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Radiometric dating of the Ootun palaeosol and its implication for the age of the Shifting Sand in Ngorongoro Lengai Geopark (Arusha, Tanzania)

Makongoro Mohamed Zengo, Vegi Maheswara Rao, Vuai Said Ali Hamad, Msabi Michael Mwita

Geologos

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2022

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Vol. 28, No. 3

203--215

EN

The Shifting Sand is a barchan dune in Ngorongoro Lengai Geopark in Arusha, Tanzania. The geopark, a UNESCO World Heritage Site, is protected by the Ngorongoro Conservation Area Authority. The dune ranks amongst the main geosites that have been attracting numerous tourists; it formed as a result of volcanic ash eruptions that led to tephra deposition on a palaeosol (palaeosurface) in the Ootun area. The easterly winds modified the ash into dunes and headed to the Olduvai Gorge area. The age of the Shifting Sand dune is not known in detail. In the present study, we employ the radiocarbon (14C) dating method to date a subsurface palaeosol bed in the Ootun area where the tephra (i.e., original Shifting Sand materials) was originally deposited. An Accelerator Mass Spectrometer was used to determine the carbon-14 date of the palaeosol so as to estimate the age of the Shifting Sand dune, and an Energy Dispersive X-ray Fluorescent Spectrometer to determine the chemical composition of the Shifting Sand material and the tephra bed for correlative purposes. A radiocarbon (14C) date of 2510 ± 30 years BP for the Ootun palaeosol was obtained to estimate the minimum age of the Ootun subsurface tephra deposited in the area; since then, this started to move westwards towards the Olduvai Gorge area, where it is today defined as the Shifting Sand. The current findings add educational value to the Shifting Sand in Ngorongoro Lengai Geopark and improve our understanding of the eruption history of the Gregory Rift volcanoes.

2

New datings of deposits from Odra river valley - stratigraphic consequences and interpretation at fluvial succession

Gontaszewska-Piekarz Agnieszka, Szczepaniak Małgorzata

Civil and Environmental Engineering Reports

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2019

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Vol. 29, no. 3

183--199

EN

This paper presents organic sediments age analysis in Odra river valley in Słubice, western Poland. In this middle reach of Odra valley reach the uppermost fluvial deposits contain several alternate layers of organic sediments. These deposits have been mostly interpreted as the Holocene fluvial (floodplain) sediments, even if visible admixture of organic matter is not observed. However, there is also another hypothesis. Geotechnical studies conducted in several locations in Słubice, have questioned this interpretation. The main argument was the values of preconsolidation ratio in the range of 0.8 to 5.4, which may suggest, that the analysed sediments were covered by an ice sheet. Also, based on the presence of a clay layer devoid of organic matter impurities in the top of organic deposits, the second one presumes an interglacial (possibly Eemian) age of the discussed fluvial/organic sediments (peats and silts). To verify these hypotheses, six samples from six different boreholes drilled in the Odra river valley, in the centre of Słubice were collected. The results of 14C dating and its interpretation allowed to determine the age of the tested material. All analysed samples from Słubice (Odra river valley) were formed within the last 10,000 years - in Preboreal, Atlantic and Subboreal. Such a result contradicts the earlier stratigraphic interpretations.

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

Nowoczesna dendrochronologia i jej pionierzy

Wandelt P

Przegląd Papierniczy

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2013

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R. 69, nr 1

51--58

PL

Dendrochronologia jest naukową metodą datowania wydarzeń, zjawisk przyrodniczych i obiektów zabytkowych zawierających drewno, a także badania klimatu w przeszłości, czym zajmuje się dendroklimatologia, na podstawie porównywania i liczenia pierścieni przyrostów rocznych w drzewie, przy czym nie trzeba go ścinać i przeżynać, bo podstawowym narzędziem dendrochronologa jest specjalny świderek pozwalający z żywego, rosnącego nawet drzewa pobrać próbkę wszystkich słojów w przekroju drewna, wyciągając ją tym świdrem (rys. 1), jak korek z butelki wina. Metoda ta wcale nie musi być inwazyjna i szkodzić drzewu, gdyż podobnie robiliśmy w fińskim lesie z kolegą wykonującym w Fińskim Instytucie Celulozowo-Papierniczym pracę licencjacką, wprowadzając w nawiercone otworki aerosol paraquatu, w celu zwiększenia wydzielania przez drzewo związków żywicznych.

EN

The article describes how astronomer A. Douglass was searching some evidence of periodic sunspot cycles in tree rings and how his former student E. Schulman discovered the oldest bristlecone pine trees which allowed to recalibrate a radiocarbon dating method, rewriting history and origin of our European civilisation.

5

Malakofauna i fazy rozwoju osuwiska w Tylce kolo Krościenka (Pieniny)

Alexandrowicz W. P.

Geologia / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

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2009

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T. 35, z. 2/1

69-75

EN

The landslide is ranking on western slope of the White Stream valley. Two colluvial barrier and accompanied them dammed-lakes have been formed. Deposits filling these lakes contains rich molluscan communities. Additionally the occurrence of plant remains allowed to dating deposits using radiocarbon method. These data make possible to reconstruction of the history of this landslide during Late Holocene.

6

Too old ams radiocarbon dates obtained from moss remains from Lake Kwiecko bottom sediments (N Poland)

Madeja J., Latowski D.

Geochronometria

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2008

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Vol. 32

13-19

EN

The paper presents the results of the AMS radiocarbon dating of moss macrofossils which seem to be too old in the context of palynological data. The lack of agreement between the obtained results of radiocarbon dating and pollen analysis has been discussed. Some possible causes of the discrepancies between the results of radiocarbon dating and palynological dating have been given.

7

Zróżnicowanie pokryw deluwialnych i aluwialnych w Sudetach Wschodnich w świetle analiz sedymentologicznych i datowań radiowęglowych

Latocha A.

Przegląd Geologiczny

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2007

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Vol. 55, nr 1

38-38, 45

EN

Textural and structural diversity of slope covers and alluvial deposits in the upper parts of mid-mountain valleys in the Eastern Sudetes allows for assessing human impact on their formation. Sandy-silty colluvial deposits in the lower parts of slopes or within local flats and slope depressions originate due to enhanced surface wash from arable grounds, in contrast to underlying coarser material with solifluctional features. Similarly, fine-grained overbank alluvial deposits can be also connected with human activity, as the slope material, washed down from arable fields, was transported to the channels and deposited within the floodplains during high-water stages. Their linkages with human activity have been confirmed by radiocarbon dating of charcoal found at the bottom of these sediments. The dates show a strong correlation with the dates of foundation of villages in the study area. The development of agriculture and deforestation of slopes resulted in increasing surface wash and transportation of slope material to footslopes and river channels. The extent of deposits, which can be correlated with human activity, is much more widespread than it was suggested before and they are found as high as 800 m a.s.l. Their thickness, however, is visibly smaller in comparison to colluvial or alluvial sediments deposited in the Sudetes foreland and it is strongly influenced by the local morphology. According to the 14C dating, these sediments are also much younger than those in the foreland, which corresponds to a substantial delay in human settlement expansion into the mountain areas.

8

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.

9

Radiocarbon in freshwater carbonates as tool of Late Quaternary studies

Pazdur Anna

Geologos

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2000

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Vol. 5

135--154

EN

Different methods of radiometric dating (14C, U/Th, TL) and stable isotopes composition (13C and 18O) in freshwater carbonates are used for analysis of sedimentologic process and reconstruction of paleoclimatic conditions as well as for stratigraphic purposes. Calcareous tufa and speleothems deposited in karst areas seem to be rightly significant indicators of the past changes because of their direct relation to the environment of deposition. Some important methodical and interpretation problems for Quaternary research in Poland were solved during the last ca. 20 years in Gliwice Radiocarbon Laboratory. Synthetic approach to 14C dating of calcareous tufa from Southern Poland, based on statistical analysis of correlation between lithologic type of tufaceous sediment, carbon isotope composition and apparent age was done. Results of measurements of 8lsO and 8I3C in tufa samples dated with 14C method are used to reconstruct Holocene climatic changes in southern and Eastern Poland. The stable isotope composition was used to estimate the mean annual temperatures in the interval 9500-2000 yr BP. On the basis of statistical analysis of several hundred 14C dates for speleothems from Kraków-Wieluń Upland caves warm and cold climate periods were indicated during the last 50,000 years BP. Distribution of the dates indicate that growth of speleothems between 30 and 20 ka BP may be interpreted as reflecting changes of paleoclimatic conditions. Comparison of measured 14C activities in carbonate fractions of lake marl from Gościąż Lake with their varve ages allowed for accurate determination of secular changes of 14C dilution factor of total dissolved inorganic carbon. Basing on the geochemical model developed by Broecker and Walton it was possible to reconstruct mean lake level during the Late Glacial and Holocene. Basing on 14C dates of lithological boundaries in the cores from Gościąż lake basin the changes of lake level during the last 12 ka BP were reconstructed. Paleokarst forms known as “pipes” from Southwest England and South Wales were dated by 14C, U/Th and TL methods. 14C ages were obtained from carbonate cements within sandrock and on the pipe walls. Statistical analysis of dates and geochemical considerations indicate on periods of pipes pipes and pipes infillings.

10

Chronology of loess-paleosol sequences at Weinan section, Central China

Jiaqi Liu, Sun Jimin, Chen Rui, Wang Wenyuan

Geologos

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2000

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Vol. 5

165--174

EN

The loess profile at Weinan (34°12’N and 109°31’E), Central China, with good stratigraphic stability and well developed paleosols, was systematically sampled and dated by AMS radiocarbon and TL methods. The preliminary high-resolution time scale of this section has been tuned. Based on this time scale and other climatic proxies such as susceptibility curve and grain-size curve, the author summarizes several for the last 150,000 years age results regarding some important stratigraphic boundaries and established a time scale. According to this time scale, the basal age of S0, located at 143 cm below the top of section, corresponding to the boundary between S0/L1 is 11,980 yr cal BP, this is the age of the beginning of Holocene. The age of the boundary between L1 and S1 is dated 74,220 years B. P. at 854 cm, which shows the ending age of the last interglacial stage is about 74,000 cal BP. Si is highly pedogenised paleosol with dark brown color and 361 cm in thickness. It can be divided into three sub-layers, corresponding to the last interglacial stage, the real S1/L2 boundary is located in 1,180 cm depth and has an age of 128,870 years B. P. It may be correlated with the deep-sea oxygen-isotopic stage 5. The Last Glacial Maximum (LGM) reflected in Weinan loess section by grain size curve and susceptibility curve is from about 20,000 cal BP to 18,000 cal BP. A rapid deposit period from 300 cm to 196 cm lasted a time span from 20,200 cal BP to 19,800 cal BP. The deposit rate of this segment is over 20 times than the average deposit rate of Chinese loess.