Abstract
The Pirabas Formation of Early Miocene age represents the final stage of the central western Atlantic carbonate platform in northeastern South America, predating the emplacement of the Amazon delta system. The otolith-based fossil fish fauna is represented by 38 species typical of a shallow marine environment. A total of 18 species are described new to science from the families Congridae, Batrachoididae, Bythitidae, Sciaenidae and Paralichthyidae. The fish fauna was associated with high benthic and planktic primary productivity including seagrass meadows, calcareous algae and suspension-feeders. The break of todays shallow marine bioprovince at the Amazonas delta mouth is not evident from the fish fauna of the Pirabas Fm., which shows good correlation with the Gatunian/proto-Caribbean bioprovince known from an only slightly younger time window in Trinidad and Venezuela. Differences observed to those Early Miocene faunal associations are interpreted to be mainly due to stratigraphic and geographic and not environmental differences. We postulate that the emergence of the Amazonas river mouth close to its present day location has terminated the carbonate cycle of the Pirabas Fm. and pushed back northwards a certain proportion of the fish fauna here described.
Highlights
Nepomuceno). (e.g. Aguilera and Lundberg, 2010; Lundberg et al, 2010; Aguilera et al, 2013b, c), the existence and timing of marine incursions (e.g. Hoorn, 1993, 1994; Hoorn et al, 2010), the timing and rate of uplift of the Andes and its relation to the geographic, topographic and hydrographic changes in western South America (Rod, 1981; Díaz de Gamero, 1996; Hoorn et al, 2010; Figueiredo et al, 2009; Shephard et al, 2010), the oceanographic changes in relation to the closure of the Central American Seaway (Leigh et al, 2013; Jackson and O0Dea, 2013) and the origin of the modern-day Amazon River (Heinrich and Zonneveld, 2013). We contribute to this discussion with a paleobiological analysis or the teleostean fish fauna reconstructed from otolith assemblages from the Pirabas Formation (Fm.) of eastern Amazon
Discussion e yBagre protocaribbeanus is known from the lower Miocene Cantaure and Castillo formations in Venezuela, and lower Miocene Castilletes Formation in Colombia (Aguilera et al, 2013a)
Porichthys atalaianus belongs to the second group, which in the Recent is mostly known from the Pacific shores of tropical America for instance P. greenei Gilbert and Starks, 1905, P. margaritatus (Richardson, 1844), P. mimeticus Walter and Rosenblatt, 1988 and P. plectrodon Jordan and Gilbert, 1882
Summary
The knowledge of the seascape of Tropical America during the Neogene has increased significantly over the last two decades, with respect to the ancient Western Amazonas hydrographic system (Hoorn et al, 2010), the large and biodiverse Proto Amazonian e Orinoquian fauna from the Urumaco trench of northwestern Venezuela (Sanchez-Villagra et al, 2010), the Huila Group in the upper Magdalena Valley of Colombia (Kay et al, 1997) and the Acre region in the western Amazon of Brazil (Hoorn et al, 2010). Hoorn, 1993, 1994; Hoorn et al, 2010), the timing and rate of uplift of the Andes and its relation to the geographic, topographic and hydrographic changes in western South America (Rod, 1981; Díaz de Gamero, 1996; Hoorn et al, 2010; Figueiredo et al, 2009; Shephard et al, 2010), the oceanographic changes in relation to the closure of the Central American Seaway (Leigh et al, 2013; Jackson and O0Dea, 2013) and the origin of the modern-day Amazon River (Heinrich and Zonneveld, 2013) We contribute to this discussion with a paleobiological analysis or the teleostean fish fauna reconstructed from otolith assemblages from the Pirabas Formation (Fm.) of eastern Amazon. The purpose of this study further is a detailed taxonomic description of Teleostean fish otoliths from the Pirabas Fm. of the pre-Amazon Delta, and an evaluation of their paleoenvironment and the paleogeographic implications
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