Abstract The mid-Piacenzian Warm Period (mPWP, 3.264–3.025 Ma) of the Pliocene epoch has been proposed as an analog for future climate scenarios. Disagreement between the paleoenvironmental reconstruction and model simulations of the climate in subtropical regions for this period suggests that more investigation of the subtropical climate variability of the mPWP is needed. This study presents pollen, microcharcoal and benthic foraminifera oxygen isotope records generated from marine sediment cores of International Ocean Discovery Program (IODP) Exp. 361 Site U1479 from the Cape Basin offshore of South Africa for the period between 3.337 and 2.875 Ma. With an average sample resolution of 3 ka, this record represents the highest-resolution record of mPWP vegetation change from the region. Our results indicate that the vegetation during the mPWP was dominated by fynbos (species-rich heathy vegetation in the Cape Floristic Region) with variable proportions of Ericaceae. Moreover, the development of the Afrotemperate forest (tall, multilayered indigenous forests in South Africa) reflects shifts in the amounts of precipitation between winter and summer in the year-round rainfall zone. The vegetation variation is probably influenced by the latitudinal insolation gradient in response to precession forcing. Several glacials depicted by the benthic foraminifera oxygen isotope record were characterized by lower percentage values of Restionaceae, higher percentage values of ericoid fynbos and Afrotemperate forest. These events correspond well with cooler SE Atlantic sea surface temperatures driven by interactions of both atmospheric and oceanographic processes. The cooler sea surface temperatures attributed to Antarctic ice sheet expansion, reduced Agulhas leakage (heat and salt transfer from the Indian Ocean to the Atlantic Ocean) and/or intensified southern Benguela upwelling, resulted in less precipitation in the winter rainfall zone of South Africa.

中文翻译：

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皮亚琴察中期暖期中南非亚热带的水文气候变化

摘要 上新世中期皮亚琴察暖期 (mPWP, 3.264–3.025 Ma) 已被提议作为未来气候情景的模拟。这一时期亚热带地区气候的古环境重建和模型模拟之间的分歧表明需要对 mPWP 的亚热带气候变异进行更多的调查。本研究提供了从国际海洋发现计划 (IODP) Exp. 的海洋沉积物核心产生的花粉、微炭和底栖有孔虫氧同位素记录。来自南非近海开普盆地的 361 站点 U1479，时间为 3.337 至 2.875 Ma。该记录的平均样本分辨率为 3 ka，代表了该地区 mPWP 植被变化的最高分辨率记录。我们的结果表明，mPWP 期间的植被以 fynbos（开普植物区物种丰富的健康植被）为主，具有不同比例的杜鹃花科。此外，非洲温带森林（南非高大的多层土著森林）的发展反映了全年降雨区冬季和夏季降水量的变化。植被变化可能受进动强迫响应的纬度日照梯度的影响。底栖有孔虫氧同位素记录所描绘的几个冰川的特征在于，Restionaceae 的百分比值较低，Ericoid fynbos 和 Afrotemperate 森林的百分比值较高。这些事件与由大气和海洋过程相互作用驱动的较冷的东南大西洋海面温度很好地对应。由于南极冰盖扩张、厄加勒斯渗漏减少（从印度洋到大西洋的热量和盐分转移）和/或本格拉南部上升流加剧，导致海面温度降低，导致南非冬季降雨区的降水减少。