U?Pb detrital zircon ages of Upper Jurassic continental successions: implications for the provenance and absolute age of the Jurassic?Cretaceous boundary in the Neuquen Basin

MAXIMILIANO NAIPAUER; MAISA TUNIK; JULIANA C. MARQUES; EMILIO A. ROJAS VERA; GRACIELA I. VUJOVICH; MARCIO M. PIMENTEL; VICTOR A. RAMOS

GEOLOGICAL SOCIETY OF LONDON SPECIAL PUBLICATION

Geological Society

Año: 2015 vol. 399 p. 131 - 154

0305-8719

New U?Pb detrital zircon ages are presented for the Tordillo Formation. The ages indicatethat the most important source region of sediment supply was the Jurassic Andean arc (peaks atc. 144, 153 and 178 Ma), although two secondary sources were defined at c. 218 and 275 Ma. Temporalvariation in the provenance indicates that at the beginning of the sedimentation, Carboniferousto Lower Jurassic magmatic rocks and Lower Palaeozoic metamorphic rocks were the mostimportant sources. Towards the top, the data suggest that the Andean arc becomes the mainsource region. The comparison between provenance patterns of the Tordillo Formation and ofthe Avile´ Member (Agrio Formation) showed some differences. In the former, the arc regionplayed a considerable role as a source region, but this is not identified in the latter. The resultspermit a statistically robust estimation of the maximum deposition age for the Tordillo Formationat c. 144 Ma. This younger age represents a discrepancy of at least 7 Ma from the absolute age ofthe Kimmeridgian and Tithonian boundary (from the chronostratigraphic timescale accepted by theInternational Commission of Stratigraphy, IUGS), and has strong implications for the absolute ageof the Jurassic?Cretaceous boundary.