Volcaniclastic Material Research Articles

Sediment provenance and dispersal of Neogene–Quaternary strata of the southeastern San Joaquin Basin and its transition into the southern Sierra Nevada, California

We have studied detrital-zircon U-Pb age spectra and conglomerate clast populations from Neogene–Quaternary siliciclastic and volcaniclastic strata of the southeastern San Joaquin Basin, as well as a fault-controlled Neogene basin that formed across the southernmost Sierra Nevada; we call this basin the Walker graben. The age spectra of the detrital-zircon populations are compared to a large basement zircon age data set that is organized into age populations based on major drainage basin geometry of the southern Sierra Nevada and adjacent ranges. We find a direct sediment provenance and dispersal link for much of the Neogene between the Walker graben and the southeastern San Joaquin Basin. In early to middle Miocene time, this link was accented by the delivery of volcaniclastic materials into the southeastern Basin margin from the Cache Peak volcanic center that was nested within the Walker graben. In late middle Miocene through early Pleistocene time, this linkage was maintained by a major fluvial system that we call the Caliente River, whose lower trunk was structurally controlled by growth faults along the Edison graben, which breached the western wall of the Walker graben. The Caliente River redistributed into the southeastern San Joaquin Basin much of the ∼2 km of volcaniclastic and siliciclastic strata that filled the Walker graben. This sediment redistribution was forced by a regional topographic gradient that developed in response to uplift along the eastern Sierra escarpment system. The Caliente River built a fluvial-deltaic fan system that prograded northwestward across the lower trunk of the Kern River and thereby deflected the Kern drainage flux of sediment into the Basin edge northward. In mainly late Miocene time, turbidites generated primarily off the Caliente River delta front built the Stevens submarine fan system of the southeastern and central areas of the San Joaquin Basin. In late Quaternary time, 1–1.8 km of Caliente River–built strata were eroded as an epeirogenic uplift that we call the Kern arch emerged along the southeastern Basin margin, in response to underlying mantle lithosphere removal. The sediment that was eroded off the arch was redistributed mainly into the Maricopa and Tulare sub-basins that are located to the southwest and northwest, respectively, of the arch.

Geochemical investigation of Neogene volcaniclastic rocks from the south-eastern part of the Zărand Basin (Apuseni Mts., Romania) – implications for locating the source area

A geochemical study of the Neogene volcaniclastic deposits from the south-eastern part of the Zărand Basin (Apuseni Mts., Romania) was performed. The investigated rocks are represented by medium-K calc-alkaline andesites. Their geochemical features are similar with those of other Neogene volcanic rocks from the Apuseni Mts. However, the investigated rocks also display a few particularities: limited variation of some major oxides and trace elements content, much lower content of Nb or of light REE. As for the other Neogene volcanic rocks from Apuseni area, the geochemical evidence supports a magma source located close to the boundary between crust and garnet-free lithospheric mantle, minor fractional crystallization processes affecting the magma. A subduction signature was identified for the investigated samples, and, similar to other Neogene volcanic rocks from Apuseni Mts., was interpreted as being related to some enrichment in fluids of the magma source. Based on the location and geochemical similarities with those of other Neogene volcanic rocks from the Apuseni Mts, the assumed age range of volcanic activity generating the volcaniclastic rocks of the study area is 13.8-10 Ma, while the source of the volcaniclastic material is most probably the Bontău volcanic structure.

Basin filling related to the Philippine Sea Plate motion in Beppu Bay, southwest Japan

Strike-slip basins are one of the most important accumulation spaces for sediment of terrigenous, biogenic, and volcanic origins, and generally include large amount of event deposits. Although these event deposits are important basin filling process, research on this topic, particularly the effects of event deposits, is insufficient. In this study, we discuss sedimentation features based on grain composition and other properties for ca. 3000year periods in Beppu Bay, which is strike-slip basin located at the western end of an arc-bisecting dextral fault known as Median Tectonic Line (MTL) associated with the northwestward subduction of the Philippine Sea Plate. This sediment is composed of hemipelagic clay and coarser event layers of turbidites referred to as types A, B, and C; ash layers referred to as type D; and other referred to as type E. The turbidite event layers, which accounted for 92% of the total major event layer, with >1cm thickness, consist of particles related to volcanism, including hydrothermal activity. The events control the regional filling rate and transportation of coarse and heavy volcaniclastic materials. In particular, type A, which accounted for 73% of the total major event layer thickness, is likely induced by earthquakes related to the MTL, according to its age. As a result, the basin filling processes are controlled mainly by tectonics related to the subduction of the Philippine Sea Plate.

Palaeoenvironmental reconstruction of Livingston Island, Antarctic Peninsula, in the Early Cretaceous: interpretations from the Walker Bay erratics

Chen, K., Stilwell, J.D. & Mays, C., 12.3.2015. Palaeoenvironmental reconstruction of Livingston Island, Antarctic Peninsula in the Early Cretaceous: interpretations from the Walker Bay erratics. Alcheringa 39, 000–000. ISSN 0311-551Fossiliferous, volcaniclastic sandstone erratics, containing abundant plant fragments, palynomorphs and a possible insect wing, were extracted from the previously unstudied Walker Bay moraine, Livingston Island (ca 62°36ʹS, 60°42ʹW). These samples provide new insights into high southern latitude ecosystems of the South Shetland Islands region during the Early Cretaceous greenhouse interval. The palynofloral assemblage, in particular the co-occurrence of Ischyosporites punctatus, Concavissimisporites penolaensis and Reticulatisporites pudens, suggests that deposition could have occurred between the early Aptian and mid-Albian (ca 125–109 Ma), but was most likely early to mid-Albian (ca 112–109 Ma). The high relative abundance of the pteridophyte taxon, Cyathidites and associated fungal disaster taxa, together with significant quantities of volcaniclastic material, indicates a volcanically perturbed post-eruption riparian environment. Petrologic evidence suggests that the volcanic sediments were deposited rapidly in the above-mentioned fluvial setting. Comparisons to geological studies conducted on Livingston Island reveal an affinity of the Walker Bay erratics to the Byers Group; the unique palynofloral assemblage and petrological features of the erratics suggesting that the volcanogenic lithic sandstone facies may represent a previously undescribed unit of the upper Cerro Negro Formation.Kevin Chen [kevin.chen@monash.edu], Jeffrey D. Stilwell* [jeffrey.stilwell@monash.edu] & Chris Mays [chris.mays@monash.edu], School of Earth, Atmosphere and Environment, Faculty of Science, Monash University, Vic 3800, Australia. *Also affiliated with Australian Museum, 6 College Street, Sydney, NSW 2000, Australia.

High‐resolution magnetics reveal the deep structure of a volcanic‐arc‐related basalt‐hosted hydrothermal site (Palinuro, Tyrrhenian Sea)

AbstractHigh‐resolution magnetic surveys have been acquired over the partially sedimented Palinuro massive sulfide deposits in the Aeolian volcanic arc, Tyrrhenian Sea. Surveys flown close to the seafloor using an autonomous underwater vehicle (AUV) show that the volcanic‐arc‐related basalt‐hosted hydrothermal site is associated with zones of lower magnetization. This observation reflects the alteration of basalt affected by hydrothermal circulation and/or the progressive accumulation of a nonmagnetic deposit made of hydrothermal and volcaniclastic material and/or a thermal demagnetization of titanomagnetite due to the upwelling of hot fluids. To discriminate among these inferences, estimate the shape of the nonmagnetic deposit and the characteristics of the underlying altered area—the stockwork—we use high‐resolution vector magnetic data acquired by the AUV Abyss (GEOMAR) above a crater‐shaped depression hosting a weakly active hydrothermal site. Our study unveils a relatively small nonmagnetic deposit accumulated at the bottom of the depression and locked between the surrounding volcanic cones. Thermal demagnetization is unlikely but the stockwork extends beyond the limits of the nonmagnetic deposit, forming lobe‐shaped zones believed to be a consequence of older volcanic episodes having contributed in generating the cones.

Provenance of the Eocene sandstones in the southern Chindwin Basin, Myanmar: Implications for the unroofing history of the Cretaceous–Eocene magmatic arc

The Eocene sedimentary rocks, exposed in the southern Chindwin Basin, northern part of Myanmar, are characterized by a thick sequence of continental clastic units consisting of sandstones with abundant volcaniclastic materials, and a subordinate amount of metamorphic lithic fragments. Detrital information preserved in these Eocene clastic sequences has shed light on the erosional unroofing history of a Cretaceous to Eocene Andean-type continental magmatic arc related to the India–Asia collision.An integrated study of the petrography, geochemistry and LA-ICP-MS (Laser Ablation Inductively Couple Plasma Mass Spectrometer) U–Pb zircon geochronology of the late Middle Eocene, volcaniclastic Pondaung sandstones, combined with the WSW-directed regional mean palaeocurrent direction (∼254° azimuth), has revealed an older, calc-alkaline, andesitic volcanic arc (detrital U–Pb zircon age: 101–43Ma), situated to the NE of the southern Chindwin Basin, possibly related to the Neo-Tethys seafloor subduction beneath the Eurasia continental margin, i.e., the West Burma Block or Burma (Myanmar) Plate. We suggest that this arc may have been eroded during the late Middle Eocene (Bartonian) with volcaniclastic detritus deposited in the fore-arc basin of the Central Myanmar Basin, forming the Pondaung Formation.

The eastern flank of the Merapi volcano (Central Java, Indonesia): Architecture and implications of volcaniclastic deposits

Merapi volcano in central Java Island is considered to be the most active and dangerous andesitic volcano in Indonesia. The volcanic history of Merapi volcano is complex, and often perturbed by frequent episodes of eruptive edifice building and subsequent erosion and collapse. In this paper, we present a detailed field, literature, and GIS-study of the well-preserved eastern flank of Merapi, which has been spared from major eruptions, in order to reconstruct the geologic and geomorphic history of the edifice. Here, the most recent deposits arise from the remobilization of the old volcanic materials by lahar, gravitational collapse of massive lava flow and local landslide processes.In this study, we describe the specific deposits and subsequent alteration and removal processes. The stratigraphic analysis was performed with respect to the distinct phases of construction due to eruptions and dismantling of the volcano by erosion, gravitational collapse and the associated local to distal re-sedimentation. Based on GIS analysis and field surveys, a drainage network anomaly was detected in two main rivers, the Soka and the Brambang Rivers. We infer that an apex fan of volcaniclastic material was deposited into a central paleo-Pusur river and explains the abnormal divergence of the rivers. A new lithological 3D conceptual model is proposed based on the characterization of the lithological facies and their temporal and spatial evolution along the eastern flank of Merapi volcano.

Paleoenvironmental reconstruction of the coastal Monte Léon and Santa Cruz formations (Early Miocene) at Rincón del Buque, Southern Patagonia: A revisited locality

Sedimentological, ichnological and paleontological analyses of the Early Miocene uppermost Monte León Formation and the lower part of the Santa Cruz Formation were carried out in Rincón del Buque (RDB), a fossiliferous locality north of Río Coyle in Santa Cruz Province, Patagonia, Argentina. This locality is of special importance because it contains the basal contact between the Monte Léon (MLF) and the Santa Cruz (SCF) formations and because it preserves a rich fossil assemblage of marine invertebrates and marine trace fossils, and terrestrial vertebrates and plants, which has not been extensively studied. A ∼90 m-thick section of the MLF and the SCF that crops out at RDB was selected for this study. Eleven facies associations (FA) are described, which are, from base to top: subtidal–intertidal deposits with Crassotrea orbignyi and bioturbation of the Skolithos-Cruziana ichnofacies (FA1); tidal creek deposits with terrestrial fossil mammals and Ophiomorpha isp. burrows (FA2); tidal flat deposits with Glossifungites ichnofacies (FA3); deposits of tidal channels (FA4) and tidal sand flats (FA5) both with and impoverish Skolithos ichnofacies associated; marsh deposits (FA6); tidal point bar deposits recording a depauperate mixture of both the Skolithos and Cruziana ichnofacies (FA7); fluvial channel deposits (FA8); fluvial point bar deposits (FA9); floodplain deposits (FA10); and pyroclastic and volcaniclastic deposits of the floodplain where terrestrial fossil mammal remains occur (FA11).The transition of the MLF–SCF at RDB reflects a changing depositional environment from the outer part of an estuary (FA1) through the central (FA2–6) to inner part of a tide-dominated estuary (FA7). Finally a fluvial system occurs with single channels of relatively low energy and low sinuosity enclosed by a broad, low-energy floodplain dominated by partially edaphized ash-fall, sheet-flood, and overbank deposits (FA8–11). Pyroclastic and volcaniclastic materials throughout the succession must have been deposited as ash-fall distal facies in a fluvial setting and also were carried by fluvial streams and redeposited in both estuarine and fluvial settings. These materials preserve most of the analyzed terrestrial fossil mammals that characterize the Santacrucian age of the RDB's succession. Episodic sedimentation under volcanic influence, high sedimentation rates and a relatively warm and seasonal climate are inferred for the MLF and SCF section.Lateral continuity of the marker horizons at RDB serve for correlation with other coastal localities such as the lower part of the coastal SCF south of Río Coyle (∼17.6–17.4 Ma) belonging to the Estancia La Costa Member of the SCF.

Late Oligocene–early Miocene landscape evolution of the Lake Mead region during the transition from Sevier contraction to Basin and Range extension

Late Oligocene to Miocene sedimentary strata of the Lake Mead, Nevada, region hold evidence that can test models of central Basin and Range extension and tectonic evolution and illuminate paleodrainage systems related to the carving of the Grand Canyon. In this region, Sevier contraction and a period of relative tectonic quiescence predate Miocene extension and magmatism. The herein revised Rainbow Gardens Formation, formerly the oldest member of the Horse Spring Formation, is found throughout the Lake Mead area and spans the transition from quiescence to the start of extension. New detailed stratigraphic work within the Rainbow Gardens Formation, including paleocurrent analyses, stable isotope geochemical data, new 40 Ar/ 39 Ar dates, tephrochronologic data, and ongoing structural studies, was used to build a detailed chronostratigraphic framework and reconstruct the Rainbow Gardens basin through time. Our results show that the basin formed by a combination of inherited topography and tectonic events outside the Lake Mead region prior to ca. 25 Ma. Sedimentation rates, sedimentary facies patterns, and the lack of evidence for syndepositional faulting indicate that the basin did not form during extensional faulting, although recent work suggests that this basin was modified by uplift to the south between 18 and 20 Ma. Initially, the basin recorded fluvial sedimentation within the center of an E-NE–trending inherited valley, with two facing gravel-dominated bajadas on either side. As the valley filled, rivers from the Caliente volcanic field to the north delivered an influx of volcaniclastic material into a broad area of marshes and ephemeral lakes. In the final stages of sedimentation, just prior to the onset of extension at ca. 17 Ma, the basin filled with limestone in a series of shallow lakes. Understanding the development and evolution of this basin is crucial for testing models of extension as recorded by the younger Horse Spring Formation. In addition, the detailed sedimentology and stratigraphy place constraints on models of the formation of the Grand Canyon and suggest that a paleo–Colorado River did not deposit sediment in the Lake Mead area between 25 and 17 Ma. This work highlights the importance of detailed basin analyses, which are crucial companions to structural, tectonic, and geomorphologic studies aimed at understanding the complex evolution of lithospheric and landscape changes across a large region.

An improved quantitative measure of the tendency for volcanic ash plumes to form in water: implications for the deposition of marine ash beds

Laboratory experiments and numerical simulations have shown that volcanic ash particles immersed in water can either settle slowly and individually, or rapidly and collectively as particle-laden plumes. The ratio of timescales for individual and collective settling, in the form of analytical expressions, provides a dimensionless quantitative measure of the tendency for such plumes to grow and persist which has important implications for determining particle residence times and deposition rates. However, existing measures in the literature assume that collective settling obeys Stokes' law and is therefore controlled by the balance between gravitational forces and viscous drag, despite plume development actually being controlled by the balance between gravitational forces and inertial drag even in the absence of turbulence during early times. This paper presents a new measure for plume onset which takes into account the inertial drag-controlled (rather than viscous drag-controlled) nature of plume growth and descent. A parameter study comprising a set of numerical simulations of small-scale volcanic ash particle settling experiments highlights the effectiveness of the new measure and, by comparison with an existing measure in the literature, also demonstrates that the timescale of collective settling is grossly under-estimated when assuming that plume development is slowed by viscous drag. Furthermore, the formulation of the new measure means that the tendency for plumes to form can be estimated from the thickness and concentration of the final deposit; the magnitude and duration of particle flux across the water's surface do not need to be known. The measure therefore permits the residence times of particles in a large body of water to be more accurately and practically determined, and allows the improved interpretation of layers of volcaniclastic material deposited at the seabed.

Peperites in the Permian Tarim large igneous province in Northwest China and their constraints on the local eruption environments

Peperites are special kinds of volcaniclastic materials generated by mingling of magma and unconsolidated sediments. They directly demonstrate the contemporaneity of volcanism and sedimentation, and hence they can be used to constrain the local paleoenvironments during volcanic eruptions. We identified peperites in the lower sequence of the northwest outcrops (Inggan-Kalpin area) of Permian Tarim large igneous province (TLIP), Northwest China. In Inggan, blocky peperites were observed at the base of lava flows generated in the second eruption phase. This kind of peperites is generated by quenching of magma in a brittle fragmentation mechanism. While in Kalpin, both the second and the fourth eruption phases preserved peperites in the base of lava flows. Not only blocky but also fluidal peperites can be observed in Kalpin. The fluidal peperites were generated in vapor films, which insulated the magmas from cold sediments and avoided direct thermal shock, and therefore kept the fluidal forms of magma. All of these peperites are hosted by submarine carbonates. In lava sequences generated in the same eruption phases but located in Kaipaizileike, ∼15 km east to Inggan, terrestrial flood basalts developed while peperites are absent, implying a paleoenvironmental transition between Kaipaizileike and Inggan-Kalpin area. Gathering information from observed peperites, TLIP lava flows, and the Lower Permian sedimentary strata, we precisely constrained the spatial distribution and temporal evolution of sedimentary facies of the early stage of TLIP. As a result, two marine transgressions were identified. The first transgression occurred contemporaneous with the second eruption phase. The transition from submarine to subaerial is located between Kaipaizileike and Inggan. The second transgression occurred contemporaneous with the forth eruption phase, and the transition from submarine to subaerial occurred between Inggan and Kalpin.

Neogene tectonostratigraphic history of the southern Neuquén basin (39°–40°30′S, Argentina): implications for foreland basin evolution

AbstractAlthough the Neuquén basin in Argentina forms a key transitional domain between the south‐central Andes and the Patagonian Andes, its Cenozoic history is poorly documented. We focus on the sedimentologic and tectonic evolution of the southern part of this basin, at 39–40°30′S, based on study of 14 sedimentary sections. We provide evidence that this basin underwent alternating erosion and deposition of reworked volcaniclastic material in continental and fluvial settings during the Neogene. In particular, basement uplift of the Sañico Massif, due to Late Miocene–Pliocene intensification of tectonic activity, led to sediment partitioning in the basin. During this interval, sedimentation was restricted to the internal domain and the Collon Cura basin evolved towards an endorheic intermontane basin. From stratigraphic interpretation, this basin remained isolated 7–11 Myr. Nevertheless, ephemeral gateways seem to have existed, because we observe a thin succession downstream of the Sañico Massif contemporaneous with the Collon Cura basin‐fill sequence. Comparisons of stratigraphic, paleoenvironmental and tectonic features of the southern Neuquén basin with other foreland basins of South America allow us to classify it as a broken foreland with the development of an intermontane basin from Late Miocene to Late Pliocene. This implies a thick‐skinned structural style for this basin, with reactivation of basement faults responsible for exhumation of the Sañico Massif. Comparison of several broken forelands of South America allows us to propose two categories of intermontane basins according to their structural setting: subsiding or uplifted basins, which has strong implications on their excavation histories.

Factors controlling the geochemical composition of Limnopolar Lake sediments (Byers Peninsula, Livingston Island, South Shetland Island, Antarctica) during the last ca. 1600 years

Abstract. We sampled a short (57 cm) sediment core in Limnopolar Lake (Byers Peninsula, Livingston Island, South Shetland Islands), which spans the last ca. 1600 years. The core was sectioned at high resolution and analyzed for elemental and mineralogical composition, and scanning electron microscope and energy dispersive X-ray spectrometer (SEM-EDS) analysis of glass mineral particles in selected samples. The chemical record was characterized by a contrasted pattern of layers with high Ca, Ti, Zr, and Sr concentrations and layers with higher concentrations of K and Rb. The former were also enriched in plagioclase and, occasionally, in zeolites, while the latter were relatively enriched in 2 : 1 phyllosilicates and quartz. This was interpreted as reflecting the abundance of volcaniclastic material (Ca rich) versus Jurassic–Lower Cretaceous marine sediments (K rich) – the dominant geological material in the lake catchment. SEM-EDS analysis revealed the presence of abundant volcanic shards in the Ca-rich layers, pointing to tephras most probably related to the activity of Deception Island volcano (located 30 km to the SE). The ages of four main peaks of volcanic-rich material (AD ca. 1840–1860 for L1, AD ca. 1570–1650 for L2, AD ca. 1450–1470 for L3, and AD ca. 1300 for L4) matched reasonably well the age of tephra layers (AP1 to AP3) previously identified in lakes of Byers Peninsula. Some of the analyzed metals (Fe, Mn, Cu, and Cr) showed enrichments in the most recent tephra layer (L1), suggesting relative changes in the composition of the tephras as found in previous investigations. No evidence of significant human impact on the cycles of most trace metals (Cu, Zn, Pb) was found, probably due to the remote location of Livingston Island and the modest research infrastructures; local contamination was found by other researchers in soils, waters and marine sediments on areas with large, permanent research stations. Chromium is the only metal showing a steady enrichment in the last 200 years, but this cannot be directly attributed to anthropogenic pollution since recent research supports the interpretation that climatic variability (reduced moisture content and increased wind intensity) may have resulted in enhanced fluxes of mineral dust and trace elements (Cr among them) to Antarctica. At the same time, some features of the chemical record suggest that climate may have also played a role in the cycling of the elements, but further research is needed to identify the underlying mechanisms.

Soils of temperate rainforests of the North American Pacific Coast

Temperate rainforests have high conservation and natural resource value, but the soils of this bioregion have not previously been studied as a unit. Here we examine the soils of North America's Pacific coastal temperate rainforests, utilizing databases from the United States Natural Resources Conservation Service and the Canadian Centre for Land and Biological Resources Research to (i) identify the soil taxa, (ii) evaluate the soil properties, and (iii) compare soils in temperate and tropical rainforests. There are strong climate gradients within these temperate rainforests, with the mean temperature declining from 11.7°C to 6.1°C and the mean annual precipitation increasing from 1500mm to around 3000mm from northern California (CA) to northwestern British Columbia (BC) and southeastern Alaska (AK). There is also high pedodiversity in this region, with soils representing 8 orders and 31 suborders, and, in the US portion, 65 great-groups, 142 subgroups, and 482 soil series. Twenty-six percent of described soil series are endemic to temperate rainforests in the US portion of the region, with the proportion declining with latitude. Dominant soil suborders vary along the latitudinal gradient from Humults–Udalfs/Ustalfs–Udepts–Udults in CA, to Udands–Udepts–Udands Humults in western Oregon (OR) and Washington (WA), to Orthods–Folists in BC and Cryods–Saprists in AK. The dominant diagnostic horizons are ochric/argillic (CA), umbric/cambic (OR, WA), and albic–histic/spodic (BC, AK). Whereas soils in CA, BC, and AK tend to have a mixed mineralogy, those in northern OR and WA commonly are derived from volcaniclastic materials and have a ferrihydritic or isotic mineralogy. Soils in this region are generally deep, hold abundant moisture, are not subject to deep-freezing, and are enriched in extractable Fe and Al. Organic C and total N contents are high overall, but also variable, with right-skewed distributions. Compared to tropical rainforest soils in the Pacific Basin, Pacific temperate rainforest have greater weatherable minerals, cation-exchange capacities, soil organic C, and total exchangeable base cations. However, soils of both bioregions tend to be deep, acidic Al-saturated, and can have large N reservoirs. This investigation provides a foundation for a more unified understanding of the soils of a globally significant bioregion.

Digital photogrammetry and GIS-based analysis of the bio-geomorphological evolution of Sakurajima Volcano, diachronic analysis from 1947 to 2006

The Sakurajima Volcano is one of the most active volcanoes in the world with regular activity dominated by vulcanian eruptions since 1955. Located in Kagoshima Prefecture – Kyushu Island, Japan – the Sakurajima Volcano is a stratovolcano with two main vents at the summit, the Kitadake and the Minamidake, and a third smaller central vent, the Nakadake. The two firsts peak at 1117 and 1060m dominate the slopes mainly composed of lava-flow deposits, secondary volcaniclastic material and recent ejectas from the Vulcanian eruptions. Although the volcano has been very closely monitored by Japanese Universities (mostly Kyoto University and Kagoshima University) and governmental agencies, there has been very little geomorphological investigation of the structure of the volcano. Using the digital photogammetric method SfM–MVS (Structure from Motion and Multiple-view Stereophotogrammetry) applied to historical aerial photographs, the present contribution aims to provide an analysis of the volcanic structure and the recent bio-geomorphological evolution for the period 1947–2006. First, the results have proved that SfM–MVS is a method that can be successfully applied to aerial photographs for diachronic reconstruction of geomorphological landscape evolution. This method is especially important in active volcanic areas, as the geomorphology can change very rapidly within the historical period. Secondly, the results have shown that during the last ~60years, the summit area of the Sakurajima has greatly evolved: the morpholology of the Minamidake crater has changed due to its regular explosive activity; the upper slopes have been covered in ejecta, modifying their elevation and their smoothness. The lower slopes have seen the apparition of lahar deposition areas, while valleys, upslope, have widened due to the lahar activity and the upward progression of the deposits. The 3D derived from SfM–MVS has also shown how the lahar deposits are using the topographic low, created on top of the lava deposits and in between lava deposit to accumulate mid-slopes, rather than accumulating on the lower volcanic apron. This is accentuated by the construction of SABO dams that keep a large amount of the material on the slopes. Finally, as this publication has been carried out using the freely available imagery from the GSI (Geospatial Information Authority of Japan) at 200dpi, higher resolution imagery can even open further possibilities for the monitoring of volcano evolution in Japan and in countries providing long series of historical imagery.

Lithospheric flexure and volcano basal boundary conditions: keys to the structural evolution of large volcanic edifices on the terrestrial planets

Abstract Large volcanic edifices constitute enormous loads at the surfaces of planets. The lithosphere, the mechanically strong outer layer of a planet, responds to growing edifice loads by flexing. The shape of this lithospheric flexure and the resulting stress state exert critical influences on the structure of the evolving edifices, which in turn feed back into the flexural response. Flexural subsidence of the lithosphere forms topographical moats surrounding volcanoes that are partially to completely filled by landslide debris, volcaniclastic materials and sediments, or by relatively flat aprons of volcanic flows. Flexure creates a characteristic ‘dipole’ state of stress that influences subsequent magma ascent paths and chamber dynamics in the lithosphere. Compression in the upper lithosphere can inhibit magma ascent and favour the development of oblate magma chambers or sill complexes. This compression can be transferred into the edifice unless a décollement allows the volcano base to slip over the underlying lithosphere; generally, basal décollements are found to operate via high pore-fluid pressure in a clay sediment-based layer. Volcanoes lacking such a layer, regardless of the thickness of the basal sediments, lack basal décollements and, thus, tend to be limited in size by compressive stresses adverse to magma ascent.

Paleosol diversity in the Olduvai Basin, Tanzania: Effects of geomorphology, parent material, depositional environment, and groundwater on soil development

Olduvai Gorge, Tanzania is known for its fossil and cultural record of early hominins. The archaeological records are typically found within pedogenically modified sediments, thus the interpretation of paleosols provides important paleoenvironmental context information. The Gorge contains a rich and diverse record of paleosols that vary spatially and temporally, however the stratigraphy can be divided into time slices using dated tuffs and studied in a paleolandscape context. Sediments were deposited in a semi-arid closed rift basin containing paleo Lake Olduvai, with volcanoes supplying volcaniclastic material to an alluvial fan system on the eastern side and quartzofeldspathic fluvial sediments derived from weathered basement rocks on the western side. The shallow saline-alkaline lake in the basin center and groundwater levels in the surrounding uplands fluctuated with Milankovitch-driven climatic (precession) cycles of ∼20,000 years. The rift basin paleolandscape (at ∼1.8 Ma) is reconstructed using sedimentology, stratigraphy and paleopedology. Standard field descriptions of physical and biogenic paleosol structures are combined with stable isotope ratios of carbonates, and whole rock geochemistry of sediments, to reveal diversity of paleosols within the basin. There are at least three distinct types of paleosols that record a paleocatena related to both landscape and drainage differences. Red tephra-rich Andisols developed on the volcaniclastic alluvial fan to the east of the paleolake, calcium-carbonate-rich, silty Aridisols developed on the interfluves and floodplain of the fluvial plain on the west, whereas clay-rich paleosols (Vertisols) developed on the lake margin and lake in the center of basin. Variances in geomorphology, depositional environment, parent material, and depth to the water table are reflected in the development of distinctly different soil types that can provide key data needed for high-resolution reconstruction of the landscape known to be utilized by early hominins.

1P1-H03 無人電動マルチロータ機搭載型土砂採取機構の開発(サーチ&レスキューロボット・メカトロニクス(1))

When an active volcano erupts, typically, a restricted area is set around the crater for safety. However, it is important to observe inside of the restricted area for a forecast of disasters, such as debris flow. There arc some proposals of visual observation methods in restricted areas, e.g. a tele-operated mobile ground robot with cameras. However, there is no sample-return method for obtaining volcaniclastic materials from such restricted areas. Therefore, in this research, we developed two sample-return devices that hang down from multi-rotor UAV. In this paper, we introduce our developed devices, and report indoor and outdoor experiments.

Influence of successive phases of volcanic construction and erosion on Mayotte Island's hydrogeological functioning as determined from a helicopter-borne resistivity survey correlated with borehole geological and permeability data

Summary The purpose of this study is to show how a multidisciplinary approach that combines geophysics, geology and hydrogeology has made it possible to: (a) significantly improve our understanding of the hydrogeological regime of the volcanic island of Mayotte, and (b) provide a new set of geophysical measurement calibration data. In 2010 a helicopter-borne geophysical survey (SkyTEM) was flown over the entire island (374 km2) with a measurement density hitherto unheard of in a volcanic environment. In addition, a database was compiled containing the geological logs of 55 boreholes. 52 of these boreholes have hydrogeological information like aquifer position and piezometric level. 21 of the boreholes have transmissivity values. Correlations were made between the inverted resistivities as obtained from the helicopter-borne TDEM profiles and the nature, age and hydrodynamic properties of the formations as obtained from the borehole data. Five hydrogeological units were mapped. These are characterized by an alternation between phases of dominant volcanic construction, with the emplacement of basaltic lavas, phonolite massifs and pyroclastic deposits, and phases of dominant erosion with the deposition of volcaniclastic material (colluvium, breccias, basaltic lavas and phonolite blocks and all materials resulting from slope slides) along the slopes and in the topographic depressions. It has also been possible to assign resistivity and permeability ranges to four of these units. Ranges that are also dependent on the age of the deposits: the younger the formation is, the greater its resistivity and the higher its permeability. The hydrogeological regime is marked by the phases of volcanic construction and erosion that succeeded one another during the geological history of Mayotte over the last 10 Ma. A conceptual model adapted to the specific geological context of this island, and differing from the Canarian and Hawaiian models, is also put forward. This model is marked by the island’s “fragmented” character resulting from its geological history (several volcanic edifices, several phases of construction and erosion), and is applicable to an old volcanic island in an advanced stage of erosion and weathering, with a volcanic history similar to that of Mayotte, i.e. with climate variations and erosion periods long enough to register volcaniclastic deposits.

CHERTS OF THE BARBERTON GREENSTONE BELT, SOUTH AFRICA: PETROLOGY AND TRACE-ELEMENT GEOCHEMISTRY OF 3.5 TO 3.3 GA OLD SILICIFIED VOLCANICLASTIC SEDIMENTS

Research Article| December 01, 2013 CHERTS OF THE BARBERTON GREENSTONE BELT, SOUTH AFRICA: PETROLOGY AND TRACE-ELEMENT GEOCHEMISTRY OF 3.5 TO 3.3 GA OLD SILICIFIED VOLCANICLASTIC SEDIMENTS A. HOFMANN; A. HOFMANN Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa, e-mail: ahofmann@uj.ac.za Search for other works by this author on: GSW Google Scholar R. BOLHAR; R. BOLHAR Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa School of Earth Sciences, University of Queensland, Brisbane, Qld 4072, Australia, e-mail: rbolhar71@gmail.com Search for other works by this author on: GSW Google Scholar B. ORBERGER; B. ORBERGER ERAMET, 1 Avenue Albert Einstein, 78190 Trappes, France, Université Paris Sud XI, UMR IDES 8148, Département des Sciences de la Terre, Bât 504-509, 91405 Orsay Cedex, France, e-mail: beate.orberger@erametgroup.com Search for other works by this author on: GSW Google Scholar F. FOUCHER F. FOUCHER Centre de Biophysique Moléculaire, CNRS, Rue Charles Sadron, 45071 Orléans, France, e-mail: frederic.foucher@cnrs-orleans.fr Search for other works by this author on: GSW Google Scholar South African Journal of Geology (2013) 116 (2): 297–322. https://doi.org/10.2113/gssajg.116.2.297 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation A. HOFMANN, R. BOLHAR, B. ORBERGER, F. FOUCHER; CHERTS OF THE BARBERTON GREENSTONE BELT, SOUTH AFRICA: PETROLOGY AND TRACE-ELEMENT GEOCHEMISTRY OF 3.5 TO 3.3 GA OLD SILICIFIED VOLCANICLASTIC SEDIMENTS. South African Journal of Geology 2013;; 116 (2): 297–322. doi: https://doi.org/10.2113/gssajg.116.2.297 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySouth African Journal of Geology Search Advanced Search Abstract A suite of green and carbonaceous black chert interbedded with submarine volcanic rocks from several stratigraphic levels of the Onverwacht Group of the Barberton greenstone belt, from the top of the ~3.48 Ga Komati Formation to the base of the ~3.26 Ga Fig Tree Group have been investigated petrologically and geochemically. Provenance analysis was undertaken using immobile trace element ratios in comparison with potential source rocks from the Barberton granitoid-greenstone terrain. Raman spectroscopy was used to better characterise carbonaceous matter in different chert varieties. Green cherts consist predominantly of silicified mafic to ultramafic volcaniclastic material. Black cherts contain volcaniclastic and/or epiclastic material of ultramafic to felsic composition, admixed with carbonaceous matter. In several cases, the clastic sediment is compositionally distinct to the volcanic substrate, suggesting that it represents volcanic material of relatively distal sources. Soon after settling out of the water column, lithification due to silicification took place. It gave rise to excellent textural preservation, but strongly modified the mineralogical and chemical composition of the seafloor sediments. Zircon, Cr-spinel and rare phosphate minerals are the only primary minerals remaining, while clastic grains have been largely replaced by a fine intergrowth of microquartz, Ti-oxide and K-bearing mica. Chemical changes are similar to those reported previously for silicification of volcanic rocks from the Barberton belt and are consistent with low-temperature hydrothermal processes common to the Palaeoarchaean seafloor environment. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.