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

Nartišs M., Kalińska-Nartiša E.

Geologos

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2017

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Vol. 23, No. 1

15--28

EN

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.

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Roundness and matt degree of quartz grain surfaces in (fluvio-)glacial deposits of the Pomeranian Stage (Weichselian) in northeast Germany

Górska-Zabielska M.

Geologos

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2015

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Vol. 21, No. 2

117--125

EN

Glacial tills and fluvioglacial sediments deposited by the ice-sheet during the Pomeranian Stage (Weichselian) in northeast Germany have been examined in terms of the degree of abrasion, rounding and frosting of quartz grain surfaces in order to determine the conditions and processes that occurred in the alimentation environment of the fine-grained material, as well as during transport. Strata in the glaciomarginal zone and the hinterland of the Pomeranian Stage in the area represent diverse lithofacies, but have similar textural features. These features illustrate mainly that a high-energy aquatic environment had reacted with glacial deposits prior to their inclusion into the ice mass and deposited in the area covered by the Odra lobe. The lack of regional diversification in the character of quartz grain surfaces in glacial deposits between the German part of the Odra lobe and the remainder of the area analysed is recorded solely in the morphological dimension, i.e. the outlet fragment of the ice-front’s course, but not in textural features of the sediments.

3

Structural reconstruction of a fractured fluid reservoir using single quartz grains of drilling chips

Skultéti A, Toth T M, Fintor K, Schubert F.

Geologia Sudetica

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2014

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Vol. 42

86--87

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Heavy and light minerals as a tool for reconstructing depositional environments: an example from the Jałówka site (northern Podlasie region, NE Poland)

Woronko Barbara, Rychel Joanna, Karasiewicz Mirosław T., Ber Andrzej, Krzywicki Tomasz, Marks Leszek, Pochocka-Szwarc Katarzyna

Geologos

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2013

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Vol. 19, No. 1-2

47--66

EN

Part of northern Podlasie (NE Poland), shaped during the Wartanian stadial of the Odranian glaciation (Saalian), was situated in the periglacial zone during the Vistulian (Weichselian) glaciation. Both landforms and sediments were affected by the periglacial conditions. This is recorded at the Jałówka site, at the floor of a dry valley, where mineral deposits of 4.13 m thick, overlying organic deposits from the Eemian interglacial, were examined. These mineral deposits form four units, from bottom to top: a fluvial unit (I), a loess-like unit (II), a solifluction unit (III), and an aeolian unit with ice wedges (IV) on top of unit III. The heavy and light minerals were analysed, as well as the geochemistry, in order to find out about the parent material and to reconstruct the climatic conditions during deposition. The mineral analysis indicates that the Saalian till was predominantly derived from shallow-marine deposits; erosion accompanied by sorting of the heavy minerals took place on the basis of their mass and grain size. The original material of the till seems therefore to be sedimentary rocks from the eastern Central Baltic Basin. This material became strongly weathered under the periglacial conditions, resulting in the destruction of the quartz grains, as well as in leaching, leading to complete decalcification of the deposits. Aeolian activity resulted in infilling of ice wedges and the creation of thin layers. The intensity and the duration of these processes was limited, so that the effects of the aeolian abrasion are insignificant. Neither resulted the aeolian activity in significant reshaping of the landscape.