Abstract:

A set of sedimentary strata represented by terrigenous clastic rocks, volcaniclastic rocks and volcanic lava are developed among the metamorphic rocks and Yanshan granites in Eastern Shandong, which leave fierce debates on their ages, sedimentary characteristics and significance of the regional tectonics. This paper presents the characteristics of the strata around the outcrops of Lingshandao, Tangdaowan, Dashangzhuang in Wulian, Shandongtou in Zhucheng, Yakou in Mountain Laoshan. Samples from the Yakou of Laoshan Mountain and Laohuizui of Lingshan Island were dated using zircon LAICPMS method, yielding two weighted mean 206Pb/238U ages of 118.9±3.3 Ma and 119.2±2.2 Ma which are coincident with the beginning of the volcanism of the Qingshan stage in the Jiaolai Basin. There was a largescale rift basin extending in NE direction developed in the offshore areas of Eastern Shandong Province during the Late Mesozoic, inferred by the sedimentary structures. This basin is characterized by alternating uplifts and depressions. Late Mesozoic tectonomagmatic activities and the evolution of regional tectonic stress field were systematically summarized, and it shows a fine comparability between the rift basin and Jiaolai Basin. These two basins may be a whole in the Laiyang stage and were separated by the volcanic arc exposing along the WulianQingdao fault zone and Mouji fault zone in the Qingshan stage. Finally, this offshore prototype basin of the Late Mesozoic was restored based on the above analysis.

Key words: Late Mesozoic, tectonomagmatic activities, rift basin, prototype basin