High‐Resolution Floating Point Time Scale (FPTS) of the Permian Capitanian Stage in South China

• Published in: Chinese journal of geophysics 2015-11, Vol.58 (6), p.611-627
• Main Authors: Wu‐Qiang, XUE, Bo, LI, Jia‐Xin, YAN, Ellwood, Brooks B., Tomkin, Jonathan H., Yan, WANG, Zong‐Min, ZHU
• Format: Article
• Language: English
• Subjects: Age; Boundaries; Capitanian; Cherts; China; Conodont; Datasets; Diamagnetism; Emeishan large igneous province; Floating point time scale (FPTS); Fourier transforms; Geophysics; Magnetic permeability; Magnetic susceptibility (MS); Time; Time‐series analysis
• ISSN: 0898-9591; 2326-0440
• DOI: 10.1002/cjg2.20199

Here we present a magnetic susceptibility (χ) dataset from the Permian Capitanian strata exposed in the Tieqiao section, Laibin area, South China, a supplementary reference section for the Guadalupian‐Lopingian (Middle‐Upper Permian) Global Boundary Stratotype Section and Point (GSSP). The succession consists of alternating thin‐bedded chert with micritic limestone of basinal and slope facies, with a carbonate cap indicating shallow‐water platform deposition. χ datasets, which are mostly negative (diamagnetic), suggest that the Laibin area was isolated from terrigenous sources during most of the Capitanian. A sudden increase in the χ signal just below the Guadalupian‐Lopingian (G‐L) boundary is recorded. Although regression at the terminal Capitanian might have contributed to the increase, the coincidence of the increase with the onset of the Emeishan Large Igneous Province (LIP) eruptions demonstrate pronounced volcanic effects controlling χ in this part of the section. χ and thermomagnetic susceptibility measurements indicate that the dominant magnetic constituents in this study are diamagnetic calcite and chert, with subordinate paramagnetic and ferrimagnetic minerals, derived from eolian and volcanic sources, and producing the cyclicity observed in the dataset. Spectral (time‐series) analyses of χ data were performed using Multi Taper Method (MTM) and Fourier Transform (FT) analysis. Five frequencies that are consistent with Milankovitch‐band orbital forcing were compared to the dataset: eccentricity E1 and E2 (100 and 405 ka, respectively), obliquity O2 (44.10 ka), and precession P1 (17.70 ka) and P2 (20.95 ka). Interpretation of these results indicates that the duration for the Capitanian in the Tieqiao section was ∼3.85 Ma. Likewise, the mean sediment accumulation rate (SAR) for the whole Capitanian was ∼2.91 cm·ka−1. In addition, graphic comparison of the Tieqiao χ data to a floating point time scale for Upper Wordian through Capitanian time allows estimates of the duration for conodont zones identified from the section; these ranging from 26.6 ka to 2.3 Ma before extinction of individual conodont species. Therefore, timing of the onset age of Emeishan LIP eruptions is estimated to yield an age of 262.7 Ma, with placement of these eruptions at 1.4 Ma below the G‐L boundary.