The Talampaya Formation: a record of Late Permian sedimentation in western margin of Gondwana

GULBRANSON, E.L.; CICCIOLI, P.L.; MONTAÑEZ, I.; MARENSSI, S.A.; LIMARINO, C.O.; SCHMITZ, M.; DAVYDOV, V.

CABA

Simposio; VI Simposio Argentino del Paleozoico Superior; 2013

The thick red bed succession of the Talampaya Formation has been largely assigned to the Early Triassic based on stratigraphic considerations. However neither paleontological remains with stratigraphic significance nor radiometric ages were provided up to now. We report here the first U/Pb age of 252.38 (+0.09/-0.22) Ma (latest Permian close to the Permian-Triassic boundary) for the upper part of the Talampaya Formation in the Cuesta de Miranda area. In addition, a detailed sedimentological study allowed recognizing 8 facies associations (FA) suggesting a gradual aridization from base to top. FA1 is composed of coarse-grained conglomerates and breccias deposited in alluvial fans. FA2 is made up of conglomerates and coarse grained sandstones of braided fluvial systems. FA3 represents a thin intercalation of basaltic breccias and lithic sandstones indicating a short intrabasinal volcanic event. FA4 comprises finning-upward cycles of conglomerates to mudstones interpreted as originated in meandering rivers. FA5 consists of horizontal laminated fine-grained sandstones deposited in sandflat environments. FA6 well-sorted fine-grained sandstones represent a thin eolian intercalation within the playa lake system. FA7 characterized by interbedded fine-grained sandstones and mudstones is interpreted as a sandflat/mudflat transition. Finally, FA8 composed of finely laminated claystones and siltstones with thin intercalations of fine-grained tuffs, corresponds to the central muddy part of the playa lake system. The dated tuff level from FA8 suggests that most of the Talampaya Formation was deposited during the late Permian but a transition to the earliest Triassic in the uppermost levels of this unit must not be ruled out.