Gygytgyn Lake Research Articles

Vegetation response to climate changes in the eastern Arctic during the Middle Gelasian age of the Early Pleistocene

Palynological analysis of sediments from El'gygytgyn Lake document vegetation changes in the Eastern Arctic from early marine isotope stage (MIS) 74 to late MIS 80 (c.2.1–1.9 MA) and close the last remaining gap in the El'gygytgyn pollen record. Cooler climates were characterized by a mix of Larix forest-tundra, shrub Betula tundra, and herb-dominated communities. During interglaciations, Larix forests with tree Betula and Alnus, and perhaps with a minor component of Picea and tree Pinus, characterized areas that today are tundra. These forests included a rich shrub understory of Betula, Duschekia, Salix, and Pinus pumila. Although MIS 77 has been considered a “super” interglaciation, the data do not indicate that this stage was exceptionally warm. Interstadial conditions are denoted by pollen assemblages that indicate the regional vegetation was dominated by Larix forest -tundra and an absence of Pinus pumila. The palynological results from this Early Pleistocene interval demonstrate the need to: 1) modify the El'gygytgyn age model; 2) reevaluate the relationship of sediment facies to climate change; and 3) reconsider the occurrence and/or definition of “super” interglaciations.

Vegetation Response to Climate Change during the Middle Calabrian in Arctic Chukotka

A palynological record obtained from El'gygytgyn Lake sediments, which spans the 1.244-1.304 million years (Ma) interval of the Calabrian Stage, shows repeated changes in the plant communities of Arctic Chukotka. These variations in the vegetation further suggest a dominance of interstadial and interglacial climates. Eight pollen zones were distinguished within this interval. According to the working age model for the composite El'gygytgyn core, these pollen zones correspond to marine oxygen isotope stages (MIS) 40, 39, and 38. The upper boundary of MIS 38 coincides with magnetic event the Cobb Mountain (1.240 Ma), which is one of the main chronological landmarks used in creating the core's chronology. The features of modern pollen-spore spectra obtained from the water-sediment interface within the lake aided in reconstructing both the local and regional paleovegetation. The consistent presence of Larix pollen throughout the 1.244-1.304 Ma interval indicates that even under the severest climatic conditions Larix forest-tundra persisted on the Anadyr Plateau and near El'gygytgyn Lake. This pattern differs sharply from that seen in the Middle and Late Pleistocene when herb-dominated tundra characterized the glacial intervals in the Arctic. The spore-pollen spectra further show that the warmest climatic conditions occurred during MIS 39. The data from the 1.244-1.304 Ma interval represent the last step in completing the Quaternary vegetation history from this unique site in Arctic Siberia.

Environmental changes in the eastern Arctic 1.6975-1.965 Ma, palynological investigations from El’gygytgyn Lake, northeastern Russia

The 1.6975–1.965 Ma (MIS 60–MIS 74) portion of the El'gygytgyn Lake record includes two key chronostratigraphic markers in the Calabrian–Gelasian boundary (1.806 Ma) and the Olduvai paleomagnetic excursion (1.77–1.95 Ma). It also provides the first paleovegetation information for these times from the eastern Arctic. Palynological data indicate the dominance of Larix forest and forest-tundra during warm and cool intervals, which differs sharply from the herb tundra which characterized glacial intervals of the Middle and Late Pleistocene. These forests likely included tree species of Betula and Alnus and perhaps Populus and Chosenia. The persistence of Larix indicates summer temperatures were warmer than present. Pinus pumila, a typical interglacial taxon, is restricted to MIS 65 and MIS 71, suggesting other intervals experienced dry winters. Cool and warm periods are clearly marked by vegetation changes during the Late Gelasian Stage, but a dominance of Poaceae pollen and reduction in Alnus pollen during the Early Calabrian Stage mutes the climatic fluctuations. The loss of Alnus perhaps relates to decreases in seasonal temperatures.

Remnants of paleoflora in impact melt rocks of the El'gygytgyn crater (Chukotka, Russia)

AbstractRemnants of paleoflora were discovered in impact melt rocks from the El'gygytgyn crater, Chukotka, Russia. El'gygytgyn is a 3.58 Ma, 18 km diameter impact structure in Chukotka, northeastern Russia. A circular crater basin is surrounded by an uplifted rim. The crater floor is occupied by the El'gygytgyn Lake, 12 km in diameter, surrounded by lacustrine terraces up to 80 m in height. Impactites found at the El'gygytgyn crater include impact melt rocks, glass bombs, and shock metamorphosed volcanic rocks. Most impact melt rocks occur only in redeposited state in the terrace lake deposits. Floral remnants were discovered in impact melt rocks from various locations in the terrace deposits. The floral remnants include fragments of leaves, cell tissue, and undetermined organic matter that occur in vesicles within glassy melt rocks and impact melt breccias. After the discovery of floral remnants in impact melt breccias from upper Miocene strata in Argentina, and the description of floral imprints in the Dakhleh Glass of proposed impact origin in Egypt, the detection of paleoflora remnants in impact melt rocks of the El'gygytgyn structure is the first such occurrence in a confirmed impact crater on Earth.

The Late Pleistocene climatic optimum in the eastern Arctic region: Evidence from El’gygytgyn Lake

The palynological investigations of sediments of the crater of El’gygytgyn Lake (67°30′ N, 172°05′ E), which provided a continuous record of interglacial and glacial events in Polar Chukotka, revealed significant climate warming corresponding to Marine Isotope Stage 31 (MIS 31) lasting from 1.062 to 1.081Ma ago. Its upper limit is placed within the Jaramillo paleomagnetic episode (0.99–1.07 Ma) registered in the sedimentary section of the lake. During MIS 31, the vegetation community was dominated by Betula-Alnus forests with subordinate Larix trees. These forests included also coniferous (Picea, Pinus) and broad-leaved trees and shrubs (Quercus, Carpinus, Corylus). The interglacial of MIS 31 was characterized by the warmest climate for the entire Quaternary Period. The warming episode established in the continuous record of the section of El’gygytgyn Lake implies relations between climatic events in the Arctic and Antarctic regions.

Late Pleistocene and Holocene Vegetation History as Inferred From Palynological Investigations of the El’gygytgyn Lake Crater Permafrost Deposits

The results of the investigation of three permafrost cores from 3.6 Myr old Lake Elgygytgyn impact crater are presented here. Paleobotanical reconstructions are based on palinological studies and involve mostly late glacial time and Holocene. Our results are more detailed in comparison to the data based on lake sediments studies due to very low sedimentation rate in Lake Elgygytgyn. The age models rely on radiocarbon dates and also on correlations between our results with previously published data.

Testing the ureilite projectile hypothesis for the El'gygytgyn impact: Determination of siderophile element abundances and Os isotope ratios in ICDP drill core samples and melt rocks

AbstractThe geochemical nature of the impactites from International Continental Scientific Drilling Project—El'gygytgyn lake drill core 1C is compared with that of impact melt rock fragments collected near the western rim of the structure and literature data. Concentrations of major and trace elements, with special focus on siderophile metals Cr, Co, Ni, and the platinum group elements, and isotope ratios of osmium (Os), were determined to test the hypothesis of an ureilite impactor at El'gygytgyn. Least squares mixing calculations suggest that the upper volcanic succession of rhyolites, dacites, and andesites were the main contributors to the polymict impact breccias. Additions of 2–13.5 vol% of basaltic inclusions recovered from drill core intervals between 391.6 and 423.0 mblf can almost entirely account for the compositional differences observed for the bottom of a reworked fallout deposit at 318.9 mblf, a polymict impact breccia at 471.4 mblf, and three impact melt rock fragments. However, the measured Os isotope ratios and slightly elevated PGE content (up to 0.262 ng g−1 Ir) of certain impactite samples, for which the CI‐normalized logarithmic PGE signature displays a relatively flat (i.e., chondritic) pattern, can only be explained by the incorporation of a small meteoritic contribution. This component is also required to explain the exceptionally high siderophile element contents and corresponding Ni/Cr, Ni/Co, and Cr/Co ratios of impact glass spherules and spherule fragments that were recovered from the reworked fallout deposits and from terrace outcrops of the Enmyvaam River approximately 10 km southeast of the crater center. Mixing calculations support the presence of approximately 0.05 wt% and 0.50–18 wt% of ordinary chondrite (possibly type‐LL) in several impactites and in the glassy spherules, respectively. The heterogeneous distribution of the meteoritic component provides clues for emplacement mechanisms of the various impactite units.

First data on the expansion of Larix gmelinii (Rupr.) Rupr. into arctic regions of Beringia during the early Holocene

The international program on paleoclimates of El’gygytgyn Lake contemplates the study of different genetic types of sediments established in its basin. The lake, which provided one of the longest continuous climatic records of the Arctic Region, was formed about 4 Ma ago when a meteorite fell in the northern Chukchi Peninsula in the region of 67 ° 30 � N, 172 ° 05 � E [1]. The region belongs to a mountainous variant of a typical tundra subzone [2]. Slopes of the Anadyr Tableland surrounding the lake are occupied by the undershrub‐ lichen tundra. Dwarf birch and willow are encountered on protected areas in valleys of the Enmyvaam River flowing out of the lake and its tributaries (the Anadyr River system). Present-day climatic parameters for El’gygytgyn Lake are as follows: the average temperature is +8.3 ° C for July and ‐28.4 ° C for January; average precipitation is 47.4 mm in July and 21.5 mm in January. A series of radiocarbon ages (figure) accompanies the palynological and paleocarpological analyses of loose deposits exposed in the scarp of the 4-m terrace of the Ol’ga Creek running into the Enmyvaam River on the left at a distance of 1 km from the lake (67 ° 26 � 45 � N, 172 ° 13 � 14 � E). The first age (9125 ± 30 years ago, MAG-994) in this series was established for a large trunk of alder ( Duschekia fruticosa ) found in peat at the depth of 163 cm (figure). This age and two other ages for fragments of shrub branches: 9250 ± 90 years ago (MAG-1477), at the depth of 172 cm, and 8120 ± 25 years ago (MAG-1478), at the depth of 150 cm, allow for correlating the peat formation time with the Boreal interval of the Holocene. The age 7770 ± 50 years ago (MAG-1480) established for plant remains from the depth of 109 cm indicates that peat with sand lenses (figure, Bed 5) formed during the period corresponding to the Atlantic interval of the Holocene. The spore-and-pollen diagram of deposits on the terrace comprises three pollen zones (figure). Subdivision of zones is determined by variations in the content of main pollen taxons and each spore taxon calculated in percent out of the total pollen. It is significant that in contrast to spectra of sediments from El’gygytgyn Lake represented by pollen brought by wind from the Anadyr Tableland [1], peat spectra reflect local plant communities. Pollen zone 1 is distinguished as a zone of birch (figure). It is similar to birch pollen zones in climatic records of Beringia lakes and reflects a response of the vegetation cover to climate warming in the period transitional from the Pleistocene to the Holocene [3]. Spore-and-pollen spectra of the zone underline a wide distribution of such shrubby birch species as Betula middendorffii, B. exilis, and B. fruticosa that replaced herb communities of the Last Glaciation [3].

The pollen record from El’gygytgyn Lake: implications for vegetation and climate histories of northern Chukotka since the late middle Pleistocene

Three types of pollen assemblages (shrub-dominated, mixed herb- and shrub-dominated, and herb-dominated) characterize the ~ 300,000 year palynological record from El’gygytgyn Lake. Despite major changes in global climatic forcings, all pollen spectra, with a few isolated exceptions, have strong to possible analogs in the modern plant communities of Northeast Siberia and Alaska. Paleoclimatic reconstructions based on squared chord-distance analog analyses indicate two periods (~8600–10,700 14C year B.P. and OIS 5e) when summers were perhaps ~2 to 4°C warmer than modern. January temperatures were also warmer than present, and both July and January were wetter than today. Palynological data remain inconclusive as to the establishment of forests near El’gygytgyn Lake at these times. The wettest Julys occurred during OIS 5 d. July temperatures were near modern, and Januarys were colder and drier than now. January temperatures, even into the Middle Pleistocene, generally show little variability, suggesting that the suppression of arboreal taxa during glaciations was likely caused by cool summers with low effective moisture and not by frigid winters. Because age schemes that correlate magnetic susceptibility to variations in summer insolation or ∂18O have cool plant taxa persisting in warm times (and vice versa), we propose an alternative age model based on the palynological data.

Pliocene to Holocene geomorphic evolution and paleogeography of the El’gygytgyn Lake region, NE Russia

Geomorphic, lithologhic, and stratigraphic field studies as well as pollen data and mineralogical study have been used to propose Pliocene and Pleistocene paleogeographic reconstructions of the El’gygytgyn meteorite crater area. The moment of impact is recorded above the early Pliocene hill denudation plain as a “chaotic horizon” consisting of fragments of impactite rocks. This chaotic horizon lies between layers of late Pliocene alluvial sediments. During the second half of the late Pliocene, the region was tectonically active, when the Anadyr lowland was uplifted causing alluvial sediments to accumulate in the basins to the south of the crater. Regional climatic cooling, which supported the spread of tundra and the formation of permafrost is characteristically to late Pliocene. The 35–40 m high terrace that roughly follows the 530 m contour interval along the Enmyvaam River formed during the middle Pleistocene. This terrace represents the maximum lake level. Erosion and incision of the upper Enmyvaam River increased due to another wave of uplift. Additionally, El’gygytgyn Lake discharge increased causing lake level to begin to drop in the Middle Pleistocene. Cooling continued, which led to the development of herb-dominated arctic tundra. middle and late Pleistocene glaciations did not reach the El’gygytgyn lake region. The 9–11 m high lacustrine terrace was formed around the lake during the late Pleistocene and the 2–3 m high lacustrine terrace formed later during the Holocene. During the last 5000 years, the lake level has continued to drop as the modern coastline developed.

Inorganic geochemistry of El’gygytgyn Lake sediments (northeastern Russia) as an indicator of paleoclimatic change for the last 250 kyr

The inorganic geochemistry of sediments from El’gygytgyn Lake shift in phase with interpreted paleoclimatic fluctuations seen in the record over the past 250 ka. Warm periods, when the lake was seasonally ice free and fully mixed, are characterized by increased concentrations of SiO2, CaO, Na2O, K2O, and Rb, by decreased contents of TiO2, Fe2O3, Al2O3, and MgO, and by a lower chemical index of alteration (CIA). Increased levels of SiO2 reflect increases in limnic productivity whereas many of the other elements and the CIA likely reflect increased hydrological activity coincident with an increase in coarser sand and silt content and a decrease in clay mineral content. For cold/cooler periods when perennial lake ice cover lead to a stratifed water column and anoxic bottom waters, the opposite is generally observed suggesting a decrease in hydrological activity and an increase in post-depositional chemical alteration.