Rifting and basin inversion in the eastern margin of the Japan Sea

Abstract

Extensional basin formation and subsequent basin inversion in the southern area of the eastern margin of the Japan Sea were studied on the basis of the interpretation of seismic profiles (total length approximately 15 000 km) and the fossil analyses of 77 sea-bottom samples. Rift (Early to Early Middle Miocene), post-rift (Middle to Late Miocene), pre-inversion (Late Miocene to Pliocene) and inversion stages (Pliocene to Quaternary) were differentiated by the extension and contraction of the crust. Many small-scale rifts were formed in the Sad0 Ridge and the Mogami Trough during the rift stage, simultaneous with back-arc spreading of the Japan Sea. Most of the rifts were east-or southeast-facing, rotational half-grabens bounded by west-dipping normal faults at their eastern boundaries. The syn-rift sequence can be divided into lower and upper units by an erosional surface. The sequences are presumed to be composed mainly of fining-upward sediments. The trend of most rifts is north-northeast with the remainder being of east-northeast-bias. The north-northeast trending rifts are distributed widely in the Sad0 Ridge and Mogami Trough and do not show an en bchelon arrangement, suggesting that they were formed mainly by pure extension nearly perpendicular to the arc. The east-northeast trending rifts are presumed to have been developed by a north-northwest extension in the late rift stage, which may have accompanied a right-lateral movement in the eastern margin of the Japan Sea. During the post-rift stage, the rifts and adjacent horsts subsided and became covered by the post-rift sequence, characterized by parallel and continuous reflections. This suggested no significant tectonic movements in this period. In the pre-inversion stage many of the rifts subsided again, presumably because of down-warping due to weak compressional stress. The normal faults reactivated as reverse faults during the inversion stage due to an increase in compressional stress. Many of the rifts have been uplifted and transformed into east-vergent asymmetric anticlines. The basin inversion is greatest in the Sado Ridges and in the Dewa Bank Chain, while it is least developed in the Mogami Trough and in the western slope of the Sad0Ridge, in which some normal faults have not been reactivated. The increase and decrease of the inversion corresponds to the peak and trough of undulation at an interval of about 50 km trending parallel to the arc.

The cause of the east–west contraction of Northeast Japan

“…The E-W contraction causes segmentation of the upper crust of NE Japan separated by a large number of N-S trending reverse faults, which results in its topography (Okamura et al, 1995;Sato, 1989;Sato, 1994;Sato et al, 2002). The Niigata Prefecture Chuetsu Earthquake (Mw = 6.6) in 2004 is a typical example of the inland earthquakes generated by such crustal deformation.…”

Tectonic Process of the Sedimentary Basin Formation and Evolution in the Late Cenozoic Arc-Arc Collision Zone, Central Japan

“…From this point of view to the plate tectonic condition around Japan, the central Japan acts as a multiple junction area unique in the earth, where four pieces of plates, such as the Amur, the Okhotsk, the Philippine Sea, and the Pacific plates, gather and converge together in and around the Japanese archipelagoes ( Figure 1). Although the GPS geodetic observations confirmed the presence of the micro-plates [3][4][5], the structural features of the incipient boundary between the Okhotsk and Amur Plates seemed still immature but recognized as strain accumulated zone along the eastern margin of Japan Sea [6][7][8][9][10][11].…”

“…A fault province composed of active faults is called an active fault province which reflects regional characteristics of the seismogenic stress field. From this point of view to the recent crustal movement regionally in a geodetic to geological time scale, a strain concentration zone denotes a geodetic zone where a pattern of displacement field demonstrates a belt of larger strain rate, and geologically it corresponds to a zone where deformation structures such as faults and/or folds develop intensively [6,9,19,20].…”

北部フォッサマグナ新潟～信越堆積盆頸城地域の上部新第三系難波山層～名立層層準のシーケンス層序とタービダイトシーケンス

“…5 ,1985, 1985 , 1989 , , 1976; , 1979; , 1982, 1992; , 1993; , 2000; , 2004 Fig. 2Gamma Ray: GR Spontaneous Potential: SP Resistivity Van Wagoner et al, 1990;Vail and Wornardt, 1991;, 1995; Emery and Mayers, 1996 1995Mitchum et al, 1977 , Fig. 1 , 1982, 1992, 1988a, 1996 J90-A , 1993, 1996 Figs.…”

“…This characteristic pattern of turbidite sequence succession seems to vary in response to the submarine-fan type; e.g., sandy radial fan and channel levee system. The present results represent fundamental information for basin-wide correlations and the reconstruction of tectono-sedimentary processes of the Fossa Magna region.Keywords: sequence stratigraphy, depositional sequence, Nambayama Formation, Kubiki area, Niigata-Shin etsu basin, submarine-fan turbidites , 1995; Takano, 2002a Takano, , b , 1983, 2002, 2002-Sagiya et al, 2000, 2002Otofuji et al, 1985 Kato, 1992;, 1995 Okamura et al, 1995;Okamura, 2003 Okamura, , 1982 Okamura, , 1992, 1992;, 1992; , 1997, , 1994 Hoyanagi and Nishimura, 1994;, 1995;, 1995, 1998 Arato, 1997; , 1998, 2001; Takano, 2002a; Hoyanagi, 2004 Posamentier et al, 1988; Allen, 1999 Vail et al, 1991;Prosser, 1993; Dennison and Ettensohn, 1994;, 1995 5000 m 5000 m , 1990 …”