Stratigraphy and Geochronology of Vertebrate Fossil-Bearing Jurassic Strata from Linglongta, Jianchang County, Western Liaoning, Northeastern China

• Published in: Acta geologica Sinica (Beijing) 2012-12, Vol.86 (6), p.1326-1339
• Main Authors: Nan, PENG, Yongqing, LIU, Hongwei, KUANG, Xiaojun, JIANG, Huan, XU
• Format: Article
• Language: English
• Subjects: Dinosaurs; Fossils; Freshwater; geochronology; Jurassic; northeastern China; Stratigraphy; vertebrates; 中国东北地区; 侏罗系地层; 吐哈盆地; 地层学; 地质年代学; 建昌县; 脊椎动物化石; 辽宁西部地区
• ISSN: 1000-9515; 1755-6724
• DOI: 10.1111/1755-6724.12003

Northeastern China contains widely distributed Jurassic terrestrial strata that have yielded many spectacular mammal and pterosaur fossils, in addition to feathered dinosaur fossils and more recent discoveries from Jianchang, particularly from western Liaoning. However, the fossil-bearing stratigraphic succession, regional correlation, and age estimates of the fossils found in Jianchang County and nearby areas have been contentious. Here, we report on the vertebrate fossil-bearing Jurassic stratigraphy from Linglongta, Jianchang County, western Liaoning, including a SHRIMP U-Pb zircon date unambiguously associated with the fossil horizons. The primary goal was to determine the vertebrate fossil-bearing succession. A further aim was to provide age estimations for the fossil-bearing horizon as well as the earliest appearance of feathered dinosaurs, the eutherian-placental clade, and transitional pterosaurs. Field investigations showed that the vertebrate fossil-bearing stratigraphic succession in Jianchang County mainly consists of basal andesites overlain by rhythmic tufts and tuffaceous lacustrine sediments, with the upper intermediate or acidic lavas interbedded with laminated more or less tuffaceous lacustrine deposits. This sequence correlates well with the Middle Jurassic Lanqifl＇iaojishan Formation in northeastern China. Detailed and accurate field observations showed that the well- preserved vertebrate fossils were buried in either the middle or the upper fine-grained laminated lacustrine deposits. Previous and current SHRIMP U-Pb zircon dates provide an age estimation of 161- 159 Myr for the fossil-bearing horizon and vertebrates. This indicates that the earliest appearance of feathered dinosaurs here was more than 159 Myr ago and unquestionably older than Archaeopteryx from Germany, making these the earliest known feathered dinosaurs in the world. Furthermore, the eutherian-placental clade and the known transitional pterosaurs first emerged no later than 161 Myr. The vertebrate assemblage unearthed recently from Linglongta and neighboring areas in Jianchang County belongs to the Daohugou Biota. In addition to feathered dinosaurs, this biota was characterized by mammals, primitive pterosaurs, insects, and plants and was present in Inner Mongolia, western Liaoning, and northern Hebei in northeastern China during the Middle-Late Jurassic.