新潟油田地域の褶曲 : 形態と形成過程  [in Japanese] Folds of Niigata oil fields and their folding process  [in Japanese]

新潟油田における新第三系の褶曲は, (1)基盤までを含んだ褶曲と, (2)浅層(椎谷層以上の地層)が著しい褶曲を示すのに比べて, 七谷層以下が緩い構造を示すような褶曲とがある。新津・角田の背斜は, 西山期から基盤が東側に断層を伴いながら傾動する事によって作られた基盤を含む構造である。上昇地塊の下盤側に圧縮の応力場ができて, これによって椎谷層中のCompetent層が挫屈して桑山の背斜ができた。宮川〜東山の断面では, 七谷層はゆるい褶曲を示す. 椎谷層より上位の地層は寺泊層中の泥質岩を滑り面として激しい圧縮性の褶曲を示す。西山層の泥質岩の一部は流動によって背斜を形成している。

There are two types of folds in Niigata Oil fields; (1) basement involved folds, (2) supraficial folds detached from underlying gently folds with under compacted mudstones. Niitsu and Kakuta anticlines are the basement involved structure. The uplifting and tilting of the basements tarted at the time of deposition of Nishiyama formation. The uplifting block were thrust up to the east. This thrusting initiated the compressional stress field within the foot wall, and made the competent beds in Shiiya Formation to buckle into Kuwayama anticline In B-B' section, the deformation of Nanatani Formation is gentle. The Shiiya Formation and its overlying formation were folded severely. The Teradomari Formation, which is sandwiched between severely folded Shiiya Formation and gently folded Nanatani Formation, has lower shearing strength and acts as the lubricants during thefolding deformation. Parts of the Nishiyama Formation deformed in mobile plastic mudstones and caused the anticline in overlying formations.