The Study Of Stratigraphic Correlation Of Yixian Formation In Beipiao And Yixian In Western Liaoning

Yixian Formation of early Cretaceous is the richest formation that outputs fossils of dinosaurs, birds, angiosperms and other animals and plants in China, even in the world. It mainly located in Jin-Yang Basin and Fuxin-Yixian Basin. It has some differences between the formation in these two Basins:In Fuxin basin, the formation is mostly developed, whose volcanic cycles are well distinct and stratums extended steadily. People there usually regard Mashenmiao-Songbahu section in Yixian basin as a standard; while, in Jin-Yang basin, Yixian Formation is developed well, but it is generally thin except in Jianshagou. Most of the jehol fossils were found in Jianshangou, especially the scarce fossils of birds and weathered dinosaurs.A lot of works about the difference of stratigraphic sequence correlation of Yixian Formation between Jin-yang basin and Fuxin-Yixian basin have been done. However, the formation samples they chose for analysis and research were from different stratums. They do the same work depended on many different gists that these experts got totally different conclusions. In 1999, Pan Huazhang and Zhu Xianggen found The Layer (analyzed in this paper) in Jin-Yang basin for the first time. In 2003, Jiang Baoyu found The Layer in another section in Beipiao. In 2007, Gong Enpu et al. found The Layer for the first time in Dakangpu bed in Wangjiagou Yixian. Pan Huazhang, Zhuxianggen and Gong Enpu found the same layer in Jin-Yang basin and Fuxin-Yixian basin. The Layer gets to be the key-reference and made it possible to make conclusions on stratigraphic sequence correlation of Yixian Formation based on one single standard.More than 5 month fieldwork and 10 month office work have done for this paper, specifically includes:measured 3 piece of sections, confirmed 5 pieces of sections, collected more than 300 pieces of rock samples, make 10 pieces of rock slices, and read about 300 pieces of papers.Five main points are concluded in this thesis:(1) The Layer occurs in both Jin-Yang basin and Yixian basin. (2) Compared with other stratums, The Layer is lack of volcanic material, which means volcanism was weak when The Layer formed. (3) Jianshangou bed in Beipiao and Dakangpu bed in Yixian were formed almost at the same time. (4) According to the comparison of experts’ conclusions for the two places, it is clear that fossil assemblage is reliable to be used in stratum correlation. The most direct gist to be used in correlation is the same stratum, which is more reliable. For now, besides The Layer with tubular scrap analyzed in this paper, pillow lava and quenched rocks discovered in both Jin-Yang basin and Fuxin-Yixian basin by Zhang Lidong in 2004 are also belongs to this kind of stratum. (5) Regarding the appearance of The Layer in the both basins, Jin-Yang basin and Fuxin-Yixian basin may be connected instead of separated during their formation.