτουν από τα δύο διαφορετικά ψηφιακά μοντέλα εδάφους οι μετρήσεις τιμών του δείκτη SL και του Υψομετρικού Ολοκληρώματος μπορούν να γίνουν εξίσου καλά και από τα δύο. Για τον δείκτη Vf οι μετρήσεις που γίνονται με την βοήθεια του πιο προσεγγιστικού μοντέλου είναι γενικά μεγαλύτερες ενώ δεν μπορεί να γίνουν μετρήσεις για ρέμματα 1ης ή 2ης τάξης κατά Strahler. Οι διαφορές στις τιμές του δείκτη Vf που παρατηρούνται μεταξύ των δύο μοντέλων εκμηδενίζονται όταν η μέτρηση του πλάτους της κοίτης μπορεί να προκύψει με αντικειμενικό τρόπο (π.χ. μέτρηση από ορθοφωτοχάρτες). Για τον δείκτη Smf προκύπτει ότι όσο μικρότερο είναι το μήκος του πρόποδα τόσο μικρότερη είναι η απόκλιση στις μετρήσεις του δείκτη Smf από το αδρομερέστερο μοντέλο καθώς είναι πιο περιορισμένη η απόκλιση της παραμέτρου Lmf λόγω ‘απλοποιήσεων’ των γραμμών. / The aim of this MSc thesis is the application of morphotectonic criteria for the qualitative and quantitative determination of the tectonic activity on two mountain range fronts segments, which are formed in the western part of Argolis plain, in the eastern Peloponnese. We also tried to measure and compare values of the geomorphological indices obtained from DTM’s of different resolution, in order to extract conclusions for the accuracy of the two different models. The two mountain front segments are almost continuous and they display different orientation in strike: the first has a NNW-SSE strike and a length of 6.5 km and the second one has a WNW-ESE strike and a length of 12.5 km. In order to examine the activity of the two range fronts we applied the suitable geomorphic indices, such as the ratio of valley-floor width to valley height index (Vf), the mountain front sinuosity index (Smf), as well as other indices such as the stream-length gradient index (SL) and the hypsometric curve-hypsometric integral index. For the calculation of these indices we used two DTM’s of different resolution, which were constructed from different approached methodologies: a more detailed DTM from digitization of topographic maps of the Hellenic Military Geographical Service, in 1:5000 scale, and a less detailed DTM from SRTM-data downloaded from NASA, all modeled with standard GIS software. The results of the two models were compared with various diagrams. Regarding the activity of the range front segments, our data show that they are both active since they display low values of Vf and Smf indexes. Their values (measured from the finer DTM) vary from 0,05 to 0,77 (Vf) and 1,3645 (Smf) for the first segment and from 0,02 to 9,3 (Vf) and 1,3526 (Smf) for the second segment. Additionally, using the SL-index we observed two zones, which when correlated with the modern topography seem to indicate two unmapped and possibly active fault zones. The Xerias basin, which is formed behind the 1st range fault segment, appears to be in the “maturity stage” using the hypsometric integral index, a fact that contradicts with the other index results. This is may be due more to tectonic than erosional processes. Finally, from the comparison of the different DTM we suggest that calculation of SL and hypsometric integral index can be made with similar accuracy. For the Vf , the SRTM data display higher values, while calculation of 1st and 2nd order gullies (sensu Strahler) cannot be directly measured. Differences in the Vf values from the two DTM models can be eliminated significantly when we calculate the width of the valley from ortho-photomaps. Regarding the Smf index, it seems that we obtain less accurate results, as the length of the range front increases, due to the over-simplification of the shape of the elevation contours compared to the real topographic data.

Identifying tectonically active faults and quantifying rates of movement is a key challenge in the Earth Sciences, in addition to this the interactions between active faulting and the landscape, specifically involving the fluvial network, is a relatively new area of study. Previous work has highlighted the value of understanding how the fluvial network responds to active tectonics, showing that a comprehensive understanding of the dynamic relationship between fluvial geomorphology and active tectonics is an important next step in geological research. This study presents new information about the poorly constrained Quaternary tectonic history of the Gediz Graben, Turkey, providing the first quantification of rates of movement of the key fault array that presently controlling graben topography. The fluvial network has been investigated and the data has been used in order to add resolution to the tectonic history for the fault array, allowing for the quantification of post-linkage throw rates. The study then investigates the key controls on the behaviour of the fluvial network that cross the active topography building fault array in the Gediz Graben. This study shows that there has been a linkage event occurring between 0.6 – 1 Ma, involving the three segments of the graben bounding fault array. The pre- and post-linkage throw rates are then extrapolated using data derived from the fluvial network, showing a faulting enhancement factor of 3 at the centre of the fault array, with the throw rate at the centre of the array predicted to have increased from a pre-linkage rate of 0.6 ± 0.1 mm/yr to a rate of 2 ± 0.2 mm/yr. This research provides evidence that the fluvial network can be used in conjunction with other types of evidence to provide a greater resolution tectonic history. Using both digital data and field studies this research presents an examination of the factors that influence the behaviour of bedrock rivers undergoing perturbation due to tectonics. Factors such as drainage area, tectonic throw rates and lithology have been investigated and the complicated interactions of these variables with the fluvial system have been quantified. This study shows that the bedrock rivers are a significant source of information about tectonics, but further work is needed to resolve quantitatively how various factors influence how rivers adjust to tectonic perturbation, in a variety of tectonic situations, in order to enable river to be used as a primary tool for deriving information about tectonics.

At present there is no theory which describes fully observations of weakness and anomalous slip behaviour on many faults. Recent field studies upon such faults indicate that reactions which generate frictionally weak phyllosilicate minerals, including talc, may be significant. A series of experiments was carried out on a deionised water fluid medium triaxial deformation apparatus to investigate the effect of the syntectonic generation of talc upon fault strength and slip characteristics, where talc is produced by the reaction: lizardite + quartz → talc + H2O. Experiments to investigate reaction kinetics were performed on lizardite and Brazilian quartz powder samples. Talc is generated by this reaction within 72 hours under hydrothermal conditions between 350°C and 500°C and effective pressures of 5 to 50 MPa. Microstructural study shows porous talc overgrowths surrounding lizardite and quartz grains suggesting an armouring effect with progressive reaction. Constant displacement rate tests and subsequent stress relaxation tests were performed upon cylindrical samples of lizardite and Hodge quartzite saw-cut at 35° juxtaposed across the shear zone. Some samples were assembled with pure talc or lizardite gouge between the forcing blocks. Tests were carried out under hydrothermal conditions: 450 °C, 50 to 150 MPa effective pressure and 4.64 x 10-4 mm s-1 shear surface displacement rate. Some samples were deformed at once to assess frictional properties of the starting materials. Other samples were held at hydrothermal conditions for 72 hours prior to deformation, to allow the blocks and gouge to react to talc. Continued reaction to talc was expected during stress relaxation. All samples displayed stable sliding behaviour, with little strain hardening. Friction coefficients averaged from varied effective pressure tests were largely in line with previous studies. A strength contrast is shown between talc gouge (average µ=0.11) and talc grown as a thin veneer between lizardite and quartz forcing blocks, (average µ=0.22) which is likely to be due to asperity effects including the variable contiguity of the talc veneer. Lizardite gouge gives a value of µ=0.45, but when partially reacted to talc gives µ=0.23. This is significantly weaker despite representing perhaps less than 15% talc. Stress relaxation data initially shows similar behaviour for all sample geometries, with a temperature-controlled dominant deformation mechanism. Lizardite gouge with ongoing reaction to talc shows enhanced shear stress reduction at low strain rates (stress exponent falls from n=12 to n=5.5). This is ascribed to the effect of reaction via production of a weaker phase, leading to reduction of frictional strength and grain size, compaction and pressure solution effects. Pure lizardite gouge also shows a reduction in stress exponent to n=7.5, attributed to dissolution-precipitation of lizardite. Microstructural study shows that talc grows as a thin veneer along the quartzite forcing block indicative of localisation of deformation with foliated talc and recrystallised lizardite present within Riedel shear structures in the lizardite gouge. The talc veneers are deformed and may be subject to mechanical smearing, enhancing their contiguity. Results of this study highlight the significance of both mechanical smearing and incongruent pressure solution creep as potential mechanisms for weakening and aseismic creep-of particular interest is the rate of strength reduction versus the rate of reaction and whether this can be extrapolated fully to creep rates on the San Andreas Fault. Similar weak phases of hydrothermal origin have been identified by other studies and the contiguity of these phases is thought crucial to their impact upon weakness, and may be enhanced greatly by the joint effects of syntectonic reaction and mechanical smearing.

Sub-surface reservoirs are normally characterised by limited information from widely spaced wells (1D sections) and relative low-resolution seismic data (2D or 3D sections) making any derived geological model highly interpretive. The ability of outcrop exposures to study the sedimentary architecture (e.g. stacking patterns, lateral continuation, facies proportions and distribution) at a wide range of scales (km to mm) in continuous 3D accessible sections make them ideal analogues to help bridge the gap in resolution between seismic and well data in reservoir studies.In this study the sedimentary architecture of the outcrop exposures the Late Triassic Wolfville Formation are evaluated using traditional sedimentological (e.g. correlation panels, log sections) and digital (e.g. DGPS, LiDAR, DEM) field techniques to help better understand these often complex fluvial depositional systems for analogue reservoir studies. The sediments of the Wolfville Formation are superbly exposed in both cliff sections and on extensive wave-cut platforms along the shore of the Minas Basin (Nova Scotia, Canada). The succession lies unconformably on Pre-Triassic rocks and forms the earliest syn-rift unit in the Fundy basin. The unit comprises coarse- and fine-grained fluvial sandstones, aeolian dune deposits, and alluvial fan sediments. The laterally extensive and three-dimensional nature of the outcrop exposures offer a valuable insight in the sedimentary architecture of the fluvial system. A detailed sedimentological analysis of the succession allowed the determination of the large-scale sedimentary architecture of this gravelly to sandy bedload fluvial system. In order to characterise the architectural evolution in more detail digital outcrop studies were employed in three carefully selected study areas. The study areas are located along the southern Minas Basin shore within the gravelly and younger sandy-dominated part of the succession.The digital outcrop studies carried out in the study areas collected spatial data using differential GPS and LiDAR (Light Detection and Ranging) equipment. The integration of traditional collected geological and spatial data forms digital outcrop models (DOMs), which allow accurate mapping and evaluation of the geological properties geometry and distribution using novel spatial analysis techniques (e.g. classified point-cloud and perpendicular projection plane method). The results offer a better understanding on the heterogeneity of the depositional system, accurate geostatistical information on the characteristics of sedimentary bodies and genetic units (geometry, distribution and proportion) and provides a high-resolution stratigraphic-structural framework for geocellular outcrop models. In the geocellular outcrop models of the study areas the three-dimensional facies distribution are simulated using various modelling approaches, such as sequential indicator simulations, object modelling and multiple point statistics. The available control of the outcrop models allowed the various facies modelling approaches to be examined. The results are evaluated and discussed using qualitative comparison studies. In addition, these outcrop models provided detailed information on the three-dimensional fluvial architecture.

Der Bericht liefert einen Überblick über die geologischen Gegebenheiten entlang der geplanten Schienenneubaustrecke zwischen Dresden und Prag, die als Teilabschnitt des Middle-East-Korridors zum Trans-Europäischen Netz gehört. Er beinhaltet ein geologisches 3D-Modell entlang der Trasse, die Ergebnisse geophysikalischer Untersuchungen im Bereich der Struktur Börnersdorf und Ergebnisse geotechnischer Untersuchungen an ausgewählten Punkten. Die Veröffentlichung richtet sich an Ingenieur- und Planungsbüros, Forschungs- und Lehreinrichtungen sowie Behörden.

In this thesis I address the problem of determining fracture properties of subsurface rocks from geophysical surface seismic and vertical seismic profile (VSP) data. In the first part of this thesis I perform multi-attribute analysis, including frequency content, amplitude, travel time and angle of rotation studies on field VSP data from two different carbonate fields, both containing time-lapse surveys. I compare the findings to independent data available in the region and find that the interpreted fracture orientations from the attribute analyses correlate with independent fracture studies in the area, the principal axis of major faults, or the maximum horizontal stress of the area studied. Although I show the existence of these correlations, due to the limited knowledge of the rock properties, these correlations are only qualitative. A more robust inversion of fracture properties requires more knowledge of the physical properties of the medium and forward modelling of the seismic response. A rock physics theory would be required to model the elastic response of the fractured rock; hence a more quantitative fracture characterisation is necessary. In the second part of this thesis I address this need by developing and testing a method for fracture density inversion. Linearised approximations are commonly used in azimuthal amplitude versus offset (AVO) analysis. However, these approximations perform poorly at large angles of incidence where the effect of fractures is more significant. The method proposed here uses a model based approach that does not use these approximations but calculates the exact azimuthal AVO response based on prior knowledge of the elastic constants of the medium, assumed to be known, and a range of fracture densities. A rock physics theory is used for modelling the elastic constants of the fractured rock. I then create a linearized relationship for a specific model that separates the effect due to fracture density from the modelled AVOZ responses. This separation is key to the method, as it provides both a new set of orthogonal basis functions that can be used to express the AVOZ response of field data, and a set of coefficients that are related to fracture density. In general, the inversion is based on these coefficients. The coefficient or coefficients which present the highest correlation with fracture density must be determined on a case by case basis, as they will vary depending on the contrast between the elastic constants across the boundary of interest. I develop and test the method on synthetic surface seismic data and then apply it to seismic data acquired from a laboratory-scale physical geological model. Due to the prior knowledge of the rock properties and structure of the physical geological model, I am able to corroborate that the inverted fracture density from the seismic data matches that of the physical model within the error. I compare the inversion for two different levels of uncertainty in the velocities and densities of the modelled reflection coefficients and show that the inversion results are more precise and accurate when there is less uncertainty in the rock properties of the modelled reflection coefficients. In both the synthetic and physical geological model studies I find that the inversion is optimal for a certain range of offsets/angles of incidence. This means that the optimal range for inversion must be found on a case by case basis, as it depends on the behaviour of the data. Finally, as the inversion relies on the input modelled azimuthal AVO curves, a careful choice of the input rock properties is essential for the inversion process. The inverted fracture density values will only be valid if the rock properties of the field data fall within the range of the modelled ones. This is a limitation of the method, as adequate knowledge of the rock properties is not always available.

The cause and distribution of spatial variations in the mechanical properties of the continental lithosphere are fundamental questions for modern geology. In this study variations in long-term lithospheric rigidity have been investigated. These investigations used profile- and grid-based flexural models of the lithosphere’s response to geologically imposed topographic, or buried, loads. These models were constrained by topographic and gravity data allowing recovery of best fitting rigidity values. In Oman a Cretaceous ophiolite acts as a significant load on the continental crust. Flexural models along profiles orthogonal to the ophiolite strike show that the observed gravity data can be best modelled by an elastic beam with standard thickness (T_e) of 30 km. Along strike there is shown to be significant variation in the foreland shape and the observed gravity signal. This, it is proposed, relates to the complex tectonic processes which occurred as the ophiolite was obducted. The Himalayan foreland has been the focus of controversy over the recovered long-term rigidity of the continents, with recovered T_e values ranging from 40 to over 90 km. Both profile- and grid-based techniques show that T_e is high (>70 km) in the foreland region. Across the India-Eurasia collisional system as a whole T_e values are variable. Beneath the Tibetan plateau recovered values are generally low (<10 km), while the plateau margins are marked by regions of higher rigidity. Recovered T_e values across the Arabia-Eurasia collisional system range from over 60 km in the foreland region to close to zero beneath the high Zagros mountains. In the eastern part of the foreland, flexural models match the gravity data; however, they disagree with sediment thickness data for the material infilling the foreland. This discrepancy is interpreted in terms of de-coupling of the flexural lithosphere from the shallower crustal levels, caused by the presence of significant salt deposits in this region. Application of grid-based techniques to South America, North America and Europe recover a broad range of Te values from ∼0 to over 90 km. The low T_e values are explained in active orogenic belts in terms of current processes acting to weaken the lithosphere, and in the continental interiors as the relics of past orogenic events. High T_e values in the continental interiors correlate with ancient cratonic cores which have undergone little deformation since their formation in the Archean. This study shows that T_e variations have a critical influence on the development of large compressional orogenic belts. In the Himalayan and Andean orogens there is a correlation between the over-thrusting of the orogenic belt and high T_e foreland regions. Where lower T_e regions are seen, less over thrusting is apparent, and in the case of the India-Eurasia collisional system out-flow of lower crustal material may be occurring.