New chronostratigraphic constraints on the Yixian Formation with implications for the Jehol Biota
New chronostratigraphic constraints on the Yixian Formation with implications for the Jehol Biota
复制标题
DOI：
10.1016/j.palaeo.2017.09.026
复制
发表时间：
2017-12-01
影响因子：
3
通讯作者：
Jourdan, Fred
中科院分区：
文献类型：
--
作者：
Chang, Su-Chin;Gao, Ke-Qin;Jourdan, Fred
白垩纪热河生物群的化石保存完好，多样性非凡。在中亚和东亚地区的大北沟组、义县组和九佛塘组（及相关地层）中发现了陆生化石，包括植物、昆虫、恐龙、鸟类、哺乳动物和淡水无脊椎动物。在内蒙古、河北、辽宁西部的义县组发现了重要的标本。依县组从下向上划分为陆家屯组、下熔岩组、建山沟组、上熔岩组、大王章子组和井冈山组。然而，以往报道的通过各种方法获得的年龄数据，并应用于义县组不同单元，与义县组普遍接受的地层解释并不一致。本文总结了义县组以前的年龄数据，并使用相同标准的新年龄解释（即FCs = 28.294）重新校准了先前报道的40Ar/39Ar年龄。对陆家屯单元的两个玄武岩样品进行了高精度的40Ar/39Ar年龄测定，分别为125.8 +/- 1.0 Ma和126.0 +/- 0.8 Ma。新时代资料和重新标定的已发表资料表明，陆家屯单元与建山沟单元同时沉积。因此，广泛接受的义县组地层柱需要重新解释。本研究为重建富化石的义县沉积环境提供了重要线索，并为约束早期哺乳动物、原始鸟类和有羽恐龙的进化速率提供了依据。
The fossils of the Cretaceous Jehol Biota exhibit excellent preservation and extraordinary diversity. Terrestrial fossils, including plants, insects, dinosaurs, birds, mammals and freshwater invertebrates have been discovered from the Dabeigou, Yixian and Jiufotang Formations (and correlative strata) in Central and East Asia. Significant specimens have been recovered from the Yixian Formation of Inner Mongolia, Hebei Province, western Liaoning Province of NE China. The Yixian Formation is generally divided (from bottom to top) into the Lujiatun Unit, Lower Lava Unit, Jianshangou Unit, Upper Lava Unit, Dawangzhangzi Unit and Jingangshan Unit. However, previously reported age data obtained through a range of methods and applied to different units of the Yixian Formation do not consistently integrate with the Yixian's commonly accepted stratigraphic interpretation. Here we summarize previous age data for the Yixian Formation and recalibrate previously reported 40Ar/39Ar ages by using new age interpretations for the same standard (i.e. FCs = 28.294). We also present new high-precision 40Ar/39Ar ages of 125.8 +/- 1.0 Ma and 126.0 +/- 0.8 Ma for two basaltic samples from the Lujiatun Unit, a unit of previously uncertain age. The new age data and re-calibrated published data indicate that the Lujiatun Unit was deposited contemporaneously with the Jianshangou Unit. The widely accepted stratigraphic column for the Yixian Formation therefore requires reinterpretation. Our study provides significant clues for reconstructing sedimentary environment for the fossil-rich Yixian deposits and allows to constrain evolutionary rates for early mammals, primitive birds and feathered dinosaurs.