Holocene Age Research Articles

THE STUDY OF THE DEBRIS-FLOWS DYNAMICS ON AN EXPERIMENTAL STAND

Designed and manufactured a test stand for the dynamic characteristics of debris-flows and for physical modelling of debris-flows. The stand is a rectangular cross-section tray with a length of 3.0 m, a width of 0.25 m, a depth of 0.25 m. The slopes of the tray vary from 10o to 45o. Rods are installed in the tray to accommodate load cells for measuring pressure, speed and temperature. The process of moving the debris-flow through the transparent wall of the debris-flow tray is filmed by a high-speed video camera. During the experiment, the velocity and high- velocity pressure of water flow and artificial debris-flow were measured. The tray was installed with a slope of 12o. Water flow was started up on the tray (to measure the flow rate and the value of the velocity head, which were then used as reference values). Then the tray was put into the flow of the prepared debris-flow mixture. The debris-flow mixture was prepared from a dredged-crushed proluvial-deluvial deposits of Holocene age with a loamy aggregate with a density of 2210 kg/m3. The density of the prepared debris-flow mixture was 1756 kg/m3. Dynamic viscosity of the debris-flow mass measured by the Stokes method was 0.0498 Poise, kinematic viscosity of the debris-flow mass was 0.0928 Stokes. Data on the debris-flow velocity measured directly during its movement of the debris-flow is not enough. Therefore, methods for calculating the speed of a debris-flow slide in its are important. One of these methods is the method of calculating the debris-flow velocity by the magnitude of the speed head (on the traces of the debris-flow on the trunks of trees). That method is based on the formula of E. Torricelli. The results of the experiment showed that the measured debris-flow velocity, calculated from the magnitude of the velocity head, was lower than the measured velocity before the obstacle and higher than the measured velocity after the obstacle. The measured velocity of the debris-flow passage of the entire tray was close to the calculated one.

An annotated checklist of the fossil birds of Australia

ABSTRACT A complete annotated checklist of all species of birds based on fossil material known as of 2019 from continental Australia is presented. Taxa range from Cretaceous to Holocene in age. It includes synonyms with full bibliographic details and specifics of the type material in all cases, such as specimen or locality data, source local fauna and geological age. Nomina based on fossil material that are now synonymised under extant taxa are also included. The list includes 95 avian species, of which 78 are extinct, in 66 genera. Five extinct subspecies in modern genera are recognised. These species represent 33 family- and 19 ordinal-group taxa, or nearly half of modern avian orders.

Non-invasive prospection techniques and direct push sensing as high-resolution validation tools in wetland geoarchaeology – Artificial water supply at a Carolingian canal in South Germany?

The prospection of (geo-)archaeological sites yield important knowledge about the concept and the utilisation of pre-historical and historical infrastructure. The satisfactory conduction of classical prospection methods like archaeological excavations or geoarchaeological vibra-coring might be challenging in the case of large sites or difficult underground conditions. This is particularly problematic in wetlands featuring a high groundwater table and high compaction rates of organic layers.In this study, we provide an alternative and non- to minimal-invasive exploration approach to discover hydro-engineering structures for artificial water supply in the surrounding of a Carolingian summit canal in South Germany. The Early Medieval Fossa Carolina was intended 792/793 CE to bridge the Central European watershed between Rhine-Main and Danube catchments. As the canal was constructed as a summit canal, an artificial water supply at the highest levels seemed very likely or even obligatory. In order to explore these obligatory hydro-engineering features, we use a wide range of on-site and off-site tools in a spatial hierarchical way. Our approach includes the large-scale SQUID magnetic survey and the sighting of historical maps. Furthermore, we integrate high-resolution direct push colour logs, and subsequent vibra-coring for small-scale stratigraphical verification and sedimentological analyses.The SQUID magnetic survey and related depth models discover two pronounced linear anomalies that might represent potential artificial water inlets in the North-Eastern and Northern Sections of the canal. I) In the North-Eastern Section, direct push colour logs, vibra-coring and 14C dating provide no evidence for a Carolingian hydro-engineering feature but reveal a natural lenticular structure of Early Holocene age. II) The linear magnetic anomaly in the Northern Section can be excluded with high probability as a hydro-engineering structure as well. Here, direct push colour logs, vibra-coring, 14C dating and the comparison with a historic map reveal evidence for a historic gravel road. Thus, we have nicely verified the magnetic information but have no prove for an artificial Carolingian water inlet from the Swabian Rezat River that contradicts with assumptions of former studies.

Intersections between wind regimes, topography and sediment supply: Perspectives from aeolian landforms in Central Asia

The widespread aeolian deposits of the Central Asian steppes and piedmonts offer potential to better understand the dynamics of the major Eurasian climate subsystems over Quaternary timescales. However, current assumptions linking climate processes with aeolian activity remain poorly substantiated and potentially problematic: emerging datasets suggest that loess accumulation rates, and the timing of peak dust flux along the Tien Shan piedmont, are highly variable between sites; the degree to which desert dunes reflect wind regimes and therefore provide records of climate circulation is unknown; and the presumed genetic link between the region's desert dunes and piedmont loess deposits remains hypothetical. These uncertainties raise questions as to the nature of the relationship between aeolian flux, deposition and (palaeo)climate.Here we investigate the relationship between wind regimes and the distribution, morphology and timing of two aeolian landform types (dunes and loess) in the topographically diverse Ili Basin of southeast Kazakhstan and western China. We establish late Holocene ages for three dune sites and one loess profile and infer that the location and morphology of these landforms can be used to test their genetic link with recent wind regimes. We assess the morphologic characteristics of linear dunes at four sites using a semi-automated mapping approach, and analyse the variability in dune orientations with respect to sand-shifting wind trajectories identified from meteorological reanalysis data for each site. The most frequently occurring wind direction appears to be responsible for sediment supply, while the strongest winds drive dune orientation. Wind orientations are strongly influenced by topography. Back trajectories incorporating dust transport and deposition potential to the loess site suggest both westerly and northerly delivery of fine-grained material to the piedmont, and that the most common source areas lie in regions where surface sediment contains a mixture of coarse and fine-grained material to facilitate entrainment into suspension.

A marsupial assemblage (Mammalia, Didelphimorphia) from the Quaternary of the Serra Da Capivara, State of Piauí, Brazil

Didelphimorphia is one of the three extant marsupial orders in South America, and the only one currently found in Brazil. These marsupials have a wide variety of habits and occupy different habitats, making them good indicators of paleoenvironmental conditions. The Serra da Capivara National Park, located in the municipalities of Sao Raimundo Nonato, Coronel Jose Dias, Joao Costa and Brejo do Piaui, in the southeast of the State of Piaui, contains a large number of karstic caves and rock shelters in which hundreds of fossils of Pleistocene mammalian megafauna have been collected, together with small mammal fossils. This study reveals the diversity of didelphids in the Serra da Capivara through the analysis of fragmented maxillae and dentaries found in four paleontological sites: Toca do Serrote das Moendas, Toca do Gordo do Garrincho, Toca do Serrote do Artur and Toca do Barrigudo. The fossils were attributed to six taxa: Monodelphis domestica, Monodelphis americana, Didelphis albiventris, Cryptonanus agricolai, Gracilinanus agilis and Thylamys karimii. They constitute new records for the Quaternary of the Serra da Capivara, except for M. domestica and D. albiventris. Despite the megafauna indicating a Pleistocene age, radiocarbon dating of bioapatite from specimens of small mammals (marsupials and rodents) resulted in Holocene ages (5,550 ± 40 years BP to 1,670 ± 25 years BP), showing temporal mixing in the studied sites. All the taxa described here are currently found in the Caatinga, suggesting stability in the taxonomic composition of the didelphid assemblage, at least since the Middle Holocene.

Optical chronology and climatic implication of glacial advances from the southern Ladakh Range, NW Himalaya, India

Morphological, sedimentological, and chronological evidence suggests the preservation of three glacial advances of decreasing magnitude in the Puche valley (near Leh), southern Ladakh Ranges. The oldest moraine of Puche Glacier Advance-1 (PGA-1) is optically dated to the early Marine Isotopic Stage (MIS)-2 (31.5 ± 3.3 ka) that persisted until around the global Last Glacial Maxima (LGM) (22.7 ± 1.6 ka). The PGA-2 is optically dated to the post LGM (14.4 ± 1.0 ka) and perhaps was triggered by meltwater pulse (1a?) cooling. The youngest PGA-3 remains undated and could be of Holocene age. The Optically Stimulated Luminescence (OSL) ages suggest a greater role of westerlies in driving the glacier advances during the MIS-2 in the southern Ladakh Ranges and are at variance with the previous suggestions that recommended monsoon driven glacier advances. The OSL ages compared to the previously obtained 10Be surface exposure ages are younger by a magnitude. The study explores probable causes for the variance in two chronologies and suggests employing multiple dating methods to minimize the uncertainty both in terms of age and climatic interpretation.

A right whale (Mysticeti, Balaenidae) from the Pleistocene of Taiwan

Current patterns of biological distribution result from the deep past. Of particular interest, some closely related species appear at high latitudes of both hemispheres, but not in between, a pattern known as antitropical distribution. However, the timing, pathway, and drivers of antitropical distributions remain mostly unknown. Here we describe a new fossil, a left tympanic bulla (part of the ear bones), from the Middle/Late Pleistocene (0.78–0.01 mya, but not excluding the possibility of Holocene in age, as the specimen was dredged from the sea bottom and the geological horizon remains uncertain) of Taiwan. The tympanic bulla is diagnostic in baleen whales, and this specimen shows morphological features that are identical to extant Eubalaena, including: relatively large size (the anteroposterior length is 117 mm); rectangular outline in medial view; short anterior lobe, judging from the remaining of the lateral furrow; squared anterior margin; prominent transverse crease on the involucrum; transversely compressed in anterior view; well-developed and rounded outer lip; and parallel involucral and main ridges. Although incomplete, the morphological characters and overall similarity to extant Eubalaena allow a reliable taxonomic assignment to Eubalaena sp. The occurrence of a Pleistocene Eubalaena on the southern margin of the western North Pacific is the first balaenid fossil evidence indicative of the biotic interchange between two hemispheres leading to the origin of antitropical distribution in the Pleistocene; alternatively, this specimen might merely represent an extra-limital record of the North Pacific Eubalaena. Furthermore, this find suggests that the Eubalaena interchange, being one of the largest species displaying antitropical distribution pairs in the history of life, likely took place along the western Pacific. Notably, this does not preclude the Eubalaena interchange from other routes, such as the eastern Pacific or the Atlantic Ocean, and future finds should test the scenario for the biotic interchange between Northern and Southern Hemispheres of Eubalaena.

Geology and Hydrogeology Aspects of El Palmar National Park, Entre Ríos, Argentina

The El Palmar National Park located in the El Palmar Basin (Entre Ríos, Argentina) is a natural reserve of a relictic nature. As a protected area, its importance lies in the population of Yatay palm trees (Butia yatay). This type of palm tree is restricted to the area of the national park and its surroundings and it is uncommon to observe them in other locations on the platense coast. In the area there are outcrops of units of Cretaceous age represented by the Puerto Yeruá formation on which were deposited the clastic sediments of the Salto Chico formation of Plio-Pleistocene age (no outcrops) and the Ubajay formation of Holocene age in net contact. We identified two types of aquifers in the area, one fissured aquifer contained in Puerto Yeruá and two clastic aquifers contained in the Salto Chico and Ubajay formations. The first is of very thin and low permeability and the second of comparable permeability but thicker. The proposed hydrostratigraphic model has allowed us to understand the lateral and vertical variations of the aquifer units involved.

Deep pockmarks as natural sediment traps: a case study from southern Santos Basin (SW Atlantic upper slope)

This study examines the role of deep pockmarks in acting as natural sediment traps. Multibeam bathymetry, single-channel seismic and sediment samples data were used for describing the morphology of pockmarks as well as the nature of sediments inside and outside these depressed features, in an area of Santos Basin (SW Atlantic upper slope), dominated by the strong flow of Brazil Current. Results show that the grain size and chemical composition of sediments inside pockmarks are distinct from the outside. Also, radiocarbon dating shows that Holocene ages are found only in samples located inside the pockmarks. Combination of sedimentological, geochemical and geochronological data allowed to recognise that deep pockmarks might present distinct sediment deposition processes when compared with those of shallow pockmarks, in which turbulence impedes sediment deposition, as reported in the literature.

Linking Holocene vegetation dynamics, palaeoclimate variability and depositional patterns in coastal successions: Insights from the Po Delta plain of northern Italy

Mediterranean deltaic-coastal plains represent relatively underexplored depositional archives that record the Holocene response of vegetation and depositional systems to high-frequency climate changes. In this study, we examine a 25 m-thick succession of Holocene age (core EM2) recovered in the innermost portion of the Po delta plain of northern Italy, applying an integrated palyno-stratigraphic approach. The existence of a paludal, freshwater setting inland of the line of maximum marine transgression favoured a low degree of pollen transportation. Application of cluster analysis to this palynological record leads to the identification of pollen-derived biomes and seven (auto)ecological groups of taxa that discriminate environmental signal (depositional facies) and regional climate conditions within a well-dated coastal record. Percentage variations of hygrophytes, aquatics and pasture-meadow herbs reveal local environmental dynamics, enabling the detailed facies characterisation of the cored succession, especially in terms of water table conditions. Framed into a chronologically constrained, high-resolution facies context, the proportion of montane taxa (climate degradation indicator) relative to Mediterranean taxa and Quercus + other deciduous trees (climate optimum indicators) highlight a vegetation-climate variability in the plain that fits with Bond events, especially for the early-mid Holocene (i.e., Preboreal and Boreal Oscillation, 8.2 ka event), supporting a strong Mediterranean–North Atlantic climate connection. For the first time, pollen from a continental succession of the Adriatic area clearly depicts the effects of the 8.2 ka cooling event on vegetation patterns (progressive degradation in high altitude communities) and depositional dynamics (increased fluvial activity), assessing the major role played by climate changes in shaping coastal landscapes in addition to glacio-eustatic variations.

Stratigraphy and radiocarbon ages of late-Holocene Las Derrumbadas rhyolitic domes and surrounding vents in the Serdán-Oriental basin (Mexico): Implications for archeology, biology, and hazard assessment

The Serdán-Oriental lacustrine basin in the eastern part of the Trans-Mexican Volcanic Belt holds a volcanic field of >30 monogenetic vents. Among them, the ~1000-m-high, ~11 km3Las Derrumbadas rhyolite twin domes dominate the interior of the basin and are surrounded by smaller scoria cones, lava flows, shields, tuff rings, and maars. Of interest in this area are rare endemic species encountered in some of the maar lakes, as well as the large number of pre-Hispanic archeological sites indicating that the lacustrine environment became attractive as a dwelling hub during the late Holocene. We conducted a stratigraphic and radiocarbon dating study to reconstruct the volcanic history, assess the impact of past eruptions on the environment and pre-Hispanic populations, and evaluate future volcanic hazards. Accordingly, at least 10 volcanoes were identified to be < 25,000 BC of which eight are Holocene in age (Alchichica, Tecuitlapa, Atexcac, Cerro El Brujo, Tepexitl, Aljojuca, Derrumbadas, Piedras Negras). Hence, the central part of the Serdán-Oriental basin should be considered potentially active and new eruptions are likely to occur in the future. Furthermore, we show that the ~AD 20 Las Derrumbadas eruption is one of the most voluminous silicic effusive eruptions during the Holocene worldwide. This eruption possibly triggered a migration of human populations from dispersed rural hamlets in the central part of the basin toward fewer larger urban sites (e.g. Cantona) at its margins. Finally, the young ages of the maars imply that the unique biodiversity of their crater lakes must have developed over remarkably short timescales.

In situ cosmogenic 3He and 36Cl and radiocarbon dating of volcanic deposits refine the Pleistocene and Holocene eruption chronology of SW Peru

Constraining the age of young lavas, which generally fall outside the effective range of traditional geochronology methods, remains a key challenge in volcanology, limiting the development of high-resolution eruption chronologies. We present an in situ cosmogenic 3He and 36Cl surface-exposure chronology, alongside new minimum-limiting 14C ages, documenting young eruptions at five sites in the Western Cordillera, southern Peru. Four 3He-dated lavas on the Nevado Coropuna volcanic complex (hitherto thought to be dormant) indicate that the central dome cluster is young and potentially active; two Holocene lavas on the easternmost dome are the youngest directly dated lavas in Peru to date. East of Coropuna, lava domes and block-lava flows represent the most extensive output to date of Nevado Sabancaya, one of Peru’s most active volcanoes. Two 3He measurements confirm the Holocene age of these deposits and expand the chronology for one of the youngest major lava fields in Peru. 36Cl surface-exposure ages from the Purupurini dome cluster and Nevado Casiri document middle-late-Holocene episodes of effusive activity, while basal 14C ages from a lava-dammed wetland constrain an effusive eruption at Mina Arcata, north of Coropuna, to the late-glacial period. These new data advance the recent Western Cordillera volcanic record whilst demonstrating both the considerable potential and fundamental limitations of cosmogenic surface-exposure methods for such applications.

The impact of the submarine volcano Kick ‘em Jenny on benthic foraminifera

Nothing is known about the impact on marine meiofauna of submarine volcanic eruptions in the Grenada Basin. The benthic foraminiferal fauna is here examined in piston cores taken within ∼8 – 38 km of the crater of Kick ‘em Jenny (KeJ), decadal eruptions of which disseminate ash to the NW via the Caribbean Current. Piston core Gs29, taken ∼8 km W of the crater, consists of clay-rich material from the Globorotalia menardii Zone U, ∼500 ka old, probably exposed by slumping. The remaining cores (from proximal to distal: GC59, GC90, GC99 and GC100), taken between 1000 – 3000 m water depth, comprise volcanic ash and are of presumed Holocene age. Recovery from GC59, GC90 and GC99, the last taken 27.3 km NW of the crater, was poor and apparently reflects volcanic ash impact. Recovery from GC100, 38 km NW of the crater and from the basin floor, was rich. Thus, KeJ disrupts seafloor colonization by foraminifera up to 32 – 38 km from the crater. Bolivina spp., indicative of low dissolved oxygen concentrations, dominated the assemblage in proximal core Gs29. Cassidulina spp. dominated the distal core GC100 assemblage, indicating somewhat higher dissolved oxygen concentrations. This might reflect a long-term change in productivity in the area, or a nutrient-rich surface eddy to the lee of Grenada. Allochthonous, shallow-water foraminifera, recovered throughout cores Gs29 and GC100, were more abundant in the latter. This might indicate that Grenada protects nearshore foraminifera from disruptive hurricanes.

Younger Dryas glaciomarine sedimentation, push-moraine formation and ice-margin behavior in the Middle Swedish end-moraine zone west of Billingen, central Sweden

New highway exposures and drilling reveal the stratigraphy and structure of the Middle Swedish end-moraine zone west of Billingen, Sweden. The material in the end moraines is primarily glaciomarine clay of Younger Dryas age that was deposited as varved clay in front of the retreating glacier and then pushed glaciotectonically to form push moraines during minor ice-margin oscillations during overall retreat during the Younger Dryas cold event. The moraines are composed of deformed and remobilized clay with some clayey diamicton and penecontemporaneously deposited and deformed sand. Between the moraines lie ‘intermoraine flats,’ composed of undeformed varved clay of Younger Dryas age and surface sands of Younger Dryas to early Holocene age. Based on estimations of moraine volume, sedimentation rate and ice-margin retreat rates, we calculate the overall ice-margin retreat and end-moraine construction to span 350–800 years within the Younger Dryas. Because the number of moraines in the Middle Swedish end-moraine zone varies across Sweden, we regard the individual oscillations west of Billingen to be driven by local physical and glaciologic factors rather than ice-sheet wide climate drivers. The study area is also the location of the early and final drainages of the Baltic Ice Lake. The final drainage of the Baltic Ice Lake took place several decades after the youngest moraine was formed. We consider it likely that the earlier, Allerød drainage of the Baltic Ice Lake (BIL) also took place at Billingen, despite the lack of clear local stratigraphic evidence. However, based on our model, a retreat driven solely by climate would not have exposed the outlet at Billingen, and we propose a dynamic break-up of the ice-margin likely centered on Valle Härad that was driven by the head difference between the BIL and the sea.

Holocene faunal procurement and species response to climate change in the Ohio River valley

This paper examines the temporal distribution of 163 distinct species recovered from 21 well-dated Holocene age archaeological sites in the Ohio River valley to determine patterns of faunal resource procurement and their response to periods of climate change. Climate change proxies include bison, long-billed curlew, pine marten, porcupine, prairie vole, and swamp rabbit. While the rice rat may be a proxy of climate change, its initial appearance in the Archaic cultural period co-occurs with storable starchy and oily seed crops such as erect knotweed, little barley, marsh elder, maygrass, and sunflower. Subsistence proxies that transcend climate change include variety of aquatic (bass/sunfish, buffalo, channel catfish, freshwater drum, gar, mussels, snails, snapping and spiny softshell turtles, and river redhorse sucker), avian (blue-wing teal, Canada goose, and turkey), and terrestrial species (dog, eastern cotton-tail, elk, gray and fox squirrels, opossum, raccoon, timber rattlesnake, and woodchuck). Caldwell’s Primary Forest Efficiency remains a valid theoretical model of Holocene subsistence strategy in the Ohio River valley.

Geoarchaeology of the early medieval stronghold surroundings in grzybowo near Września, Greater Poland

Abstract The stronghold in Grzybowo (Rabieżyce village) near Września is a remnant of medieval ring-fort. It is investigated to a considerably lower degree than similar objects from Greater Poland. The analysis of archival data shows that the stronghold is located on the edge of the flood plain of the Struga River formed by Holocene sediments, cutting into the moraine plateau. Analysis of sediments in the stronghold vicinity revealed interlayers of organic matter and sandy deposits rich in calcium carbonate with variable grain size composition, particularly west of the stronghold (i.e. in the valley floor). Moreover, radiocarbon data set showed a considerably older than Holocene age of the sediment. The analysis of the course of the contemporary river channel also allowed for stating hypotheses regarding a potentially different course of the former Struga River channel and its changes during the development of the stronghold. These assumptions were based on the analysis of the archaeological archival data, where field drawings suggest the existence of such a channel in the territory of the stronghold.

Age and development of active cryoplanation terraces in the alpine permafrost zone at Svartkampan, Jotunheimen, southern Norway

AbstractSchmidt-hammer exposure-age dating (SHD) of boulders on cryoplanation terrace treads and associated bedrock cliff faces revealed Holocene ages ranging from 0 ± 825 to 8890 ± 1185 yr. The cliffs were significantly younger than the inner treads, which tended to be younger than the outer treads. Radiocarbon dates from the regolith of 3854 to 4821 cal yr BP (2σ range) indicated maximum rates of cliff recession of ~0.1 mm/yr, which suggests the onset of terrace formation before the last glacial maximum. Age, angularity, and size of clasts, together with planation across bedrock structures and the seepage of groundwater from the cliff foot, all support a process-based conceptual model of cryoplanation terrace development in which frost weathering leads to parallel cliff recession and, hence, terrace extension. The availability of groundwater during autumn freezeback is viewed as critical for frost wedging and/or the growth of segregation ice during prolonged winter frost penetration. Permafrost promotes cryoplanation by providing an impermeable frost table beneath the active layer, focusing groundwater flow, and supplying water for sediment transport by solifluction across the tread. Snow beds are considered an effect rather than a cause of cryoplanation terraces, and cryoplanation is seen as distinct from nivation.

Дарьгангын лаавын тавцан дахь Шилийн Богд галт уулын геоморфологийн хэлбэр

The Cenozoic volcanism, which has been active in the territory of Mongolia since the beginning of the last century, has attracted the attention of Central Asian researchers. The purpose of this study is to analyze the geological research materials of the previous study and to determine the morphological origin and morphology of Shiliin Bogd volcano as the key representative of Cenozoic volcanism. In general, due to the lava flow of basic composition, several types of geomorphological forms have been identified, and the identification of the type of dominant distribution is associated with a relation with origin problem that has not been encountered in our country before, and because of the current importance, the selection of the Shiliin Bogd volcano in Dariganga Plateau becomes important. The morphometric analyses were performed in-field measurements and previous studies, also highlighted the faults in satellite and other images using the morpho-structure method in order to depict the geomorphology of the Shiliin Bogd volcano. By comparing the results of the morphometric analysis, the Shiliin Bogd volcano morphological type was determined and a schematic diagram of the volcano's origin was developed. A large lava flow of fundamental composition flowed along to the large faults that stretched from the northeast to the southwest of the Shiliin Bogd volcano, which resulted in the current morphological forms of Shiliin Bogd and other volcanoes. The lava flow had a flow rate of less than 50% SiO2, which led to the creation of a Lava Plato. The morphological formations of lava cones, which are semicircular and basal in composition, with the average slope of the Shiliin Bogd volcano crater in 410, depth 63 meters and crater average diameter 302 meters, have been compared with morphology of other volcanoes by morphometric analysis. Based on the researchers' research data, the age of the trap of Shiliin Bogd volcano can be traced to the late Quaternary age, possibly to the Holocene age. Further details of the age of the basalt rock need to be precise.

The quaternary eruptive sequence of the Tengchong volcanic group, southwestern China

The Tengchong volcanic group in SW China is situated along the NS-oriented tectonic belt in the southeastern margin of the Tibetan plateau. The volcanic field has experienced intense tectonic stress due to the continuous subduction of the Indian plate under the Eurasian plate, and throughout Quaternary has experienced pervasive volcanism. The present volcanic rocks cover the successive domains of basic, intermediate (Group II) and acid (Group I) rocks, belonging to the high-K calc-alkaline series. Correspondingly, the eruption types of the Tengchong volcanoes roughly fall into two categories: explosive eruptions with large amounts of volcaniclastics and lava; and moderately quiet central eruptions with small amounts of scoria and lava overflow.According to systematic geochronological dating methods such as K-Ar, Ar-Ar, 14C AMS, and OSL dating, as well as field work, we separate the eruptive sequence of the Tengchong volcanic group during the Quaternary into four subsequences: the early Pleistocene, middle Pleistocene, late Pleistocene and the Holocene epoch. The early to middle Quaternary eruption sequence consists of a series of explosive eruptions, with almost all the eruptive dacitic volcaniclasts and lava constituting the bottom layer of the Tengchong basin. The Tengchong volcanism reached its climax in the late Pleistocene when it formed numerous cinder cones. A series of moderately quiet central eruptions occurred in the late Quaternary, and basic and intermediate-acid volcanic rocks formed the upper layer of the basin. From this study, three volcanoes are determined to be of Holocene age, and we conclude that the volcanic activity moved from the south and periphery to the north and center, and ended in the Heikongshan eruption ∼ 3600 years ago.

First radiocarbon dating of a Holocene eruption of the Datong volcanic field, eastern China

The accurate dating of prehistoric eruptions is essential for reconstructing volcanic sequences and for preparing volcanic-hazard assessments. The chronology of the eruptions of the Datong volcanic field (DVF) in eastern China has been debated for several decades, especially the start and end of volcanism. Loess sediments incorporated in explosive volcanic products have been described from the Dongpingshan scoria cone in the DVF. We conducted radiocarbon dating of the loess sediments, which produced an age of ~7300 cal yr BP for the Dongpingshan volcanic eruption. This result confirms the eruption of the DVF during the Holocene, and it provides important evidence for assessing volcanic hazards in this densely populated region. The Holocene age of the eruption indicates that DVF is dormant, contrary to previous studies which concluded that the DVF is extinct and that its volcanic eruptions ended at ~100 ka. In addition, this study documents a new method of dating Late Pleistocene to Holocene volcanic eruptions in and around the DVF, where loess sediments are widespread and may be preserved within volcanic products.