Eocene relative paleointensity of the geomagnetic field from Integrated Ocean Drilling Program Site U1403 and U1408 sediments in the northwest Atlantic

Yamamoto, Yuhji; Fukami, Hiroto; Lippert, Peter C.

doi:10.1016/j.epsl.2022.117518

Cited by 2 publications

(1 citation statement)

References 38 publications

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“…Examples of the achievement of RPI estimations are the establishment of the global RPI stacks such as the Sint‐2000 stack for the last 2 Myr (Valet et al., 2005) and the PISO‐1500 stack for the last 1.5 Myr (Channell et al., 2009). For older ages, global RPI stacks have not yet been established, but the number of RPI curves reported is increasing (Ohneiser et al., 2013; Tauxe & Hartl, 1997; Yamamoto et al., 2014, 2022; Yamazaki & Yamamoto, 2018). On the other hand, limitations of the current RPI estimations are widely recognized.…”

Section: Introductionmentioning

confidence: 99%

Difference in Relative Paleointensity Recording Efficiency of Magnetic Mineral Constituents in a Sediment Core Off Chile

Yamazaki

Shimono

et al. 2023

JGR Solid Earth

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Progress of relative paleointensity (RPI) estimations using marine sediments has greatly contributed to better understanding of the behavior of the past geomagnetic field. To enhance further the reliability of RPI estimations, we must overcome the problem that climatically induced variations of magnetic‐mineral assemblages in sediments may influence RPI records. Two major constituents of magnetic‐mineral assemblages in marine sediments are magnetofossils and detrital magnetic minerals, and the latter consists of silicate‐hosted magnetic inclusions and unprotected magnetic minerals. It is necessary to understand different RPI recording efficiencies among those constituents to tackle the problem, but previous evaluations were inconclusive. We studied this issue using a sediment core taken from the southeast Pacific Ocean. Rock‐magnetic investigations revealed that the magnetic mineral assemblage of this core during the last ∼900 ka is a mixture of low‐coercivity magnetofossils and middle‐coercivity detrital unprotected partially oxidized magnetite. Natural remanent magnetization (NRM) vs. isothermal remanent magnetization (IRM) demagnetization diagram showed strong convex curvature, and RPI signals carried by the two components could be separated by calculating RPI from the gradients of 20–40 and 70–160 mT segments. We confirmed that RPI recording efficiency of magnetofossils is lower than that of detrital unprotected magnetites/maghemites. Because of the marginal overlap between the coercivity ranges of the two components, changes in their relative abundance do not influence RPI estimations. This condition is ideal for RPI estimations, and the resulted RPI curve closely coincides with that of the PISO‐1500 stack despite changes in the relative abundance of the two components.

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Section: Introductionmentioning

confidence: 99%

Difference in Relative Paleointensity Recording Efficiency of Magnetic Mineral Constituents in a Sediment Core Off Chile

Yamazaki

Shimono

et al. 2023

JGR Solid Earth

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Stepwise astronomical tuning of obliquity-driven evaporite cycles in an Eocene salt lake (Jianghan Basin, Hubei Province, China): Implications for middle Eocene East Asian monsoon-like climate evolution

Kong,

Jiang,

et al. 2024

Geological Society of America Bulletin

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The rhythmic evaporation cycle is an ideal recorder of astronomical cycle signals, but studies on cyclostratigraphy have yet to be directly conducted on halite-rich strata. The Qianjiang Depression of the Jianghan Basin is a representative Eocene East Asian halite-rich basin, and the salt rhythmites that developed therein are important recorders of climate evolution in East Asia. This study selected five wells for basin-scale cyclostratigraphy analysis, taking the Lower Qian 4 member of the Qianjiang Formation as the research object. This study found that the basinal salt lake facies were dominated by obliquity cycles, whereas the shallow-water deposits mainly recorded short eccentricity cycles. The study also found that s3−s6 obliquity cycles could be detected throughout the salt lake sedimentary record. Therefore, a stepwise astronomical tuning scheme was adopted. First, the target intervals in different sedimentary areas were preliminarily tuned to s3−s6 obliquity cycles, and stratigraphic correlation was performed. Then, the tuned data were further adjusted using obliquity cycles to reveal the impact of obliquity on the development of salt rhythmites and establish a floating astronomical time scale (ATS). Sedimentary noise models and pollen analysis further demonstrated that obliquity amplitude modulation cycles drove periodic changes in hydrology and climate. Based on the spatiotemporal distribution of salt rhythmite−rich strata in Paleogene East Asia, this study proposes that the development of rhythmic evaporites can reveal the existence of a monsoon-like climate. Astronomical influence was an important driving force for developing the middle Eocene East Asian monsoon.

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Eocene relative paleointensity of the geomagnetic field from Integrated Ocean Drilling Program Site U1403 and U1408 sediments in the northwest Atlantic

Cited by 2 publications

References 38 publications

Difference in Relative Paleointensity Recording Efficiency of Magnetic Mineral Constituents in a Sediment Core Off Chile

Difference in Relative Paleointensity Recording Efficiency of Magnetic Mineral Constituents in a Sediment Core Off Chile

Stepwise astronomical tuning of obliquity-driven evaporite cycles in an Eocene salt lake (Jianghan Basin, Hubei Province, China): Implications for middle Eocene East Asian monsoon-like climate evolution

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