湖南株洲天元区晚白垩世恐龙化石层时代及沉积环境

The Age and Sedimentary Environment of Late Cretaceous Dinosaur Fossils Layer in the Tianyuan Area of Zhuzhou City,Hunan Province

在湖南省株洲市天元区的戴家坪组发现了新的恐龙化石产出点.然而,关于赋存该恐龙化石地层的时代存在一定的争议.基于碎屑锆石U-Pb物源分析和孢粉数据对恐龙化石点进行了年代学和沉积学研究.从恐龙化石点的关键层位采集了孢粉和碎屑锆石样品,经过室内样品处理和数据分析,孢粉化石鉴定获得15属18种;根据具有时代意义的孢粉特征分子可以得到其共存延限带Aquilapollenites coriaceus-Betpakdalina pentaoculoides,把戴家坪组时代厘定为晚白垩世坎潘期(Campanian)-马斯特里赫特期(Maastrichtian).碎屑锆石U-Pb年龄峰值主要为6个阶段:200~320 Ma、390~450 Ma、740~950 Ma、1020~1100 Ma、1640~2000 Ma和2440~2600 Ma,指示戴家坪组粗粒的沉积物主要来源于盆地SE侧的近源幕阜罗霄山,而细粒的沉积碎屑可能部分来自NW侧的黄陵等地区.

New dinosaur fossils were found from the Late Cretaceous Daijiaping Formation in the Zhuzhou Basin recently.However,the age of the dinosaur fossil formation remains controvercial.Based on the analysis of palynological types and detrital zircon U-Pb data,the age and geological background of the dinosaur fossils from the Tianyuan area,Zhuzhou City,Hunan Province,are reported here.18 species of 15 genera of the main palynomorphs could obtain a concurrent-range Aquilapollenites coriaceus-Betpakdalina pentaoculoides zone.Through comparison of the typical palynomorphs from the Daijiaping Formation,the age of the formation can be accurately defined as Campanian-Maastrichtian.A series of detrital zircon samples are collected and analyzed from the key layers of dinosaur fossils,and the detrital zircon U-Pb age peaks can be divided into six stages:200-320 Ma,390-450 Ma,740-950 Ma,1020-1100 Ma,1640-2000 Ma and 2440-2600 Ma.On the basis of detrital zircon and paleogeography analysis,coarse sediments of the Daijiaping Formation were mainly from the southeastern surrounding mountains,whereas parts of the fine-grained debris came from the northwestern Huangling area.