SOFT-SEDIMENT DEFORMATION STRUCTURES IN THE SEDIMENTS AT LINGSHAN ISLAND

Many types of soft-sediment deformation structures, such as curled bedding, liquefied diapir, load structure, diapired structure, liquefied breccia, ball-pillow structure, water escape structure, micro-faults and large slump body, are found in the Cretaceous sediments at the Lingshan Island. Based on field observation and laboratory analysis, we described the characteristics and distribution pattern of the soft-sediment deformation structures, and discussed the paleo-morphology, driving forces and the deformation mechanism. The study area was suffered from frequent tectonic activities in early Cretaceous influenced by the nearby Wulian-Yantai fault. The deformation structures are most probably caused by earthquakes. The horizontal shear stress analysis for asymmetric load structures and micro-faults are used to determine the existence of paleo-slope and its direction. Our results verified the dominant paleo-slope dipping from SE to NW inferred by Lv Hongbo. Earthquakes induced volcanic eruptions and formed the thick white tuffaceous deposits. The deep fault, which may have extended to the magmatic pocket, provided channels for volcanic eruption.