Paleomagnetic Secular Variation and Relative Paleointensity During the Holocene in South China—Huguangyan Maar Lake Revisited

Abstract

The scarcity of reliable paleomagnetic secular variation (PSV) records from East Asia especially from low-latitude regions impedes better understanding of global PSV mechanisms. Here we report on a radiocarbon-dated Holocene PSV record from a composite ~6.7-m-long core collected from the high-sedimentation-rate Huguangyan Maar Lake (HML) in subtropical-tropical South China. Rock magnetic results demonstrate that the natural remanent magnetization resides in single-domain magnetite. Alternating field demagnetization experiments at 1-cm spacing on u-channel samples reveal six distinct inclination highs at ~7,500 BCE, ~5,100 BCE, ~4,600 BCE, ~3,600–3,400 BCE, ~1,600–1,200 BCE, and 600–800 CE; three inclination lows at ~4,800 BCE, ~600–300 BCE, and ~1,000–1,300 CE; and three eastward declination trends at ~3,600–3,200 BCE, ~2,600–2,400 BCE, and 400 BCE to 200 CE. The similarity between the HML PSV record and other independently dated records from East Asia and geomagnetic field models corroborates the robustness of our age model and Holocene PSV record. Strikingly, centennial- to millennial-scale PSV features of the HML are comparable, within age uncertainties, with other Holocene records from Europe, North America, and Canada, suggesting that such directional patterns are likely to be hemispheric in scale. Although relative paleointensity data of HML are affected by environmental factors (e.g., organic matter diagenesis), the record still provides a regionally important new PSV reference curve whose conspicuous features may serve as stratigraphic markers for East Asian paleorecords.