Geologic structures and boundary faults along the western margin of the Odate Basin, Northeast Japan

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Abstract

Under conditions of horizontal shortening tectonics, active reverse faults and flexures often occur between a basin and its surrounding mountains. The purpose of this paper is to evaluate the existence of active faults between those two landforms on the western margin of the Odate Basin, the inner zone of the Northeast Japan Arc, on the basis of the Upper Cenozoic geologic structures and the succession of the sedimentary basin. The Miocene rocks covering the investigated area are the Fujikuragawa Formation consisting of hydrothermally altered andesitic to dacitic lava, the upper member of the Hayaguchigawa Formation composed of interfingering pyroclastic rocks and andesitic lava, and the Ittori Formation comprising dark gray to black mudstone deposited in the middle bathyal zone, in ascending order. Fluvial higher terrace surfaces, that is, O-H Surfaces of Middle Pleistocene age, are slightly recognized on the hilltop along the margin. Inside the basin, the Alluvial deposits and Latest Pleistocene and Holocene pyroclastic flow deposits are widely distributed. The boundary faults on the western margin of the Odate Basin, such as the Niida Fault, are certain to have been inverted to reverse faults after the deposition of the Ittori Formation, namely, in the earliest Pliocene. The basin is inferred to have been a sedimentary basin accompanied by reverse faults probably during Pliocene to Early Pleistocene time, because Middle to Upper Miocene formations in front of the faults underwent horizontal shortening deformation. On the other hand, no distinct reverse fault is currently confirmed to exist along the western fringe of the basin, especially close to the frontal margin of the surrounding mountainous and hilly areas, from the Upper Cenozoic structures. It is concluded that the Odate Basin and its surrounding areas are dominated by gentle uplift-subsidence at present with no relation to faulting.

Original languageEnglish
Pages (from-to)37-54
Number of pages18
JournalScience Reports of the Tohoku University, Series 7: Geography
Volume49
Issue number1
Publication statusPublished - 1999 Dec 1

Keywords

  • Active fault
  • Boundary fault
  • Horizontal shortening
  • Late Cenozoic
  • Northeast Japan Arc
  • Odate Basin
  • Sedimentary basin

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

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