San Francisco State University, United States

Basin development during the Miocene in the Northwest Pacific Region was complex. In the Japan Sea and southwestern part of Sakhalin Island, pull apart basins developed in the early-middle Miocene between two dextral faults. In the eastern margin, basins were influenced by en echelon grabens formed in a 200 km dextral shear zone. During the Miocene, basin development was influence by volcanism to the west and southeast, rifting in the southeast and southwest compression from the eastern Sea of Okhotsk Block, and shear faulting. Sedimentation in the individual basins was influenced by rivers from the Asian continent, ice rafting, and biogenic sedimentation. This study looks at the Schmidt Peninsula, Makarov, and Pogranichyni regions and compares clastic and biogenic sedimentation of these basins with published data from ODP Legs 127, 128 and 145. The North Basin (Schmidt Peninsula) during the Miocene was created by shear faulting. The Miocene sediments are represented by five formations whose major influence was deltaic from the paleo-Amur River. The onset of radiolarians and diatom deposition signals basin deepening in middle to late Miocene. The Pogranichyni area is part of the East Sakhalin Basin and influenced by en echelon faulting. Characteristics of Miocene sediments include sandstones with boulder size carbonate concretions, tuffaceous sandstones, and pebbly mudstone. Terpeniva Basin in the Makarov region has volcanic deposits in the early Miocene, with sandstones and mudstones deposits throughout middle-late Miocene. Diatomaceous mudstones are found from middle to late Miocene.