Terrace Deposits Research Articles

Aeolian imprints of multiple Mediterranean invasions of the Black Sea during Pleistocene

Climate changes determined the repeated connections between the Black Sea, Caspian Sea and Mediterranean Sea. The landlocked anoxic Black Sea basin was exposed to several transgressions throughout Quaternary by the Mediterranean Sea through the Straits of Istanbul (Bosphorus) and by the Caspian Sea through the Manych-Kerch spillway. Sedimentological records of these connections are limited mostly to the marine terrace deposits of Marine Isotope Stage (MIS) 5e while the pre-MIS 5e period remains uncertain due to a lack of robust facies and chronological data from deep-sea sedimentary sequences. Here we discuss the imprints of multiple Mediterranean transgressions during Middle Pleistocene in the Black Sea based on facies analysis and the optical age of coastal carbonate aeolianites. Contrary to today's hydro-climate of the Black Sea, the aeolianites bear witness to the transformation of the Black Sea into a warm inland sea during successive Mediterranean invasions. Prior to the onset of aeolian deposition, paleosols were formed on the Eocene-aged hardened sandy silts, suggesting strongly washed soil. This is evidenced by no calcium carbonate and a high Rb/Sr ratio, with quartz amounting to of 99.8%. According to our OSL ages, carbonates deposited on the shelf plain under higher temperature and increased evaporation conditions in MIS 15 and the later interglacial phases were transported to the coastal sand dunes during the transitional phases of MIS 15–14, MIS 13–12, MIS 11–10 and MIS 9–8. We suggest that the carbonate-rich and ooid-containing aeolianites were repeatedly formed in the multiple Mediterranean transgression stages, beginning with an increasingly severe dry phase following the Brunhes-Matuyama magnetic reversal. • The aeolianite is a robust record for Mediterranean transgressions of the Black Sea. • The ooid-rich aeolianites was repeatedly formed in multiple transgression stages. • The aeolianites bear witness to the transformation of the Black Sea into a warmer sea.

Geomorphological and sedimentary records of Late Quaternary activities of Qiaojia-Jinyang segment of Lianfeng fault zone, Southwest China

Lianfeng fault zone (LFZ) in Southwest China has great significance for understanding the seismogenic environment, but its nature and latest active age is still poor constrained up to now. The Qiaojia-Jinyang segment (QJS) of LFZ intersects with Jinsha River; so the well-developed river terraces provide a potential spatio-temporal constrains for recent faulting of QJS. Based on investigation of the terrace deposits along river, this paper makes a detailed logging and dating of the faulting and liquefaction of QJS. Combined previous data, the spatio-temporal sequence of the Late-Quaternary river terraces in the area was redetermined. It is considered that the river terraces T1 (lowest) and T2 at QJS (~ 10–20 m and 60–70 m, respectively, above the local river level) are roughly developed in the Middle Holocene and the Late Pleistocene, indicating that the valley along QJS was strongly undercut since the Late Pleistocene. Based on the analysis of the morphological characteristics, spatial distribution, material composition and intersecting relationship between the sand veins and the layers, the strong ground motions is preliminarily detected, which indicates the strong seismic activity of the during the Quaternary. Combined with the faulting characteristics and the dating data of strata within the profiles of terrace deposits, it is considered that the LFZ is active at least at QJS, and the latest active time is not earlier than the Early-Middle Holocene. These findings provide a clear geological evidences for the seismicity assessment at LFZ, and help to the understanding of regional tectonic environment and the prevention of earthquake disasters.

Foundation cutoffs for flood-detention reservoirs

In design and periodic safety reviews of flood-detention reservoirs one of the key issues, in terms of sustainability, affordability and safety, is the need for a positive cutoff through foundation strata to prevent internal erosion. Such strata often involve alluvial or terrace deposits, which are of variable composition and lithology. The authors will describe the considerations that affect the decision as to when a positive cutoff such as sheet piles, or a bentonite cutoff wall is required, and conversely when it can be omitted, with the potential consequences of such an omission. The latter is likely to include additional requirements for surveillance and monitoring. The paper will describe the investigations that are necessary to inform that decision, including desk study, understanding geological context, site-specific intrusive investigations and arrangements for inspections and so on during construction. The paper will conclude with key issues to be evaluated in deciding when a positive cutoff is necessary.

Arsenic Contamination in Groundwater and Potential Health Risk in Western Lampang Basin, Northern Thailand

This research aimed to investigate the spatial distribution of arsenic concentrations in shallow and deep groundwaters which were used as sources for drinking and domestic and agricultural uses. A geochemical modeling software PHREEQC was used to simulate equilibrium geochemical reactions of complex water–rock interactions to identify arsenic speciation and mineral saturation indices based on groundwater quality and hydrogeochemical conditions. In addition, the potential health risk from arsenic-contaminated groundwater consumption was assessed based on the method developed by the U.S. Environmental Protection Agency. The study area is located at the western part of the Lampang Basin, an intermontane aquifer, Northern Thailand. The area is flat and situated in a floodplain in the Cenozoic basin. Most shallow groundwater (≤10 m depth) samples from dug wells were of Ca-Na-HCO3 and Ca-HCO3 types, whereas deep groundwater from Quaternary terrace deposits (30–150 m depth) samples were of Na-HCO3 and Ca-Na-HCO3 types. High arsenic concentrations were found in the central part of the study area (Shallow groundwater: <2.8–35 mg/L with a mean of 10.7 mg/L; Deep groundwater: <2.8–480 mg/L with a mean of 51.0 mg/L). According to geochemical modeling study, deep groundwater contained toxic As(III), as the dominant species more than shallow groundwater. Arsenic in groundwater of the Lampang Basin may have been derived from leaching of rocks and could have been the primary source of the subsurface arsenic in the study area. Secondary source of arsenic, which is more significant, could be derived from the leaching of sorbed arsenic in aquifer from co-precipitated Fe-oxyhydroxides in sediments. Quantitative risk assessment showed that the average carcinogenic risk values were as high as 2.78 × 10−3 and 7.65 × 10−3 for adult and child, respectively, which were higher than the acceptable level (1 × 10−4). The adverse health impact should be notified or warned with the use of this arsenic-contaminated groundwater without pre-treatment.

Geologic Map of the Woodrock Quadrangle, Sheridan and Big Horn Counties, Wyoming

Here we present the results of detailed (1:24,000 scale) mapping of the Woodrock 7.5 Minute Quadrangle Wyoming, which mainly consists of Archean basement rocks of the Laramide Bighorn uplift. Our focus was on the Archean geology of the Laramide age Bighorn uplift. Isotopic age determinations (U-Pb on zircon) were conducted at the University of Arizona LaserChron Center. Our work revealed the presence of four different components of the batholith. The oldest unit is a ~2880 Ma foliated Lookout Mountain Granodiorite that occurs in the southern part of the quadrangle in the vicinity of Bruce and Lookout Mountains. The ~2775 Black Mountain Tonalite occurs in the northeastern part of the quadrangle. The age of the Black Mountain Tonalite and Lookout Mountain Granodiorite overlap but the units are distinct in terms of structure and lithology so they were mapped separately. The central part of the quadrangle is underlain by the massive, ~2860 Ma Taylor Mine Granite. This unit is poorly exposed and variable in texture. The youngest unit is the ~2850 Ma Owen Creek Alkali Feldspar Granite, which occurs in the western part of the quadrangle. Mafic dikes of variable geometry, texture and age cross-cut the quartzofeldspathic rocks. Less than 25 m of poorly exposed Cambrian Flathead Sandstone occurs along the extreme western margin of the quadrangle. We discovered as much as 30 m of Oligocene White River Formation strata occur as terrace deposits along the western side of the Tongue River in the central part of the quadrangle. The White River strata are poorly exposed and consist of thin bedded tuffaceous sandstone and massive conglomerate that are light colors and include as clasts Paleozoic carbonate and Archean basement rocks. Less than 50 m of Pinedale-age glacial tills occur along the upper Tongue River in the southern part of the Quadrangle, forming hummocky, poorly-drained topography. Quaternary alluvium occurs along some of the larger streams.

Geochemistry and Utilization of Water from Thermal Springs of Tawang and West Kameng Districts, Arunachal Pradesh

ABSTRACT The hydrogeochemical studies provide insights about reservoir conditions of geothermal springs along with utilization of thermal waters for domestic, livestock and irrigation purposes. Most of the hot springs of Tawang and West Kameng districts of Arunachal Pradesh emanated through garnet bearing high grade gneissmigmatite-schist-quartzite sequence of the Se La Group, except for Dirang hot springs which emanate from river terrace deposits lying on the footwall of deformed quartzite-phyllite. The thermal waters are of mixed Na-Ca-HCO3-SO4-Cl type, meteoric in origin and at the same time immature in nature, moving sluggishly towards mineral-fluid equilibration zone with slow rock-water interactions. Chemical geothermometry showed wide variation in estimation of sub-surface reservoir temperature and quartz geothermometry model fits prominently to provide the most reliable reservoir temperature varying within 90±40°C. The studies recorded highest reservoir temperature of Thingbu hot spring with 133°C with very high fluoride concentration in all the hot springs except Bishum and Phudung as per BIS (2012) IS: 10500 specifications. High fluoride and sulfate concentration in thermal spring waters make it unsuitable for drinking purpose. The applicability of thermal waters for irrigation is predicted through sodium adsorption ratio (SAR) calculations which showed that waters of Dirang-2, Sorbe and Kitpi-1&2 are not suitable for irrigation purpose due to high salinity and SAR values.

Luminescence dating of cobbles from Pleistocene fluvial terrace deposits of the Ara River, Japan

Constraining the ages of fluvial terraces is essential to understanding fluvial responses to climate and sea-level changes and estimating uplift/incision. Luminescence dating of sand or silt grains from fluvial terrace deposits in Japan is difficult because sand layers are often absent from gravelly deposits, quartz grains are typically dominated by medium/slow components and/or contaminated by feldspars, and short transport distances and short residence times in riverbeds result in poor bleaching of luminescence signals. Luminescence dating of cobbles may overcome these difficulties, but few studies have applied this technique to fluvial terrace deposits. Here, we examine the utility of luminescence dating applied to three granodiorite cobbles from a late Pleistocene fluvial terrace deposit of the Ara River, Japan. We investigated variations of the infrared stimulated luminescence (IRSL) and post-IR IRSL signals with depth in each cobble. The IRSL and post-IR IRSL signals generally increase with depth, indicating that the cobbles were not completely bleached before deposition. Nonetheless, the IRSL ages of the cobble surfaces (19–17 ka) are consistent with the age of a tephra layer (16–15 ka) at the base of loess deposits overlying the terrace. In contrast, IRSL ages of sand-sized feldspar grains overestimate the depositional age because of incomplete bleaching, whereas silt-sized quartz grains greatly underestimate the depositional age, likely because of the thermal instability of the medium component. Our results demonstrate that luminescence dating of cobbles could provide a better understanding of fluvial systems in which luminescence dating of sand grains is difficult.

Paleoenvironmental Evolution of a Forearc in Response to Forcings by Drainage, Climate, Volcanism, and Tectonics: The Quillagua Depocenter, Chile

Abstract The Late Miocene and Pliocene Quillagua depocenter lake system existed in a forearc basin on the west side of the Andes Mountains in northern Chile, alternating between standing-water and salar conditions. Quaternary incision of the Loa River Canyon resulted in bypass of the prior depositional surface and drainage of groundwater from the abandoned depocenter. Systematic regional geological mapping, 32 new chronological constraints on the strata in the basin, outcrop-scale facies analyses, and geophysical data underpin a revised evaluation of the controls on the lake system. The progressive stages, ages, and causes of the Quaternary destruction of the lake system are reconstructed based on mapped distributions of superficial fluvial sediments, chronological studies of terrace deposits, and landform analysis. The lake system occurred at the junction of small catchments draining the slowly rising western Andean foothills and the large paleo-Loa River catchment draining the Andean volcanic arc, during a time span of intense caldera activity. Small magnitude climate variability affected both the hyperarid low elevation sectors and arid upper sectors of the catchments. By 10 Ma, the regional climate was extremely arid, limiting water and sediment to small amounts, and during the Late Miocene and Pliocene, there was no surface-water outlet to the Pacific. Hydrological variations from 9 to 2.6 Ma led to sediment accumulation in variable lake environments, alternating with long hiatuses. Minor deformation within the Quillagua depocenter shifted the topographic axis and groundwater outlets. Simultaneous headward erosion from the Pacific shore captured the Loa River, which triggered large-magnitude incision that persists today. The progression of surface water environmental change was accompanied by changing composition and amount of surface and groundwater, which determined deposition of primary evaporite minerals, extensive diagenesis, and eventually, complex patterns of dissolution expressed as karst.

Age of the Most Extensive Glaciation in the Alps

Previous research suggested that the Alpine glaciers of the Northern Swiss Foreland reached their maximum extensive position during the Middle Pleistocene. Relict tills and glaciofluvial deposits, attributed to the Most Extensive Glaciation (MEG), have been found only beyond the extents of the Last Glacial Maximum (LGM). Traditionally, these sediments have been correlated to the Riss glaciation sensu Penck and Brückner and have been morphostratigraphically classified as the Higher Terrace (HT) deposits. The age of the MEG glaciation was originally proposed to be intermediate to the Brunhes/Matuyama transition (780 ka) and the Marine Isotope Stage 6 (191 ka). In this study, we focused on the glacial deposits in Möhlin (Canton of Aargau, Switzerland), in order to constrain the age of the MEG. The sediments from these deposits were analyzed to determine the provenance and depositional environments. We applied isochron-burial dating, with cosmogenic 10Be and 26Al, to the till layer in the Bünten gravel pit near Möhlin. Our results indicate that a glacier of Alpine origin reached its most extensive position during the Middle Pleistocene (500 ± 100 ka). The age of the MEG thus appears to be synchronous with the most extensive glaciations in the northern hemisphere.

Slip rate deficit partitioned by fault-fold system on the active Haiyuan fault zone, Northeastern Tibetan Plateau

This study focuses on the complexity of fault-fold system developed in the Hasishan section of the Haiyuan fault zone in the northeastern margin of the Tibetan Plateau, along which a 237-km-long coseismic surface rupture zone formed during the 1920 M 8.5 Haiyuan earthquake. Interpretations of satellite imageries combined with field investigations and structural analyses of fault geometry and kinematics reveal that the fault-fold system developed in the Hasishan section are characterized by four main elements (i) the left-lateral strike-slip Haiyuan primary fault F1; (ii) a discrete branch fault F2 with an identical sense of movement; (iii) a tension structure, characterized by a NE-trending normal fault F3 developed in piedmont terrace deposits; and (iv) a compression structure P, characterized by a NW-trending en echelon folds within the Cretaceous–Cenozoic sedimentary sequences including the most recent late Pleistocene–Holocene unconsolidated and/or weakly-consolidated deposits. Previous geologic and geophysical observations show that the slip rate along the whole Haiyuan fault zone is non-uniform, indicating an eastward decrease with a gradient of ∼2.65 mm/100 km. In contrast, the slip rate for the primary fault F1 in the Hasishan section was reported to be 3.2 ± 0.2 mm/yr, ∼3 mm/yr less than the result of 6.2 mm/yr inferred from the slip rate gradient. The finding in this study demonstrates that the fault-fold system consisting of faults F2, F3, and fold P has partitioned ∼3 mm/yr slip within the Hasishan section of the Haiyuan fault zone. This study documents that the slip rates at different sections along the primary strike-slip faults are partially dependent on local geometric structure and fault complexity, and the recognition and analyses of related fault-fold system within large strike-slip fault zone are important for better characterizing the total slip rate budget across primary strike-slip faults, which will contribute to improve seismic hazard assessments.

Selenium Concentrations in Southeastern Missouri Soils and Its Impact on Livestock Nutrition

Selenium is a trace element in animal nutrition provided through forage. Vegetation should accumulate adequate levels to meet this livestock requirement. This study assessed southeastern Missouri soils for their selenium concentrations. Multiple sites across southeastern Missouri were sampled, from which a total of twenty-six soils were collected. Parent materials ranged from coarse to fine-textured alluvium and terrace deposits, colluvium, loess, limestone residuum and rhyolite residuum from poor to well-drained soils. The mean whole soil selenium contents ranged from less than 0.1 mg Se kg-1 for the Kaintuck pedons to 1.0, 2.2, and 2.4 mg Se kg-1 for the Irondale, Killarney, and Frenchmill pedons. For individual soils, Menfro pedons were deep, well-drained soils developed in loess. Paired Menfro pedons having similar soil morphology and having A-E-BE-Bt-C horizon sequences were selected and the greatest selenium concentrations were in the argillic horizons. Soils having fine textures (clayey) had moderate selenium concentrations, whereas soils having coarse textures (sandy) revealed minimal selenium concentrations. A wide soil selenium concentration variation was shown; however, no toxic selenium levels were measured. Therefore, soil selenium toxicity is not a regional issue. Noting that soil selenium concentrations in medium to fine-textured soils are appropriate for providing selenium to livestock, the need to artificially soil incorporate selenium or add selenium into the livestock ration remains critical for coarse-textured soils.

The connections between river terraces and slope deposits as paleoclimate proxies: The Guadalaviar - Turia sequence (Eastern, Iberia Chain, Spain)

This study, focused on the well-exposed terrace deposits of the Guadalaviar and Turia rivers and associated slopes, provides a better understanding of the genetic connection between river-terrace sediments and slope accumulations in a setting influenced by temperate to cold (extraglacial) climates: the Sierra de Albarracín and Alfambra–Teruel depression (Iberian Chain, eastern Spain). The terrace system comprises seven levels, Qt1 to Qt7. In the two older levels (Qt2 and Qt3) lateral connections with thick stratified slope screes were observed. The lower terraces (Qt4 to Qt7) have less expressive slope deposits. New Optically Stimulated Luminescence (OSL) ages, using quartz-OSL and pIRIR290, were obtained from these Quaternary deposits. Qt2 is dated ~310 to 270 ky (Marine Isotope Stage (MIS) 9–8); Qt3 dates from ~175 to 150 ky (MIS 6), Qt4 from ~136 to 80 ky (MIS 5e–a) and Qt5 from ~23 ky (MIS 2); Qt6 has a tufa dated to 10–4.6 ky (early–middle Holocene), while Qt7 probably records the last 4 ky (late Holocene). The thick slope deposits connected with the upper parts of the Qt2 and Qt3 terraces were generated under the cold-climate conditions of MIS 8 and MIS 6, respectively. These are the oldest dated slope deposits connected with fluvial terraces documented in the Mediterranean region, their preservation and recognition thus being of considerable significance. Chronological correlation of the glacial–interglacial cycles of the Pyrenees with the marine isotope stages conforms to the interpretation of paleo-environmental data and sedimentary controls of terrace genesis in extraglacial fluvial basins under temperate- to cold-climatic conditions.

Maximální rozšíření pleistocenního ledovcového štítu ve Vnějších Západních Karpatech a Východních Sudetech – současné znalosti a nový důkaz

A single find of erratic Baltic flint in the Slezské Beskydy Mts. represents a rare evidence of glaciation in the area. The find originates from fluvial deposits of Weichselian valley terrace of the Hluchová Stream, tributary of the Olza River. The erratic was reworked from Elsterian sediments deposited by the Scandinavian Ice Sheet in a very marginal position near its maximum extent in Outer Western Carpathians. Based on morphological analysis, the surface of the erratic was abraded by wave action in the source area on the Baltic shore and subsequently by glacial and (glacio)fluvial transport. Position of the find proves the glaciation of the Olza River valley by a greater ice lobe, than previously assumed.

Large river chronology along the Jinshaan Gorge on the Yellow River and its implications for initialization

The ancient fluvial terrace is one of the keys to understanding how a large river develops in long-term landform evolution. However, surface erosion usually dissects the once extensive terrace into discontinuous segments and makes it difficult to explore the evolution of a large river worldwide. Fortunately, an exception is found in the Jinshaan Gorge of the Yellow River (JGYR), which preserves many Late Miocene-Late Quaternary fluvial terraces and thus can help understand the origin and evolution of a large river. Detailed investigation of the high terraces along the JGYR indicates a broad valley that was later superposed by a V-shaped valley due to rapid incision. To constrain the timeframe in which the broad valley persisted, as well as the onset time of the V-shaped valley formation, we select ten typical fluvial terrace profiles, apply terrestrial cosmogenic nuclide (TCN) 26Al/10Be burial dating to yield the ages of terrace deposits, and correct the results by considering both inherited and postburial nuclide production during slow red clay and loess deposition. Integrated with previous studies of magnetostratigraphic ages, our chronological results show that the lateral erosion and valley widening of the infant JGYR formed a broad valley during ca. 8–3.7 Ma; subsequent downward incision began ca. 3.7 Ma, accelerated to form a V-shaped valley and incising meanders into the initial broad valley since ca. 2.5 Ma. Moreover, most terrace ages plot in either periodic or short-lived arid conditions during ca. 8–3.7 Ma, while a distinctive downward incision has occurred under strengthened oscillating arid conditions since ca. 2.5 Ma, suggesting that climate aridification favours terrace aggradation, and tectonic uplift mainly dominated incision, which was consistent with the onset of the extension of the Shanxi Graben System ca. 8 Ma and the enhanced uplift of the Ordos Block since ca. 3.7 Ma.

Natural conditions of the formation of the monument of Maly Gonbinsky Kordon-2 of the Odintsovo Culture of Altai in the 4th–8th centuries A.D.

The study is aimed at reconstructing the natural and climatic conditions of the Upper Ob River region (south of Western Siberia) in the early Middle Ages (4th–8th centuries A.D.), based on the paleosol data obtained from the fortified settlements of Maly Gonbinsky Kordon-2/11 and Maly Gonbinsky Kordon-2 / 6-3. Settlements are located on the terrace of the right bank of the Ob River. The fortification elements are represented by a horse-shoe-shaped system of a ditch and a rampart, adjacent to the edge of the above-floodplain terrace, inside which there were dwellings and outbuildings. Archaeological investigations of the settlements permitted to study the sediments of the first terrace above the floodplain and to select core samples for palynological analysis. Applica-tion of this method allowed reconstruction of the vegetation during the occupational period of the complex of monuments MGK-2. For interpreting of the actual data, the method of landscape analysis was employed. The need for its application for carrying out paleogeographic reconstructions is warranted by the presence of the relict elements in the morphological structure of the landscapes. To establish their paleogeographic status, within the framework of this study, there was determined the percentage ratio of the amount of pollen and seeds of plants extracted from the deposits of the first above-floodplain terrace, corresponding to the existence of the Odintsovo Culture and belonging to different ecological groups. As the result, the dominance of sparse birch forests and forb dry meadows in the landscape structure of that time was established, whereas the vegetation associations featu-ring pine forests were in the status of progressive elements of the landscape structure. Also, supersedence of birch forb forests by green moss pine forests was revealed. The use of the landscape approach allowed recon-struction of natural conditions of the territory occupied by the complex of fortified settlements of MGK-2. On the basis of the digital elevation model, 3D visualization of the surface of the sediments overlapping the cultural layer of the monuments was rendered, which shows the location of the objects at the lowest elevations of the surface I above the floodplain terrace and the effects of the surface water flow. This necessitated construction of a drai-nage system, the main elements of which might be represented by shallow ditches.

Microstructure and Dispersive Characteristics of a River Nile Terrace Deposit from Northern Sudan

The microstructure of low plastic highly dispersive sandy silty clay (CL) deposit obtained from the terraces of the River Nile in Northern Sudan was studied using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) in relation to its dispersive characteristics. The study showed that the silt size of the CL is mostly aggregates of clay particlescemented by organic matter and iron oxide bonds. Kneading experiments have shown that these aggregates are unstable and could be broken by kneading and compaction. Pinhole tests on specimens prepared at wide ranges of density and water content and kept for different curing times (hours to one year) have shown that neither water content, density andcuring times have pronounced effect on the dispersivity and erosion characteristics of the tested soil.

РЕЛЬЕФ И ОТЛОЖЕНИЯ ПОЗДНЕКАЙНОЗОЙСКОГО ВРЕМЕНИ СЕВЕРО-ЗАПАДНОЙ ЧАСТИ ЦЕНТРАЛЬНО-ЯКУТСКОЙ РАВНИНЫ И СОПРЕДЕЛЬНОЙ ТЕРРИТОРИИ ВОСТОЧНО-СИБИРСКОГО ПЛОСКОГОРЬЯ (ЛИСТ Q-51)

The so-called “watershed coarse gravels” of the Neogene were preserved within the development of heterochronous denudation peneplanation planes. Based on the comparison of paleontological data with the global eustatic Hague-Weil curve, a ladder of denudation levels is constructed. According to the latter, the age of alluvial are determined. Correlation of the deposits of erosion-accumulative terraces in the conditions of the Munsky neotectonic uplift with alluvium in the valley of the Lena is realised. For the latter, the Late Neo-Pleistocene-Holocene age is substantiated and separate geomorphological unit is proposed. The conclusion is made about the weak notion substantiation on the dammed origin of the Mavrinskaya Formation and its age range, the significant role of subaeral processes in its formation in the interval of the Samarovo-Muruktinskoye time is assumed.

Exomorpholithogenesis of the Selenga River delta at the present stage of the hydroclimatic cycle

The materials of complex interdisciplinary studies of the relief forming in different periods of water availability in the Selenga River delta are presented since the technogenic level rise of Lake Baikal. Four water and sediment runoff anomalies, synchronous with water level fluctuations in the Lake are identified. The current boundaries of the Selenga River mouth area (RMA), floodplain complex, flooding territories in the maximum water ability conditions are identified. The RMA covers the territory from the main channel bifurcation nod to Lake Baikal, includes subaerial and subaqueous parts of the protruding delta, the interaction zone fluvial processes and different-aged terraces deposits and adjacent lagoons Proval and Cherkalov Sor. Semi-empirical models and data on the water runoff and sediment yield are presented.

SMALL-AMPLITUDE DISCONTINUOUS DISTURBANCES IN PLEISTOCENE DEPOSITS OF THE VOLYN-PODILSKA UPLAND

The paper presents the results of the study of the small-amplitude discon¬tinuous disturbances of the possibly cryogenic (thermokarst) origin. The dislocations were found in the outcrops of Middle and Upper Pleistocene sediments of the Volyn-Podilska Upland, accumulated in periglacial or sub-periglacial conditions. The distur¬bances are represented mostly by the micro-normal faults and also by sheared fractures and are very similar to tectonic (seismogenic) discontinuities. The tectonotypic fractures in the near-surface deposits of the Pleistocene terraces of Western Bug and Styr (five sections within Volhynian Upland, four of them – in the valley of Bug), as well as in the cover of the Late Pleistocene sediments on the slope of the valley of Dniester (Galician Prydnisterya) are subjected to consideration, analysis and interpretation. In the last location the ruptures are represented mostly by the dis¬turbances identified as sheared fractures. In all others there are small-amplitude normal faults. One reverse fault, timed to an ice-wedge cast, was also revealed. Typical micro-normal faults of all sections are steep and have a number of other common features, which testifies to the same or almost identical mechanism of their formation. These features, in particular, are as follows: 1) insignificant (usually up to 2–2.5 m) length in cross-section and small (several centimeters) amplitude of displacement along the rupture plane; 2) gradual attenuation of the fractures up and down the section. All micro-normal faults are confined to sediments (thicknesses) that are partially or completely composed of sand. The formation of the micro-normal faults and other examined ruptures can be ex¬plained by the uneven compaction and the gravitational subsidence of the rocks, and in the section on the slope of the Dniester valley – also by their displacement down along the slope. It is probable that these processes occurred due to: 1) the degradation of the permafrost; 2) the dehydration of the sand deposits during a significant decrease in the groundwater levels; 3) the melting of the buried layers and lenses of snow, which were accumulated during the winter season in the thickness of sandy the niveo-aeolian deposits. In the outcrops of this terrace, they occur no less frequently than the confidently identified ice wedge pseudomorphs. Key words: small-amplitude disturbances; microfaults; thermokarst; Volyn-Podilska Upland.

Response of terrace deposit thickness to climate change and tectonic deformation: An example of the Liyuan River in the Northeast Tibetan Plateau

AbstractThe relationships between tectonics, climate and sedimentation are important for understanding landscape evolution. In order to elucidate these relationships, we conducted a detailed survey of the thickness of terrace deposits and the altitude of terrace surfaces along the Liyuan River valley, in the Northeast (NE) Tibetan Plateau. We have dated the formation ages of terraces T3 and T4 to 42 ± 3.2 and 93.7 ± 7.5 ka, respectively, using optically stimulated luminescence (OSL) method. By compiling the deposit thickness of terraces, palaeoclimate records and local tectonism, we found that variations in precipitation account for the temporal differences in thickness/rates of sediment deposition in terraces T4 and T3. However, the spatial distribution of terrace deposit thickness was determined by tectonism, including faulting and folding, which changed the local base level. In order to maintain a foreland‐ward‐dipping gradient, the Liyuan River adjusts its sedimentary processes via spatially differentiated aggradation.