早白垩世缺氧事件OAE 1d在东特提斯域的环境响应：来自藏南地区的古环境证据
- 收稿日期:
2025-04-19
- 网络出版日期:
2025-09-12
摘要: 摘要：【目的】早白垩世晚阿尔布期大洋缺氧事件（OAE 1d）是白垩纪温室气候背景下一次重要的碳循环扰动事件。尽管前人在特提斯洋西部和北大西洋等地区对OAE 1d的特征及成因开展了大量研究，但该事件在东特提斯域的古环境响应仍存在认知空白。【方法】本项研究重点选择东特提斯域藏南定日油下剖面下白垩统冷青热组作为对比研究对象，通过矿物岩石学、沉积学、同位素地球化学分析及元素地球化学研究，揭示了OAE 1d时期东特提斯域与全球其他区域同时期在古海洋环境特征方面的差异。【结果】（1）无机碳和有机碳同位素分析均表明，研究区油下剖面记录了OAE 1d事件，且具有良好的全球可对比性；（2）薄片观察和陆源碎屑输入指标（Si/Al和Ti/Al）表明，研究区在OAE 1d期间，陆源碎屑输入增加，这可能与同期火山活动驱动的水文循环加快、大陆风化加剧密切相关；（3）Corg/P比值及草莓状黄铁矿研究表明，研究区在OAE 1d期间处于氧化-次氧化的沉积环境，与西欧地区有明显差异，揭示了古海洋氧化还原状态在OAE 1d期间的非均质展布；（4）研究区在OAE 1d期间的有机碳埋藏受制于氧化环境、强陆源碎屑输入及高沉积速率引发的稀释效应共同作用，致使藏南地区在该事件期间未能发育富有机质沉积，揭示了富有机质沉积物的沉积受全球气候背景与区域古环境条件的共同控制。【结论】东特提斯域藏南地区OAE 1d期间，独特的氧化-次氧化沉积环境以及缺乏富有机质沉积物等特征，凸显了全球大洋缺氧事件在区域沉积记录及古海洋环境响应方面的差异性，该成果对于全球大洋缺氧事件对比研究具有重要的借鉴意义。
Environmental Response to the Early Cretaceous Oceanic Anoxic Event 1d in the Eastern Tethyan: Paleoenvironmental Evidence from Southern Tibet
- Received Date:
2025-04-19
- Available Online:
2025-09-12
Abstract: Abstract: [Objective] The Oceanic Anoxic Event 1d (OAE 1d), took place during the late Albian of the Early Cretaceous, represents a significant perturbation in the global carbon cycle associated with a greenhouse climate. Although extensive research has been conducted on the characteristics and origin of OAE 1d in the western Tethys and North Atlantic regions, the paleoenvironmental response to this event in the eastern Tethys remains poorly understood. [Methods] This study focuses on the Lower Cretaceous Lengqingre Formation at the Youxia section in Dingri (southern Tibet) within the eastern Tethyan domain. Here, an integrated approach of mineralogical, petrological, sedimentological, isotopic, and elemental geochemical analyses, was employed to evaluated the paleoenvironmental response to OAE 1d and its distinction from coeval global patterns compared to contemporaneous global records. [Results] (1) Both bulk carbonate and organic carbon isotope data confirm that the Youxia section records the OAE 1d excursion, supporting the global signal of this phenomenon. (2) Thin-section observations and terrigenous input proxies (e.g., Si/Al and Ti/Al ratios) indicate enhanced input of siliciclastic materials during OAE 1d, likely linked to accelerated hydrological cycling and intensified continental weathering related to coeval volcanic activity. (3) Corg/P ratios and framboidal pyrite characteristics reveal that the Youxia section was deposited under oxic to suboxic bottom-water conditions during OAE 1d, markedly different from the anoxic conditions observed in the western Tethys. This highlights the spatial heterogeneity in marine redox conditions during this event. (4) The absence of organic carbon-rich sediments at Youxia is attributed to a combination of oxic environmental conditions, intense terrigenous input, and dilution effects induced by rapid sedimentation rates. This suggests that organic carbon burial was suppressed by regional environmental controls in the Dingri region during OAE 1d. [Conclusion] The oxic-suboxic conditions and lack of organic-rich sediments in the eastern Tethys during OAE 1d underscore the regional heterogeneity in sedimentary and oceanographic responses to global Oceanic Anoxic Events. These findings provide critical insights into complexity of paleoenvironmental feedbacks during global Oceanic Anoxic Events.
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