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Marine influence in western Amazonia during the late Miocene
Global and Planetary Change ( IF 3.9 ) Pub Date : 2021-08-10 , DOI: 10.1016/j.gloplacha.2021.103600
Bruno S. Espinosa 1 , Carlos D'Apolito 1 , Silane A.F. da Silva-Caminha 1
Affiliation  

The dynamic environments of western Amazonia during the Neogene (23 to 2.58 million years ago [Ma]) included continental-scale wetlands that were episodically influenced by marine incursions originating from the Caribbean. The nature and frequency of such events is highly debated, with a general consensus on short events during the early (23 to 16) and middle (16 to 11.6 Ma) Miocene. However, scattered evidence for more events up until the late Miocene (11.6 to 5.3 Ma) exists. Based on a palynological analysis of borehole 1-AS-9-AM from the Solimões Formation (western Amazonia, Brazil), we provide further support for late Miocene marine influence in the region. Comparisons with other sites in the Solimões Basin indicate an age of earliest Tortonian (~11–10 Ma) for an assemblage with foraminiferal linings, acritarchs and dinocysts, totalling ~17.3% of the palynological count (n = 374 palynomorphs) at 34.10 m of depth. This is the topmost sample with a significant amount of marine indicators and its age is consistent even when different biostratigraphic interpretations are appreciated. Our data and comparisons also show that a larger proportion of sediments of the Solimões Formation should be placed within the late middle to early late Miocene. Our reconstruction of the Solimões deposits in the early Tortonian indicates intermintent low salinity regimes and a persistent connection with the paleo-Orinoco drainage until the closure of this connection in the late Miocene to Pliocene times.



中文翻译:

中新世晚期对亚马逊西部的海洋影响

新近纪(23 至 258 万年前 [Ma])期间亚马逊西部的动态环境包括大陆尺度的湿地,这些湿地受到来自加勒比海的海洋入侵的影响。此类事件的性质和频率引起了高度争议,对早(23 至 16 年)和中期(16 至 11.6 马)中新世的短事件达成了普遍共识。然而,直到中新世晚期(11.6 至 5.3 Ma)为止,存在更多事件的零星证据。基于对 Solimões 地层(巴西亚马逊河流域西部)钻孔 1-AS-9-AM 的孢粉学分析,我们为该地区晚中新世海洋影响提供了进一步的支持。与 Solimões 盆地其他地点的比较表明,最早的 Tortonian 时代(~11-10 Ma)与有孔虫衬里、acritarchs 和 dinocysts 的组合共约 17 年。n  = 374 个孢粉型),深度为 34.10 m。这是具有大量海洋指标的最高样本,即使在不同的生物地层解释受到赞赏时,其年龄也是一致的。我们的数据和比较还表明,Solimões 组的较大比例的沉积物应位于中新世晚期至晚中新世早期。我们对托尔托阶早期 Solimões 矿床的重建显示出间歇性低盐度状态和与古奥里诺科河流域的持续联系,直到中新世晚期至上新世时期这种联系关闭。

更新日期:2021-08-13
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