<b>: A novel GDGT-based proxy for reconstructing subsurface temperature in oceanic (sub-)tropical OMZs</b>

The TEX₈₆ proxy, based on the distribution of archaeal isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGT) in marine sediments, is widely utilized for reconstructing sea surface/subsurface temperatures. However, its application in oxygen minimum zones (OMZs) frequently yields substantial warm biases, underscoring the need for systematic evaluation of TEX₈₆ accuracy in low-oxygen environments. Here, we compiled a (sub-)tropical isoGDGT dataset from suspended particulate matter (SPM), surface sediments and sediment cores across OMZs and non-OMZs, alongside influencing parameters including temperature, dissolved oxygen, ammonia oxidation rates. Our analysis reveals substantial deviations between TEX₈₆-derived and in situ or export-layer temperatures, with offsets amplified under low-oxygen conditions. This highlights dissolved oxygen as a key factor influencing isoGDGT composition within the export layer. To address this bias, we propose a new OMZ-specific calibration, TEX₈₆_OMZs, optimized for subsurface temperature reconstructions. Validation against Holocene WOA data and foraminiferal δ¹⁸O-based paleotemperature records from the PETM and OAEs confirms its improved accuracy, providing a robust tool for paleotemperature reconstructions in low-oxygen marine environments.基于海洋沉积物中古菌类异戊二烯甘油二烷基甘油四醚（isoGDGT）分布的TEX₈₆代用指标（TEX₈₆ proxy），被广泛应用于海表及次表层海水温度的重建工作。然而，该指标在缺氧区（OMZs）的应用时常出现显著的暖偏差，这凸显了对低氧环境下TEX₈₆代用指标精度进行系统评估的必要性。本研究整合了横跨缺氧区与非缺氧区的悬浮颗粒物（SPM）、表层沉积物及沉积物岩芯中的（亚）热带类异戊二烯甘油二烷基甘油四醚数据集，并纳入温度、溶解氧、氨氧化速率等相关影响参数。分析结果显示，TEX₈₆反演温度与原位温度或输出层温度之间存在显著偏差，且在低氧环境下偏差进一步放大，这表明溶解氧是调控输出层内类异戊二烯甘油二烷基甘油四醚组成的关键因素。为修正这一偏差，我们提出了一种针对缺氧区的新校正方案TEX₈₆_OMZs，该方案专为次表层海水温度重建优化。通过全新世世界海洋图集（WOA）数据以及古新世-始新世极热事件（PETM）和大洋缺氧事件（OAEs）的有孔虫δ¹⁸O古温度记录进行验证，结果证实该校正方案的精度得到显著提升，可为低氧海洋环境的古温度重建提供可靠的研究工具。