Initial Results of a Rock Magnetic Study from Core LZ-1029, Lake El'gygytgyn, Northeast Siberia
Abstract
Lake El’gygytgyn, located in northeast Siberia, formed from a meteorite impact some 3.6 million years ago. Since that time it is thought to have never been glaciated, providing a sink for continual sedimentation since the mid Pliocene. An international team of geoscientists has recently drilled deep into the lake recovering over 350 meters of lake sediment for paleoclimate studies. Initial studies on shorter cores from the lake have previously shown it to be a valuable resource in understanding past climates, but has also raised several questions. Core LZ-1029 shows a wide range of magnetic susceptibility, unlike what is usually found in lacustrine environments, and members of the Lake E team have postulated several theories as to the reason. One explanation for the exceedingly low susceptibilities is the possible dissolution of magnetite due to severe anoxia. In this study, we investigate rock magnetic properties of samples from Core LZ-1029 to better understand the varying susceptibility levels. Magnetic behavior of samples at low temperatures was investigated using a MPMS instrument. Samples from the low susceptibility areas showed imperfect Verwey transitions indicating the presence of magnetite mixed with another magnetic mineral, possibly hematite. At lower temperatures (~10 to 30K) some samples exhibited another transition, implying the presence of other magnetic minerals, probably siderite and/or vivianite. If minerals such as these are present, the environments in which they form will help to determine whether or not the conditions were anoxic. Continued investigation of additional rock magnetic properties, optical and SEM investigation of sediment samples, and correlations with geochemistry are underway to better understand the climatic variations affecting this lake.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMGP13B0778M
- Keywords:
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- 1540 GEOMAGNETISM AND PALEOMAGNETISM / Rock and mineral magnetism