An aeolian or a glaciolacustrine record? A case study from Mieļupīte, Middle Gauja Lowland, northeast Latvia

In the Middle Gauja Lowland, northeast Latvia, dunes are distributed over a vast glaciolacustrine plain that formed during the retreat of the Fennoscandian ice sheet. Such a direct contact between aeolian and glaciolacustrine sediments can be used to infer depositional settings and decipher to what extent these sediments bear an aeolian component. Our proxies, although preliminary, reveal a limited range of variation in grain-size parameters, a significant presence of quartz grains with silica precipitation and matt-surface grains of various rounding degrees and massive structure combined with horizontal lamination. These are indicative of periglacial-aeolian depositional conditions in the foreland of the Linkuva ice-marginal zone. Sedimentary characteristics do not match a single luminescence date of 9.2±0.6 ka, which significantly postdates the minimum age of the Linkuva ice-marginal zone with 10Be ages between 15.4 and 12.0 ka. Whether deposition started directly after drainage of the Middle Gauja ice-dammed lake or if there is a gap of 2.8–6.2 ka is a matter of debate; only future studies at higher OSL resolution could resolve this

Aeolian activity in Sweden: an unexplored environmental archive

During the course of this three-year project, we have studied aeolian deposits at 70 sites within sixteen areas in south-central Sweden. Inland dunes have been the focus, but some sites with coversand and coastal dunes have also been investigated. We have mapped dune morphology, mainly by LiDAR-based remote sensing, studied the internal sediment architecture by ground-penetrating radar profiling and in sediment exposures, documented the sedimentology of the deposits with field and laboratory methods as well as determined the age of the deposits with luminescence and radiocarbon dating. In this scientific report to the Geological Survey of Sweden, who funded the project, we present a summary of the project and its results. The largest and best developed dune fields are found at glacifluvial deposits in Värmland and Dalarna, while in areas south thereof there are mainly scattered dunes or coversand deposits. A range of dune types has been observed, but transverse dunes seem to be dominating and the majority of these are oriented roughly NE-SW. The bulk of the aeolian deposits were formed shortly after the local deglaciation and, once stabilised, do not appear to have been significantly reworked during the Holocene. Most Mid- and Late-Holocene aeolian deposits consist of coversand, apart from in coastal areas where e.g. young foredunes are found.Our results thus largely confirm the hypothesis of previous investigators but we do add a significant amount of new information. We provide, for the first time for most of our study areas, numerical ages for the aeolian deposits and thus provide the timing and duration of sand-drift events in south-central Sweden. The ages, in combination with detailed geomorphological mapping, allow us to distinguish phases of dune-field development, which are likely due to changes in wind patterns and vegetation cover, and also to correlate Swedish aeolian deposits to regional storminess periods. Based on sedimentological information we are able to reconstruct dominating depositional processes, transport paths and sediment sources. Additional outcomes of the project are e.g. methodological developments (LiDAR mapping, luminescence dating) and pilot studies of potential relevance for applied geology (coastal development)

Quartz grains reveal sedimentary palaeoenvironment and past storm events: A case study from eastern Baltic

Sediment record collected from the coastal lake serves as a powerful tool for reconstructing changes in palaeoenvironment and understanding the potential signals of past storminess. In this study, we use several proxies from sediment of the Holocene Thermal Maximum at coastal Lake Lilaste, Latvia. We focus on surface texture of quartz grains from the mineral inorganic fraction as indicators of depositional environments. We then use this as a proxy for potential storm transport and combine with information on granulometry, diatom stratigraphy and chronology to answer the question whether flux of quartz grains in the lake originated from the sea or from the land. Analyses in a binocular and scanning electron microscope reveal that most of the investigated quartz grains originate from dwelling in the seawater and wave action in the nearshore zone. Grains representing very energetic subaqueous environment similar to storm events are also present. Terrestrial record is of minor significance and visible through occurrence of aeolian quartz grains. During drier and colder conditions, an influx of sand with aeolian imprint was delivered to the lake between 8500 and 7800 cal yr BP. Marine and terrestrial conditions alternated between 7800 and 6000 cal yr BP. Storm-induced grains were likely deposited three times: at 7300 cal yr BP, 6600–6400 cal yr BP, and 6200–6000 cal yr BP. Overall stable marine environmental conditions prevailed between 6000 and 4000 cal yr BP except of the last portion of terrestrial-induced sediment at 4100 cal yr BP

The north-eastern aeolian 'European Sand Belt' as potential record of environmental changes: A case study from Eastern Latvia and Southern Estonia

The Latvian and Estonian inland dunes belong to the north-eastern part of the 'European Sand Belt' (ESB). These dunes are widely distributed over broad glaciolacustrine plains and Late Glacial alluvial deltas, considered to be potential sources for the aeolian material. Little is known about these aeolian sediments and their substratum; here we present a detailed sedimentary structural and textural characterisation together with a luminescence-based chronology. Through a comparison between grain-size, rounding of quartz grains and surface characteristics in medium/coarse (0.5-0.8 mm) sand, and the light mineral content, we found an alternation of aeolian and periglacial components. Further, short-lasting aeolian abrasion and/or transportation periods, and a significant contribution of a nearby sediment source are suggested. Luminescence dating points to aeolian sand accumulation and dune formation between ~16 ka and ~9 ka. However, we also observed some presumably watertable controlled environmental conditions at ~13 ka; this corresponds with the occurrence of an ice-dammed/proglacial lake

Quartz grain features in modern glacial and proglacial environments : A microscopic study from the Russell Glacier, southwest Greenland

Funding Information: and Karol Tylmann, are appreciated. Research was supported by the SIA SunGIS (Edyta Kalińska-Nartiša), by the Post-doctoral Research Project No. 1.1.1.2/VIAA/1/16/118 Comparision of subglacial and ice-marginal formations and processes at the outer zone of the south sector of the Scandinavian Ice Sheet and at the contemporary glaciers in Greenland, Iceland and Antarctica (Kristaps Lamsters) and by the University of Latvia project Climate change and sustainable use of natural resources No. AAP2016/B041. We thank Reinis Pāvils for field assistance. Publisher Copyright: © 2017 Polish Academy of Sciences.It is assumed that close to the margins of ice-sheets, glacial, fluvial and aeolian processes overlap, and combined with weathering processes, produce numerous sediments, in which quartz is a common mineral. Quartz grains, if available, may serve as a powerful tool in determining the depositional history, transportation mode and postdepositional processes. However, quartz grain studies in some modern glacial areas are still sparse. In this study, we examine for the first time quartz grains sampled from the modern glacial and proglacial environments of the Russell Glacier, southwest Greenland in binocular microscope and scanning electron microscope, to analyze their shape, character of surface and microtextures. We debate whether the investigated quartz grains reveal glacial characteristics and to what extent they carry a signal of another transportation and sedimentary processes. Although glacial fracturing and abrasion occur in grain suites, most mechanical origin features are not of a high frequency or freshness, potentially suggesting a reduced shear stress in the glacier from its limited thickness and influence of the pressurized water at the ice-bed. In contrast, the signal that originates from the fluvial environment is much stronger derived by numerous aqueous-induced features present on quartz grain surfaces. Aeolian-induced microtextures on grain surfaces increase among the samples the closest to the ice margin, which may be due to enhanced aeolian activity, but are practically absent in sediments taken from the small scale aeolian landforms. In contrast, aeolian grains have been found in the bigger-size (1.0-2.0 mm) investigated fraction. These grains gained the strongest aeolian abrasion, possibly due to changes in transportation mode.publishersversionPeer reviewe

Microtextural Inheritance on Quartz Sand Grains from Pleistocene Periglacial Environments of the Mazovian Lowland, Central Poland

Sand grains from Quaternary glacial, aeolian and fluvial deposits in the Mazovian Lowland, central Poland, were examined to characterize the effects of different Quaternary processes on sand-grain surfaces that experienced repeated cycles of intense polar-desert-like conditions during the Middle and Late Pleistocene. A cold, dry and windy periglacial environment prevailed here at least twice between the Saalian (Marine Isotope Stage (MIS) 6) and Holocene (MIS 1) stages. Because the surface characteristics of quartz sand grains can provide important palaeoenvironmental information, we examined grains extracted from sediment samples in different landforms to determine their surficial features from scanning electron microscope images. The grain surfaces were dominated by microtextures characteristic of aeolian-induced grain transformation, indicated by a high percentage of well-rounded, low-relief-worn grains with dish-shaped depressions, bulbous edges and upturned plates. Although remnants of previous sedimentary cycles were occasionally observed, aeolian effects were dominant even in glacial and fluvial settings. Quartz microtextures indicated that none of the examined grains represented their original setting, but rather suggested remobilisation under periglacial conditions