Search

The aim of this study, which covers the Tigris River and its tributaries (Kizilsu River) established in Cizre and its surroundings, in the province of Sirnak in the Southeastern Anatolia Region, it is to examine the valley evolution process, geomorphologicalfeatures, response to tectonic. This works the evolution process of the Kizilsu River, which settled in the region by crossing Kasrik George the aim of to the factors affecting the morphological structure of the region. This area is important in terms of covering a part of Tigris River valley, one of Turkey’s most important rivers and tectonism-fluvial system relationship. In this research around Kasrik George; the formation process of the George (antesedant split valley), the step structure sandrock terrace formed by effect of tectonism on morphology are discussed and tectonism-fluvial system relationship is studied. The area where the Cizre district center was established and its immediate surroundings draw attention with the terraces of the Tigris River. In this study area, the Tigris River formed S1 (100-125 m), S2 (50-70 m), S3 (10-30 m) and S4 (3-5 m) terraces. The upper (S1) level of these landforms is covered with basalt sand formed a structural lava plateau. In addition, different drainage networks formed by the Tigris River and its tributaries are also seen in the study area.

The Udokan volcanic plateau differs from other volcanic regions of the Late Cenozoic volcanic province of East Asia in the high alkalinity of volcanic rocks, their potassium specialization, and rock composition, varying from melaleucytitis and melanephelinites to alkaline trachytes. The presence of alkaline-salic rocks in volcanic associations makes it unique to the province. The reasons that determined the unique magmatism of the Udokan plateau are considered. The data of geochemical and isotopic studies have shown that the moderately enriched magma of the mantle plume served as a melt source in the region. The initial melts were formed under conditions of garnet stability at low degrees of melting. This contributed to their enrichment in alkalis and other incompatible elements that is especially characteristic of ultramafic rocks. It is established that fractionation processes controlled the distribution of the trace elements in the rocks of volcanic associations. Deep differentiation of the magmas to alkaline trachytes occurred in the peripheral magma chambers. Here, magmas interacted with intracrustal waters, which led to a change in their oxygen isotopic composition. It is shown that contamination did not play a decisive role in the formation of lava plateau rocks.

The Tharsis region of Mars is a vast volcanic plateau which hosts the immense Tharsis Montes shield volcanoes. The Tharsis region is suggested by multiple lines of morphologic and modeling evidence to have been a site of coincident volcanic and glacial activity throughout the majority of the geologic history of Mars. The prolonged and overlapping histories of volcanism and glaciation within the Tharsis region raise the likelihood of widespread surficial glaciovolcanism, a possibility which is supported by the recognition of glaciovolcanic landforms in the region by past investigations. Given this likelihood, we perform an exploratory study to assess the potential role that surficial glaciovolcanism may have played in the geologic and hydrologic history of the Tharsis region. We first review the history and characteristics of volcanism and glaciation in the Tharsis region, as well as previously documented evidence for past glaciovolcanic activity, in order to outline relevant conditions and parameters. The outlined volcanic and glacial conditions are then used in conjunction with results and predictions from past modeling of surficial glaciovolcanic processes to assess the potential role of glaciovolcanism in the formation of the Tharsis region's major tectonic and hydrologic features. We conclude that surficial glaciovolcanism may plausibly have contributed to the formation of many of the tectonic and fluvial features in the Tharsis region, offering advantages over prior formation models, particularly for the large basin/chaos-sourced outflow channels concentrated in the area. The formation of a range of investigated features in the Tharsis region by surficial glaciovolcanism does not require ambient warm and wet climate conditions therefore suggesting potential consistency between the observed features and a predominantly cold and icy climate. Consequently, this analysis represents an incremental contribution to better understanding the climatic and hydrologic evolution of Mars. However, analyses performed in this work indicate that the glaciovolcanic origin models we considered are unable to viably account for the complete range of explored features, indicating that future work is required to better resolve the processes involved in their formation.

The paper reports the isotope-geochronological and petrological-geochemical studies of the Pliocene moderately-acid volcanism of the Akhalkalaki Plateau in the central part of the Lesser Caucasus (Javakheti highland, Georgia). K-Ar dating showed that young dacitic lavas and pyroclastic rocks were formed in the mid-Pliocene (3.28 ± 0.10 Ma) in relation with the explosive–effusive eruptions of small composite volcanic cones and formation of minor extrusive domes confined mainly to the eastern margin of the region. Isotope-geochronological data in the combination with results of structural drilling indicate that the considered short-term pulse of the volcanic activity occurred during a short gap between two phases of the Pliocene–Early Pleistocene mafic magmatism widespread within the Akhalkalaki plateau. The studied Pliocene dacites were erupted at the post-collisional stage of the evolution of the Lesser Caucasus, but bear petrological-geochemical affinity of adakitic series. They are characterized by the steady presence of amphibole phenocrysts, the elevated contents of Sr, Ba, LILE and the lowered contents of Y, Nb, Ta, and HREE, and have depleted Sr isotopic composition (87Sr/86Sr < 0.7045). Analysis of petrogenetic models earlier proposed to explain the generation of adakite-like magmas in the modern collision zones showed that the origin of the Pliocene dacitic lavas of the Akhlkalaki plateau is best described by the crystallization differentiation of water-saturated calc-alkaline basaltic melts with removal of common mafic rock-forming minerals (first of all, amphibole and pyroxene) and accessory phases (apatite, titanite, Ti-magnetite) as cumulus minerals. Crustal assimilation of evolved magmas only insignificantly contributed to the petrogenesis of the dacites.

Quantifying water contents of the lithospheric mantle is key for our understanding of global geodynamics, mantle composition and related physical properties. Most of the mantle lithologies contain little water, but some heterogeneities like pyroxenites, likely contain more water, and by their mineralogical assemblage melt at lower temperatures. The quantification of their water content brings new information about water distribution in the mantle. This study focuses on two continental lithospheric domains: the Massif Central (France) and the Adamawa Volcanic Plateau (Cameroon). Garnet pyroxenites in Adamawa Volcanic Plateau are more hydrated ([H2O]Cpx = 386-685 ppm; [H2O]Opx = 124-155 ppm; [H2O]Garnet < 0.5 ppm) than those of French Massif Central ([H2O]Cpx = 112-465 ppm; [H2O]Opx = 61-104 ppm; [H2O]Garnet < 0.5 ppm). These water concentrations are representative of lithospheric water (no water loss during xenolith ascent), however water content of French Massif Central pyroxenites have been modified by metasomatism. Pyroxenites have been dehydrated by a hot carbonatitic fluid, whereas rocks of Adamawa Volcanic Plateau were likely not affected by metasomatic events. In both regions, the metasomatic episodes modified the LREE contents (e.g., Ce). Consequently H2O/Ce ratio, which could be a good source tracer, might not be the most appropriate tool to identify pyroxenites implication in magmas genesis.

Georgia is in the middle of the area (70, 000 km2) almost 25 in the Europe. The formation of the country's territory counts for one billion years. All forms of relief are presented in Georgia, which is known worldwide. There are hundreds of natural monuments on the territory of Georgia that make a special impression on the visitors. It is also important that such monuments of nature are concentrated on a small area that increases their tourism and recreational purpose. With the diversity of nature, Georgia can be presented in the world geographical parks (geoparks) networks, and will further increase its tourist attraction. Georgia has not been presented in the world geographical parks (geoparks) networks, what is an interesting as Caucasus Office of Nature Protection World Fund, as state and local tourist organizations. The relevant nomination can be submitted by Elizbarashvili (2018): 1. Javakheti—volcanoes and Vardzia canyon is located in southern Georgia (Akhalkalaki administrative district). It is made of lavish streams flowing from the slopes of the Mordian direction. There are several volcanic cones on this ridge that create effective peaks. The western boundary of the Plateau passes through the Vardzia canyon (the administrative district of Aspinza), with an average depth of 500 m, and a length of 7 km. It is in the middle of the medieval city of Vardzia (13-storey cave building) and monastery complex, which is nominated for a UNESCO cultural heritage monument. Some volcanic lakes are presented under geopark, which present Ramsar Convention site and are in composition of protected territories of Javakheti. 2. Imereti—The dinosaur footprint and the Imereti Cave Complex (including the Kutaisi city and Tskaltubo administrative districts) in central Georgia—There are over 200 unique footprints of dinosaurs, which are found in 1933 on the mercury limestone. The footprint is located at 500 m above the sea level, with subtropical humid conditions and the western exposition winds (slopes from the Black Sea). Nearby, there are several karst caves, geological, paleontological, zoological, and botanical monuments. The Tskaltubo Cave is one of the most remarkable places in Europe. 3. Khevi—Glacier (Kazbegi), Gudauri volcanic plateau and Dariali Gorge—The glacier is located on the central Caucasus in northern Georgia (Stepantsminda administrative district). Its height is 5033 m. The local population call it “Khevi bride". The glacier is a “dormant” volcano that lasted 6,000 years ago. Here the lavish deer runs in three—south, east, and north-east. One of the mythological and one historical (Gergeti Trinity) monument is the monument on the edge of the glacier. Mythology is connected to Amiran (the analog of Prometheus) attached to the Caucasus. According to the tradition, God Amiran right here climbed the cliff, and “on top of the snow-ice gear and the glacier of the glacier". At the foot of the glacier, Dariali canyonic gorge is represented in the rocks formed in the form of volcanoes developed over 300–400 million years ago, central Caucasus. Its length is 11 km, and the relative height is more than a thousand meters. There is also a volcanic plate of Gudauri, whose vertical slopes are formed by lava cooling (suspension).

International audience; This paper presents a multi-proxy geoarchaeological analysis of the complex pedo-sedimentary archives of a small pond situated within the protohistoric site of Corent, in central France. A robust chrono-stratigraphic framework was developed integrating all chronological data from previous studies. Micromorphological, geochemical and sedimentological analyses were performed on a radiocarbon-dated core. Results are discussed alongside palynological data from previous work on the same core, in order to reconstruct human-environmental interactions on the Corent volcanic plateau since the Neolithic. After intense soil erosion recorded during the Early and Middle Neolithic, the Late Neolithic is characterized by vegetation recovery and soil stability in the basin contemporaneous with site abandonment, perhaps due to pronounced soil degradation in the plateau. During the Early Bronze Age, agropastoral land use contributed to major environmental changes in the pond’s basin, including soil profile sealing and gleyfication. Environmental impact patterns detected in the pedo-sedimentary record indicate settlement intensification during the Middle Bronze Age. After the substantial impacts of an intense anthropogenic disturbance in the Early Iron Age, the Lac du Puy becomes a vertic depression recurrently flooded while a late Iron Age Gallic oppidum develops on the plateau, and is finally backfilled at the end of the Iron Age. The detailed multi-proxy picture from this intra-urban wetland helps nuance our understanding of the environmental impacts of prehistoric societies in Western Europe. Indeed, our results highlight the importance of keeping a long term perspective when dealing with past human-environment interactions.

Large-scale pyroclastic density currents (PDCs) produce inhomogeneity of distributions, thicknesses, stratigraphic structures, and temperatures, thereby causing poor understanding of PDC emplacement processes. Millennium Eruption (ME) of Tianchi volcano in 946 A.D. produced masses of PDCs, covering an area of more than 1570 km2 around the caldera in the Chinese territory. To understand PDC emplacement processes, we examine the proximal to distal variations in the PDC facies during the ME by analyzing the topography, stratigraphy, granulometry, and petrography. The topography of Tianchi volcano has different slopes, including the cone (> 6°), lava shield (2–5°) and lava plateau (< 1°), which affected the PDC emplacement during the ME. The shape of the PDC deposits radiates outward from the caldera, and the periphery has two pyroclastic aprons. The proximal strata (< 10 km) are less than 4 m thick and consist of eutaxitic and lava-like structures in the gullies of the cone. The medial strata (10–20 km) are 10–60 m thick, with columnar joints, pumice-rich layers, and lithic-rich layers in the valleys of the shield. The distal strata (> 20 km) are less than 10 m thick, with coarse-tail layers, ground surge layers, climbing layers, and carbonized woods in the plateau. From the proximal to the distal strata, the emplacement temperature of the PDCs decreased from 740 to 280°C. The medial layers indicate a gravitational differentiation effect and weakened transportation, which led to the formation of thick beds. The distal PDCs demonstrate fluidization characteristics and a density lower than that of the proximal and medial strata, which exhibit clear stratification. Grain size data (< 64 mm) show that the median diameters decreases with increasing distance from the caldera. Rhyolitic and trachytic pumice were found and are assumed to be associated with the composition of the magma chamber. Magmatic mixing structures were confirmed through microscope observations. The volume of the PDCs in the Chinese territory is approximately 7 km3. Our results assist in unraveling some PDCs emplacement processes, marked by a high level of topography confinement, about 50 km runout distance, 280–750°C emplacement temperatures, and more than 7 km3 volume, which provide insights of the PDCs destruction during the ME.

Lechmine n’Ait El Haj (LNH) is a monogenetic plioquaternary maar, lying in the volcanic province of the MiddleAtlas. It is a 110-m-deep crater located in the Liassic limestones. The tephra deposits surrounding the crater are mainly made up of depositional units (surges and projectas) interpreted as deposits of phreatomagmatic origin. They are topped by a small unit of massive breccia tuff reflecting magmatic deposits. The maar is a result of the interaction between the ascending magma and karstic water, in an intraplate volcanism context. Water, causing this eruption, is drained by an open system of fractures in the limestone. The explosion started by phreatomagmatic dynamism, producing a big stack of pyroclastic deposits and pyroclastic falls. During the eruption, the crater grows progressively from the eruptive center to the Northwest. The upper part of the phreatomagmatic deposits is characterized by a typical mud crack structure. A transition to a strombolian dynamism occurred throughout the end of volcanic activity. Meanwhile, a lava flow, coming from the volcanic plateau, discharged in the crater’s center. With the eruption resumption, the lava is strongly fragmented; therefore, a small cone is created especially in the northern flank of the maar. Towards the end of the volcanic activity, a supply of karstic water causes another transition of the eruptive style from strombolian to phreatomagmatic dynamism. A significant karst collapse in the southern flank of the LNH maar has occurred, leading to its current morphology.

The Erzurum-Kars Volcanic Plateau (EKVP) was formed by volcanic eruptions during the Messinian-Zanclean (~5.5 Ma) period, related to a continental collision event between Eurasia and Arabia, initiated ~15 Ma ago. The EKVP unconformably overlies a series of older sedimentary formations spanning in age from Cretaceous to Miocene. It starts with a ~400 m thick pyroclastic-rich layer at its bottom, named the Akkoz basal tuff, consisting of rhyolitic and dacitic ignimbrites, pyroclastic fall and surge deposits, which are intercalated with andesitic and dacitic lavas. Upper layers of the plateau are dominated by andesitic and basaltic andesitic lavas (~100 m).In the northwest of the study area, an eroded stratovolcano, named Hamamlı volcano, which is possibly coeval with the plateau volcanism is present. It covers ~280 km2 area and consists of a thick sequence of rhyolitic lavas, tuffs, ignimbrites, perlites and obsidians. The best preserved volcanic edifice in the study area is the Greater Aladağ Stratovolcano with a footprint of ~230 km2. It is composed of intermediate lavas with andesitic, dacitic, trachy-andesitic compositions, erupted ~3.55 Ma in Piacenzian. A small volcanic cone, named in this study as the Lesser Aladağ volcano, sits on the northern flank of the Greater Aladağ. Lesser Aladağ has an elliptical shape and is composed of basaltic-andesitic and basaltic trachy-andesitic lavas. Three semi-circular shaped rhyolitic domes called the Odalar rhyolite sit on the southern and eastern slopes of the Greater Aladağ. In the N and NE, the Aladağ volcanic sequence is unconformably overlain by a younger (~2.7 Ma) sequence of olivine basalts and basaltic andesites, which is known as the Kars volcanic plateau.All volcanic products in the study area are calc-alkaline in character with a clear subduction signature. Results from our petrological modelling studies indicate that the magmas that fed the Aladağ volcanic system were evolved in a chamber, which was periodically replenished by fresh and primitive basaltic magma. Our assimilation model results based on the equations of DePaolo (1981) and Aitcheson and Forrest (1994) show that fractional crystallization was more important than crustal assimilation process in evolved lavas of the Aladağ system. Interestingly, EC-AFC model results indicate that some of the youngest basalts from the Kars volcanic plateau contain higher degrees of crustal assimilation relative to more evolved lavas.Crystal chemistry of amphiboles by EMP from the amphibole-bearing lavas of the Akkoz basal tuff layer indicates that they had experienced crystallization pressures between 5.63 and 6.45 kbar and temperatures between 949 and 1026 °C during their magma chamber evolution. On the other hand, pyroxene thermo-barometry of the Aladağ units has given crystallization pressures between 0.8 and 4.8 kbar, and temperatures from 1025 to 1078 °C, implying polybaric fractionation. Calculated crystallization pressures and temperatures from the younger lavas of the Kars volcanic plateau are ~8.8 kbar and ~1179 °C respectively. Our partial melting models indicate that the primitive basaltic magmas might have been derived from a metasomatised spinel peridotite source with varying melting degrees from 0.7% to 2%.

Curie point depths in southwestern Yemen were determined from radially averaged power spectra of the reduced to the pole aeromagnetic data by the modified centroid method. The results show that shallow CPD zones occurred in the western and southeastern parts of the area associated mainly with Tertiary and Quaternary volcanic regions, respectively. The distribution of hot springs and hot groundwater wells through the area is correlated well with the mapped shallow zones and thermal gradient regions around them. On the other hand, the deepest CPD zone is attributed to a hot mantle upwelling underplating the crust beneath the volcanic plateau and crystalline basement margins in the middle part of the area. This spot forming the most probable source of magma for the Quaternary volcanic activity in the area. The observed geothermal activity at Al Lisi–Isbil, Damt, and Al Qafr fields is ascribed to the heat derived from shallow magmatic bodies, with temperature less than Curie temperature of magnetite, and also to the heat transferred from the underlain hot mantle spot through a net of deep faults affected this region.

New data on the geology, age, and composition of the Late Cenozoic volcanic rocks of the Vitim Depression, a satellite of the Vitim Lava Plateau (VLP), have been obtained. Two-stage volcanic activity has been revealed. In the Middle Miocene (14–13 Ma), a basalt and trachybasalt (hawaiite) lava covers were formed. In the Pleistocene (1.6–0.7 Ma), basanite erupted from scoria cones. Both stages of volcanism were coeval to similar pulses of volcanism within the VLP. However, unlike the latter, there were no Pliocene and Late Miocene eruptions within the Vitim Depression. Additionally, the Vitim Depression basalts have depleted geochemical characteristics comparative to those of the VLP. These features of the Vitim Depression volcanics imply their autonomous formation, whereas the synchroneity of the initial and final stages of volcanism in the depression and in the VLP reflects the existence of a common regulating mechanism of igneous activity.

Peculiarities of the forest vegetation dynamics and the main factors and mechanisms of environmental filtering were studied on loose deposits of the Tolbachinskii Dol Volcanic Plateau (Kamchatka) by means of plant life-form analysis. It was found that, in the earlier stages of plant succession, polycarpic herbs, acrocarpous mosses, and fruticulose lichens dominated. Forest communities of 35 years old differed from the old-growth ones by the proportions of plant life-forms and the total coverage. Environmental filtering is manifested by the most successful development of plants having special morphological adaptations of belowground systems to loose unstable substrata.

The Paleocene volcanic rocks in the Nuussuaq Basin on Disko and Nuussuaq comprise the Vaigat Formation (c. 62–61 Ma) and the Maligât Formation (c. 60 Ma). The Vaigat Formation in this area is 0–1600 m thick and is dominated by olivine-rich picrites. The formation was deposited during three volcanic episodes and is divided into 10 formally defined members and about 20 informal units. The first episode gave rise to the Anaanaa Member. The second episode gave rise to the Naujánguit Member, which is intercalated with the minor, crustally contaminated Nuusap Qaqqarsua, Nuuk Killeq, Asuk, Tunoqqu and Kûgánguaq members and the uncontaminated Qordlortorssuaq Member. The third episode gave rise to the Ordlingassoq Member and the minor alkaline Manîtdlat Member. Contemporaneous sediments deposited during the first two episodes are the marine Eqalulik Formation, and during the third episode the nonmarine Atanikerluk Formation. During the second episode, the polarity of the geomagnetic field changed from normal (Chron C27n) via a transition zone to reversed (C26r). The deposits of the first volcanic episode are situated on western Nuussuaq. During the second and third episodes, the volcanism gradually spread eastwards and southwards so that the Vaigat Formation now forms a domed structure, thickest in the north, thinning out on northern Disko and reaching eastwards to the high gneiss country on central Nuussuaq. The earliest eruptions took place on the sea floor and quickly built up a subaerial lava plateau. All three episodes gave rise to complicated facies changes between subaqueous and subaerial eruption products caused by the eastmoving volcanism, subsidence, volcanic aggradation and blockage of the sea connection against the elevated eastern gneiss country. Eruption sites are widespread for all three volcanic episodes. Within certain time periods, a number of contemporaneous high-level magma reservoirs developed within sediments of the Nuussuaq Group, and the crustally contaminated members formed in these reservoirs by reaction between Mg-rich magmas and sediments. The uncontaminated rocks in the Vaigat Formation are picrites with 12–31 wt% MgO and subordinate basalts with 7–12 wt% MgO. The crustally contaminated rocks range from silicic picrites with 12–16 wt% MgO (Nuusap Qaqqarsua Member) to native-iron-bearing magnesian andesites with 6–10 wt% MgO and up to 62 wt% SiO2 (Asuk Member). The Asuk Member includes unique, strongly reduced rock types with native iron, graphite and sulfide. The contaminated units have individually distinct compositions, indicating individually different contamination events. The alkaline Manîtdlat Member contains an enriched lithospheric component. Present-day seeps of migrated oil are widespread in the oldest part of the volcanic succession on western Nuussuaq. Some of the contaminated magmas in the Asuk and Kûgánguaq members have fractionated sulfides with Cu and Ni and have been explored for nickel and platinum-group elements.

The Junggar Basin is a large superimposed basin with multistage evolution. The Carboniferous volcanic rock in the middle-lower part of the basin has been an important target of oil and gas exploration. Therefore, it is crucial to establish a set of efficient methods and techniques to find out the distribution of the Carboniferous volcanic rock and the tectonic factors related to the reservoir forming of the volcanic rock. Our research reveals that the density and magnetism of the Carboniferous volcanic rock are obviously higher than those of the Mesozoic and Cenozoic sedimentary rocks. With a series of frequency domain filters and boundary enhancement techniques, we determine the residual gravitational and magnetic anomalies caused by the Carboniferous volcanic rock. Combined with borehole and seismic data from the studied areas, the horizontal and vertical distributions of the Carboniferous volcanic rock are defined, and the lithologies of different types of volcanic rocks are predicted. Furthermore, the gravitational and magnetic anomalies are used to estimate the basement faults and topography. The regional deep faults and their secondary faults of the basement are outlined, and the model of basement relief is constructed. Finally, the effects of the fracture structure and the basement topography in the process of volcanic activity and hydrocarbon accumulation are fully discussed. These results provide fundamental information for optimal selection of the favorable area of volcanic reservoir.

Although the last rhyolite eruption occurred around 70 ka ago, the silicic Yellowstone volcanic field is still considered active due to high hydrothermal and seismic activity and possible recent magma intrusions. Geodetic measurements document complex deformation patterns in crustal strain and seismic activity likewise reveal spatial and temporal variations in the stress field. We use earthquake data recorded between 1988 and 2010 to investigate these variations and their possible causes in more detail. Earthquake relocations and a set of 369 well-constrained, double-couple, focal mechanism solutions were computed. Events were grouped according to location and time to investigate trends in faulting. The majority of the events have normal-faulting solutions, subordinate strike-slip kinematics, and very rarely, reverse motions. The dominant direction of extension throughout the 0.64 Ma Yellowstone caldera is nearly ENE, consistent with the perpendicular direction of alignments of volcanic vents within the caldera, but our study also reveals spatial and temporal variations. Stress-field solutions for different areas and time periods were calculated from earthquake focal mechanism inversion. A well-resolved rotation of σ 3 was found, from NNE-SSW near the Hebgen Lake fault zone, to ENE-WSW near Norris Junction. In particular, the σ 3 direction changed throughout the years around Norris Geyser Basin, from being ENE-WSW, as calculated in the study by Waite and Smith (2004) , to NNE-SSW, while the other σ 3 directions are mostly unchanged over time. The presence of “chocolate tablet” structures, with two sets of nearly perpendicular normal faults, was identified in many stages of the deformation history both in the Norris Geyser Basin area and inside the caldera.

Direct observations of vertical movements of the earth's surface are now possible with space-based GPS networks, and have applications to resources, hazards and tectonics. Here we present data on vertical movements of the Earth's surface in New Zealand, computed from the processing of GPS data collected between 2000 and 2015 by 189 permanent GPS stations. We map the geographical variation in vertical rates and show how these variations are explicable within a tectonic framework of subduction, volcanic activity and slow slip earthquakes. Subsidence of >3 mm/yr is observed along southeastern North Island and is interpreted to be due to the locked segment of the Hikurangi subduction zone. Uplift of 1–3 mm/yr further north along the margin of the eastern North Island is interpreted as being due to the plate interface being unlocked and underplating of sediment on the subduction thrust. The Volcanic Plateau of the central North Island is being uplifted at about 1 mm/yr, which can be explained by basaltic melts being injected in the active mantle-wedge at a rate of ∼6 mm/yr. Within the Central Volcanic Region there is a 250 km2 area that subsided between 2005 and 2012 at a rate of up to 14 mm/yr. Time series from the stations located within and near the zone of subsidence show a strong link between subsidence, adjacent uplift and local earthquake swarms.

The continental collision between Arabia and Eurasia created large strike-slip faults in Turkey as well as mountains in the Caucasus and the volcanic plateau between them. In this study, we use regional waveforms of a new seismic array deployed between 2008 and 2012 to constrain the focal mechanisms and depths of small to moderate sized earthquakes occurring in the western part of the Central Caucasus and northeast Turkey. The distribution of aftershocks and the twelve focal mechanisms involved in the sequence of the 2009 earthquake in Racha are clearly a reactivation of a deeper segment of the 1991 M7 Racha rupture zone. The deeper segment is not well connected to the shallower decollement separating the basement and sedimentary basin. The earthquakes we determined in northeastern Turkey and southern Georgia are related to the strike-slip fault system. We further combined all of the reliably determined focal mechanisms over the last 30 years to investigate the current stress status of the crust in three areas: Racha in the western Greater Caucasus, Javakheti near the Lesser Caucasus and in Northeast Turkey. Our results show that the directions of maximum compressional stress consistently fall within − 2 to 14°N throughout the entire study region. This appears to be controlled by the continental collision. Nonetheless, the minimum compression switches from vertical (in the Greater Caucasus) to the east-west direction (in northeastern Turkey), due to the westward extrusion of the Anatolia block, which is driven partly by the Hellenic subduction. The transition of the stress field is close to the Javakheti volcanic plateau in the Lesser Caucasus, where the relative magnitude between the principal stresses appears to be strongly variable.

The Pernambuco marginal basin is located on the eastern continental margin of northeastern Brazil, covers an area of 20,800 km 2 , and represents one of the most prominent frontiers for deep water oil and gas exploration off the Brazilian coast. The onshore region of this basin was highly affected by extrusive and intrusive magmatism during the Upper Albian, and the relation of that event with the volcanic structures observed in the offshore sector has not been thoroughly characterized to date. This study aims to characterize the major extrusive and intrusive volcanic structures of the offshore portion of this basin, which is dominated by the Pernambuco Plateau, and its stratigraphic relations. A set of 143 2D multichannel seismic sections that cover the Pernambuco Plateau region are used to interpret the major tectono-stratigraphic sequences and describe the distribution of volcanoes, sills, vent complexes and related volcaniclastic sequences. The interpretations are supported by aeromagnetic and gravimetric geophysical surveys. Volcanoes are classified into two groups that differ in terms of their morphology: shield-like structures and cone-shaped volcanic structures. Sill intrusions are mainly identified beneath the volcanic structures and are characterized by high-amplitude reflectors with short extensions and abrupt terminations. Volcaniclastic sequences are found adjacent to the volcanoes and are characterized by high-amplitude, disrupted reflections with local chaotic configurations. Vent complexes are classified on the basis of their morphologies as either eye-shaped or crater-shaped. The volcanic features identified within the available seismic dataset are concentrated in two main areas: in the centre of the plateau and near its northeastern border. These two regions are host basement outer highs and are surrounded by hyper-extended continental crust, which forms the plateau itself. The extrusive and intrusive features described in the offshore region were formed during the post rift Cretaceous and Cenozoic intervals and point to the continuation of magmatic events after the rifting process. The findings presented in this report provide a better understanding of the magmatism on the northeastern passive margin of Brazil and can also be useful for future modelling of the Pernambuco Basin petroleum system.

The Middle Siberian volcanic plateau is characterized with respect to its paleoecological environments. In this area, volcanism commenced in the Severodvinian (Vishkilian) Age. The lower (tuffaceous) part of the plateau section (Lebedev deposits) was formed in the Vyatkian Age. Its middle (tufflava) part (Khungtukun deposits) is correlative with the Goudikeng Formation (interval of 65–111 m) in the Dalongkou type section of China and corresponds to the Quadrocladus pachyphyllus ... Echinolimnadia mattoxi Zone. The top of this sedimentary unit (111 m up from the base of the Goudikeng Formation) should be correlated with the base of the Otoceras Ecozone. The upper (lava) part of the plateau (Putorana deposits) corresponds to the interval of 111–210 m, belongs to the Elatocladus linearis ... Cornia vosini Ecozone, and is older than the Hindeodus parvus Zone, which is now considered as the basal unit of the Triassic marine sequences. The volcanic plateau section shows now evidence of any biotic crisis.

Primary plant successions on volcanic deposits of the Tolbachinskii DoI Plateau (Central Kamchatka) were studied. The main factors determining the succession rate were revealed. The peculiarities of plant successions on lava flows and ash-scoria deposits differed significantly. Some common mechanisms for all volcanic regions of the world were revealed. The leading factors of plant succession on lava flows were the type of lava surface, the texture of lava, and the fine tephra accumulation rate. The main factors determining plant succession on ash-scoria deposits were wind and water erosion and the distance to the seed sources. The time of formation of a secondary permanent larch (Larix cajanderi Mayr.) forest should take about 1500-2000 years on lava flows and up to 1000 years (but not less than 300-500 years) on ash-scoria plains.

Based on 112.5 km2 of 3-D seismic data and data of 8 prospecting wells drilled volcanic rocks in the 3rd member of the Paleogene Shahejie Formation in Hongxing area of the Eastern Sag of the Liaohe Depression, Bohai Bay Basin, three levels of volcanic interfaces (stage→edifice→lithofacies) of the intermediate-mafic volcanic formation are identified to reveal favorable prospecting facies through comprehensive studies on geology, well logging and seismic data in single well and multiple wells following the seismic volcano stratigraphy principle. According to stage interfaces, three volcanic stages were identified in the 3rd member of Shahejie Formation. One or more volcanic edifice-seismic facies were identified in each volcanic stage and volcanic facies-seismic facies were identified in each volcanic edifice-seismic facies. Based on single well points, we described volcanic edifices on well-tie seismic sections; identified volcanic bodies by extracting coherent seismic attribute (superimposed volcanic edifices) taking the volcanic stages as the units; then identified volcanic edifices and volcanic lithofacies by extracting waveform classification properties. Volcanic facies mapping were completed by constituting the relationship between the volcanic facies and the seismic facies in drilling wells, seismic cross sections and mappings. There are two types of plane volcanic facies sequences in the intermediate-mafic volcanic facies of this study area: volcanic conduit facies→extrusive facies (→explosive facies)→effusive facies→volcanic sedimentary facies, volcanic conduit facies (→explosive facies)→effusive facies→volcanic sedimentary facies. Among them, the near crater assemblage (volcanic conduit, extrusive and explosive facies) has better hydrocarbon shows and is the most favorable target of hydrocarbon exploration. Key words: intermediate-mafic volcanic rock, volcanic facies, seismic facies, volcanic stratigraphy, volcanic stage, Liaohe Depression

We present the results of a detailed photogeological study of a region surrounding Acidalia Mensa (43–50°N, 15–35°W) based on analysis of a mosaic of the CTX images (nominal resolution ~5 m/px). The main result of the study is the unfolding of the geologic history of the study region and determination of absolute model ages of its major episodes. The documented history begins with the formation of a volcanic plateau of Acidalia Mensa ~4 Ga ago. The surface of the Acidalia plateau was strongly modified since its formation. The crater size-frequency distribution (CSFD) on the plateau indicates that the resurfacing was likely consisted of multiple episodes. The latest such episode recognizable by the crater statistics occurred ~3.65 Ga ago. The vast majority of the surface around Acidalia Mensa is covered by materials of the background plains that correspond to the interior unit of the Vastitas Borealis Formation (VBF). The CSFD on the background plains corresponds to an absolute model age (AMA) of ~3.58 Ga, which is completely within the range of AMAs determined for the VBF along its boundary with the southern uplands. Small-scale features such as bright cones/mounds, polygonal troughs, and flow-like mantling materials postdate the emplacement of the background plains and manifest the post-formational evolution of the VBF. The majority of crater ejecta in the study area have higher albedo in the CTX and HiRISE images, but appear as dark spots in the THEMIS-IR nighttime images. These wavelength-dependent properties of the ejecta indicate the presence of light-toned and fine-grained material beneath the surface of the background plains. This material was the source of numerous bright cones/mounds. We interpret the formation of this reservoir as the result of sorting of large amounts of water/mud deposited in the study area and, by implication, within the northern lowlands. The final episodes of the ancient geologic history of the study area were related to the emplacement of materials of the thick flows at topographically high levels within the Acidalia plateau ~3.47 Ga ago. The morphology of the flows is inconsistent with lava and we interpret the occurrences of the thick flows as the result of displacement of water-saturated regolith in the form of either soli- or gelifluction flows, or ice-cored rock glaciers.

Many of the volcanic plateau margins of the eastern, formerly glaciated, foreland of the Patagonian Andes are undermined by giant landslides (≥108 m3). One cluster of such landslides extends along the margin of the Meseta del Lago Buenos Aires (MLBA) plateau that is formed mainly by Neogene-Quaternary basalts. The dry climate is at odds with numerous >2-km long earthflows nested within older and larger compound landslides. We present a hydrological analysis, a detailed geomorphic map, interpretations of exposed landslide interiors, and radiocarbon dating of the El Mirador landslide, which is one of the largest and morphologically most representative landslide. We find that the presence of lakes on top of the plateau, representing low infiltration rates, correlates negatively with the abundance of earthflows on landslide debris along the plateau margins. Field outcrops show that the pattern of landslides and earthflows is likely controlled by groundwater seepage at the contact between the basalts and underlying soft Miocene molasse. Numerous peat bogs store water and sediment and are more abundant in earthflow-affected areas than in their contributing catchment areas. Radiocarbon dates indicate that these earthflows displaced metre-thick layers of peat in the late Holocene (

International audience; The relationships between volcanic activity and tectonics at the southernmost termination of the Main Ethiopian Rift (MER), East Africa, still represent a debated problem in the MER evolution. New constraints on the timing, evolution and characteristics of the poorly documented volcanic activity of the Dilo and Mega volcanic fields (VF), near the Kenya-Ethiopia border are here presented and discussed. The new data delineate the occurrence of two distinct groups of volcanic rocks: 1) Pliocene subalkaline basalts, observed only in the Dilo VF, forming a lava basement faulted during a significant rifting phase; 2) Quaternary alkaline basalts, occurring in the two volcanic fields as pyroclastic products and lava flows issued from monogenetic edifices and covering the rift-related faults. 40Ar/39Ar dating constrains the emplacement time of the large basal lava plateau to ~3.7 Ma, whereas the youngest volcanic activity characterising the two areas dates back to 134 ka (Dilo VF) to as recent as the Holocene (Mega VF). Volcanic activity developed along tectonic lineaments independent from those of the rift. No direct relations are observed between the Pliocene, roughly N-S-trending major boundary faults of the Ririba rift and the NE-SW-oriented structural trend characteristic of the Quaternary volcanic activity. We speculate that this change in structural trend may be the expression of (1) inherited crustal structures affecting the distribution of the recent volcanic vents, and (2) a local stress field controlled by differences in crustal thickness, following a major episode of reorganization of extensional structures in the region due to rift propagation and abandonment

The Manihiki Plateau is a Large Igneous Province (LIP) in the central Pacific. It was emplaced as part of the "Super-LIP" Ontong Java Nui and experienced fragmentation into three sub-plateaus, possibly during the break-up of Ontong Java Nui. The Manihiki Plateau is presumably the centerpiece of this "Super-LIP" and its investigation can therefore decipher the break-up mechanisms as well as the evolution of the plateau after its initial emplacement. By analyzing two seismic refraction/wide-angle reflection profiles crossing the two largest sub-plateaus of the Manihiki Plateau, the High Plateau and the Western Plateaus, we give new insights into their crustal structure and magmatic evolution. The High Plateau shows a crustal structure of 20 km thickness and a seismic P wave velocity distribution, which is comparable to other LIPs. The High Plateau experienced a strong secondary volcanism, which can be seen in relicts of seamount chain volcanism. The Western Plateaus on the other hand show no extensive secondary volcanism and are mainly structured by fault systems and sedimentary basins. A constant decrease in Moho depth (9–17 km) is a further indicator of crustal stretching on the Western Plateaus. Those findings lead to the conclusion, that the two sub-plateaus of the Manihiki Plateau experienced a different magmatic and tectonic history. Whereas the High Plateau experienced a secondary volcanism, the Western Plateaus underwent crustal stretching during and after the break-up of Ontong Java Nui. This indicates, that the sub-plateaus of the Manihiki Plateau play an individual part in the break-up history of Ontong Java Nui.

The Giant’s Causeway and Causeway Coast lies at the foot of high cliffs along the North Sea in the coast of Northern Ireland. It is composed of some 40,000 massive columns of basalt sticking out of the sea. The Giant’s Causeway itself is a sea-level promontory outcrop and pavement running out to sea. Exposure of the columns in a pavement of such perfect horizontal sections is considered unique and is also scenically remarkable. The Causeway Coast is an unparalleled displays of geological formations, remnants of volcanic activity some 50–60 million years ago, forming the largest remaining lava plateau in Europe. Geological studies of this lava flow over the last 300 years have greatly contributed to the analysis of Tertiary volcanic events in the North Atlantic.

This paper takes its inspiration from Karl W. Butzer's course on the Human Use of Landforms at the University of Chicago. It builds upon that concept through an exploration of regional settlement patterns and landforms in the Deccan volcanic province of west-central India. The first section develops a conceptual framework for analyzing human adjustment to landforms on regional, settlement, and site scales. The second section employs that framework to analyze four major landform-settlement configurations in the Deccan from antiquity to the end of the eighteenth century. The Satavahana kingdom (ca. 100 BCE to 200 CE) had a strong southeast to northwest alignment along the Godavari River. Their capital city of Paithan was located at a navigable sacred ford across the river (tirtha), which was linked with upstream confluences (sangams), tanks (kunds), mountain passes (ghats), and port cities on the Arabian Sea. Subsequent Hindu dynasties (ca. 850–1300 CE) shifted from fluvial landforms to a north-south alignment along steep mesa escarpments and buttes in the central Deccan that provided defensive fortress and cave temple sites. Sultanate and Mughal forces expanded the urban footprint on nearby plateau lands at sites protected by surrounding mesas (ca. 1330–1700 CE). These cities were supported by local watershed runoff and long distance water channels. The final precolonial phase of Deccan settlement entailed a shift from the semiarid central plateaus to humid headwaters of the Western Ghats, whose buttes and scarps provided sites for scores of forts controlled by the founder of the Maratha empire Chhatrapati Shivaji in the seventeenth century. Maratha success led to development downstream at the capital city of Pune (1627–1803 CE), located at a river confluence flanked by mesas, which combined the strategies of previous periods. Over two millennia these four distinct, yet intersecting, patterns of human-landform relations have shaped an evolving geocultural region on the Deccan plateau that deserves comparison with other flood basalt regions. Keywords: Butzer; Historical geomorphology; Flood basalt; Rock cut caves; Deccan; Maharashtra

In this chapter, the geomorphological characterization of volcanic highland of southern Georgia is presented. The orographic units are considered in detail, such as the Erusheti Highland, Mtkvari River upper gorge, Javakheti Upland with its subregions (the Akhalkalaki Plateau, the northern hilly low mountainous subregion, and the southwestern hilly subregion), Nialiskuri, Samsari and Javakheti ranges, Tsalka depression and the volcanic plateaus of Bedena, Kvemo Kartli, Chochiani, Gomareti, and Dmanisi. The text also provides geological structure, tectonic conditions, and current exogenic processes in the study region. Each subchapter is accompanied by appropriate images and maps.

The Dalinor volcanic swarm, located south of Xilinhot, Inner Mongolia of China, was a result of multistage eruptions that occurred since the Neogene period. This swarm is mainly composed of volcanic cones and lava tablelands. The objective of this study is to map the topography and morphology of this volcanic swarm. It is based on a variety of data collected from various sources, such as the digital elevation model (DEM), Landsat images, and a 1:50,000 topographic map, in addition to various software platforms, including ArcGIS, Envi4.8, Global Mapper, and Google Earth for data processing and interpretation. The results show that the overall topography of the volcanic swarm is a platform with a central swell having great undulation, sizable gradient variations, a rough surface, and small terrain relief. According to the undulating characteristics of the line profile, the volcanic swarm can be divided into four stairs with heights of 1,280 m, 1,360 m, 1,440 m, and 1,500 m. The analysis of the swath profile characterizes the two clusters of volcanoes with different height ranges and evolution. The lava tablelands and volcanic cones are distributed in nearly EW-trending belts, where tableland coverage was delineated with superposed layers of gradients and degrees of relief. According to the morphology, the volcanic cones were classified into four types: conical, composite, dome, and shield. The formation causes and classification basis for each type of volcanic cone were analyzed and their parameters were extracted. The H/D ratios of all types of volcanic cones were then statistically determined and projected to create a map of volcanic density distribution. Based on the relationship between distribution and time sequence of the formation of different volcanic cones, it can be inferred that the volcanic eruptions migrated from the margins to the center of the lava plateau. The central area was formed through superposition of multi-stage eruptive materials. In addition, a large number of early shield volcanoes were distributed on the margins. The morphological analysis of volcanic cones reveals the evolutionary stages of different types of cones. From the interpreted geomorphological indicators of faults, such as surface scarps, the pattern of volcanic cones, and the arrangement of crater major axes, it can be inferred that NE-trending and nearly EW-trending faults are present in this area, which are closely related to the formation and distribution of the volcanoes.

We report40Ar–39Ar laser step-heating age determinations on 15 stratigraphically controlled lava flows and intrusive rocks from Heard Island, Central Kerguelen Plateau (Indian Ocean). The island history began with uplift of pelagic limestone intruded by 22 Ma gabbro sills. Subaerial and wave erosion levelled the early island, producing an unconformity onto which pillow lavas, tuffaceous sediments and shallow-water, fossiliferous marine siltstone (Drygalski Formation) were deposited, beginning in late Miocene time. Two volcanic systems then formed in the late Quaternary. Big Ben dominates the larger southeast part of the island, while Mount Dixon occupies the northwest Laurens Peninsula. Feeder dykes and the early lava flows in both systems are 400–200 ka. Lava flows with evolved compositions (trachytes, trachyandesites) erupted 100–20 ka. Well-preserved parasitic cones exposed at low elevations are 15–10 ka and younger. Mawson Peak, near the summit of Big Ben, has erupted lava flows as recently as 2007. Heard Island, and nearby active McDonald Island, are subaerial features of a larger Neogene volcanic region of Central Kerguelen Plateau that includes several large sea knolls and recently identified submarine fields of small cones. This broadly distributed volcanic activity is linked to incubation of plume material at the base of the nearly stationary overlying Central Kerguelen Plateau.

The Lagavulin exploration well 217/15-1Z penetrated a c . 2.6 km thick volcanic sequence dominated by extrusive basaltic rocks spanning the Paleocene–Eocene boundary in the NE Faroe–Shetland Basin. The well comprises one of the thickest drilled sequences through the North Atlantic Igneous Province. Integrated analysis of drill cuttings and wireline-log data reveals key volcanic lithofacies: (1) tabular lava flows; (2) compound lava flows; (3) hyaloclastite; (4) volcaniclastic rocks. The volcanic facies reveal two major sub-aqueous to subaerial sequences consistent with lava delta progradation. These sequences are separated by a volcanic hiatus represented by extensive reddened soils, which preceded the re-submergence of the area. Emergence followed by submergence of the first lava delta is interpreted to record an intra-T40 transient uplift event near the Paleocene–Eocene boundary. Basalts from the lower c . 1.3 km have low TiO 2 ( 85–91 ). The hiatus correlates precisely with a change to high-TiO 2 (2.5–3.2 wt%), high-Zr/Y (>4) compositions, which dominate the upper sequence. The associated change in lava geochemistry, transient uplift and volcanic hiatus appears consistent with a transient pulse of hot buoyant plume material passing beneath the area. Supplementary material: All raw geochemical data and supplementary analyses are available at http://www.geolsoc.org.uk/SUP18888.

A previously unknown submerged volcanic field offshore western Sardinia (western Mediterranean Sea), has been identified based on swath bathymetric data collected in 2009, 2010 and 2013, and high-resolution seismic profiles collected in 2011 and 2013. About 40 conical-shaped volcanic edifices (maximum width of about 1600 m and maximum height of about 180 m) and several lava outcrops (up to 1,200 m wide) were recognized at 20 to 150 m water depth over an area of 800 km2. The volcanic edifices are mainly eruptive monogenic vents, mostly isolated with a rather distinct shape, or grouped to form a coalescent volcanic body in which single elements are often still recognizable. High-resolution seismics enabled identifying relationships between the volcanic bodies and continental margin successions. The edifices overlie a major erosional surface related to the margin exposure following the Messinian salinity crisis, and are overlain by or interbedded with an early Pliocene marine unit. This seismo-stratigraphic pattern dates the volcanic activity to the early Pliocene, in agreement with the radiometric age of the Catalano island lavas (4.7 Ma) reported in earlier studies. The morphometry of the volcanic bodies suggests that cone erosion was higher at shallow water depths. Indeed, most of the shallow edifices are strongly eroded and flattened at 125 to 130 m water depth, plausibly explained by recurrent sub-aerial exposure during Pleistocene sea-level lowstands, whereas cones in deeper water are much better preserved. Volcanic vents and lava deposits, hereafter named the Catalano volcanic field (CVF), are emplaced along lineaments corresponding to the main directions of the normal fault system, which lowered the Sinis Basin and the western Sardinia continental margin. The CVF represents a volumetrically relevant phase of the late Miocene – Quaternary anorogenic volcanic cycle of Sardinia, which is related to the first stage of the extensional tectonics affecting the island since the late Miocene.

Analysis and summary of publications on southern East Sayan, eastern Tuva, and northern Mongolia have shown that the late Pleistocene glaciation covered a large area and had a complicated dynamics of glacier advance and retreat. Starting with MIS 5, the Todza Basin and, partly, the Oka Plateau, Azas Volcanic Plateau, Mondy Basin, and river valleys in southern East Sayan were periodically covered with ice. The thickness of ice in the eastern Todza Basin was 700 m, on the Azas Volcanic Plateau it reached 300–600 m, and in the valleys of southern East Sayan it is estimated as 700–800 m. The thickness of ice in the Mondy Basin was 300–350 m. Geological and geomorphological studies and isotope surface exposure dating (10Be method) of boulders from terminal moraine complexes have provided evidence for extensive MIS 2 glacier advance in the Mondy Basin and in the Sentsa, Jombolok, and Sailag river valleys (southern East Sayan). The average age of exposure for three groups of samples is 14, 16, and 22 ka.

Igneous rock samples recovered during the 2008–09 Australian Southwest Margin Marine Reconnaissance Survey (GA-2476), off the Western Australian coast from Perth to the Wallaby Plateau, come from a variety of tectonic settings reflecting a complex magmatic history of this margin. Cretaceous rhyolite and basaltic andesite samples most likely erupted in a continental extensional setting, while younger volcanic samples reflect a transition to a mature passive continental margin with the generation of mid-ocean ridge basalt. During the last phase of volcanism, a series of volcanic cones and mounds with ocean island basalt geochemical signatures formed along the margin. The pre-rift sedimentary rocks sampled on the Wallaby Plateau support the viewpoint that it is an extended block of continental crust, overlain by syn-rift and post-rift volcanic rocks.

Over the past 30 years, the Cenozoic basalts in eastern China have been the subject of many investigations, but their origin remains highly controversial. The Abaga–Dalinuoer volcanic field in Inner Mongolia consists of an approximately 10,000 km2 lava plateau and more than 300 volcanic cones and extends northwestward to the adjacent Dariganga lava plateau of Mongolia, forming one of the largest Cenozoic volcanic fields in eastern Asia. In this paper, we concentrate on the Abaga volcanic field that comprises more than 200 monogenetic cones, including scoria cones, lava flows, and maars. Phreatomagmatism has contributed to the generation of several volcanic edifices, and the diameter of the maars craters can reach 3 to 6 km, which are among the largest in eastern China. The volcanic rocks in the Abaga area can be divided into alkaline basalts and tholeiites. According to trace element and Sr–Nd isotopic characteristics, the Abaga magmas were primarily derived from a relatively homogeneous garnet peridotite source within the asthenosphere. Variable degrees and depths of partial melting played a key role in the genesis of magma from alkaline basalts to tholeiites. In contrast to the surrounding Cenozoic volcanic fields, such as Datong, Jining, and Hanuoba, in the western block of the North China Craton, the Abaga volcanic region in the southern part of the Central Asian Orogenic Belt is distinguished by the deepest melting and the thickest lithosphere. Negative Ba-, Rb-, K-, and Ti anomalies and relatively high 87Sr/86Sr ratios suggest the presence of residual phlogopite/amphibole during mantle melting. The origin of the Abaga magma most likely required involvement of fluids released from the stagnant Pacific slab in the mantle transition zone.

The formation history of the Manihiki Plateau, a Large Igneous Province, is poorly understood. New high resolution seismic reflection data across the High Plateau, the largest edifice of the Manihiki Plateau, provides evidence for multistage magmatic emplacement. Improved data quality allows for an identification of an earlier volcanic phase, the initial formation phase (>125 Ma), in addition to the previously known volcanic formation phases: the expansion phase (125-116) formerly called main-phase and the secondary volcanic phase (100-65 Ma). This enhances the understanding of the emplacement scenario. An intrabasement reflection band IB1 reveals the end of initial volcanic formation and forms the nucleus of the High Plateau. This feature provides indications that it continued beyond the Manihiki Scarp and thus supports the hypothesis of an extension of the Manihiki Plateau to the East during the initial formation and expansion phases. The expansion phase is characterized by massive volcanic outpourings leveling and extending the basement throughout the High Plateau and the neighboring Western Plateaus, which in contrast shows massive tectonic alteration. Extrusion centers formed within the secondary volcanic phase (ending ∼65 Ma) are mainly concentrated along the margins of the High Plateau, suggesting the magmatic sources shifted from those being related to the initial emplacement and expansion phases of the High Plateau to induced volcanism at the tectonically altered margins. This article is protected by copyright. All rights reserved

The formation of the Middle Siberian Traps has been considered one of the main causes for the change in the biota at the Permian-Triassic boundary. At the first stage of the formation of the volcanic plateau (Lebedevskian time), volcanism was dominated by tuffs; at the second stage (Khungtukunian time), by tuffs and lavas; and at the last stage (Putoranian time), by flood basalts. The paper presents a paleoecological characterization of the plateau at the middle (Khungtukunian) stage, immediately before the Permian-Triassic boundary (ammonoid standard). At the beginning of this stage the plateau reached an altitude of about 500 m above sea level, at the end of the stage it was higher than 800 m above sea level (Sadovnikov and Turlova, 2004). The Khungtukunian deposits have yielded more than 230 species, belonging to more than 70 genera of plants, conchostracans, ostracods, bivalves, and fishes.

The Lausitz (Lusatia) Volcanic Field is part of the Central European Volcanic Province, and its magmas represent an alkaline trend from olivine nephelinites and basanites to trachytes and phonolites, typical for intraplate settings. Neighbouring volcanic fields are the Ceske Středohoři Mountains to the south-west and the Fore-Sudetic Basin in Lower Silesia to the east. More than 1000 volcanic structures associated with approximately 500 vents have been located within this volcanic field. Residuals of scoria cones, lava lakes, lava flows and maar-diatreme in filling occur in situ near the level of the original syn-volcanic terrain. In more deeply eroded structures, volcanic relicts outcrop as plugs or feeders. Evolved rocks occur as monogenetic domes or intrusions in diatremes, while their volcaniclastic equivalents are rare. Twenty-three localities were dated using the 40Ar/39Ar method. The ages range from 35 to 27 Ma, with a focus around 32–29 Ma, indicating Late Eocene and mainly Oligocene volcanism for the LVF. Differentiated rocks appear to be slightly younger than less differentiated. No geographical age clusters are apparent.

This study examines the neotectonic deformation and development of the Tromen massif, a Quaternary retroarc volcanic field located in the western section of the Malargüe fold and thrust belt in the Southern Central Andes. The linkages between neotectonic deformation in the intra-arc zone and the recent retroarc structures of the Tromen volcanic plateau are not clearly understood. These retroarc deformations affect the mid-section of the fold and thrust belt, leaving to the east a 200 km-wide deformed zone that can be considered inactive over the last 12–10 Ma. This out-of-sequence deformation west of the orogenic front area has not been previously addressed in detail. In this study, exhaustive mapping is used to describe and discriminate structures with a neotectonic component from those fossilized by Pleistocene strata. Two balanced cross-sections are constructed showing the distribution of the youngest deformations and their relation to pre-Miocene structures. An important means for evaluating this is the morphometric and morphological analyses that allowed identification of perturbations in the fluvial network associated with active structures. In a broader perspective, neotectonic activity in the fold and thrust belt is discussed and inferred to be caused by local mechanical weakening of the retroarc zone, due to injection of asthenospheric material evidenced by magnetotelluric surveys. Thus, deformation imposed by the oblique convergence between South American and Nazca plates, while to the south being limited to the Liquiñe-Ofqui fault system that runs through the arc zone, in the retroarc area is located at the site of magmatic emplacement, presumably in association with a thermally weakened-upper crust. This control exemplifies the relationship that exists between surficial processes, magmatic emplacement and upper asthenospheric dynamics in the Southern Central Andes. Fil: Sagripanti, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos ; Argentina Fil: Rojas Vera, Emilio Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos ; Argentina Fil: Gianni, Guido Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos ; Argentina Fil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos ; Argentina Fil: Harvey, Jonathan E.. University of Santa Barbara; Estados Unidos Fil: Farías, Marcelo. Universidad de Chile; Chile Fil: Ramos, Victor Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos ; Argentina

The Catan Lil Basin is an intermontane basin developed on the wedge top of the Miocene North Patagonian retro-arc foreland basin. This basin is formed by the growth of a west verging thick skinned fold and thrust belt. An internal anticline divides the basin into two sub-basins: Las Coloradas and Los Remolinos, with other minor isolated depocentre (La Esperanza Syncline). Due to the structural configuration the basin evolved as a compartmentalized basin, connected with an extrabasinal drainage network. Structural and sedimentological analysis of field data enable us to determine that the basin was filled in four sequences (DS-I, DS-II, DS-III and DS-IV) that recorded three major aggradational/degradational cycles characterized by alluvial-fluvial sedimentation and a final volcanic succession of olivinic basalts. The first two sequences (DS-I and DS-II) integrate a growth wedge related to tectonic uplift and limb rotation of the main anticlines. DS-III and DS-IV were deposited under post-kinematic conditions when there was no more tectonic activity in the fold and thrust belt. There is a strong difference in composition between the first sequence DS-I and the others. DS-I is composed by volcaniclastic sandstones, conglomerates and paleosols. The two other sedimentary sequences (DS-II and DS-III) are composed of purely epiclastic material. This sedimentary succession can be defined as compound valley fill occurred under general low accommodation conditions with a progressive reduction of A/S during basin evolution. The DS-IV corresponds to a volcanic plateau associated with an upper Miocene basaltic retro-arc volcanism. A new 39Ar/40Ar age for the basalts is presented in this paper that constrains the end of deposition in the Catan Lil Basin to the Upper Miocene (8.5 Ma). After this basaltic event, the foreland turned towards an erosional by-pass system in the study area., Centro de Investigaciones Geológicas

Middle Siberian trappean volcanism is considered to have been one of the major causes of the fundamental biotic change at the Permian-Triassic boundary. Accumulation of tuffs dominated the initial stage of the volcanic plateau development (Exah time), while later (Khungturunian time), tuffs and lavas accumulated, and at the conclusive stage (Putoranian time) lavas prevailed. At the end of the eruptions the height of the plateau reached 1700 m. Over 200 species and 80 genera of plants, conchostracans, ostracodes, bivalves, fishes, gastropods are known from the Putoranian. This article contains the characterization of a Putoranian plateau biota for the interval between the conodont and ammonoid standards of the P-T boundary.

Volcanic ash is a volcanic product with a wide distribution that can be used as a geological marker. In volcanic regions such as Indonesia, the identification of the sources of volcanic ash and tuff layers from different volcanoes or eruptive events is a challenging task. In this study, samples of volcanic ash from the 2010 eruption of Bromo—a relatively young and active tuff cone volcano within the Sandsea caldera in the Tengger volcanic complex in East Java, Indonesia—along with two older tuff layers from the same caldera (Widodaren tuff: 1.8 kyr and Segarawedi tuff: 33 kyr) were subjected to magnetic measurements, geochemical analyses, and petrographic analyses. The aim is to attempt to use magnetic characters as a fingerprint for volcanic ash and tuff layers. The results show that the samples had variations in grain size and magnetic domain as indicated by the hysteresis parameters. These magnetic characters correlated with the results of geochemical and petrographic analyses, suggesting that magnetic properties may potentially be used as fingerprints to identify volcanic ashes and tuff layers.

The Al-Ays Volcanic Area (AAVA) experienced a massive earthquake swarm in 2009 under the Harrat Lunayyir (HL). To examine the space distribution of basaltic lava flows in AAVA, we present here an analysis of satellite images. This has helped to identify three generations of lava flows within AAVA for the first time, their spatial extent and relationship to geological features. Various remote sensing treatments were applied to the Landsat 8 image: (a) color composites, (b) band ratioing, (c) principal component analysis, and (d) a mathematical index. Spectral analysis of the maps assists with charting the spatial configuration of the lava flows. Total area occupied by basalts is ~677 km2, of which the oldest lava flows occupy almost 52% (354 km2) and the lavas of intermediate age share 43% (295 km2) while the recent lava flows merely share 5% (28 km2), including 6.8 km2 referring to the volcanic cones. It should be noted that the generation of lava flows outlines a rather small area, of ≤20 km radius, circumventing the swarm epicenter zone. These maps may prove useful in volcanic hazard mapping for the rugged terrain.

We report sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone belt of western Dharwar Craton which is associated with rhyolites, chlorite schists and pyroclastic rocks. The pyroclastic rocks of Yalavadahalli area of Shimoga greenstone belt host volcanogenic Pb–Cu–Zn mineralization. The sediment-infill volcanic breccia is clast-supported and comprises angular to sub-angular felsic volcanic clasts embedded in a dolomitic matrix that infilled the spaces in between the framework of volcanic clasts. The volcanic clasts are essentially composed of alkali feldspar and quartz with accessory biotite and opaques. These clasts have geochemical characteristics consistent with that of the associated potassic rhyolites from Daginkatte Formation. The rare earth elements (REE) and high field strength element (HFSE) compositions of the sediment-infill volcanic breccia and associated mafic and felsic volcanic rocks suggest an active continental margin setting for their generation. Origin, transport and deposition of these rhyolitic clasts and their aggregation with infiltrated carbonate sediments may be attributed to pyroclastic volcanism, short distance transportation of felsic volcanic clasts and their deposition in a shallow marine shelf in an active continental margin tectonic setting where the rhyolitic clasts were cemented by carbonate material. This unique rock type, marked by close association of pyroclastic volcanic rocks and shallow marine shelf sediments, suggest shorter distance between the ridge and shelf in the Neoarchean plate tectonic scenario.

Petrological and geochemical characteristics of low- and high-temperature alterations were investigated in volcanic rocks from the northern Philippine Sea. The assemblage of secondary minerals is divided into two groups based on microprobe and XRD analyses. The first group, comprising samples from the Kyushu-Palau Ridge and Urdaneta Plateau, includes calcite, phillipsite, clay minerals and Fe-oxyhydroxides, reflecting low-temperature alteration. The content of secondary deposition is high in the Kyushu-Palau Ridge, but low in the Urdaneta Plateau. The second group, consisting of samples from the Amami Plateau, includes secondary alkali feldspar, analcime, and chlorite, reflecting high-temperature hydrothermal alteration. As groundmass alteration is dominant in the studied volcanic rocks, the alteration index, defined as the ratio of secondary minerals in voids to the total material count, is useful for estimating alteration degree when precise identification of secondary materials is difficult in highly vesicular rocks. Alteration indexes correlate with bulk H2O+ and loss on ignition (LOI) contents, and bulk major and trace element compositions of the studied volcanic rocks change with alteration. The difference of alteration types in three regions may depend on the tectonic setting of volcanism. That is: (i) the Kyushu-Palau Ridge is covered with the last lava flow of rifting volcanism associated with spreading of the Shikoku Basin, and the volcanics reacted with circulating seawater under low temperatures and oxidative conditions; (ii) the Urdaneta Plateau was formed as a result of intra-plate volcanism, and the volcanics were under seafloor weathering without seawater circulation associated with volcanic activity; and (iii) the Amami Plateau was produced by Cretaceous arc volcanism, which suffered high-temperature alteration associated with intrusive activity of tonalite.

A large number of in-situ volcanic reservoirs have been discovered from the Meso-Cenozoic rift basin group in eastern China. Based on drilling results in combination with geological and geophysical analysis, a case study from the Early Cretaceous Xujiaweizi fault-depression shows that the formation mechanism of in-situ volcanic reservoirs is characterized by “fault-controlled body, body-controlled facies, facies-controlled reservoir, and reservoir-controlled accumulation”. In other words, deep faults control the volcanic eruption type, volcanic body, and gas reservoir distribution; the volcanic body determines the spatial distribution of volcanic facies and volcanic gas reservoir size; the volcanic facies control reservoir physical properties and effective thickness of gas formation; the volcanic reservoir properties control gas reservoir type and gas productivity. The result is useful to guiding the discovery of in-situ volcanic gas reservoirs in faulted basins in both theory and practice.

Onset and termination of Eocene felsic volcanism in the Chilcotin Plateau of central British Columbia is constrained between 54.6 and 46.6 Ma by 33 new U–Pb and 40Ar/39Ar isotopic age determinations. Dates were obtained from representative felsic coherent and fragmental volcanic rocks that comprise the Ootsa Lake Group. The resulting chronostratigraphy shows that magma compositions evolved from felsic to intermediate, with no spatial migration of the volcanic activity. Rhyolitic compositions are oldest; and are overlain by dacitic rocks with varied phenocrysts assemblages. In many parts of the Chilcotin Plateau, the Eocene stratigraphy is capped by distinctive vitreous black dacite lavas, which are contemporaneous with andesitic lavas of the Endako Group in the Nechako Plateau to the north. Crystallization ages from Ootsa Lake Group rocks of the Chilcotin Plateau overlap age determinations from correlative rocks of the Nechako Plateau and southern BC. Collectively, this geochronological dataset supports previous suggestions of a voluminous Early Eocene-aged (∼55–46 Ma) period of volcanism in the Intermontane Belt. The abrupt initiation of volcanism, as well as the wide extent, thickness, and compositions that characterize Eocene volcanic rocks may be explained by cessation of subduction and formation of a slab gap beneath British Columbia in the Early Eocene.