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高校地质学报 ›› 2026, Vol. 32 ›› Issue (01): 49-60.DOI: 10.16108/j.issn1006-7493.2024037

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塔里木盆地古城地区中下奥陶统碳氧同位素特征及其古环境意义

郭春涛1, 2, 3,李如一4,史江涛1, 2   

  1. 1. 山西工程技术学院 地球科学与工程系,阳泉 045000;
    2. 矿区生态修复与固废资源化厅市共建山西省重点实验室培育基地,山西工程技术学院,阳泉 045000;
    3. 中国石油 大庆油田有限责任公司人才开发院,大庆 163453;
    4. 中国石油 大庆油田有限责任公司勘探事业部,大庆 163453
  • 出版日期:2026-02-14 发布日期:2026-02-14

Carbon and Oxygen Isotopic Characteristics of the Middle to Lower Ordovician Strata in the Gucheng Area, Tarim Basin and Their Geological and Paleoenvironmental Implications

GUO Chuntao1, 2, 3,LI Ruyi4,SHI Jiangtao1, 2   

  1. 1. Department of Earth Sciences and Engineering, Shanxi Institute of Technology, Yangquan 045000, China;
    2. The Cultivation Base of Shanxi Key Laboratory of Mining Area Ecological Restoration and Solid Wastes Utilization,
    Yangquan 045000, China;
    3. Daqing Oilfield Personnel Development Institute, CNPC, Daqing 163453, China;
    4. Exploration Department of Daqing Oilfield Company Limited, CNPC, Daqing 163453, China
  • Online:2026-02-14 Published:2026-02-14

摘要: 海相碳酸盐岩碳氧同位素具有保持原始海水同位素组成的能力,常被用于古海水、古气候、古环境的重建。基于此,文章对塔里木盆地古城低凸起古城8井中下奥陶统86个碳酸盐岩碳氧同位素进行了分析。结果显示,δ13C值分布在-2.32‰~+0.53‰之间,平均为-1.10‰,总体为负值,表现出4个阶段;δ18O分布在-8.80‰~-7.15‰之间,平均为-8.04‰,总体为负值,表现出3个明显的“正漂—负漂”旋回。利用碳氧同位素计算古环境特征的结果显示,早中奥陶世研究区盐度指数Z总体大于120,水温在16.7~26.9 ℃之间,整体表现出温暖—炎热正常盐度的海洋环境;碳氧同位素的变化显示出蓬莱坝组时古海平面持续上升后缓慢下降,鹰山组时古海平面持续震荡且缓慢小幅下降,一间房组时古海平面快速上升并保持高位,其海平面变化过程与全球海平面变化趋势基本一致;而通过盆地内早中奥陶世多个剖面(钻井)δ13C曲线对比,δ13C曲线特征和变化总体相似,且与全球δ13C曲线相似,反映出塔里木盆地早中奥陶世沉积主要受控于海平面变化,而周缘造山等构造活动在早中奥陶世对盆地沉积影响有限。

关键词: 古城地区, 中下奥陶统, 碳氧同位素, 古环境

Abstract:

The carbon and oxygen isotopes of marine carbonate rocks exhibit the inherent capacity to faithfully record the primary isotopic composition of seawater, serving as invaluable proxies for paleoenvironmental reconstructions. Based on this, this study systematically investigates the carbon and oxygen isotopic profiles containing 86 carbonate rock specimens retrieved from the Lower Ordovician strata of well Gucheng 8, situated in Gucheng lower uplift of the Tarim Basin. The results show δ13C values ranging from -2.32‰ to +0.53‰ , with an average of -1.10‰ , delineating four discernible stages. Simultaneously, the δ18O values span -8.80‰ to -7.15‰ , averaging at -8.04‰ , revealing three distinct“positive ten-negative shift”cycles. The computed paleoenvironmental characteristics, based on carbon and oxygen isotopes, underscore a salinity index (Z) consistently exceeding 120 during the Early to Middle Ordovician epoch in the study area. Concurrently, water temperatures exhibit fluctuationsbetween 16.7 ℃ and 26.9 ℃ , indicating an overall warm to hot marine environment with normal salinity levels. Isotopic variations further unveil nuanced sea-level dynamics. During the Penglaiba formation, the ancient sea level underwent a gradual rise followed by a subdued fall. In the Yingshan formation, sea levels exhibited continuous fluctuations with a gradual, marginal decline. Conversely, the Yijianfang formation documents a rapid rise in the ancient sea level, maintaining a sustained high position. These fluctuations closely parallel the global sea-level trends. Comparative scrutiny of δ13C curves across multiple Early to Middle Ordovician profiles (drilling wells) within the basin underscores analogous characteristics and variations. This concordance with global δ13C curves signifies that sedimentary patterns in the Tarim basin during the Early to Middle Ordovician were primarily dictated by sea-level changes, with limited influence by the peripheral orogeny and other tectonic activities.

Key words: Gucheng area, Lower and Middle Ordovician, carbon and oxygen isotopes, paleoenvironment

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