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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]

To better constrain the origin and drift history of the North Qiangtang terrane (NQT), we report a well‐dated paleomagnetic pole from the Late Permian volcanics of the NQT that appears to average out secular variation. Our new results yield a paleolatitude of −7.6 ± 5.6°N at ~259 Ma for our sampling area, which confirms the NQT drifted northward during the Permian and Triassic periods. The equatorial paleolatitude of the NQT is similar to that of the coeval South China block, demonstrating that they were in close proximity. Combined with palaeontological and magmatic evidence, paleomagnetic constraints on the drift of the NQT in the Permian indicate that the NQT moved northward together with the South China block at this time. The paleolatitude evolution of the NQT implies that the NQT rifted from the northern margin of the Gondwana in the Devonian, which is earlier than the departure time of the South Qiangtang terrane. Plain Language Summary: The Tibetan Plateau is composed of several different blocks that accreted to the southern margin of Asia. There are still several unanswered questions, such as the following: Where did these blocks originate? How did these blocks accrete to Asia? How did the oceanic basin evolve? In this work, we provide robust evidence to show that the Northern Qiangtang was located at equatorial latitude (−7.6 ± 5.6°N) during the Late Permian (~259 Ma). The northward drift history together with features of the Northern Qiangtang and South China block indicates that they moved northward together during the Permian and that the Northern Qiangtang rifted from the northern margin of the Greater India margin of Gondwana during the Devonian. Key Points: The North Qiangtang terrane (NQT) was located at equatorial paleolatitude (−7.6 ± 5.6°N) during the Late Permian (~259 Ma)The NQT drifted northward together with the South China block (SCB) during the PermianThe NQT rifted from the northern margin of Gondwana during the Devonian [ABSTRACT FROM AUTHOR]

Milankovitch cycles are quasi-periodic fluctuations in insolation forced by variations in the Earth's astronomical parameters, inducing climate change, and in turn affecting sedimentation and the formation of cyclostratigraphy. Astronomical calibration of the cyclostratigraphy can be exploited as a high-resolution (0.02–0.4 Myr) astronomical time scale (ATS), facilitating the reconstruction of Earth's evolutionary history. The ATS is already an important geochronometer for the Cenozoic and Mesozoic eras, however, the ATS for the Paleozoic Era has yet to be fully constructed. Radioisotopic age-calibrated Milankovitch cycles have been detected in Paleozoic strata, linked to the hierarchy of sedimentary cycles deposited in the continental, paralic, and marine environments. The orbital eccentricity metronome (i.e., 405-kyr cycle) has already been used to construct the ATS for the timing of Paleozoic geological and climatic events. Here, we review Paleozoic cyclostratigraphy and develop a provisional ATS from published paleoclimatic proxy time series, which results in revisions to the timing of key geological events in the Paleozoic Era. [ABSTRACT FROM AUTHOR]

At the end of the Late Paleozoic Ice Age (LPIA) from late Early Permian to early Late Permian, the global climate was impacted by a prevailing megamonsoon and Gondwanan deglaciation. To better understand the abiotic and biotic responses to Milankovitch-forced climate changes during this time period, multi-element X-ray fluorescence (XRF) geochemistry analyses were conducted on 948 samples from the late Early−late Middle Permian Maokou Formation at Shangsi, South China. The Fe/Ti, S/Ti, Ba/Ti and Ca time series, which were calibrated with an existing “floating” astronomical time scale (ATS), show the entire suite of Milankovitch rhythms including 405 kyr long eccentricity, 128 and 95 kyr short eccentricity, 33 kyr obliquity and 20 kyr precession. Spectral coherency and cross-phase analysis reveals that chemical weathering (monitored by Fe/Ti) and upwelling (captured by S/Ti and Ba/Ti) are nearly antiphase in the precession band, which suggests a contrast between summer and winter monsoon intensities. Strong obliquity signal in the Ba/Ti series is proposed to derive from changes in thermohaline circulation intensity from glaciation dynamics in southern Gondwana. The abundance of foraminifer, brachiopod and ostracod faunas within the Maokou Formation were mainly controlled by the ~1.1 Myr obliquity modulation cycle. The obliquity-forced high-nutrient and oxygen-depleted conditions generally produced a benthic foraminifer bloom, but threatened the brachiopod and ostracod faunas. [ABSTRACT FROM AUTHOR]

Termination of the late Paleozoic icehouse (LPI) serves as the Earth's first icehouse-to-greenhouse transition when the continents were covered by extensive vegetation. However, low-latitude climatic and biological responses to this climate transition remain unclear. In this study, we conducted a cyclostratigraphic analysis of a shallow marine succession of the Tieqiao section in South China. Variations in gamma rays that reflect continental weathering strength in the source regions are paced by Milankovitch cycles, including 405-kyr long eccentricity, 31.7-kyr obliquity, and ∼ 20-kyr (20.1 kyr and 18.7 kyr) precession. Based on the 405-kyr-scale cyclostratigraphic correlation between the Tieqiao section and the deep marine succession of Naqing, a floating astronomical time scale for the late Early Permian was constructed, and the base of the Kungurian stage was estimated as 284.83 ± 0.40 Ma. Climatic and astronomical variations were synchronized to this refined timescale and further compared with a geochronologically independent marine invertebrate biodiversity time series to interpret the dynamics of marine biological evolution during the late Paleozoic icehouse-to-greenhouse transition. The impacts of low-frequency obliquity forcing (with a period of ∼1.35 Myr) on climatic and biotic systems have differentiated in the changing climate backgrounds. When Gondwana land was minimally glaciated during the Artinskian, increased marine speciation was associated with elevated climatic humidity, nutrient inputs, linkage to glacial building at low-amplitude obliquity oscillation intervals (obliquity nodes). This cause-and-effect relationship gradually changed from ∼285.1 Ma, along with the termination of Gondwanan glaciation and tropical aridification over the long term. In an arid greenhouse, continental aridity and marine transgression at obliquity nodes led to a low nutrient level that the suppressed marine biodiversity. Our results show differential dynamics involving the Earth's astronomical parameters, climate change, and marine invertebrate biodiversity between icehouse and greenhouse conditions in the late Paleozoic Era. • The constructed astronomical time scale yields an age for the basal Kungurian stage of 284.83 ± 0.40 Ma. • Obliquity nodes led to climate humidity and marine speciation during the partially glaciated period. • Obliquity nodes led to aridity, marine transgression and reduced biodiversity in an ice-free world. [ABSTRACT FROM AUTHOR]

In their comment, Smith et al. (2016) discount the astronomical cycle identifications made from Middle Permian cyclostratigraphy in our recent paper (Fang et al. 2015), declaring that we presented defective null models and improper hypothesis tests, and greatly overestimated the statistical significance of cycles. Here we respond in detail to clarify the decisions that were made in our work, and to correct errors and omissions and other misunderstandings arising in their comment. We also discuss the advent of objective methodologies that promise to improve research in cyclostratigraphy in the near future. [ABSTRACT FROM AUTHOR]

High-resolution (948 samples) measurements of anhysteretic remanent magnetization (ARM) were performed on the ~ 200 m thick Early–Middle Permian Maokou Formation of the Shangsi section, South China. The ARM variations are quasi-periodic and the wavelengths of significant cycles collectively present a ratio of 20:5:2:1 throughout the formation, corresponding to long orbital eccentricity, short orbital eccentricity, obliquity, and precession cycles. A strong obliquity (44 and 33 kyr) signal suggests that waning and waxing of the ice sheet in eastern Australia at the end of the Late Paleozoic Ice Age (LPIA) exerted a significant influence on global climate and sea level. A “floating” astronomical time scale (ATS) is developed using the 405 kyr orbital eccentricity cycle as an astronomical calibration target. This results in estimation of the Roadian and Wordian stages duration as 3.7 ± 0.4 myr and 2.9 ± 0.4 myr, respectively. Prominent ~ 2 myr cycles likely originated from Earth and Mars secular frequencies g 4 –g 3 , and ~ 1 myr cycles from s 4 –s 3 . These periodicities are shorter than those observed in the Cenozoic Era, which may be due to the chaotic behavior of the planets, but still reflecting 2:1 secular resonance between Earth and Mars. Third-order eustatic sequences are linked to the s 4 –s 3 obliquity term, which suggests a glacioeustatic controlling mechanism during this transitional stage from Paleozoic icehouse to Mesozoic greenhouse. [ABSTRACT FROM AUTHOR]

Late Paleozoic deglaciation is Earth's first icehouse-to-greenhouse transition with extensive vegetation, but the response of tropical climate to this transition has not yet been fully addressed. Here, cyclostratigraphic analysis was conducted on the magnetic susceptibility (MS) record of a deep marine carbonate succession in South China to construct the astrochronology of late Cisuralian (Early Permian), and decipher the evolutionary response to the climate transition in the MS and δ13C carb time series. The constructed astronomical time scale indicates an age of 272.83 ± 0.2 Ma for the Cisuralian–Guadalupian boundary in South China. Synchronizing global records demonstrates a complicated linkage between low and high latitudes, involving secular changes in atmospheric p CO 2 , ice volume, tropical climate and carbon cycling. In the final stage of the Early Permian icehouse (~290–288.2 Ma), the delivery of moisture from low to high latitudes was reduced in comparison with that in the icehouse apex. A more humid climate facilitated the development of tropical coal forests and more storage of 12C on land. In a full greenhouse condition (~281–272 Ma), the tropical responses to a rise in atmospheric p CO 2 involved continental drying and ocean stagnation. On a shorter time scale, the nodes of 1.36 Myr obliquity cycles triggered ice-sheet expansion and enhanced tropical precipitation during an icehouse condition. With the gradual transition to an arid greenhouse, the insolation-climate relationship began to change at ~285.1 Ma, and the obliquity nodes became associated instead with terrestrial aridity and marine anoxia. These results bring into a focus pattern of shifting dynamics involving Earth's astronomical parameters and climate change for icehouse and greenhouse worlds in the Late Paleozoic Era. • The Cisuralian–Guadalupian boundary were dated as 272.83 ± 0.2 Ma. • Obliquity nodes triggered ice sheet expansion and enhanced tropical precipitation during a subhumid icehouse (290–285.1 Ma). • Obliquity nodes resulted in the terrestrial aridity and marine anoxia during an arid greenhouse (285.1–272 Ma). [ABSTRACT FROM AUTHOR]

The Late Paleozoic Ice Age (LPIA) was the longest-lasting icehouse in the Phanerozoic. Previous studies indicated a climate warming interval in the earliest Permian—an apex of the LPIA. To better understand hydroclimatic changes and carbon cycling within this time interval, we conducted a series of high-resolution geochemical and rock magnetic analyses, including magnetic measurements (e.g., magnetic susceptibility, anhysteretic remanent magnetization, hysteresis loops, temperature-dependent susceptibility), ratio of iron to potassium (Fe/K), and carbonate carbon isotope (δ13C carb) from a deep-marine section in South China. Calibrated to the published astronomical time scale, a negative δ13C carb excursion (−1‰) was identified during 298.4–297.9 Ma, and it was time-equivalent with the warming interval, recognized by a decrease in conodont apatite oxygen isotopes in South China, low-latitude sea-level transgression, and high-latitude deglaciation. The negative δ13C carb excursion also coincided with a magmatic pulse of the Skagerrak-Centered Large Igneous Province (LIP), indicating that the perturbation in carbon cycling is likely associated with the release of volcanic CO 2. Furthermore, cyclostratigraphic analysis on multiple paleoclimatic proxies, including ferrimagnetic susceptibility, gamma-ray, and Fe/K, suggested that the negative excursion of δ13C carb also overlapped with the maximum of the eccentricity cycle. It implied that orbital configurations may amplify the feedback of the LIP, causing this short-term warming interval. • High-resolution carbon isotope and magnetic record in the earliest Permian. • Transient climate warming interval is documented in the earliest Permian. • LIP and orbital forcing were critical drivers of the earliest Permian warming. [ABSTRACT FROM AUTHOR]