手取層群で確認された三番目の海進相 : 岐阜県飛騨市古川町周辺に分布する手取層群について  [in Japanese] Discovery of a third marine transgression in the Tetori Group based on the restudy of stratigraphy of the group in Hida : Furukawa region, Gifu Prefecture, Japan  [in Japanese]

飛騨市古川町地域に分布する手取層群を下位より種村層,沼町層,杉崎層/栃尾層,太江層,稲越層に区分した.アンモナイトの産出により稲越層はHauterivian階〜Barrremian階に対比される.また,杉崎層からも海生二枚貝類が産出するので,本地域の手取層群では2回の海進が認められた.種村層から稲越層への層序は,Tithonian期〜Barremian期を示す.これにより,手取層群では,ジュラ紀中期のBathonian期〜Oxfordian期,ジュラ紀-白亜紀境界のTithonian期〜Berriasian期,白亜紀のHautervian期〜Barremian期の3回の海進が認められた.稲越層から産するアンモナイトの類縁種と海生二枚貝化石の同種が中国黒竜江省東部の云山層から産出するので,Hautervian期〜Barremian期に手取地域と中国黒竜江省東部は共に北からの海流の影響を受けたことが示された.

The Tetori Group is distributed in the Hida-Furukawa area. There are diverse opinions about the stratigraphy of the group. So, we restudied the stratigraphy of the group. The group can be divided into six formations: the Tanemura, Numamachi, Sugizaki/Tochio, Taie and Inagoe in ascending order. The geological map of the area was revised to show the distribution of these six formations. These formations are suggested the environments of alluvial fan to shallow marine, shown by deposits transported from the eastern hinterland and fossil evidence. Ammonite indices suggesting Hauterivian to Barremian age occur in the Inagoe Formation. This shows the evidence of the third marine transgression in the Tetori Group. As marine bivalves including inoce- ramids occur in the Sugizaki Formation as well, two marine transgressions can be recognized in the Tetori Group in this area. Consequently, three sequential marine transgressions: Bathonian to Oxfordian, Tithonian to Berriasian, and Hautervian to Barremian, can be recognized in the Tetori area. In the eastern part of the Heilongjiang, China, two marine transgressions, the first from late Oxfordian to Volgian (= Tithonian to early Berrriasian) and the second from Barremian to Aptian, are recognizable. Therefore, these marine transgressions in China correspond to these in the Tetori area. Occurrence of common marine bivalve species and related ammonite species suggests the same realm for both the eastern part of the Heilongjiang, China and the Tetori area, Japan, during Hauterivian to Barremian time. These faunal compositions are different from those of areas in the southwest of Japan influenced by currents from low latitudes. This supports the idea that a peninsula of land was present between both the Tetori area and areas in southwest of Japan. Thus, both areas of the eastern part of the Heilongjiang and the Tetori area were influenced by current from the high latitude.