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

Abstract

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.

Demise of the Middle Jurassic carbonate platform: Responses to sea‐level fall in the Qiangtang Basin, Eastern Tethys

“…The precession is the longitude of the vernal node relative to the perihelion. The eccentricity and precession which influence the solar energy distribution together and further dominate palaeoclimate changes on the Earth (Milankovitch, 1941; Xia et al, 2020). Sedimentological evidence indicates cyclic changes in eustasic fluctuations are resulted from Milankovitch forcing.…”

“…The basic principle of cyclostratigraphic analysis is to detect astronomical orbital signals in the sedimentary record (Ma et al, 2017; Meyers & Sageman, 2007; Wu et al, 2014; Wu, Zhang, Jiang, & Huang, 2009; Xia et al, 2020). As mentioned above, Th controlled the GR intensity which was reflected on spectral GR logs in terms of amount that contributed to the radioactivity.…”

“…The calculation of sedimentation rate was based on the theory of Milankovitch Cycle with the quantitative method resulted from orbital signals (Milankovitch, 1941). The Milankovitch Cycle did not provides insights into the genesis of global climatic changes but also established high‐resolution chronostratigraphic framework and sedimentation rate changes with time (Milankovitch, 1941; Xia et al, 2020). There was a relatively stable relationship among various order Milankovitch Cycles.…”

Correspondences between high‐frequency sequences and the Milankovitch Cycles of Dongying Formation in Liaoxi Uplift, Bohai Bay Basin, North‐east China

“…The present Bohai Bay Basin is located among northern Yanshan Uplift, eastern Liaodong Uplift, and Luxi Uplift (Hsiao et al, 2004;Hsiao, Graham, & Tilander, 2010). In addition, its coverage arrives at about 200,000 km 2 with north-eastward trend (Xia et al, 2020). Liaodong Bay, as a sub-tectonic unit, is situated in northeastern Bohai Bay Basin, where there are several depressions and uplifts with NE or NNE strike.…”

“…The stratum in the Palaeogene develops Kongdian Formation (Ek), Shahejie Formation (Es), and Dongying Formation (Ed) from bottom to top, respectively (Peng et al, 2018;Xia et al, 2020). During the depositional process of Dongying Formation, the whole Bohai Bay Basin was in the late syn-rift stage of tectonic evolution.…”