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Erosion and accumulation phases during the last glacial-interglacial cycle : a case study of the terrace system of the Odra and Osobłoga rivers (southern Poland)

Wójcicki Krzysztof Jan, Pawelec Halina, Malik Ireneusz, Woskowicz-Ślęzak Beata, Moska Piotr

Geological Quarterly

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2020

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Vol. 64, No. 1

104--119

EN

In the Odra and Osobłoga River valleys in the vicinity of the town of Krapkowice, a system of morphological levels is present which is exceptionally extensive compared to other such systems in southern Poland. The extent, origins and chronology of these levels have been the subject of many controversies. In the light of current research, the terraces, which are situated on average 14.5-13, 12-10, 8-6, 6-4 and 3-1 metres above the river level, were formed in the post-Wartanian interval. The main factor driving their development was erosion, which compensated for the effects of large-scale aggradation that had occurred during the anaglacial phase of the Odranian Glaciation (MIS 8) dated to 261 ±15 ka. The impact of climatic conditions on the trends towards fluvial erosion or accumulation was only of secondary importance. According to OSL dating, successive phases of vertical stabilisation of the valley floor occurred ~118.8 ±8.3, 87.7 ±5.7 and 42.0 ±2.0 ka. In the meantime, erosion intensified, which resulted in the formation of lower terrace levels. During the climatic minimum of the Upper Plenivistulian (21.5 ±1.5 ka), under conditions of the delivery of sheet-wash-generated sediment, the aggradation of distal reaches of the Odra River valley was locally marked. During the Late Vistulian and Holocene, erosive tendencies continued, which were reflected by the fact that the surfaces of subsequent inset alluvial fills were situated ever lower. In the light of dating results, it can be concluded that during the colder periods correlated with the Rederstall Stadial (MIS 5b) and with the Hasselo Stadial (MIS 3), a braided river was present in the river valleys examined, which was most probably accompanied by permafrost. During the Eemian Interglacial (MIS 5e), during the Late Vistulian Interstadials and in the Holocene, it was a meandering river.

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The Late Quaternary vegetational and environmental history of western tropical Africa - the eastern Benin Basin, Lagos, Nigeria

Adeonipekun P. A., Adeniyi T. A., Mateawo J., Agbalaya B.

Geology, Geophysics and Environment

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2017

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Vol. 43, no. 4

277--291

EN

A palynological study of a 30 m borehole within the Akoka campus of the University of Lagos, Akoka, Nigeria revealed Late Quaternary paleo-vegetational, climatic and environmental changes. Sixteen samples at a regular interval of 2 m were subjected to standard palynological and sedimentological techniques. Six pollen zones representing six paleoclimatic phases within the Late Quaternary period were recognized. The age model is based on two radiocarbon dates (6 m: 5,495 ± 25 ¹⁴C yr and 12 m: 15,660 ± 40 ¹⁴C yr) and, by extrapolation, the sequence spans approximately the last 35,000 yr BP. The African maximum transgression and the African Humid Period (wet paleoclimate maximum) – the Nouaktchottian, and Pre-Nouaktchottian respectively – were recognized, while the Ogolian II (Erg II) was stratigraphically recognized and the Upper Inchirian extrapolated. Recovered diatom frustules with other proxies were employed for paleoclimatic and paleoecological deductions. Four hydrological cycles and three paleoecological settings were identified. Results from this work indicate the co-eval record of paleoclimatic events across Africa, suspected cooling during the African maximum transgression in Nigeria and the usefulness of coastal freshwater swamp sediments for paleoclimate studies.

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Kohonen Artificial Neural Networks and the IndVal Index as Supplementary Tools for the Quantitative Analysis of Palaeoecological Data

Płóciennik M., Kruk A., Michczyńska D. J., Birks J. B.

Geochronometria

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2015

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Vol. 42, no.1

189--201

EN

We applied two widely-used methods for data partitioning — constrained incremental sum-of-squares (CONISS) and Optimal Partitioning (OP) along with two supplementary methods, a Kohonen artificial neural network (self-organising map, SOM) and the indicator value (IndVal) index, for the quantitative analysis of subfossil chironomid assemblages from a palaeolake in Central Poland. The samples, taken from 79 core depths, were divided into 5–11 groups (five by SOM, seven by CONISS, 11 by OP), for which different numbers of indicator taxa were determined with the use of the IndVal index (18 for CONISS, 15 for SOM, 11 for OP). Only six indicator taxa were common to all three methods. The number of highly specific (p < 0.001) taxa was highest for SOM. Only the SOM analysis clearly reflected the rate of the changes in chironomid assemblages, which occurred rapidly in the Late Glacial (as a result of greater climate variability) and slowly in the Holocene (as a reflection of slow long-term changes in the local habitat, such as paludification). In summary, we recommend using SOM and the IndVal index in combination with CONISS and/or OP in order to detect different aspects of temporal variability in complex multivariate palaeoecological data.

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Diatom record of northeast Atlantic circulation changes in marine isotope stages 1 and 5

Witak M., Kuijpers A.

Oceanological Studies

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2001

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Vol. 30, No. 1-2

21--36

EN

Fossil and subfossil diatom floras were analysed in a sediment core taken near the outlet of the Faroe Bank Channel, NE Atlantic. Diatom preservation horizons were found at various levels in the core. The correlation with the oxygen isotope stratigraphy of the core indicates that these horizons correspond to the Marine Oxygen Isotope Sub-Stages 5e (Eemian), 5a and Stage 1 (Holocene). Results of the study show that environmental conditions for the development of diatoms were more favourable in Stage 5 than in the Holocene. At the very beginning of the Sub-Stages 5e and 5a distinct changes in the diatom concentration are indicative of circulation changes probably associated with a marked intensification of the North Atlantic Current. The highest surface water temperature is indicated by the diatom flora from early Sub-Stage 5e.

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Late Quaternary evolution of the Czyżynka river valley, Wałbrzych Upland, Middle Sudetes Mts, southwestern Poland

Krzyszkowski D.

Geologia Sudetica

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1998

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Vol. 31, nr 2

259-288

EN

The lower part of the Czyżynka river valley (Wałbrzych Upland, Sudetes) was formed entirely after the early Saalian (Odranian) stage. The subsequent, 60-80 m deep, valley was incised into the mountain plateau. The valley is generally narrow with an alternating wide and narrow segments, and characterized by steep slopes, including common subvertical rock walls. Three terraces, formed most probably during the Wartanian/Eemian, Middle Weichselian and Late Weichselian represent the main stages of fluvial activity. Fluvial sequences show that sinuous to meandering rivers were active throughout the late Quaternary. Two phases of loess deposition are inferred (Wartanian and Middle Weichselian), as the deposits of the older terraces contain large admixtures of loess-like deposits. Moreover, two phases of large angular debris production and formation of extensive slope covers and fans have been recognized. The older occurred during the Upper Pleniglacial of the Weichselian stage. A continuum of slope colluvium was formed at that time, from fine-grained sheet wash deposits (including redeposited loess) to coarse grained deposits formed by cohesive debris flows, noncohesive debris flows and grain flows, and open-work loose material formed by debris avalanches. Frost activity and permanently moist conditions have been reported for that time, most probably with permafrost. Also, all these slope deposits contain an admixture of loess, suggesting loess deposition that time, too. The second phase of coarse debris production occurred, most probably, during the the Younger Dryas forming less extensive slope covers.