(Table 1) TOC content, BIT, TEX86 and UK'37 indices, and sea surface temperature reconstruction for the middle Miocene to Pliocene of ODP Hole 175-1085A@en

The initiation of the Benguela upwelling has been dated to the late Miocene, but estimates of its sea surface temperature evolution are not available. This study presents data from Ocean Drilling Program (ODP) Site 1085 recovered from the southern Cape Basin. Samples of the middle Miocene to Pliocene were analyzed for alkenone-based (UK'37, SSTUK) and glycerol dialkyl glycerol tetraether (GDGT) based (TEX86, TempTEX) water temperature proxies. In concordance with global cooling during the Miocene, SSTUK and TempTEX exhibit a decline of about 8°C and 16°C, respectively. The temperature trends suggest an inflow of cold Antarctic waters triggered by Antarctic ice sheet expansion and intensification of Southern Hemisphere southeasterly winds. A temperature offset between both proxies developed with the onset of upwelling, which can be explained by differences in habitat: alkenone-producing phytoplankton live in the euphotic zone and record sea surface temperatures, while GDGT-producing Thaumarchaeota are displaced to colder subsurface waters in upwelling-influenced areas and record subsurface water temperatures. We suggest that variations in subsurface water temperatures were driven by advection of cold Antarctic waters and thermocline adjustments that were due to changes in North Atlantic deep water formation. A decline in surface temperatures, an increased offset between temperature proxies, and an increase in primary productivity suggest the establishment of the Benguela upwelling at 10 Ma. During the Messinian Salinity Crisis, between 7 and 5 Ma, surface and subsurface temperature estimates became similar, likely because of a strong reduction in Atlantic overturning circulation, while high total organic carbon contents suggest a “biogenic bloom.” In the Pliocene the offset between the temperature estimates and the cooling trend was reestablished.本格拉上升流的启动时间可追溯至中新世晚期，但目前尚无其海面温度演化的相关估算数据。本研究采用了从开普敦盆地南部钻取的大洋钻探计划（Ocean Drilling Program, ODP）1085站位的样品数据，对中新世中期至上新世的样品开展了基于烯酮类化合物（alkenone）的温度代用指标（UK'37、SSTUK）以及基于甘油二烷基甘油四醚（glycerol dialkyl glycerol tetraether, GDGT）的温度代用指标（TEX86、TempTEX）分析。与中新世全球降温趋势一致，SSTUK与TempTEX分别呈现约8℃与16℃的降温幅度。上述温度变化趋势表明，南极冰盖扩张与南半球东南风增强驱动了南极冷水的涌入。两种代用指标间的温度差值随上升流启动而显现，这可通过生境差异解释：产烯酮类的浮游植物栖息于真光层，记录海面温度；而产GDGT的奇古菌（Thaumarchaeota）在受上升流影响的区域会迁移至温度更低的次表层水体，从而记录次表层水温。我们认为，次表层水温的变化由南极冷水平流以及由北大西洋深水形成变化引发的温跃层调整所驱动。海面温度下降、温度代用指标间差值增大以及初级生产力提升，均表明本格拉上升流于10 Ma时正式建立。在7 Ma至5 Ma期间的墨西拿盐度危机（Messinian Salinity Crisis）阶段，海面与次表层水温估算值趋于一致，这大概率是因为大西洋翻转环流大幅减弱；而总有机碳含量升高则表明该时期出现了"生物勃发"。上新世时期，水温估算值间的差值与降温趋势再度恢复。