Detrital zircn age for the fossil-bearing Xingezhuang Formation in the Jiao-Lai basin, East Shandong, China

Abstract

The late Mesozoic terrestrial Jiao-Lai basin, located in East Shandong Province, China, is a typical pull-apart basin controlled by the strike-slip Tan-Lu fault system. Tectonically, it lies to the east of the Tan-Lu fault, and intervened between the Jiaobei terrane in the north and the Su-Lu orogen in the south. Extensive dinosaur and dinosaur egg fossils have been discovered from the Xingezhuang Formation of the Wangshi Group in this basin (Hu et al., 2001; Zhao et al., 2007, 2011; Liu et al., 2010; Wang et al., 2010; Xu et al., 2010a, 2010b). Determining the age of the fossil-bearing Xingezhuang Formation is critical for evaluating the evolutionary significance of the dinosaurs and for understanding the tectonic background of the Jiao-Lai basin. However, reliable age determinations for the Xingezhuang Formation and even the whole Wangshi Group are rare (e.g. Yan et al., 2003, 2005; Meng et al., 2006). We are analyzing detrital zircons from two tuffaceous sandstones collected from the fossil beds of the Xingezhuang Formation in the Jiao-Lai basin. Our work will provide the maximum depositional age for the Xingezhuang Formation and will allow reconstructing the tectonic history of this region. Furthermore, our radioisotopic age for this fossil-bearing formation will be a first step towards putting this stratum into a global framework of biological evolution.