Frequency of fast geomorphological processes in high-gradient streams: case study from the Moravskoslezské Beskydy Mts (Czech Republic) using dendrogeomorphic methods

High-gradient streams are localities with the most dynamic activity of geomorphological processes in medium-high mountains. This study of the frequency of floods and debris flows in a selected high-gradient stream in the Moravskoslezské Beskydy Mts was based on a dendrogeomorphic approach. It makes use of the most accurate methods applied in the dating of historic geomorphological processes. Individual events were reconstructed on the basis of the dating of various growth disturbances displayed in 99 samples taken from 56 predominantly broad-leaved trees.     

Obituaries

Abstract

A rich variety of processes have modified the glacial landscape of the Scottish Highlands since the last glaciers disappeared 11,500 years ago. Many of these processes can be described as paraglacial (glacially-conditioned): retreat of glacier ice has resulted in exposure of metastable sediment sources (rock slopes, drift-mantled slopes and valley-floor glacigenic deposits) that have been reworked over a range of timescales. Much of the reworked sediment has been deposited in paraglacial sediment stores (talus accumulations, debris cones, alluvial fans, valley fills, river terraces and deltas). The trajectory of paraglacial sediment transfer can be approximated by an exhaustion model. A corollary of this model is that all sediment stores eventually undergo a change from net accumulation to net erosion, reflecting the non-renewable nature of sediment sources. This concept helps to explain why most talus accumulations, debris cones and alluvial fans in the Highlands are now relict, and why many floodplains appear to have experienced an initial period of aggradation followed by later river incision and terrace development. Since deglaciation, rock slopes have experienced paraglacial stress release due to differential deglacial unloading. Many rock slopes have remained stable or experienced gradual adjustment through intermittent rockfall. At over 600 sites, however, large-scale rock-slope failure has occurred, either in the form of catastrophic failure with complete or arrested debris runout, or as major slope deformations. Modification of drift-mantled slopes has been dominated by rainstorm-generated debris flows activity, which have stripped sediment from slopes and redeposited it in debris cones. Radiocarbon dating of buried organic horizons shows that debris flows have occurred intermittently throughout the Holocene. Snow avalanches have played only a localized role in paraglacial sediment transfer. The Holocene alluvial history of the Highlands is poorly understood. Some alluvial fans formed during a few exceptional flood events, and there is evidence that postglacial floodplain aggradation peaked in the late Holocene and was succeeded by floodplain incision and terrace development, possibly reflecting upstream reduction in paraglacial sediment supply. Other processes have operated independently of glacial conditioning. The effects of wind action are dominant in the coastal zone, forming dunefields through aeolian reworking of beach sand, and on plateaux in the form of deflation surfaces and sand sheets. Extensive erosion of plateau-top sands and aeolisols occurred in the period AD 1550–1700, a period of exceptional storminess. Small-scale periglacial processes have also been active on high ground throughout the Holocene, including granular weathering of exposed rock surfaces, the development of small-scale frost-sorted patterned ground on unvegetated terrain, and slow downslope movement of solifluction sheets, solifluction lobes and ploughing boulders.     

Optical dating of alluvial deposits at the orogenic front of the andean precordillera (Mendoza,Argentina)

Well constrained numerical ages of alluvial fan sediments are key to understanding the chronology of alluvial episodes and tectonic activity at the front of the Andean Precordillera. We tested the application of radiocarbon and optically stimulated luminescence (OSL) dating in the distal part of an alluvial fan five kilometers north of Mendoza. For OSL dating a large number of aliquots (n > 70) — each composed of ∼50 quartz grains — were measured in order to obtain reliable burial ages despite scattered dose distributions. Owing to a feldspar contamination in all samples, an infrared stimulation was inserted before each OSL measurement, which reduced the feldspar OSL signal successfully. By using the minimum age model we obtained stratigraphically consistent burial ages of alluvial deposits in a depth profile. The uppermost ∼1 m of sediment is composed of debris flow deposits buried 770±76 years ago. Three plant remnants used for radiocarbon dating from the same layer, however, yielded ages younger than 350 years, which are interpreted to underestimate the depositional age. Underneath the debris flow, a major unconformity cuts a series of distal alluvial fan sediments with interstratified floodplain deposits, which are composed of sandy and calciterich silt layers, respectively. Three samples from this unit which were distributed over one meter of sediment thickness yielded statistically concordant OSL ages of 12.3±1.2 ka, 12.3±1.2 ka, and 11.7±1.1 ka. The deposition of these sediments during the latest Pleistocene coincides with a phase of cool and humid climate, which occurred before the alluvial fan propagated farther into the foreland. The overlying debris flow sediments are associated with alluvial fan incision during the arid Late Holocene.     

Meta-analysis of dendrochronological dating of mass movements

Absolute dating of mass movements is crucial for disentangling possible release factors and determining the frequency of events. Here, we present an overview of a recent approach to dendrochronological dating of rockfalls, flows, landslides and avalanches. The results, based on 69 casestudies, show that methodological approaches to sampling and material processing differ considerably for different types of mass movements. Landslides are usually detected through abrupt growth changes and changes in stem eccentricity, whereas high-energy events as avalanches and flows are mostly identified by the formation of traumatic resin ducts, reaction wood, growth injuries and eccentricity changes. Cross-dating of dead wood is applicable as well. The dating of most mass movements except landslides is common, even with sub-annual resolution. In comparison to other methods of absolute dating, the main benefit of dendrochronology still lies in the high temporal resolution of the results. If living material is accessible, on-going research progress makes absolute dating of most mass-wasting events possible with sub-annual precision.     

Late Pleistocene marine birds from southern Peru: distinguishing human capture from El Niño-induced windfall

The Central Andean hyperarid littoral has abundant marine fauna that would have been attractive to the earliest inhabitants. Whether people hunted or scavenged marine animals during the terminal Late Pleistocene have social and technological implications for understanding ancient Andean foraging. The periodic phenomenon of El Niño/Southern Oscillation (ENSO) disrupts marine food chains and results in the death of significant numbers of marine vertebrates and microorganisms. The onset of ancient El Niño events may have created a subsistence opportunity for human coastal inhabitants along the Pacific coast of the Central Andes when large numbers of guano-producing birds (cormorants, boobies, and pelicans) became weak and eventually died. The remains of numerous marine birds dominate the Late Pleistocene archaeological site of Quebrada Tacahuay in far southern Peru. This Terminal Pleistocene occupation dating to 10,770–10,290 years ago (uncalibrated radiocarbon years; 12,880–11,970 calendar years ago) was buried and sealed by an apparent ancient El Niño-induced debris flow. Using characteristics of the faunal assemblage I assess whether people hunted marine birds or ENSO created a subsistence opportunity for people to either scavenge a catastrophic assemblage or collect a community of vulnerable birds prior to the debris flow. I present avian skeletal part frequencies, butchering patterns, and the quantities and variety of marine bony fishes. An analysis of vertebrate taxonomic and skeletal composition in conjunction with an analysis of site context does not support the hypothesis that paleoenvironmental conditions generated an opportunity for the facile collection of either dead or weak birds. In contrast, the faunal data suggest that humans actively hunted, captured, and consumed healthy marine birds. When evaluating the possible role of environmental fluctuations on human behavior and diet, researchers must consider not only the taphonomy of the most abundant remains, but also how other vertebrate taxa in a region are affected as well as the archaeological context.     

Field Measurements and Numerical Simulation of Debris Flows from Dolomite Slopes Destabilized during the 2005 Kashmir Earthquake,Pakistan

A devastating earthquake occurred in Kashmir, Pakistan on October 8, 2005. This earthquake resulted from reactivation of a known active fault later defined as the Balakot–Bagh fault, which caused widespread slope failure throughout its stretch, particularly around Muzaffarabad, the provincial capital of Azad Jammu and Kashmir. This slope failure resulted in a huge amount of debris material which flows in deeply incised creeks during monsoon and hits the inhabitants along the valley in Muzaffarabad. Two GPS measurements are carried out along with channel morphometric parameters and observed changes to investigate the effect of debris flows along these creeks during monsoon. Other than the physical measurements, actual debris flow is simulated using the Depth Average Material Point Method (DAMPM) after carrying out parametric study and calibrating the model for subject topographical and geological settings. The generalized effect of different input parameters of the model on debris flow runout features is studied and discussed in detail. After ensuring validation of the numerical tool, the contribution of a single closed-type check dam to decrease runout intensity to its downstream reach is also investigated for different locations to obtain optimized selection.     

Selective woodland exploitation for charcoal production. A detailed analysis of charcoal kiln remains (ca. 1300–1900 AD) from Zoersel (northern Belgium)

A detailed study of charcoal burning activities has been made for the Zoersel forest (Northern Belgium) based on an inventory of charcoal kiln remains, the analyses of wood charcoal and other charred botanical macroremains and radiocarbon dating of 10 of these kilns. Age determination of the youngest kilns was refined by dendrochronological analysis of trees growing on top of these kiln sites. The results show that, although many kilns were found, charcoal was produced in Zoersel only at certain moments during late and post-medieval times suggesting that charcoal burning was not a part of the regular management practice of these forests. The wood used for the production of charcoal mainly consists of taxa of alluvial (alder) forests while the kilns are situated on sites that currently are rather dry, with an oak dominated vegetation. For the older kilns, this contrast could be explained by an important change in local soil conditions. The younger kilns may be related to the conversion of alder woodland to grassland in the lower parts of the domain, with the kilns being constructed in the nearby dryer woodland areas.     

Large-scale Debris Flow Disasters: Hazard-Risk-Vulnerability Analysis Approach in Taiwan

Catastrophic disasters may cause irreversible damage to cultural heritage. This study identified the risk to cultural heritage sites in Taiwan posed by large-scale debris flow disasters. The cultural heritage sites that may be affected by debris flows were identified through risk identification and by using GIS. Subsequently, an on-site field survey was conducted to confirm the cultural heritage sites that are potentially vulnerable to debris flow disasters. The research findings are as follows: (a) the top three cultural heritage sites that are most affected by debris flows are municipal, county, and city monuments, historical buildings, and historical sites; (b) the number of cultural heritage sites affected is related to environmental exploitation; (c) the cultural heritage sites at high risk of being affected by disasters were primarily located in Taitung and Chiayi Counties.     

怀袖雅物——上海明墓出土折扇和扇坠珍赏

折扇起源于日本,旧称倭扇,是日本人受蝙蝠形象启示而制作的,故亦称蝙蝠扇,在11世纪时由日本、高丽（朝鲜）传人中国。据南宋吴自牧《梦梁录》记载：当时杭州城外的镇市上,已有专卖折扇（折叠扇）的店铺。邓椿《画继》则明确记有“市井上所制折叠扇者”。折扇是折叠扇的简称,它以竹木或象牙等为骨,韧纸或绫绢为面,可收拢折叠,因此又称撤扇、聚头扇、聚骨扇等。     

Dendrochronological methods for reconstructing mass movements — An example of landslide activity analysis using tree-ring eccentricity

Dendrochronological methods can be applied to the reconstruction of different types of environmental events such as climate changes, fires, glacier movements, floods, earthquakes, volcano activity. In the field of geomorphology dendrochronology is increasingly frequently used for the absolute dating of different types of mass-movements (rock falls, landslides and debris flows, etc.). Trees growing on slopes transformed by mass-movements are tilted and wounded while their stems and root systems are exposed or buried under sediment. These events are recorded in wood anatomy as eccentric growth, reaction wood, scar overgrowth by callous tissue, changes in cell size or adventitious root production. Dating changes in wood anatomy allows to date and precisely reconstruct the spatial and temporal occurrence of mass-movements with at least one year resolution. The paper provides a review of existing dendrochronological tools used in geomorphology and also an example of the application of eccentric tree-growth to reconstruct landsliding. Using tree-ring eccentricity allows to (1) obtain a dynamic depiction of slopes, (2) study landslide activity, not only contemporary, but also in the last tens of hundreds of years (depending on the stand age).     

Quebrada Tacahuay,Southern Peru: A Late Pleistocene Site Preserved by a Debris Flow

Abstract

Here we describe the properties of a debris flow apparently generated by a warm phase El Niño event that buried an intermittently occupied Late Pleistocene forager site located in the southern coastal desert of Peru. Although the event deposited roughly one meter of sediment over the initial occupation, our analyses of debris flow dynamics and data from large scale archaeological investigations indicate that the earliest anthropogenic deposits at the site of Quebrada Tacahuay were preserved intact as a result of the burial episode; there is no evidence that the debris flow scoured or disturbed the cultural deposits. The event that buried the oldest archaeological contexts at Quebrada Tacahuay differs from other flood events that are characterized by turbulent, fast-moving floodwaters. Our data on debris flow dynamics and our results from excavation have implications for identifying, investigating, and interpreting other deeply buried archaeological sites both in the central Andes and in other geographic regions.     

Proposing new approaches for dating young volcanic eruptions by luminescence methods

The application of luminescence dating to young volcanic sediments has been first investigated over three decades ago, but it was only with the technical innovations of the last decade that such analyses became viable. While current analytical procedures show promise for dating late Quaternary volcanic events, most efforts have been aimed at unconsolidated volcanic tephra. Investigations into direct dating of lava flows or of non-heated volcanoclastics like phreatic explosion layers, however, remain scarce. These volcanic deposits are of common occurrence and represent important chrono- and volcanostratigraphic markers. Their age determination is therefore of great importance in volcanologic, tectonic, geomorphological and climate studies. In this article, we propose the use of phreatic explosion deposits and xenolithic inclusions in lava flows as target materials for luminescence dating applications. The main focus is on the crucial criterion whether it is probable that such materials experience complete luminescence signal resetting during the volcanic event to be dated. This is argued based on the findings from existing literature, model calculations and laboratory tests.     

Pliocene sand injectites from a submarine lobe fringe during hydrocarbon migration and salt diapirism: a seismic example from the Lower Congo Basin

Large‐scale conical and saucer‐shaped sand injectites have been identified in the Upper Miocene sediments of the Lower Congo Basin. These structures are evidenced on the 3D high‐resolution seismic data at about 600 ms TWT (two‐way traveltime) beneath the seabed. The conical and saucer‐shaped anomalies range from 20 to 80 m in height, 50 to 300 m in diameter, and 10 to 20 ms TWT in thickness. They are located within a sedimentary interval of about 100 m in thickness and are aligned over 20 km in dip direction (NE‐SW), above the NW margin of an underlying Upper Miocene submarine fan. We have interpreted the conical and saucer‐shaped anomalies as upward‐emplaced sand injectites sourced from the Upper Miocene fan because of their discordant character, the postsedimentary uplifting of the sediments overlying the cones and saucer‐shaped bodies, the alignment with the lateral fringe of the Upper Miocene submarine fan, and the geological context. Sand injection dates from the Miocene–Pliocene transition (approximately 5.3 Ma). The prerequisite overpressure to the sand injection process may be due to the buoyancy effect of hydrocarbons accumulated in the margins of the fan. Additionally, overpressure could have been enhanced by the lateral transfer of fluids operating in the inclined margins of the lobe. The short duration of sand injection and the presence of many sandstone intrusions suggested that the process of injection was triggered by an event, likely due to a nearby fault displacement related to diapiric movements. This is the first time that sand injectites of seismic scale have been described from the Lower Congo Basin. The localized nature of these injectites has led to a change in the migration path of fluids through the sedimentary cover. Consequently, the sand intrusions are both evidence and vectors of fluid migration within the basin fill.     

生之意志的最后温存——论岜沙苗寨的生命教育

在地球某个角落,生活在林荫中的一群人用他们的行动和习俗演绎着对神的虔诚,对祖先的眷念及对生命的特殊理解。他们被称为中国最后一个枪族部落,大树的民族。他们过着大部分中国人所向往的桃源生活,享受着现代人已久违的那份清淡与宁静。这就是至今仍信仰着人树同体的贵州从江县岜沙苗人。     

Age and sedimentological features of fluvial series in the Toruń Basin and the Drwęca Valley (Poland)

The deposits of the Toruń Basin are dominated by a few-metre thick sand series which fill up buried valley-like depressions. In many cases they underlie the Weichselian till which builds up the ice marginal streamway (pradolina) terraces or they are exposed at the basin slopes. As the results of the geological and sedimentological studies, as well as of the dating of the deposits at the sites in the Toruń Basin indicate, the deposits include two fluvial series accumulated before the advancement of the Leszno Phase ice sheet, i.e. in Middle Weichselian and at the beginning of Late Weichselian. The oldest fluvial series connected with the Saalian Glaciation was found at the mouth section of the Drwęca Valley. The fluvial system of the Toruń Basin during Middle Weichselian and at the beginning of Late Weichselian developed in two phases of the sand-bed braided river. During the first one the river channel were dominated by large mid-riverbed sandbars, while during the second phase the water flow was smaller and, as a result, low transverse sandbars and two-dimensional dunes developed. Other active river channel also showed low-energy flows, more intensive meandering than in the case of the braided rivers, as well as sandy side-bars. Analysis of the rounding and frosting of the quartz grains indicate that the studied series of the Weichselian sandy deposits represent alluvia of a river which were fed from two diverse sources. The first one might have represented the alluvia of a warm river which transformed its load, while the other one might have mainly carried the underlying Quaternary deposits.     

折迭扇的输入与仿制

“摺扇”起源于日本,大约于北宋中期输入中国。元末明初,随着中、日间贸易的发展,外来的“摺扇”成为当时的“时髦”,从而加快了中国仿制技术的发展。     

怀袖雅物 苏州折扇六百年（上）

中国最早的扇子,传说始于虞舜。晋崔豹《古今注·舆服》说：＂五明扇,舜所作也。既受尧禅,广开视听,求贤人以自辅,故作五明扇焉。秦汉公卿、士大夫皆得用之;魏晋非乘舆（皇帝）不得用也。＂由此看来,最早的扇子主要并非风,而是帝王们为了广开视听,招贤辅政,将治国的主张写在扇子上,用来昭示清明。     

丹青咫尺 扇里乾坤—吉林省博物院藏扇画赏析

摇曳生风千秋过,扇子原本不过是御风消暑、驱逐蚊蝇的实用品和装饰物,它在古代的别称为“摇风”、“凉友”,不光达官贵人使用,平民百姓也广泛使用。我国早在商代就有了扇子的雏形,汉代以后,扇子从煽风发展到士人淑女把玩的装饰品,少女们常喜欢用绘有图画的纨扇半遮脸面,而被人们形容得更美丽,于是扇子又有了“便面”、     

Dendrochronological dating of a wooden causeway in Finland

A mean ring‐width chronology for Scots pine in eastern Finland has been compiled based on living trees and dendrochronologically dated historical timber constructions. As an application of this master chronology, a young archaeological site near the town of Hämeenlinna, southern Finland, was dated. A previous assumption of the age of this site was that it could even be medieval. The construction was not older than 160 years, the road having been built after 1828, the year of growth of the outermost tree rings of the samples. A new pine chronology for southern Finland extending to the year AD 1539 is presented and it is now applicable for precise dating purposes in this area.     

Hydrothermal fluid flow models of stratiform ore genesis in the McArthur Basin, Northern Territory, Australia

This paper explores the role of basin‐scale fluid migration in stratiform Pb–Zn ore formation in the southern McArthur Basin, Australia. Mathematical models are presented for coupled brine migration and heat transport in the basin. The models account for: (i) topographically driven flow (forced convection) during periods when parts of the McArthur Basin were subaerial and elevated above the central Batten Fault Zone; (ii) density‐driven flow (free convection) during periods when the basin was mostly submarine; and (iii) transient flows associated with fault rupture during periods of transpression. These hydrologic models help to compare and contrast a variety of hypotheses concerning deep fluid migration and the origin of base metal ores in the McArthur Basin. The numerical results exhibit a strong structural control on fluid flow caused by the north‐trending fault systems that characterize the Batten Fault Zone. As a result, fluids descend to depths of a few kilometers along the western side, migrate laterally to the east through the clastic and volcanic aquifers of the upper Tawallah and lowest McArthur Groups, and then ascend along the eastern side of the fault zone. This recharge–discharge pattern dominates all of the hydrogeologic models. The basin‐wide flow pattern suggests that Na–Ca–Cl brines acquired base metals in the deepest levels of the basin stratigraphy as the fluids migrated eastwards through the aquifer system. Upward flow was relatively rapid along the Emu Fault Zone, so much so that fluid temperatures likely approached 130°C in the muddy sediments near the sea floor due to upward flow and venting at the HYC (‘Here’s Your Chance'). Transient pulses of flow characterized periods of transpressional stress and subsequent faulting may have punctuated the basin history. Large‐scale free convection, however, characterized notably long periods of diagenesis and ore mineralization during the Proterozoic in the McArthur Basin.