Abstract
Major and trace elements of ninety-two coastal beach sands samples, collected along the San’in region of southwest Japan, were determined by X-ray fluorescence to define their geochemical characteristics. These included Yamaguchi (n=27), Shimane (n=50), and Tottori (n=15) beach sands samples. Data of beach sands from Shimane and Tottori normalised averages show approaching patterns relative to the upper crust of the Japan arc UCJAN, and upper continental crust UCCN, reflecting the composition of the source rocks that dominate their watersheds. In contrast the normalised patterns for most elements of Yamaguchi beach sands samples are less than 1 except for CaO, Sr, and Th. The primary component of beach sands from Shimane is quartz, or silica (SiO2), Sands from Tottori are composed essentially of weathered particles of feldspar, and in contrast components of biogenic and quartz-rich sands from Yamaguchi are primarily shell fragments, quartz, and igneous rock.
Highlights
1.1 Background and ObjectivesThe Japanese Islands have complex coastal landforms, where mountains and hills meet the sea in composite geometries; the total length of Japan’s coastline is roughly 35,000 kilometres
Our study suggests that pocket beaches are common on the coastline of the Inner Zone of southwest Japan, which generally coincides with the southwestern Mountain arc, and the inclusive trend of highlands and lowlands roughly convex toward the Sea of Japan, this is clear contrast to those on the Outer Zone of Southwest Japan
Yamaguchi coastal beach sands samples have low to high SiO2 contents, with abundances ranging from 4.72 wt% to 92.16 wt%, and averaging 60.32 wt%
Summary
1.1 Background and ObjectivesThe Japanese Islands have complex coastal landforms, where mountains and hills meet the sea in composite geometries; the total length of Japan’s coastline is roughly 35,000 kilometres. The southwestern region of Japan, which includes western Honshu (Chūgoku), as well as Shikoku and northern Kyushu, is divided into two distinguishing domain separated by the Median Tectonic Line-MTL (Ito et al, 2010): comprising the Inner and the Outer Zones. Our study suggests that pocket beaches are common on the coastline of the Inner Zone of southwest Japan, which generally coincides with the southwestern Mountain arc, and the inclusive trend of highlands and lowlands roughly convex toward the Sea of Japan, this is clear contrast to those on the Outer Zone of Southwest Japan. The Tsushima Coastal Branch Current enters the Sea of Japan through the Eastern Channel of the Tsushima Strait and moves northeast along the San’in Coast (Inoue et al, 2007). The current has presumably had a deep impact on the Quaternary paleoclimate, paleoenvironment and ecosystem within and around the Sea of Japan (Akihisa et al, 1997)
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