THE UNITED PLATES OF LAURENTIA AND BEYOND: THE PALEOPROTEROZOIC OROGENIC RECORD AND ASSEMBLY OF EARTH'S FIRST SUPERCONTINENT

The United Plates of Laurentia is at heart the story of assembly of Earth’s first true supercontinent, Nuna, We present new appropriately scaled, animated reconstructions for Nuna between 2.2-1.6 Ga, and use them to evaluate its mode and tempo of assembly.

Nuna was formed by closure of the young Manikewan ocean between 2.1 and 1.85 Ga. At least eight major Archean cratons were amalgamated (Superior, Slave, Rae, Wyoming, Gawler-Mawson, Volgo-Uralia, Tungus-Margan, Nain) along with 6 ribbon microcontinents (Hearne, MetaIncognita, Sugluk, Karelia-Kola, Sask, Hottah) and newly assembled blocks (Amazonia, West Africa, Fennoscandia, Proto-Siberia, North China, Proto-Australia, North Atlantic). Manikwan and marginal oceans closed diachronously with a distinct lateral progression, focused on initial ‘eastern’ development of West African and Amazonia and possibly proto-West Australia between 2.1-2.0 Ga (Siberian 1, Magonde, Birimian, Opthalmian, Eburnian orogenies). Post 2.0 Ga the locus of activity switched to the ‘northern’ flank of greater Laurentia (Thelon, Inglefeld, Karelia-Kola, Taltson, Snowbird orogenies) with accretion of microcontinents (Hearne, Slave) and continuing outboard assembly of cratonic nuclei (proto-Siberia, Fennoscandia). Starting at 1.90 Ga, following a major plate reorganization and plume impingement, Manikewan began to contract in earnest, leading to rapid formation and accretion of numerous arcs and major collisional orogens (Trans North China, NAG, Svecofennian, TransHudsonian, Torngat, Luliang, Mozambique, Barramundi). The spatial pattern and nature of Manikewan closure is consistent with Nuna assembly through introversion.

A second phase of continent accretion 1.88-1.84 Ga, welded the essential core of Nuna (and Laurentia) through additions of the Superior, Wyoming, Sask, Marshfield, Hottah, North-South Australia cratons. The terminal collisional phase was focused on the ‘southern’ flank of the supercontinent as was the subsequent switch at 1.8 Ga to peripheral orogenesis (Big Sky, Yavapai, Mojave, Gothian, Makkovik, Isan, Racklan, Pine Creek). The apparent spatially distinct phases of peripheral orogensis along this margin may reflect regions of stronger slab coupling, governed by the segmented nature of oceanic plates in the new exterior peri-Nuna ocean.