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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Volcanic glass geochemistry of Italian proximal deposits linked to distal archives in the central Mediterranean region

Albert, Paul Graham January 2012 (has links)
Distal tephrochronology relies on the synchronous dispersal and deposition of volcanic ash or tephra (i.e. < 2mm) from explosive volcanic eruptions (Plinian/sub-Plinian). Tephrochronology correlates tephra layers to proximal source volcanic eruptions, where proximal age is well constrained, allowing tephra layers to be used as robust age markers. Tephras layers are recorded in a variety of distal environmental archives, thus tephrochronology provides an independent time framework for interpreting palaeoenvironmental proxies in marine and lacustrine cores. Tephrochronology is dependant on precise correlations of distal glass geochemistries with proximal source volcanics. Proximal volcanic deposits have been subject to detailed sampling and glass analyses revealing spatial and temporal changes III magmatic compositions during individual eruptions. Geochemical 'fingerprints' have been determined for Italian explosive proximal deposits using electron probe micro analysis (EMPA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Presented are detailed volcanic glass major, minor and trace element compositions for proximal deposits outcropping on the Aeolian Islands, Mount Etna and Ischia. These proximal glass compositions are used to test proximal-distal correlations, . linking visible and crypto-tephra layers from marine (Tyrrbenian, Ionian and Adriatic \ Seas) and lacustrine (Lago Grande di Monticchio, Italy) cores to their volcanic source. Combined major, minor and trace element charcterisation of proximal and distal glasses has valdiated the provenance and age of numerous distal tephra layers. Precise tephra correlations have allowed for the exchange of tephrochronological information over wide geogrpahical distances (up to 800 km). Correlations based solely on major element analyses can be erroneous due to repeated chemistries produced at many of the volcanic centres investigated. Trace element concentrations enable the identification of additional diagnostic features nessesary for distinguishing tephras produced from a single volcanic centre. However, in some instances volcanic systems repeatedly produce glass geochemistries that are indistinguishable at a multi-element level demonstrating the importance of good strati graphic control distally when assigning procvenance. Some tephras identified in the Tyrrhenian Sea (Marsili basin) have no currently identified proximal counterparts. This research demonstrates that proximal stratigraphies are not always fully representative of event stratigraphies due to resurgent activity and in the case of volcanic islands flank collapse and limited on-land deposits.
122

The Cenozoic evolution of the strike-slip Ecemis fault zone and its implications for the mechanism of the tectonic escape in Anatolia

Jaffrey, N. January 2001 (has links)
The mechanism by which crustal extrusion, or 'tectonic escape' functions remains poorly understood. Central Anatolia provides an example of extrusion where the kinematics of 'escape' - related strike-slip faults can be well-constrained. This study focuses on the Ecemis Fault Zone, one of the main strike-slip fault systems involved in the Cenozoic westward extrusion of Anatolia. This study concentrates on the structure, sedimentology, geomorphology and subsidence history of the EFZ, to constrain the timing and offset on this fault zone, and thereby build a more comprehensive model of extrusion of the context of the regional geology. Sedimentological data from Lutetian (Mid-Eocene) outcrops indicate that significant strike-slip occurred on the EFZ since the Mid-Eocene. Palaeocurrent and facies data establish that an inward-draining depocentre existed in the central EFZ during Late Oligocene - Early Miocene time, contemporaneously with regional crustal extension and unroofing of the nearby Nigde Core Complex. Sedimentological studies show that the present-day fault scarps of the EFZ were established during the latest Miocene - Early Pliocene, synchronous with the initiation of Anatolian extrusion. Subsidence curves indicate that the Late Oligocene - Early Miocene was a period of rapid subsidence rates in the Adana region (north of the Taurus Mountains) and that subsidence was more rapid in the EFZ area than in surrounding Cenozoic basins during this period. Rapid subsidence in the EFZ may have been associated with the formation of a pull-apart basin the location of the EFZ. Slikenline data analysis indicate that the EFZ was undergoing sinistral trans-tension by at least Mid-Miocene time, and that this changed to dominantly E-W extension during the Quaternary. Slikenline data from the Camardi area (northern EFZ) indicate that limited sinistral strike-slip has also occurred during the Quaternary, focused on a N-S striking small graben.
123

An experimental study of compaction band evolution in an anisotropic sandstone

Townend, Edward January 2008 (has links)
No description available.
124

The kinematics, rheology, structure and anisotropy of the Alpine schist derived Alpine fault zone mylonites, New Zealand

Dempsey, Edward Damien January 2010 (has links)
No description available.
125

The thinning of continental lithosphere leading to continental breakup and the initiation of seafloor spreading

Gozzard, Simon Peter January 2011 (has links)
No description available.
126

A geodynamic model for continental breakup and sea-floor spreading initiation : implications for post-breakup rifted margin hinterland uplift

Greenhalgh, Erica January 2010 (has links)
No description available.
127

The belt of Schuppen, Assam, and the pattern of an orogeny

Fraser, W. E. January 1957 (has links)
No description available.
128

The geology of the Rop Younger Granite Complex, northern Nigeria

Black, R. January 1958 (has links)
No description available.
129

Jointing and minor tectonics of the Neath disturbance and adjacent areas

Roberts, J. C. January 1961 (has links)
No description available.
130

Evolution of thrust belts in the Alps (Savoy) and the Moine thrust zone

Butler, R. W. H. January 1984 (has links)
No description available.

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