Abstract
The Holocene Warm Period (HWP) provides valuable insights into the climate system and biotic responses to environmental variability and thus serves as an excellent analogue for future global climate changes. Here we document, for the first time, that warm and wet HWP conditions were highly favourable for magnetofossil proliferation in the semi-arid Asian interior. The pronounced increase of magnetofossil concentrations at ~9.8 ka and decrease at ~5.9 ka in Dali Lake coincided respectively with the onset and termination of the HWP, and are respectively linked to increased nutrient supply due to postglacial warming and poor nutrition due to drying at ~6 ka in the Asian interior. The two-stage transition at ~7.7 ka correlates well with increased organic carbon in middle HWP and suggests that improved climate conditions, leading to high quality nutrient influx, fostered magnetofossil proliferation. Our findings represent an excellent lake record in which magnetofossil abundance is, through nutrient availability, controlled by insolation driven climate changes.
Highlights
The Holocene Warm Period (HWP) provides valuable insights into the climate system and biotic responses to environmental variability and serves as an excellent analogue for future global climate changes
We investigated the magnetic properties of an 8.5-m Holocene lake sediment core from Dali Lake, Inner Mongolia, northern China (Fig. 1), in which the magnetic properties are controlled by biogenic and detrital magnetic minerals
The S-ratio, which is a composition-dependent parameter, is defined as the ratio of isothermal remanent magnetization acquired at 20.3 T (IRM–0.3T) to saturation IRM acquired at 1 T (IRM1T, hereinafter termed SIRM)[12], has high values throughout the studied core (Fig. 2a)
Summary
The Holocene Warm Period (HWP) provides valuable insights into the climate system and biotic responses to environmental variability and serves as an excellent analogue for future global climate changes. For the first time, that warm and wet HWP conditions were highly favourable for magnetofossil proliferation in the semi-arid Asian interior. Hyperthermal events in geological times, such as Palaeocene-Eocene Thermal Maximum, Early Eocene Climate Optimum, Mid-Miocene Climate Optimum, and Holocene Warm Period (HWP), are believed to have profoundly changed global and/or regional hydrologic cycles, and significantly reshape sedimentary and biological processes in marine and terrestrial environments[8,9]. Our results document the first biomagnetic record of HWP climate variability at the northern limit of the East Asian summer monsoon. The biomagnetic response to the HWP is unambiguously demonstrated using a combination of magnetic measurements (Figs. 2–4) and TEM analyses (Fig. 5)
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