Non-Glacial Varved Lake Sediment as a Natural Timekeeper and Detector on Environmental Changes.

DOI Web Site 87 Citations 66 References
  • Fukusawa Hitoshi
    Department of Geography, Faculty of Science, Tokyo Metropolitan University

Bibliographic Information

Other Title
  • 天然の「時計」・「環境変動検出計」としての湖沼の年縞堆積物
  • テンネン ノ トケイ カンキョウ ヘンドウ ケンシュツケイ トシテノ コショウ

Search this article

Abstract

Varve chronologies are regarded as one of the most accurate dating techniques for the Quaternary. In this article, I aim to review the latest investigations on the process of varve formation and to examine the accuracy of varve chronology. As a result, there are three errors on varve counting in time scale: 1) the link to the present, 2) problems of correlation among varve sequences, 3) extra and missing varve.<br>Non-glacial varved sediments during the last 16, 000 years were discovered from four cores in Lake Suigetsu, central Japan. There are marker beds of historical events such as civil engeering for drawing, eruptions, earthquakes and floods in the varved sediments. These marker beds provide isochronous horizons across all depositional environments and are very useful to link the latest age of varved sediments to the present day. In other words, the presence of these marker beds such as a known tephra within different varved sequences would provide evidence for both age and correct correlation. Also, age and duration of the Younger Dryas and the Last Glacial Maximum may be able to be determined in an annual scale by these varve correlations. Varved sediments may be of use as a timekeeper year by year.<br>In Lake Suigetsu, clay mineral composition in bottom varved sediments would be reflected by eolian dust concentrations, transported from Chinese loess plateau, and by precipitation around Lake Suigetsu. Also, formation of iron sulfides and carbonates in varves would be caused by cyclic changes of sea-water invasion, originating from sea-level changes. Annual oscillations of dust and iron mineral concentrations during the last 8, 830 years were detected in varved sequence of SGP 2. Varved sediments may be useful as detectors for annual environmental changes.

Journal

Citations (87)*help

See more

References(66)*help

See more

Keywords

Details 詳細情報について

Report a problem

Back to top