2024年6月24日出版的《自然—地球科学》杂志发表了澳大利亚国立大学Amarathunga, Udara研究组的最新成果，他们最新的研究显示，上新世中期的冰期之前是50万年的北非湿润期。

据悉，在过去的北非湿润期，由于非洲热带雨带的向北迁移，撒哈拉沙漠上的植被扩大，为人类开辟了迁徙通道。通常，这些与岁差同步的湿润期在15,000年因雨带退缩结束。在北非湿润期，地中海东部富含有机物的腐石层至少从8Myr前就开始沉积。

研究人员将气候模拟与古气候代理数据相结合，以表明5.3-3.3Myr期间腐泥保存作用减弱是由于营养径流限制造成的，营养径流限制相对于上新世中期(3.3-3.0Myr，当冰川强度增加时)持续偏北的非洲季风锋导致的北非植被增强有关。此外，在3.8-3.3Myr最高产量期腐泥的缺失与整个北非最大的季风径流和广泛潮湿的植被条件相吻合。

模型结果表明，这个0.5Myr跨度的泛北非湿润期结束于约3.3Myr。随着北半球冰川的加强，季风锋面向南移动。3.8-3.3Myr湿润期与已知最早的人类在北非东部和中部共存的证据相吻合。研究人员推测，在这个潮湿阶段，持续的绿色走廊促进了早期人类的联系和迁徙，扩大了他们在更广阔的北非领土上的栖息地范围。

附：英文原文

Title: Mid-Pliocene glaciation preceded by a 0.5-million-year North African humid period

Author: Amarathunga, Udara, Rohling, Eelco J., Grant, Katharine M., Francke, Alexander, Latimer, James, Klaebe, Robert M., Heslop, David, Roberts, Andrew P., Hutchinson, David K.

Issue&Volume: 2024-06-24

Abstract: Past North African humid periods caused expanded vegetation over the Sahara, due to northward tropical African rainbelt displacement, opening migration pathways for hominins. Commonly, these precession-timed humid periods ended within 15,000years due to rainbelt retreat. During North African humid periods, eastern Mediterranean organic-rich layers called sapropels were deposited at least since 8Myr. Here we combine climate modelling with palaeoclimate proxy data to show that weakened sapropel preservation during the 5.3–3.3Myr period resulted from nutrient runoff limitation associated with enhanced North African vegetation cover due to a persistently more northward-located African monsoon front, relative to the mid-Pliocene (3.3–3.0Myr, when glacial intensity increased). Moreover, sapropel absence within the 3.8–3.3Myr period coincided with maximum monsoon runoff and extensively humid, vegetated conditions throughout North Africa. Our model results indicate that this 0.5-Myr-long pan-North African humid period ended at ~3.3Myr because of southward monsoon front displacement with Northern Hemisphere glacial intensification. The 3.8–3.3Myr humid period coincided with the earliest known evidence for hominin coexistence over eastern and central North Africa. We posit that persistent green corridors during this humid phase facilitated early hominin connectivity and migration, expanding their habitat range over the wider North African territory.

DOI: 10.1038/s41561-024-01472-8

Source: https://www.nature.com/articles/s41561-024-01472-8