Earth’s oldest tsunami deposit? Early Archaean high-energy sediments in the ca 3.48 Ga Dresser Formation (Pilbara, Western Australia)

Abstract

Dynamic sedimentary processes are a key parameter for establishing the habitability of planetary surface environments on Earth and beyond and thus critical for reconstructing the early evolution of life on our planet. This paper presents a sedimentary section from the ca 3.48 Ga Dresser Formation (Pilbara Craton, Western Australia) that contains high-energy reworked sediments, possibly representing the oldest reported tsunami deposit on Earth to date. Field and petrographic evidence (e.g. up to 20 cm large imbricated clasts, hummocky bedding, Bouma-type graded sequences) indicate that the high-energy deposit represents a bi-directional succession of two debrite–turbidite couplets. This succession can best be explained by deposition related to passage and rebound of tsunami waves. Sedimentary processes were possibly influenced by highly dense silica-rich seawater. The tsunami was probably triggered by local fault-induced seismic activity since the Dresser Formation was deposited in a volcanic caldera basin that experienced syndepositional extensional growth faulting. However, alternative triggers (meteorite impact, volcanic eruption) or a combination thereof cannot be excluded. The results of this work indicate a subaquatic habitat that was subject to tsunami-induced high-energy disturbance. Potentially, this was a common situation on the early Archaean Earth, which experienced frequent impacts of extraterrestrial bodies. This study thus adds to the scarce record of early Archaean high-energy deposits and stresses the relevance of high-energy depositional events for the early evolution of life on Earth.