U-Th dated speleothem recorded geomagnetic excursions in the Lower Brunhes

Area of Science:

• Paleomagnetism
• Geophysics
• Quaternary Geology

Background:

• Understanding Earth's magnetic field behavior is crucial.
• Geomagnetic excursions provide insights into past magnetic field instabilities.
• Flowstone records offer continuous archives of geomagnetic variations.

Purpose of the Study:

• To present the geomagnetic record from a flowstone core in Liguria, Italy.
• To analyze geomagnetic excursions during the Lower Brunhes chron.
• To investigate the relationship between flowstone growth rate and climate stages.

Main Methods:

• A 2.29-m-long continuous flowstone core was sampled and dated using U-series.
• Magnetic remanence was measured using u-channel and deconvolved.
• High-resolution dating established the age of the flowstone from Marine Isotopic Stage (MIS) 13 to MIS 7.

Main Results:

• Four geomagnetic excursions (Basura 1, 2, 3, and 4) were identified within the flowstone.
• Basura 1, 2, and 3 exhibit overlapping ages due to U-Th dating uncertainties.
• Basura 4 is well-dated to 417 ± 7/8 ka and is distinguishable from the other events.

Conclusions:

• The flowstone provides a detailed record of geomagnetic behavior during the Lower Brunhes.
• Basura 4 represents a significant geomagnetic event, potentially a new excursion.
• The study highlights the importance of flowstones in paleomagnetic research.