Fluvioglacial Processes Research Articles

MICROMORPHOLOGICAL AND MORPHOSCOPIC PARAMETERS OF SAND GRAINS AS INTERPRETATION INDICATION OF THE GENESIS OF KINBURNSKA ARENA

The Кіnburnska arena is one of the seven sand massifs of the Oleshkivsky Sands (Oleshia). In order to clarify the genesis of the relief forms of the Kinburngska аrena and in general the formation of the territory of the Oleshkivsky Sands, a map-scheme of the types of relief forms of the Kinburnska arena is presented for the first time. Another goal of this research was to find out the priority of fluvial or аeolian processes in the formation of arena landforms. In this regard, for the first time, micromorphological and morphoscopic studies of sand grains from deposits of hilly landforms were conducted here. The typology of landforms showed the geomorphological diversity of the arena and evidenced the manifestation of specific, here and there unique landforms. Unique for the territory of Europe here are discrete parallel ridges of the south of the arena, which are a manifestation of giant ripples (diluvial dunes). The author examines their formation in the context of the diluvial paradigm, in particular in relation to fluvioglacial processes at the end of the Pleistocene and flood-overflow processes in the Holocene. The specific formations of the arena here include ridges and depressions formed as a result of the flow of water masses from the water area of the Dniprovsko-Buzkyi liman to the Black Sea (western part of the arena), as well as its Yagorlytskyi Bay (eastern part of the arena). The analysis of the parameters of sand grains from the deposits of various geocomplexes of the Kinburnska arena showed the predominance of weakly rolled grains, as well as the dominance of bugor and bugor-stepped texture of the surface sand grains with almost universal development of micro- and nanoforms on their surface. The typology of the relief forms of the arena and the interpretation of the parameters of the analyzed sand grains proved the dominant role of fluvial processes in the formation of the relief of sandy deposits of the Kinburnska arena and the subordinate importance of aeolian processes.

Paraglacial transformation and ice‐dammed lake dynamics in a high Arctic glacier foreland, Gåsbreen, Svalbard

AbstractThe structural change of the Svalbard landscape from glacially dominated to paraglacial, that has taken place since the termination of the Little Ice Age (ca. 1900) is expressed by the widespread retreat of glaciers and progressive exposure of glacial landforms. This study provides insights into the rate of post‐LIA deglaciation and associated paraglacial transformation in the foreland of Gåsbreen, one of the first ever investigated glacier systems in the Arctic. Glacier is situated in Sørkapp Land (Southern Spitsbergen), a region characterized by one of the fastest deglaciation rates in the entire Svalbard Archipelago. During the investigated period, 1938–2020, the Gåsbreen was in a recession that accelerated after 1990, leading to its foreland increasing from 2.2 to 5.8 km2. The dynamics of landscape change in the glacier foreland, exposed since the end of LIA, manifested in i.e. the formation of ice‐dammed lakes, degradation in the surface of ice‐cored moraines and the landforms that are underlain by dead‐ice. Mass movements and debris flow on ice‐cored moraines and fluvioglacial processes had a great influence on this transformation. Enhanced proglacial runoff intensified denudation, transport and accumulation of sediments, which resulted, in: an increase in the extent of sandurs and proglacial riverbeds, an increase in the area of glacial lakes, extending and changing of the course of rivers in the glacier foreland. At the same time, the major lake system in the area—Goësvatnet underwent several cycles of filling and draining, often through glacial outburst flooding events.

Contemporary and past aeolian deposition rates in periglacial conditions (Ebba Valley, central Spitsbergen)

Quantitative measurements of aeolian activity at high latitudes are not currently carried out on a large scale, even though these processes are important elements of the geomorphic system of polar regions, which are particularly affected by climate change. This study presents the results of aeolian deposition rates measured and calculated for one of the central Spitsbergen postglacial valleys (Ebba Valley). The results are based on seven summer season field campaigns (2012–2018), as well as on AMS 14C and OSL dating of niveo-aeolian and aeolian sediments. Contemporary mean aeolian deposition rates ranged from 0.1 to 22.9 g·m−2·day−1 over selected parts of the valley and averaged from 2.1 to 12.3 g·m−2·day−1 over the studied summer seasons. Interestingly strong relationships (r2 = 0.71, p = 0.017) between mean air temperature and mean aeolian deposition were observed, possibly indicating the importance of the source material delivered to the valley by fluvioglacial processes. Moreover, aeolian deposition dependence on the source material reflected in the local nature of the process was observed. Niveo-aeolian deposition rates were estimated for the period since the 11th century, through the Little Ice Age, till the second half of the 20th century and revealed a rather constant value of 0.05 cm per year. Since then, the niveo-aeolian deposition rate has significantly increased and equalled 0.3 cm per year, which may be related to rising air temperatures and associated pan-Arctic environmental changes.

Mapping of major river terraces and assessment of their characteristics in Upper Pindar River Basin, Uttarakhand: A geospatial approach

In the present paper, an attempt has been made to trace out the major terraces and analyse their characteristics in the Upper Pindar valley of the Uttarakhand state. The study is based on digital elevation model (DEM), satellite data-based terrain characterisation with field and ground truth investigations. The results are derived from the data, which shows the preservation of river terraces along the trunk and tributary streams of the Pindar River. The terraces are formed because of the combined effect of local structural, geological, lithological, and tectonic control along with the climatic influence on landform development. Among the eight surveyed terraces, seven are cut and fill type and influenced by climate, tributaries, formed by both glacial and fluvio-glacial processes, whereas the rest terrace is developed because of tectonic uplift and creates a strath type. The terrace of Upthar and T3 of Langari has gone through the past tectonic events operated within this region. The analysis through cross-section profiles also exhibits the fact that the Upper Pindar basin has experienced a maximum of three stages of terrace development during different phases of the Holocene period and Late Pleistocene period. The alternative river aggradation, degradation, local landsliding, and a sudden increase in sediment flux caused by the monsoonal surge, tectonic uplift, and rapid incision in three separate times are the prime factors that are responsible for the generation of maximum three-tiered terrace landform in the study area. The sequence of terrace development reveals that the trunk of the Pindar River creates the highest number of terraces followed by the tributary rivers, which are generated in the later phase. The three phases of river aggradation in 33.5 ka, 17.5–13 ka, and 8–3.6 ka separated by a deep incision of different timescale are remarkable in this area, mainly around Langri and Khati, which creates the ordering of a maximum of three levels of terrace development. The results concluded that the dominance of local processes plays a vital role in the formation and characterization of river terraces in the Upper Pindar valley. The present study gives a detailed idea of the valley development and the result can also be used as an identification of suitable areas for human interactions with the environment.

SPECIALLY PROTECTED NATURAL AND TECHNOGENIC TERRITORIES OF THE KIROV REGION

The article presents comprehensive data on one of the nature monuments of the Kirov region under the name “Zhukovlyansky sandstone spherical concretions”. The status of a specially protected natural area of local importance was granted to it in 2017 due to the presence of clusters of spherical geological bodies of human size, which give the area a very scenic view. They were discovered during the quarrying of gravel and sand materials in the early 80-s of the last century and soon became a reason to put forward various hypotheses regarding the time and methods of their formation. The latter was the motivation for this publication, which is based on field and laboratory geological and soil-geochemical studies carried out by the authors in 2014-18. The results below give an idea of the peculiarities of the spatial structure, component composition and properties of local geosystems, the time of formation of their lithogenic basis, scientific and cognitive, tourist-recreational importance and problems of preservation of the original natural heritage of the region under consideration. From the genetic point of view, the spherical sandstone concretions located within the paleolacial province of the Vyatka Territory are treated by the authors as native Permian formations, not affected or slightly affected by fluvioglacial processes at the Pleistocene stage of geological development. They serve as a basis for the designation of a special category of protected areas on Vyatka land - natural and man-made monuments - as an example of spontaneous creation of nature and man.

Gems and Placers—A Genetic Relationship Par Excellence

Gemstones form in metamorphic, magmatic, and sedimentary rocks. In sedimentary units, these minerals were emplaced by organic and inorganic chemical processes and also found in clastic deposits as a result of weathering, erosion, transport, and deposition leading to what is called the formation of placer deposits. Of the approximately 150 gemstones, roughly 40 can be recovered from placer deposits for a profit after having passed through the “natural processing plant” encompassing the aforementioned stages in an aquatic and aeolian regime. It is mainly the group of heavy minerals that plays the major part among the placer-type gemstones (almandine, apatite, (chrome) diopside, (chrome) tourmaline, chrysoberyl, demantoid, diamond, enstatite, hessonite, hiddenite, kornerupine, kunzite, kyanite, peridote, pyrope, rhodolite, spessartine, (chrome) titanite, spinel, ruby, sapphire, padparaja, tanzanite, zoisite, topaz, tsavorite, and zircon). Silica and beryl, both light minerals by definition (minerals with a density less than 2.8–2.9 g/cm3, minerals with a density greater than this are called heavy minerals, also sometimes abbreviated to “heavies”. This technical term has no connotation as to the presence or absence of heavy metals), can also appear in some placers and won for a profit (agate, amethyst, citrine, emerald, quartz, rose quartz, smoky quartz, morganite, and aquamarine, beryl). This is also true for the fossilized tree resin, which has a density similar to the light minerals. Going downhill from the source area to the basin means in effect separating the wheat from the chaff, showcase from the jeweler quality, because only the flawless and strongest contenders among the gemstones survive it all. On the other way round, gem minerals can also be used as pathfinder minerals for primary or secondary gemstone deposits of their own together with a series of other non-gemmy material that is genetically linked to these gemstones in magmatic and metamorphic gem deposits. All placer types known to be relevant for the accumulation of non-gemmy material are also found as trap-site of gemstones (residual, eluvial, colluvial, alluvial, deltaic, aeolian, and marine shelf deposits). Running water and wind can separate minerals according to their physical-chemical features, whereas glaciers can only transport minerals and rocks but do not sort and separate placer-type minerals. Nevertheless till (unconsolidated mineral matter transported by the ice without re-deposition of fluvio-glacial processes) exploration is a technique successfully used to delineate ore bodies of, for example, diamonds. The general parameters that matter during accumulation of gemstones in placers are their intrinsic value controlled by the size and hardness and the extrinsic factors controlling the evolution of the landscape through time such as weathering, erosion, and vertical movements and fertility of the hinterland as to the minerals targeted upon. Morphoclimatic processes take particular effect in the humid tropical and mid humid mid-latitude zones (chemical weathering) and in the periglacial/glacial and the high-altitude/mountain zones, where mechanical weathering and the paleogradients are high. Some tectono-geographic elements such as unconformities, hiatuses, and sequence boundaries (often with incised valley fills and karstic landforms) are also known as planar architectural elements in sequence stratigraphy and applied to marine and correlative continental environments where they play a significant role in forward modeling of gemstone accumulation. The present study on gems and gemstone placers is a reference example of fine-tuning the “Chessboard classification scheme of mineral deposits” (Dill 2010) and a sedimentary supplement to the digital maps that form the core of the overview “Gemstones and geosciences in space and time” (Dill and Weber 2013).

Investigating the volcanic versus aqueous origin of the surficial deposits in Eastern Elysium Planitia, Mars

The Elysium Volcanic Province consists of numerous overlapping flow units and may include the youngest lava flows on Mars. However, it is possible that these volcanic units have been modified or overprinted by aqueous processes. Understanding the timing of the igneous and aqueous events in this region is therefore essential for constraining the geological and environmental history of Mars during the Amazonian Period. We investigate the geologic evolution of Eastern Elysium Planitia to determine the relationship between major units, with the support of a geological map and chronological constraints from crater size–frequency distributions. We also evaluate the hypothesized origin of these units via volcanic, fluvial, and/or fluvioglacial processes using a detailed facies-mapping approach. The study area includes the Eastern Cerberus Fossae, Rahway Valles, and Marte Vallis. The surficial deposits in Rahway Valles were formerly interpreted to be modified by fluvial and fluvioglacial processes. However, our facies map reveals that the surface of Eastern Elysium Planitia includes nineteen morphologically distinct regions (i.e., facies), which are interpreted to be the products of flood lava volcanism, including: ʻaʻā, pāhoehoe, and transitional lava flow types. In contrast to previous studies, which determined that Rahway Valles and Marte Vallis consist of two distinct geologic units with Middle to Late Amazonian ages, the results of this work show that the region was resurfaced by at least two volcanic flows with much younger ages of 20.0 Ma and 8.8 Ma. Furthermore, by coupling results of our geologic and facies mapping with chronological constraints as well as subsurface information provided by Shallow Radar reflectors, we show that there is an erosional unconformity located between the two youngest lava flow units in Marte Vallis. We interpret that this unconformity was generated by a catastrophic aqueous flooding event that occurred only 8.8 − 20.0 Ma ago. This implies alternating episodes of volcanism and aqueous flooding that have continued into the geologically recent past on Mars, and may again occur within Elysium Planitia.

Structural and textural response to dynamics of fluvioglacial processes of the Rzymsko esker sediments, Central Poland

The study was conducted in the Rzymsko esker, in the Eastern part of the Turek Upland Plain, within the range of the Warta Glaciation (Saalian II). The form was accumulated in a tunnel valley, which was partially filled with esker sediments. Lithofacies analysis, extended by a detailed analysis of clasts, made it possible to identify a considerable variability of sedimentation conditions. At the initial stage, transport and accumulation of sediments took place in the conditions of high energy hydraulic flows or hyperconcentrated flows. The flow energy rose cyclically, which was recorded as sediments coarsening. Deposits of boulders as well as massive and cross-bedded gravels were identified, a record of catastrophic glacial floods. During the later stage of esker formation, sandy and gravelly sediments were accumulated in an open crevasse. The strong erosional force of subglacial water is confirmed by an extremely high content of local rocks in the gravelly fraction (30–87%) and its very good roundness. Zingg shape analysis (1935) revealed a clear predominance of oblate forms among local clasts and equant fennoscandian erratics. A dependency was also found between the processing method and petrographic characteristics.

Integrated geophysical-geological model for seismic local site response: the Caldes alpine slope case (Southern Alps, NE Italy)

We present the seismic local response analysis of an alpine slope based on an integrated geophysical and geological model. The studied site is located in Caldes, in the lower Val di Sole valley in the Trentino region, Southern Italian Alps. Caldes represents the typical alpine valley formed by glacial and fluvio-glacial processes characterized by complex geomorphological, lithological and tectonic settings. A detailed reconstruction of the valley slope geology (subsoil geometry and stratigraphy) was obtained using electrical tomography resistivity soundings, controlled source multi-channel analysis of surface waves, microtremor single station measurements, borehole investigations, and geotechnical analyses on undisturbed samples. The geological model was shaken with real accelerometric series to obtain 1D (linear equivalent approach) and 2D (finite element approach) local seismic responses. The results, considering the uncertainties of the geophysical measurements, show different seismic responses between 1D and 2D approaches due to relevant geometrical amplifications, with clearer variations in the 2D approach. The comparison of the results with the building code design spectra shows the limits of the simplified approaches, suggesting that detailed characterizations are necessary, especially for such populous alpine environments.

Climate-induced changes in sediment supply revealed by surface exposure dating of Sijiquan River terraces, northeastern Tibet

In this paper, we report cosmogenic isotope evidence for dramatic changes in sediment supply during glacial–interglacial climatic cycles in the Late Quaternary. Previous work on fluvio-glacial processes in cold environments has qualitatively revealed that significant increases in debris production occurred in glacial periods, due typically to accelerated glacial and periglacial processes on high-relief slopes, resulting in river aggradation (accumulation) in the drainage. In interglacial periods, rivers behave in the opposite way, forming incised valleys. However, little has been studied on climatically controlled production-and-reworking processes with radiometric evidence. The evidence presented here is from the northeastern margin of the Tibetan Plateau, where lateral growth of the plateau is now ongoing. Reconstructions of fluvial response to Quaternary glacial fluctuations are crucial also to better understand the active tectonic process in the region using geomorphological information. The Sijiquan River drainage basin on the north of the East Kunlun Mountains was investigated. Detailed geomorphological mapping of fluvio-glacial landforms indicates two phases of aggradation, each of which was followed by valley incision. 10Be and 26Al concentrations in fluvial terrace deposits suggest that these two aggradational phases correspond most likely to the penultimate and last glacial periods, assuming a low rate of surface erosion on the terraces and zero inherited concentration. On the other hand, present-day river gravel has higher concentrations in amalgamated samples of 10Be and 26Al than the terrace deposits. Surface-exposure and burial analyses based on grain-by-grain measurements of both 10Be and 26Al indicate that the present-day river gravel consists mostly of reworked grains from terrace deposits and underlying fluvio-lacustrine rocks in the drainage basin. It is concluded that significant changes in clastic sediment supply occur in cold environments in response to glacial–interglacial cycles; clastic sediments are transported from mountain slopes much more directly in glacial periods than in interglacial periods. This violates the common assumption for surface exposure dating that the inherited cosmogenic isotope concentration is constant through time.

Oksyvos kultūra dešiniajame žemutinės Vyslos krante

Oksyvos kultūra, kaip nauja vėlyvojo ikiromėniškojo gele­žies amžiaus archeologinė kultūra, susidarė dėl keltų pasau­lio įtakos bei Pševorsko ir Jastorfo kultūrų impulsų III a. prieš Kr. (A1 periode). Kultūros vardas kilo nuo vietovės Oksywie (Oxhцft), šiandieninio Gdynės miesto dalies, apie 10 km į šiaurę nuo Gdansko, kur buvo atidengtas šios kul­tūros kapinynas. Pradžioje ši kultūra užėmė visą dešiniąją žemutinės Vyslos pusę ir sritį prie Chełmno (Kulmo). Kla­sikiniame periode A2 kultūra užėmė ir sritį Pomeranijoje. Archeologinių šaltinių duomenimis, čia buvo įsikūrusios vietinių gyventojų grupės – Pomeranijos kultūros tęsėjos. Dėl materialinės kultūros pokyčių ir galbūt gotų diktuoja­mų laidojimo papročių iš Oksyvos kultūros ikiromėniškojo laikotarpio A3 periodo pabaigoje ir romėniškojo laikotarpio B1 periodo pradžioje išsivystė Wielbarko kultūra. Archeologinę medžiagą, reprezentuojančią Oksyvos kul­tūrą šioje Vyslos srities dalyje, sudaro archyvinė medžiaga (apie radinius, aptiktus iki Antrojo pasaulinio karo) ir archeo­logijos paminklai. Svarbiausią grupę tarp prieškario kolekcijų sudaro archyvinė medžiaga, kurią surinko Waldemaras Hey­mas (Heym). Šis žmogus į archeologijos istoriją pirmiausia pateko kaip Heimatmuseum Marienwerder vadovas. Dėl Antrojo pasaulinio karo maišaties didžioji W. Hey­mo rinkinio dalis yra negrįžtamai dingusi arba išbarstyta. Likusi tik informacija apie pavienius artefaktus. Naujausi archeologiniai rinkiniai yra tik prieškario medžiagos papil­dymas. Jie nėra svarbiausia šio Vyslos srities regiono Oksy­vos kultūros kolekcijos dalis. Turimas medžiagos rinkinys reprezentuoja Oksyvos kul­tūrą visu ikiromėniškuoju laikotarpiu, t. y. nuo periodo A1 iki periodo A3. Dalis rinkinio yra iš to laikotarpio kapinynų, kaip antai Bystrzec (buv. Weisshof, Kreis Marienwerder) arba Stary Targ (buv. Altmark, Kreis Stuhm). Kapai, ku­riuose rasta ginklų (ietigalių, kalavijų, antskydžių), yra ypač svarbūs, tačiau jie žinomi tik iš A2 periodo ir A3 periodo baigiamosios stadijos. Iš minėto laikotarpio ankstyviausio horizonto galima kalbėti apie Pomeranijos varpinius kapus ir Jastorfo kultūros įtaką. Geriau pažįstama Pševorsko kul­tūros įtaka, ypač Oksyvos kultūros puodininkystei. Suma­nymas nustatyti Oksyvos kultūros gyvenviečių chronologiją pagal išlikusią medžiagą ir kaupiamą informaciją, kuri dau­giausia fragmentiška, yra sunkiai įvykdomas. Kitu atveju tai klausimas, į kurį turėtume atsakyti. Oksyvos kultūros arheologinė medžiaga iš šitos Vakarų Prūsijos srities yra svarbi bendram Oksyvos kultūros pa­veikslui identifikuoti, ji reikšminga ne tik šiam Vyslos re­gionui.Iš vokiečių kalbos vertė Mykolas Michelbertas

Late Quaternary landscape development at the margin of the Pomeranian phase (MIS 2) near Lake Wygonin (Northern Poland)

In Central Europe, Late Quaternary landscapes experienced multiple phases of geomorphologic activity. In this study, we used a combined geomorphological, pedological, sedimentological and palynological approach to characterize landscape development after the Last Glacial Maximum (LGM) near Lake Wygonin in Northern Poland. The pedostratigraphical findings from soil pits and drillings were extrapolated using ground-penetrating radar (GPR) and electric resistivity tomography (ERT). During the Pomeranian phase, glacial and fluvioglacial processes dominated the landscape near Lake Wygonin. At the end of the glacial period, periglacial processes became relevant and caused the formation of ventifacts and coversands containing coated sand grains. At approximately 15,290–14,800calyrBP, a small pond formed in a kettle hole (profile BWI 2). The lacustrine sediments lack eolian sand components and therefore indicate the decline of eolian processes during that time. The increase of Juniperus and rock-rose (Helianthemum) in the pollen diagram is a prominent marker of the Younger Dryas. At the end of the Younger Dryas, a partial reshaping of the landscape is indicated by abundant charcoal fragments in disturbed lake sediments. No geomorphologic activity since the beginning of the Holocene is documented in the terrestrial and wetland archives. The anthropogenic impact is reflected in the pollen diagram by the occurrence of rye pollen grains (Secale cereale) and translocated soil sediments dated to 1560–1410calyrBP, proving agricultural use of the immediate vicinity. With the onset of land use, gully incision and the accumulation of colluvial fans reshaped the landscape locally. Since 540–460calyrBP, further gully incision in the steep forest tracks has been associated with the intensification of forestry. Outside of the gully catchments, the weakly podzolized Rubic Brunic Arenosols show no features of Holocene soil erosion.

Retroarc deformation and exhumation near the end of the Andes, southern Patagonia

The southern Patagonian Andes constitute the narrow, high-latitude end of the Andean orogen belt in South America, where inherited basin paleogeography, subduction processes, retroarc crustal thickening, and late Cenozoic glaciation have collectively influenced their unusual tectonic and physiographic evolution. New zircon and apatite (U–Th)/He thermochronology from the Patagonian Andes between 50°30′ and 51°30′S suggest concentrated exhumation across the retroarc (leeward) side of the orogen since early Miocene time. Zircon (U–Th)/He (ZHe) ages range from 44 to 10 Ma; oldest ages are recorded in the Patagonian batholith and along the far eastern frontal foreland monocline. Regionally-uniform ZHe ages between 22 and 18Ma, located across a ∼75km wide-zone of the Patagonian retroarc thrust-belt indicate widespread early Miocene cooling through the ZHe partial retention zone. Mesozoic sedimentary and volcanic rocks in this region have been exhumed from at least 5 to 6km depths. Early Miocene denudation of the thrust-belt, deformation, and increased foreland sedimentation rates coincided with opening of the Scotia Sea, suggesting a causal response of the foreland to changes in plate dynamics. The apatite (U–Th)/He (AHe) ages from a similar region range from 11 to 3Ma; the youngest ages (6–3Ma) are spatially clustered within the more deeply-exhumed central thrust domain. We interpret these AHe ages to record >1–2km of erosional denudation associated with late Cenozoic glaciation and fluvioglacial processes in Patagonia beginning ca. 7Ma.Zircon results indicate that since ca. 22Ma, long-term exhumation rates have been highest across the western and central thrust domains (0.22–0.37mmyr−1), and significantly lower along the eastern thrust front (0.10–0.17mmyr−1). Since ∼7Ma, apatite results from these same regions suggest comparable and slightly higher denudation rates (0.14–0.46mmyr−1), particularly within the eastern thrust domain, consistent with efficient erosional processes acting in the retroarc region. These results from the Patagonian retroarc region, particularly the predominance of <7–4Ma AHe ages, provide a new understanding for regional orogenic erosion models that are largely based on existing data from the windward regions. We suggest that retroarc denudation was enhanced by widespread Miocene structural uplift and unroofing of the fine-grained siliciclastic rocks of the marine Cretaceous Magallanes/Austral foreland basin. Furthermore, its location at the southern tip of the orogen, may have allowed additional moisture to reach the leeward side, leading to sustained late Cenozoic erosional denudation.

Precipitation as the main driver of Neoglacial fluctuations of Gualas glacier, Northern Patagonian Icefield

Abstract. Glaciers are frequently used as indicators of climate change. However, the link between past glacier fluctuations and climate variability is still highly debated. Here, we investigate the mid- to late-Holocene fluctuations of Gualas Glacier, one of the northernmost outlet glaciers of the Northern Patagonian Icefield, using a multi-proxy sedimentological and geochemical analysis of a 15 m long fjord sediment core from Golfo Elefantes, Chile, and historical documents from early Spanish explorers. Our results show that the core can be sub-divided into three main lithological units that were deposited under very different hydrodynamic conditions. Between 5400 and 4180 cal yr BP and after 750 cal yr BP, sedimentation in Golfo Elefantes was characterized by the rapid deposition of fine silt, most likely transported by fluvio-glacial processes. By contrast, the sediment deposited between 4130 and 850 cal yr BP is composed of poorly sorted sand that is free of shells. This interval is particularly marked by high magnetic susceptibility values and Zr concentrations, and likely reflects a major advance of Gualas glacier towards Golfo Elefantes during the Neoglaciation. Several thin silt layers observed in the upper part of the core are interpreted as secondary fluctuations of Gualas glacier during the Little Ice Age, in agreement with historical and dendrochronological data. Our interpretation of the Golfo Elefantes glaciomarine sediment record in terms of fluctuations of Gualas glacier is in excellent agreement with the glacier chronology proposed for the Southern Patagonian Icefield, which is based on terrestrial (moraine) deposits. By comparing our results with independent proxy records of precipitation and sea surface temperature, we suggest that the fluctuations of Gualas glacier during the last 5400 yr were mainly driven by changes in precipitation in the North Patagonian Andes.

Geotourism merits of selected inanimate nature objects of Lithuania

The short characteristic of Lithuanian geology is presented, as well as the landforms which are tightly connected to the sediments. The landscape was formed thanks to glacial and fluvioglacial processes. The land is covered mainly by Quaternary sediments. The outcrops of older rocks (Devonian, Jurassic, Cretaceous and Neogene periods) are rather rare. Although there are no mountains on the territory of Lithuania, the geomorphology of the country is differentiated. The kinds of landscape are: morainic hills and plains, wide river valleys, as well as narrow river gullies and many of lakes. One of the most interesting places in Lithuania is the Curonian Spit placed on UNESCO’s World Heritage list. It is full of sandy dunes, the highest in the Northern Europe. Moreover the Curonian Spit is famous for the real Lithuanian treasure – amber. In the article there are also presented some more worth-seeing places, e.g.: Biržai karst area (formed by gypsum and anhydrite rocks), Pakruojis region, well known thanks to the exploitation of Permian limestones and Devonian dolomites, and the large erratics locations.

The role of meltwater in glacial processes

Water plays a dominant role in many glacial processes and the erosional, depositional and climatic significance of meltwaters and associated fluvioglacial processes cannot be overemphasized. At its maximum extent c. 20,000 years ago, the volume of the Laurentide ice sheet was 33 × 10 6 km 3 (about the same as the volume of all ice present today on planet Earth). The bulk of this was released as water in little more than 10,000 years. Pulses of meltwater flowing to the Atlantic Ocean from large ice dammed lakes altered thermohaline circulation of the world's oceans and global climate. One such discharge event via Hudson Bay at 8200 years BP released 160,000 km 3 of water in 12 months. Global sea levels recovered from glacial maximum low stands reached at about 20,000 years ago at an average rate of 15 m per thousand years but estimates of shorter term rates suggest as much as 20 m sea level rise in 1000 years and for short periods, rates as high as 4 m per hundred years. Meltwaters played a key role in lubricating ice sheet motion (and thus areal abrasion) across the inner portions of the ice sheet where it slid over rigid crystalline bedrock of the Canadian Shield. The recharge of meltwater into the ice sheets bed was instrumental in generating poorly sorted diamict sediments (till) by sliding-induced shearing and deformation of overpressured sediment and soft rock. The transformation of overpressured till into hyperconcentrated slurries in subglacial channels may have generated a highly effective erosional tool for selective overdeepening and sculpting of bedrock substrates. Some workers credit catastrophic subglacial ‘megafloods’ with the formation of drumlins and flutes on till surfaces. Subglacial melt river systems were instrumental in reworking large volumes of glaciclastic sediment to marine basins; it has been estimated that less than 6% of the total volume of glaciclastic sediment produced during the Pleistocene remains on land. Fluvioglacial and glaciolacustrine sediments and landforms dominate large tracts of the ‘glacial’ landscape in North America. The recharge of subglacial meltwater into underlying bedrock and sediment aquifers created transient reversals in the long-term equilibrium flow directions of basinal fluids. With regard to pre-Pleistocene glacial record, meltwaters moved enormous volumes of terrestrial ‘glaciclastic’ sediment to marine basins and thus played a key role in preserving a record of glaciation, a record otherwise almost entirely lost on land.

Geomorphological control of gold distribution and gold particle evolution in glacial and fluvioglacial placers of the Ancocala-Ananea basin - Southeastern Andes of Peru

Gold placers are formed as a result of surficial processes but glacial and fluvioglacial systems are generally considered to be unfavourable for placer genesis. Nevertheless, some important glacial and fluvioglacial placers have been discovered and are currently being exploited in the Andes of Peru and Bolivia. In the Plio-Pleistocene Ananea-Ancocala basin (4300–4900 m above sea-level), the gold content of the various formations indicates that only glacial and fluvioglacial sediments related to the Ancocala and Chaquiminas Glaciations (middle and upper Pleistocene) contain gold in any notable quantity. Local concentrations of economic interest occur only where a glacier has cut through a primary mineralized zone. Glacial erosion of dispersed primary mineralizations does not produce high-content placers of the kind found in fluviatile environments. Gold distribution in tills is more irregular than in fluviatile sediments and no marked enrichment at bedrock occurs. The transition from a glacial to a fluvioglacial environment is characterized by an increase in gold content due to a relative concentration of the biggest gold flakes and by the appearance of a gold distribution pattern similar to that found in a fluviatile environment. During their transport by glacial and fluvioglacial processes, gold particles acquire specific features; the size and morphology of a gold flake population are determined by the sedimentological and geomorphological environment in which the flakes are carried.