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Volcanic influence of Mt. Fuji on the watershed of Lake Motosu and its impact on the lacustrine sedimentary record

By Laura Lamair, Aurelia Hubert, Shinya Yamamoto, Meriam El Ouahabi, Jacqueline Vander Auwera, Stephen Obrochta, Evelien Boes, Atsunori Nakamura, Osamu Fujiwara, Masanobu Shishikura, Sabine Schmidt, Giuseppe Siani, Yosuke Miyairi, Yusuke Yokoyama, Marc De Batist and Vanessa Heyvaert

Abstract

Lacustrine sediments are particularly sensitive to modifications within the lake catchment. In a volcanic area, sedimentation rates are directly affected by the history of the volcano and its eruptions. Here, we investigate the impact of Mt. Fuji Volcano (Japan) on Lake Motosu and its watershed. The lacustrine infill is studied by combining seismic reflection profiles and sediment cores. We show evidence of changes in sedimentation patterns during the depositional history of Lake Motosu. The frequency of large mass-transport deposits recorded within the lake decreases over the Holocene. Before ~8000 cal yr BP, large sublacustrine landslides and turbidites were filling the lacustrine depression. After 8000 cal yr BP, only one large sublacustrine landslide was recorded. The change in sedimentation pattern coincides with a change in sediment accumulation rate. Over the last 8000 cal yr BP, the sediment accumulation rate was not sufficient enough to produce large sublacustrine slope failures. Consequently, the frequency of large masstransport deposits decreased and only turbidites resulting from surficial slope reworking occurred. These constitute the main sedimentary infill of the deep basin. We link the change in sediment accumulation rate with (i) climate and vegetation changes; and (ii) theMt. Fuji eruptions which affected the LakeMotosu watershed by reducing its size and strongly modified its topography. Moreover, this study highlights that the deposition of turbidites in the deep basin of Lake Motosu is mainly controlled by the paleobathymetry of the lakefloor. Two large mass-transport deposits, occurring around ~8000 cal yr BP and ~2000 cal yr BP respectively, modified the paleobathymetry of the lakefloor and therefore changed the turbidite depositional pattern of Lake Motosu.Peer reviewe

Topics: Lake Motosu, Mount Fuji, Volcano, Mass-transport deposits, Turbidites, Sediment accumulation rate, Turbidites, Physical, chemical, mathematical & earth Sciences :: Earth sciences & physical geography, Physique, chimie, mathématiques & sciences de la terre :: Sciences de la terre & géographie physique
Year: 2018
OAI identifier: oai:orbi.ulg.ac.be:2268/219598
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