In the Kanchenjunga area (far eastern Nepal), as well as in the whole Himalayan chain, the juxtaposition of the high-grade mid-crustal Higher Himalayan Crystallines (HHC) onto the low grade Lesser Himalayan Sequence (LHS) is structurally marked by the Main Central Thrust Zone (MCTZ). On the base of original field mapping and mesoand micro-structural data, the MCTZ has been here identified as a crustal-scale ductile to ductile-brittle shear zone roughly centred on the Inverted Metamorphic Sequence (IMS), in which different rocks are more pervasively deformed and sheared with respect to adjacent rocks. The boundaries of the MCTZ are not represented by single thrusts. The lower boundary is marked by phyllonites and mylonitic schists located at the uppermost portions of the LHS at the contact with strongly mylonitic augen gneisses of the IMS. The upper boundary of the MCTZ is roughly located at the base of Grt-Kfs-Ky-Sil anatectic gneisses in the lower portion of the HHC, being itself characterized by pervasive ductile shearing. Structural field data combined with petrologic results clearly indicate that the MCTZ is internally imbricated, resulting in the juxtaposition of rock packages characterized by different P-T evolutions and T/depth gradients, separated by “metamorphic discontinuities” which do not always correspond to evident structural breaks. This is the case of the metamorphic discontinuity identified at the upper structural levels of the IMS and juxtaposing the upper IMS rocks, locally anatectic, characterized by higher T/depth gradients on the lower IMS rocks, characterized by lower T/depth gradients. A similar metamorphic discontinuity was previously reported westward (Milke Danda transect) thus suggesting that it could be of regional importance in the tectonometmaoprhic architecture of eastern Nepal Himalaya. Citation: 2012. Structural and metamorphic features of the Main Central Thrust Zone and its contiguous domains in the eastern Nepalese Himalaya . In: (Eds.) Michele Zucali, Maria Iole Spalla, and Guido Gosso, Journal of the Virtual Explorer, volume 41, paper 2, doi: 10.3809/jvirtex.2011.00294 Journal of the Virtual Explorer, 2012 Volume 41 Paper 2 http://virtualexplorer.com.au/
This paper examines the history and disciplinary trajectory of geoarchaeology in Greece. Comprising one of the most complex and tectonically active geological settings and entailing one of the richest and most important archaeological records in Europe, Greece was among the first places where the discipline of geoarchaeology was originally applied. The peninsular and maritime character of the country, the extensive coastlines and the pronounced sea-level oscillations occurring in the Quaternary explains why geoarchaeological approaches were at first employed on famous archaeological sites situated along or near the coast. Geoarchaeology in Greece never lost its ‘coastal focus’, but it did enter a second phase during the 1980’s, when there is a shift of interest towards the study of humanenvironment interactions. This phase initiates a long-lasting debate over landscape instability and the anthropogenic versus climatic impact as major drivers of alluviation and soil erosion during the Holocene. The third stage in the history of the discipline is marked with a dual emphasis on both broad, landscape-scale perspectives and site-specific, micro-scale applications. Particularly during the last decade, geoarchaeological investigations in Greece have been characterized by pioneering studies of site formation processes, archaeological sediments and the micro-stratigraphic context. Citation: 2012. Geoarchaeology in Greece: A Review. In: (Eds.) Emmanuel Skourtsos and Gordon S. Lister, Journal of the Virtual Explorer, volume 42, paper 4, doi: 10.3809/jvirtex.2012.00304 Journal of the Virtual Explorer, 2012
In the Evia Island, our own investigations brought palaeoenvironmental informations in direct comparison with other Palaeozoic sequences of Greece. The sedimentary sequences occurring in northern Evia are overlaying the Variscan metaplutonic and metasedimentary rocks of Edipsos, Aghios and Rovies regions attributed to the Pelagonian basement (Vavassis et al. 2001). They are of Late Permian to Middle Triassic age and, in many cases, younger rocks underlay older lithologies, so that all formations are folded together or imbricated. The sedimentological characters and age of northern Evia carbonates display strong similarities with Upper Paleozoic formations from other places in Greece (i.e. Hydra, Skyros, Othrys, Attica, Salamine, Cyclades, Peloponnesus, Crete, Lesbos, Chios). There, Carboniferous and mainly Permian carbonates, crop out within the siliciclastic beds occurring at the base of the Mesozoic neritic platform of the internal Pelagonian domain.
A detailed study has been realized in the framework of a large-scale seismotectonic survey in Western Crete (Southern Greece), for the creation of a revised neotectonic map in a scale of 1:50.000, including the recognition and mapping of the main neotectonic faults and the evaluation of their seismic potential. For this reason, the faults under investigation were distinguished as active, possible active and inactive. Kinematic data and striations were used to estimate the corresponding stress field geometry. Two distinctive stress phases were recognized, operating after the Middle Miocene extensional exhumation of deep crustal rocks. The first N-S extension phase (D1) took place during Mid-Upper Miocene to Lower Pliocene, forming large normal faults, trending mainly E-W, that bound the large Neogene basins. The second phase (D2) took place during late Pliocene-Quaternary times, forming medium-to-large normal faults that trend mainly N-S, related to an E-W extension. In the E-W trending D1 faults, a younger strike-slip striation usually occurs, compatible with the later D2 kinematics. Smaller, mainly NE-SW trending faults, with significant lateral displacement, indicate a kinematic compatibility to the more recent D2 phase. Some of these faults act as transfer zones between the larger N-S trending D2 faults. Considering the fault length and the using several geological criteria for their seismic risk evaluation, we recognized 13 large major fault zones in the study area, six of which were considered as active, while three as possible active faults. Results obtained from the analysis of fault plane solution information verify both the determined active (D2 phase) stress field results, as well as the local kinematic behavior of the neotectonic faulting. Moreover, a detailed seismic hazard analysis, involving both probabilistic and deterministic approaches, shows a significant spatial variation of the various hazard measures, with the seismic hazard of the westernmost part of study area being controlled by the neighboring higher seismicity neotectonic faults
