Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancon, Republic of Panama.
University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Sci Adv. 2017 May 3;3(5):e1601693. doi: 10.1126/sciadv.1601693. eCollection 2017 May.
There is a considerable controversy about whether western Amazonia was ever covered by marine waters during the Miocene [23 to 5 Ma (million years ago)]. We investigated the possible occurrence of Miocene marine incursions in the Llanos and Amazonas/Solimões basins, using sedimentological and palynological data from two sediment cores taken in eastern Colombia and northwestern Brazil together with seismic information. We observed two distinct marine intervals in the Llanos Basin, an early Miocene that lasted ~0.9 My (million years) (18.1 to 17.2 Ma) and a middle Miocene that lasted ~3.7 My (16.1 to 12.4 Ma). These two marine intervals are also seen in Amazonas/Solimões Basin (northwestern Amazonia) but were much shorter in duration, ~0.2 My (18.0 to 17.8 Ma) and ~0.4 My (14.1 to 13.7 Ma), respectively. Our results indicate that shallow marine waters covered the region at least twice during the Miocene, but the events were short-lived, rather than a continuous full-marine occupancy of Amazonian landscape over millions of years.
关于上新世（2300 万至 500 万年前）期间是否有海洋水域覆盖西亚马逊地区，存在相当大的争议。我们利用从哥伦比亚东部和巴西西北部采集的两个岩芯中的沉积学和孢粉学数据以及地震信息，研究了上新世期间海洋可能侵入拉兰诺斯盆地和亚马孙/索利蒙伊斯盆地的情况。我们在拉兰诺斯盆地观察到两个截然不同的海洋间隔期，一个是持续约 0.9 百万年（1810 万至 1720 万年前）的早中新世，另一个是持续约 3.7 百万年（1610 万至 1240 万年前）的中中新世。这些两个海洋间隔期也见于亚马孙/索利蒙伊斯盆地（西北亚马逊地区），但持续时间更短，分别为约 0.2 百万年（1800 万至 1780 万年前）和约 0.4 百万年（1410 万至 1370 万年前）。我们的研究结果表明，上新世期间，浅海水域至少两次覆盖该地区，但这些事件持续时间短，而不是亚马逊地貌在数百万年期间持续完全被海水占据。
