...Mark J. Johnsson; Robert H. Meade Abstract Modification of sediment composition by chemical weathering depends both on the overall intensity of weathering and on its duration. At Macuapanim Island, Solimboes River (Amazon main channel), Brazil, a number of alluvial deposits have been exposed...

...Figure 1. (A) Study area on the Solimões River, Brazil, with bank and bar lines from 1967 Corona satellite imagery (yellow lines) superimposed on 2021 PlanetScope imagery, showing varying migration rates between left and right bank. Colored points denote measurement locations along the 100 km...

... including Fourier transform infrared spectroscopy (FT-IR), electron paramagnetic resonance (EPR) and potentiometric measurements. Particulate and colloidal matter are organo-mineral and organic, respectively. Signatures of the particulate fractions distinguish Rio Amazonas/Rio Solimoes rivers...

... are proposed. The samples from the Solimões Formation contain the following taxa: Mediaverrunites elsikii , Mediaverrunites mulleri , Monoporisporites sp., Fusiformisporites crabbii , and Multicellites cingulatus . The presence of these suggests river channel margins colonized by freshwater vegetation, where...

... event in Western Amazonia during the Neogene. These onshore records are compared with three offshore cores from the Atlantic and Pacific Oceans. The similarity between microfossil assemblages of the Solimões Basin and the Caribbean Sea, and evidence of increased runoff from the Orinoco river drainage...

... extinctions over evolutionary time, and thus measure rates of diversification (origination versus extinction). Amazonia palynology Miocene Holocene Solimões Formation floristic diversity The modern landscape of Amazonia, including the Amazon River, was established by the late Miocene...

... the Solimões and Içá Formations in Coari ( Figure 3 ; Nogueira et al. 2013 ; Silveira and Souza 2015 ). Figure 3. Correlation of sections discussed in the text. From left to right: (a) Solimões Formation cores in the upper Solimões River (Hoorn et al. 1993 ; Silva Caminha et al. 2010 ; Kachniasz...

... The trunk stream of the Amazon River in Brazil is formed by three main tributaries, which are the Solimões, draining the central Andes, the Negro River draining the Guyana Shield, and the Madeira River, a mixed load river draining the Bolivian and Peruvian Andes and the Brazilian Shield (see Fig. 1...

... also re-studied the palynology of the Patos outcrop in the upper Acre River (10°55’S, 69°5’20”W) ( Figure 2 ) that had been studied by Latrubesse et al. ( 2007 , 2010 ). Patos is a ∼30 m high outcrop of the Solimões Formation in a river bank cut; the lower part bears a rich vertebrate fauna (Cozzuol...

... of the Amazon and therefore its biogeography and possibly biodiversity. Herein we present palynological and lithostratigraphical results from the Solimões Formation in the well 1AS-33-AM. It was drilled in the Solimões Basin, Amazonas State, Brazil, reaching 405 m in depth. We identified 152 palynomorphs, in 32...

... has been hampered by limited outcrop exposure. Also, ichnological data largely have been ignored. This study focuses on ichnological and sedimentological relationships observed in outcropping strata of the Solimoes Formation (Middle Miocene) along the Acre River in western Brazil and northern Bolivia...

... tributaries draining the basic and metamorphic rocks from the southeastern Guiana Shield, and strongest influence of the upstream Amazon and Solimoes areas. These source signals are damped by transitional storage and intense lateral sediment exchange between channel and floodplain. The Brazilian Shield...

... and Fk suggest that unstable minerals like feldspars do not suffer any loss during stream transport probably due to short river distance. Johnson and Meade (1990) examined the sediments of Solimoes River in Brazil and documented that longer the duration of sediment storage in alluvial environment, better...