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

R.K. Nepop
R.K. Nepop
, 
A.R. Agatova
A.R. Agatova
, 
M.A. Bronnikova
M.A. Bronnikova
, 
E.P. Zazovskaya
E.P. Zazovskaya
, 
I.YU. Ovchinnikov
I.YU. Ovchinnikov
 and 
P. Moska
P. Moska
   | Dec 31, 2020
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Article Category: CONFERENCE PROCEEDINGS OF THE 13TH INTERNATIONAL CONFERENCE “METHODS OF ABSOLUTE CHRONOLOGY” JUNE 5-7TH, 2019, TARNOWSKIE GORY, POLAND
Published Online: Dec 31, 2020
Page range: 138 - 153
Received: Nov 10, 2019
Accepted: Aug 28, 2020
DOI: https://doi.org/10.2478/geochr-2020-0018
Keywords
© 2020 R. K. Nepop. published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Fig 1

Location of the SE Altai within the Altai Mountains. The acronyms indicate the names of the largest intermountain depressions: Ch – Chuya, K – Kurai; Dz – Dzhazator valley. Red circles show the location of studied sections.
Location of the SE Altai within the Altai Mountains. The acronyms indicate the names of the largest intermountain depressions: Ch – Chuya, K – Kurai; Dz – Dzhazator valley. Red circles show the location of studied sections.

Fig 2

Multiplot view of analyzed radiocarbon ages. Dating results are marked as follows: red – for the samples collected in ancient (Upper Oligocene– Low Miocene peat and brown coal-bearing) deposits; yellow – for the samples collected from the single pack of sediments; and green – for dating results of humic acids obtained from one sample.
Multiplot view of analyzed radiocarbon ages. Dating results are marked as follows: red – for the samples collected in ancient (Upper Oligocene– Low Miocene peat and brown coal-bearing) deposits; yellow – for the samples collected from the single pack of sediments; and green – for dating results of humic acids obtained from one sample.

Fig 3

Geomorphological position of Section 1 (a), west–east stretch of sediments (b) along the roadcut in a strandline at altitude of ~1570 m a.s.l. and numerous fragments of organic matter (c) presented in diluvial deposits as inclusions. Field car is 2 m high and 4 m long.
Geomorphological position of Section 1 (a), west–east stretch of sediments (b) along the roadcut in a strandline at altitude of ~1570 m a.s.l. and numerous fragments of organic matter (c) presented in diluvial deposits as inclusions. Field car is 2 m high and 4 m long.

Fig 4

Generalized scheme of sedimentary records in Section 1 and available numerical ages.
Generalized scheme of sedimentary records in Section 1 and available numerical ages.

Fig 5

The Upper Oligocene–Low Miocene peat and brown coal-bearing deposits exposed in Section 2. General view of the outcrop in a dry gully (a) and sample of ancient peats from the lower part of the section (b).
The Upper Oligocene–Low Miocene peat and brown coal-bearing deposits exposed in Section 2. General view of the outcrop in a dry gully (a) and sample of ancient peats from the lower part of the section (b).

Fig 6

General view of the outcrop (b), exposed sediments, and obtained numerical ages (b) for Section 3. Sample location and calculated ages are indicated by rectangle for OSL (ka) and by circle for 14C (cal BP) dates.
General view of the outcrop (b), exposed sediments, and obtained numerical ages (b) for Section 3. Sample location and calculated ages are indicated by rectangle for OSL (ka) and by circle for 14C (cal BP) dates.

Fig 7

Geomorphological position of Section 4 (a). View to southwest along the “Chuya-highway”. North Chuya range in the background. Exposed sediments and available radiocarbon dates for peaty-rich layers (b).
Geomorphological position of Section 4 (a). View to southwest along the “Chuya-highway”. North Chuya range in the background. Exposed sediments and available radiocarbon dates for peaty-rich layers (b).

Fig 8

Geomorphological position of Section 5. Sample location and obtained numerical ages are indicated by rectangle for OSL (ka) and by circle for 14C (cal BP) dates.
Geomorphological position of Section 5. Sample location and obtained numerical ages are indicated by rectangle for OSL (ka) and by circle for 14C (cal BP) dates.

Fig 9

Taldy–Dyurgun brown coal deposit.
Taldy–Dyurgun brown coal deposit.

Fig 10

Geomorphological position (a), exposed sediments, and obtained radiocarbon ages (b) for Section 6.
Geomorphological position (a), exposed sediments, and obtained radiocarbon ages (b) for Section 6.

Fig 11

Google image of studied sites in the Dzhazator River valley (a); exposed sediments and obtained radiocarbon ages for Section 8b (b, c).
Google image of studied sites in the Dzhazator River valley (a); exposed sediments and obtained radiocarbon ages for Section 8b (b, c).

Fig 12

Exposed sediments and obtained radiocarbon ages for Section 8c (a); redeposited organic mineral material and obtained radiocarbon ages for Section 8a (b).* indicates uncalibrated 14C age for sample IGAN 4880 (see Table 1)
Exposed sediments and obtained radiocarbon ages for Section 8c (a); redeposited organic mineral material and obtained radiocarbon ages for Section 8a (b).* indicates uncalibrated 14C age for sample IGAN 4880 (see Table 1)

Radiocarbon dating results. Dating material is marked as co – coal; ha – humic acids; pp – paleopeat; toc – total organic carbon. Dates marked with asterisk are results of dating of humic acids obtained from one sample.

Laboratory codeStudied sections (fig. 1)Applied techniqueDating material14C yr BPCal BP (2σ)Confidence intervals %Description
SOAN 94961LSCha3380±1153920-337095.4Fossil soil in subaerial pack above lacustrine deposits
SOAN 95021LSCpp22070±45027350-2560095.4Inclusions of peat in the upper diluvial pack
SOAN 78021LSCha34750±48040430-3837095.4Inclusions diluvial pack of organic matter in the middle part of upper
SOAN 49711LSCha20750±22025560-2441095.4Fragment diluvial pack of charcoal (Vysotsky in 2009the middle ) part of upper
SOAN 95031LSCpp26715±70032500-2936095.4Inclusions of peat at the bottom of the upper diluvial pack
SOAN 93061LSCha12400±19515220-13920 13890-1386094.8 0.6Organic fragments in the lower diluvial pack (after Vysotsky in Agatova et al., 2020)
SOAN 93051LSCha7320±1108370-795095.4Organic Vysotsky fragments in Agatova in et the allower ., 2020diluvial ) pack (after
IGAN 48112LSCpp35090±95041830-3770095.4Upper Formation Oligocene–Low Miocene peat of Koshagach
SOAN 95053LSCha33790±109540930-3582095.4Thin flowing peat paleolake layer in sediments of the Early Holocene
IGAN 32044LSCha18800±27023420-2211095.4Upper peat layer (after Rogozhin et al. 2008)
SOAN 95754LSCha29375±28534070-3291095.4Middle peat layer
SOAN 95764LSCha27970±32032760-3120095.4Lower peat layer
SOAN 96895LSCha---Silt loams at the same location as Beta 159972 sample (not enough material – 0.4g of ha from a 3-kg sample)
IGANAMS 78215AMStoc21410±6025900-2558095.4Silt loams at the same location as Beta 159972 sample
Beta 1599725AMSha35870±49041540-3947095.4Layer profile of (Herget, organic 2005 sediment, ) probably part of paleosol
IGAN 62496LSCha13990±27017710-1621095.4Horizon [В] of fossil soil at the bottom of proluvial–colluvial pack
IGAN 60086LSCco9830±23012100-1058095.4Lens of charcoals under fossil soil
SOAN 9573-16LSCco8635±150101809350--9400 933095.1 0.3Lens of charcoals under fossil soil
SOAN 9573-26LSCha9220±951066010610--10620 102201.9 93.5Matrix in lens of charcoals under fossil soil
IGAN 50117LSCco50120±2300--Upper shagach Oligocene–Formation Low from Miocene Taldy–Dyurgun brown coal deposit of Ko
IGAN 48808aLSCpp44790±1400--Upper layer of brown coal
IGAN 48818aLSCco37570±110044000-4006095.4Lower layer of brown coal
SOAN 94958bLSCpp14085±40018140-1602095.4Upper horizon (among three) interlayers within the peat
IGAN 49088bLSCpp36680±91042730-3955095.4Lower horizon (among three) interlayers within the peat
SOAN 87098cLSCha2760±803070-274095.4Upper partly exhumed at the surface organic mineral layer
SOAN 84208cLSCha23100±41528080-2644095.4
SOAN 84218cLSCha25530±35530620-2888095.4
SOAN 84228cLSCha16600±14020410-1964095.4
SOAN 87108cLSCha15330±11018820-1834095.4
SOAN 8711*8cLSCha17940±12022090-2137095.4Layers of organic mineral matter with inclusions of
organic material (mainly fragments of peat and some-
SOAN 9464*8cLSCha22475±45027570-2594095.4times lignitized wood) affected by solifluction
SOAN 9627*8cLSCha22880±28027670-2654095.4
SOAN 8712**8cLSCha15600±10019080-1863095.4
SOAN 9467**8cLSCha26400±50031300-2950095.4
SOAN 9629**8cLSCha19480±36024310-2260095.4

OSL dating results. The dose rate was determined based on the radioisotope content measurements. The equivalent doses were calculated using central age model (Galbraith et al., 1999). OSL age is given with 1σ standard deviation except samples GdTL 3125 and GdTL 3126 (2σ).

Laboratory codeSample location (fig. 1)U (Bq/kg)Th (Bq/kg)K (Bq/kg)Dose rate (Gy/ka)Equivalent dose (Gy)OSL Age (ka)Number of aliquotsWater contentSample description
GdTL 2590129.1±0.822.4±0.5434±142.21±0.0842.0±1.819.0±1.11318±5%Sandy layer at the top of cross-bedded diluvial pack (Fig. 3)
GdTL 2591125.3±0.620.0±0.4485±152.23±0.0835.9±3.516.0±1.72018±5%Sandy zons of layer loams between (Fig. 3) hori-
GdTL 3125316.6±0.421.4±0.6480±232.06±0.0919.6±1.59.41±1.681218±5%Lacustrine peaty layer sands (Fig. below 5) the
GdTL 3126317.3±0.421.9±0.7486±262.11±0.0923.6±1.511.12±1.741418±5%Lacustrine peaty layer sands (Fig. above 5) the
GdTL 3424517.2±0.824.0±1.2501±422.20±0.1881.2±2.737.0±3.12715±5%Sandy of sliding layer proluvium at the bottom (Fig. 7)
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