The Ostracod Biostratigraphy And The K/Pg Boundary Discussion In Lk1 Core, Jiaolai Basin

Jiaolai basin is a typical Mesozoic continental fault basin, its strata developed well. The LK1 core is located at the north of the Jiao Zhou, a city in the Jiaolai basin. The section is composed of the Wangshi group and overlying Quaternary deposit.Most of depositions in Shandong province, whether east or west area, lack of the Cretaceous-Plaeogene boundary strata. The exception is Jiaozhou area. The Jiaozhou formation, which belongs to the Wangshi group in Jiaozhou area, pertains late Cretaceous to early Paleocene epoch. Although Jiaozhou formation also lacks part of strata, the section of Cretaceous-Plaeogene boundary strata is unbroken developed. So it complete records the K/Pg event and event’s influence, boundary strata provides great possibilities for the K/Pg boundary study in ShanDong.Based on the lithologic characteristics and previous study, we can know that all the section of core belong to the Wangshi group, and the group in LK1 core is composed of the Hongtuya fromation and the Jiaozhou fromation. The bottom of Hongtuya fromation and the top of Jiaozhou fromation both not emerge. The Jiaozhou fromation can be subdivided into Jiao One member, Jiao Two member, Jiao Three member and Jiao Four member.Totally 28 species of 16 genera have been identified through detailed study of ostracod fossils in the Jiaozhou formation. Through the study of ostracod biostraigraphic, we establish 3 ostracod assemblage zones : 1) Cypridea recta—Eucypris triangularis—Eucypris cuneata assemblage zone;2) Candoniella suzini—Timiriasevia minuscula—Candoniella candida assemblage zone;3) Candoniella candida assemblage zone. The distribution of the ostracod fossils shows that ostracod assemblage of assemblage zone 2 is assigned to the transition biota from latest Maastrichtian to the earliest Paleocene. The last disappearance of Gobiella prima possibly marks the end of the Cretaceous.Except the microfossils, There is a large number of microtektites founded in LK1 core. According to topographic characteristics and major element composition analyze, our conclusion is that microtektites of LK1 core are resultant from the K/T boundary yellow microtektites in Haiti. Their parent materials are similar.The section of LK1 core do exist the K/Pg boundary. The position of boundary should be in 523.35m- 517.94 m, which belongs to greyish-green clastic sediments of fluvial facies at Jiao Two member. The first appearance of microtektite marks the K/Pg boundary.