A sedimentary paleomagnetic record of the upper Jaramillo transition from the Lantian Basin in China

Yi Wu,Shifan Qiu,Zhaoyu Zhu,Zhiguo Rao,Tingping Ouyang

doi:10.1186/s40623-015-0341-9

Abstract

The termination of the Jaramillo (normal to reverse) subchron is a key chronostratigraphic marker for dating global Pleistocene sedimentary sequences. However, the stratigraphic position of the geomagnetic polarity reversal varies greatly across the Chinese Loess Plateau (CLP), from near the bottom of paleosol unit S9 to the middle-upper part of S10. Here, we present paleomagnetic and rock magnetic results from high-resolution sampling of the Yushan loess section of the Lantian Basin located within the southern CLP. Our combined analyses determine that the polarity reversal is located in the middle-lower part of the paleosol unit S10. This stratigraphic position is lower than most of other studies conducted throughout the CLP. We attribute the difference in the location of the reversal to a deeper lock-in depth of remanence acquisition, which may have occurred from postdepositional processes under favorable hydrothermal conditions along the southern margin of CLP. It is important to note that age determinations through magnetic stratigraphy on sedimentary sections, particularly in discontinuous and/or imperfect sequences, should be treated with caution; there are significant differences with respect to the location of the polarity reversal throughout the CLP.

Highlights

IntroductionSignificant progress has occurred in the construction of the chronological framework for the thick, continuous Quaternary loess sediments over throughout northern China (Heller and Liu 1982; Burbank and Li 1985; Liu 1985; Kukla 1987; Kukla et al 1988; Liu et al 1988; Rolph et al 1989; Yue 1989, 1995; An et al 1991; Zheng et al 1992; Ding et al 1994, 2002; Porter and An 1995; Lu et al 1999; Heslop et al 2000; Sun et al 2006; Liu et al 2015)
There are three sub-units of paleosols labeled as S5-1, S5-2 and S5-3 in the paleosol unit S5, two sub-units labeled as S6 and S6’ in S6, and two sub-units labeled as S9-1 and S9-2 in S9 (e.g., Liu 1985; Ding et al 2002)
The slight decrease of magnetization when temperature rises above 580 °C might indicate the existence of hematite

Summary

Introduction

Significant progress has occurred in the construction of the chronological framework for the thick, continuous Quaternary loess sediments over throughout northern China (Heller and Liu 1982; Burbank and Li 1985; Liu 1985; Kukla 1987; Kukla et al 1988; Liu et al 1988; Rolph et al 1989; Yue 1989, 1995; An et al 1991; Zheng et al 1992; Ding et al 1994, 2002; Porter and An 1995; Lu et al 1999; Heslop et al 2000; Sun et al 2006; Liu et al 2015). There are three sub-units of paleosols labeled as S5-1, S5-2 and S5-3 in the paleosol unit S5, two sub-units labeled as S6 and S6’ (or S6 and S6-1) in S6, and two sub-units labeled as S9-1 and S9-2 in S9 (e.g., Liu 1985; Ding et al 2002)

Methods

Results

Discussion

Conclusion