The Okinawa Trough (OT) is a back-arc basin related with the plate subduction since the late Miocene (9 to 6 Ma), and its depositional evolution can be divided into 3 stages, stage Ⅰ from the late Miocene (9 to 6 Ma) to the late Pliocene (2 Ma), stage Ⅱ from the late Pliocene (2 Ma) to the late Pleistocene (130 ka) and stage Ⅲ from the Pleistocene to the present. It is shown from the study results that the northern OT developed earlier in the late Miocence and has a low degree of depositional evolution, then the middle OT developed and has a high degree of depositional evolution, and the southern OT developed later in the late Pliocene and has a high degree of deposional evolution. At the present stage, the northern OT is in a decline phase, and the middle and southern OT is in a broadening phase. The tectonic activities play a leading role in the basin evolution because these activities built up the initial depositional framework of the basin in a geologic period of considerable length and provided some sediments (volcanic and hydrothermal materials) to the basin. During the intense tectonic activity period, the effect of crust extension on sedimentary sequence was greater than that of sedimentation, and during the weak tectonic activity period, the relative sea level changes controlled the variations in internal depositional structure of the basin.

Trough (economics)

Early Pleistocene

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Characteristics and Tectonic Interpretation of Magnetic Anomalies in the Jiaozhou Bay Mouth Sea Area

Haiyang kexue jinzhan (2006)

Pei Yan-liang Baohua Liu Xishuang Li Chenguang Liu Zhao Yue-xia

It is shown from the interpretation results of magnetic anomalies and the analysis results of other geologic and geophysical data in the Jiaozhou Bay mouth sea area that there are a NW trending fault,2 NWW trending faults and 3 NE trending faults in the survey area.Among them,a NW trending fault F3 is a new found fault with a right-lateral fault structure,and was filled by several kinds of medium-basic dikes.It is concluded from the combination and intersection relations of fault structures in the area that the active age of fault F3 is earlier than that of the Cangkou Fault,and the fault F3 is not a Holocene active fault.

Dike

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