Correspondences among lacustrine fluctuations, climate changes and the Milankovitch cycles in the Paleogene through tracking onlap points and correlating palaeontology in Liaozhong Depression, Bohai Bay Basin, NE China

The solar radiation or insolation at a specific locality on the Earth's surface is determined by the distance of this point from the sun and by the angle with which the radiation hits the earth's surface. The theory that variations in the earth's orbit determine the amount of radiation and therefore the climate which is the Milankovitch Cycle. In non‐marine lacustrine rift basin, the changes of climate can be recorded by the palaeontology, and it also plays an important role in controlling lacustrine fluctuations. The lacustrine fluctuations are indicated by coastal onlap, which is the landward or lake‐ward onlap of non‐marine coastal deposits. In this paper, based on borehole data, wireline logs, seismic datasets, biostratigraphic data and palaeontology, the lacustrine fluctuation curve can be reconstructed from the onlap of lacustrine deposits in non‐marine sequences. The durations and magnitudes of these changes can be used to construct charts showing cycles of the relative rising and falling of lake level. In addition, the changes of lake level can also be reflected by the palaeontology such as pollen. The living conditions and distributions of pollen can be a good indicator for climate changes and lacustrine fluctuations in an a non‐marine setting. The calculation of the Milankovitch Cycle can be determined by the GR log in the study area which keeps a record of cycle changes. All climatic changes and lacustrine fluctuations are mainly resulted from the Milankovitch Cycles, and therefore, through the reconstruction of lacustrine fluctuations, climate changes and the Milankovitch Cycle, the correspondences among them can be clearly addressed. All the results can contribute a lot in theory research in the study area and lead to a new focus in practical hydrocarbon exploration and exploitation.