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with help from: |
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with help from: |
Elgygytgyn Lake, located 100 km north of the Arctic Circle (67° 30' North latitude and 172° 05' East longitude) in northeast Russia (See Beringian map), was created about 3.6 million years ago by a meteorite impact that generated a crater roughly 23 km in diameter. The lack of glaciation in this basin makes it highly likely that the modern lake, measuring some 15 km across and 175 m deep, contains a continuous record probably back to the time of impact. We believe that, eventually, an international, multidisciplinary project to collect and analyze core materials from this lake will provide a paleoclimate record unparalleled in northern Asia. It is likely to become a key lacustrine archive, among a necessary network of global sites for the reconstruction of past climate on several time scales. The expense of such an undertaking, however, cannot be justified without prior knowledge of the nature of the sediments (organic versus inorganic content; pollen preservation; microfossil preservation, etc.) and, at a minimum, knowledge of late Pleistocene and Holocene sedimentation rates. An important question is whether the sediments in this lake are varved, preserving a record with annual resolution of regional paleoclimate.
During the Spring of 1998, we conducted a limited pilot study of Egygytgyn Lake to determine whether or not it contains a profitable sediment record for high-resolution paleoclimatic investigations. The field team consisted of:
The field team was assembled in Magadan, Russian, on April 24, 1998. We then chartered a Magadan Airlines cargo plane to Pevek, a closed gold mining town on the arctic coast on April 29. On May 1, we deployed two Russian Aeroflot MI-8 helicopters from Pevek to Elgygytgyn Lake with six field members and over 2,100 kg of coring equipment and gear. Coring operations and seismic work took place from May 2 until May 15 when we were picked up by helicopter to return to Pevek. We sincerely wish to acknowledge the help of the administration and personnel at the Geological Mining Institute in Pevek for making our transfers in Pevek go smoothly.
CORING:
The field team successfully penetrated to 12.5 meters in 175 m of water on Lake Elgygytgyn -- this is a new record for the coring equipment as far as we know. In total we collected 23 m of core in liners (several cores with overlapping sections) and about 2 m sectioned in vials. The AWI coring system, championed by Paul Overduin and Artur Zielke, is a percussion piston corer that collects cores in 3 m sections using a 20 kg. hammer. The sediment/water interface was sampled using a simple gravity corer and we then sliced the poorly consolidated sediments into vials at high resolution intervals. For our expedition, the AWI had a huge bright yellow tent custom-made to fit over the entire coring operation and this made it possible to work comfortably despite daily temperatures of -10 to -15 C and semi-constant north/south winds of 5-10 mph. Even on the few days we had >20 mph winds and temps of -15 C, the tent produced a nice greenhouse in which we could work with bare hands without bulky clothes. See photos for a look at the tent.
The sediment cores will be split and subsampled by members of the field team plus Martin Melles at the AWI-Potsdam between July 16 and August 8, 1998. Analyses of the core materials, following the PALE protocols (see http://www.ngdc.noaa.gov/paleo/pale/index.html), will take place over the next 6-12 months.
SEISMIC:
In an attempt to determine the total thickness of post-impact sediments in the lake, we attempted to conduct seismic work from the frozen lake surface. Under the direction of Matt Nolan, we used a standard Bison Instruments Model 7012 (series 7000) Seismograph with a Betsy Buffalo "gun"(with 12 gauge shells) shot into the lake water to create a signal. We also tried a 12 kg sledge hammer on a metal plate directly on the ice but this was not very effective. The signal was received by a string of 12 geophones set out at 25 m intervals over 300 m. These we cemented to the ice surface, sometimes digging pits into over a meter of hardpacked snow to get to the ice surface. The Betsy was shot into a hole drilled through the 2.5 m of lake ice. The seismograph was run off a 12 volt battery and data was stored and downloaded onto a laptop computer.
It is likely that the sediments we collected will contain a paleoclimate record of at least the last 20,000 years, a period germane to the goals of the NSF-PALE (Paleoclimate from Arctic Lakes and Estuaries) and ESH (Earth Sysytem History) programs. Based upon sedimentolgical study, microfossil content, a survey of samples for pollen analyses, and several radiocarbon ages, these cores will provide the crucial foundation for assessing the potential of this lacustrine basin to yield to a continuous 3.6 Myr long record.
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| Figure 1. View of El'gygytgyn lake on April 29, 1998, from the west. The crater lake is the large flat area in the upper half of the photo. |
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| Figure 2. Large MI-8 Aeroflot helicopters were used to get the field team from Pevek to El'gygytgyn Lake, some 256 km to the SE, in Eastern Siberia. |
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| Figure 3. By necessity, the field members communicated in three langauges (Russian, German, and English) which required team work and a healthy sense of humor. There was no lack of humor on this expedition! From left to right, Olga Glushkova, Pavel Minyuk, Paul Overduin (squatting), Artur Zielke, Julie Brigham-Grette (kneeling), Matt Nolan. |
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| Figure 4. The field team camped at the coring site nearly in the middle of the lake. The lake ice at this point was 2.5 m thick and water depth was 175 m. The yellow pyramid is the AWI coring tent. |
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| Figure 5. Seismic lines were oriented roughly north-south from the coring sites and extended discontinuously to the north end of the lake, some 5 km away. |
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| Figure 6. Cores were taken in 3 m lengths and then cut into 1 m lengths for transport back to AWI for study by the field team. The cores were kept just above freezing in a large insulted box warmed by an electric blanket operated off of a small Honda generator. Paul Overduin and Artur Zeilke in photo. |
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| Figure 7. Ice cold, but beautiful sunsets after 11 PM from camp on Lake El'gygytgyn. |