Neocratonic magmatic‐sedimentary basins of post‐Variscan Europe and post‐Kanimblan eastern Australia generated by right‐lateral transtension of Permo‐Carboniferous Pangaea

Abstract

A B S T R A C TThe stress from the initial coalescence of Pangaea during the mid-Carboniferous (320 Ma) collision of Gondwanaland and Laurussia in the Variscan (Sudetic) magmatic fold belt was transmitted through Pangaea to generate the nappes and thrusts that dismembered the intracratonic Centralian Superbasin during the Alice Springs Orogeny and the megakinks that terminally deformed the Lachlan fold belt along the subducted Andean-type margin of eastern Australia. Definitive collision was followed by a lacuna on the Pangaean platform that reflects uplift. T h e first release of heat at ~3 0 0Ma from the self-induced Pangaean heat anomaly weakened the hypersensitive neocratonic crust of the inactive but still hot European and eastern Australian magmatic fold belts to become stress guides for right-lateral transtension during anticlockwise rotation of Pangaea. Deep transtensional fractures provided a way into and through the neocratonic crust for magma ranging from S-type granite to rhyodacitic ignimbrite to basalt, with alkaline undersaturated rocks in some rifts.Lagging behind the magma, the platform subsided at ~2 9 0 Ma in basins by differential weakening of the crust during the release of Pangaean heat. T h e Gondwana facies accumulated in the Gondwanaland province and the Stephanian-Rotliegend succession in Europe. T h e basins of Europe and eastern Australia continued to grow by transtension followed by mid-Permian (270-265 Ma) thermal sagging and rifting. Their histories then diverged. Europe maintained its post-orogenic course except in the Alpine region, where rifting and sagging continued to accommodate the western Tethys. The eastern fringe of Australia entered a new, Innamincka, orogenic cycle that developed in embryo at 265 Ma to a fully developed magmatic arc and yoked foreland basin at 258 Ma.

The Karoo basins of south-central Africa

“…Although the onset of rifting was triggered by an anomalous heat accumulation under the insulating blanket of the vast continental crust, transtension was the controlling mechanism for the establishment of rift directions. The forces were created by the opening of Neotethys combined with the right-lateral rotation between Gondwana and Laurasia (Veevers et al, 1994a). The release of heat from the self-induced heat anomaly is considered the cause for the sagging and the formation of the syneclise-type basins on the western side of African Gondwana.…”

“…Most likely it originated in Oman, where Permian pillow lavas and marine cherts occur at the base of the sequence (Lee, 1990). Veevers et al (1994a) suggested heat congestion beneath Pangea and right lateral translation between Gondwana and Laurasia as a possible cause for the creation of the Late Palaeozoic strain distribution.…”

Paleostress field reconstruction in the Oslo region

“…This event comprised the transformation of the Variscan fold belt into a wrench system accompanied by extension to the north (Neumann et al, 2004;Olaussen et al, 1994;Ziegler, 1990) and expressed by Permo-Carboniferous deformation along the Sorgenfrei-Tornquist Zone and concurrent tectonics in the Oslo Region (Glennie, 1984;Erlströ m et al, 1997;Sundvoll et al, 1990Sundvoll et al, , 1992Veevers et al, 1994;Ziegler, 1990). These connections are also emphasised by some stratigraphic units in the Oslo Rift System that exhibit similarities to the Lower Rotliegendes in the Northern Permian Basin (Ziegler, 1990), thus suggesting the region to be a prolonged northern branch of the Central European Basin System (Larsen et al, 2008b).…”

Eastern Australia

“…Stage A represents the base of the Pangean supersequence (Veevers, 1990a), and its 0.5 x 10 6 km 2 of magmatic rocks is comparable in extent and content to the coeval deposits of Europe (Veevers et al, 1994b). These are the only regions in the early Pangea that are dominated by magmatic rocks.…”