Micro‐Blocks in NE Asia Amalgamated Into the Unified Amuria Block by ∼300 Ma: First Paleomagnetic Evidence From the Songliao Block, NE China

Abstract

AbstractAmuria formed in the late Paleozoic through amalgamation of the Mongolia and Songliao‐Jiamusi blocks in the eastern Central Asian Orogenic Belt (CAOB). The exact timing of the assembly is critical towards unraveling the Phanerozoic evolution of the Paleo‐Asian Ocean (PAO) and assembly of the Asian blocks in Pangea. Here, we report the first Permo‐Carboniferous paleomagnetic data from the Songliao‐Jiamusi block, aiming to constrain its relative paleoposition with respect to Mongolia. A stable characteristic remanent magnetization (ChRM) was isolated from 313–292 Ma volcanic‐sedimentary sequences of the Dashizhai Formation. The ChRM yields a primary record of the geomagnetic field with positive fold, reversal and paleosecular variation tests. Along with published paleomagnetic data and geological constraints, we proposed a new reconstruction for the CAOB at 300 Ma. Our model posits that the Songliao‐Jiamusi and Mongolia blocks were welded into the unified Amuria block situated along the northern side of the PAO (∼34°N). On the southern side of the PAO, the Xilinhot and North China blocks were situated at equatorial paleolatitudes and were not amalgamated with Amuria until 250 Ma. This finding provides new insights into Asian paleogeography and the reconstruction of the Pangea supercontinent.