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Radiocarbon dating of organic-rich deposits: Difficulties of paleogeographical interpretations in highlands of Russian Altai

Nepop R.K., Agatova A.R., Bronnikova M.A., Zazovskaya E.P., Ovchinnikov I.YU., Moska P.

Geochronometria

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2020

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Vol. 47, no.1

138--153

EN

The high mountainous southeastern part of Russian Altai is characterized by complicated sedimentation history. As a result of tectonic movements, Paleogene, Neogene, and even more old Carboniferous and Jurassic organicrich deposits had been partly uplifted and exhumed on the ridge’s slopes, where during the Pleistocene, they were affected by various exogenous processes including glaciation, glacio-fluvial erosion, winnowing activity of ice-dammed lakes, sliding during lake-draining events, followed by further intensive Holocene erosion, pedogenesis, and permafrost formation/degradation. Remobilized ancient organic matter had been involved into geomorphic and pedogenesis processes and affected the results of radiocarbon dating. Numerous radiocarbon ages obtained revealed several typical problems in interpretation of dating results, which was confirmed by multidisciplinary investigations of associated sediments in a wider regional context. This article presents a discussion on obtained apparent radiocarbon dates of organic material from ten sections of the SE Altai. In addition to radiocarbon analysis, in each case multidisciplinary study was carried out in order to properly interpret obtained dates, as well as to explain the inability of directly using apparent 14C ages as a geochronological basis for paleogeographical reconstruction. The analysis presented is of vital importance for establishing the chronology of formation of large ice-dammed lakes and their cataclysmic draining; revealing chronology and paleoenvironmental conditions of pedogenesis in the highlands of the SE Altai; and estimating the range and magnitude of the tectonically driven topography rebuilding in the post-Neogene time.

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Development of the Vychegda-Vyatka-Kama drainage basin and changes in the outflow directions related to the Late-Glacial morphological conditions (North-Eastern European Russia)

Nazarov N. N., Kopytov S. V., Chernov A. V.

Geography and Tourism

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2018

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Vol. 6, No. 1

15--19

EN

The paper describes the features of the drainage system development in the upper Kama basin. Two buried river valleys were identified within the Kama-Pechora-Vychegda watershed. The upper courses of the Kama, the Vychegda, the Pechora and their tributaries likely belonged either to the White Sea basin, or the Caspian Basin. The southern direction of the outflow corresponded to the location of the palaeovalleys of the Pra-Kolva and the Pra-Vishera. The northern direction corresponded to the location of ancient hollows in the present valleys of the tributaries of the Kama. It is believed that the upper Kama was connected with the Vychegda basin. The geological structure of the palaeovalley has recorded a long period of joint development of the hydrosystems of the Kama and the Vyatka. The basins were divided only in the Late Neo-Pleistocene. The rivers regenerated in the Middle and Late Neo-Pleistocene after the lakes had flowed into the Kolva-Vishera basin in the east and into the Pra-Vyatka basin in the west.

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Sedimentary evidence for an ice-sheet dammed lake in a mountain valley of the Eastern Sudetes, Czechia

Hanáček M., Nývlt D., Skácelová Z., Nehyba S., Procházková B., Engel Z.

Acta Geologica Polonica

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2018

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Vol. 68, no. 1

107--134

EN

An accumulation of glacial sediments is located near Písečná village in the depression between the Sokol Ridge and Zlaté Hory Highlands NNE of Jeseník town (Eastern Sudetes). The accumulation lies at the lateral side of the mountain valley of the Bělá River and fills a preglacial palaeovalley of this river. Research combining facies analysis of outcrops, ground penetrating radar survey, interpretation drilling survey, and modelling of the preglacial relief was undertaken at the site. According to the results obtained, the upper part of the sedimentary accumulation represents a coarse-grained terminoglacial glaciofluvial delta of the Gilbert type. The development of the accumulation has dominantly been driven by the preglacial morphology. Facies typical for foresets of coarse-grained deltas represented mainly by high-density flows, cohesionless debris flows, debris falls and less common low-density flows were found in the outcrops. The delta near Písečná prograded into a lake dammed by the ice-sheet front in the north. The lake was bounded by the slopes of Sokol Ridge, Zlaté Hory Highlands and Góry Parkowe on other sides. The lake level reached an altitude of up to 430 m a.s.l., as the coarse-grained delta plain base lies at this level.

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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.