Matuyama/Brunhes (M/B) Transition Recorded in Chinese Loess.

Donghuai, Sun; Shaw, John; An, Zhisheng; Rolph, Tim

doi:10.5636/jgg.45.319

Cited by 31 publications

(33 citation statements)

References 19 publications

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“…In addition to the major magnetozones, some researchers have focused on shorter geomagnetic polarity changes such as polarity reversals Sun et al, 1993;Zhu et al, 1993Zhu et al, , 1994a and geomagnetic excursions (e.g., Zhu et al, 1994bZhu et al, , 1998Zhu et al, , 2006Fang et al, 1997;Pan et al, 2002;Yang et al, 2004). Although the exact magnetization process of loess is not yet well understood, many short-lived geomagnetic excursions, such as the Mono Lake and Laschamp at loess L1 (Zhu et al, 1999(Zhu et al, , 2000Pan et al, 2002), Blake at paleosol S1 (Zhu et al, 1994b;Zheng et al, 1995;Fang et al, 1997;Pan et al, 2002), Santa Rosa at loess L9 (Pan et al, 2002;Yang et al, 2004), and Punaruu at loess L13 (Pan et al, 2002;Yang et al, 2005), have been observed from several different loess sections.…”

Section: Introductionmentioning

confidence: 99%

Early and middle Matuyama geomagnetic excursions recorded in the Chinese loess-paleosol sediments

et al. 2007

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A detailed paleomagnetic and rock-magnetic investigation on the early and middle Matuyama loess-paleosol sediments has been carried out at the Baoji section, Shaanxi province, southern Chinese Loess Plateau. Our new magnetostatigraphy revises the position of the lower Olduvai boundary from L27 to S26. Seven shortlived geomagnetic excursions, tentatively named as E1, E2, E3, E4, E5, E6, and E7, have been recognized in the L13, S22, L26, L27, S29, and upper and middle parts of L32, respectively. Results of the anisotropy of low-field magnetic susceptibility (AMS) show that the studied loess-paleosol sediments retain the primary sedimentary fabric. Rock magnetic experiments reveal that the sediments from the excursional and polarity transitional intervals have the same magnetic characteristics as those from the surrounding normal and reversed polarity intervals. Assuming a constant accumulation rate between polarity boundaries, these seven excursions are estimated to be at about 1.11 Ma (E1), 1.58 Ma (E2), 1.92 Ma (E3), 2.11 Ma (E4), 2.25 Ma (E5), 2.35 Ma (E6), and 2.42 Ma (E7) Ma. The E1 and E2 in the middle Matuyama Chron can be correlated with the Punaruu and Stage 54 (Gilsa) excursions, respectively. The E4, E5, and E7 in the early Matuyama Chron can be correlated with the Réunion II, Réunion I, and cryptochron C2r.2r-1 (X-subchron), respectively. The E3 in the lower Olduvai subchron and E6 in the early Matuyama Chron have no comparable events. At present they can only be correlated with the anomalous directions observed in the Osaka Bay core (Biswas et al., 1999). Therefore, further investigations are necessary to support their global occurrences. The present result together with the two late Matuyama excursions dated at about 0.89 Ma and 0.92 Ma (Yang et al., 2004) show that the Baoji section yields at least nine Matuyama excursions which, along with the results of the study, suggests that eight excursions occur at 0.9-2.2 Ma (Channell et al., 2002), thereby providing evidence that the short-lived geomagnetic excursions may also be a basic characteristic of the geomagnetic field during the Matuyama Chron.

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Section: Introductionmentioning

confidence: 99%

Early and middle Matuyama geomagnetic excursions recorded in the Chinese loess-paleosol sediments

et al. 2007

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“…Guo et al, 2002) and Xifeng (Liu et al, 1988;Sun et al, 1993;Zhu et al, 1993) , 1990;Tauxe et al, 1996;Channell et al, 2010). To reconcile this inconsistency, Zhou and Shackleton (1999) proposed that paleomagnetic signals recorded by Chinese loess are misplaced because of a large magnetic lock-in depth.…”

Section: Stratigraphic Position and Age Of The Mbbmentioning

confidence: 93%

Magnetostratigraphy of Chinese loess–paleosol sequences

Liu

Jin

et al. 2015

Earth-Science Reviews

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“…The high sedimentation rates of the loess should assist such studies compared to the generally lower rates for marine sediments. Sun et al (1993) investigated the M/B transition from the Xifeng section, which spans a 3.8 m stratigraphic interval and corresponds to a time interval of 20 kyr. Paleomagnetic directions from the transition have a complex pattern with five polarity switches between normal and reversed polarity.…”

Section: Magnetostratigraphy and Geomagnetism Of Chinese Loessmentioning

confidence: 99%

How does Chinese loess become magnetized?

Zhao

Roberts

2010

Earth and Planetary Science Letters

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Thick loess deposits on the Chinese Loess Plateau provide an outstanding archive of paleoclimate, geomagnetic field and paleoenvironmental changes over at least the last 2.6 Ma. Much work on magnetic polarity reversals, pedogenic magnetic enhancement and climatic change has been carried out over the past 30 years. However, questions about how Chinese loess becomes magnetized remain unanswered. In this thesis, I have sought to address key questions concerning magnetization processes in the Chinese loess. To understand magnetization processes, it is important to understand which magnetic minerals are present and the processes that caused them to be present. Magnetic and other analyses of both loess and paleosol samples indicate that pedogenic superparamagnetic and single domain magnetite and hematite can be present. The mass concentration of hematite can exceed 90% of the magnetic particle assemblage. An eolian dust deposition simulator designed for laboratory redeposition experiments was then used to demonstrate that both a depositional remanent magnetization (DRM) and a post-depositional remanent magnetization (PDRM) can be acquired by Chinese loess. Water content significantly affects the efficiency of PDRM acquisition. No significant PDRM was observed when the water content was below a critical threshold of 40%. Published paleomagnetic data from the Chinese loess indicate the widespread occurrence of inclination error. Detailed paleomagnetic studies of U-channel samples from the last loess/paleosol sequence at Yuanbao were made to assess whether the Chinese loess can accurately record geomagnetic relative paleointensity variations. Three normalized remanence records were determined using conventional normalization as well as the pseudo-Thellier method. Strong coherence among the normalized remanence records indicate that the whole range of magnetic minerals has been affected by pedogenesis. Poor similarity among published normalized remanence records from the Chinese loess, as well as with marine relative paleointensity records indicate that the Chinese loess is not suitable for relative paleointensity determinations. The range of magnetic minerals present and their varying distribution within loess and paleosol sediments indicate that the magnetization is due to a mixture of remanence acquisition mechanisms including DRM, PDRM, chemical remanent magnetization (CRM) and viscous remanent magnetizations, which also indicates complexities in remanence acquisition that will complicate attempts to extract relative paleointensity information. This thesis has provided an improved understanding of the mechanisms of Chinese loess magnetization, and re-emphasizes the importance of pedogenic CRM acquisition.

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Matuyama/Brunhes (M/B) Transition Recorded in Chinese Loess.

Cited by 31 publications

References 19 publications

Early and middle Matuyama geomagnetic excursions recorded in the Chinese loess-paleosol sediments

Early and middle Matuyama geomagnetic excursions recorded in the Chinese loess-paleosol sediments

Magnetostratigraphy of Chinese loess–paleosol sequences

How does Chinese loess become magnetized?

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