沉积学报  2018, Vol. 36 Issue (2): 267−279

扩展功能

文章信息

白玛曲宗, 韦恒叶, 江增光, 邱振
BAI MaQuZong, WEI HengYe, JIANG ZengGuang, QIU Zhen
江西东岭剖面P-T界线碳同位素变化与沉积物输入的关系
The Relationship between Carbon Isotopic Changes and the Sediments Supply at the P-T Boundary in Dongling Section, Jiangxi Province
沉积学报, 2018, 36(2): 267-279
ACTA SEDIMENTOLOGICA SINCA, 2018, 36(2): 267-279
10.14027/j.issn.1000-0550.2018.028

文章历史

收稿日期:2017-01-09
收修改稿日期: 2017-06-01
江西东岭剖面P-T界线碳同位素变化与沉积物输入的关系
白玛曲宗1,2, 韦恒叶1,2, 江增光2, 邱振3     
1. 东华理工大学核资源与环境教育部重点实验室大气环境实验室, 南昌 330013;
2. 东华理工大学地球科学学院, 南昌 330013;
3. 中国石油勘探开发研究院, 北京 100083
摘要: 二叠纪末期发生了显生宙以来规模最大的生物灭绝事件,利用江西修水东岭剖面二叠—三叠系界线的碳同位素、主量元素及微量元素分别研究全球碳循环的变化及其相对应的物源的变化进而分析环境变化与生物灭绝的关系。研究结果表明,东岭剖面二叠—三叠系界线存在阶梯式碳同位素负偏,第一阶段阶梯式负偏幅度为2‰,第二阶段阶梯式负偏幅度为2.5‰,总的负偏幅度高达4.5‰。在阶段阶梯式碳同位素负偏过程,碳酸盐岩中的硅酸盐组分物源由基性火成岩转变为岛弧性质的酸性火成岩。后者可能与我国华南周围岛弧火山喷发有关。这些碳同位素负偏在时间上与物源的转变及火山灰层基本一致,推测其与我国华南岛弧火山及西伯利亚大火成岩省喷发有关。大规模火山作用喷出或诱发出的二氧化碳及甲烷温室气体有可能是造成二叠—三叠系阶梯式碳同位素负偏的主要原因。火山喷发造成的环境恶化如全球变暖、海洋缺氧、海洋酸化、植被破坏形成的大量沉积物输入海洋致使生物生存压力增大,从而造成二叠末期生物的大灭绝。
关键词碳同位素     二叠-三叠系界线     物源     生物灭绝     东岭剖面    
The Relationship between Carbon Isotopic Changes and the Sediments Supply at the P-T Boundary in Dongling Section, Jiangxi Province
BAI MaQuZong1,2, WEI HengYe1,2, JIANG ZengGuang2, QIU Zhen3     
1. Laboratory Atmospheric Environment, Key Laboratory of Nuclear Resources and Environment(Ministry of Education), East China University of Technology, Nanchang 330013, China;
2. School of Earth Science, East China University of Technology, Nanchang 330013, China;
3. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
Foundation: National Natural Science Foundation of China, No.41302021; Opening Fund from Laboratory Atmospheric Environment, Key Laboratory of Nuclear Resources and Environment (Ministry of Education), East China University of Technology, No.AE1604
Abstract: The largest mass extinction event in the Phanerozoic took place at the end of Permian. The cause of this biological crisis is still remaining controversial. This work uses the carbon isotope, major and minor elements across the Permian-Triassic boundary at the Dongling section in the Xiushui city of the Jiangxi Province to study the relationship between the global carbon cycle perturbation and consistent provenance changes and the mass extinction. The results show that the carbonate carbon isotope profile displays stepwise negative excursion. The magnitudes of first and secondary stepwise are 2‰ and 2.5‰, respectively, with a total magnitude of 4.5‰. In the process of stepwise negative excursion of carbon isotope, the provenance of silicate composition in the carbonate rock changes from mafic igneous rocks to island arc intermediate-acid igneous rocks. The later probably concern with the volcanic eruption of Southern China Island. According to negative excursion of carbon isotope has the same time with the change of provenance and ash layer, conjecture it may relate to South China island arc volcanism and volcanism eruption of Siberian large igneous provinces. Large-scale volcanism eruption released or triggered carbon dioxides and methane. These greenhouse gases and the global regression probably are the main causes for this stepwise carbon isotopic excursion across the Permian-Triassic boundary. The deteriorated environments resulted from the volcanism, e.g., global warming, marine anoxia, marine acidification, large sediment influx resulted from vegetation deterioration, lead to the increased pressure of organism existence and thus the mass extinction.
Key words: carbon isotope     Permian-Triassic boundary     provenance     mass extinction     Dongling Section    
0 引言

二叠末期生物大灭绝事件是显生宙最大的生物危机事件[1],化石记录表明大约80%至96%种一级别的海洋无脊椎动物以及大约70%种一级别的陆地脊椎动物在二叠—三叠系界线附近消失[2-3]。研究认为该次生物灭绝主要与西伯利亚大火成岩省的喷发[4-7]、海洋缺氧甚至硫化[8-12]、全球变暖[13-15]以及海洋酸化[16-18]有关。然而,这些全球环境扰动或剧变的性质及时间与生物灭绝的详细过程及方式的关系尚未清楚,二叠末生物大灭绝的最终成因未知[19]

二叠—三叠纪碳同位素组成变化研究已经较为详细而全面。碳同位素比值在二叠—三叠系界线附近全球范围内均发生了负向偏移[20-21],总体上可分为两期负偏[22]。第一期发生在二叠纪末期H. changxingensis牙形石带,距离二叠—三叠纪界线约110 ky[21];界线年龄取252.17 Ma[23],第二期发生在三叠世早期I. isarcica牙形石带(煤山剖面的34层),距离二叠—三叠纪界线约675 ky[24]。第一期碳同位素负偏又可以细分为两个阶段[25-27],第一阶段的碳同位素负偏最大值发生在C. yini-C. zhangi牙形石带,第二阶段碳同位素负偏最大值发生在C. meishanensis牙形石带。这些期次的碳同位素负偏均被认为与西伯利亚大火成岩省喷发有关[20, 27-28]。然而,引起碳同位素比值负偏的轻碳来源问题还存在争议[19],长期的碳同位素扰动及西伯利亚大火成岩省的喷发与短期快速的二叠末期生物大灭绝之间的相互关系尚未清楚。需要在二叠—三叠界线沉积速率较大的剖面开展更多的研究[19]

江西省修水县东岭剖面的长兴组厚度约为煤山剖面长兴组厚度的4倍[29],是沉积速率较大的区域。与煤山剖面一样,其地点靠近华夏古陆的物源区。二叠—三叠纪过渡时期,巢湖和煤山地区的沉积物供应发生了较大的变化,这从侧面上反映了环境的恶化[30],从而诱发了生物危机。这些沉积物的供应与碳同位素变化的关系可以从新的角度探讨碳同位素负偏中轻碳的来源问题以及碳循环扰动、沉积物变化及生物灭绝三者之间的关系。因此,本次研究在江西东岭剖面二叠—三叠系界线地层中开展碳酸盐岩碳同位素组成以及全岩主量、微量元素分析,研究碳同位素比值的变化以及沉积物元素组成的变化来探讨碳循环、沉积物供应的变化与生物灭绝的关系。

1 地质背景

江西东岭剖面位于江西省修水县四都镇东岭村(图 1a),坐标为29°9′48″N,114°36′2″E,交通便利,与四都镇连通乡村公路,距离南昌市大约150 km左右。构造上,该剖面位于一个向斜的核部,由翼部向中心由老至新出露中志留统夏家桥组、上志留统西坑组、中二叠统栖霞组、茅口组、上二叠统龙潭组、长兴组以及下三叠统大冶组(图 1b)。其中长兴组为石林喀斯特地貌,是研究长兴阶及二叠—三叠界线的理想地区之一。

图 1 江西省修水县四都镇东岭剖面地理位置图(a)以及地质图(b) P2q.中二叠统栖霞组;P2m.中二叠统茅口组;P3c.上二叠统长兴组;T1d.下三叠统大冶组 Figure 1 The geography location (a) and geologic map (b) of the Dongling section at Sidu, Xiushui city, Jiangxi province

研究剖面位于华南陆块,该陆块在二叠—三叠纪之交位于特提斯洋东部、北半球赤道附近(图 2)。华南陆块在二叠末时期在东部和西部分别发育华夏台地以及扬子台地。其中扬子台地北部从西至东分别发育峡口—利川湾[23]以及扬子台地北部边缘盆地[31]。长兴期在台地边缘发育生物礁,这些礁主要分布在川东北、湖南慈利地区以及江西东岭地区[31]。江西东岭剖面长兴期的生物礁主要是藻—海绵骨架灰岩[32]。江西沿沟地区为在长兴期为非礁的浅水碳酸盐岩相[33-34]。浙江煤山剖面在长兴期为斜坡环境而在早三叠世为盆地环境[35]

图 2 扬子台地北部晚二叠世古地理图(修改自冯增昭等[31]) Figure 2 The late Permian palaeogeography in the northern Yangtze Platform (modified from Feng et al.[31])

东岭剖面自下而上出露上二叠统长兴组和下三叠统大冶组(图 3)。长兴组主要为灰白色块状生物碎屑石灰岩,而大冶组底部主要为薄层状灰泥石灰岩(图 3)。在长兴组顶部发育一套杂色微生物岩,含丰富的球状微生物、介形虫、小腹足和小双壳类化石(图 4)[36-37]。在大冶组底部27层首次出现H.parvus牙形石,标志着二叠—三叠系界线[38]。大冶组中—薄层状石灰岩中含化石很少,主要是小介形虫、薄壳的双壳类、管状和舌状的小腕足类[36]

图 3 江西修水县东岭剖面二叠—三叠系界线地层 Figure 3 The Permian-Triassic boundary stratigraphy at Dongling, Xiushui city, Jiangxi province
图 4 江西修水县东岭剖面碳、氧同位素地层及其与Wu et al.[39]剖面对比图(H. parvus据朱相水等[39]) Figure 4 The C and O isotopic stratigraphy in the Dongling section, Xiushui, Jiangxi province and the correlation with the nearby section studied by Wu et al.[39] (Conodont H. parvus data is from Zhu et al.[39])

所测剖面上,由于地层界线有一段地层被覆盖,所以无法获取连续的剖面,即25-26缺失了一段地层。而吴亚生等[37]在离本次剖面北部约10 m远处,通过人工开挖,获得了一个连续出露的PTB剖面(图 3)。在本次研究剖面长兴组顶部为微生物岩,相比Wu et al.[39]所研究的剖面缺失了微生物岩的上部(图 4)。即本次剖面的24b层与Wu et al.[39]剖面的第二层相对应,出现H.parvus牙形石27层与Wu et al.[39]的第5层相对应。本次研究剖面缺失地层与Wu et al.[39]剖面中2-3层相对应,为一段生物碎屑颗粒岩、灰泥岩及微生物岩。

2 实验方法

东岭剖面采集了67个块状样品,岩石切割抛光后,利用牙钻钻取石灰岩灰泥部分,将粉末样品用玛瑙研钵进一步磨碎加工后利用称样纸包裹好用于无机碳同位素比值测试分析。将块状样品破碎成小块后利用玛瑙研钵粉碎至200目以下,用于元素含量测试分析。

粉末样品的无机碳同位素比值测试分析在东华理工大学核资源与环境教育部重点实验室进行。测试方法为磷酸法,以纯He气作为载气,将40 mg左右(量的多少取决于碳酸盐含量)粉末样品放入恒温槽中与0.03毫升98%的磷酸在72 ℃反应平衡1小时。生成的CO2气体经提纯后在德国Finnigan公司生产的气体同位素比值质谱仪MAT253中进行碳、氧同位素比值测定。碳同位素与氧同位素比值的测试分析精度均优于0.2‰(2σ)。δ13C和δ18O数据均为VPDB标准。

粉末样品的元素含量测试分析主要利用X射线荧光光谱(XRF)仪在东华理工大学核资源与环境重点实验室完成。称取4 g粉末样品,利用压片法,不加任何黏结剂,以硼酸垫底直接压制成薄片。将薄片放入型号为Axios-mAX的XRF仪器中进行测试分析。主量元素的分析精度优于5%,微量元素的分析精度优于8%。

3 实验结果

碳酸盐岩碳同位素比值δ13Ccarb分布在-1.42‰~4.7‰,平均值为2.6‰(表 1)。垂向上,东岭剖面δ13Ccarb值在长兴组中至下部基本稳定在4‰左右,至长兴组上部24a层的上半部分开始突然出现负偏,至二叠—三叠系界线达到最大负偏(图 4)。其负偏过程呈现出阶梯式,可分为两个阶梯,第一个阶梯式负偏出现在24a层的中部,负偏幅度达2‰左右,负偏过程中岩性没有发生变化,均为灰白色厚层至块状生物碎屑石灰岩;第二个阶梯式负偏出现在24b层的底部,也就是开始出现微生物岩时发生快速的负偏,负偏幅度达2.5‰左右,同时伴随着岩性的突变。碳酸盐岩氧同位素比值δ18Ocarb分布在-13.2‰~-7.3‰,平均值为-10.2‰(表 1)。垂向上,东岭剖面长兴组灰白色厚层至块状生物碎屑石灰岩δ18Ocarb大部分分布在-12‰~-9.5‰,同位素比值较负(图 4),而上二叠统长兴组顶部微生物岩和下三叠统大冶组底部中至薄层状灰泥石灰岩δ18Ocarb大部分分布在-8.7‰~-7‰,其同位素比值相对长兴组生物碎屑石灰岩较重。

表 1 江西省修水县东岭剖面主量元素、微量元素、Mn/Sr比值与碳酸盐岩碳、氧同位素比值数据 Table 1 Major element, minor element and carbonate carbon and oxygen isotopic ratio data
SiO2
/%
Al2O3
/%
Fe2O3
/%
MgO
/%
CaO
/%
Ti
/(ug/g)
Mn
/(ug/g)
Sr
/(ug/g)
Mn/Sr Al2O3
/TiO2
δ13C
/‰
δ18O
/‰
DL01 4 -10.3
DL02 0.34 2.85 0.99 1.06 94.42 1 653 147 228 0.64 17 3.9 -9.8
DL03 0.48 2.91 0.99 0.87 94.41 1 660 147 232 0.63 18 4 -10.3
DL04 0.31 2.82 0.98 0.73 94.77 1 647 144 299 0.48 17 3.9 -10.1
DL05 0.37 3.05 1.06 5.5 89.68 1 921 160 171 0.93 16 2.8 -10.9
DL06 0.59 3.37 1.14 10.3 84.21 1 892 173 157 1.1 18 3.6 -9.5
DL07 0.63 3.61 1.29 19.58 74.47 2 028 189 131 1.44 18 4.1 -9.8
DL08 0.39 3.02 1.04 4.2 91 153 204 0.75 3.7 -11.7
DL09 0.63 3.67 1.26 22.5 71.51 2 067 199 113 1.75 18 4.7 -8
DL10 0.34 2.94 1.02 2.27 93.05 1 713 150 215 0.7 17 4.3 -7.9
DL11 0.4 3.47 1.24 19.34 75.12 2 018 196 105 1.86 17 3.8 -8.9
DL12 0.36 2.94 1.02 2.63 92.69 1 708 150 242 0.62 17 4 -10.2
DL13 0.47 3.18 1.09 7.65 87.22 1 809 165 191 0.86 18 4 -10.6
DL14 0.36 2.88 1 1.29 94.12 1 667 147 259 0.57 17 3.9 -10.1
DL15 0.37 2.84 0.98 0.65 94.79 1 642 145 270 0.53 17 3.9 -10.1
DL16 0.39 3.15 1.1 7.64 87.32 1 829 166 180 0.92 17 3.9 -10.1
DL17 0.32 2.87 1 1.45 94 1 671 151 235 0.64 17 3.7 -10.9
DL18 0.47 2.94 1.01 2.08 93.17 1 677 150 222 0.68 18 3.8 -11.4
DL19 0.69 3.11 1 0.59 94.23 1 669 144 271 0.53 19 3.3 -10.4
DL20 0.39 2.93 1.01 1.93 93.42 1 686 151 219 0.69 17 3.7 -10.5
DL21 0.32 2.84 0.99 0.97 94.56 1 660 145 17 3.8 -10.6
DL22 0.33 2.85 0.99 0.82 94.68 1 658 148 240 0.62 17 3.7 -10.6
DL23 0.38 2.88 1 1.27 94.09 1 669 148 224 0.66 17 3.1 -10.8
DL24 0.3 2.81 0.98 0.6 94.96 1 648 142 276 0.52 17 3.6 -10.7
DL25 0.32 2.82 0.99 1.09 94.45 1 652 147 234 0.63 17 4 -10.6
DL26 0.3 2.8 0.98 0.4 95.19 1 645 146 248 0.59 17 2.7 -11.6
DL27 0.39 2.85 0.98 0.74 94.72 1 635 143 235 0.61 17 3.4 -13.2
DL28 0.34 2.82 0.98 0.45 95.06 1 636 144 260 0.55 17 3.8 -11.2
DL29 0.42 2.85 0.97 0.37 95.03 1 624 143 256 0.56 18 3.9 -11.2
DL30 0.34 2.8 0.98 0.41 95.12 1 635 143 252 0.57 17 3 -11.5
DL31 0.35 2.85 0.99 0.95 94.51 1 653 145 238 0.61 17 3.9 -11
DL32 0.41 2.86 0.98 0.45 94.96 1 645 143 244 0.59 17 3.6 -11.5
DL33 0.51 2.86 0.98 0.65 94.6 1 646 142 277 0.51 17 4 -10.1
DL34 0.42 3.44 1.26 17.54 76.95 1 996 190 101 1.87 17 1.1 -9.6
DL35 0.37 3.24 1.14 11.48 83.36 1 886 172 139 1.24 17 3.7 -11.1
DL36 0.42 3.11 1.08 6.58 88.43 1 797 162 189 0.86 17 3.9 -10.5
DL37 0.38 2.95 1.03 2.38 92.94 1 705 155 193 0.8 17 2.9 -11.4
DL38 0.38 2.88 0.99 0.85 94.57 1 657 144 233 0.62 17 3.7 -11.2
DL39 0.32 2.82 0.98 0.38 95.16 1 644 142 257 0.55 17 3.5 -11.4
DL40 0.31 2.81 0.98 0.45 95.08 1 641 143 321 0.44 17 3.7 -10.7
DL41 0.44 3.1 1.08 5.75 89.26 1 786 161 191 0.85 17 3.9 -10.6
DL42 0.32 2.81 0.98 0.41 95.13 1 635 143 265 0.54 17 4 -10.6
DL43 0.3 2.81 0.98 0.4 95.15 1 639 143 282 0.51 17 3.6 -11
DL44 0.33 2.8 0.97 0.35 95.22 1 631 146 263 0.55 17 3.6 -10.8
DL45 0.37 2.84 0.98 0.39 95.06 1 633 143 279 0.51 17 3.5 -10.3
DL46 0.35 2.83 0.99 0.43 95.03 1 652 145 295 0.49 17 3.2 -10.7
DL47 0.3 2.81 0.98 0.43 95.11 1 645 145 294 0.49 17 3.8 -10.8
DL48 0.36 2.84 0.99 0.43 95.04 1 651 142 252 0.56 17 3.8 -10.9
DL49 0.52 2.92 0.98 0.33 94.9 1 637 144 232 0.62 18 1.2 -11.2
DL50 0.72 3.01 1.01 0.38 94.54 1 658 154 265 0.58 18 1.8 -11.4
DL51 0.66 2.94 1 0.44 94.59 1 652 149 272 0.55 18 1.8 -11.7
DL52 0.42 2.9 0.99 0.39 94.93 1 647 147 278 0.53 18 2 -12.2
DL53 0.39 2.9 1 0.4 94.98 1 659 155 269 0.57 17 2.1 -11
DL54 0.36 2.84 0.99 0.39 95.05 1 646 154 288 0.54 17 2 -11
DL55 13.12 6.51 1.6 4.04 73.32 2 132 211 341 0.62 31 -0.2 -7.5
DL56 4.63 4.03 1.2 1.17 88.19 1 781 178 912 0.19 23 -0.8 -8.1
DL57 8.49 5.08 1.4 3.96 80.08 1 930 205 273 0.75 26 -0.8 -8.9
DL58 6.02 4.28 1.2 0.64 86.87 1 788 175 702 0.25 24 -0.5 -8.7
DL59 6.05 4.35 1.24 2.66 84.82 1 822 217 323 0.67 24 -0.8 -7.8
DL60 3.97 3.5 1.09 0.5 90.33 1 697 166 795 0.21 21 -0.7 -8.2
DL61 5.37 4.05 1.14 0.69 87.95 1 759 181 491 0.37 23 -1.1 -8.3
DL62 10.18 5.42 1.37 0.82 80.84 1 943 178 903 0.2 28 -0.4 -8.4
DL63 7.43 4.57 1.24 0.78 85.01 1 830 189 351 0.54 25 -1.4 -8.8
DL64 7.54 4.73 1.25 0.87 84.43 1 849 182 483 0.38 26 -1 -7.9
DL65 4.65 3.91 1.17 0.75 88.76 1 752 172 620 0.28 22 -1.4 -9.4
DL66 5.31 4.02 1.18 0.65 87.98 1 770 177 770 0.23 23 -0.9 -8.7
DL67 -0.9 -7.3

Al2O3含量分布在2.80%~6.51%,平均值为3.25%;Ti含量分布在1 623 ~2 132 μg/g,平均值为1 733 μg/g;Fe2O3含量分布在0.97%~1.60%,平均值为1.07%(表 1)。CaO含量分布在71.51%~95.22%,平均值为90.68%。Al2O3/TiO2比值分布在16~31,平均值为19。Mn/Sr比值主要分布在0.19~1.87,平均值为0.66。垂向上,Al、Ti和Fe曲线变化一致(图 5),在长兴组灰白色生物碎屑灰岩段绝大部分呈现为一条稳定的直线(除了在3~5 m处,以及16 m处出现小的波动以外)。然而,在长兴组岩性突变处24b层底部,也就是开始出现杂色微生物岩处,Al、Ti和Fe值开始突然升高,然后下降,至微生物岩顶部下降至最低值,至中—薄层灰泥石灰岩二叠—三叠界线处出现一次幅度较小的突然升高,然后突然下降。总之,Al、Ti和Fe在二叠—三叠界线附近值突然增大,并呈现快速的波动。

图 5 江西省修水县东岭剖面Al、Ti和Fe元素含量变化曲线图 Figure 5 The Al, Ti and Fe profiles at Dongling, Xiushui, Jiangxi province
4 讨论 4.1 成岩作用的影响

碳酸盐岩全岩无机碳同位素比值容易受到成岩作用的影响,从而改变了其原始海水溶解无机碳的碳同位素比值信号。在利用碳同位素比值进行古气候古环境分析之前需要评估成岩作用的影响。由于成岩流体中含大量的氧原子,在进行水—岩反应时往往会伴随着较大的氧同位素分馏[40-41],碳酸盐岩全岩氧同位素极容易受到成岩作用的改造从而改变了其原始海水的氧同位素比值。受成岩作用影响较大的海相碳酸盐岩其碳同位素与氧同位素往往表现为较大的相关性[40]。因此,可以利用碳同位素比值与氧同位素比值作交汇图来判断成岩作用对碳同位素的改造程度[42]。东岭剖面碳酸盐岩碳同位素与氧同位素交汇图(图 6)表明,碳同位素比值与氧同位素比值总体上为负相关而非正相关,说明总体上该剖面碳同位素比值与氧同位素比值没有相关性,碳同位素比值受到成岩作用影响较小。由于碳—氧同位素比值交汇图数据明显分为两组(图 6),一组为24b层以下的长兴组浅水生物碎屑石灰岩,另一组为24b层及其以上的长兴组及大冶组地层。将这两组分别制作碳—氧同位素比值交汇图(图 78)。长兴组灰白色生物碎屑石灰岩碳氧同位素比值数据点分布较为离散(图 7),两者的相关系数(R2)仅为0. 16,相关性很弱。虽然氧同位素比值较负(-8‰~-13‰),但碳同位素比值较重(1‰~4.6‰),落在正常海水无机碳同位素比值范围之内,反映原始海水的信号[43]。而24b层及其以上的长兴组顶部微生物岩和大冶组中—薄层灰泥石灰岩碳—氧同位素比值相关系数(R2)仅为0.18,相关性很弱(图 8),碳同位素组成受成岩及后期蚀变作用的影响程度较低,反映原始海水碳同位素信号。

图 6 江西省修水县东岭剖面碳—氧同位素比值交汇图阴影部分代表 24b层以下地层 Figure 6 Crossplot between C and O isotopic ratios at Dongling, Xiushui, Jiangxi province
图 7 江西省修水县东岭剖面24b层以下地层碳—氧同位素比值交汇图 Figure 7 Crossplot between C and O isotopic ratios at below 24 bed in Dongling, Xiushui, Jiangxi province
图 8 江西省修水县东岭剖面24b层及以上地层碳—氧同位素比值交汇图 Figure 8 Crossplot between C and O isotopic ratios at 24 bed above in Dongling, Xiushui, Jiangxi province

此外,Mn和Sr元素也可以用来识别成岩作用对全岩样品的改造[44-46]。在碳酸盐岩的沉积后期的溶解以及重结晶作用过程中富集Mn[44, 47-48]。Sr一般保存在原始海水形成的碳酸盐相中[49-50],而在溶解和重结晶过程中容易流失[48, 51]。因此,当Mn/Sr比值较低,如小于2~3时,成岩作用影响很小[52-54]。东岭剖面Mn/Sr比值分布在0.2~1.9之间,说明成岩作用影响小,碳同位素和元素等地球化学指标能反映原始沉积的信息。

4.2 地层对比

如前文所述,成岩作用对研究剖面碳同位素影响较小,碳同位素组成的变化往往可以用来对全球或区域性不同环境下的地层进行对比[55]。二叠—三叠系界线地层的碳同位素比值一般存在碳同位素负偏[20],这种同位素比值的变化往往可以作为全球地层对比的标志层[56-57]。将江西东岭剖面与其西部湖南慈利剖面、其东部江西沿沟剖面及浙江煤山剖面的碳同位素组成变化曲线进行对比(图 9)。结果显示,东岭剖面第一阶梯碳同位素负偏可以与慈利剖面第一阶梯碳同位素负偏对比,其碳同位素曲线的突然负偏与江西沿沟剖面及浙江煤山剖面碳同位素曲线负偏的开始一致,对应C. yini带的下部。东岭剖面的第二阶梯碳同位素负偏可以与慈利剖面第二阶梯碳同位素负偏对比,其突然负偏与煤山剖面主灭绝层最大负偏以及沿沟剖面碳同位素的突然负偏一致,对应着C. meishanensis牙形石带底部,也即主要灭绝层位的底部。因此,东岭剖面碳酸盐岩阶梯式碳同位素负偏发生在二叠—三叠界线之前的C. yiniC. zhangi牙形石带以及C. meishanensis牙形石带底部。

图 9 江西修水县东岭剖面与其他剖面碳同位素地层对比 慈利剖面据Luo et al.[26],沿沟剖面据Song et al.[58],煤山剖面据Yin et al.[23]和Cao et al. [25]。不同剖面比例尺不同 Figure 9 The stratigraphic correlation of carbon isotope between the Dongling Section and other sections
4.3 碳同位素负偏的成因

东岭剖面长兴组上部发生了阶梯式碳同位素负偏,第一次负偏由4‰突然负偏至2‰,负偏幅度达2‰,对应于C. yini牙形石带下部;第二次负偏由2‰突然负偏至-0.5‰左右,负偏幅度达2.5‰,对应于C. meishanensis牙形石带底部。这些发生于主灭绝事件之前的碳同位素负偏说明当时存在大量12C的输入。而火山喷出的二氧化碳、生物或热成因甲烷为富12C的碳库来源,这些物质的输入均有可能影响东岭剖面碳同位素负偏[20]

东岭剖面从长兴组微生物岩开始至大冶组石灰岩,其Al、Ti和Fe含量明显比其下部含量要高,且呈现出快速波动变化特征(图 5)。表明陆源碎屑物质供应从微生物岩底部开始明显增加。具有相同物源的岩石其Al与Ti、Al与Fe往往呈现相关性高的直线关系[59-60],然而东岭剖面Al与Ti(图 10a)、Al与Fe(图 10b)交汇图中数据点均出现了分叉,两者之间并不是一条直线,而是两条相关性强的回归直线。微生物岩及其以上地层与微生物岩以下地层中Al和Ti、Al和Fe表现出两种截然不同的行为特征,表明长兴组顶部微生物岩至下三叠统大冶组地层与长兴组微生物岩以下地层具有不同的物源[60]。也即,以24b层底部为界,上下地层具有不同的物源。微生物岩以下地层中Al2O3/TiO2比值分布在16~19,说明岩石中硅酸盐组分物源来自铁镁质火成岩[61];微生物岩及其以上地层中Al2O3/TiO2比值分布在21~31,说明岩石中硅酸盐组分物源来自长英质火成岩[61]。这些表明在二叠—三叠系界线附近陆源碎屑物源由原来的基性火成岩转变为岛弧性质的酸性火成岩[62]。此外,华南二叠—三叠系界线附近广泛发育的火山灰被认为是英安至流纹质火成岩来源[63]。华夏板块周围碎屑锆石年龄(250~258 Ma)研究表明华夏板块西南部在晚二叠世曾发生过造山运动[64]。这些研究说明,华夏板块在二叠纪晚期发生的造山运动及火山喷发形成英安至流纹质的火成岩,这些火成岩可能是东岭剖面从微生物岩开始出现长英质来源的陆源碎屑组分的成因,而且时间上与西伯利亚大火成岩省喷发期一致。

图 10 江西东岭剖面Al与Ti(a)及Al与Fe(b)交汇图 Figure 10 The crossplots between Al and Ti (a) and between Al and Fe (b) at Dongling, Jiangxi province

陆源碎屑物源转变为酸性火成岩之后或之前形成的地层中普遍含有二叠—三叠系界线附近的火山灰层(图 9)。煤山剖面在长兴组上部见火山灰层[21],在东岭剖面的大冶组下部也发现了多个火山灰层[33]。这些火山灰可能来自华南周围岛弧火山喷发[62, 65]。这些岛弧火山及西伯利亚大火成岩省喷发与碳同位素负偏均发生在二叠—三叠纪界线附近。东岭剖面阶梯式碳同位素负偏的开始(也即第一阶段阶梯式碳同位素负偏)出现在灰白色生物碎屑石灰岩之中,可以与煤山剖面23层与24层界线附近开始的碳同位素负偏对比,是一个全球性的碳同位素负偏,也是二叠末期多期碳同位素负偏事件的开始[20]。该次负偏过程中岩性没有变化,始终为生物碎屑碳酸盐岩,且Al、Ti和Fe含量没有发生变化(图 5),说明碳同位素组成的变化与岩性无关,很可能是全球环境变化(如全球碳循环)的成因。二阶梯式碳同位素负偏的层位与华南火山灰层位基本一致,均是出现在二叠—三叠系界线之前约150 ky范围之内[21],推测其负偏可能是华南岛弧火山及西伯利亚大火成岩省喷发的成因[27, 66]

火山喷出的CO2其碳同位素比值为-5‰[67],仅仅由西伯利亚大火成岩省的火山作用难以形成高达4.5‰的碳同位素负偏[68-70]。因此,二叠—三叠系界线附近碳同位素负偏除了火山作用对12C的贡献以外,还有其他富12C的碳库来源。东岭剖面碳同位素曲线在二叠末期突然快速的下降从而形成阶梯式;煤山剖面碳同位素曲线在最大负偏处同样是表现为突然快速的负偏(图 9)。这些表明,二叠纪末期碳同位素负偏过程中存在某一时期快速的负偏,全球碳循环快速扰动,这些特征与甲烷输入大气造成的碳同位素组成变化特征相似[71-72]。西伯利亚大火成岩省岩体侵入富有机质的沉积岩中,接触热变质会导致有机质(如煤、烃类)释放出大量的二氧化碳和甲烷,这些富12C的热成因碳库的输入会引起碳同位素比值快速负偏[73]。此外,二叠末气候变暖时诱发海底甲烷冰不稳定而释放出大量富12C的甲烷也是二叠—三叠界线碳同位素快速负偏的原因之一[74-75],尽管有研究认为晚二叠世晚期逐渐释放出不稳定的甲烷致使到二叠末期已经没有足够的甲烷冰造成如此之大幅度的碳同位素负偏[76]

4.4 碳同位素负偏与生物灭绝的关系

二叠—三叠纪界线生物灭绝方式呈现为两幕,第一幕的生物灭绝高峰出现于煤山剖面的25层底,第二幕的生物灭绝高峰出现于煤山剖面29层底[58]。而东岭剖面二叠末期出现两个阶段的阶梯式碳同位素负偏,第一阶段阶梯式碳同位素负偏的开始对应着第一幕生物灭绝的开始,第二阶段阶梯式负偏的开始对应着第二幕生物灭绝的开始。前文所述,碳同位素负偏主要与华南岛弧火山及西伯利亚大火成岩省的喷发、热成因甲烷与生物甲烷冰的释放有关。西伯利亚大火成岩省大规模火山喷出或诱发出的温室气体(例如二氧化碳和甲烷)导致全球气候变暖[13-14],海洋表层温度过高致使海洋生物生理不适应而大量死亡[14]。海水温度过高导致氧气在海水的溶解度下降以及海洋循环的迟缓形成海洋缺氧[8]。大规模火山喷发引起大气二氧化碳浓度升高,海水的二氧化碳浓度随之升高,再加上火山喷发的硫酸盐气溶胶、酸雨的降落形成海洋酸化导致部分高钙生物不适应而死亡[77]。大规模火山喷发形成的酸雨破坏陆地生态系统,造成水土保持能力下降,导致大量的富Al、Ti和Fe沉积物输入海洋造成浑浊水体[30],再加上海洋酸化及缺氧的物理化学条件的变化,从而引发了大规模的生物灭绝。

5 结论

江西东岭剖面在长兴组及大冶组界线附近物源由原来的基性火成岩转变为岛弧性质的酸性火成岩。后者可能与我国华南周围岛弧火山喷发有关。该剖面二叠—三叠系界线之下碳酸盐岩碳同位素曲线表现为二阶梯式碳同位素负偏。碳同位素负偏过程伴随着Al、Ti和Fe元素的突然大量输入以及物源的突然变化,并与火山灰分布层位基本一致。碳同位素二阶梯式负偏很可能是由华南岛弧火山及西伯利亚大火成岩省喷发及其引发的大量甲烷释放造成的。大规模火山作用引发的全球变化、海洋缺氧、海洋酸化以及陆地大量沉积物的输入导致环境恶化,引发了二叠末期生物大规模灭绝。

参考文献
[1] Erwin D H, Bowring S A, Jin Y G. End-Permian mass extinctions:a review[J]. Geological Society of America Special Paper, 2002, 365: 363–384.
[2] McKinney M L. Extinction selectivity among lower taxa:gradational patterns and rarefaction error in extinction estimates[J]. Paleobiology, 1995, 21(3): 300–313. DOI: 10.1017/S0094837300013312
[3] Benton M J, Twitchett R J. How to kill (almost) all life:the end-Permian extinction event[J]. Trends in Ecology & Evolution, 2003, 18(7): 358–365.
[4] Campbell I H, Czamanske G K, Fedorenko V A, et al. Synchronism of the Siberian traps and the Permian-Triassic boundary[J]. Science, 1992, 258(5089): 1760–1763. DOI: 10.1126/science.258.5089.1760
[5] Renne P R, Black M T, Zhang Z C, et al. Synchrony and causal relations between Permian-Triassic boundary crises and Siberian flood volcanism[J]. Science, 1995, 269(5229): 1413–1416. DOI: 10.1126/science.269.5229.1413
[6] Reichow M K, Pringle M S, Al'Mukhamedov A I, et al. The timing and extent of the eruption of the Siberian Traps large igneous province:implications for the end-Permian environmental crisis[J]. Earth and Planetary Science Letters, 2009, 277(1/2): 9–20.
[7] Sobolev S V, Sobolev A V, Kuzmin D V, et al. Linking mantle plumes, large igneous provinces and environmental catastrophes[J]. Nature, 2011, 477(7364): 312–316. DOI: 10.1038/nature10385
[8] Wignall P B, Twitchett R J. Oceanic anoxia and the end Permian mass extinction[J]. Science, 1996, 272(5265): 1155–1158. DOI: 10.1126/science.272.5265.1155
[9] Isozaki Y. Permo-Triassic boundary superanoxia and stratified superocean:records from lost deep sea[J]. Science, 1997, 276(5310): 235–238. DOI: 10.1126/science.276.5310.235
[10] Grice K, Cao C Q, Love G D, et al. Photic zone euxinia during the Permian-Triassic superanoxic event[J]. Science, 2005, 307(5710): 706–709. DOI: 10.1126/science.1104323
[11] Kump L R, Pavlov A, Arthur M A. Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of oceanic anoxia[J]. Geology, 2005, 33(5): 397–400. DOI: 10.1130/G21295.1
[12] Wei H Y, Algeo T J, Yu H, et al. Episodic euxinia in the Changhsingian (late Permian) of South China:evidence from framboidal pyrite and geochemical data[J]. Sedimentary Geology, 2015, 319: 78–97. DOI: 10.1016/j.sedgeo.2014.11.008
[13] Joachimski M M, Lai X, Shen S, et al. Climate warming in the latest Permian and the Permian-Triassic mass extinction[J]. Geology, 2012, 40(3): 195–198. DOI: 10.1130/G32707.1
[14] Sun Y D, Joachimski M M, Wignall P B, et al. Lethally hot temperatures during the Early Triassic greenhouse[J]. Science, 2012, 338(6105): 366–370. DOI: 10.1126/science.1224126
[15] Romano C, Goudemand N, Vennemann T W V, et al. Climatic and biotic upheavals following the end-Permian mass extinction[J]. Nature Geoscience, 2013, 6(1): 57–60. DOI: 10.1038/ngeo1667
[16] Payne J L, Turchyn A V, Paytan A, et al. Calcium isotope constraints on the end-Permian mass extinction[J]. Proceedings of the National Academy of Science of the United States of America, 2010, 107(19): 8543–8548. DOI: 10.1073/pnas.0914065107
[17] Hinojosa J L, Brown S T, Chen J, et al. Evidence for end-Permian ocean acidification from calcium isotopes in biogenic apatite[J]. Geology, 2012, 40(8): 743–746. DOI: 10.1130/G33048.1
[18] Kershaw S, Crasquin S, Li Y, et al. Ocean acidification and the end-Permian mass extinction:to what extent does evidence support hypothesis?[J]. Geosciences, 2012, 2(4): 221–234. DOI: 10.3390/geosciences2040221
[19] Shen S Z, Bowring S A. The end-Permian mass extinction:a still unexplained catastrophe[J]. National Science Review, 2014, 1(4): 492–495. DOI: 10.1093/nsr/nwu047
[20] Korte C, Kozur H W. Carbon-isotope stratigraphy across the Permian-Triassic boundary:a review[J]. Journal of Asian Earth Sciences, 2010, 39(4): 215–235. DOI: 10.1016/j.jseaes.2010.01.005
[21] Shen S Z, Crowley J L, Wang Y, et al. Calibrating the end-Permian mass extinction[J]. Science, 2011, 334(6061): 1367–1372. DOI: 10.1126/science.1213454
[22] Xie S C, Pancost R D, Huang J H, et al. Changes in the global carbon cycle occurred as two episodes during the Permian-Triassic crisis[J]. Geology, 2007, 35(12): 1083–1086. DOI: 10.1130/G24224A.1
[23] Yin H F, Xie S C, Luo G M, et al. Two episodes of environmental change at the Permian-Triassic boundary of the GSSP section Meishan[J]. Earth-Science Reviews, 2012, 115(3): 163–172. DOI: 10.1016/j.earscirev.2012.08.006
[24] Burgess S D, Bowring S, Shen S Z. High-precision timeline for Earth's most severe extinction[J]. Proceedings of the National Academy of Sciences of the United States of America, 2014, 111(9): 3316–3321. DOI: 10.1073/pnas.1317692111
[25] Cao C Q, Wang W, Yin Y G. Carbon isotope excursions across the Permian-Triassic boundary in the Meishan section, Zhejiang Province, China[J]. Chinese Science Bulletin, 2002, 47(13): 1125–1129. DOI: 10.1360/02tb9252
[26] Luo G M, Kump L R, Wang Y B, et al. Isotopic evidence for an anomalously low oceanic sulfate concentration following end-Permian mass extinction[J]. Earth and Planetary Science Letters, 2010, 300(1/2): 101–111.
[27] Luo G M, Wang Y B, Yang H, et al. Stepwise and large-magnitude negative shift in δ13Ccarb preceded the main marine mass extinction of the Permian-Triassic crisis interval[J]. Palaeogeography, Palaeoclimatology, Palaeoecology, 2011, 299(1/2): 70–82.
[28] Payne J L, Kump L R. Evidence for recurrent Early Triassic massive volcanism from quantitative interpretation of carbon isotope fluctuations[J]. Earth and Planetary Science Letters, 2007, 256(1/2): 264–277.
[29] 朱相水, 林联盛, 吕桦. 推荐一条GSSP的辅助剖面[J]. 江西师范大学学报(自然科学版), 1996, 20 (3): 264–268. [ Zhu Xiangshui, Lin Liansheng, Lü Hua. Recommendation on a reference section of GSSP[J]. Journal of Jiangxi Normal University (Natural Sciences Edition), 1996, 20(3): 264–268. ]
[30] Algeo T J, Twitchett R J. Anomalous Early Triassic sediment fluxes due to elevated weathering rates and their biological consequences[J]. Geology, 2010, 38(11): 1023–1026. DOI: 10.1130/G31203.1
[31] 冯增昭, 杨玉卿, 金振奎, 等. 中国南方二叠纪岩相古地理[M]. 东营: 石油大学出版社, 1997: 1-62. [ Feng Zengzhao, Yang Yuqing, Jin Zhenkui, et al. Lithofacies paleogeography of the Permian of South China[M]. Dongying: Petroleum University Press, 1997: 1-62. ]
[32] 朱相水. 论赣西北东岭地区生物礁的形成时代[J]. 江西师范大学学报:自然科学版, 1999, 23 (3): 252–258. [ Zhu Xiangshui. On a taking shape era of the reefs in Dongling area of northwest Jiangxi[J]. Journal of Jiangxi Normal University:Natural Sciences Edition, 1999, 23(3): 252–258. ]
[33] 朱相水, 王成源, 吕桦, 等. 江西二叠-三叠系界线[J]. 微体古生物学报, 1994, 11 (4): 439–452. [ Zhu Xiangshui, Wang Chengyuan, Lü Hua, et al. Permian-Triassic boundaries in Jiangxi, China[J]. Acta Micropalaeontologica Sinica, 1994, 11(4): 439–452. ]
[34] 田力, 童金南, 孙冬英, 等. 江西乐平沿沟二叠纪-三叠纪过渡期沉积微相演变及其对灭绝事件的响应[J]. 中国科学:地球科学, 2014, 57 (10): 2195–2207. [ Tian Li, Tong Jinnan, Sun Dongying, et al. The microfacies and sedimentary responses to the mass extinction during the Permian-Triassic transition at Yangou section, Jiangxi province, South China[J]. Science China:Earth Sciences, 2014, 57(10): 2195–2207. ]
[35] 郑全锋. 浙江省长兴县煤山剖面二叠系-三叠系界线层序的沉积微相特征及层序地层划分[J]. 地层学杂志, 2006, 30 (4): 373–383. [ Zheng Quanfeng. Sedimentary microfacies and sequence stratigraphy of the P-T boundary beds of the Meishan section, Changxing county, Zhejiang[J]. Journal of Stratigraphy, 2006, 30(4): 373–383. ]
[36] 姜红霞, 吴亚生. 江西修水二叠系-三叠系界线地层树枝状微生物岩状岩石成因初解[J]. 地质论评, 2006, 53 (3): 323–329. [ Jiang Hongxia, Wu Yasheng. Origin of microbialite-like dendroid rocks in the Permian-Triassic boundary section in Xiushui, Jiangxi province[J]. Geological Review, 2006, 53(3): 323–329. ]
[37] 吴亚生, 姜红霞, YangWan, 等. 二叠纪-三叠纪之交缺氧环境的微生物和微生物岩[J]. 中国科学D辑:地球科学, 2007, 50 (7): 1040–1051. [ Wu Yasheng, Jiang Hongxia, Yang Wan, et al. Microbialite of anoxic condition from Permian-Triassic transition in Guizhou, China[J]. Science China Series D:Earth Science, 2007, 50(7): 1040–1051. ]
[38] 朱相水, 林联盛, 蒋梅鑫. Hindeodus parvus及其"首次出现"[J]. 江西师范大学学报(自然科学版), 1997, 21 (3): 269–274. [ Zhu Xiangshui, Lin Liansheng, Jiang Meixin. Hindeodus parvus and its "First Occurrence"[J]. Journal of Jiangxi Normal University (Natural Sciences Edition), 1997, 21(3): 269–274. ]
[39] Wu Y S, Yuan X H, Jiang H X, et al. Coevality of the sea-level fall and main mass extinction in the Permian-Triassic transition in Xiushui, Jiangxi Province, southern China[J]. Journal of Palaeogeography, 2014, 3(3): 309–322.
[40] Brand U, Veizer J. Chemical diagenesis of a multicomponent carbonate system -2:stable isotopes[J]. Journal of Sedimentary Petrology, 1981, 51(3): 987–997.
[41] Marshall J D. Climatic and oceanographic isotopic signals from the carbonate rock record and their preservation[J]. Geological Magazine, 1992, 129(2): 143–160. DOI: 10.1017/S0016756800008244
[42] Heydari E, Wade W J, Hassanzadeh J. Diagenetic origin of carbon and oxygen isotope compositions of Permian-Triassic boundary strata[J]. Sedimentary Geology, 2001, 143(3/4): 191–197.
[43] Schobben M, Ullmann C V, Leda L, et al. Discerning primary versus diagenetic signals in carbonate carbon and oxygen isotope records:an example from the Permian-Triassic boundary of Iran[J]. Chemical Geology, 2016, 422: 94–107. DOI: 10.1016/j.chemgeo.2015.12.013
[44] Denison R E, Koepnick R B, Fletcher A, et al. Criteria for the retention of original seawater 87Sr/86Sr in ancient shelf limestones[J]. Chemical Geology, 1994, 112(1/2): 131–143.
[45] Brand U, Jiang G Q, Azmy K, et al. Diagenetic evaluation of a Pennsylvanian carbonate succession (Bird Spring Formation, Arrow Canyon, Nevada, U.S.A.) -1:brachiopod and whole rock comparison[J]. Chemical Geology, 2012, 308-309: 26–39. DOI: 10.1016/j.chemgeo.2012.03.017
[46] Brand U, Posenato R, Came R, et al. The end-Permian mass extinction:a rapid volcanic CO2 and CH4-climatic catastrophe[J]. Chemical Geology, 2012, 322-323: 121–144. DOI: 10.1016/j.chemgeo.2012.06.015
[47] Pingitore N E, J r. The behavior of Zn2+ and Mn2+ during carbonate diagenesis:theory and applications[J]. Journal of Sedimentary Petrology, 1978, 48(3): 799–814.
[48] Brand U, Veizer J. Chemical diagenesis of a multicomponent carbonate system -1:trace elements[J]. Journal of Sedimentary Petrology, 1980, 50(4): 1219–1236.
[49] Korte C, Hesselbo S P. Shallow marine carbon and oxygen isotope and elemental records indicate icehouse-greenhouse cycles during the Early Jurassic[J]. Paleoceanography, 2011, 26(4): PA4219.
[50] Ullmann C V, Hesselbo S P, Korte C. Tectonic forcing of Early to Middle Jurassic seawater Sr/Ca[J]. Geology, 2013, 41(12): 1211–1214. DOI: 10.1130/G34817.1
[51] Veizer J, Demovic R, Turan J. Possible use of strontium in sedimentary carbonate rocks as a paleoenvironmental indicator[J]. Sedimentary Geology, 1971, 5(1): 5–22. DOI: 10.1016/0037-0738(71)90016-9
[52] Derry L A, Kaufman A J, Jacobsen S B. Sedimentary cycling and environmental change in the Late Proterozoic:evidence from stable and radiogenic isotopes[J]. Geochimica et Cosmochimica Acta, 1992, 56(3): 1317–1329. DOI: 10.1016/0016-7037(92)90064-P
[53] Kaufman A J, Knoll A H, Awramik S M. Biostratigraphic and chemostratigraphic correlation of Neoproterozoic sedimentary successions:Upper Tindir Group, northwestern Canada, as a test case[J]. Geology, 1992, 20: 181–185. DOI: 10.1130/0091-7613(1992)020<0181:BACCON>2.3.CO;2
[54] Kaufman A J, Jacobsen S B, Knoll A H. The vendian record of Sr and C isotopic variations in seawater:implications for tectonics and paleoclimate[J]. Earth and Planetary Science Letters, 1993, 120(3/4): 409–430.
[55] Weissert H, Joachimski M, Sarnthein M. Chemostratigraphy[J]. Newsletters on Stratigraphy, 2008, 42(3): 145–179. DOI: 10.1127/0078-0421/2008/0042-0145
[56] Kraus S H, Siegert S, Mette W, et al. Stratigraphic significance of carbon isotope variations in the shallow-marine Seis/Siusi Permian-Triassic boundary section (Southern Alps, Italy)[J]. Fossil Record, 2009, 12(2): 197–205. DOI: 10.5194/fr-12-197-2009
[57] Hermann E, Hochuli P A, Bucher H, et al. A close-up view of the Permian-Triassic boundary based on expanded organic carbon isotope records from Norway (Trøndelag and Finnmark Platform)[J]. Global and Planetary Changes, 2010, 74(3/4): 156–167.
[58] Song H J, Wignall P B, Tong J N, et al. Two pulses of extinction during the Permian-Triassic crisis[J]. Nature Geoscience, 2013, 6(1): 52–56. DOI: 10.1038/ngeo1649
[59] McLennan S M, Hemming S, McDaniel D K, et al. Geochemical approaches to sedimentation, provenance, and tectonics[J]. Geological Society of America Special Paper, 1993, 284: 21–40. DOI: 10.1130/SPE284
[60] Huang J, Chu X, Lyons T W, et al. A new look at saponite formation and its implications for early animal records in the Ediacaran of South China[J]. Geobiology, 2013, 11(1): 3–14. DOI: 10.1111/gbi.2012.11.issue-1
[61] Hayashi K I, Fujisawa H, Holland H D, et al. Geochemistry of~1.9 Ga sedimentary rocks from northeastern Labrador, Canada[J]. Geochimica et Cosmochimica Acta, 1997, 61(19): 4115–4137. DOI: 10.1016/S0016-7037(97)00214-7
[62] Yang J H, Cawood P A, Du Y S, et al. Large Igneous Province and magmatic arc sourced Permian-Triassic volcanogenic sediments in China[J]. Sedimentary Geology, 2012, 261-262: 120–131. DOI: 10.1016/j.sedgeo.2012.03.018
[63] Gao Q L, Zhang N, Xia W C, et al. Origin of volcanic ash beds across the Permian-Triassic boundary, Daxiakou, South China:Petrology and U-Pb age, trace elements and Hf-isotope composition of zircon[J]. Chemical Geology, 2013, 360-361: 41–53. DOI: 10.1016/j.chemgeo.2013.09.020
[64] 梁新权, 周云, 蒋英, 等. 二叠纪东吴运动的沉积响应差异:来自扬子和华夏板块吴家坪组或龙潭组碎屑锆石LA-ICPMS U-Pb年龄研究[J]. 岩石学报, 2013, 29 (10): 3592–3606. [ Liang Xinquan, Zhou Yun, Jiang Ying, et al. Difference of sedimentary response to Dongwu Movement:study on LA-ICPMS U-Pb ages of detrital zircons from upper Permian Wujiaping or Longtan Formation from the Yangtze and Cathaysia blocks[J]. Acta Petrologica Sinica, 2013, 29(10): 3592–3606. ]
[65] Xie S S, Pancost R D, Wang Y B, et al. Cyanobacterial blooms tied to volcanism during the 5 m.y[J]. Permo-Triassic biotic crisis. Geology, 2010, 38(5): 447–450.
[66] Korte C, Pande P, Kalia P, et al. Massive volcanism at the Permian-Triassic boundary and its impact on the isotopic composition of the ocean and atmosphere[J]. Journal of Asian Earth Sciences, 2010, 37(4): 293–311. DOI: 10.1016/j.jseaes.2009.08.012
[67] McLean D M. Mantle degassing unification of the Trans-K-T geobiological record[J]. Evolutionary Biology, 1985, 19: 287–313.
[68] Kump L R, Arthur M A. Interpreting carbon-isotope excursions:carbonates and organic matter[J]. Chemical Geology, 1999, 161(1/2/3): 181–198.
[69] Wignall P B. Large igneous provinces and mass extinctions[J]. Earth-Science Reviews, 2001, 53(1/2): 1–33.
[70] Berner R A. Examination of hypotheses for the Permo-Triassic boundary extinction by carbon cycle modeling[J]. Proceedings of the National Academy Sciences of the United States of America, 2002, 99(7): 4172–4177. DOI: 10.1073/pnas.032095199
[71] Hesselbo S P, Gröcke D R, Jenkyns H C, et al. Massive dissociation of gas hydrate during a Jurassic oceanic anoxic event[J]. Nature, 2000, 406(6794): 392–395. DOI: 10.1038/35019044
[72] Kamo S L, Czamanske G K, Amelin Y, et al. Rapid eruption of Siberian flood-volcanic rocks and evidence for coincidence with the Permian-Triassic boundary and mass extinction at 251 Ma[J]. Earth and Planetary Science Letters, 2003, 21(1/2)4: 75-91.
[73] Svensen H, Planke S, Polozov A G, et al. Siberian gas venting and the end-Permian environmental crisis[J]. Earth and Planetary Science Letters, 2009, 277(3/4): 490–500.
[74] Krull E S, Retallack G J. δ13C depth profiles from paleosols across the Permian-Triassic boundary:evidence for methane release[J]. Geological Society of America Bulletin, 2000, 112(9): 1459–1472.
[75] Twitchett R J, Looy C V, Morante R, et al. Rapid and synchronous collapse of marine and terrestrial ecosystems during the end-Permian biotic crisis[J]. Geology, 2001, 29(4): 351–354. DOI: 10.1130/0091-7613(2001)029<0351:RASCOM>2.0.CO;2
[76] Majorowicz J, Grasby S E, Safanda J, et al. Gas hydrate contribution to Late Permian global warming[J]. Earth and Planetary Science Letters, 2014, 393: 243–253. DOI: 10.1016/j.epsl.2014.03.003
[77] Clarkson M O, Kasemann S A, Wood R A, et al. Ocean acidification and the Permo-Triassic mass extinction[J]. Science, 2015, 348(6231): 229–232. DOI: 10.1126/science.aaa0193