四川盆地长宁县双河地区奥陶系-志留系界线地层剖面海相有机质碳同位素偏移与古大气二氧化碳浓度变化研究

doi:10.13745/j.esf.sf.2024.10.15

地学前缘 ›› 2026, Vol. 33 ›› Issue (2): 515-524.DOI: 10.13745/j.esf.sf.2024.10.15

四川盆地长宁县双河地区奥陶系-志留系界线地层剖面海相有机质碳同位素偏移与古大气二氧化碳浓度变化研究

伊海生¹(), 伊帆²^,³^,⁴^,^*(), 陈云⁵, 田康志¹

1.成都理工大学沉积地质研究院, 四川成都 610059
2.成都理工大学地理与规划学院, 四川成都 610059
3.甘肃省油气资源研究重点实验室, 甘肃兰州 730000
4.中国科学院西北生态环境资源研究院, 甘肃兰州 730000
5.中国地质科学院, 北京 100037

收稿日期:2024-08-06 修回日期:2024-12-06 出版日期:2026-03-25 发布日期:2026-01-29
通信作者: *伊帆(1987—),女,博士,副教授,主要研究方向为沉积地球化学。E-mail: yifan12@cdut.edu.cn
作者简介:伊海生(1959—),男,教授,博士生导师,主要从事西藏高原油气地质和古海洋及古气候研究。E-mail: yhs@cdut.edu.cn
基金资助:
国家自然科学基金项目(42172121);甘肃省油气资源研究重点实验室开放课题(SZDKFJJ2022002)

The carbon isotope excursions of marine organic carbon isotopes and paleoatmospheric CO₂ concentrations reconstruction across the Ordovician-Silurian stratigraphic boundary from Shuanghe, Changning County, Sichuan Basin

YI Haisheng¹(), YI Fan²^,³^,⁴^,^*(), CHEN Yun⁵, TIAN Kangzhi¹

1. Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China
2. College of Geography and Planning, Chengdu University of Technology, Chengdu 610059, China
3. Key Laboratory of Petroleum Resources Research, Gansu Province, Lanzhou 730000, China
4. Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
5. Chinese Academy of Geological Sciences, Beijing 100037, China

Received:2024-08-06 Revised:2024-12-06 Online:2026-03-25 Published:2026-01-29

摘要/Abstract

摘要：

古大气CO₂浓度变化是驱动地球表面温度升高或降低的关键要素,也是我们解析地质历史时期冰室期和温室期气候状态转型的一个重要参数。现代海洋研究证实,海洋浮游植物及其产生的悬浮和沉降颗粒有机碳以及海底沉积物中有机质的碳同位素δ¹³C值大小变化受到海水中溶解CO₂浓度控制,海水溶解CO₂碳同位素(δ¹³ $C C O 2$ )与海洋来源有机质碳同位素(δ¹³C_org)的差值(Δ=δ¹³ $C C O 2$ -δ¹³C_org),与海水溶解CO₂浓度的倒数之间可以采用定量方程进行描述。如果引用海面古大气pCO₂与全球海表平均水温(GAT)相关方程,则可以通过海水溶解CO₂浓度定量计算海表古大气pCO₂,同时求解古海洋平均海面温度和酸碱度pH值。四川盆地长宁县双河地区发育连续的奥陶系上部五峰组和顶部观音桥段以及志留系下部龙马溪组黑色泥页岩地层剖面,观音桥段的地层时代对应赫南特冰室期气候期。这一地表剖面生物化石控制精度高,岩石富有机碳,而且早古生代时期陆生高等植物尚未出现,这为我们采用海洋有机质碳同位素变化计算古大气pCO₂提供了最佳的材料。研究结果表明,观音桥段沉积期古大气CO₂浓度平均值为625 μatm,海表全球平均温度为18.46 ℃,这些与新生代渐新世时期南极冰盖出现时冰室期气候状态可以对比。

关键词: 海洋有机质碳同位素组成, 海水溶解CO₂浓度, 古大气pCO₂, 全球平均温度, 古气候变化, 四川盆地, 观音桥段, 赫南特冰期

Abstract:

Fluctuations in atmospheric CO₂ concentration throughout geological history have been a pivotal driver of Earth’s surface temperature variations, serving as a key parameter for elucidating transitions between icehouse and greenhouse climates. Modern marine studies confirm that the carbon isotope composition (δ¹³C) of marine phytoplankton, their derived particulate organic carbon, and sedimentary organic matter is primarily controlled by the concentration (or partial pressure) of dissolved CO₂ in seawater ([CO₂(aq)]). Previous work has established that the carbon isotope difference (Δ=δ¹³ $C C O 2$ -δ¹³C_org) between seawater [CO₂(aq)] and marine organic matter exhibits a quantifiable relationship with the inverse of [CO₂(aq)]. By incorporating an equation linking sea-surface atmospheric pCO₂ to global average sea surface temperature (GAT), it is possible to estimate past atmospheric pCO₂, mean sea surface temperature, and seawater pH. This study applies this approach to a continuous sedimentary succession spanning the Upper Ordovician Wufeng Formation, the Hirnantian Guanyinqiao Formation, and the Lower Silurian Longmaxi Formation. The Guanyinqiao Formation corresponds to the Hirnantian glaciation. This interval benefits from precise biostratigraphic age control, consists predominantly of organic-rich black shales, and was deposited prior to the emergence of terrestrial plants. Consequently, the δ¹³C of its marine organic matter provides optimal material for reconstructing paleoatmospheric CO₂. Our results indicate that during the deposition of the Guanyinqiao Formation, the average atmospheric pCO₂ was approximately 625 μatm, and the global average sea surface temperature was about 18.46 ℃. This climatic state represents an icehouse condition comparable to that during the Oligocene, following the establishment of the Antarctic Ice Sheet in the Cenozoic era.

Key words: δ¹³C of marine organic carbon, surface seawater dissolved CO₂ concentration, ancient atmospheric pCO₂, global average temperature, palaeoclimatic change, Sichuan Basin, Guanyinqiao Member, Hirnantian ice age

中图分类号:

伊海生, 伊帆, 陈云, 田康志. 四川盆地长宁县双河地区奥陶系-志留系界线地层剖面海相有机质碳同位素偏移与古大气二氧化碳浓度变化研究[J]. 地学前缘, 2026, 33(2): 515-524.

YI Haisheng, YI Fan, CHEN Yun, TIAN Kangzhi. The carbon isotope excursions of marine organic carbon isotopes and paleoatmospheric CO₂ concentrations reconstruction across the Ordovician-Silurian stratigraphic boundary from Shuanghe, Changning County, Sichuan Basin[J]. Earth Science Frontiers, 2026, 33(2): 515-524.

图/表 6

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采样层位	地层	样品序列	采样深度/m	样品编号	TOC 含量/%	δ¹³C_org/‰ (PDB)	石灰岩 δ¹³C_carb/‰ (PDB)	分馏系数 ε_p/‰	CO₂浓度/ (μmol·kg^-1)	pCO₂/ μatm	GAT/℃	pH值
龙马溪组	鲁丹阶	32	16.0	S12	5.41	-30.63	1.2	31.83	25.90	786	19.48	7.94
		31	15.5	S11	4.89	-30.93	1.2	32.13	27.54	843	19.79	7.92
		30	15.1	S10	4.33	-30.79	1.2	31.99	26.90	821	19.67	7.93
		29	14.6	S09	4.27	-30.91	1.2	32.11	27.45	840	19.77	7.92
		28	14.1	S08	5.05	-30.46	1.2	31.66	25.51	773	19.41	7.94
		27	13.6	S07	5.32	-30.60	1.2	31.80	26.08	792	19.52	7.94
		26	13.2	S06	5.69	-30.71	1.2	31.91	26.55	809	19.61	7.93
		25	12.7	S05	5.22	-31.10	1.2	32.30	28.34	871	19.93	7.91
		24	12.2	S04	5.97	-30.76	1.2	31.96	26.77	816	19.65	7.93
		23	11.7	S03	8.00	-30.56	1.2	31.76	25.92	787	19.49	7.94
		22	11.3	S02	9.11	-30.15	1.2	31.35	24.30	731	19.17	7.96
		21	10.8	S01	5.07	-29.35	1.2	30.55	21.61	640	18.59	7.99
观音桥段	赫南特阶	20	10.3	Og06	3.15	-28.76	2.1	30.86	22.59	673	18.81	7.98
		19	10.1	Og05	1.62	-28.06	2.1	30.16	20.48	602	18.33	8.00
		18	9.9	Og04	2.40	-28.08	2.1	30.18	20.53	604	18.34	8.00
		17	9.8	Og03	3.06	-28.32	2.1	30.42	21.22	627	18.50	7.99
		16	9.6	Og02	3.85	-28.29	2.1	30.39	21.13	624	18.48	8.00
		15	9.4	Og01	4.02	-28.26	2.1	30.36	21.05	621	18.46	8.00
五峰组	凯迪阶	14	9.2	Ow14	4.23	-29.81	1.2	31.01	23.09	690	18.92	7.97
		13	8.5	Ow13	4.85	-29.91	1.2	31.11	23.44	702	18.99	7.97
		12	7.8	Ow12	6.10	-29.70	1.2	30.90	22.72	678	18.84	7.98
		11	7.1	Ow11	3.88	-29.73	1.2	30.93	22.82	681	18.86	7.97
		10	6.4	Ow10	3.31	-29.24	1.2	30.44	21.28	629	18.52	7.99
		9	5.7	Ow09	3.91	-29.85	1.2	31.05	23.23	695	18.95	7.97
		8	5.0	Ow08	3.08	-29.65	1.2	30.85	22.56	672	18.80	7.98
		7	4.2	Ow07	3.23	-29.49	1.2	30.69	22.04	655	18.69	7.98
		6	3.5	Ow06	3.29	-29.55	1.2	30.75	22.23	661	18.73	7.98
		5	2.8	Ow05	3.19	-30.10	1.2	31.30	24.12	725	19.13	7.96
		4	2.1	Ow04	4.01	-29.36	1.2	30.56	21.64	641	18.60	7.99
		3	1.4	Ow03	3.80	-30.13	1.2	31.33	24.23	729	19.16	7.96
		2	0.7	Ow02	1.01	-30.23	1.2	31.43	24.60	742	19.23	7.95
		1	0.0	Ow01	0.93	-29.86	1.2	31.06	23.26	696	18.95	7.97

采样层位	地层	样品序列	采样深度/m	样品编号	TOC 含量/%	δ¹³C_org/‰ (PDB)	石灰岩 δ¹³C_carb/‰ (PDB)	分馏系数 ε_p/‰	CO₂浓度/ (μmol·kg^-1)	pCO₂/ μatm	GAT/℃	pH值
龙马溪组	鲁丹阶	32	16.0	S12	5.41	-30.63	1.2	31.83	25.90	786	19.48	7.94
		31	15.5	S11	4.89	-30.93	1.2	32.13	27.54	843	19.79	7.92
		30	15.1	S10	4.33	-30.79	1.2	31.99	26.90	821	19.67	7.93
		29	14.6	S09	4.27	-30.91	1.2	32.11	27.45	840	19.77	7.92
		28	14.1	S08	5.05	-30.46	1.2	31.66	25.51	773	19.41	7.94
		27	13.6	S07	5.32	-30.60	1.2	31.80	26.08	792	19.52	7.94
		26	13.2	S06	5.69	-30.71	1.2	31.91	26.55	809	19.61	7.93
		25	12.7	S05	5.22	-31.10	1.2	32.30	28.34	871	19.93	7.91
		24	12.2	S04	5.97	-30.76	1.2	31.96	26.77	816	19.65	7.93
		23	11.7	S03	8.00	-30.56	1.2	31.76	25.92	787	19.49	7.94
		22	11.3	S02	9.11	-30.15	1.2	31.35	24.30	731	19.17	7.96
		21	10.8	S01	5.07	-29.35	1.2	30.55	21.61	640	18.59	7.99
观音桥段	赫南特阶	20	10.3	Og06	3.15	-28.76	2.1	30.86	22.59	673	18.81	7.98
		19	10.1	Og05	1.62	-28.06	2.1	30.16	20.48	602	18.33	8.00
		18	9.9	Og04	2.40	-28.08	2.1	30.18	20.53	604	18.34	8.00
		17	9.8	Og03	3.06	-28.32	2.1	30.42	21.22	627	18.50	7.99
		16	9.6	Og02	3.85	-28.29	2.1	30.39	21.13	624	18.48	8.00
		15	9.4	Og01	4.02	-28.26	2.1	30.36	21.05	621	18.46	8.00
五峰组	凯迪阶	14	9.2	Ow14	4.23	-29.81	1.2	31.01	23.09	690	18.92	7.97
		13	8.5	Ow13	4.85	-29.91	1.2	31.11	23.44	702	18.99	7.97
		12	7.8	Ow12	6.10	-29.70	1.2	30.90	22.72	678	18.84	7.98
		11	7.1	Ow11	3.88	-29.73	1.2	30.93	22.82	681	18.86	7.97
		10	6.4	Ow10	3.31	-29.24	1.2	30.44	21.28	629	18.52	7.99
		9	5.7	Ow09	3.91	-29.85	1.2	31.05	23.23	695	18.95	7.97
		8	5.0	Ow08	3.08	-29.65	1.2	30.85	22.56	672	18.80	7.98
		7	4.2	Ow07	3.23	-29.49	1.2	30.69	22.04	655	18.69	7.98
		6	3.5	Ow06	3.29	-29.55	1.2	30.75	22.23	661	18.73	7.98
		5	2.8	Ow05	3.19	-30.10	1.2	31.30	24.12	725	19.13	7.96
		4	2.1	Ow04	4.01	-29.36	1.2	30.56	21.64	641	18.60	7.99
		3	1.4	Ow03	3.80	-30.13	1.2	31.33	24.23	729	19.16	7.96
		2	0.7	Ow02	1.01	-30.23	1.2	31.43	24.60	742	19.23	7.95
		1	0.0	Ow01	0.93	-29.86	1.2	31.06	23.26	696	18.95	7.97

四川盆地长宁县双河地区奥陶系-志留系界线地层剖面海相有机质碳同位素偏移与古大气二氧化碳浓度变化研究

The carbon isotope excursions of marine organic carbon isotopes and paleoatmospheric CO₂ concentrations reconstruction across the Ordovician-Silurian stratigraphic boundary from Shuanghe, Changning County, Sichuan Basin

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