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The final assembly of Pangea is thought to be marked by the Siberia‐Laurussia amalgamation during the Late Carboniferous–Permian, but there are large uncertainties on the timing of the amalgamation in the previous paleogeographic reconstructions because there are no high‐quality Carboniferous–Permian paleomagnetic data available from the Siberian continent. The Zharma‐Saur area in the junction between the Siberia‐Laurussia amalgamation, involving the Zharma‐Saur arc on the northern margin of the Kazakhstan microcontinent, the South Chinese Altai terrane in the southern margin of the Siberian continent and the Irtysh‐Zaisan suture in between, can provide crucial geological constraints for the assembly of Pangea. In the Zharma‐Saur arc, the Tournaisian–Visean marine sequences are interbedded with thick pillow lavas, which were formed during southward subduction of the Irtysh‐Zaisan Ocean and unconformably covered by the Moscovian terrestrial bimodal volcanic associations and sedimentary successions, in which the basalts are columnar‐jointed in structure and the sandstones also contain the detritus derived from the South Chinese Altai terrane. The Serpukhovian–Bashkirian unconformity was coeval with the transition from the Tournaisian–Visean calc‐alkaline to the Moscovian–Early Permian high alkaline and bimodal volcanism. These dramatic changes in sedimentary environments, provenances and volcanism together indicate the Siberia‐Laurussia amalgamation during the Serpukhovian–Bashkirian and this event was almost simultaneous with the Laurussia‐Gondwana collision and the welding of Laurussia with the Kazakhstan microcontinent, but slightly earlier than the Laurussia‐Tarim collision. Therefore, the final assembly of Pangea could be completed in the Late Carboniferous.
Plain Language Summary
The previous paleogeographic reconstructions generally show that the Pangea supercontinent was formed at ∼250 Ma (million years ago) when the Siberian continent collided with the Laurussia continent. However, the timing of the Siberia‐Laurussia collision is ambiguous and needs to be constrained by geological records because the high‐quality paleomagnetic data for positioning are insufficient in the Siberian continent during 360–250 Ma. For this purpose, we carried out the investigation on the 350–290 Ma sedimentological and volcanic records in the junction between the two continents. We find that the volcanism generated by the convergence of two continents and marine sedimentation were terminated at ∼320 Ma, followed by the terrestrial sedimentary strata and intracontinental volcanism. Importantly, the detritus from the southern margin of the Siberia continent can be transported to the northern margin of the Laurussia continent since ∼310 Ma. These data show that the Siberia‐Laurussia collision was happened during 320–310 Ma. This event was almost coeval with not only the Laurussia‐Gondwana collision but also the incorporations of the Tarim and Karakum‐Tajik continents into the Pangea supercontinent. Therefore, the Pangea supercontinent was already formed at ∼320 Ma rather than ∼250 Ma in the previous paleogeographic reconstructions.
Key Points
Geological records show the Laurussia‐Siberia amalgamation in the Serpukhovian–Bashkirian
The final assembly of Pangea was completed in the Late Carboniferous rather than the latest Permian