北海道北部幌延町における地球化学的特徴を用いた侵食量の推定

Estimation of erosion amount by geochemical characteristic in the Horonobe area, northern Hokkaido

高橋 一晴; 新里 忠史  ; 安江 健一; 石井 英一   

Takahashi, Kazuharu; Niizato, Tadafumi; Yasue, Kenichi; Ishii, Eiichi

石油探鉱が行われている地域では、堆積岩中に含まれる自生鉱物を利用して埋没深度の推定や削剥(侵食)量を推定する試みが行われているが(例えば、天然ガス鉱業会・大陸棚石油開発協会、1982など)、侵食速度までの推定は行われていない。ここでは、北海道北部の幌延地域を対象として取り組んでいる、シリカ鉱物による侵食速度の推定手法および有機物を用いた侵食速度の推定手法の概要とその適用事例について紹介する。

This article presents the results of the estimated amount of erosion and uplifting based on mineralogy and organic geochemical characters of the Neogene siliceous rock (Wakkanai and Koetoi Formations) in Horonobe. As a result of the transformational change of silica minerals, it was clarified that the erosion amount was about 0.66 [m ky] or more at the large uplift site, and was about 0.21 [m ky] or more at the small uplift site at Hokushin region, Horonobe area. In this case of the correlation with the palaeo-geothermal temperature and the sterane/sterene ratio, the ratio is effective measure to estimate the burial depth and erosion amount. We think that the estimation of the amount of erosion and uplifting became possible in high a resolution by the organic geochemical character.