Search results for "Processes"
showing 10 items of 3831 documents
Impact of Holocene tsunamis detected in lagoonal environments on Corfu (Ionian Islands, Greece): Geomorphological, sedimentary and microfaunal eviden…
2016
Abstract In this paper, we present for the first time geomorphological, sedimentary and microfaunal evidence of palaeotsunami impact on Corfu (Ionian Islands, Greece). The island of Corfu is located in an area of exceptional tectonic stress: towards the south, the African oceanic plate is being subducted underneath the Aegean plate, whereas towards the north, the Adriatic and European plates form a continental collision zone. Recent publications provide evidence of earthquake related co-seismic movements that potentially trigger extreme wave events as well as relative sea level fluctuations. In this context, we investigated two selected near-coast geological archives – the Chalikiopoulou La…
Slab-triggered wet upwellings produce large volumes of melt: Insights into the destruction of the North China Craton
2018
Abstract Cratons have remained stable for billions of years, despite of ongoing mantle convection and plate tectonics. The North China Craton (NCC), however, is abnormal, as it has experienced a destruction event during the Mesozoic and Cenozoic which was accompanied by extensive magmatism. Several lines of evidence suggest that the (Paleo-)Pacific plate played an important role in this event. Yet, the geodynamic link between subduction and craton destruction remains poorly understood, and it is unclear why there is no systematic spatial and temporal variation of magmatism related to subduction. Here, we perform 2-D petrological-thermomechanical simulations to investigate the influence of s…
Cretaceous tectonic evolution of the Sava-Klepa Massif, Republic of North Macedonia – Results from calcite twin based automated paleostress analysis
2019
Abstract The Sava-Klepa Massif represents an approximately 5 × 2 km sized fault-bounded block of dominantly basaltic rocks located within the Sava-Zone, an important suture zone between the Eurasian (Europe) and Gondwana (Adria) continental plates in the Balkans. Its nature and tectonic evolution is controversial: It is either interpreted as a remnant of the youngest Tethyan oceanic realm left behind after the main closure in the Late Jurassic or as the delimiter of a diffuse tectonic boundary between Adria and Europe, which had already collided in the Late Jurassic and was dominantly controlled by transtensional tectonics during Cretaceous times. In order to strengthen one or the other mod…
The sedimentary and geomorphological imprint of the AD 365 tsunami on the coasts of southwestern Crete (Greece): Examples from Sougia and Palaiochora
2018
Abstract The southwestern coast of Crete, one of the most seismically active regions in Europe, experienced co-seismic crust uplift by 9 m during the Ms = 8.3 mega-earthquake that struck the eastern Mediterranean world on 21 July AD 365. An associated tsunami event caused thousands of fatalities and destroyed many coastal settlements and infrastructure between the Levante in the east and the Adriatic Sea in the northwest. So far, coastal sedimentary archives in southwestern Crete including distinct palaeotsunami fingerprints are rarely investigated. Therefore, a multi-proxy study including sedimentological, geochemical, geochronological, and microfaunal methods was conducted in order to det…
Late Carboniferous (Kasimovian) closure of the South Tianshan Ocean: No Triassic subduction
2019
Abstract The proposed Triassic age of oceanic subduction and high-pressure/low-temperature (HP-LT) metamorphism in the South Tianshan orogen (STS) of the southwestern Central Asian Orogenic Belt needs to be re-examined on the basis of field relationship and precise age dating. Our biostratigraphic study in the Atbashi Range of southern Kyrgyzstan indicates that sedimentary strata unconformably overlie the HP-LT metamorphic rocks within the Turkestan suture zone and have a late Kasimovian (ca. 305 Ma) age. This constrains the minimum age of eclogite metamorphism in the HP-LT metamorphic complex. A Late Pennsylvanian to early Permian (Asselian) hinterland basin overlaps the margins of the Mid…
Age and isotopic evidence for the origin of the Archæan granitoid intrusives of the Johannesburg Dome, South Africa
1999
Abstract Results of RbSr, PbPb and SmNd whole rock, Rbr biotite and PbPb zircon evaporation analyses are presented for certain granitoid rocks from the Johannesburg Dome. These data indicate that the granodiorite, granite and leucosome from migmatite were emplaced ∼ 3090 Ma ago, were genetically related and were derived primarily from a source between ∼ 3300 and ∼ 3500 Ma old. A portion of the granodiorite and granite might have been derived from a source between ∼ 4000 and ∼ 4300 Ma old. The tonalite was emplaced ∼ 3170 Ma ago and was derived from a source between 3.3 and 3.5 Ga old. RbSr biotite-whole rock ages, ranging between about ∼ 2614 and ∼ 2080 Ma, probably reflect complete r…
Age and evolution of a late Archean to Paleoproterozoic upper to lower crustal section in the Wutaishan/Hengshan/Fuping terrain of northern China
2005
Abstract The Taihangshan–Wutaishan area forms part of the central North China Craton and consists of three main components: the Hengshan and Fuping complexes, containing predominantly ductilely deformed late Archean to Paleoproterozoic high-grade granitoid orthogneisses, intruded by mafic dykes of gabbroic composition, and the low-grade late Archean Wutai greenstone belt, developed between the high-grade terrains and consisting of bimodal volcanic rocks and metasediments, associated with coeval granitoids. Zircon dating shows that both the Hengshan and Fuping complexes were intruded by major granitoid bodies between 2.52 and 2.48 Ga, with rare occurrences of 2.7 Ga gneisses. Wutai granitoid…
Relationships between diffuse CO 2 emissions and volcanic activity on the island of Vulcano (Aeolian Islands, Italy) during the period 1984-1994
2002
Measurements of CO2 flux from the ground were periodically carried out on the island of Vulcano (Aeolian Islands, Italy) between 1984 and 1994. Three high-flux areas were identified at the foot of the volcanic cone (La Fossa), either inside or very close to the main village. Effect of the choice of the sampling grid was evaluated. A different sampling grid resulted in similar distribution patterns, but with different CO2 fluxes. Therefore, the absolute estimate of the total flux from the investigated area includes a large degree of uncertainty, but repeated measurements with permanent sampling sites are accurate and can detect small changes. No correlation of the flux with atmospheric param…
Structural control on the presence and character of calas: Observations from Balearic Islands limestones rock coast macroforms
2013
Calas are characteristic embayed rocky coastline landforms related to steep-sided drowned valleys that were deeply incised during low sea-level stages into carbonate plateaus. This paper studies the factors that control the presence and character of calas in three different islands of the Balearic Archipelago (Mallorca, Menorca and Formentera) by means of Digital Elevation Model (DEM) reconstructions, embayment and catchment morphometric analysis and through the compilation of fault and joint orientations. All islands exhibit emerged carbonate platforms (Upper Miocene in age) characterised by horizontal or very gently-dipping bedding. Two distinct patterns observed at all study sites are th…