Absolute geomagnetic paleointensities obtained from the Americas’ presumably oldest pottery

Abstract

We carried out a detailed rock-magnetic and absolute paleointensity investigation on well-dated, presumably the oldest American pottery from northern Colombia (around 4000 B.C.) The study aims to contribute to the reconstruction of Earth’s Magnetic Field strength fluctuations in the southern hemisphere, improving extremely incipient archaeomagnetic database for the Caribbean region through comprehensive rock-magnetic and archaeointensity analysis of Puerto Chacho pottery (Lat: 10° .110 N, Long: 75° .455 W). Essentially Ti-poor titanomagnetite and some fractions of hematite are main magnetic carriers of apparently pseudo-single-domain state. Individual intensities obtained from Puerto Chacho archaeological site vary from 8.7 ± 0.5 to 27.3 ± 1.2 μT, which corresponds to the Virtual Axial Dipole Moments (VADM) values between 2.2 ± 0.1 and 6.8 ± 0.3 10²² Am². The mean Puerto Chacho’s intensity determined for all twenty-three accepted values is 17.1 ± 6.2 μT, corresponding to the mean VADM of 4.2 ± 1.5 10²² Am². These values are significantly lower compared to nearby San Jacinto paleointensities (Goguitchaishvili et al. in Phys Earth Planet Interiors 31:107061, 2023), considered belonging older archaeological periods. Moreover, the absolute intensity values obtained from the Puerto Chacho pottery yielded relatively low values compared to those derived from three available global field prediction models SHA.DIF.14 K, CALS10k.1b and ArchKalmag.14 K and existing data obtained from previously published studies from Colombia and surrounding areas. A bootstrap analysis of available age distributions and updated radiocarbon calibration values indicate that absolute age intervals for Puerto Chacho are younger, which may explain the difference between the intensity values. The time interval between 6000 and 5000 BP was probably characterized by some drastic variations of the Earth’s magnetic Field strength. Although many studies have recently become available, no conclusions may be drawn about the regional fluctuations of the geomagnetic field strength.