Wu_G45461 1st pages Wu_G45461 1st pages https://doi.org/10.1130/G45461.1 Manuscript received 7 August 2018 Revised manuscript received 20 November 2018 Manuscript accepted 20 November 2018 © 2018 Geological Society of America. For permission to copy, contact [email protected]. Published online XX Month 2018 An ~34 m.y. astronomical time scale for the uppermost Mississippian through Pennsylvanian of the Carboniferous System of the Paleo-Tethyan realm Huaichun Wu1,2,*, Qiang Fang1,2, Xiangdong Wang3,4, Linda A. Hinnov5, Yuping Qi4, Shu-zhong Shen3,4, Tianshui Yang1, Haiyan Li1, Jitao Chen4, and Shihong Zhang1 1State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China 2School of Ocean Sciences, China University of Geosciences, Beijing 100083, China 3Centre for Research and Education on Biological Evolution and Environment, Nanjing University, Nanjing 210023, China 4State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China 5Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, Virginia 22030, USA ABSTRACT Time Scale 2016 (GTS2016; Ogg et al., 2016). However, the inferred The Naqing section in South China is a representative carbonate Carboniferous chronostratigraphic framework needs further improve- slope succession in the eastern Paleo-Tethyan realm. It encompasses ment, because: (1) the pan-Euramerican framework cannot be applied at a four global stratotype section and point (GSSP) candidates for the Car- global scale through conodont or fusulinid biozone correlation due to bio- boniferous Period. High-resolution magnetic susceptibility measure- diachronism and provincialism (Davydov et al., 2012); (2) astronomically ments through the section have variations that correlate with lithologi- forced sedimentary cycles from other continents are required to affirm cal cycles of lime mudstone, wackestone, and packstone. Astronomical the widespread pan-Euramerican cyclothems related to orbital eccentric- calibration of ~3 m sedimentary cycles to a 405 k.y. orbital eccentricity ity forcing (Heckel, 2008); and (3) inconclusive stage-boundary markers cycle period aligns other significant, shorter sedimentary cycles to lead to variable durations for the Carboniferous stages (Ogg et al., 2016). periods recognizable as short orbital eccentricity (136 k.y., 122 k.y., Quantitative biostratigraphic calibration that is separate from the pan- and 96 k.y.), obliquity (31 k.y.), and precession (22.9 k.y. and 19.7 k.y.). Euramerica region needs to be investigated in order to improve Carbonifer- The orbital eccentricity has long-period modulations with 2.4 m.y., 1.6 ous chronology. A near-continuously deposited, carbonate slope succession m.y., and 1.2 m.y. periods, and the obliquity has a 1.2 m.y. modulation at Naqing in South China constitutes an excellent stratigraphic standard for cycle. The astronomical calibration indicates durations of 7.6 m.y., 8.1 the marine Carboniferous in the Paleo-Tethyan realm. Four global strato- m.y., 8.5 m.y., 2.87 m.y., and 4.83 m.y. for the Serpukhovian, Bashkirian, type section and point (GSSP) candidates for the Carboniferous stages have Moscovian, Kasimovian, and Gzhelian Stages, respectively. The cali- been proposed in this section, including Visean/Serpukhovian, Bashkirian/ brated durations of the 25 conodont zones collectively indicate a 33.9 Moscovian, Moscovian/Kasimovian, and Kasimovian/Gzhelian boundaries m.y. time scale. Biochronological correlation of the Paleo-Tethyan and (Ueno and Task Group, 2009; Richards and Task Group, 2010; Qi et al., pan-Euramerican records significantly refines the global chronostratig- 2012, 2016). Here, we present a detailed cyclostratigraphic study using raphy for the Serpukhovian Stage and the Pennsylvanian subsystem. magnetic susceptibility (MS) measurements of the Naqing section and This new Paleo-Tethyan astronomical time scale opens a new window propose a 33.9 m.y. astronomical time scale (ATS) for the Serpukhovian for understanding the late Paleozoic icehouse world. Stage and the stages of the Pennsylvanian subsystem. INTRODUCTION DATA AND METHODS The Carboniferous Period is a key interval in the evolution of the The South China Block (SCB) was located in an equatorial region Earth system, characterized by major tectonic (Torsvik and Cocks, 2004), adjacent to the eastern Paleo-Tethys Ocean during the Carboniferous climatic (Montañez and Poulsen, 2013), and biotic (Wang et al., 2013) (Fig. 1A). The studied ~250-m-thick Carboniferous section at Naqing events. Reconstruction of the sequence of geological events for the period (25°15′3.9″N, 106°29′6.9″E) in the Guizhou Province includes the Shan- requires an accurate global chronostratigraphic framework. The age model gruya and Nandan Formations, which were deposited in the Qian-Gui for the Carboniferous in the Geologic Time Scale 2012 (GTS2012; Davy- Basin in the southwestern part of the SCB (Figs. 1B and 1C; Fig. DR1 dov et al., 2012) was derived from 405-k.y.-calibrated cyclothems and in the GSA Data Repository1). The lithology is mainly composed of gray, constrained optimization (CONOP) for scaling biozones relative to their thin- to medium-bedded lime mudstone, wackestone, and packstone sediment thicknesses, mostly from pan-Euramerican records. Recently, the intermittently intercalated with chert, which were deposited in a carbonate Pennsylvanian age model for pan-Euramerican successions was revised slope environment without evident hiatuses (Chen et al., 2018; Fig. 1C). using an astronomical calibration of major cyclothems in the Geologic 1 GSA Data Repository item 2019036, additional details of paleoclimatic and *E-mail: [email protected] paleoenvironmental proxies, time series analysis methods, amplitude modulations CITATION: Wu, H., et al., 2018, An ~34 m.y. astronomical time scale for the of the astronomical parameters, Figures DR1–DR7, and Tables DR1–DR3, is uppermost Mississippian through Pennsylvanian of the Carboniferous System of available online at http://www.geosociety.org/datarepository/2019/, or on request the Paleo-Tethyan realm: Geology, v. 47, p. 1–4, https://doi.org/10.1130/G45461.1 from [email protected]. Geological Society of America | GEOLOGY | Volume 47 | Number 1 | www.gsapubs.org 1 Wu_G45461 1st pages Wu_G45461 1st pages Figure 1. A: Carboniferous paleogeographic map showing location of 104°E 107°E South China (ca. 300 Ma). Base map is modified from Ron Blakey (http:// A B Guiyang Duyun Panthalassic UralianSiberia Seawa jan.ucc.nau.edu/~rcb7). B: Paleogeographic map of Guizhou Prov- Ocean South China Block Anshun 26°N y Qian-Gui Basin ince and adjacent area, modified from Jiao et al. (2003). C: Lithology, Mid-continent Basin biostratigraphy, and cyclostratigraphy of Naqing section. Conodont Donets Basin Paleo-Te Qujing S. Urals Ocean zones are after Hu (2016). Interpreted 405 k.y. orbital eccentricity cycles thys Naqing (E; red curve) were extracted using a Gaussian filter with pass-bands Gondwana Land Paralic facies 0 40 km of 0.25 ± 0.13 cycles/m for 0–94.8 m, 0.4 ± 0.14 cycles/m for 94.8–159.75 Platform Slope Basin m, 0.3 ± 0.12 cycles/m for 159.75–224.4 m, and 0.4 ± 0.16 cycles/m for 224.4–249.55 m, respectively. M—lime mudstone; W—wackestone; F— h C Magnetic fine-grained packstone; C—coarse-grained packstone. Conodont susceptibility (in log) poc Depth (m) E Stage zone Lithology -9 -8 -7 E84 Streptognathodus The basal Serpukhovian, Bashkirian, Moscovian, Kasimovian, Gzhelian, Formation wabaunsensis E82 n 240 Streptognathodus E80 and Asselian Stages at Naqing have been defined as the first appearance tenuialveus datum (FAD) of Lochriea ziegleri at 17.92 m, Declinognathodus nodu- Streptognathodus E78 230 virgilicus E76 liferus sensu lato at 91.4 m, Diplognathodus ellesmerensis at 138.15 m, Gzhelia Idiognathodus E74 nashuiensis Idiognathodus turbatus at 200.08 m, I. simulator at 220.33 m, and Strep- 220 Idiognathodus E72 simulator tognathodus isolatus at 249.52 m, respectively (Qi et al., 2012, 2014; Hu Streptognathodus E70 210 zethus E68 Late Pennsylvanian and Qi, 2017; Hu, 2016; Fig. 1; Fig. DR2 and Table DR1). Kasimo -vian Idiognathodus E66 A high-resolution MS record with 4992 samples, collected at a spac- 200 eudoraensis Idiognathodus E64 ing of 5 cm, is presented for the upper Visean to uppermost Gzhelian guizhouensis E62 190 Idiognathodus Stages (Table DR2). Cyclostratigraphic analysis involves identification of magnificus E60 180 Idiognathodus astronomical frequencies in sedimentary records to construct precise time turbatus E58 scales (Hinnov, 2013). The 2 multitaper method (MTM) spectral analysis Swadelina π 170 makhlinae E56 (Thomson, 1982) was applied with classical red noise modeling reported at Nandan Swadelina E54 Moscovian subexcelsa 160 E52 85%, 90%, 95%, and 99% confidence levels. The evolutionary fast Fourier Idiognathodus podolskensis E50 transform (FFT) spectrogram was computed to identify the changes in 150 Middle Pennsylvanian Mesogondolella E48 donbassica cycle frequencies due to variable sedimentation rates. The MTM and FFT - Mesogondolella E46 analyses use MATLAB scripts available at http://mason.gmu.edu/ ~lhin- 140 clarki E44 Diplognathodus E42 nov/cyclostratigraphytools.html. The interpreted astronomical signals were 130 ellesmerensis E40 “Streptognathodus” E38 extracted with Gaussian band-pass filters in