New Middle–Late Permian Paleomagnetic and Geochronological Results From Inner Mongolia and their Paleogeographic Implications

Abstract

A combined paleomagnetic and geochronological study was conducted on the red beds of the Zhesi Formation (ZSF) in the Xilinhot–Songliao Block (XSB) and the andesites and sandstones of the Qingfengshan Formation (QFF) in the North China Block (NCB). The ZSF tuffs and the QFF andesites were dated to 265.3 ± 1.8 Ma and 254.8–257.1 Ma, respectively, using the zircon U–Pb laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) method. A total of 246 paleomagnetic samples were subjected to stepwise thermal demagnetization. After removal of the low‐temperature viscous components acquired in the recent geomagnetic field, stable high‐temperature components (HTCs) were isolated from most samples. The HTC of the ZSF passed a fold test, and the HTC of the QFF passed both fold and reversal tests, indicating their primary origins. The corresponding paleomagnetic poles are 57.4°N/342.0°E (A95 = 4.3°) for the XSB at ~265 Ma and 54.3°N/20.2°E (A95 = 3.3°) for the NCB at ~255 Ma. Comparison of high‐quality Permian paleomagnetic poles of the XSB and NCB reveals a latitudinal convergence and relative rotation between them that led to a scissors‐like closure of the Solonker Ocean from west to east between ~265 and ~246 Ma, which controlled the mixing of the Cathaysian and Angara floras in space and time. The XSB and NCB moved rapidly northward between ~265 and ~255 Ma, which probably accelerated the end‐Guadalupian mass extinction in East Asia.

New Early Permian Paleomagnetic and Geochronological Data From the Xilinhot–Songliao Block and Their Implications for the Relationship Between the Paleo‐Asian Ocean and the Paleo‐Tethys Ocean

“…Domeier and Torsvik (2014). The East Asian blocks are mostly shown according to paleomagnetic constraints (this study and Ren et al, 2020). Distributions of flora and fauna are based on C. Wang et al (2014), X.…”

“…265 Ma; Y. Liu et al, 2017;Ren et al, 2020;Xiao et al, 2018). We speculate that this limited ocean basin was formed by the westward movement of the NCB (Figure 4a) accompanied by its southward movement (Figure 3b).…”

“…For the published paleomagnetic data, most researchers used a blanket flattening factor (f = 0.6) to correct the inclination of the clastic rocks (e.g., Torsvik et al, 2012;Van der Voo et al, 2015). This blanket correction is supported by the recent investigations of the lower Triassic red beds of the Liujiagou Formation (T. Zhou, Huang, et al, 2018) and the ∼255 Ma volcanic rocks of the Qingfengshan Formation (Ren et al, 2020). In this study, the published data from clastic rocks are corrected with an optimal flattening factor, f, of 0.6 (Table S1 in Supporting Information S1).…”

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

“…In the Suolun area, we collected eight sites (84 specimens) from the sandstones of the Linxi Formation (Figures 1b,2 and Figure S1d in Supporting Information S1). All cores were drilled using a portable paleomagnetic drill and oriented using magnetic and/or sun compass (Table 1 and Table S2 , 1991 andRen et al, 2020). The Permian geomagnetic polarity time scale is adopted from Hounslow and Balabanov (2016).…”

“…Figure 2. Stratigraphic sequences of the Ulanhot area (Modified after IMBGMR, 1991 andRen et al, 2020). The Permian geomagnetic polarity time scale is adopted fromHounslow and Balabanov (2016).…”