Journal of Asian Earth Sciences 110 (2015) 101–122 Contents lists available at ScienceDirect Journal of Asian Earth Sciences journal homepage: www.elsevier.com/lo cate/jseaes Soft-sediment deformation structures in the Cretaceous Zhucheng depression, Shandong Province, East China; their character, deformation timing and tectonic implications Bizhu He a,⇑, Xiufu Qiao a, Yingli Zhang b, Hongshui Tian c, Zhihui Cai a, Shuqing Chen d, Yanxia Zhang d a State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China b Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China c Shandong Construction University, Jinan, Shandong 250014, China d Dinosaur National Geopark, Zhucheng, Shandong 262200, China a r t i c l e i n f o a b s t r a c t Article history: Various plastic and brittle soft-sediment deformation structures (SSDS) are recognized in Cretaceous sed- Received 2 April 2013 imentary rocks of the Zhucheng depression, East China record important information on the different Received in revised form 25 November 2014 sediment characteristics, depositional settings and tectonic movements involved in their formation. Accepted 15 December 2014 The recognized SSDS include undulate folds, mound-and-sag structures, diapirs, convolute features and a Available online xxxx seismically induced unconformity. The Lower Cretaceous sedimentary rocks are fine grained, lacustrine deposits, whereas those of the Upper Cretaceous are coarse-grained sandstones and conglomerates Keywords: formed in an alluvial fan or flood-plain setting. These SSDS with coarse-grained rocks are characterized by Soft-sediment deformation structures fault grading, load cast structures, ball and pillow structures and plunged sediment mixture struc- tures. Deformed time Seismites We propose that the SSDS was triggered by paleo-earthquakes. Alternating deformed and unde- formed Dinosaur fossils layers suggest frequent and repeated seismic activity. Stratigraphic correlations, the evaluation of Cretaceous magmatic events and the youngest detrital zircon ages indicate that the deformational events occurred Zhucheng depression mainly in the Early Cretaceous between 118 Ma to 105 Ma, and in the Late Cretaceous at approximately East China 100 Ma. Numerous giant hadrosaurid fossil skeletons have been found in the Upper Cretaceous Wangshi Group, and unusual and abundant dinosaur tracks are preserved in the Lower Cretaceous Yangzhuang Formation of the Laiyang Group. The zones of widespread SSDS closely underlie and overlie the dinosaur fossil-bearing strata. The depositional setting changed in response to multiple paleoseismic events and regional tectonic movements. After many paleoearthquakes and environmental changes in the Early Cre- taceous, many dinosaurs appear to have migrated, based on the presence of many tracks with a similar orientation in lacustrine sedimentary rocks. In the Late Cretaceous strata, large-scale dinosaur fossil lay- ers are associated with paleo-earthquake records, suggesting that the dinosaur fossil burial may be asso- ciated with large-scale debris flows triggered by frequent earthquakes. Based on regional tectonic setting, the distribution of SSDS and the predicted paleo-earthquake magnitudes, the seismogenic fault may have been the Wulian Fault. 2014 Elsevier Ltd. All rights reserved. 1. Introduction determine the exact cause of any given feature. Many things, such as the nature of the driving force, the sediment rheology, deforma- SSDS are features produced when deformation occurs in uncon- tion mechanism and timing of deformation relative to sedimenta- solidated sediment, typically close to the surface, during or shortly tion, can affect the final morphology and deformation style of after deposition and before significant diagenesis (Owen, 1987; soft-sediment structures (Obermeier, 1996; Moretti et al., 1999; Qiao et al., 2006; Owen et al., 2011). Because many processes can Qiao et al., 2006; Owen et al., 2011). Driving forces include gravity produce SSDS, such as tectonic activity, glacier-related deposition, acting on slopes, unequal loading, reverse density gradients, shear gravity-driven mass-movements, sediment mobilization in over- forces, and biological and chemical agents (Owen et al., 2011). pressured and collapsing environments, it can be difficult to Most SSDS are produced by inputs of kinetic energy from outside the deposystem (Leeder, 1987). Seismic activity with a magnitude of 5 or greater, related to episodic fault motion, is ⇑ Corresponding author. E-mail addresses: [email protected], [email protected] (B. He). considered the most common trigger, leading to liquefaction of http://dx.doi.org/10.1016/j.jseaes.2014.12.005 1367-9120/ 2014 Elsevier Ltd. All rights reserved. Please cite this article in press as: He, B., et al. Soft-sediment deformation structures in the Cretaceous Zhucheng depression, Shandong Province, East China; their character, deformation timing and tectonic implications. Journal of Asian Earth Sciences (2015), http://dx.doi.org/10.1016/j.jseaes.2014.12.005 Journal of Asian Earth Sciences 110 (2015) 101–122 unconsolidated sediments (Allen and Banks, 1972; Allen, 1986; variety of SSDS sedimentary rocks containing the largest collection Galli, 2000; Santos et al., 2012). Seismites (proposed by Seilacher of dinosaur fossils in Asia (Young, 1958). So far, approximately (1969)) is the term applied to SSDS produced by earthquakes. 8000 dinosaur fossils, both as individual animals and bone masses, The most important criteria used to identify seismites include: have been recovered from several quarries in the Upper Cretaceous (1) the deformation occurs in laterally continuous, recurring hori- Wangshi Group southwest of Zhucheng (Fig. 1A and B). In addition, zons, separated by layers of undeformed sediment that can be tem- many footprints of different dinosaur species are preserved in sed- porally or stratigraphically constrained; (2) the deformation imentary rocks of the Lower Cretaceous Laiyang Group. involves alluvial, lacustrine, and marine sediments; (3) deformed Major dinosaur fossils include femurs, humeri, ribs, tibiae and and undeformed beds have similar lithologies and facies features; scapulae of hadrosaurs, horned dinosaurs, tyrannosaurus and other (4) the deformation can be related to a seismically or tectonically species (Young, 1958; Hu, 1973; Li, 1998; Zhao et al., 2007; Hone active area when the SSDS were formed; and (5) the deformation et al., 2011). The longest single bone is 4.84 m, the shortest is about shows systematic increases in frequency or intensity toward a 10 cm, and many small skeletal fragments are also present. These likely epicentral area (Seilacher, 1984; Qiao et al., 1994; fossils were buried in debris flows, or flood plain and braided chan- Obermeier, 1996; Ettensohn et al., 2002; Montenat et al., 2007; nel deposits, with the debris flow deposits being the most impor- Qiao and Li, 2008, 2009; Van Loon, 2009). Recognition of seismites tant (Liu et al., 2003; The Fourth Institute of Geological and generally involves a combination of sedimentary facies analysis, Mineral Resources Reconnaissance of Shandong Province, 2003; identification of potential triggers, and recognition of all of the cri- Liu et al., 2010, 2011). Abundant, well-preserved footprints of teria listed above (Owen et al., 2011). dinosaurs are present in the Huanglonggou quarry south of Zhuch- Various SSDS have recently been identified in the Zhucheng eng, where ca. 3000 tracks belonging to at least 6 species, including faulted depression. The initial recognition of SSDS in the Upper ornithopod, theropod, sauropoda and others, have been identified Cretaceous strata was reported briefly after the initial discovery in an area of 2600 m2(Li and Zhang, 2000, 2001; Xing et al., (He et al., 2011). The earlier paper in Chinese reported a large 2010; Li et al., 2011). Small footprints of ornithopods are generally B (A) (B) (D) D E (C) (E) Fig. 1. Dinosaur fossils and footprints in Cretaceous strata of the Kugou and Huanglonggou quarries, Zhucheng depression, Shandong Province, China. (A) Bone bed in the middle part of Kugou quarry (view is about 1/8 the length of the whole quarry); (B) detailed view of fossils in the bone bed (hammer is 23 cm long, camera pointing south); (C) view of a dinosaur track in the Lower Cretaceous Yangzhuang Formation of the Laiyang Group (letters indicate the locations of the next two photographs; (D) dinosaur footprints in ripple marked sandstone; and (E) close-up of the dinosaur track (scale is 10 cm long). Photographs (A) and (C) are courtesy of the Zhucheng Dinosaur National Geopark. Please cite this article in press as: He, B., et al. Soft-sediment deformation structures in the Cretaceous Zhucheng depression, Shandong Province, East China; their character, deformation timing and tectonic implications. Journal of Asian Earth Sciences (2015), http://dx.doi.org/10.1016/j.jseaes.2014.12.005 B. He et al. / Journal of Asian Earth Sciences xxx (2015) xxx–xxx 3 5–10 cm long, whereas large footprints of theropods can be up to relationship between paleo-earthquake events and dinosaur fossil 40 cm long (Fig. 1C–E). Most footprints with similar motion orien- burial in this environment. tations are preserved in argillaceous siltstone and fine-grained sandstone of offshore to shallow lacustrine environments with par- allel bedding, small-scale cross-bedding and ripple marks (Liu 2. Geological setting et