TY - JOUR
T1 - Astronomical tuning and magnetostratigraphy of the Upper Triassic Xujiahe Formation of South China and Newark Supergroup of North America
T2 - Implications for the Late Triassic time scale
AU - Li, Mingsong
AU - Zhang, Yang
AU - Huang, Chunju
AU - Ogg, James
AU - Hinnov, Linda
AU - Wang, Yongdong
AU - Zou, Zhuoyan
AU - Li, Liqin
N1 - Funding Information:
We acknowledge Junliang Ji, Shizhen Jia, Keke Ai, Xiaoping Xie, Ning Tian, Zhihao Song, and Ning Zhou for field and laboratory assistances. We thank anonymous reviewers for their specific comments and instructive suggestions. The study was co-sponsored by the National Natural Sciences Foundation of China (No. 41322013, 41572014 and 41688103), Natural Science Foundation for Distinguished Young Scholars of Hubei Province of China (2016CFA051) and the 111 Project (No. B14031 and B08030). M. Li acknowledges the China Scholarship Council (201406410029) for Ph.D. work at Johns Hopkins University, USA. Y. Zhang was supported by a Ph.D. research fellowship from the Geologic TimeScale Foundation. J. Ogg acknowledges the Overseas Distinguished Teacher Program of the Ministry of Education (MS2013ZGDZ[WH]028) for his visiting research professorship at the State Key Laboratory of Geobiology and Environmental Geology. Y. Wang acknowledges the support from the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB18000000, XDPB05) and the State Key Program of Basic Research of Ministry of Science and Technology, China (973 program, 2012CB822003). Magnetostratigraphy analyses were undertaken at (1) the Laboratory for Paleomagnetism and Environmental Magnetism, China University of Geosciences (Beijing) under the direction of Haiyan Li, and (2) the Institute of Geomechanics, Chinese Academy of Geological Sciences under the supervision of Zhiming Sun.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017/10/1
Y1 - 2017/10/1
N2 - The time scale of the Late Triassic Epoch has a divergence of age models, especially for the durations of competing definitions for its Rhaetian Stage (uppermost Triassic). The astrochronology derived from relative depth of lacustrine-bearing clastic successions and astronomically tuned geomagnetic polarity time scale (APTS) of the Newark Supergroup of eastern North America provides a basis for the Late Triassic time scale. However, the Newark APTS has been challenged regarding its age scale and completeness; therefore an independent astronomical-tuned magnetic polarity zonation is required to verify the upper Newark APTS reference scale. We compiled a 6.5 million year (myr) APTS with magnetic stratigraphy from four sections of the lacustrine-fluvial, dinosaur-track-bearing Xujiahe Formation in the Sichuan Basin of South China that also has dating from detrital zircons and regional biostratigraphy. Variations in natural gamma-ray and magnetic susceptibility that reflect variable continental weathering in the source regions of the Xujiahe Formation are paced by Milankovitch cycles, especially the 100-kyr short eccentricity and 405-kyr long eccentricity. The cycle-tuned magnetostratigraphy of the Xujiahe Formation is compared directly via the magnetic-polarity zones to the depth ranks of the Newark Supergroup that are indicative of relative depths of lacustrine facies. The Sichuan APTS indicates that there is no significant hiatus between the sedimentary succession and the basalt flows at the top of the Newark Supergroup. The Sichuan APTS is compatible with the magnetostratigraphy from the candidate Global Boundary Stratotype Section and Point (GSSP) for the Norian–Rhaetian boundary interval at the Pignola–Abriola of South Italy, but does not extend downward to the proposed GSSP in Austria associated with the longer Rhaetian option. The earliest dinosaur tracks in China are from the middle of this Xujiahe Formation, therefore are implied to be middle Rhaetian in age. This Sichuan APTS helps to resolve the controversy about the completeness and reliability of the Newark-APTS, and can be used in the future to verify if isotopic excursions in organic carbon recorded in the Italian sections that are proposed as possible secondary markers for a base-Rhaetian definition are global in nature.
AB - The time scale of the Late Triassic Epoch has a divergence of age models, especially for the durations of competing definitions for its Rhaetian Stage (uppermost Triassic). The astrochronology derived from relative depth of lacustrine-bearing clastic successions and astronomically tuned geomagnetic polarity time scale (APTS) of the Newark Supergroup of eastern North America provides a basis for the Late Triassic time scale. However, the Newark APTS has been challenged regarding its age scale and completeness; therefore an independent astronomical-tuned magnetic polarity zonation is required to verify the upper Newark APTS reference scale. We compiled a 6.5 million year (myr) APTS with magnetic stratigraphy from four sections of the lacustrine-fluvial, dinosaur-track-bearing Xujiahe Formation in the Sichuan Basin of South China that also has dating from detrital zircons and regional biostratigraphy. Variations in natural gamma-ray and magnetic susceptibility that reflect variable continental weathering in the source regions of the Xujiahe Formation are paced by Milankovitch cycles, especially the 100-kyr short eccentricity and 405-kyr long eccentricity. The cycle-tuned magnetostratigraphy of the Xujiahe Formation is compared directly via the magnetic-polarity zones to the depth ranks of the Newark Supergroup that are indicative of relative depths of lacustrine facies. The Sichuan APTS indicates that there is no significant hiatus between the sedimentary succession and the basalt flows at the top of the Newark Supergroup. The Sichuan APTS is compatible with the magnetostratigraphy from the candidate Global Boundary Stratotype Section and Point (GSSP) for the Norian–Rhaetian boundary interval at the Pignola–Abriola of South Italy, but does not extend downward to the proposed GSSP in Austria associated with the longer Rhaetian option. The earliest dinosaur tracks in China are from the middle of this Xujiahe Formation, therefore are implied to be middle Rhaetian in age. This Sichuan APTS helps to resolve the controversy about the completeness and reliability of the Newark-APTS, and can be used in the future to verify if isotopic excursions in organic carbon recorded in the Italian sections that are proposed as possible secondary markers for a base-Rhaetian definition are global in nature.
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U2 - 10.1016/j.epsl.2017.07.015
DO - 10.1016/j.epsl.2017.07.015
M3 - Article
AN - SCOPUS:85026805289
SN - 0012-821X
VL - 475
SP - 207
EP - 223
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -