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Paleoclimatic analysis of Quaternary sediments associated with the floodplain deposits of a tropical estuary along the southwestern cost of India

Murali Divya, Reghunath Rajesh, Prakash Pranav, Bhushan Ravi, Krishnan K. Anoop, Baby Sruthy Rose

Studia Quaternaria

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2024

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Vol. 41, Nr 1

13--21

EN

The coastal regions of southwest India which falls in the tropical regime, have witnessed many transgression-regression events and climatic extremes in the Quaternary Period. A core, 15 m long, was recovered from the floodplains associated with a typical backwater body (lake) in the southwestern coast of India. The granulometric analysis proved dominance of sand and silt fractions and extremely high energy conditions over the entire core. The TOC/TN ratio indicated a domination of the C4-type over the C3-type plants in the lower half of the core, suggesting a warm climate. The C3-type plants prevail in the upper part of the core, thus reflecting cool and wet environments. Extremely low values of TOC/TN ratio (0.33% to 10%) of the core indicate short periods of very high rainfall events and the rapid influx of nutrients to the basin and the eutrophication of the basin. The presence of slightly brackish, brackish/marine and marine benthic foraminifers at 12.5–9 m depth indicates episodes of transgression and regression. The derived AMS radiocarbon dates suggest the Marine Isotope Stage 3 for the lower part of the core.

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Analiza sumarycznych rozkładów gęstości prawdopodobieństwa (PDFs) dat radiowęglowych i luminescencyjnych z nieciągłych profili osadów rzecznych na tle zmian klimatycznych zapisanych w rdzeniu NGRIP

Michczyńska Danuta J., Dzieduszyńska Danuta A., Gębica Piotr, Krzyszkowski Dariusz, Ludwikowska-Kędzia Małgorzata, Petera-Zganiacz Joanna, Wachecka-Kotkowska Lucyna, Wieczorek Dariusz

Przegląd Geologiczny

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2023

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Vol. 71, nr 10

527--529

EN

The study presents the results of a compre¬hensive analysis of radiocarbon and luminescence dates from samples taken from a fluvial environment for selected regions south of the LGM line, presented against a high-resolution INTIMATE stratigraphy. It is shown that discontinuous records of fluvial environmen¬tal responses in such an analysis reveal significantly more details than studies conducted at individual sites. A strong correlation is observed between peaks in the PDF curves of radiocarbon dates and interstadial periods, while accumulations of luminescence dates are corre¬lated with stadial periods.

3

Cyclic sedimentation pattern in Lake Veetka, southeast Estonia: a case study

Saarse L.

Geologos

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2015

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Vol. 21, No. 1

59--69

EN

A sediment core from Lake Veetka, southeast Estonia, 1077 cm in length and covering 10,500 calibrated years, was examined using loss-on-ignition, grain-size distribution and AMS 14C dating to reconstruct depositional dynamics. The studied core, recovered from the northern part of the lake, shows a cyclic pattern of organic and mineral matter concentration with cycle durations of 100-400 years. Cyclicity is displayed better in sediments laid down between 9,200 and 5,600 cal BP. Within two time windows (5,600–5,100 cal BP and from 1,200 cal BP to the present), sediment composition changed drastically on account of a high and fluctuating mineral matter content, obviously driven by different factors. Little Ice Age cooling is characterised by the highest proportion of mineral matter, and the Medieval Warm Period is typified by high organic matter content. The cyclic change of organic and mineral matter has been related to climate dynamics, most likely an alternation of wet and dry conditions, changes in the water level of the lake and differences in bioproduction.

4

Middle Weichselian Pleniglacial sedimentation in the Krasówka river palaeovalley, central Poland

Wachecka-Kotkowska L., Krzyszkowski D., Klaczak K., Król E.

Annales Societatis Geologorum Poloniae

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2014

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Vol. 84, No. 4

323--340

EN

This study from the Szczerców field of the Bełchatów open-cast mining complex, central Poland, reveals the local geomorphic and stratigraphic history of the Krasówka river palaeovalley – a major western tributary of the river Widawka. The data are from the western flank of the N-trending palaeovalley and the study combines detailed lithofacies analysis of outcrop sections, sediment petrology, AMS measurements and palynological evidence. Radiocarbon dates are of crucial importance for the reconstruction of the palaeovalley history. The study contributes to a better understanding of the response of the Central European river systems to the Vistulian Pleniglacial conditions. The Vistulian Pleniglacial sedimentation in the study area commenced with the accumulation of the latest Eemian to earliest Weichselian (≥45 ka) deposits by sheetwash processes in a local karstic topographic depression. The Krasówka river then formed to the east and shifted farther eastwards, but later approached twice the study area with a net aggradation prior to 43 ka BP – flooding it with overbank deposits. The river subsequently incised by nearly 20 m around 40 ka BP and began to fill in its valley by aggradation around 35 ka BP, while migrating eastwards and markedly decreasing its flooding capacity from 33 to 24 ka BP. The fluvial system was rejuvenated around 21 ka BP, with some initial erosion, and kept filling its valley by aggradation while flooding the valley flank. The river after filling its valley continued to aggrade, but gradually ran out of vertical accommodation and migrated westwards. The fluvial activity at this stage was increasingly accompanied by aeolian sedimentation. Once the Mid-Weichselian Pleniglacial came to an end around 14.5 ka BP, the Krasówka river had re-incised by nearly 5 m and assumed its present-day altitude in response to the post-glacial regional isostatic rebound of crustal basement.

5

Some problems in the study of the chronology of the ancient nomadic cultures in Eurasia (9th - 3rd centuries BC)

Alekseev A. Yu., Bokovenko N. A., Boltrik Yu., Chugunov K. A., Cook G., Dergachev V. A., Kovaliukh N., Possnert G., Plicht J. van der, Scott E. M., Sementsov A., Skripkin V., Vasiliev S., Zaitseva G.

Geochronometria

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2002

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Vol. 21

143-150

EN

This research is focused on the chronological investigations of ancient nomads belonging to the Scythian cultures which occupied the steppe and forest-steppe zones of Eurasia during the 9 th -3 rd centuries BC. The 14 C dates for the pre-scythian and early scythian time in both Europe and Asia are presented and compared to their chronological position based on archaeological evidence. The first 14 C dates have been produced for the Scythian time monuments located in the Lower Volga River basin, Urals and Transurals regions. Their chronological positions are compared with the position of the monuments of Southern Siberia and Central Asia. It was shown that the nomadic cultures belonging to the Scythian culture began to exist over the wide territory of Eurasia from the 9 th -8 th centuries cal BC and there are some monuments which may be synchronous to the Arzhan royal barrow (the oldest monument known). A list of new 14 C dates and a map of the monuments are presented.

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The radiocarbon age of marine and land deposits in the southern Baltic area

Uścinowicz Szymon, Kramarska Regina, Tomczak Anna, Zachowicz Joanna

Geologos

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2000

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Vol. 5

155--163

EN

Basing on statistical analysis of ca. 150 radiocarbon dates of sediments from different environments an attempt to reconstruct the time framework of main environmental changes during the late Pleistocene and Holocene in the Southern Baltic area was made. The main results are as follow: 45 000-22 000 years BP - period of interpleniglacial (Grudziądz Interstadial), 22 000-14 500 years BP - period of the last glaciation (lack of dates for this period or uncorrected dates), 14 500-8800 years BP - beginning of the last deglaciation and development of the southern Baltic area in land conditions, 8800-5000 years BP - period of Mezoholocene (Littorina, Atlantic) transgression of the Southern Baltic with major changes of coastline, since ca. 5000 years BP - present shape of the southern Baltic with minor changes of coastline.