Range extensions and biogeographic implications of Chilean Neogene mollusks found in Peru

Abstract

Thirty species of marine mollusks once known only from the Lower to Middle Miocene Navidad Group and Pliocene marine terraces of central Chile are reported from forearc basins of south-central Peru. Well preserved microfossils, particularly diatoms and foraminifera, and volcanic ash interbedded with mollusk-bearing sandstones in Peru provide temporal control for the ranges of these species. Few Early Miocene species are found in both Chile and Peru, despite the tropical cast of the more southerly Chilean fauna. A greater proportion of Pliocene species are common to both countries, but with more tropical taxa found in Peruvian deposits. Differences between the Peruvian and Chilean faunas may be explained by latitudinal thermal gradients that changed as coastal upwelling intensity and southern ocean temperatures changed through the Neogene.