Department of Earth and Climate Science, Indian Institute of Science Education and Research Pune, Pune, 411008, India.
Department of Geological Sciences, California State University, Bakersfield, CA, 93311, USA.
Sci Rep. 2019 Jul 12;9(1):10125. doi: 10.1038/s41598-019-46253-1.
The formation of the Antarctic Circumpolar Current (ACC) is critical for the evolution of the global climate, but the timing of its onset is not well constrained. Here, we present new seismic evidence of widespread Late Eocene to Oligocene marine diagenetic chert in sedimentary drift deposits east of New Zealand indicating prolonged periods of blooms of siliceous microorganisms starting ~36 million years ago (Ma). These major blooms reflect the initiation of the arrival and upwelling of northern-sourced, nutrient-rich deep equatorial Pacific waters at the high latitudes of the South Pacific. We show that this change in circulation was linked to the initiation of a proto-ACC, which occurred ~6 Ma earlier than the currently estimated onset of the ACC at 30 Ma. We propose that the associated increased primary productivity and carbon burial facilitated atmospheric carbon dioxide reduction contributing to the expansion of Antarctic Ice Sheet at the Eocene-Oligocene Transition.
南极环极流（ACC）的形成对全球气候的演变至关重要，但它的起始时间还没有得到很好的限制。在这里，我们提出了新的地震证据，表明在新西兰东部的沉积漂移沉积物中存在广泛的晚始新世至渐新世海洋成岩硅质燧石，这表明从大约 3600 万年前开始，硅质微生物的大量繁殖持续了很长一段时间。这些大量繁殖反映了富含营养的北源深层赤道太平洋水在南太平洋高纬度地区到达和上升的开始。我们表明，这种环流的变化与原南极环极流的开始有关，原南极环极流的开始比目前估计的南极环极流在 3000 万年前开始早了约 600 万年前。我们提出，相关的初级生产力增加和碳埋藏促进了大气二氧化碳的减少，这有助于在始新世-渐新世过渡期扩大南极冰盖。
