Geomagnetic secular variations over the last 23 ka recorded in Lake Chala, eastern equatorial Africa

Abstract

Documenting the Earth’s magnetic field variations through time is fundamental for several disciplines. However, current geomagnetic models heavily rely on datasets biased towards mid- and high northern latitudes, whereas data from Africa and surrounding oceans are particularly underrepresented. In this study, we present a new record of paleo-secular variations (PSV) in geomagnetic field inclinations during the last 23 ka from Lake Chala, situated at 3° S near Mt Kilimanjaro in eastern equatorial Africa. This deep groundwater-fed crater lake is characterized by a high sedimentation rate (ca. 1 cm/10 years) and a particularly well-constrained age model based on 210Pb and 14C dating; and rock magnetic analyses have demonstrated the magnetic stability of the sediments. The Chala dataset is linked to PSV records from Lake Malawi and Lake Victoria using a sequence slotting technique to generate a composite PSV record for East Africa. The Lake Chala PSV record not only represents an important contribution toward a better understanding of local and global features of the Earth’s magnetic field, but also expands the utility of paleomagnetism as a key tool for dating of, and cross-correlation between, lake-based paleoenvironmental records and archeological sites throughout eastern tropical Africa.