丹沢山地北縁の地質構造
スポンサーリンク
概要
- 論文の詳細を見る
The area investigated occupies the northern periphery of the Tanzawa Mountainland and the southern border of the Kanto Mountainland. The area consists mostly of the molasse type sediments related to the so-called "Green Tuff Orogeny". Geologic structure, however, is very complicated because of the development of various types of faults. In this study, the writer intends to settle the stratigraphy and to clarify the geologic structure of this region. The results obtained are summarized as follows: 1. Stratigraphy. (1) The Hinate andesite is interfingered with the Shimada mudstone, and consequently belongs to the Nishikatsura group (the Iwadono-san formation). (2) The Nakama-gawa boulder conglomerate is a heteropic but contemporaneous facies in the upper part of the Tsuru-kawa conglomerate. (3) Both the Ohkura andesite and the Nagura basalt, which are exposed in the "Green Tuff Lenticular Zone", may belong to the Tsuru group. 2. Geologic structure. (1) Folds: Folds developed in the Pre-Neogene strata are "closed", and those in the Neogene are divided genetically into two types. One is the product of dragging related with the movement of the Tohnoki-Aikawa Tectonic Line, and the other is of the oscillatory movement of basement rocks. (2) Fracture systems: (A) Fractures are mostly developed along the boundary of the groups, and are divided into three systems, that is, (a) The Tohnoki-Aikawa Tectonic Line and longitudinal faults harmonious with it, (b) transverse faults, and (c) other faults. (B) Minor faults are developed generally in this area, and they have different tendencies in different formations. Conjugate faults are rare. 3. Tohnoki-Aikawa Tectonic Line. (1) At least the following two phases of the Tectonic Line are recognized, that is, the Middle to Late Miocene, and the Quaternary. (2) The thrusting of this fault is confirmed to be accompanied with left-lateral displacement at the west of Ohtsuki, and with right-lateral one at the east of Uenohara. (3) "Green Tuff Lenticular Zone" might be a relatively depressed belt along the high-angle faults occurred at the crest of anticline, which resulted from the dragging by the thrusting of the Kobotoke group. (4) The location of the Tohnoki-Aikawa Tectonic Line might be determined by the outline of the Neogene Tertiary basin and the distribution of the quartz-diorite intrusions exposed and/or concealed.
- 日本地質学会の論文
- 1976-12-30