Neogene Paleoseismic Events and the Shanwang Biota's Burial in the Linqu Area, Shandong Province, China

AbstractSeveral paleoseismic events are recorded in the Neogene Linqu Group, exposed in the Linqu area, Shandong Province, China. The events were interpreted on the basis of fieldwork and laboratory analysis, which showed the presence of seismites with plastically deformed soft‐sediment deformation structures in the Shanwang Formation, and of seismic volcanic rocks in the Yaoshan Formation which show brittle deformation. The earthquake‐triggered soft‐sediment deformations in the seismites include load structures, ball‐and‐pillow structures, flame structures, pillow‐like beds, boudinage structures, slump folds, syn‐depositional faults, veins of liquefied sand, and dikes of liquefied sandy lime‐mud. The seismic activity is also reflected in what might be called ‘brittle seismites’; these originated when, under the influence of seismic vibrations, semi‐consolidated conglomerate was shattered. Moreover, volcanic activity is related to intense earthquakes that affected basalts intercalated with sand layers; these successions are known as ‘seismic volcanic rocks’, which are characterized by veins of liquefied sand intruding the basalts. All above traces of paleoseismic activity were left from one single time span of 4 Ma with active seismicity that took place 14–10 Ma. This time span is known as ‘the Linqu Neogene Paleoseismic Active Period’, which is divided into four paleoseismic episodes, which were responses to tectonic extension and basin rifting in this area. It even includes the activity of the Yishu Fault Zone during the Miocene and the Neogene. The ratios of trace elements in the seismites, w(La)/w(Sc) and w (La)/w(Th) are higher than the average value of the upper crust, but w(Th)/w(Sc) is lower; this is geochemical evidence for the basin rifting that resulted in a high sedimentation rate. The intense and frequent paleo‐earthquakes are held responsible for the rapid burial of the Shanwang Biota. Secondary earthquake‐induced processes (e.g. slumping of a lake shore and the strongly increased lacustrine sedimentation rate) contributed to the rapid burial of the biota.