The Mesozoic-Cenozoic Extensional Tectonics In Western Shandong Province

In light of the previous work, the techniques of structural examination, basin analysis and petrology study have been used to deal with the Mesozoic –Cenozoic extensional tectonics in the west Shandong; determine the time of onset of crustal extension; unravel the structure and its style, change in magnitude, and deformation model of extension; clarify the process of continental extension. And the tectonic driver for extensional event also has been discussed. This work can help to gain a further knowledge of complex tectonic evolution of west Shandong and its adjacent areas in eastern China. Detailed studies revealed that the time of the the beginning of N-S regional extension is at ca. 200 Ma. And Mesozoic extension is characterized by gently to moderately dipping listric faults style and displacement along these faults is transferred from one to the next along N-S strike-slip faults. This structural style displays high-magnitude extension, has overall tectonic geometry of simple shear and forms detachment basins. However, Cenozoic extension is characterized by high-angle normal faults style and some of them bound the present basins. This structural style displays low-magnitude extension, has overall tectonic geometry of pure shear and forms rift basins. Crustal extension activities were partly concurrent with regional magmatism since Mesozoic in west Shandong province. Experienced maximum rotation of Cretaceous sedimentary sequences related to extension is evidence for the most extensive crustal stretching and thinning from 110 to 130 Ma. The Mesozoic extension preceded magmatism by 25 Ma. And compared with magmatism, extensional activities was long-lived and occurred in more widespread area, to the extent that preclude a genetic link between local magmatism and extension. But the observation that pulses of magmation generally coincided with the peak extensional strain rates suggests that the two processes reinforced each other. The integrated studies support the concept that Mesozoic S-N extension activities result from the lateral spread of the early gravitationally unstable thickened crust. But the deviatoric stress caused by the plates motions is the main driver for the Cenozoic extension. And the crustal structure change over time also plays an important role in the tectonic process. The rapid...