Late Devensian and Holocene landscape change in the uplands of the Isle of Man

The Late Glacial and Holocene geomorphology of the Manx uplands has received scant attention in previous researches. Solifluction deposits and terraces provide the earliest evidence for geomorphic activity after deglaciation. Fluvial incision into drift-choked valleys is correlated with the formation of the large mountain front alluvial fans that flank the Manx uplands. Formation of these alluvial fans is constrained to 15,000–10,500 cal. years BP by ¹⁴C dates on organic deposits beneath and above the alluvial fan gravels. Alluvial fan and river terraces along four valleys postdate this incision. Optically Stimulated Luminescence (OSL) and ¹⁴C dating provide a tentative chronology for these landforms. The higher terraces are Late Glacial fluvial surfaces that were probably occupied by rivers into the Holocene. Incision during the Late Holocene led to the abandonment of the higher surfaces, producing a suite of younger river terraces and alluvial fan surfaces. Independent dating constrains this fluvial activity to post-Bronze Age (3500–2800 cal. years BP). Increased human activity and climatic change during the Late Holocene are possible causes for this increased geomorphic activity.     

Catastrophic flood effects in alpine/foothill fluvial system (a case study from the Sudetes Mts, SW Poland)

Depositional effects of two great floods in the Nysa drainage basin have been studied: the alluvial forms and deposits of channels and floodplains. Three types of bars and one overbank form were found in the mountain streams, and four types of bars and three types of overbank forms have been distinguished in main rivers. A specific spatial succession of depositional forms was recognized along the mountain streams, however, no analogous phenomena were noted within the main river valleys. Several types of bars and alluvial lithofacies have been regarded as characteristic effects of the catastrophic flood. The study indicates that the Nysa river is close to the threshold of metamorphosis to a typical braided fluvial system.     

Small valley bottom deposits in the sandy districts of the Sarthe basin (France): climatic and/or human origin?

The study of the small valley bottom deposits in a sandy district where several recent erosional events have occurred makes it possible to distinguish deposits, which are caused by climatic oscillations from those induced by both climate and human activities. The coarse alluvium with flints, which reached the main valleys prior to the Subboreal, was transported by greater flows than those which resulted from later human-induced flood discharges, where flints were not evacuated from the small valleys. Radiocarbon dates of peat set those deposits in the Iron Age, in the transition from Antiquity to the Medieval period, at the end of the “optimum climatique de l'an Mil” and during the Little Ice Age. At the present time, human-induced flood discharges reach again the main valleys.     

全新世以来山东半岛东北部海面变化的河流地貌响应

对全新世以来山东半岛东北部沿岸的相对海面（基准面）变化,不同河流有截然不同的地貌响应方式。大沽夹河型河流的下游河谷中有分别与相对海面升降对应的溯源堆积期和溯源侵蚀期,但不同规模的河流仍有差异。黄水河型河流河谷未因基准面升降而发生侵蚀或堆积,河谷仅起了输沙通道的作用。此外,大沽夹河型河流的中下游河型在相对海面上升或下降时,还可能发生相应地网状化或曲流化。     

某巨型冰水堆积体强度特性大型常规三轴试验

在我国大渡河流域广泛分布一套规模巨大,形成于第四纪更新世中晚期的冰水堆积体.这类冰水堆积体在颗粒组成、结构特征、密实程度等诸多方面与其他松散堆积体存在较明显的区别,因而其变形特性、强度特性等方面与其他岩土体相比,也表现出较为明显的差异.以大渡河某巨型冰水堆积体为例,在室内大型常规三轴试验的基础上,对该冰水堆积体的变形特性、强度特性进行了较为深入的研究和探讨,结果表明该冰水堆积物在剪切破坏过程存在较明显的应变强化和剪胀现象,其强度包络线在低应力水平下呈直线状,在高应力水平下呈非线性下凹形,由此提出了应力水平与抗剪强度参数的试验关系式.     

福建武夷山风景名胜区及其附近地区的地貌研究

武夷山风景名胜区及其附近地区由花岗岩、火山熔岩、变质岩和砂页岩等构成的中山、低山占最大面积.最高海拔约1800m,在海拔350～1200m,有7级剥蚀夷平面,形态有山顶缓坡型、山坡肩膀型、谷底裂点型(占绝大多数).丹霞地貌的顶面坡以圆弧形为主,陡崖坡有罕见的切层洞穴群和最大的晒布岩,崖麓缓坡多由红层组成.河流纵谷常沿着NNE走向较软的中生界砂页岩发育,断层谷断续长数十公里;横谷常沿着NWW的走向节理发育.据6个TL年龄认定河流阶地的沉积年代:第一级阶地Q3 ,第二级阶地Q2或Q2为主,第三级阶地Q2.     

横断山区干旱河谷植被类型

横断山区干旱河谷植被,按植物群落的生态外貌、种类组成与结构特点,可分为4个类型(即:稀树灌木草丛,肉质刺灌丛,扭曲云南松疏林,小叶刺灌丛)15个群落。按干旱河谷的区域分异、水热状况、山地植被垂直带和利用方向,将本区干旱河谷分为4个类型(即:干热、干暖、干温、干凉)7个区。     

Low‐accommodation and backwater effects on sequence stratigraphic surfaces and depositional architecture of fluvio‐deltaic settings (Cretaceous Mesa Rica Sandstone,Dakota Group,USA)

The adequate documentation and interpretation of regional‐scale stratigraphic surfaces is paramount to establish correlations between continental and shallow marine strata. However, this is often challenged by the amalgamated nature of low‐accommodation settings and control of backwater hydraulics on fluvio‐deltaic stratigraphy. Exhumed examples of full‐transect depositional profiles across river‐to‐delta systems are key to improve our understanding about interacting controlling factors and resultant stratigraphy. This study utilizes the ~400 km transect of the Cenomanian Mesa Rica Sandstone (Dakota Group, USA), which allows mapping of down‐dip changes in facies, thickness distribution, fluvial architecture and spatial extent of stratigraphic surfaces. The two sandstone units of the Mesa Rica Sandstone represent contemporaneous fluvio‐deltaic deposition in the Tucumcari sub‐basin (Western Interior Basin) during two regressive phases. Multivalley deposits pass down‐dip into single‐story channel sandstones and eventually into contemporaneous distributary channels and delta‐front strata. Down‐dip changes reflect accommodation decrease towards the paleoshoreline at the Tucumcari basin rim, and subsequent expansion into the basin. Additionally, multi‐storey channel deposits bound by erosional composite scours incise into underlying deltaic deposits. These represent incised‐valley fill deposits, based on their regional occurrence, estimated channel tops below the surrounding topographic surface and coeval downstepping delta‐front geometries. This opposes criteria offered to differentiate incised valleys from flood‐induced backwater scours. As the incised valleys evidence relative sea‐level fall and flood‐induced backwater scours do not, the interpretation of incised valleys impacts sequence stratigraphic interpretations. The erosional composite surface below fluvial strata in the continental realm represents a sequence boundary/regional composite scour (RCS). The RCS’ diachronous nature demonstrates that its down‐dip equivalent disperses into several surfaces in the marine part of the depositional system, which challenges the idea of a single, correlatable surface. Formation of a regional composite scour in the fluvial realm throughout a relative sea‐level cycle highlights that erosion and deposition occur virtually contemporaneously at any point along the depositional profile. This contradicts stratigraphic models that interpret low‐accommodation settings to dominantly promote bypass, especially during forced regressions. Source‐to‐sink analyses should account for this in order to adequately resolve timing and volume of sediment storage in the system throughout a complete relative sea‐level cycle.     

华北山地的古河道与古水系*

华北山地早第三纪地貌奠定了现代水系格局的基础。至晚第三纪晚期河流已发育到中-老年阶段。第三纪末期至第四纪早期,山地差异活动剧烈,断陷盆地形成,内、外流水系并存,遗留下垭口与顺直-曲流型宽谷。第四纪中期,河流袭夺,内陆水系先后变成外流水系,并生成“U”形宽谷。第四纪晚期,河流下切,水系变迁,现代水系形成。     

The ecologo-geographical framework for the protection and recovery of taiga reindeer populations within the Konda river basin (Western Siberia)

The key aspects of reindeer ecology within the Konda river basin are considered. The study revealed the factors governing the characteristics of calving reindeer pastures determined by the structure of forest-bog landscapes of a different generalization level. A deficit of such pastures is regarded as the factor of differentiation of reindeer groups with respect to migrants and residents. It is shown that the individual geocomplexes have a multifunctional role. Of particular significance among them are the aufeis glades with outcrops of salt-saturated groundwater, and the dark-coniferous forests along river valleys rich in epiphytic lichens (beard lichens).     

Scaling in river corridor widths depicts organization in valley morphology

Landscapes have been shown to exhibit numerous scaling laws from Horton's laws to more sophisticated scaling in topography heights, river network topology and power laws in several geomorphic attributes. In this paper, we propose a different way of examining landscape organization by introducing the “river corridor width” (lateral distance from the centerline of the river to the left and right valley walls at a fixed height above the water surface) as one moves downstream. We establish that the river corridor width series, extracted from 1 m LIDAR topography of a mountainous river, exhibit a rich multiscale statistical structure (anomalous scaling) which varies distinctly across physical boundaries, e.g., bedrock versus alluvial valleys. We postulate that such an analysis, in conjunction with field observations and physical modeling, has the potential to quantitatively relate mechanistic laws of valley formation to the statistical signature that underlying processes leave on the landscape. Such relations can be useful in guiding field work (by identifying physically distinct regimes from statistically distinct regimes) and advancing process understanding and hypothesis testing.     

Formation of river terraces in conditions of high seismicity

We have investigated the river terraces on the left bank of the Irkut river in the Torskaya depression a short distance from the village of Guzhiry. On the basis of lithological-geological findings and radiocarbon datings of buried soils from two sections of the second terrace (12–14 m), we identified nine formation stages of the terrace in the latter half of the Late Neopleistocene and in the Holocene. They reflect multiple changes of the leading exogenous process, implying a variety of the genetic types of deposits (soils, and aeolian and alluvial sediments) during the Early and Mid-Holocene. The formation stages of alluvium are correlated with periods of high water. It is found that the final transition of alluvial to cover deposits is associated with incision of the river to 2–4 m and is dated to 5.2–4.5 cal. ka. We examine the alternation of the natural factors for the formation of deposits of the second terrace of the Irkut river in the Late Neopleistocene and Holocene. One (hydroclimatic) factor implies accumulation of deposits of the alluvial and cover complex depending on climate and water runoff fluctuations, landscape changes, and on variation in the base level of erosion. The other (seismic) factor is correlated with data on high activity of the Tory paleoseismogenic structure, which seems to have caused the lowering as well as the rise of the bottom of the depression at the time of strong earthquakes and, as a consequence, erosion or accumulation of deposits of the channel facies of alluvium. It is established that the chief causes for the change of the terrace’s deposit types were the natural-climatic changes, the character and directedness of tectonic movements, the variations in the base levels of erosion, and the height of floo ds.     

Landscape and Coast Development of A Lowland Fjord Margin Following Deglaciation, East Greenland

The landscapes of western Jameson Land bordering Hall Bredning fjord comprise upper river basins, glacial landscapes, lower river basins and a near‐shore zone. The upper river basins are incised into bedrock and display no cover of young sediments whilst the glacial landscapes, located closer to the coast, are dominated by Pleistocene deposits and an irregular topography with hills and ridges. The lower river basins, dissecting the glacial landscapes, are connected to the upper river basins and contain well‐defined Holocene delta terraces. The near‐shore zone, which includes the present coast, displays a few raised shorelines. Geomorphological observations combined with stratigraphic work and ¹⁴C dates provide a chronological framework for the development of landscape and shoreline, as presented by a four‐stage reconstruction. The first stage covers the deglaciation of western Jameson Land at the Weichselian‐Holocene transition after a collapse of the main fjord glacier in Hall Bredning. The sea inundated the low‐lying areas on Jameson Land forming small side‐entry fjord basins that possibly follow the track of older valleys. This was followed by a second stage, the paraglacial period, when large meltwater production and sediment transport resulted in a fast infilling of the side‐entry fjord basins by deltas. These are now exposed in terraces in the lower river basins at 70–80 m a.s.l. During a third stage, the relaxation period, fluvial activity decreased and the land surface was increasingly occupied by a cover of tundra vegetation. A glacio‐isostatic rebound resulted in a relative sea level fall and fluvial incision. During stages two and three the coast was exposed to shallow marine processes that aided the alignment of the coast. Stages one to three presumably lasted for less than 2000 years. During stage four, the stable period, lasting for several thousand years till the present, there were minor adjustments of shoreline and landscape. The four‐step reconstruction describes the sedimentary response of a lowland fjord margin to dramatic changes in climate and sea level. The distribution of erosion and sedimentation during this development was mainly controlled by topography. The reconstruction of the latest environmental development of Jameson Land puts new light on Jameson Land's long and complex Quaternary stratigraphic record. The reconstruction may also be used as a model for the interpretation of deposits in similar areas elsewhere.     

现代黄河三角洲叶瓣的划分和识别

黄河分流河道摆动频繁,自1855年以来形成了8个三角洲叶瓣。1904-1929年的三角洲沉积物划归一个叶瓣较为合适。1934-1938年和1947-1964年也应该划归一个叶瓣。叶瓣活动时间短,平均活动时间只有16年。单个叶瓣形成的沉积物厚度有限。一个钻孔剖面上的三角洲沉积物常常分层于数个叶瓣。叶瓣废弃后改造时间短,还没有形成较粗的改造,沉积物便被新的叶瓣所覆盖。两个叶瓣的界线不很清楚。但根据沉积结构和构造,微体化石,²¹⁰pb测年方法,土壤层以及历史记录,可以识别出不同的叶瓣。     

Proglacial Lake-ice Conveyors: A New Mechanism for Deposition of Drift in Polar Environments

Interpretation of sediments in the floors of valleys opening into western McMurdo Sound has been so problematic that it has hindered understanding of the late Quaternary history of the Antarctic Ice Sheet. Lateral moraines and enclosed drift sheets so clearly exposed on the headlands are generally absent within the valleys themselves. Instead, valley-floor sediments and landforms consist of hummocky, stratified fine sediment generally capped by coarser, poorly sorted material, small cross-valley and longitudinal ridges, and lateral ridges that superficially resemble shorelines. One clue as to the origin of these deposits is that at least some of the valleys were occupied by large proglacial lakes during the last glacial maximum (e.g. Glacial Lakes Trowbridge and Washburn in Miers and Taylor Valleys, respectively). This paper describes a new mechanism observed in a modern perennially ice-covered proglacial lake that documents the movement of glacial debris beyond the grounding line across the surface of the lake. This mechanism accounts for the absence of moraines and other ice-contact features on the valley floors, as well as for the presence of the other deposits and landforms mentioned above.     

Structural-hydrographic and morphometric analysis of river systems: Theoretical aspects

We examine the current possibilities for a further development and some basic notions of structural-hydrographic analysis of river systems. The advent of digital medium-scale global data on land surface and generally available software products strongly dictates a need to switch over from a functional to structural-functional modeling as the basic tool of land surface hydrology. On the other hand, the concepts from classic geo-morphology on the energy of topography, the structure of river basins and their linkage to modern tectonics, and on phenomena of double and antecedent valleys can be verified using a large body of statistical data to obtain a further development, based on introducing digital terrain models (DTM) and new algorithms for their processing.     

STORAGE OF MINING-RELATED ZINC IN FLOODPLAIN SEDIMENTS,BLUE RIVER,WISCONSIN

This study investigates spatial patterns of sediment-associated zinc (Zn) storage in floodplain deposits and the potential reintroduction of these metal-contaminated sediments to the active channel by bank erosion. We estimate patterns of Zn mass storage by combining longitudinal trends in Zn concentrations with measurements of sediment mass storage in overbank and point-bar deposits. Overbank deposits are the largest contaminant sink, storing five times more Zn than the point-bar deposits. While Zn concentrations decrease downstream because of dilution effects, the total mass of Zn stored in floodplains is greatest in both the upstream reaches and in the wider lower valleys where low channel gradients promote rapid sedimentation. Zn storage is low in middle reaches where steep, narrow valleys with high stream power favor sediment transport over deposition. Overall, more than half of the Zn released by mining remains stored in floodplain deposits within the watershed. The remobilization of Zn from storage is more likely in the upstream and mid-basin reaches where high stream power increases rates of lateral channel migration. Channels in the lower valley lack the stream power to migrate laterally and remobilize the large Zn mass stored in overbank sediments. [Key words: floodplains, Zn contamination, mining, stream power, Wisconsin.]     

Landforms and landscape evolution in the Skardu,Shigar and Braldu Valleys,Central Karakoram

The Central Karakoram, which includes K2 in Pakistan, is one of the most rapidly rising areas on Earth and exhibits complex topography and extreme relief. Impressive valley fills and glacial landforms are present throughout the valleys. The dynamics of landscape evolution of the region are currently not well understood. Consequently, the landforms were mapped and assessed in the Skardu, Shigar, and Braldu valleys, to elucidate the spatio-temporal scale dependencies of surface processes active in the region. These valleys were examined using geomorphic field methods, remote sensing, geomorphometry, and terrestrial cosmogenic nuclides (TCNs) surface exposure dating. The glaciers in this region have oscillated considerably throughout the Late Quaternary, and four glacial stages have been recognized including at least six glacial advances. Surface processes readjusted after glacier retreat, and ubiquitous mass movements and catastrophic landsliding transported material from steep slopes to valley bottoms, while glaciofluvial meltwater and glacier outburst floods redistributed sediment down valley. Glacier geochronology and late Holocene ages of the outburst flood deposits indicate that landscape evolution has been dominated by glaciation and paraglaciation during the late Quaternary.     

The Southern Margin of the Late Cainozoic Ice Cap on the Central Plateau of Tasmania

The easternmost extremity of the ice cap that developed in the Tasmanian Central Highlands during the time of most extensive Late Cainozoic glaciation lay on the doleritecapped Central Plateau east and north-east of Lake St Clair. During the Last Glacial Maximum (LGM), the more restricted ice cover included a small discrete ice cap (probably less than 250-300 m thick) that formed on the Central Plateau. The LGM ice limits on the southern part of the Central Plateau, including all five southern outlet valleys, are reported here. Earlier ice limits have been identified in two of these valleys, but on the plateau proper earlier glacial deposits have been generally extensively reworked beyond the LGM limit, such that confirmation of a glacial origin for diamictons on slopes is difficult. South of the plateau, the oldest deposits flooring lower reaches of two outlet valleys indicate that ice flowed southwards directly from the plateau, but later deposits indicate diffluent flow from the Derwent Glacier.     

Periglacial nivation cirques and local glaciations in the rock canyons of Söderåsen,Scania, Sweden. A discussion and new interpretation

Rapp, Anders: Periglacial nivation cirques and local glaciations in the rock canyons of Söderåsen, Scania, Sweden. A discussion and new interpretation. Geografisk Tidsskrift 82: 95–99, Copenhagen, October 15, 1982.

Present opinions about the genesis of the rock canyons OdensjOn, Skäralid and Klöva Hallar of Söderåsen, Sweden are reviewed, and a new theory is presented. It is proposed, that during periglacial tundra periods large amounts of drifting snow collected in valleys of north-south directions. Small glaciers were created, which caused local overdeepening and removal of loose material. These processes were active in tundra periods before and after the main Quaternary glaciations.

SUMMARY

Odensjön, Skäralid and Klöva Hallar are three valleys of canyon type, deeply cut (60–100 m) into the horst block of Söderåsen, of fractured Precambrian gneiss rock. It has been shown by other authors that the cold periods after the Weichselian deglaciation were characterized by permafrost and ice wedges on sandy plains in south Sweden. Strong winds caused widespread wind-polishing of stones and bedrock, predominantly from easterly and westerly directions. Based on this evidence, the author presents the theory that large deposits of wind-blown snow were trapped in the canyon valleys of Söderåsen, except for the valleys of east-west directions. The snow was metamorphosed to firn and local, small glaciers, which filled the valleys. The rims of the canyon valleys have in many cases well developed nivation hollows, either steep nivation funnels or gently sloping, semicircular nivation cirques. Odensjøn is a closed, semicircular rock basin, which has been much discussed by scientists earlier, and which seems to fit the theory of creation by nivation from mainly west, but also east, and a local cirque glacier flow northwards causing the overdeepening and removal of loose material. The three valleys mentioned were problably widened and deepened into a series of nivation basins in tundra periods before and after each major continental glaciation. The nivation hollows and the deep canyon valleys were not destroyed by glacial erosion during the Weichselian and earlier Quaternary major ice advances, because the valleys were filled with densely packed snow and ice from snow drifting before the main glacier front moved over them from NE directions. The theory will be further checked by a team of scientists from the Department of Physical Geography in Lund. A comparison is made with cirque forms in present-day mountain tundra conditions in the area of Kärkevagge in northern Lappland, investigated by the author during the 1950's and later.