Biostratigraphy of Late Holocene bottom sediments from the Northern part of Chukchi Sea
- Authors: Vologina E.G.1, Kulagina N.V.1, Chernyaeva G.P.1, Sturm M.2, Kolesnik A.N.3
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Affiliations:
- Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Science
- Swiss Federal Institute of Aquatic Science and Technology
- Il’ichev Pacific Oceanological Institute, Far East Branch, Russian Academy of Sciences
- Issue: No 2 (2024)
- Pages: 48-57
- Section: Articles
- URL: https://ogarev-online.ru/2658-3518/article/view/282263
- DOI: https://doi.org/10.31951/2658-3518-2024-A-2-48
- ID: 282263
Cite item
Abstract
The research goal is the investigation of environmental processes of recent sedimentation in the Arctic Ocean area. A short core (length – 37 cm) was taken from the Northern part of the Chukchi Sea. Analytical methods included macroscopic sedimentological description by smear-slides, dating by γ-measurements of 137Cs and 210Pb, diatom and palynological analyses. Sedimentation rates at the research site have been determined to be 1 mm y-1. Thus, the age of the cored sediments spans approximately 400 years, which includes the period of the Little Ice Age. Abundant cold-water diatom species and spores of terrestrial plants within the lower part of the sediment core are characteristic for cold climate conditions, which dominated the Little Ice Age. The occurrence of Jurassic, Cretaceous, and Neogene species of spores and pollen in the Holocene deposits are the evidence of coastal abrasion and the subsequent transfer of the material to the coring site by currents. Southern, subtropical, and tropical species of diatoms within the upper, more recent part of the core reveal the transfer of material by currents from the Pacific Ocean to the Arctic Ocean through the Bering Strait. The results of biostratigraphic analyses indicate environmental changes during the last 400 years, revealed in bottom sediments of the Northern part of the Chukchi Sea.
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1. Introduction
Recent climate warming (Brohan et al., 2006; Wilson et al., 2007) leads to changes in the natural environment, both on continents and in oceans. The research has been conducted in the Chukchi Sea, a marginal sea of the Arctic Ocean, located between Chukotka and Alaska. Here, the increase of the mean annual air temperature over the past decades has caused a distinct areal reduction of ice cover (Stone, 1997; Crane, 2005). Such climatic and environmental changes are reflected in the formation and composition of the bottom sediments of the Chukchi Sea (Astakhov et al., 2018; Vologina et al., 2018; Astakhov et al., 2019; Vologina et al., 2019).
Compared to other marginal seas of the Arctic Ocean, the Chukchi Sea is characterized by its higher biological productivity, caused by the inflow of warmer Pacific waters through the Bering Strait [Ogorodnikov and Rusanov, 1978; Grebmeier et al., 2006; Astakhov et al., 2015]. Consequently, biostratigraphic methods are particularly important for studying bottom sediment of this area and are widely used (Saidova, 1994; de Vernal et al., 2005; Obrezkova et al., 2023).
This paper presents biostratigraphic results of palynological and diatom analyses of upper layers of bottom sediments sampled in the Northern region of the Chukchi Sea and leads to a better understanding of environmental processes of recent sedimentation in this region of the Arctic Ocean.
2. Material and Methods
Sediments were taken during an international expedition with the research vessel «Professor Khromov» in 2012. Core b16 with a length of 37 cm was recovered from a «boxcorer» at a site in the northern part of the Chukchi Sea with coordinates 72°32’37.8” / N 175°59’42” W, at a water depth of 100 m (Fig. 1). After splitting the core in half a macroscopic description of the split core was carried out, followed by the analysis of smear-slides with a light microscope SK14 (magnification x 100). Smear-slide description included the qualitative determination of the particle size and the occurrence of lithological and biological components. The sediments of the core were dated by γ-measurements of the activities of 137Cs and 210Pb, described by (Vologina et al., 2018; Vologina et al., 2019). Diatom and palynological analyses were carried out at sampling intervals of 1 cm to 2 cm. Diatom analysis was performed according to (Zhuze et al., 1969; Diatoms of the USSR, 1974) and preliminary results were published by Vologina et al. (2018). Technical processing of samples for palynological analysis was carried out according to a well-known method (Berglund and Ralska-Jasiewiczowa, 1986).
Fig.1. Map of Chukchi Sea with the positions of core b16. The arrows mark main ocean currents within Chukchi Sea according to (Stein et al., 2017): SCC – Siberian Coastal Current, HC – Herald Canyon Current, CC – Central Channel Current, BC – Barrow Canyon Current, ACC – Alaska Coastal Current.
3. Results
The sediments of core b16 are represented by clayey silt with an insignificant admixture of sand (Fig.2). The relatively homogeneous lithological composition indicates stable depositional conditions during their formation. Dating results reveal a sedimentation rate of approximately 1 mm y-1, implying a time range of 400 years for core b16. It includes the period of the Little Ice Age (LIA) from 1600 AD–1850 AD to the present (Vologina et al., 2018). Thus, the studied deposits belong to the Late Holocene.
3.1. Palynological analysis results
The total amount of pollen and spores in the sediments of core b16 ranges from 221 to 637 specimens (Fig. 2). Based on their composition, two different sections can be distinguished in the core.
Fig.2. Core b16: photo, lithology and diagram of pollen and spores. Legend of lithology: 1 – clay, 2 – silt, 3 – sand, 4 – diatoms. Note for the diagram: N – Neogene, J-K – Jurrassic-Cretaceous
Section 1: 17–37 cm. Picea obovata and Sphagnum sp. are dominant in this interval, which is characterized by a high content of spores (46–54 %), especially represented by Sphagnum sp. (30–38 %). Tree pollen (19–28 %), containing mainly Picea obovata (13–21 %), Pinus sec. Cembra (2–4 %) and Pinus sylvestris (2–4 %). Shrubs (12–21 %) are less frequent in the spectrum and mainly represented by Betula type Nanae (6–13 %) and Duschekia sp. (4–10 %). Grass pollen (7–15 %) are less frequent and contain mainly by Ericales (1–7 %), Artemisia sp. (up to 3 %), Cyperaceae (up to 2 %) and various herbs (2–5 %).
Section 2: 0–17 cm. This section is dominated by Picea obovata, Betula type Nanae, Duschekia sp. and Sphagnum sp. The content of spores (43–51 %) decreases and is represented by Sphagnum sp. (29–37 %), Polypodiaceae (4–9 %), Lycopodiaceae (2–5 %). The amount of tree pollen changes slightly (12–28 %), characterized by Picea obovata (8–20 %), Pinus sec. Cembra (1–4 %), Pinus sylvestris (1–4 %), Betula type Albae (up to 2 %). Section 2 contains more shrub pollen (16–29 %), namely Betula type Nanae (8–14 %), Duschekia sp. and Salix sp. (6–16 %). Grass pollen account for 9–12 %, including Ericales (1–5 %), Cyperaceae (up to 4 %), Artemisia sp. (up to 4 %), Poaceae (up to 2 %) and various herbs (2–4 %).
Up to 1.8 % of redeposited forms of the Neogene age (N) occur throughout the core (Tsuga sp., Juglandaceae, Carya sp., Myrica sp., Alnus sp., Quercus sp., Betula sp. Corylus sp., Ulmus sp., Tilia sp., Osmunda sp.) and up to 1 % of forms of the Jurassic (J) and Cretaceous (K) periods (Cyathidites-type, Pinus protocembra, Gleicheniidites sp., Ginkgo sp., Cicatricosisporites sp.) (Fig. 2).
3.2. Results of diatom analysis
The distribution of the most typical diatoms in the sediments of core b16 is presented in Table. 54 taxa of diatoms have been identified. The composition is dominated by planktonic species (61.1 %). The content of neritic species is 30 %, oceanic species – 26 % and sub-littoral species – 18.5 %.
Table. Content of the most frequent species of diatoms in the core b16 (in % of the total number)
| Section | Depth, cm | Achnanthes brevipes | Bacterosira fragilis | Coscinodiscus marginatus | Chaetoceros sp. | Ch. mitra | Chaetoceros (spores) | Nitzschia sp. | Rhizosolenia sp. | Thalassiosira antarctica | Th. hyalina | Th. nordenskioeldii | Thalassionema nitzsehioides |
2 | 0–1 | 3.7 | 2.6 | 1.1 | 12.4 | 5.7 | 59.9 | 4.0 | 0.15 | 0.5 | 0.3 | 4.0 | 0.9 |
3–4 | 1.3 | 1.0 | 4.1 | 3.4 | 1.1 | 41.7 | 4.3 | 1.5 | 3.2 | 0.9 | 1.7 | 3.0 | |
5–6 | 1.8 | 3.5 | 2.2 | 2.4 | 3.9 | 47.5 | 5.1 | 0.6 | 2.7 | 1.1 | 3.1 | 3.1 | |
7–8 | 1.5 | 2.3 | 1.7 | 5.4 | 6.2 | 49.4 | 3.2 | 0.8 | 1.9 | 0.9 | 0.6 | 2.6 | |
9–10 | 3.2 | 1.8 | 0.9 | 12.4 | 5.8 | 35.1 | 4.5 | 0.5 | 3.6 | 0.9 | 0.8 | 2.2 | |
11–12 | 1.1 | 1.9 | 2.1 | 15.5 | 4.1 | 41.9 | 3.2 | 8.0 | 3.4 | – | 1.9 | 3.4 | |
13–14 | 0.7 | 3.3 | 1.6 | 14.9 | 3.3 | 44.2 | 3.6 | 0.5 | 3.1 | – | 2.5 | 1.1 | |
15–16 | 1.4 | 2.3 | 0.9 | 9.2 | 5.5 | 49.3 | 4.3 | 0.9 | 1.3 | – | 2.3 | 1.1 | |
1 | 17–18 | 1.2 | 2.7 | 8.3 | 16.6 | 4.2 | 32.3 | 3.7 | 2.3 | 2.1 | 1.1 | 0.2 | 2.7 |
19–20 | 0.7 | 2.1 | 1.5 | 19.3 | 6.1 | 42.1 | 5.3 | 2.1 | 0.8 | 0.2 | 1.2 | 2.8 | |
21–22 | 1.3 | 4.2 | 1.1 | 22.5 | 5.3 | 32.1 | 3.3 | 1.7 | 2.0 | 0.4 | 1.6 | 3.6 | |
23–24 | 1.0 | 2.1 | 0.7 | 28.4 | 4.0 | 35.6 | 4.5 | 1.6 | 2.0 | 0.9 | 1.8 | 1.4 | |
25–26 | 1.5 | 2.0 | 1.3 | 25.1 | 5.2 | 29.4 | 3.3 | 3.1 | 4.1 | 2.5 | – | 1.3 | |
27–28 | 1.3 | 2.1 | 1.0 | 28.0 | 4.0 | 27.3 | 4.1 | 3.4 | 3.0 | 1.3 | 0.3 | 2.7 | |
29–30 | 0.9 | 1.3 | 0.5 | 14.9 | 4.3 | 40.3 | 2.9 | 1.6 | 4.5 | 0.9 | 0.2 | 0.2 | |
31–32 | 0.6 | 1.1 | 0.5 | 14.7 | 2.6 | 45.1 | 4.1 | 2.7 | 2.6 | 0.1 | 1.0 | 1.5 | |
33–34 | 0.3 | 1.6 | 0.6 | 9.8 | 4.6 | 45.4 | 4.0 | 2.4 | 3.0 | 1.0 | 0.6 | 2.2 | |
35–36 | 0.8 | 1.6 | 2.3 | 10.5 | 8.4 | 29.0 | 3.9 | 2.6 | 3.9 | 1.5 | 0.3 | 1.6 | |
36–37 | 0.8 | 1.2 | 1.1 | 12.5 | 2.8 | 50.1 | 3.7 | 1.8 | 1.2 | 1.5 | 0.8 | 1.2 |
Arctoboreal and subboreal diatoms amount 62.8 % of the total diatom content. Nevertheless, a distinct occurrence can be observed of southern boreal, subtropical and tropical species, as well as redeposited ancient diatoms.
Approximately half of all diatom valves belong to the genus Chaetoceros Ehr. (up to 50 %) and the species Chaetoceros sp.(up to 28 %). Coscinodiscus marginatus Ehr. represents 0.5–8.3 %, Ch. mitra (Bailey) Cleve – 1.1–6.2 %. The increased content of diatom species is observed in the lower part of the core (Section 1, Table), where arctoboreal, cold-loving species of the genus Thalassiosira dominate: Th. antarctica, Th. hyalina, as well as Bacterosira fragilis, Coscinodiscus marginatus, Actinocyclus sp., Paralia sulcata (Ehr.) Cl., Rhizosolenia hebetata (Bail.) Gran. and numerous representatives of the genus Chaetoceros.
4. Discussion
The Holocene sediments of the Chukchi Sea consist mainly of material formed by bottom erosion and coastal abrasion (Yashin, 2000). Material from river runoff accounts for not more than 7 %. In the sediments from the northern part of the Chukchi Sea the terrigenous fractions predominate over the biogenic components.
The palynological spectra of sediments from core b16 generally reflect forest-tundra and tundra vegetation, which is widespread along the coasts of the Chukchi Sea including a distinct predominance of pollen of shrubs, herbs and spores. In the lower part of the core, corresponding to the period of LIA, an increase in the content of spores is associated to colder climatic conditions. Re-deposited species of the Jurassic, Cretaceous, and Neogene are observed throughout the entire sediment core (Fig. 2). They derived from coastal abrasion and subsequent transfer by currents. The results are distorted by the significant content of coniferous pollen (especially spruce). Their most likely source is assumed to be by currents from the Bering Sea.
Most of the diatom species observed in the sediments of core b16 (almost 2/3 of the total composition) are characteristic of cold-water conditions at high latitudes. The presence of south boreal, subtropical, and tropical valves is most likely caused by their entry through the Bering Strait (Astakhov et al., 2015; Vologina et al., 2018), facilitated mainly by currents (Grebmeier et al., 2006). The identification of changes in composition and quantity of pollen, spores and diatoms in the sediments allows a distinction of two stages of sedimentation. Obviously, lower temperatures during cooler environmental conditions throughout LIA prevailed during the time of sedimentation within the lower half of the core. This caused lower biological productivity and lead to the increase of the cold-water species of genus Thalassiosira (Table) (Vologina et al., 2018).
The obtained data correlate well with variations in the chemical composition of bottom sediments sampled in the northern part of the Chukchi Sea (Astakhov et al., 2019). The results of palynological and diatom analyzes complement the geochemical data for core b16 and are consistent with the reconstruction of ice conditions in the Arctic over the past 300–400 years (Astakhov et al., 2019).
5. Conclusion
Detailed biostratigraphic analyses of a sediment core from the northern part of the Chukchi Sea allow the reconstruction of environmental conditions during the last 400 years in this part of the Arctic Ocean. The lower section of the core was formed during the cooling period of the Little Ice Age. It is characterized by the deposition of the cold-water diatoms and the increased content of spores of terrestrial plants. The upper core-section represents the time after the end of LIA, when warmer climate conditions prevailed and led to a distinct reduction of the cold-water diatoms and spores of terrestrial plants. The appearance of southern boreal, subtropical and tropical diatom species in the sediments of the northern part of the Chukchi Sea is caused by the transfer of Pacific waters through the Bering Strait to the Arctic Ocean. Transport of coniferous pollen and spores to the sediments of the Chukchi Sea occurs mainly by ocean currents and by wind drift from land areas. Coastal abrasion and the subsequent transfer by currents are responsible for Jurassic, Cretaceous and Neogene species of spores and pollen redeposited in the Holocene deposits.
6. Acknowledgments
The authors express gratitude to many colleagues from POI FEB RAS, EAWAG, and IEC SB RAS for the support during the collection of bottom sediments, analytical work, and discussion of the results.
7. Funding
The study was supported by the Russian Science Foundation grant No. 24-27-00098, https://rscf.ru/en/project/24-27-00098/. The equipment of the Central Collective Use Center «Geodynamics and Geochronology» of the IEC SB RAS was partially involved in the work.
Conflict of interest
The authors declare no competing interest.
About the authors
E. G. Vologina
Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Science
Author for correspondence.
Email: vologina@crust.irk.ru
Russian Federation, 128 Lermontov street Irkutsk, 664033
N. V. Kulagina
Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Science
Email: vologina@crust.irk.ru
Russian Federation, 128 Lermontov street Irkutsk, 664033
G. P. Chernyaeva
Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Science
Email: vologina@crust.irk.ru
Russian Federation, 128 Lermontov street Irkutsk, 664033
M. Sturm
Swiss Federal Institute of Aquatic Science and Technology
Email: vologina@crust.irk.ru
Switzerland, 133 Überlandstrasse, Dübendorf, 8600
A. N. Kolesnik
Il’ichev Pacific Oceanological Institute, Far East Branch, Russian Academy of Sciences
Email: vologina@crust.irk.ru
Russian Federation, 43 Baltiyskaya street, Vladivostok 690041
References
- Astakhov A.S., Bosin A.A., Kolesnik A.N. et al. 2015. Sediment geochemistry and diatom distribution in the Chukchi Sea: Application for bioproductivity and paleoceanography. Oceanography 28(3): 190–201.
- Astakhov A.S., Vologina E.G., Dar’in A.V. et al. 2018. Influence of global climate changes in past centuries on the chemical composition of bottom sediments in the Chukchi Sea. Russian Meteorology and Hydrology 43 (4): 251–257. doi: 10.3103/S1068373918040064
- Astakhov A.S., Bosin A.A., Liu Yanguang et al. 2019. Reconstruction of ice conditions in the northern Chukchi Sea during recent centuries: geochemical proxy compared with observed data. Quaternary International 522: 23–37. doi: 10.1016/j.quaint.2019.05.009
- Berglund B.E., Ralska-Jasiewiczowa M. 1986. Handbook of Holocene Palaeoecology and Palaeohydrology. Ed. by Berglund. Interscience, New York.
- Brohan P., Kennedy J.J., Harris I. et al. 2006. Uncertainty estimates in regional and global observed temperature changes: A new dataset from 1850. Journal of Geophysical Research 111: D12106.
- Crane K. 2005. Russian-American long-term census of the Arctic. Initial expedition to the Bering and Chukchi Seas. Arctic Research of the United States 19: 73–76.
- De Vernal A., Hillaire-Marcel C., Darby D.A. 2005. Variability of sea ice cover in the Chukchi Sea (western Arctic Ocean) during the Holocene. Paleoceanography 20: PA4018. doi: 10.1029/2005PA001157
- Diatoms of the USSR. 1974. In: Proshkina-Lavrenko A.I. (Ed.). Leningrad: Nauka. (in Russian).
- Grebmeier J.M., Cooper L.W., Feder H.M. et al. 2006. Ecosystem dynamics of the Pacific influenced Northern Bering and Chukchi Seas in the Amerasian Arctic. Progress in Oceanography 71: 331–361.
- Obrezkova M.S., Pospelova V., Kolesnik A.N. 2023. Diatom and dinoflagellate cyst distribution in surface sediments of the Chukchi Sea in relation to the upper water masses. Marine Micropaleontology 178: 102184. doi: 10.1016/j.marmicro.2022.102184
- Ogorodnikov V.I., Rusanov V.P. 1978. Conditions for accumulation and distribution of amorphous silica in bottom sediments of the Chukchi Sea. Oceanology 18(6): 1049–1052.
- Saidova H.M. 1994. Ecology of shelf foraminiferal communities and Holocene paleoenvironments of the Bering and Chukchi Seas. Moscow: Nauka.
- Stein R., Fahl K., Schade I. et al. 2017. Holocene variability in sea ice cover, primary production, and Pacific-Water inflow and climate change in the Chukchi and East Siberian Seas (Arctic Ocean). Journal of Quaternary Science 32(3): 362–370.
- Stone R.S. 1997. Variations in western Arctic temperatures in response to cloud radiative and synoptic-scale influences. Journal of Geophysical Research: Atmospheres 102(D18): 21769–21776.
- Vologina E.G., Kalugin I.A., Daryin A.V. et al. 2018. Late Holocene sedimentation in active geological structures of the Chukchi Sea. Geodynamics & Tectonophysics 9(1): 199–219. doi: 10.5800/GT-2018-9-1-0345
- Vologina E.G., Sturm M., Astakhov A.S., Shi Xuefa. 2019. Anthropogenic traces in bottom sediments of Chukchi Sea. Quaternary International 524: 86–92. doi: 10.1016/j.quaint.2019.07.008
- Wilson R., D’Arrigo R., Buckley B. et al. 2007. A matter of divergence: Tracking recent warming at hemispheric scales using tree ring data. Journal of Geophysical Research 112: D17103.
- Yashin D.S. 2000. Holocene sedimentogenesis of the Arctic seas of Russia. In: Geological and Geophysical Characteristics of the Lithosphere in the Arctic Region. Vol 3. Saint Petersburg: VNII Okeangeologiya, pp. 57–67 (in Russian).
- Zhuze A.P., Mukhina V.V., Kozlova O.G. 1969. Diatoms and silicoflagellates in the surface layer of sediments of Pacific Ocean. In: Microflora and microfauna in the modern sediments of the Pacific Ocean. Moscow: Nauka, pp. 7–47 (in Russian).
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