scholarly journals Seasonal deposition processes and chronology of a varved Holocene lake sediment record from Chatyr Kol lake (Kyrgyz Republic)

Geochronology ◽  
2020 ◽  
Vol 2 (1) ◽  
pp. 133-154
Author(s):  
Julia Kalanke ◽  
Jens Mingram ◽  
Stefan Lauterbach ◽  
Ryskul Usubaliev ◽  
Rik Tjallingii ◽  
...  
Keyword(s):  
Kyrgyz Republic ◽  
Sediment Record ◽  
Spring Precipitation ◽  
Radiocarbon Dates ◽  
Thin Sections ◽  
Varve Thickness ◽  
210Pb And 137Cs ◽  
Plant Remains ◽  
Bulk Organic Matter ◽  
Deposition Processes

Abstract. Microfacies analysis of a sediment record from Chatyr Kol lake (Kyrgyz Republic) reveals the presence of seasonal laminae (varves) from the sediment base dated at 11 619±603 BP (years Before Present) up to ∼360±40 BP. The Chatvd19 floating varve chronology relies on replicate varve counts on overlapping petrographic thin sections with an uncertainty of ±5 %. The uppermost non-varved interval was chronologically constrained by 210Pb and 137Cs gamma spectrometry and interpolation based on varve thickness measurements of adjacent varved intervals with an assumed maximum uncertainty of 10 %. Six varve types were distinguished, are described in detail, and show a changing predominance of clastic-organic, clastic-calcitic or clastic-aragonitic, calcitic-clastic, organic-clastic, and clastic-diatom varves throughout the Holocene. Variations in varve thickness and the number and composition of seasonal sublayers are attributed to (1) changes in the amount of summer or winter/spring precipitation affecting local runoff and erosion and/or to (2) evaporative conditions during summer. Radiocarbon dating of bulk organic matter, daphnia remains, aquatic plant remains, and Ruppia maritima seeds reveals reservoir ages with a clear decreasing trend up core from ∼6150 years in the early Holocene, to ∼3000 years in the mid-Holocene, to ∼1000 years and less in the late Holocene and modern times. In contrast, two radiocarbon dates from terrestrial plant remains are in good agreement with the varve-based chronology.

scholarly journals Seasonal deposition processes and chronology of a varved Holocene lake sediment record from Lake Chatyr Kol (Kyrgyz Republic)

2020 ◽  
Author(s):  
Julia Kalanke ◽  
Jens Mingram ◽  
Stefan Lauterbach ◽  
Ryskul Usubaliev ◽  
Achim Brauer
Keyword(s):  
Lake Sediment ◽  
Kyrgyz Republic ◽  
Sediment Record ◽  
Spring Precipitation ◽  
Radiocarbon Dates ◽  
Thin Sections ◽  
Varve Thickness ◽  
210Pb And 137Cs ◽  
Plant Remains ◽  
Deposition Processes

Abstract. A finely laminated lake sediment record with a basal age of 11,619 ± 603 years BP was retrieved from Lake Chatyr Kol (Kyrgyz Republic). Microfacies analysis reveals the presence of seasonal laminae (varves) from the sediment basis to ~ 360 ± 40 years BP. The Chatvd19 floating varve chronology covers the time span from 360 ± 40 years BP to the base and relies on replicate varve counts on overlapping petrographic thin sections with an uncertainty of ± 5 %. The uppermost non-varved interval was chronologically constrained by 210Pb and 137Cs γ-spectrometry and interpolation based on varve thickness measurements of adjacent varved intervals with an assumed uncertainty of 10 %. Six varve types were distinguished, are described in detail and show a changing predominance of clastic-organic, clastic-calcitic or -aragonitic, calcitic-clastic, organic-clastic and clastic-diatom varves throughout the Holocene. Variations in varve thickness and the number and composition of seasonal sublayers are attributed to 1) changes in the amount of summer or winter/spring precipitation affecting local runoff and erosion and/or to 2) evaporative conditions during summer. Radiocarbon dating of bulk organic matter, daphnia remains, aquatic plant remains and Ruppia maritima seeds reveal reservoir ages with a clear decreasing trend up core from ~ 6,150 years in the early Holocene, to ~ 3,000 years in the mid-Holocene, to ~ 1,000 years and less in the late Holocene and modern times. In contrast, two radiocarbon dates from terrestrial plant remains are in good agreement with the varve-based chronology.

First Holocene floating varve chronology in Central Asia from the Lake Chatyr Kol sediment record (Kyrgyz Republic)

2020 ◽  
Author(s):  
Julia Kalanke ◽  
Jens Mingram ◽  
Stefan Lauterbach ◽  
Ryskul Usubaliev ◽  
Achim Brauer
Keyword(s):  
Central Asia ◽  
Mountain Lake ◽  
Lake Basin ◽  
High Mountain ◽  
Kyrgyz Republic ◽  
Sediment Record ◽  
Thin Sections ◽  
The Holocene ◽  
Sediment Profile ◽  
Varve Chronology

<p>We present the first floating varve chronology in arid Central Asia of a finely laminated lake sediment record from the high-mountain Lake Chatyr Kol (Kyrgyz Republic). The record was retrieved from the deepest part (~20m) of the lake basin and comprises seasonal laminations (varves) from 11,619 ± 603 years BP to 360 ± 40 BP years. The identification of varves is based on seasonal deposition models established from continuous thin section analyses of the entire sediment profile. The varves comprise a complex pattern of six different micro-facies types throughout the Holocene. All varve types include a pronounced clastic-detrital sublayer, but the composition of their summer sublayers varies between organic, diatom, calcite, and aragonite sublayers. Based on replicate varve counts on overlapping petrographic thin sections an uncertainty of ± 5 % has been calculated for the varve chronology. The chronology is floating because in the uppermost part of the sediment profile varves have been only occasionally formed or preserved which prevented from continuous varve counting in this interval. Instead, the non-varved interval has been dated with <sup>210</sup>Pb and <sup>137</sup>Cs γ-spectrometry providing an age for anchoring the floating chronology to the absolute time scale. The resulting chronology is supported by two <sup>14</sup>C ages obtained from terrestrial plant macrofossils. In contrast, radiocarbon dating of aquatic materials showed significantly older ages and prove reservoir effects. Through comparison with the varve chronology changes in reservoir effects throughout the Holocene have been determined. We find a stepwise decline of reservoir ages from up to ~6150 years in the early Holocene to lowest reservoir ages of less than 1000 years in the late Holocene. In addition to their value as chronological tool, changes in varve thickness and seasonal sublayer composition are used as proxies for hydro-climatological reconstruction of Holocene climate evolution.</p><p>This is a contribution to the CAHOL project, part of the BMBF-funded and integrated project CAME II.</p>

The First Holocene Varve Chronology for the UK: based on the integration of varve counting, radiocarbon dating and tephrostratigraphy from Diss Mere (UK).

2021 ◽  
Author(s):  
Celia Martin-Puertas ◽  
Amy A. Walsh ◽  
Simon P.E Blockley ◽  
Poppy Harding ◽  
George E. Biddulph ◽  
...  
Keyword(s):  
Laminated Sediments ◽  
Seasonal Patterns ◽  
Sediment Record ◽  
Radiocarbon Dates ◽  
Varve Chronology ◽  
Counting Error ◽  
Tephra Layers ◽  
Core Depth ◽  
The Uk ◽  
Varve Counting

<p>This paper reports the first Holocene varved chronology for the lacustrine sediment record of Diss Mere in the UK. The record of Diss Mere is 15 m long, and shows 4.2 m of finely-laminated sediments, which are present between ca. 9 and 13 m of core depth. The microfacies analysis identified three major seasonal patterns of deposition, which corroborate the annual nature of sedimentation throughout the whole interval. The sediments are diatomaceous organic and carbonate varves with an average thickness of 0.45 mm. A total of 8473 varves were counted with maximum counting error of up to  40 varves by the bottom of the varved sequence. To tie the resulting floating varve chronology to the IntCal 2020 radiocarbon timescale, we used a Bayesian Deposition model (P_Sequencewith outlier detection) on all available chronological data from the core. The data included five radiocarbon dates, two known tephra layers (Glen Garry and OMH-185) with calendar ages based on Bayesian modelling of sequences of radiocarbon ages, and the relative varve counts between dated points. The resulting age-depth model (DISSV-2020) dates the varved sequence between ca. 2100 and 10,300 cal BP and age uncertainties are decadal in scale (95% confidence). </p>

Plant Remains from the Washington Square Mound site (41NA49), Nacogdoches, Texas

2016 ◽  
Author(s):  
Leslie L. Bush
Keyword(s):  
Vegetation Type ◽  
Atlantic Coast ◽  
Evergreen Forest ◽  
Pinus Echinata ◽  
Shortleaf Pine ◽  
Radiocarbon Dates ◽  
Plant Remains ◽  
River Cane ◽  
Botanical Remains ◽  
Washington Square

Botanical remains were identified from 27 lots from the Washington Square Mound site (41NA49). The primary occupation at the site is Middle Caddo period in age. The first pooled set of calibrated radiocarbon dates from the site fell into the period A.D. 1268-1302, while a recent set of five calibrated dates from samples of plant remains discussed in this article range from A.D. 1279 + 17; (2) A.D. 1358 + 57; and three dates on charred corn from Features 36, 81, and 86 range from as early as A.D. 1394 to as late as A.D. 1437. These dates as a group fall in the Middle Caddo period; there is limited evidence at the site for other, smaller occupations, including Late Caddo and Late Woodland/Early Caddo. At least three mounds were visible in the nineteenth century. Much of the site was never plowed, a situation that has resulted in intact shallow deposits and unusually large pottery sherds, although a high school has been built over parts of the non-mound site area. Labels of botanical lots that included excavation dates indicate a range from 1979 to 1983, associating the botanical remains with Stephen F. Austin State University Field School excavations that took place during this time. At least nine features are represented in the botanical lots. Four are described as charcoal-filled pits, one as a pit, and one as a post mold. Feature 36 was a corn cob concentration . Botanical lots for Features 62, 81, and 199 are also present. The Washington Square Mound site is situated in the city of Nacogdoches, Texas, on an interfluve between Banita Creek and La Nana Creek, which drain into La Nana Bayou and the Angelina River. The area lies squarely in the Pineywoods ecological zone, the westernmost extension of the great Southeastern Evergreen Forest that reaches across the southeastern United States to the Atlantic coast (Braun 2001:281). The dominant vegetation type in an upland area such as Washington Square during presettlement times would have been a shortleaf pine community, where shortleaf pines (Pinus echinata) share dominance with dry-site oaks such as southern red oak (Quercus falcata), post oak (Q. stellata), and blackjack oak (Q. marilandica), hickories (Carya spp.), and elms (Ulmus spp.) Springs and marshy areas nearby would have offered aquatic and wetland plants such as river cane (Arundinaria gigantea). A spring-fed pond is reported to have existed north of the site, and a marshy area to the southwest. Pollen studies indicate that use of the modern and recent vegetation is appropriate for understanding the plants and attendant animal resources available to occupants of the sites during prehistoric times. Some fluctuations in rainfall and temperature have taken place, however. In addition, more frequent fires would have made the understory in the uplands less prominent than today. Early explorers in East Texas and other parts of the Eastern Woodlands noted the open, park-like nature of many woodlands.

scholarly journals Atmospheric Radiocarbon at the End of the Last Glacial: An Estimate Based on AMS Radiocarbon Dates on Terrestrial Macrofossils From Lake Sediments

Radiocarbon ◽  
1989 ◽  
Vol 31 (03) ◽  
pp. 795-804 ◽  
Author(s):  
Hugo Zbinden ◽  
Michael Andree ◽  
Hans Oeschger ◽  
Brigitta Ammann ◽  
Andre Lotter ◽  
...  
Keyword(s):  
Mass Spectroscopy ◽  
Calibration Curve ◽  
Hard Water ◽  
Sedimentation Rates ◽  
Local Effects ◽  
Data Set ◽  
Radiocarbon Dates ◽  
Pollen Zone ◽  
Plant Remains ◽  
The Last Glacial

The main purpose of this work is to reconstruct the atmospheric Δ 14C in the glacial-postglacial transition, 14,000 – 10,000 BP, a range not covered by the tree-ring calibration curve. We measured 14C/12C ratios on series of terrestrial macrofossils from sediments of two Swiss lakes. We selected exclusively plant remains of recognizable terrestrial origin that are not affected by hard water and thus reflect atmospheric 14C concentration. Due to the scarcity of such material, we used accelerator mass spectroscopy. Cores of two lakes were measured to eliminate local effects and to check the reproducibility of results. This required a reliable, 14C-independent correlation of the cores, obtained through local pollen zone boundaries 14C ages were obtained as a function of the depth in the cores. If sedimentation rates are known ages can be converted into Δ 14C values. We also attempted estimating sedimentation rates; calculations are based on the Swedish varve chronology. Results were combined to form an entire data set. The Δ 14C curve shows an increase with time during the Allerød and decreases during Preboreal and Bølling periods. Probabilities for these 14C variations are discussed.

Tree macrofossils of Younger Dryas age from Cohoes, New York State, USA

2012 ◽  
Vol 49 (5) ◽  
pp. 671-680 ◽  
Author(s):  
Norton G. Miller ◽  
Carol B. Griggs
Keyword(s):  
New York ◽  
Picea Glauca ◽  
New York State ◽  
Abies Balsamea ◽  
Younger Dryas ◽  
Hudson River ◽  
Growth Responses ◽  
Radiocarbon Dates ◽  
Plant Remains ◽  
American Beaver

Tree macrofossils dating from the middle to end (about 1000 years, ca. 12 600–11 600 cal years BP) of the Younger Dryas chronozone were found in an organic deposit on the southwest side of the Mohawk River, near its junction with the Hudson River in Cohoes, New York, USA. The fossils included substantial wood fragments, associated plant remains, and pollen, which indicate a forest of white spruce ( Picea glauca ), balsam fir ( Abies balsamea ), and tamarack ( Larix laricina ). The presence of white, rather than black ( P. mariana ) or red ( P. rubens ) spruce in the Younger Dryas was probably due to a riparian-type environment, confirmed by its location and American beaver tooth marks on some of the wood fragments. The clusters of wood radiocarbon dates indicate periodic changes in erosion and deposition at the site. One possible but very short decline (temperature reversal?) may be indicated by tree-ring growth, but in general, the ring widths of the trees and their growth responses suggest variable but slowly improving conditions over time, possibly from warming temperatures, before the end of the Younger Dryas.

Tephra anchored floating varve chronology covering ca. 19.0-11.0 ka BP in new core from Lake Lago Grande di Monticchio: preliminary results

2020 ◽  
Author(s):  
Xueru Zhao ◽  
Sabine Wulf ◽  
Markus J. Schwab ◽  
Rik Tjallingii ◽  
Achim Brauer
Keyword(s):  
High Resolution ◽  
Environmental Changes ◽  
Late Quaternary ◽  
Methodological Approach ◽  
Radiocarbon Dates ◽  
Thin Sections ◽  
Last Glacial ◽  
Varve Chronology ◽  
Varve Counting ◽  
The Last Glacial

<p>The high-resolution Monticchio (MON) sediment record has been demonstrated to be a key archive for reconstructing climate and environmental changes in the central Mediterranean for the last glacial-interglacial cycle. New sediment cores have been retrieved in April 2016 to investigate particularly the transition from the Last Glacial Maximum into the Holocene with a new high-resolution methodological approach. A floating varve chronology spanning ca. 8,000 years has been established by varve counting on thin sections using a petrographic microscope and layer thickness based sedimentation rate estimates for non- or poorly varved intervals. Varve counting is based on detailed seasonal deposition models of five different varve types. The resulting floating chronology consist of 66.6% individually counted varves and 33.4% interpolated years. The uncertainty estimate of the floating chronology has been determined by double counting and amounts to ±5.8%.</p><p>The floating chronology is anchored to an absolute chronology using the Agnano Pomici Principali tephra, dated at 11,999±52 cal yrs BP from paleosols overlying proximal tephra (Bronk Ramsey et al. 2015), is a suitable anchoring point to cross correlation. The resulting varve-based chronology has been compared with several other marker tephras dated elsewhere including the Soccavo 4 tephra (11,700±150 cal yrs BP), the Neapolitan Yellow Tuff (NYT; 14,194±172 cal yrs BP) and the Greenish tephra (19226±104 cal yrs BP). Further comparison with published (Hajdas et al. 1997) and new radiocarbon dates from different terrestrial macro remains are discussed in this paper. This study presents an independent chronology for the last glacial/interglacial transition for a comparison of MON data with high-resolution lake records western and central Europe.</p><p>References</p><p>Bronk Ramsey, C., P. G. Albert, S. P. E. Blockley, M. Hardiman, R. A. Housley, C. S. Lane, S. Lee, I. P. Matthews, V. C. Smith & J. J. Lowe (2015) Improved age estimates for key Late Quaternary European tephra horizons in the RESET lattice. Quaternary Science Reviews, 118<strong>,</strong> 18-32.</p><p>Hajdas, I., G. Bonani, B. Zolitschka, A. Brauer & J. Negendank (1997) 14C Ages of Terrestrial Macrofossils from Lago Grande Di Monticchio (Italy). Radiocarbon, 40<strong>,</strong> 803-807.</p>

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