Abstract
ABSTRACT We review geological evidence on the origin of the modern transcontinental Amazon River, and the paleogeographic history of riverine connections among the principal sedimentary basins of northern South America through the Neogene. Data are reviewed from new geochronological datasets using radiogenic and stable isotopes, and from traditional geochronological methods, including sedimentology, structural mapping, sonic and seismic logging, and biostratigraphy. The modern Amazon River and the continental-scale Amazon drainage basin were assembled during the late Miocene and Pliocene, via some of the largest purported river capture events in Earth history. Andean sediments are first recorded in the Amazon Fan at about 10.1-9.4 Ma, with a large increase in sedimentation at about 4.5 Ma. The transcontinental Amazon River therefore formed over a period of about 4.9-5.6 million years, by means of several river capture events. The origins of the modern Amazon River are hypothesized to be linked with that of mega-wetland landscapes of tropical South America (e.g. várzeas, pantanals, seasonally flooded savannahs). Mega-wetlands have persisted over about 10% northern South America under different configurations for >15 million years. Although the paleogeographic reconstructions presented are simplistic and coarse-grained, they are offered to inspire the collection and analysis of new sedimentological and geochronological datasets.
Highlights
The principle of uniformitarianism avers “the present is the key to the past”, asserting the universality of natural laws and processes across space and through time
In these sciences the reverse is often just as important, where the current state of a geological or biological system can only be fully understood in light of conditions as they were in the past (Webb et al, 2002; Fine, Ree, 2006; Kissling et al, 2012; Albert, Antonelli, 2017)
Mega-river captures at the scale of sedimentary basins allowed taxa originating in the Western Amazon to disperse into the Eastern Amazon, Essequibo, and Parana drainages (Albert et al, 2011a; Dias et al, 2014; Evans et al, 2017a), and isolated taxa in the trans-Andean, Llanos, and Upper Madeira regions (Albert et al, 2006; Albert et al, 2011a; Tagliacollo et al, 2015)
Summary
The changing course of the Amazon River in the Neogene: center stage for Neotropical diversification. We review geological evidence on the origin of the modern transcontinental Amazon River, and the paleogeographic history of riverine connections among the principal sedimentary basins of northern South America through the Neogene. The origins of the modern Amazon River are hypothesized to be linked with that of mega-wetland landscapes of tropical South America (e.g. várzeas, pantanals, seasonally flooded savannahs). Este trabalho é uma revisão das evidências geológicas sobre a origem do moderno rio Amazonas transcontinental, e a história paleogeográfica das conexões ribeirinhas entre as principais bacias sedimentares do norte da América do Sul durante o Neógeno. Os sedimentos andinos são registrados pela primeira vez no leque fluvial do Amazonas por volta de 10,1-9,4 Ma, com um grande aumento na sedimentação a cerca de 4,5 Ma. O rio Amazonas transcontinental, portanto, se formou durante um período de cerca de 4,9 a 5,6 milhões de anos, por meio de vários eventos de captura de rios. Palavras-chave: Amazonas transcontinental, Bioestratigrafia, Captura de rio, Geocronologia, Modelos de evolução de paisagem
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