Intensity Of Denudation Research Articles

Environmental changes recorded in the sequence of lake-peat bogs in the Eemian Interglacial and Vistulian on the basis of multi-proxy data

We present the results of geochemical investigations, including stable isotope, of the Eemian (MIS 5e) and Vistulian (Weichselian, MIS 5a–d, MIS 3–4) sediments of the palaeolake horizons from Gorzów Wielkopolski site (NW Poland). Our analyzes comprised two profiles from different parts of lake basin, each approximately 11-m long. The deposits represent two cycles of lake accumulation (two limnic layers), each ended by peat deposition, separated by mineral fluvial deposits. The lower and upper limnic layers, despite several similar geochemical features, are records of two separate phases of the lake's functioning. The palynological data suggest that the mineral deposits separating them are not continuous succession, but contain a stratigraphic hiatus. We characterized six geochemical zones (GZ), which correspond well with lithological features of deposits and climatic changes, and reflect the changing environmental conditions (redox conditions, variability and intensity of denudation, biological productivity, and fertility of the environment). In the first phase of lake's development, some influence of the surface material supply is visible, indicated by the increased content of lithophilous elements, (e.g. potassium), as well as closely correlated with them copper and zinc. Slow accumulation of carbonates dominated the limnic layers due to their abundant supply from the catchment area. The greatest variations of isotopic values of carbonates occur in the bottom and at the top of the stratigraphic profile and are related to the changing environmental conditions in the lake's basin (water level and temperature variations). The differences in carbon and nitrogen isotope values suggest different sources of organic matter accumulated in the studied basin and varying trophy of the environment. The higher mercury content is related to the course of climate change and is the highest in cold periods. We identified five main phases of evolution of the palaeolake at Gorzów Wielkopolski site. The lake accumulation began during the final phase of the Wartanian (Late Saalian) Glaciation (MIS 6). Initially the palaeolake harmonically developed and reached its maximum depth (Early and Middle Eemian, MIS 5e). Next the palaeolake became shallower and transformed into the peatbog (Late Eemian, MIS 5e). In the Early Vistulian period (or Early Weichselian, MIS 5a–d), the lake re-existed, initially as a flow-through lake. Finally in middle Vistulian (or Middle Weichselian – Pleniglacial, MIS 3–4), the palaeolake declined and mire developed.

Differential post-mineralization thermal evolution of the Jiaodong and Liaodong Areas, Eastern China: An indicator of regional tectonic activity

Post-mineralization thermal evolution is an integral part of the process of formation of ore deposits. However, as two important gold mineralization regions in eastern China, the thermal histories after ore formation of the Jiaodong area is debated while that of the Liaodong area are scarce. Given that the two areas are not only in similar tectonic settings but also have gold deposits that formed in association with the thinning and destruction of the North China Craton, a comparative study can be made. Here new zircon and apatite (U–Th)/He and apatite fission track ages are presented to reconstruct the post-mineralization geological evolution. Four periods of rapid uplift and denudation happening during the 110–100 Ma, 80–70 Ma, 42–38 Ma and 35–32 Ma are defined in Liaodong, and two such periods happening during the 100–95 Ma and 80–72 Ma in Jiaodong. The small timing difference of the rapid uplift (110–100 Ma versus 100–95 Ma) can be explained by the elevation difference of the respective samples. Hence, the evolution processes between the Jiaodong and Liaodong areas are very similar during the Cretaceous, but show marked differences during the Cenozoic. After ore-formation, the erosion amount in Liaodong and Jiaodong is estimated at ∼4.8 and ∼4.7 km, respectively. Moreover, the denudation intensity in Liaodong shows an increase from southeast to northwest. The westward convergence of the Pacific Plate and associated multi-stage activity of the Tanlu and Yalujiang faults are inferred to have induced the regional-scale rapid uplift of the Jiao-Liao areas.

Original

Basin morphometry is a crucial method of analysis to understand the geology, lithological structure, infiltration rate of rainwater, runoff, eroded load carrying capacity and flooding potential of a drainage basin. The quantitative techniques applied for linear, aerial and relief aspects of the drainage basin elucidate the rate of erosion, the intensity of denudation and subsequently the potential of the Nandakini river basin to flooding. The morphometric analysis of the Nandakini river basin in the Garwhal Himalayan region of Uttarakhand reveals that the Rf value of the Nandakini river basin is 0.28, indicating an elongated basin shape leading to quick flooding and poor draining out of floodwaters. Similarly, an elevation difference between the highest and lowest elevation is 5380 metres aids quick runoff and deposition of eroded debris in the drainage channels, another cause of channel overflow. The Rh value is high (0.12), indicating a high channel gradient with intense erosional processes operating due to steep gradient and this has a considerable impact on the rate of erosive geomorphic processes operating. The higher elevation on the Eastern part of the basin due to the Vaikrita Thrust, the Munsiyari Thrust (ie. the southern tilting Main Central Thrust) and the Baijnath Klippe has resulted in metamorphism in Miocene and Pliocene explaining the low rate of infiltration and rapid runoff.

Relationship between geological structure and marine shale gas preservation conditions in the western Middle Yangtze Block

Lower Paleozoic dark shale is developed in the western Middle Yangtze Block, which lays a material foundation for the enrichment and accumulation of marine shale gas. In order to ascertain the control action of geological structures on the differential preservation of shale gas and reveal the key factors in shale gas preservation, this paper firstly analyzed the structure characteristics of this area, carried out structure pattern recognition and structural belt division, and studied structural deformation mode and intensity. Based on this, the relationships between different structure styles and shale gas preservation conditions were analyzed. Finally, combined with the structural deformation and the lithofacies paleogeographic characteristics of marine shale, the favorable exploration zones of shale gas were proposed. And the following research results were obtained. First, the western Middle Yangtze Block can be divided into four structural deformation belts, and three types of piggyback structural patterns have been identified, including restricted type, weakly reformed type and strongly reformed type. Second, the restricted type is located in the northwestern part of Hunan and Hubei Provinces. In this pattern, piggyback structure is incomplete and thrust belt and Compressive fold belt are developed. Third, the weakly and strongly reformed types are located in the western parts of Hunan and Hubei, and Wulingshan area, respectively. They both have complete piggyback structures, but the former has lower deformation intensity and has never undergone the late superimposed reformation. Fourth, there are three structural transfer belts in the western Middle Yangtze Block, i.e. the structural transfer belt between the East Sichuan fault–fold belt and West Hunan–Hubei fault–fold belt, the structural transfer belt between West Hunan–Hubei fault–fold belt and Wulingshan fault–fold belt, and the structural transfer belt between the outcrop and the hinterland of Middle Yangtze Block. The first one is structurally transformed at the Qiyueshan fault. The East Sichuan fault–fold belt on the west is an ejective fold with low fault density and formation denudation intensity, where shale gas is enriched in anticlines and slopes; while the West Hunan–Hubei fault–fold belt on the east is a trough-like fold with strong faulting and high formation denudation intensity, where shale gas is enriched in residual synclines. In conclusion, shale gas preservation conditions of Upper Ordovician Wufeng Formation–Lower Silurian Longmaxi Formation in this area are the best in Zigui syncline, thrust–detachment zone and western margin of Qiyueshan fault. The favorable exploration areas of shale gas of Lower Cambrian Niutitang Formation are distributed in the western flank of Yichang Slope, Kaixian thrust zone, compressive fold zone and thrust–detachment zone.

Karst Denudation Intensity and Climate Change – Case of Lithuania

Karst Denudation Intensity and Climate Change – Case of Lithuania

ИЗМЕНЕНИЕ ИНТЕНСИВНОСТИ ХИМИЧЕСКОЙ ДЕНУДАЦИИ НА ВОДОСБОРЕ РЕКИ ПЕЧОРЫ В УСЛОВИЯХ НЕСТАЦИОНАРНОГО КЛИМАТА И ХОЗЯЙСТВЕННОЙ ДЕЯТЕЛЬНОСТИ

Introduction. Climate warming, which is currently observed in the Arctic, has the potential to intensify chemical denudation in river basins partially or completely located within permafrost. In order to test this hypothesis, we investigated the longterm dynamics of the rivers’ ion runoff in the Pechora River basin, 42 % of which are located within permafrost. Methods. To study changes in the chemical denudation intensity in nonstationary climate, we analyzed data of systematic observations over the main ion concentrations from 1985 to 2017 in the Pechora River outlet (Naryan-Mar) and its tributaries (Usa, Adzva, Kolva, Sula rivers). The intensity of chemical denudation in the Pechora River basin was assessed in terms of ion runoff. The probable reasons for its changes — water content and concentrations of macrocomponents — were also analyzed. Results. The ion-salt composition of Pechora River water is mainly determined by the dissolution of carbonate minerals in the underlying rocks. Calculations and comparison of ion runoff moduli showed that the studied rivers are comparable in terms of the chemical denudation intensity in catchments. The exceptions were the Sula and Kolva rivers, where, with the river runoff, a relatively high amount of chlorides and hydrocarbonates is carried. Contrary to the initial assumptions about the possible intensification of the chemical denudation process under the conditions of climate warming, we found a decrease in the sulfate runoff moduli in all rivers. In addition to that, individual changes in the runoff moduli for other main ions are observed for the studied rivers. Conclusion. In modern conditions, the chemical denudation intensity remains at the level of the end of the last century, and the long-term dynamics of the Pechora River ion runoff correlates in time with the variability of anthropogenic factors, in particular, wet sulfate deposition with atmospheric waters.

Clay mineralogical and geochemical proxies of the East Asian summer monsoon evolution in the South China Sea during Late Quaternary

The East Asian summer monsoon controls the climatic regime of an extended region through temperature and precipitation changes. As the East Asian summer monsoon is primarily driven by the northern hemisphere summer insolation, such meteorological variables are expected to significantly change on the orbital timescale, influencing the composition of terrestrial sediments in terms of both mineralogy and geochemistry. Here we present clay mineralogy and major element composition of Core MD12-3432 retrieved from the northern South China Sea, and we investigate their relationship with the East Asian summer monsoon evolution over the last 400 ka. The variability of smectite/(illite + chlorite) ratio presents a predominant precession periodicity, synchronous with the northern hemisphere summer insolation changes and therefore with that of the East Asian summer monsoon. Variations in K2O/Al2O3 are characterized by eccentricity cycles, increasing during interglacials when the East Asian summer monsoon is enhanced. Based on the knowledge of sediment provenances, we suggest that these two proxies in the South China Sea are linked to the East Asian summer monsoon evolution with different mechanisms, which are (1) contemporaneous chemical weathering intensity in Luzon for smectite/(illite + chlorite) ratio and (2) river denudation intensity for K2O/Al2O3 ratio of bulk sediment.

Denudation intensity and control in the Chinese Tian Shan: new constraints from mass balance on catchment‐alluvial fan systems

AbstractTectonics and climate are usually seen as the main controlling factors of denudation rates, which seem to rise with the tectonic activity and to decrease when the climate becomes drier. However, the low denudation rates observed in semi‐arid to arid contexts are generally measured on orogenic plateaus where the respective influence of the flat relief and the dry climate cannot really be unravelled. The Chinese Tian Shan was chosen as a case study. In the northern piedmont of this mountain range, a series of well‐preserved Quaternary alluvial fans offer the opportunity to perform a mass balance study at the scale of several catchment areas and several hundreds of thousands of years. Based on a geometrical reconstruction of these fans, the volumes of sediments exported out of 10 drainage basins during the Middle–Late Pleistocene (from ∼300 to ∼12 kyr) and the Holocene (from ∼12 kyr to present) have been estimated. From these volumes, an average denudation rate of ∼135 m/Myr was determined in the Tian Shan Range for the last 300 kyr. In agreement with other mass balances performed in the same area, the typical denudation intensity of the northern Tian Shan is thus of a few hundred meters per million years at most, regardless of the space and time scales considered. From a comparison with denudation rates in other mountain ranges throughout the world, we suggest that a dry climate can dramatically limit the denudation intensity even in active orogenic systems with a high topographic gradient like the Tian Shan. As a result, the time required to reach equilibrium between denudation and rock uplift in these systems could be extremely long (i.e. of more than several million years). Copyright © 2016 John Wiley & Sons, Ltd.

Химическая денудация на горной территории Азербайджана

Chemical denudation (dissolved matter runoff) in mountain rivers in comparison with mechanical denudation (sediments runoff) has not yet been properly investigated and remains one of the poorly studied issues of hydrology. Assessment of the chemical denudation intensity in the Azerbaijan mountain regions has been carried out on the basis of the summed up material on ions runoff over the 1980-2013 period. Value of the average annual wash-out from the catchment area (relation of the average annual ions runoff volume to the catchment area) has been used as an indicator of the chemical denudation intensity. The chemical denudation intensity has been made on the basis of the data on the ions runoff transferred by the rivers. The river water ion runoff module dependence on the catchment average height has been obtained. It has been found that the chemical denudation intensity at the Greater and the Lower Caucasus is increasing with altitude. In contrast, in Talysh the chemical denudation intensity is decreasing with altitude. It has been stated that the role of chemical denudation on the territory under study is substantial (22.6 %), its intensity is nearly six times higher the average world value.

Assessing soil erosion hazard in a key badland area of Central Italy

In this work, an integrated methodology was applied to assess the water erosion hazard in Upper Orcia Valley, an area of Southern Tuscany (Italy), greatly affected by severe denudation processes, that caused the development of widespread badlands. Prediction of areas prone to calanchi badland development was carried out by applying a susceptibility assessment method based on conditional statistical analysis, preceded by a bivariate statistical analysis aimed at selecting the most influential causal factors of erosion. Water erosion rates at badland sites were estimated by means of an empirical statistical method, implemented to evaluate the erosion intensity (Tu denudation index) and based on some geomorphic parameters as independent variables. This methodology allows associating the denudation intensity to the spatial prediction. The validation procedure, based on a random partition of calanchi badland areas, confirmed the efficiency of the spatial zonation of the erosion hazard values. Moreover, the comparison of the estimated erosion rates with the results of decadal investigations on denudation processes affecting the study area, performed by different monitoring methods, showed the effectiveness of the estimation model. These results allowed concluding that the proposed procedure represents a useful tool to be applicable for soil protection strategy planning in land management of Mediterranean areas characterized by similar morphoclimatic features, even when direct erosion rate measures are not available.

Denudation rates across the Pamir based on <sup>10</sup>Be concentrations in fluvial sediments: dominance of topographic over climatic factors

Abstract. A clear understanding of erosion processes is fundamental in order to comprehend the evolution of actively deforming mountain ranges. However, the relative contributions of tectonic and climatic factors and their feedbacks remain highly debated. In order to contribute to the debate, we quantify basin-wide denudation rates from cosmogenic 10Be concentrations in modern river sediments in the Pamir. This mountain range is a unique natural laboratory because the ongoing India–Eurasia collision sustains high deformation rates and, on account of its position at the transition between Westerlies and monsoon, a strong regional climatic variability arises. Sample acquisition and preparation for accelerator mass spectrometry measurements were challenging due to difficult field accessibility, low quartz and high feldspar concentrations and crystal coating. Six samples along the main draining river, the Panj, and five samples within the major, east–west elongated tributary basins allow us to quantify basin-wide denudation rates for the first time in this orogen. An average denudation rate of ~ 0.64 mm yr−1 reveals a rapid evolution of the entire Pamir. Denudation rates of tributary sub-basins highlight the strong contrast between the Pamir Plateau (0.05 to 0.16 mm yr−1) and its margins (0.54 to 1.45 mm yr−1). The intensity of denudation is primarily correlated with geometric properties of the surface, such as slope steepness (0.75 quartiles; R2 of 0.81), and to a lesser extent to climatic factors such as precipitation. We thus argue that either tectonic uplift or base-level lowering are the main contributors to denudation processes. Multiple linear regression analysis (best R2 of 0.93) suggests that precipitation may act as a limiting factor to denudation. The highest denudation rates coincide with areas of the northwestern Pamir margin that receive precipitation predominantly from the Westerlies during winter. There, the concentrated discharge during spring and early summer may sustain the pronounced denudation and allow the rapid sediment transport out of the basins. Low slope angles and dry conditions hamper the sediment flux on the plateau and, consequently, denudation. The magnitude of denudation in the Pamir is similar to rates determined in the southern Himalaya despite very different climatic and tectonic conditions. The discrepancy between rates of basin-wide denudation and the fluvial incision that is up to 10 times higher evidences a transient landscape in the Pamir. This underpins the hypothesis that river captures may have caused the strong base-level lowering that drives the enhanced incision of the Panj and its main tributaries.

CATCHMENT FUNNELS (CIRCUS) OF THE SIKHOTE-ALIN AND CHERNOGORIE (PRIMORSKY KRAY)

The description of the morphology of catchment funnels and their distribution within the Sikhote-Alin and Chernogorie is given. These landforms are considered as independent elements of geomorphological zoning in the upper parts of any catchment basin. The main features of quaternary deposits (lithocomplexes) correlated to catchment funnels are considered. Their formation proved to be durable and effected by denudation intensity changes caused by tectonic and climate. The characteristics were determined, which make it possible to distinguish clacial circus from catchment funnels.

A TENTATIVE FOR A WATERSHED MORPHODYNAMICS RECONSTRUCTION IN THE NORTHERN PRIAZOV’E (TEST SITE MELEKINO, DONETSK REGION, UKRAINE)

The loess-soil series structure of Melekino test site was studied in detail in the coastal outcrop and the drill profile. It is possible to reveal specific features of watershed morphodynamics in the Northern Azov region since the Muchkap time (MIS 13, ~ 470-500 kyr). The position of paleosols and textural features of deposits indicate leading role of loess accumulation in the development of watersheds relief before the Valdai glacial epoch. Intensity of denudation was a relatively low at the time. Stage of unique denudation intensity was diagnosed for the Valdai glacial epoch (as follows from indirect data, to its end - MIS 2, ~ 29-12 kyr). The denudation resulted in the development of linear erosion and slope processes even on gentle slopes (2-4 degrees). Analysis of paleosol deformations revealed the specific of watersheds relief evolution during the transitions from interglacial to glacial epochs. We determined that early stages of glacial epochs were characterized by sharp intensification of processes of arid and cryo-arid types. These processes led to the formation of specific micro-knobby surface.

Human impact on Subatlantic slopewash processes and landform development at Lake Jasień (northern Poland)

A survey of the Lake Jasień area (northern Poland) demonstrates the relationship between human economic activity and the course of slopewash processes during the Subatlantic. In the catchment area of the erosional-denudational valley affected by prolonged human economic activity in the early Iron Age (the Hallstatt period) and the pre-Roman period, deforestation may have led to activation of hillslope processes. A manifestation of this activation is a fossil cut in the bottom of the valley and sediments of hillslope origin filling it, lying on top of sediments dated to 450 BC–100 cal. AD. The intensity of the hillslope processes may have been modelled by climate changes involving cooling and humidification.The most recent documented increase in the intensity of denudation occurred around the middle of the 17th century. Deposited on top of sediments dated to 1456 AD–1638 cal. AD and 1453 AD–1797 cal. AD is a sequence of hillslope sediments developed in the form of diluvium and tillage diamicton filling the bottom of the valley and the closed depression.Faster denudation in the landform catchments and accumulation on their bottoms were caused by deforestation of those areas and using them as farmland, as indicated by old cartographic materials. The cooling and humidification of the climate during the Little Ice Age may also have contributed to the acceleration of the agrotechnical denudation. In areas unaffected by deforestation, no noticeable traces have been found of active denudation processes during the Subatlantic. This may suggest that hillslope processes did not play a major role in lowland forested areas of the Temperate Zone.

Paleogeography of the environment in north-eastern Poland recorded in an Eemian sedimentary basin, based on the example of the Jałówka site

The paper presents the results of the research on biogenic sediments from the Jałówka profile (Podlasie region, NE Poland) situated at the foot of a dry valley slope. A 35 cm monolith of sediments was collected from the excavation pit. The sediments were deposited beneath 4 m thick mineral sediments. Interdisciplinary research helped to reconstruct the possible transformations of the local environment. Palynological, physical, and geochemical analyses were applied to organic sediments, and plant macroremains were examined. Five local pollen zones were identified in palynological terms and correlated with the late Warta Stadial (MIS 6) of the Odra Glaciation (Saalian), and four older periods of the Eemian Interglacial: MIS 5e (E1, E2, E3 and E4). Younger zones have not been preserved. They were eroded in the early Vistulian. During the late MIS 6, there was a eutrophic water body with highly transparent water, characterized by a relative stable water level. The landscape was dominated by tundra with a high proportion of Juniperus–Artemisia. Curves of oxygen (δ18O) and carbon (δ13C) stable isotopes confirmed the boundary between MIS 6 and MIS 5e. The beginning of the interglacial vegetation succession (E1) was characterized by expansion of birch–pine–spruce forests. Probably at the end of this period, the lake became shallower. E2 is distinguished by the dominance of pine and birch. The lake was replaced by a peat bog. The sequence of vegetation succession in the landscape was as follows: Quercus (E3), Corylus, Fraxinus-Alnus and Tilia (E4). Probably, the peat bog drained in the E4 and the water level rose again in the climate optimum of the Eemian Interglacial. The results of physical and geochemical analysis clearly corresponded with climatic changes determined by palynological analysis. They provided evidence of the changing redox conditions, variability and intensity of denudation, the scale of biological productivity, and fertility of the environment. The studied sediments were characterized by reducing conditions. The increase in terrigenous silica content and the relatively high N:K ratio indicated the predominance of mechanical denudation during the late glacial period of the Warta Stadial and the E2 period.

Nutrient budgets for large Chinese estuaries

Abstract. Chinese rivers deliver about 5–10% of global freshwater input and 15–20% of the global continental sediment to the world ocean. We report the riverine fluxes and concentrations of major nutrients (nitrogen, phosphorus, and silicon) in the rivers of the contiguous landmass of China and Korea in the northeast Asia. The rivers are generally enriched with dissolved inorganic nitrogen (DIN) and depleted in dissolved inorganic phosphate (PO43−) with very high DIN: PO43− concentration ratios. DIN, phosphorus, and silicon levels and loads in rivers are mainly affected by agriculture activities and urbanization, anthropogenic activities and adsorption on particulates, and rock types, climate and physical denudation intensity, respectively. Nutrient transports by rivers in the summer are 3–4 times higher than those in the winter with the exception of NH4+. The flux of NH4+ is rather constant throughout the year due to the anthropogenic sources such as the sewer discharge. As nutrient composition has changed in the rivers, ecosystems in estuaries and coastal sea have also changed in recent decades. Among the changes, a shift of limiting nutrients from phosphorus to nitrogen for phytoplankton production with urbanization is noticeable and in some areas silicon becomes the limiting nutrient for diatom productivity. A simple steady-state mass-balance box model was employed to assess nutrient budgets in the estuaries. The major Chinese estuaries export <15% of nitrogen, <6% of phosphorus required for phytoplankton production and ~4% of silicon required for diatom growth in the Chinese Seas (Bohai, Yellow Sea, East China Sea, South China Sea). This suggests that land-derived nutrients are largely confined to the immediate estuaries, and ecosystem in the coastal sea beyond the estuaries is mainly supported by other nutrient sources such as regeneration, open ocean and atmospheric deposition.

新潟平野北東縁の活しゅう曲地域にみられる隆起量と侵食様式・削剥強度の関係

This paper discusses the relationships between relief energy and types and intensity of erosional processes in an active folding zone in the northeastern margin of the Niigata plain. It is recognized that there is a positive correlation among relief energy, magnitude of erosional processes and intensity of denudation in areas that have relief energy less than 150 m and are underlain by the upper Miocene mudstones. This relationship suggests that the intense areal denudation in the higher relief zone provides an upper limit of relief energy in the areas of less resistant rocks.In the study area, where denudation is not yet in the equilibrium with uplifting, the relief energy will reflect the amount of uplift. Large amount of uplift is expected to produce large relief energy, and mountainous landscape characterized by large-scale landslide and lack of crest-flats in the southern part of the surveyed area. In contrast with the southern part, in the northern part of the surveyed area, where the amount of uplift is smaller than the southern part, the hilly landscape characterized by the broad crest-flats and numerous gullies are formed in the low relief area.