Magnetostratigraphy and its paleoclimatic significance of the PL02 borehole in the Yinchuan Basin

• Published in: Journal of Asian earth sciences Vol. 114; pp. 258 - 265
• Main Authors: Wang, Junping, Shen, Miaomiao, Hu, Jianmin, Wei, Mingjian, Zhao, Xiaohong, Liu, Shaochang, Li, Xiaolei, Li, Xinling
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.12.2015
• Subjects: Frequency-dependent susceptibility; Magnetostratigraphy; Palaeoenvironment; Palaeomagnetic; Frequency-dependent susceptibility; Palaeomagnetic; Palaeoenvironment; Magnetostratigraphy
• ISSN: 1367-9120; 1878-5786
• DOI: 10.1016/j.jseaes.2015.07.017

•It established a detailed chronological framework for regional geological studies.•The borehole is up to 720m and has high sedimentation rate.•Frequency-dependent susceptibility is more effective than magnetic susceptibility.•Sedimentation rate archives three regional tectonic subsidence events since 3.4Ma. The basin sediment provides an important means of studying regional tectonic actives; however, regional climate factors, overlaying tectonic actives, affect the sedimentary process in the basin. Because of the lack of long-term scales data, the research on climate change in the arid and semi-arid region is limited. The PL02 core, located in the center area of deposition in the Yinchuan Basin, has a thick deposit with a higher resolution and sedimentation rate, making itself practical for the reconstruction of the paleoclimate and the coupling relationship between regional tectonic activities and climate change. The study of the 720-m borehole near Pingluo County is presented in this paper. The chronostratigraphic sequence of the core is established by palaeomagnetic dating. The magnetostratigraphic correlation to the geomagnetic polarity timescale shows that the PL02 core recorded the Brunhes, Matuyama, Gauss, Jaramillo, Olduvai, Kaena and Mammoth polarity chron or subchron. The sedimentation rate and the magnetostratigraphic of the core indicate that the onset of the PL02 core in this section occurred at ∼3.4Ma BP. The analysis of the core established a detailed chronological framework for regional geological research. At the stage of 3.22–3.04Ma, 2.581–1.95Ma and after 0.012Ma, the sedimentation rate increases gradually, which archive three regional tectonic subsidence events. The frequency-dependent susceptibility of the sediment is used to reconstruct the paleoclimatic change. The frequency-dependent susceptibility is more effective than the magnetic susceptibility on reflecting regional climate change in the basin. From 3.4 to 0.467Ma, the gradual decrease of frequency-dependent susceptibility reflects the regional climate change from warm and humid to cold and dry. Since 0.467Ma, the gradual increase of the frequency-dependent susceptibility corresponds to the climate becoming warm and humid again.