Late Miocene Tidal Deposits in the Amazonian Foreland Basin

Abstract

Late Miocene tidal sediments of Acre, Brazilian Amazonia, were deposited in an embayment or interior seaway located in the sub-Andean zone. This late Tertiary embayment system may once have connected the Caribbean with the South Atlantic. The tidal coasts of the embayment-seaway have provided an avenue for the earliest waif (over water) dispersal phases of the great American biotic interchange in the late Miocene. The subsequent change from semimarine to terrestrial environments is of value in assessing the importance of earlier hypotheses on the evolution of the westem Amazonian landscape and gives insight into the formation of several observed biogeographic patterns, especially of aquatic biota.

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

“…The unconformity, below the Ipururo/Solimões Formation, has not been recognized by a few researchers (Räsänen et al 1995, Cozzuol et al 2006, Rebata 2006a, b, Silva 2001), yet it is widely recognized. It was mapped in various continental (Maia et al 1977), coastal (Rossetti et al 2001, Arai 2006 and marine (Figueiredo et al 2009(Figueiredo et al , 2010 areas of Brazil.…”

“…Many authors have interpreted plain or tenuous marine influence on outcrops and wells in the Solimões Formation (Hoorn 1993, Räsänen et al 1995, Webb 1996, Hovikoski et al 2003, 2005, Monsch 1998, among others), but some discard this possibility (Latrubesse et al 1997, 2007, 2010, Marshall & Lundberg 1996, Praxton et al 1996, Dino et al 2012, Riff et al 2010). The problem is that Repouso and Solimões Formations identification is misunderstood, and the sedimentary environments also depend on the stratigraphic level analyzed in environmental interpretation.…”

Historical Diversification of a Terra-Firme Forest Bird Superspecies: A Phylogeographic Perspective on the Role of Different Hypotheses of Amazonian Diversification

“…Several paleoecological studies indicate significant climatic and vegetational changes in eastern and central Amazonia during the last 60,000 years, with a return of wet conditions and associated rainforest expansion since the last glacial maximum (LGM), about 20,000 years ago (see reviews in Haffer 1997a; Burnham and Graham 1999). Therefore, populations of terra-firme species are expected to have experienced a sudden population expansion during the last 20,000 years, after a population bottleneck.The Miocene marine incursion hypothesis posits that diversification in Amazonia was caused by sea-level fluctuations throughout the Tertiary (Räsänen et al 1995;Webb 1995;Lovejoy et al 1998;Bates 2001). These marine invasions or embayments promoted an extensive flooding of the Amazon lowlands and the isolation of three large, higher land blocks at different places in the basin: the Guianan shield in the north, the Brazilian shield in the south, and the base of the eastern slope of the Andes in the west (Fig.…”

Tetraploidía en Ceratophrys (Anura, Leptodactylidae), análisis del registro fósil

“…Es decir que ya se haría sentir el cambio climático producido tanto por la elevación de la cordillera patagónica (Mioceno tardío), que frenaría los vientos húmedos del Pacífico incrementando paulatinamente las condiciones áridas de la zona, como la apertura del pasaje de Drake y la formación de la corriente circumpolar antártica, trayendo como consecuencia la modificación de patrones de circulación atmosférica y oceánica (BÁEZ, 1986). A esto se sumaría la impresionante transgresión marina (Mioceno medio al Plioceno) que ocupó las zonas bajas y precordilleranas del continente sudamericano (NE de la Patagonia, llanura Chaco-pampeana y Mesopotamia (del territorio argentino), Paraguay, Bolivia, Norte de Perú, Colombia y Venezuela) (RÄSÄNEN et al, 1995).…”