Earth and Planetary Science

The Ironian Ocean and the 2.2–1.8 Ga Introversion Process in the Formation of the Columbia (Nuna) Supercontinent

Alexandre de Oliveira Chaves

Federal University of Minas Gerais (UFMG)

DOI: https://doi.org/10.36956/eps.v4i2.2161

Received: 15 May 2025; Published: 9 July 2025

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Abstract

Robust evidence on the existence of the Columbia (Nuna) supercontinent's internal ocean—the Ironian Ocean (name proposed here for the first time)—has been compiled from scientific literature. Remnants of Superior-type banded iron formations suggest the 2.5–2.2 Ga ocean spreading stage, as well as eclogites, blueschists, oceanic plateau, eclogite xenolith and ophiolites point to 2.2–1.8 Ga ocean closure stage along its suture zone. The 2.10–1.95 Ga collisional orogens of the Columbia (Nuna) supercontinent would have been formed throughout impact of continental lithospheric fragments during the consumption of the Ironian internal ocean by introversion process developed in the formation of the Columbia (Nuna) in the Paleoproterozoic Earth. These collisional orogens are located along the suture zone of the Ironian ocean, in a situation that indicates the process of introversion. Although tectonic stress associated with the 1.9-1.8 Ga accretionary and intracontinental orogenies contributed complementarily to the assembly of Columbia (Nuna) around 1.75 Ga, this supercontinent formed essentially by collisional orogenesis during Ironian Ocean closure and therefore by introversion process.

Keywords: Columbia (Nuna) Supercontinent, Internal Ocean, Introversion, Ironian

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