Albian zircon U-Pb crystallization ages from tuff beds in the Candeleros and Huincul formations, Neuquén Basin, Argentina

New U-Pb zircon laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) ages from airfall tuff beds in the dinosaur-rich nonmarine Candeleros Formation (111.4 ± 1.1 Ma) and overlying Huincul Formation (106.8 ± 2.2 Ma) in the Neuquén Basin of Argentina indicate Albian ages for both stratigraphic units. Three widely separated volcanogenic sandstones collected from basal Candeleros Formation strata ∼ 200 km north of the dated Candeleros airfall ash bed contain statistically indistinguishable clusters of young detrital zircon grains that confirm an early Albian (∼111 Ma) age for basal Candeleros strata across the entire Neuquén Basin. Depositionally synchronous zircon, as seen here in basal Candeleros strata, is a widespread and well-documented feature of retroarc basin assemblages adjacent to active volcanic arcs. The new Albian ages for the Candeleros and Huincul formations require a shift in the age of two of the six major tetrapod assemblages defined for the Neuquén Basin by ∼ 10–15 Myr and prompt a broad reevaluation of fossil assemblages and correlations across the Early-Late Cretaceous boundary, which are critical for the study of the evolution and diversification of Patagonian faunas. The early Albian Candeleros Formation is correlated here to the Cerro Barcino Formation of the dinosaur-bearing Chubut Group 500 km to the south of the Neuquén Basin. This correlation resolves formerly confounding biostratigraphic correlation between these two areas. The new ages also place constraints on the timing of Andean fold and thrust belt inception and further indicate that pedogenic contrasts between the Candeleros and Huincul formations reflect the emergence of global climate from cooler conditions toward warmer Greenhouse World conditions broadly characteristic of the mid-Cretaceous.