Japan Geoscience Union Meeting 2015

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Oral

Symbol M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS32] Drilling Earth Science

Sun. May 24, 2015 9:00 AM - 10:45 AM 304 (3F)

Convener:*Saneatsu Saito(Japan Agency for Marine-Earth Science and Technology), Katsuyoshi Michibayashi(Institute of Geosciences, Shizuoka University), Tetsuro Hirono(Department of Earth and Space Science, Graduate School of Science, Osaka University), Keita Umetsu(Japan Agency for Marine-Earth Science and Technology), Chair:Keita Umetsu(Japan Agency for Marine-Earth Science and Technology), Junichiro Kuroda(Institute for Research on Earth Evolution, )

9:45 AM - 10:00 AM

[MIS32-04] Holocene sedimentation in estuaries of the Baltic Sea (Exp. 347)

*Stephen OBROCHTA1, A.T. Kotilainen2, O. Hyttinen3, T. Andren4, D. Ryabchuk5, I. Snowball6, Y. Yokoyama7, 347, Science party EXP.8 (1.Akita University Faculty of International Resource Science, 2.Geological Survey of Finland (GTK), 3.University of Helsinki, Department of Geosciences and Geography, 4.Sodertorn University, School of Natural Sciences, 5.A.P. Karpinsky Russian Research Geological Institute (VSEGEI), 6.Uppsala University, Department of Earth Sciences - Natural Resources and Sustainable Development, 7.University of Tokyo Atmosphere and Ocean Research Institute, 8.International Ocean Discovery Program (IODP))

The IODP Expedition 347 "Baltic Sea Paleoenvironment" drilled two sites in the Angermanalven River estuary. Sites M0061 and M0062 are located in an area that was deglaciated ca. 10 ka ago. It has long been known that varves continue to form in this estuary and previous work has shown that a correlation exists between maximum daily discharge and mean varve thickness at least AD 1901-1971 in the Angermanalven River. One aim of the IODP drilling was to recover a uniquely long varve record from the two sites in Angermanalven and study varve thickness and sediment geochemistry, potentially yielding estimations on past changes in discharge and sedimentation processes in the estuary.
In this presentation, we show the preliminary results from site M0062. The core recovery was ~ 36 m and the sediment sequence was divided into two lithological units. Unit 2 (17.09-35.9 mbsf) consists of well-sorted sand, deposited by a (glacio)fluvial system. Unit 1 (0-17.09 mbsf) contains a transition from clastic varves typical of a glaciolacustrine environment to couplets characteristic of a glaciomarine, or brackish environment. The uppermost 18 metres were analysed for grain-size and elemental geochemistry every 0.3-0.5 m. The uppermost 26 m were scanned by XRF at 1-cm resolution, and select intervals at 1-mm resolution.