Magnetostratigraphy Of The North Core Of The China Cretaceous Continental Scientific Drilling Borehole In The Songliao Basin

In geological history, the Cretaceous is a very special period, during which the global biosphere, paleogeography and paleoclimate changed dramatically. Therefore, the Cretaceous period of geologic history is a typical example of the Earth system.The marine Cretaceous has been intensively studied. However, systematic research for Cretaceous continental deposits remains scarce. The Songliao Basin in northeastern China which is one of the largest nonmarine petroliferous basins in the world, contains a complete Cretaceous sequence of terrestrial sediments. However, correlation of the Cretaceous terrestrial sequences of the Songliao Basin to marine strata remains ambiguous due to the absence of a reliable chronology.The Cretaceous Continental Scientific Drilling borehole in the Songliao Basin (CCSD-SK-I) offers a unique opportunity for probing into the nature of the terrestrial Cretaceous world. The CCSD-SK-I sedimentary sequence consists of two borehole cores: the north core being upper; and the south core, lower. The strata of the north core comprise the Nenjiang, Sifangtai and Mingshui Formations; and of the south core, the Quantou, Qingshankou, Yaojia and Nenjiang Formations.In this dissertation, I carried out high-resolution magnetostratigraphic investigation on the north core. Correlation of the recognized magnetozone to the geomagnetic polarity timescale was achieved by combining magnetostratigraphic and SIMS U-Pb zircon geochronologic data of the south core. Our correlation suggests that the north core sedimentary sequence spans from the upper chron C34n to chron C29r. The age of the north core sedimentary sequence from the lower Nenjiang Formation to the Mingshui Formation in the Songliao Basin can thus be constrained to an interval from the early Campanian to the Maastrichtian ages. I futher get ages between the lithostratigraphic formations/members in the CCSD-SK-â… n: K/T boundary is located in the upper part of member 2 of the Mingshui Formation, that is, within magnetic polarity with magnetozone R1 (C29r); the age of boundary between Nenjiang (K_2n)and Sifangtai formation (K_2s) is 79.075 Ma; the age of boundary between the member 2 of Nenjiang formation and the member 3 of Nenjiang formation (K₂n₂-K₂n₃) is 82.172 Ma; the age of boundary between the member 3 of Nenjiang formation and the member 4 of Nenjiang formation (K₂n₃-K₂n₄) is 81.591 Ma; the age of boundary between the member 4 of Nenjiang formation and the member 5 of Nenjiang formation (K₂n₄-K₂n₅) is 80.478 Ma; the age of boundary between Sifangtai and Mingshui formation (K_2s-K_2m) is 72.155 Ma; the age of the boundary between the member 1 and the member 2 of Mingshui formation (K_2m2-K_2m1) is 70.132Ma. The CCSD-SK-I(north) records the sedimentary succession from the early Campanian to the early Danian, the boundary between the Cretaceous/Paleogene is in the upper part of member 2 of Mingshui Formation.