A new early Cretaceous amber locality from Inner Mongolia, China: taphonomy and age

Abstract

The Hailar Basin is located in the northeastern part of Inner Mongolia autonomous region and yields abundant Early Cretaceous coal resources. The main coal-bearing strata are from the Damoguaihe and Yimin formations. We here report a new amber site from the coal layers of the Yimin Formation in two coal mines in the Hailar Basin. The amber is small and fragmented, and some amber pieces were directly preserved in the leaves, retaining the shape. Because of the poor preservation, the details of the plant veins cannot be seen clearly, and the preliminary identification indicated that the plants belong to conifers. No inclusions were found so far. This is the first report of in-situ preserved amber in China. To establish robust age for this significant site, two interbedded tuffaceous samples were collected from the coal beds in the Zhalainuoer Coalmine and Yimin coalfield. Zircons from these samples were separated for LA-ICP-MS U-Pb dating. Our age result will provide important constraints on the biogeographic history of the field area and the geological age of the Yimin Formation in the Hailar Basin. Furthermore, this study will improve our understanding of the palynology records and Cretaceous world in general.