Shaanxi is the birthplace of chinese dinosaur footprint fossil research, and in 1929, academicians Yang Zhongjian and De Rijin first reported the fossil dinosaur footprints found in Shenmu, Shaanxi, which is the earliest report on dinosaur footprints in China. In recent years, there have been reports of dinosaur footprints in Tongchuan, Shenmu, Shangluo, Zizhou and Zhongji.
Figure 1, Shaanxi dinosaur footprint discovery point (Wang Baopeng, 2020)
First, the discovery of dinosaur footprints
In 1929, Mr. Yang Zhongjian of Northwest University and French paleontologist De Rijin found an iguanodon footprint in the Jurassic strata of Dongshan Cliff in Shenmu County, Shaanxi Province, with a total length of 30 cm and a width of 33 cm, and the three toes of the footprint were wider, of which the middle toe was 19 cm long and 9 cm wide. This was reported in the same year, and it was the first report of dinosaur footprints found in China. But it wasn't until 1958 that german paleontologist Kuhn officially studied the footprint and named it the Young's China Footprint.
Figure 2, Heilongjiang Yichun Dinosaur National Geopark, Yang Zhongjian (left) and Sun Ge (right)
In 1966, Academician Yang Zhongjian of Northwest University reported that Cheng Shusen of the Northwest Coalfield Geology Bureau collected two fossil footprints from the open pit northeast bangpo of the Qianhe River in the Jiaoping Coal Mine in Tongchuan, Shaanxi, and the footprints were named tongchuan shaanxi footprints.
Figure 3, Dinosaur footprints
In 1981, Professor Xue Xiangxu of Northwest University and others found lizard dinosaur fossils in the red strata of Luonan Basin, and Xue Xiangxu et al. introduced that 4 dinosaur footprints were found on the argillary siltstone level in Shangxian County, Shaanxi Province, of which 2 footprint specimens were preserved in the Erlongshan Reservoir Management Office of Shangluo City.
Figure 4, Professor Xue Xiangxu
Later, in 2017, a number of dinosaur footprints were found in the Cretaceous strata of Gonggegou in Zhongji Town, Shenmu County, Shaanxi Province, including 3 dinosaur footprints and 2 small tetrapod footprints.
Second, the characteristics of dinosaur footprints
(1) Dinosaur footprints in Kamiki City were discovered and preserved after the 20th century, and there have been no new discoveries or research progress for a long time. In 2009, dinosaur footprints found in Qiujinggou Village, Railing Fort Town, about 25 km southeast of Shenmu City, were located on top of the brownish yellow medium coarse sandstone layer above the lower flint strip of the Lower Jurassic Fuxian Formation (J1f), and the dinosaur footprints were mostly three-toed theropods and stegosaurus.
Figure 5, Shenmu Zhongji Town, E: Three-toed Theropod Footprint, F-Two-Toed Theropod Footprint (Tang Yongzhong, 2018)
The fossils of dinosaur footprints in Zhongji Town, Shenmu City, are distributed on the east bank of gonggegou reservoir in Baodaoshili Village, and in the 30 km2 red Danxia landscape, 3 dinosaur footprints and 2 tetrapod footprints have been found to be clearly preserved in their original state. Dinosaur footprints were found in the coarse-grained sandstone layers of the upper middle Jurassic Yan'an Formation (J2y), and most of the dinosaur footprints were left by the three-toed theropod stegosaurus and ornithopod iguanodon.
Figure 6, Dinosaur footprints
(2) In the Anse area, 4 dinosaur footprints were found in a set of sandstone formations at the top of the Gira Formation, of which 3 were three-toed dinosaur footprints; and 3 suspected dinosaur footprints were observed. According to the comparison of footprint morphology and footprint characteristics, it is inferred that the footprint tracers of three-toed dinosaurs are large carnivorous theropod dinosaurs, and the tracers of other footprints are difficult to confirm.
Figure 7, Dinosaur Footprints in the Ansai Area (Li Xinwei, 2021)
(3) The location of the Jingbian Longzhou dinosaur footprint is located in Baituping Village, Longzhou Town, Jingbian County. Dinosaur footprints are endowed with lower Cretaceous Luohe Formation, and the lithology of the footprint preservation level is purple-red thin layer of medium-grain feldspar quartz sandstone and argillary siltstone, and the development of small and medium-sized oblique stratigraphy and staggered stratigraphy is desert facies desert lake sedimentary subphase - dune subphase sedimentary sediments. Dinosaur footprints were formed in a dune environment on the shores of shallow desert lakes.
Figure 8, Dinosaur footprints in Jingbian Longzhou
Third, the formation environment of dinosaur footprint fossils
The discovery of a large number of dinosaur footprints in Shaanxi shows that Shaanxi was once a beautiful home for dinosaur life. Dinosaur footprint fossils are mainly distributed in the Upper Jurassic Anding Formation, the Lower Cretaceous Luohe Formation, especially in the lower Cretaceous Luohe Formation in the central layer of the purple-red thin-medium grain quartz sandstone.
Figure 9, Dinosaur Footprints
The Anding Formation is a set of coarse-fine clastic rock spiral sediments dominated by brown-red, fuchsia and purple variegated hues, which can be divided into three secondary spirals.
Figure 10, purple-red sandstone
During the sedimentary period of the Luohe Formation, the basin has quasi-plain properties, the river is wide, the purple red, brown red, brick red thick layer sandstone is deposited, and there is a gray-white Kaolin stony fine sandstone, the sandstone body is developed large-giant trough-like staggered layer, staggered stratification, containing conglomerate sandstone, medium grain feldspar sandstone sandwiched with a small amount of siltstone sedimentary combination, belongs to the river and alluvial fan sedimentation.
Figure 11, Luohe Formation sandstone
Through the comparison with neighboring areas, the dinosaur footprint fossils in Shenmu City are distributed from the early and middle Jurassic to the early Cretaceous, and the mesozoic plant fossil combinations in the northern ordos basin are mainly ginkgo biloba, followed by true ferns, indicating that the basin was rich in vegetation and warm and humid at that time, which was suitable for dinosaur life, and the paleoclimate belonged to a warm and humid climate conducive to the rapid growth of plants, accompanied by a dry temperate-subtropical climate.
Figure 12, Sandstone of The Chicken in Shaanxi Province
There are small layers of volcanic ash (basalt lava chips in the sandstone) in the sedimentation of lakes in the Lower Cretaceous LuoHe Formation, and the climate is relatively hot and dry. Spore powder is dominated by Bennei cycads, cycads, ginkgo biloba, pine cypress, etc., followed by conical leaf fern, cypress spores and so on. The paleontological landscape generally reflects the warm paleoclimate environment dominated by drought.
Figure 13, Cycads
In summary, the formation era of dinosaur footprint fossils is of great significance to the study of dinosaur life, evolution and extinction, and has important isochronism. At present, it is mainly determined by the comparison of stratigraphic rock combinations, the comparison of dinosaur footprint fossil types, and the ancient plant fossils and pollen.