Load structures and ball-and-pillow structures on the Lingshan Island, Shandong

The load structures and ball-and-pillow structures on the Lingshan Island, Shandong are examined in the light of outcrop observation, sedimentary petrology and geostatistical analysis. These load structures and ball-and-pillow structures are laterally extensive in the studied sections, and have the features of multiple scales, multiple morphologies and multiple associations. They are interpreted to be originated from the stratigraphic density inversion (bigger in the upper part and smaller in the lower part). In other words, the gravity-induced overlying deposits with greater densities and earthquake-induced liquification penetrated into the underlying strata, resulting in the formation of the load structures and ball-and-pillow structures. The asymmetrical morphology of the load structures strongly support the existence of the Lingshan palaeoslope during the Early Cretaceous. The statistics of the sizes of the load structures and ball-and-pillow structures may be used to deduce those of earthquake magnitudes. The presence of abundant load structures on the Lingshan Island indicates that frequent structural activities, especially the seismic activities may be responsible for the formation of the load structures and ball-and-pillow structures in the study area.