Paleoenvironmental Model for the Late Cenozoic of Southwestern Amazonia: Paleontology and Geology

Abstract

-Our study provides paleontological and geological data substantiating a paleoenvironmental model for the upper Miocene-Pliocene of Southwestern Amazonia. The extensive Late Tertiary sediments of The Solimões Formation, outcropping in Southwestern Amazonia, were deposited by a complex megafan system, originating in the high Peruvian Andes. The megafan system was the sedimentological response to the Andean Quechua tectonic phase of Tertiary age, producing sediments that fdled the foreland basin of Southwestern Amazonia. Occurrences of varied vertebrate fossil assemblages of the HuayquerianMontehermosan Mammal age collected in these sediments support this interpretation. The fauna includes several genera and species of fishes, reptiles, birds, mammals and appears to be one that could have lived in or near a riverine habitat. In the Late Pliocene, the megafan system became inactive as a result of the influence of the Diaguita Tectonical Phase.

The emerging field of geogenomics: Constraining geological problems with genetic data

“…Latrubesse and coworkers (Latrubesse et al, 1997(Latrubesse et al, , 2007(Latrubesse et al, , 2010 conclude that trans-Amazon drainage occurred sometime between 6.5 and 5 Ma, soon after deposition of the Solimões Formation ceased in the Solimões basin of the western Brazilian Amazon. Leguizamon Vega et al (2006) used sedimentological evidence to conclude that the Purus Arch was an effective barrier to eastward, transcontinental Amazon drainage until at least the late Miocene.…”

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

“…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.…”

Climatically controlled river terrace staircases: A worldwide Quaternary phenomenon

“…Examples of terrace sequences in tropical regions for which aridity/humidity cycles are envisaged as principal forcing factors include the Amazon, in Brazil (Latrubesse et al, 1997), and the Niger, in the Niger Republic (e.g. Dubois et al, 1984;Oussini and Morel, 1989).…”