Exploring hypotheses about mixed carbonate-siliciclastic successions in lacustrine settings: A case study from the Yacoraite Formation, Tres Cruces sub-basin, Argentina

Abstract

The Yacoraite Formation represents a mixed carbonate-siliciclastic succession deposited in the Salta Basin (NW Argentina). In the Tres Cruces sub-basin, the spectacular exposures and lateral continuity of outcrops provide the perfect setting to study and reconstruct the spatial variability and stratigraphic architecture of the facies deposited in this complex setting. In this location facies are represented prevalently by marginal littoral and sub-littoral facies: bioclastic and oolitic grainstones and packstone, shell rudstones and microbial carbonates. The facies analysis and high-resolution stratigraphic analysis allow to reconstruct in detail the paleoenvironmental conditions of the Yacoraite Formation, interpreted as a closed saline lake system characterized by extended marginal littoral areas where prevalently carbonate facies deposited. The evolution of the Yacoraite paleo-lake has also been reconstructed and shows a transition from a relatively stable perennial lake system to a highly fluctuating ephemeral lake systems. The stratigraphic architecture is characterized by a marked cyclicity, at different scales and hierarchies: with long-term, medium, and short-term cyclicity being observed. The short-term cyclicity is the base of the stratigraphic architecture and is characterized by metric-scale transgressive-regressive cycles (T-R), interpreted as the result of climatically-controlled lake expansion and contraction phases.