Magnetic mineralogy of the Baringo core (HSPDP-BTB13-1A, Kenya) shows astronomical forcing with implications for retrieving meaningful paleointensity

Abstract

This study evaluates the potential of the BTB13 sedimentary core from the Baringo Basin, Kenya, to contribute to relative paleointensity (RPI) records and improve geochronological correlations across Eastern Africa. The core, spanning ~3.3-2.6 Ma, is part of the Hominin Sites Paleolakes Drilling Project (HSPDP) and has a robust age model based on magnetostratigraphy and 40Ar/39Ar dating. High-resolution rock magnetic analyses, including NRM/ARM ratios and pseudo-Thellier RPI methods, were applied to test the suitability of the core for RPI reconstruction. Results indicate that the magnetic signal is dominated by environmental rather than geomagnetic influences, with large amplitude NRM/ARM variations failing standard selection criteria for RPI. Spectral analysis reveals strong periodicities at ~22, ~40, ~50, and ~400 kyr, aligning with orbital parameters and suggesting that the magnetic signal is climatically driven, likely linked to lake level changes paced by precession and obliquity cycles. While unsuitable for RPI-based correlations, the BTB13 core preserves a valuable astrochronological signal that can support regional correlation and paleoenvironmental reconstruction in the context of hominin evolution.