The expansion of C₄ vegetation during the Neogene was one of the largest reorganizations of Earth's terrestrial biome. Once thought to be globally synchronous in the late Miocene, site-specific studies have revealed differences in the timing of the expansion and suggest that local conditions play a substantial role. Here, we examine the expansion of C₄ vegetation on the Indian Peninsula since the late Miocene by constructing a ∼6-million-year paleorecord with marine sediment from the Bay of Bengal at Site U1445, drilled during International Ocean Discovery Program Expedition 353. Analyses of element concentrations indicate that the marine sediment originates from the Mahanadi River in the Core Monsoon Zone (CMZ) of the Indian Peninsula. Hydrogen isotopes of the fatty acids of leaf waxes reveal an overall decrease in the CMZ precipitation since the late Miocene. Carbon isotopes of the leaf wax fatty acids suggest C₄ vegetation on the Indian Peninsula existed before the end of the Miocene but expanded to even higher abundances during the mid-Pliocene to mid-Pleistocene (∼3.5 to 1.5 million years ago). Similar to the CMZ on the Indian Peninsula, a Pliocene expansion or re-expansion has previously been observed in northwest Australia and in East Africa, suggesting that these tropical ecosystems surrounding the Indian Ocean remained highly sensitive to changes in hydroclimate after the initial spread of C₄ plants in late Miocene.

中文翻译：

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印度半岛核心季风区C ₄植被的上新世扩张

在新近纪期间，C ₄植被的扩张是地球陆地生物群落最大的重组之一。在中新世晚期曾被认为是全球同步的，但针对特定地点的研究揭示了扩张时间的差异，并表明当地条件起着重要作用。在这里，我们通过构造一个〜6来研究中新世晚期以来印度半岛C ₄植被的扩展。在国际海洋发现计划远征353期间钻探的具有百万年古记录的孟加拉湾U1445站点海洋沉积物。对元素浓度的分析表明，海洋沉积物起源于孟加拉国核心季风区（CMZ）的马哈纳迪河。印度半岛。自中新世晚期以来，叶蜡脂肪酸的氢同位素显示出CMZ降水的总体下降。叶蜡脂肪酸的碳同位素表明，印度半岛上的C ₄植被存在于中新世末期之前，但在上新世中期至中新世中期扩展至更高的丰度（〜3.5）到150万年前）。与印度半岛上的CMZ相似，以前在澳大利亚西北部和东非曾观察到上新世扩张或再扩张，这表明印度洋周围的这些热带生态系统在C最初扩散后仍对水文气候的变化高度敏感。中新世晚期有₄种植物。