Eustatic and tectonic change effects in the reversion of the transcontinental Amazon River drainage system

Abstract

The development of the transcontinental Amazon River System involved geological events in the Andes Chain; Vaupés, Purus and Gurupá arches; sedimentary basins of the region and sea level changes. The origin and age of this river have been discussed for decades, and many ideas have been proposed, including those pertaining to it having originated in the Holocene, Pleistocene, Pliocene, Late Miocene, or even earlier times. Under this context, the geology of the sedimentary basins of northern Brazil has been analyzed from the Mesozoic time on, and some clarifications are placed on its stratigraphy. Vaupés Arch, in Colombia, was uplifted together with the Andean Mountains in the Middle Miocene time. In the Cenozoic Era, the Purus Arch has not blocked this drainage system westward to marine basins of Western South America or eastward to the Atlantic Ocean. Also the Gurupá Arch remained high up to the end of Middle Miocene, directing this drainage system westward. With the late subsidence and breaching of the Gurupá Arch and a major fall in sea level, at the beginning of the Late Miocene, the Amazon River quickly opened its pathway to the west, from the Marajó Basin, through deep headward erosion, capturing a vast drainage network from cratonic and Andean areas, which had previously been diverted towards the Caribbean Sea. During this time, the large siliciclastic influx to the Amazon Mouth (Foz do Amazonas) Basin and its fan increased, due to erosion of large tracts of South America, linking the Amazon drainage network to that of the Marajó Basin. This extensive exposure originated the Late Miocene (Tortonian) unconformity, which marks the onset of the transcontinental Amazon River flowing into the Atlantic Ocean.

Peer Review #1 of "A Pan-Amazonian species delimitation: high species diversity within the genus Amazophrynella (Anura: Bufonidae) (v0.1)"

“…In general, however, marine incursions remain largely untested as a diversifying force (Noonan & Wray, 2006;Garda & Cannatella, 2007;Antonelli et al, 2009). In addition, it is reported that in early Miocene, the Purus arch was still active, and was a prominent landscape feature in central Amazon (Wesselingh & Salo, 2006;Figueiredo et al, 2009;Caputo & Soares, 2016) thus this geological formation also could explain the east-west pattern as well. While other hypotheses, such as Pleistocene refugia have also been proposed to explain this east-west pattern of diversity (Pellegrino et al, 2011), the Miocene marine incursions have the best temporal concordance with the basal east-west divergence pattern observed in Amazophrynella and other Amazonian anuran groups.…”

Piezometric Behavior in the Amazonian Lateritic Plateaus: Implications of Climate Changes to the Recharge of the Alter do Chão Aquifer System

“…It consists of an exposed area that continues underground to the West, under the Içá and Solimões formations [30]. The Alter do Chão Formation is represented by the fluvio-lacustrine and fluvial deposits of Cenozoic age [31], consisting of medium to coarse sandstone with clay fragments, medium to coarse caulinitic sandstone, fine sandstone, massif mudstone interbedded with thin to medium sandstone and mudstone.…”

Exploring The Biogeography Of South American Rainforest Understory Birds Using Morphological Variation In The Wedge-Billed Woodcreeper (glyphorynchus Spirurus)

“…Atlantic incursions are believed to have followed the present course of the Amazon (Nores 1999, Hubert andRenno 2006) and must have either been of exceptional size (as described in Nores 1999 but not supported in recent literature as explained below) or taken place after the Amazon's course had developed, due to geological barriers at earlier time periods (Caputo and Amaral 2016). The existence of such east-west incursions is disputed in Rossetti et al (2005).…”

“…Another paleogeography model, the lake model, states that tectonic activity caused a downwarping of part of the Amazon Basin, resulting in a large lake covering much of the western and central portions of Amazonia and having at various times an outlet either to the north through the Orinoco River or to the east through the current mouth of the Amazon (Frailey et al 1988). The current outlet and east-west orientation of the Amazon is believed to have arisen only at the end of the Miocene (Figueiredo et al 2009, Caputo andAmaral 2016). Such a lake would have separated the Brazilian and Guianan Shields in the east, made up of Precambrian rock, from the newly raised Andes in the west for much of the Miocene, with lakes or seas separating the two shields as well, resulting in differentiation of organisms in all three areas (Aleixo and Rossetti 2007).…”