Western South America and Antarctica

New constraints on the Jurassic–Cretaceous boundary in the High Andes using high-precision U–Pb data

“…This assumption is in a strong discrepancy with the Tithonian age assumed by all the paleontological studies on ammonites of this unit (Leanza, 1980(Leanza, , 1981Riccardi, 2008;Riccardi et al, 1992Riccardi et al, , 2000Zeiss and Leanza, 2010, among many others).…”

“…In particular, the Jurassic−Early Cretaceous ammonite zonation in the Neuquén Basin of west central Argentina, through more than a century of paleontological studies, shows a correlation not only with the northern hemisphere but also all along the Circum-Pacific realm (Leanza, 1981;Riccardi, 1991Riccardi, , 2008Riccardi et al, 1992;Aguirre-Urreta et al, 2005, 2008a.…”

Ammonoid Habitats and Life History

“…A black shale sequence was reported from the Middle Jurassic (BathonianCallovian) Los Molles Formation in Argentina (e.g., Neuquén Basin; Riccardi and Westermann 1991;Riccardi et al 1992). The invertebrate fauna consists mainly of abundant adult ammonoids with very low diversity but high intraspecific variation (Westermann 1996).…”

Ammonoid Life and Habitat

“…At the center of the back-arc Neuquen Basin, Argentina (Riccardi and Westermann, 1991; Riccardi et al, 1992), the thick, dysoxic black shales of the Los Molles Formation (Bathonian-Callovian) were rapidly deposited (ca. 20 cm/Ka).…”