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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.

On the Ground • When Yellowstone National Park (YNP) was established in 1872, American bison (Bison bison) were living in the park's forests and mountains. • A study conducted in the 1960s concluded that those were Mountain bison (Bison bison athabascae), a subspecies adapted to mountain habitat. It was assumed that those historical bison occupied their native habitat and had done so in prehistoric times. • When archaeological evidence of YNP bison was discovered in the mid-1990s it seemed reasonable to assume that those bones were derived from a herd of native prehistoric bison. • However, a review of archaeological, historical, genetic, and ecological evidence suggests a different history. Namely, herds of bison were absent before 1840. Sometime between 1840 and the mid-1850s, plains bison were driven into the mountain forest in and near YNP. In those forests, bison were relatively safe from horse-mounted, bow-and-arrow-armed Native American hunters. • Archaeological evidence suggests that YNP’s prehistoric bison were bulls that left herds on the low-elevation plains that surround the park; the bulls would have traveled up mountain drainages to the Yellowstone volcanic plateau. • Bison played no significant role in the ecological processes that shaped YNP’s prehistoric landscape. YNP’s modern bison herd is causing significant changes in range condition.

Highlights • The volcanic nature of the Mozambique Ridge is clearly established. • It is a Large Igneous Province. • It is formed by a mantle plume originating from the African LLSVP. Abstract The Mozambique Ridge (MOZR) is one of several bathymetric highs formed in the South African gateway shortly after the breakup of the supercontinent Gondwana. Two major models have been proposed for its formation - volcanic plateau and continental raft. In order to gain new insights into the genesis of the Mozambique Ridge, R/V SONNE cruise SO232 carried out bathymetric mapping, seismic reflection studies and comprehensive rock sampling of the igneous plateau basement. In this study, geochemical data are presented for 51 dredged samples, confirming the volcanic origin of at least the upper (exposed) part of the plateau. The samples have DUPAL-like geochemical compositions with high initial 87Sr/86Sr (0.7024–0.7050), low initial 143Nd/144Nd (0.5123–0.5128) and low initial 176Hf/177Hf (0.2827–0.2831), and elevated initial 207Pb/204Pb and 208Pb/204Pb at a given 206Pb/204Pb (Δ7/4 = 2–16; Δ8/4 = 13–167). The geochemistry, however, is not consistent with exclusive derivation from an Indian MORB-type mantle source and requires a large contribution from at least two components. Ratios of fluid-immobile incompatible elements suggest the addition of an OIB-type mantle to the ambient upper mantle. The MOZR shares similar isotopic compositions similar to mixtures of sub-continental lithospheric mantle end members but also to long-lived, mantle-plume-related volcanic structures such as the Walvis Ridge, Discovery Seamounts and Shona hotspot track in the South Atlantic Ocean, which have been proposed to ascend from the African Large Low Shear Velocity Province (LLSVP), a possible source for DUPAL-type mantle located at the core-mantle boundary. Interestingly, the MOZR also overlaps compositionally with the nearby Karoo-Vestfjella Continental Flood Basalt province after filtering for the effect of interaction with the continental lithosphere. This geochemical similarity suggests that both volcanic provinces may be derived from a common deep source. Since a continuous hotspot track connecting the Karoo with the MOZR has not been found, there is some question about derivation of both provinces from the same plume. In conclusion, two possible models arise: (1) formation by a second mantle upwelling (blob or mantle plume), possibly reflecting a pulsating plume, or (2) melting of subcontinental lithospheric material transferred by channelized flow to the mid-ocean ridge shortly after continental break-up. Based on geological, geophysical and geochemical observations from this study and recent published literature, the mantle-plume model is favored.

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.

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.

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.

The Neogene Kağızman–Tuzluca Basin is located in the NE Anatolia and extends eastward into Armenia Oktemberian Basin. The Halıkışlak (Late Oligocene), Turabi and Tuzluca formations (Lower–Middle Miocene) are time equivalents of the organic-rich Oligo-Miocene Maikop Series in the Caspian region. However, depositional conditions within the KBT are appreciably different and source rocks are not as richer as it. The Halıkışlak Formation has little source rock potentials, with very low values of TOC (0.04–0.25%), HI (14–90 mg HC/TOC) and genetic potential-GP (i.e. Rock–Eval S 1 + S 2 = 0.05 to 0.22 mg HC/g rock). Although a peat facies sample has a relatively high TOC (6.78%), T max of 428 °C, HI values are very low (45 mg HC/TOC). TOC and GP values for the Tuzluca Formation are between 0.06 and 0.39 wt%, and 0.16–1.51 mg HC/g rock, respectively. Some levels of the Turabi Formation have TOC contents up to 6.14 wt%; however, mainly T max values are low 435 °C, and HI range from 25 to 54 mg HC/TOC. The extract of one low-maturity Turabi sample possesses biomarker distributions of an immature rock. Low relative abundance of tricyclic terpane and dominant C29 ααα (20R) are in accordance with the immature source rock. Some samples collected from the outcrops nearby Pliocene/Pleistocene lava series show localized maturation stage. We suggest that the Oligocene to Middle Miocene units could be more studied beneath the volcanic plateau.

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.

Volcanism associated with the Kerguelen Large Igneous Province is found scattered in southwestern Australia (the ca 136 to ca 130 Ma Bunbury Basalts, and ca 124 Ma Wallaby Plateau), India (ca 118 Ma Rajmahal Traps and Cona Basalts), and Tibet (the ca 132 Ma Comei Basalts), but apart from the ∼70 000 km2 Wallaby Plateau, these examples are spatially and volumetrically minor. Here, we report dredge, geochronological and geochemical results from the ∼90 000 km2 Naturaliste Plateau, located ∼170 to ∼500 km southwest of Australia. Dredged lavas and intrusive rocks range from mafic to felsic compositions, and prior geophysical analyses indicate these units comprise much of the plateau substrate. 40Ar/39Ar plagioclase ages from mafic units and U–Pb zircon ages from silicic rocks indicate magmatic emplacement from 130.6 ± 1.2 to 129.4 ± 1.3 Ma for mafic rocks and 131.8 ± 3.9 to 128.2 ± 2.3 Ma for silicic rocks (2σ). These Cretaceous Naturaliste magmas incorporated a significant component of continental crust, with relatively high 87Sr/86Sr (up to 0.78), high 207Pb/204 Pb ratios (15.5–15.6), low 143Nd/144Nd (0.511–0.512) and primitive-mantle normalised Th/Nb of 11.3 and La/Nb of 3.97. These geochemical results are consistent with the plateau being underlain by continental basement, as indicated by prior interpretations of seismic and gravity data, corroborated by dredging of Mesoproterozoic granites and gneisses on the southern plateau flank. The Cretaceous Naturaliste Plateau igneous rocks have signatures indicative of extraction from a depleted mantle, with trace-element and isotopic values that overlap with Kerguelen Plateau lavas reflect crustal contamination. Our chemical and geochronological results therefore show the Naturaliste Plateau contains evidence of an extensive igneous event representing some of the earliest voluminous Kerguelen hotspot magmas. Prior work reports that contemporaneous correlative volcanic sequences underlie the nearby Mentelle Basin, and the Enderby Basin and Princess Elizabeth Trough in the Antarctic. When combined, the igneous rocks in the Naturaliste, Mentelle, Wallaby, Enderby, Princess Elizabeth, Bunbury and Comei-Cona areas form a 136–124 Ma Large Igneous Province covering >244 000 km2.

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.

The article discusses data on paleosol, mineralogy, and paleobotany obtained as a result of studying material collected from the Maastricht-Early Paleocene sediments of the Tanyurer Formation of South Chukotka. The burial of organic matter in the sedimentary rock of the Tanyurer Formation is associated with deflationary processes during the period of activation of volcanic activity. On the drained volcanic plateau of soil formation, a sod humus-accumulative process prevailed under the steppe vegetation. Humic substance dispersed in sedimentary rock was represented by a group of humins resistant to microbial decomposition. As a result of exposure to high pressures and temperatures, the colloidal form of humus was transformed into kerogen. Organic compounds (cellulose, lignin) in the plant tissue of buried tree trunks were replaced by silicon compounds. Weathering processes have affected the thin surface layer of dense sedimentary rock. Under the influence of the temperature and humidity gradient, loosening of loose rock and disintegration of clots of colloidal forms of humus occurred.

Author(s): Behar, Nicole; Shaar, Ron; Tauxe, Lisa; Asefaw, Hanna; Ebert, Yael; Heimann, Ariel; Koppers, Anthony AP; Ron, Hagai

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

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.

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

The bacterial biocontrol agent Serratia entomophila and the insecticide diazinon were applied as separate granular formulations with ryegrass seed and compared with a seedonly control treatment on three pastures of different ages and composition on the North Island volcanic plateau In the first 2 years diazinon and S entomophila significantly reduced healthy grass grub populations compared with the control However by the third year populations in the diazinon treatments had recovered and were significantly higher than in S entomophila or control plots Grass grub populations were reduced by disease outbreaks after S entomophila was applied which infected >40 of grass grub larvae in the treated plots in year two Bacterial extraction from soil a year after application confirmed establishment and persistence of S entomophila in treated plots Visual positive pasture growth responses were noted in both the S entomophila and diazinontreated plots

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.

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

An ecozone Quadrocladus pachyphyllus ... Prilukiella (?) tomiensis has been described in the lower part of the Middle Siberia trap volcanics. It differs very much from the underlying coal-bearing deposits with so called “furrowed” Cordaites and significantly differs from the overlying rocks. On the Russian platform it corresponds to the topmost (Chernigov) floristic complex of the Upper Permian Tatarian series. It is not identified reliably in the unsatisfactory chosen standard section of the non-marine GSSP of Triassic. The units of mountain, plain and seaside sedimentation levels are distinguished as coenozones - separate, independent spatial parts of the ecozone. The woody layer is prevailed with: Quadrocladus pachyphyllus, Elatocladus linearis (mountain), Voltzia (?) avamica, Elatocladus linearis, Quadrocladus pachyphyllus (plain), Pseudovoltzia, Quadrocladus borealis, Q. dvinensis, Geinitzia subangarica (seaside). The grassy level of damp slopes is formed by: Acrostichides linnaeaefolius, Cladophlebis lobifera, Madygenia borealis (mountain), Acrostichides linnaeaefolius, А. tunguskanus, Cladophlebis kaoiana, Madygenia borealis, Pursongia beloussovae, Lepidopteris arctica (plain), Schvedopteris lobata, Madygenia, borealis, Phylladoderma aequalis, Р. annulata, Р. rastorguevii, Fefilopteris pilosa (seaside). Dominants of grassy cover of lowlands are Arthropitys prynadae (plain), Pursongia beloussovae, Tatarina (seaside), Paracalamites triassicum.

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

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 review the biology and ecology of Metrosideros excelsa (Myrtaceae), an endemic angiosperm evergreen tree. Metrosideros excelsa belongs to a conspicuous and widely distributed Pacific Basin genus, with centres of diversity in both New Zealand and New Caledonia. Metrosideros excelsa is an iconic tree species that forms a significant component of northern New Zealand's exposed coastal headland and cliff vegetation. Where conditions are more favourable, M. excelsa forms tall coastal forest, ranging from simple young high-density stands to diverse mature forest. Inland, M. excelsa stands are confined to the margins of lakes and rivers on the Central Volcanic Plateau, where some may originate from early Māori plantings. Metrosideros excelsa is reliant on stochastic disturbance events (e.g. landslides, volcanic eruptions) to create open sites necessary for regeneration. Mass flowering (December–January), followed by abundant production of wind-dispersed seed maximises chance colonisation of such sites. Since ...

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.

Drilling, gravity, magnetic observation and seismic facies are combined to identify the Cenozoic volcanic rocks in the Pearl River Mouth Basin and the Southeast Hainan Basin in the northern South China Sea, and to analyze how their lithology, distribution characteristics and volcanic activity influence on hydrocarbon accumulation. As a result, more than 70 volcanic bodies are ascertained. They are divided into two types: (1) laminated lava and pyroclastic rocks in the Cenozoic sedimentary sequence; and (2) conoid, mounded or wedged basalt with rigid basement under the Cenozoic sedimentary sequence. In the early Cenozoic (E1-E2), the acidic, neutral and basic volcanic rocks developed, while in the mid-late Cenozoic (E3-Q), single basic rocks existed intensively. The volcanic lithofacies mainly include the lower and middle effusive subfacies and the pyroclastic flow deposit explosive subfacies. Spatially, from the Southeast Hainan Basin to the Pearl River Mouth Basin, the Cenozoic volcanic activity gradually enhances; from shallow water area to the Central Basin of the South China Sea, the scale of Cenozoic volcanic rocks increases gradually, and the age tends to be younger. These activities improve the formation temperature, reduce the hydrocarbon generation threshold, and promote the hydrocarbon accumulation. Volcanic rocks in Wenchang Formation (E2w) to Zhujiang Formation (N1z) provide favorable conditions for hydrocarbon accumulation, so they are important targets in the deep exploration. Key words: northern South China Sea, Pearl River Mouth Basin, Southeast Hainan Basin, Cenozoic, volcanic rocks, lava, pyroclastic rocks, hydrocarbon accumulation

Under conditions of active volcanism, the soils on different geomorphic positions (from high-mountain landscapes to river valleys) are formed under the impact of periodic ashfalls. The exogenous processes affect the redistribution of volcanic ashes by the elements of the relief, so that the soils of different altitudinal zones have their own morphological specificity. It is suggested that two additional types of volcanic soils should be included in the new Russian soil classification: the type of alluvial volcanic soils in the order of volcanic soils and the type of volcanic lithozems in the order of lithozems. These soils can be considered intergrades between volcanic and alluvial soils and between volcanic soils and lithozems, respectively.

[1] The volcanic domes, cones, sinuous rilles, and pyroclastic deposits of the Marius Hills region of the Moon (~13.4°N, 304.6°E) represent a significant episode of magmatic activity at or near the lunar surface that is still poorly understood. Comparisons between LROC NAC block populations, Mini-RF data, and Diviner-derived rock abundances confirm that blocky lava flows comprise the domes of the Marius Hills. 8 µm features measured by Diviner indicate that the domes are not rich in silica and are not significantly different than surrounding mare materials. LROC observations indicate that some of the dome-building lava flows originated directly from volcanic cones. Many of the cones are C-shaped, while others are irregularly shaped, and local topography and lava eruptions affect cone shape. In general, the cones are morphologically similar to terrestrial cinder and lava cones and are composed of varying amounts of cinder, spatter, and lava. Many of the cones are found in local groupings or alignments. The wide range of volcanic features, from broad low domes to steep cones, represents a range of variable eruption conditions. Complex morphologies and variable layering show that eruption conditions were variable over the plateau.

[1] Mass flows on volcanic islands generated by volcanic lava dome collapse and by larger-volume flank collapse can be highly dangerous locally and may generate tsunamis that threaten a wider area. It is therefore important to understand their frequency, emplacement dynamics, and relationship to volcanic eruption cycles. The best record of mass flow on volcanic islands may be found offshore, where most material is deposited and where intervening hemipelagic sediment aids dating. Here we analyze what is arguably the most comprehensive sediment core data set collected offshore from a volcanic island. The cores are located southeast of Montserrat, on which the Soufriere Hills volcano has been erupting since 1995. The cores provide a record of mass flow events during the last 110 thousand years. Older mass flow deposits differ significantly from those generated by the repeated lava dome collapses observed since 1995. The oldest mass flow deposit originated through collapse of the basaltic South Soufriere Hills at 103–110 ka, some 20–30 ka after eruptions formed this volcanic center. A ~1.8 km3 blocky debris avalanche deposit that extends from a chute in the island shelf records a particularly deep-seated failure. It likely formed from a collapse of almost equal amounts of volcanic edifice and coeval carbonate shelf, emplacing a mixed bioclastic-andesitic turbidite in a complex series of stages. This study illustrates how volcanic island growth and collapse involved extensive, large-volume submarine mass flows with highly variable composition. Runout turbidites indicate that mass flows are emplaced either in multiple stages or as single events.

Neogene back-arc mafic volcanism in the northern Puna Plateau produced a suite of mainly high-Mg, calc-alkaline, basaltic andesites to andesites that form small scoria cones and lava fields. We present the first comprehensive geochemical study of the mafic suite in the northern Puna that complements work on similar rocks from the southern Puna Plateau. The emphasis is on magma genesis and evolution in both areas, and on a combined interpretation of the two regional datasets in the geodynamic context of back-arc magmatism in the central Andes. The results from the northern Puna suite (bulk-rock and mineral compositions, thermobarometry and radiogenic isotope ratios) are consistent with a predominantly asthenospheric source for the mafic magmas, with variable but locally significant contamination by crustal material. Quantifying the crustal and mantle input fails in most cases because the data display contradictory features, such as high compatible element contents (Mg, Ni, Cr) paired with moderate contents of silica and incompatible lithophile elements that defy classical models of magma mixing, fractionation and assimilation. We suggest that magma evolution involved selective assimilation during turbulent flow, probably at more than one level in the crust. Comparison with the southern Puna mafic suite reveals many features in common (high magma temperatures, textural evidence of rapid magma ascent and cooling, assimilation of crust at different depths). However, the volume of erupted magma is greater in the south than in the north and the volcanism in the south is slightly younger. There is much compositional overlap between the two regions, but the southern Puna suite extends to more primitive compositions. These differences suggest a stronger crustal influence in the northern Puna andesites, which we suggest is due to the presence of an extended upper-crustal melt zone associated with the Altiplano?Puna ignimbrite province. Radiogenic Sr and Nd isotope data from both suites define two diverging trends of variation with MgO that can be explained with a crustal component common to both trends, similar to the silicic ignimbrites, and two contrasting mantle components. The more common and regionally more widespread of the two mantle components (also seen in the frontal arc magmas) has 87Sr/86Sr and 143Nd/144Nd values of 0·705 and 0·5126, respectively, which we attribute to an asthenospheric source enriched by subduction erosion. The less common of the two has Sr and Nd initial ratios (0·708 and 0·51235) that we attribute to melting or assimilation of enriched lithosphere. This component has been found only in the northern Puna and it may have an origin in delaminated lithosphere. Fil: Maro, Guadalupe. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; Argentina Fil: Caffe, Pablo Jorge. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; Argentina Fil: Romer, Rolf L. German Research Centre for Geosciences; Alemania Fil: Trumbull, Robert B. German Research Centre for Geosciences; Alemania

It has been reported that the characteristics of a very old wood charcoal sample are different from those of modern wood charcoal according to its state of preservation (Cohen-Ofri et al. 2006; Rebollo et al. 2008). It can be assumed that these differences may lead to some difficulties when radiocarbon dating very old wood charcoal samples. To investigate this problem, we studied a carbonized trunk of Prunus pendula for. acendens tree buried in lava and found at the Hantan River lava plateau on the Korean Peninsula. The 14C date of this sample was previously measured as >30,000 BP. However, separate 14C results of its outer crust and inner wood showed a considerable difference, exceeding the estimated age differences by tree-ring counting. To study the reason for this discrepancy, optical microscopy and FTIR (Fourier transform infrared spectroscopy) were performed to examine the differences in the structural and chemical states of the samples. For reference data and to expand our understanding of very old wood charcoal, we applied the same analysis tools (AMS, FTIR, FE-SEM, EDS, and optical microscopy) to a variety of wood charcoals and original wood. From these analyses, we noticed considerable chemical changes in the outer crust sample, and this might explain the age discrepancy. Although it seems that the age difference might be due to the digestion of 14C-free CO2 from a volcanic environment, this explanation would not account for such a large value in the age difference.

Oceanic plateaus form by mantle processes distinct from those forming oceanic crust at divergent plate boundaries. Eleven drillsites into igneous basement of Kerguelen Plateau and Broken Ridge, including seven from the recent Ocean Drilling Program Leg 183 (1998-99) and four from Legs 119 and 120 (1987-88), show that the dominant rocks are basalts with geochemical characteristics distinct from those of mid-ocean ridge basalts. Moreover, the physical characteristics of the lava flows and the presence of wood fragments, charcoal, pollen, spores and seeds in the shallow water sediments overlying the igneous basement show that the growth rate of the plateau was sufficient to form subaerial landmasses. Most of the southern Kerguelen Plateau formed at ~ 110 Ma, but the uppermost submarine lavas in the northern Kerguelen Plateau erupted during Cenozoic time. These results are consistent with derivation of the plateau by partial melting of the Kerguelen plume. Leg 183 provided two new major observations about the final growth stages of the Kerguelen Plateau. 1: At several locations, volcanism ended with explosive eruptions of volatilerich, felsic magmas; although the total volume of felsic volcanic rocks is poorly constrained, the explosive nature of the eruptions may have resulted in globally significant effects on climate and atmospheric chemistry during the late-stage, subaerial growth of the Kerguelen Plateau. 2: At one drillsite, clasts of garnet-biotite gneiss, a continental rock, occur in a fluvial conglomerate intercalated within basaltic flows. Previously, geochemical and geophysical evidence has been used to infer continental lithospheric components within this large igneous province. A continental geochemical signature in an oceanic setting may represent deeply recycled crust incorporated into the Kerguelen plume or continental fragments dispersed during initial formation of the Indian Ocean during breakup of Gondwana. The clasts of garnet-biotite gneiss are the first unequivocal evidence of continental crust in this oceanic plateau. We propose that during initial breakup between India and Antarctica, the spreading center jumped northwards transferring slivers of the continental Indian plate to oceanic portions of the Antarctic plate. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

In the Obongri-Goseong area of Gangwondo, South Korea, there are six densely distributed volcanic edifices i.e., Duibaejae, Oeumsan, Galmibong, 249 m height, 166 m height, and 102 m height, and two other volcanic edifices including Goseongsan and Unbongsan volcanic edifice that are separately located from a distance. A previously undiscovered 249m volcanic edifice in Obongri was found in this investigation, and the six volcanic edifices distributed in Obongri will be referred to as the Obongri volcanic edifice group. Volcanic edifices in this area were interpreted by other researchers as being volcanic plug, plug dome, and cylindrical volcanic pipe type edifices. The aim of this study is to investigate the aspect of volcanic activity in the Obongri-Goseong area and the formation of volcanic edifices by examining of the shape of volcanic edifices, stratigraphy, and characterization of volcanic products. All the volcanic edifices in the area are composed of basaltic rocks on the Mesozoic granite basement, and the prevalence of the dome shape increased towards the upper part of the mountain. Three volcanic edifices (Duibaejae, 166 m height, 102 m height) include intercalated pyroclastic deposits between the basaltic rocks and the basement. The pyroclastic deposit in the Duibaejae volcanic edifice is composed of quartz, feldspar, granite fragments originated from the basement, and scoria fragments originated from the volcanic eruption. In addition to angular olivine, plagioclase, and pyroxene xenocrysts, all the basaltic rocks contained mantle xenolith, gabbroic xenolith originated from the lower crust, and granitic xenolith originated from the basement. This fact indicates that magma rapidly rose to the surface and that the volcanic activity was explosive. It is also interpreted that, as the basaltic magma became highly viscous due to the large amount of xenocrysts, the erupted magma formed a dome structure on the surface. The original dome structure was then severely eroded out leaving a plug dome formation on the basement.

Three distinct radiolarian assemblages were obtained in this study; two of them were extracted from large blocks of radiolarites included in a mélange NW of Lake Sevan (Dzknaget). The latest Tithonian-Late Valanginian assemblage comes from a coherent sequence of 6–7 m-thick radiolarites with intercalations of lavas and rounded blocks of shallow-water limestones. The Late Barremian-Early Aptian assemblage found in the second block allows correlation with radiolarites dated recently in Karabagh. A third radiolarian assemblage comes from Vedi and establishes that radiolarian ooze was accumulated in the Tethyan realm of the Lesser Caucasus until at least the middle Albian. A synthesis of all available micropaleontological (radiolarian) and geochronological ages for the ophiolites present in Armenia and Karabagh points to the following scenario for their geological evolution: the initial phase of oceanic floor spreading was under way during the Late Triassic (Carnian) or even slightly before; the bulk of oceanic lithosphere preserved today in the Lesser Caucasus was formed during the Jurassic; evidence for subaerial volcanic activity is recorded in tuffite intercalations in the Middle-Upper Jurassic radiolarian cherts; an oceanic volcanic plateau was formed during the Late Barremian-Aptian (or possibly even before) while the obduction of ophiolites took place during the Coniacian-Santonian.The geological history of ophiolites in the Lesser Caucasus shares a number of similarities with the Izmir-Ankara-Erzincan suture zone (i.e. initiation of ocean spreading during the Carnian, obduction after the Cenomanian), but there are also some differences especially with respect to the timing of the oceanic plateau emplacement.

We determined the possible compensation depths for relief harmonics of different degrees and orders. The relief is shown to be completely compensated within the depth range of 0 to 1400 km. The lateral distributions of compensation masses are determined at these depths and the maps are constructed. The possible nonisostatic vertical stresses in the crust and mantle of Mars are estimated to be 64 MPa in compression and 20 MPa in tension. The relief anomalies of the Tharsis volcanic plateau and symmetric feature in the eastern hemisphere could have arisen and been maintained dynamically due to two plumes in the mantle substance that are enriched with fluids. The plumes that originate at the core of Mars can arise and be maintained by the anomalies of the inner gravitational field achieving +800 mGal in the region of plume formation, - 1200 mGal above the lower mantle-core transition layer, and -1400 mGal at the crust., 9 pages, 5 figures

Volcanic rocks in the Sonoma volcanic field in the northern California Coast Ranges contain heterogeneous assemblages of a variety of compositionally diverse volcanic rocks. We have used field mapping, new and existing age determinations, and 343 new major and trace element analyses of whole-rock samples from lavas and tuff to define for the first time volcanic source areas for many parts of the Sonoma volcanic field. Geophysical data and models have helped to define the thickness of the volcanic pile and the location of caldera structures. Volcanic rocks of the Sonoma volcanic field show a broad range in eruptive style that is spatially variable and specific to an individual eruptive center. Major, minor, and trace-element geochemical data for intracaldera and outflow tuffs and their distal fall equivalents suggest caldera-related sources for the Pinole and Lawlor Tuffs in southern Napa Valley and for the tuff of Franz Valley in northern Napa Valley. Stratigraphic correlations based on similarity in eruptive sequence and style coupled with geochemical data allow an estimate of 30 km of right-lateral offset across the West Napa-Carneros fault zones since ∼5 Ma. The volcanic fields in the California Coast Ranges north of San Francisco Bay are temporally and spatially associated with the northward migration of the Mendocino triple junction and the transition from subduction and associated arc volcanism to a slab window tectonic environment. Our geochemical analyses from the Sonoma volcanic field highlight the geochemical diversity of these volcanic rocks, allowing us to clearly distinguish these volcanic rocks from those of the roughly coeval ancestral Cascades magmatic arc to the west, and also to compare rocks of the Sonoma volcanic field to rocks from other slab window settings.

Peninsula area was built up by thick Tertiary sequence of volcanic flows and volcaniclastic rocks. Early Cretaceous tholeiite basalt is the oldest sequence of volcanic rocks interpreted to have formed as part of a wide spread submarine volcano or volcanic complex within an MORB characterized by rapid volcanism. Miocene to Quaternary volcanisms from volcanic arcs contributed sequences of lava flows and pyroclastic rocks of dacitic, andesitic and basaltic rock types forming the major mountain chains of southeast Sabah. This Neogene volcanic sequence is dominated by low to high K-calc alkaline andesitic to dacitic volcanic rocks similar to modern island arc type. The subaerial of the latest lava flows of the region indicates volcanism consistent with tholeiitic basalt type. It has been accepted that during the Cenozoic, Sabah has been subjected to series of major tectonic regimes. A number of deformation phases have been determined include: Middle Eocene, Middle Miocene and Plio-Pleistocene phases of crustal movements of this region. The area appeared, therefore, to have been subjected to compressional tectonic regime throughout much of the late Cenozoic. However, the structural and sedimentological expression of these tectonic regimes varies considerably. It is suggested here that compressional episodes were interspersed with periods of active transtensional basin formation and that Late Miocene extension of the eastern part of Sabah which was related to compressional forces. On the basis of geological data and kinematic reconstructions, two types of island arcs can be differentiated: those related to the progressive closing of the Celebes and Sulu marginal basins during Middle Miocene and those belonging to the south Philippine Sea Plate during Plio-Pleistocene. The combined age and chemistry for these two magmatic belts allow us to decipher the Tertiary evolution of the complex zone of interaction of the Semporna Peninsula and the surrounding areas. This Tertiary sequence is underlain by the Early Cretaceous pillow lava basalt, and culminated by the late Pleistocene volcanisms those contributing to the major topography of the area include Andrassy, Lucia, Maria, Wullersdorf and Magdalena mountains formed the prominent topographic features of the area. This youngest volcanic apron covers an extensive area of the Semporna Peninsula. Semporna volcanic associations form important link with the long chain of Tertiary volcanic activities in this region that extend from the Sulu Archipelago, Philippines to the southeastern part of Sabah.

Neogene to Quaternary volcanic/magmatic activity in the Carpathian-Pannonian Region (CPR) occurred between 21 and 0.1 Ma with a distinct migration in time from west to east. It shows a diverse compositional variation in response to a complex interplay of subduction with rollback, back-arc extension, collision, slab break-off, delamination, strike-slip tectonics and microplate rotations, as well as in response to further evolution of magmas in the crustal environment by processes of differentiation, crustal contamination, anatexis and magma mixing. Since most of the primary volcanic forms have been affected by erosion, especially in areas of post-volcanic uplift, based on the level of erosion we distinguish: (1) areas eroded to the basement level, where paleovolcanic reconstruction is not possible; (2) deeply eroded volcanic forms with secondary morphology and possible paleovolcanic reconstruction; (3) eroded volcanic forms with remnants of original morphology preserved; and (4) the least eroded volcanic forms with original morphology quite well preserved. The large variety of volcanic forms present in the area can be grouped in a) monogenetic volcanoes and b) polygenetic volcanoes and their subsurface/intrusive counterparts that belong to various rock series found in the CPR such as calc-alkaline magmatic rock-types (felsic, intermediate and mafic varieties) and alkalic types including K-alkalic, shoshonitic, ultrapotassic and Na-alkalic. The following volcanic/subvolcanic forms have been identified: (i) domes, shield volcanoes, effusive cones, pyroclastic cones, stratovolcanoes and calderas with associated intrusive bodies for intermediate and basic calclkaline volcanism; (ii) domes, calderas and ignimbrite/ash-flow fields for felsic calc-alkaline volcanism and (iii) dome flows, shield volcanoes, maars, tuffcone/tuff-rings, scoria-cones with or without related lava flow/field and their erosional or subsurface forms (necks/ plugs, dykes, shallow intrusions, diatreme, lava lake) for various types of K- and Na-alkalic and ultra-potassic magmatism. Finally, we provide a summary of the eruptive history and distribution of volcanic forms in the CPR using several sub-region schemes.

Volcanic eruptions and lava flows comprise one of the most highly stressed terrestrial environments for the survival of biological organisms; the destruction of botanical and biological colonies by molten lava, pyroclastic flows, lahars, poisonous gas emissions and the deposition of highly toxic materials from fumaroles is the normal expectation from such events. However, the role of lichens and cyanobacteria in the earlier colonization of volcanic lava outcrops has now been recognized. In this paper, we build upon earlier Raman spectroscopic studies on extremophilic colonies in old lava flows to assess the potential of finding evidence of biological colonization in more recent lava deposits that would inform, first, the new colonization of these rocks and also provide evidence for the relict presence of biological colonies that existed before the volcanism occurred and were engulfed by the lava. In this research, samples were collected from a recent expedition to the active volcano at Kilauea, Hawaii, which comprises very recent lava flows, active fumaroles and volcanic rocks that had broken through to the ocean and had engulfed a coral reef. The Raman spectra indicated that biological and geobiological signatures could be identified in the presence of geological matrices, which is encouraging for the planned exploration of Mars, where it is believed that there is evidence of an active volcanism that perhaps could have preserved traces of biological activity that once existed on the planet’s surface, especially in sites near the old Martian oceans.

The Xiong’er volcanic rocks constitute a large Paleo-Mesoproterozoic volcanic belt along the southern margin of the North China Craton. The volcanic rocks can be petrographically and geochemically classified into the basaltic andesite–andesite and dacite-rhyolite series, with the former being the dominant component of the Xiong’er volcanic rocks. The volcanic rocks of the dacite-rhyolite series have been derived from the wet and low-temperature differentiation of the basaltic andesite–andesite series at shallow depth, suggested by regional geological, lithological, and geochemical studies. In addition, crustal assimilation was involved in the magmas to form volcanic rocks of the dacite-rhyolite series, as suggested by low ϵNd(t) values (−8.09 to ∼−9.99) and high Th/Yb ratios (1.7–2.7). Some of volcanic rocks from the basaltic andesite–andesite series show features of high-Mg andesites (HMA), being characterized by high MgO contents and Mg numbers, representing the most primitive end-member of the...

Short-term channel dynamics of mountain stream reaches in the southern North Island of New Zealand were assessed over two successive 3-month periods using morphological budgeting. Response to floods varies between reaches, even\ud when the catchments were located close to each other and had similar characteristics. The reaches on the Central Volcanic Plateau experienced least morphological change, while streams with steep catchments and migrating planform in the Tararua and Ruahine Ranges showed frequent channel adjustments. Channel response is conditioned by intrinsic variables rendering reaches responsive or robust to the effects of floods, and this is likely to reflect the degree of connectivity between slopes and channels, and reaches.

This paper provides new accelerator mass spectrometry (AMS) radiocarbon age data for the last volcanic events in the Carpathian-Pannonian region of eastern-central Europe. The eruption ages were determined on charcoal fragments collected from pumiceous pyroclastic flow deposits at 2 localities of the Ciomadul Volcano. Two charcoal samples from the southeastern margin of the volcano (Bixad locality) set the date of the last volcanic eruption to 27,200 ± 260 yr BP (29,500 ± 260 cal BC). On the other hand, our data show that the Tusnad pyroclastic flow deposit, previously considered as representing the youngest volcanic rock of the region, erupted at ∼39,000 yr BP (∼41,300 cal BC). Thus, a period of dormancy more than 10,000 yr long might have elapsed between the 2 volcanic events. The different ages of the Tusnad and Bixad pyroclastic flow deposits are confirmed also by the geochemical data. The bulk pumices, groundmass glass, and the composition of the main mineral phases (plagioclase and amphibole) suggest eruption of slightly different magmas. Considering also the assumed long volcanic history (∼600 ka) of the Ciomadul, these data suggest that further detailed studies are necessary on this seemingly inactive volcano in order to evaluate the possible renewal of volcanic activity in the future.