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The timing of formation of the Hegenshan suture is crucial to understanding the evolution of the Central Asian Orogenic Belt (CAOB). Here we present a well‐dated paleomagnetic pole (103 samples from 15 sites, 36.7°N/29.2°E, A95 = 3.3°) that passed a positive fold test, a reversal test, and a conglomerate test from the ∼250 Ma upper Gunbayn Formation andesites in the southeastern Mongolia Block (MOB). The high‐quality paleomagnetic database may demonstrate that the MOB drifted rapidly southward and collided with the Xilinhot–Songliao Block between 256 and 250 Ma, resulting in the closure of the Hegenshan Ocean at ∼250 Ma. The Hegenshan suture and the Solonker suture were formed almost simultaneously and marked the final closure of the Paleo‐Asian Ocean. Plain Language Summary: The Central Asian Orogenic Belt (CAOB) is the largest accretionary orogenic belt on earth since begin of the Phanerozoic. Since the Late Paleozoic, two prominent sutures, namely the Hegenshan and Solonker sutures, have played crucial roles in the tectonic evolution of the eastern CAOB, as they were associated with the closure of the Paleo‐Asian Ocean (PAO). The timing of the formation of the Hegenshan suture, however, remains ambiguous due to the lack of reliable paleomagnetic data. In this study, we present accurately dated paleomagnetic constraints on the paleogeographic position of the Mongolia Block (MOB), located on the northern side of the Hegenshan suture, at ∼250 Ma. By combining high‐quality Late Permian–Early Triassic paleomagnetic data with geological evidence, we propose a new reconstruction that suggests the near‐simultaneous closure of both the Hegenshan and Solonker oceans around 250 Ma. This significant event marks the final disappearance of the PAO and represents a fundamental stage in the establishment of the tectonic framework of the eastern CAOB at that time. Key Points: We report a well‐dated ∼250 Ma paleomagnetic pole from the Mongolia BlockThe closure of both the Hegenshan and Solonker oceans at ∼250 Ma marked the final disappearance of the Paleo‐Asian Ocean [ABSTRACT FROM AUTHOR]

The paleogeographic position of the Xilinhot–Songliao Block (XSB) is crucial to understand the spatiotemporal relationship between the Paleo‐Asian Ocean (PAO) and East Paleo‐Tethys Ocean (EPTO) tectonic domains. However, the lack of robust early Permian paleomagnetic data in the XSB has led to uncertainty in its paleogeographic position. Here, we report a well‐dated (286.1–281.25 Ma) paleomagnetic pole (38.4°N/17.6°E, A95 = 4.0°) from andesites of the Dashizhai Formation in the XSB. We combined our paleomagnetic data with available geological and paleontological data to reconstruct the paleogeographic relationship between the PAO and EPTO. The XSB was located on the northern margin of the EPTO at ∼285 Ma, suggesting that the northern boundary of the EPTO tectonic domain extended to the southern margin of the XSB, the Hegenshan Ocean (between the XSB and the Mongolia Block) corresponds to the eastern PAO, and the XSB separated the eastern PAO and EPTO at ∼285 Ma. Plain Language Summary: The evolution of the Paleo‐Asian Ocean (PAO) and the East Paleo‐Tethys Ocean (EPTO) tectonic domains constructed the late Paleozoic paleogeographic pattern of Central and East Asia. Due to contradictions between the tectonic paleogeography and paleobiogeography of the Xilinhot–Songliao Block (XSB) during the early Permian, the spatiotemporal relationship between the two tectonic domains has been unclear. In this study, we present well‐dated paleomagnetic constraints on the paleogeographic position of the XSB at ca. 285 Ma. We provide a new reconstruction for the Northeast Asian block, which suggests that the XSB was located between the eastern PAO and the EPTO during that time and was the intermediate unit that separated the two tectonic domains. Key Points: The Xilinhot–Songliao Block (XSB) was located at ∼19.3°N on the northern margin of the East Paleo‐Tethys Ocean (EPTO) at 285 MaThe northern boundary of the EPTO tectonic domain extended to the southern margin of the XSBThe Hegenshan Ocean between the XSB and Mongolia Block was the main ocean basin of the eastern Paleo‐Asian Ocean at 285 Ma [ABSTRACT FROM AUTHOR]

The Cryogenian nonglacial epoch (CNE) spans from the termination of the Sturtian snowball Earth (ca. 659 Ma) to the initiation of the Marinoan snowball Earth (ca. 649.2 Ma). The carbonate sequences formed in low latitudes record paleoclimatic and paleoceanographic changes during the CNE. Three negative carbon isotope (δ13C) excursions, named Rasthof, Tayshir and Trezona, are present at the bottom, middle, and top of the carbonate sequences, bracketing two intervals with highly positive δ13C values. Uranium isotope (δ238U) data from Mongolia reveal ocean redox changes linked to δ13C variations during the CNE, marked by the development of anoxic deep ocean to extensive oxygenation and subsequent deoxygenation. However, the timing and duration of these paleoceanographic events and δ13C excursions have not been adequately investigated. Here, we report new environmental magnetic results of the higher paleo-latitudinal, siliciclastic-dominated Datangpo Formation (Fm) in South China that may help constrain the age and correlation of the CNE geochemical events. We identified four segments of the Datangpo Fm based on the magnetic susceptibility (MS) profile and other environmental magnetic parameters, which are, in ascending order, the ascent segment (Da), lower stable-segment (Db), transition segment (Dc), and upper stable-segment (Dd). These segments are dated by the astronomical time scale as 659–655.6 Ma (Da), 655.6–653.3 Ma (Db), 653.3–652.3 Ma (Dc), and 652.3–649.2 Ma (Dd). Environmental magnetism analyses show that the highest magnetite concentration but lowest fine-grained magnetite contents are present in "Da", followed by "Dd" and "Db". These results suggest a sea-level fall and a potential decrease in oxygenation after the deposition of the transition segment (Dc), implying that a cooling climate started ∼4 Myr before the Nantuo glaciation (Marinoan snowball Earth). Ocean redox variations revealed by environmental magnetism in the Datangpo Fm are consistent with those reported from the low-latitudinal carbonate sequences. "Da" likely corresponds to the Rasthof δ13C excursion and "Dc" corresponds to the Tayshir δ 13C excursion; whereas "Db" and "Dd" probably correspond to the two intervals with positive δ 13C values. • Four segments of the Cryogenian nonglaciatial epoch in South China are identified and the time of each segment is constrained. • Environmental magnetism analyses show a climate cooling ∼4 Myr before the Nantuo glaciation (or Marinoan snowball Earth). • Siliciclastic depositions in South China are linked to carbonate depositions in low-latitude continents. [ABSTRACT FROM AUTHOR]