Ammonites from the Maastrichtian (Upper Cretaceous) Quiriquina Formation in central Chile

Primera datación radiométrica (U-Pb, LA-ICP-MS, en circones detríticos) de la Formación Punta Topocalma: observaciones sobre la sedimentación marina durante el Cretácico Tardío en Chile central.

“…In this unit, the assemblage is exceptionally diverse (30 taxa assigned to 17 genera) and shows affinities with Indo-Pacific and European assemblages (Stinnesbeck, 1986;Salazar et al, 2010). Biró-Bagóczky (1982) proposed a Campanian-Maastrichtian age for the formation, but subsequently, Stinnesbeck (1986Stinnesbeck ( , 1996 and Salazar et al (2010) restricted the age of the Quiriquina Formation to the Maastrichtian. Salazar et al (2010) refined the biostratigraphic scheme proposed by Stinnesbeck (1986) FIG.…”

“…Biró-Bagóczky (1982) proposed a Campanian-Maastrichtian age for the formation, but subsequently, Stinnesbeck (1986Stinnesbeck ( , 1996 and Salazar et al (2010) restricted the age of the Quiriquina Formation to the Maastrichtian. Salazar et al (2010) refined the biostratigraphic scheme proposed by Stinnesbeck (1986) FIG. 4.…”

“…Based on ammonites, a Late Senonian age was originally assigned to the Quiriquina Formation by Steinmann (1895). However, Stinnesbeck (1986Stinnesbeck ( , 1996 and Salazar et al (2010) restricted the age of the unit to the Early to Late Maastrichtian, also based on ammonite occurrences.…”

“…Upper Cretaceous marine deposits have also been recognized in boreholes drilled on the continental shelf at the same latitudes (Mordojovich, 1981). These strata have been studied since the 19 th century (e.g., D'Orbigny, 1842; Darwin, 1846;Philippi, 1887;Steinmann et al, 1895;Wilckens, 1904;Wetzel, 1930;Biró-Bagóczky, 1982;Stinnesbeck, 1986;Salazar et al, 2010;Buatois and Encinas, 2011) and constitute an important reference for the Upper Cretaceous of South America due to their diverse fossil fauna and flora that includes bivalves, gastropods, scaphopods, cephalopods, crustaceans, birds, plesiosaurs, mosasaurs, turtles, fish, pollen, and wood (for references see Salazar et al, 2010;Buatois and Encinas, 2011).…”

“…Algarrobo (~33°S) where they were defined as the Estratos de la Quebrada Municipalidad by Gana et al (1996) and assigned to the early Maastrichtian by Levi and Aguirre (1966) based on ammonites, and by Suárez and Marquardt (2003) based on strontium isotope stratigraphy. The Quiriquina Formation is biostratigraphically constrained to the Maastrichtian in its type sections around the bay of Concepción (e.g., Las Tablas, Cocholgüe, Tomé; Stinnesbeck 1986Stinnesbeck , 1996Salazar et al, 2010), but the precise ages of potentially correlative Late Cretaceous units to the north and south of Concepción (Arauco, Chanco, Algarrobo, and Punta Topocalma) are less well known and it remains unclear to date whether deposition in these localities was strictly coeval or may have initiated earlier, during the Campanian (e.g., Pérez and Reyes, 1980;Biró-Bagóczky, 1982;Tavera, 1988). The presence of abundant pumice clasts in Upper Cretaceous marine strata at Punta Topocalma prompted us to carry out U-Pb (LA-ICPMS) geochronological analyses on detrital zircons.…”