TY - JOUR
T1 - Cycle-calibrated magnetostratigraphy of middle Carnian from South China
T2 - Implications for Late Triassic time scale and termination of the Yangtze Platform
AU - Zhang, Yang
AU - Li, Mingsong
AU - Ogg, James G.
AU - Montgomery, Paul
AU - Huang, Chunju
AU - Chen, Zhong Qiang
AU - Shi, Zhiqiang
AU - Enos, Paul
AU - Lehrmann, Daniel J.
N1 - Funding Information:
We are grateful to the late Heinz Kozur for his detailed education on the mid-Carnian “Wet Intermezzo” and its global implications, and to Marco Franceschi (Univ. Padova, Italy) for a Dolomites stratigraphy field excursion and discussions. Field work was assisted by Zhihao Song, Xueqian Feng and Steve Grasby in Guizhou and by XiongDuan and Yixing Du in Sichuan. Magnetostratigraphy analyses were undertaken at the Black Mountain paleomagnetism laboratory (Australian National University) inCanberra under the patient guidance of David Heslop and Xiang Zhao, and Y.Z.'s stay was funded by the Geologic TimeScale Foundation (USA) . Gabi Ogg prepared the time-scale graphics from her diagrams for the GTS2012 volumes and from output from TimeScale Creator ( www.tscreator.org ). Support for J.O. was from a visiting professorship at the State Key Laboratory of Geobiology and Environmental Geology funded by the Overseas Distinguished Teacher Program of the Ministry of Education ( MS2013ZGDZ[WH]028 ), and as a visiting-scholar sabbatical hosted by the Geosciences Australia (Canberra). Funding for field work, graduate-student support, and international travel costs for Y.Z. and M.L. are from the National Natural Science Foundation of China (nos. 41322013 , 41272023 , 41272131 ), the Program for New Century Excellent Talents in University ( NCET-11-0723 ), the Program of Introducing Talents of Discipline to Universities (no. B14031 ), the China Scholarship Council , and the National Key Basic Research Development Program of China ( 2012CB822003 ). ZQC's work is supported by the 973 Program of China ( 2011CB808800 ), the 111 Program of China ( B08030 ), and research grants from the State Key Laboratory of Geobiology and Environmental Geology ( GBL11206 ).
Publisher Copyright:
© 2015 Elsevier B.V.
PY - 2015/10/5
Y1 - 2015/10/5
N2 - Thick successions from the margins of the Triassic Yangtze Platform of the South China Block record a transition from carbonate-rich facies (Zhuganpo Formation and equivalents) to clastic-rich facies (Xiaowa Formation and equivalents) during the Carnian (early Late Triassic) that mark the final phase of termination of this long-lived platform. Cyclostratigraphy derived from spectral gamma-ray (SGR) intensity curves was combined with magnetostratigraphy of two sections in Guizhou Province (Wayao transect and its upward extension into the Geopark Wayao in Guanling county and the Laishike section in Zhenfeng county) and one location in Sichuan Province (Hanwang section). The cyclostratigraphy from all the Guizhou sections indicates a persistent suite of ca. 34. m, 9. m and 1.8. m. cycles, which are consistent with the ratios of orbital-climate oscillations caused by long-eccentricity (405. kyr), short-eccentricity (~. 100. kyr) and precession (20. kyr). The magnetostratigraphy of all sections is consistent with the cyclicity and characteristic SGR features, thereby enabling a cycle-tuned magnetic polarity scale spanning ~. 2.4. myr. The main feature is a 1.3-myr interval of reversed polarity containing brief normal-polarity subchrons, and this reversed-polarity chron appears to correspond to the significant reversed-polarity-dominated interval spanning the upper half of the Trachyceras aonoides through the lower half of the Austrotrachyceras austriacum ammonoid zones of the upper Julian (the lower substage of Carnian). This magnetostratigraphic correlation implies that the termination of the Yangtze Platform is coeval with the beginning of the mid-Carnian episode of climatic disruption in Europe, which is locally called the "Carnian Pluvial Event" or "Wet Intermezzo", and with the temporary cessation of the platform carbonates in the Dolomites. The cycle-scaled magnetic-polarity time scale supports the "Short-Tuvalian/Long-Norian" age model of the Late Triassic in which the base of the cycle-tuned polarity pattern from the Newark Group of eastern North America is younger than the end of the Julian substage.
AB - Thick successions from the margins of the Triassic Yangtze Platform of the South China Block record a transition from carbonate-rich facies (Zhuganpo Formation and equivalents) to clastic-rich facies (Xiaowa Formation and equivalents) during the Carnian (early Late Triassic) that mark the final phase of termination of this long-lived platform. Cyclostratigraphy derived from spectral gamma-ray (SGR) intensity curves was combined with magnetostratigraphy of two sections in Guizhou Province (Wayao transect and its upward extension into the Geopark Wayao in Guanling county and the Laishike section in Zhenfeng county) and one location in Sichuan Province (Hanwang section). The cyclostratigraphy from all the Guizhou sections indicates a persistent suite of ca. 34. m, 9. m and 1.8. m. cycles, which are consistent with the ratios of orbital-climate oscillations caused by long-eccentricity (405. kyr), short-eccentricity (~. 100. kyr) and precession (20. kyr). The magnetostratigraphy of all sections is consistent with the cyclicity and characteristic SGR features, thereby enabling a cycle-tuned magnetic polarity scale spanning ~. 2.4. myr. The main feature is a 1.3-myr interval of reversed polarity containing brief normal-polarity subchrons, and this reversed-polarity chron appears to correspond to the significant reversed-polarity-dominated interval spanning the upper half of the Trachyceras aonoides through the lower half of the Austrotrachyceras austriacum ammonoid zones of the upper Julian (the lower substage of Carnian). This magnetostratigraphic correlation implies that the termination of the Yangtze Platform is coeval with the beginning of the mid-Carnian episode of climatic disruption in Europe, which is locally called the "Carnian Pluvial Event" or "Wet Intermezzo", and with the temporary cessation of the platform carbonates in the Dolomites. The cycle-scaled magnetic-polarity time scale supports the "Short-Tuvalian/Long-Norian" age model of the Late Triassic in which the base of the cycle-tuned polarity pattern from the Newark Group of eastern North America is younger than the end of the Julian substage.
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U2 - 10.1016/j.palaeo.2015.05.033
DO - 10.1016/j.palaeo.2015.05.033
M3 - Article
AN - SCOPUS:84937806024
SN - 0031-0182
VL - 436
SP - 135
EP - 166
JO - Palaeogeography, Palaeoclimatology, Palaeoecology
JF - Palaeogeography, Palaeoclimatology, Palaeoecology
ER -