Speleothem Palaeosecular Variation Records from China: Their Contribution to the Coverage of Holocene Palaeosecular Variation Data in East Asia.

Abstract

Five stalagmitic speleothems from two caves in Sichuan province China, have yielded data on the palaeosecular variation (PSV) of the past 8.9 ka. The uranium-thorium disequilibrium method has been utilised in order to estimate the age of each record. Due to the high detrital load contributing some allogenic thorium, age corrections had to be applied to most sub-samples. The directional agreement between coeval central and lateral sub-samples where growth layers are horizontal and steeply dipping respectively suggests that inclination errors are absent in these speleothems. Correlation between features of declination and inclination in the individual records, even after time-averaging, are reasonable indicating a local consistency in recorded PSV and adding to the reliability of the palaeomagnetic and age data. Comparisons between our speleothem directions and the directions of the modern field drifted westward past our site at 0.13° yr-' suggests westward drifting of non-dipole sources during the past 2.8 ka. Using directional data from two speleothems with the longest growth periods a composite curve covering the past 8.9 ka has been constructed. The resulting VGP path again indicates predominantly westward drift. The declination and inclination features of these speleothems also compare reasonably with features of PSV in contemporaneous records from China and Japan.

Environmental magnetism: Principles and applications

“…Speleothems have been reported to host magnetic minerals whose concentrations are readily measurable using standard rock magnetic techniques [ Perkins , 1996; Openshaw et al , 1997; Lascu and Feinberg , 2011]. Although the main interest of rock magnetic studies of speleothems has been constraining the reliability of records of geomagnetic field behavior (mainly paleosecular variation and geomagnetic reversals), the common occurrence of detrital natural magnetizations indicates that environmental magnetic studies of speleothems can potentially provide useful records of climate variability with U‐Th chronologies that are much more accurate compared to other methods [e.g., Perkins , 1996; Lascu and Feinberg , 2011].…”

Magnetic fingerprint of southern Portuguese speleothems and implications for paleomagnetism and environmental magnetism

“…The main magnetic carrier of stable DRM in speleothems is thought to be detrital (titano)-magnetite [Lascu and Feinberg, 2011;Latham et al, 1979;Lean et al, 1995;Morinaga et al, 1986;Openshaw et al, 1997;Osete et al, 2012;Perkins, 1996;Perkins and Maher, 1993;Pruner et al, 2010;Zhu et al, 2012]. To a lesser extent, maghemite has also been suggested [Brook et al, 2006;Herries et al, 2006;Latham et al, 1989], but its identification has remained ambiguous.…”

“…Implicitly, magnetic studies of speleothems contribute information about two important areas of geosciences. First, speleothems can provide high-resolution records of short-term variations of the ancient geomagnetic field, or their converse, that allow the use of paleomagnetism as a dating tool of speleothems [Lascu and Feinberg, 2011;Latham et al, 1979;Lean et al, 1995;Morinaga et al, 1992;Openshaw et al, 1997;Osete et al, 2012;Pruner et al, 2010;Stock et al, 2005;Strauss et al, 2013]. Second, speleothems can provide a record of climate variability by linking rock magnetic properties to changes in detrital input driven by regional and global climate and environmental forcing parameters [Ellwood and Gose, 2006].…”

Speleothems as Magnetic Archives: Paleosecular Variation and a Relative Paleointensity Record From a Portuguese Speleothem

“…These karstic deposits have been described as reliable Earth magnetic field recorders (Font et al, 2014;Lascu et al, 2016;Latham et al, 1979Latham et al, , 1982Latham et al, , 1986Latham et al, , 1989Lean et al, 1995;Morinaga et al, 1986Morinaga et al, , 1989Martin, 1990;Openshaw et al, 1997;Osete et al, 2012;Ponte et al, 2017). Paleomagnetic data are commonly obtained from three main sources: marine or lake sediments, volcanic rocks, and archeological objects.…”

“…More recently, speleothems have been explored as potential archives of the Earth's magnetic field. These karstic deposits have been described as reliable Earth magnetic field recorders (Font et al, 2014;Lascu et al, 2016;Latham et al, 1979Latham et al, , 1982Latham et al, , 1986Latham et al, , 1989Lean et al, 1995;Morinaga et al, 1986Morinaga et al, , 1989Martin, 1990;Openshaw et al, 1997;Osete et al, 2012;Ponte et al, 2017). Within the last few years, research on speleothem magnetism has grown particularly, with some focus on the magnetic fabric (Zhu et al, 2012), mineralogy and relations with climate (Bourne et al, 2015;Jaqueto et al, 2016;Zhu et al, 2017), and on the origin of the recorded remanent magnetization (Font et al, 2014;Ponte et al, 2017;Strauss et al, 2013).…”