Records of geomagnetism, climate, and tectonics across a Paleoarchean erosion surface

Abstract

Paleomagnetism has provided key constraints on the evolution of Earth's climate, geomagnetic field, and continental geography through Phanerozoic and Proterozoic time. Extending these constraints into the Archean eon has been particularly challenging due to the paucity of the ancient rock record. Here we report paleomagnetic measurements on the NASA Astrobiology Drilling Project (ABDP)-8 core drilled through one of the world's least deformed and least metamorphosed Paleoarchean [3200–3600 million year old (Ma)] rock successions located in the East Strelley Belt of the eastern Pilbara Craton, Australia. Our results show that the ∼3350 Ma Euro Basalt preserves a shallow magnetic inclination that appears to have formed as a result of early seafloor hydrothermal alteration, suggesting that the evaporitic carbonate platform of the conformably underlying Strelley Pool Formation was deposited in a near-equatorial location. This is consistent with (although does not require) late Paleoarchean climatic zoning, low orbital obliquity, and a geocentric axial dipole (GAD) field geometry similar to that of the Phanerozoic. The Euro Basalt paleopole overlaps with previously published Paleoarchean poles from the East Pilbara craton and with time-equivalent poles reported from the Barberton Greenstone Belt of the Kaapvaal craton, supporting the existence of a Paleoarchean Vaalbara continental aggregation.