Abstract
Neogene to Quaternary tectonic history and geologic structures since the Pliocene in the Tsugaru Peninsula, northeast Japan, are reviewed.
Neogene to Quaternary tectonic history in the Tsugaru Peninsula resembles those in other areas of the inner zone of the northeast Japan Arc. In the early Miocene, green tuff was formed by the volcanic activity accompanying the formation of the Japan Sea. The paleo-environment of the Tsugaru Peninsula changed from shallow marine to deep sea in middle Miocene, due to the expansion of the Japan Sea. After the Pliocene, the northeast Japan Arc was under compressive stress field, and reverse faults and domes were developed in the Tsuragru Peninsula. The topography of the Tsugaru Peninsula consists of three uplifting zones and two lowlands, reflecting those geologic structures.
Faults and flexures parallel with the Tsugaru Fault in the southeastern part of the Tsugaru Peninsula suggest the migration of a deformation belt toward the east, and the expansion of the land area, since the Pliocene. There is no major fault in the western margin of the Tsugaru Mountains, except for the Western margin of Tsugaru Mountain Fault. A buried anticlinal axis might be present under the terrace deposits in the southwestern margin of the Tsugaru Peninsula.
