Sedimentary evolution of Tres Cruces basin: Constraints on the development of the Cenozoic foreland in Central Andes, NW Argentina

VILLALBA ULBERICH, JUAN PABLO; GALLI, CLAUDIA INÉS; FRANZESE, JUAN RAFAEL

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2021 vol. 112 p. 1 - 21

0895-9811

The Tres Cruces basin presents an excellent record of deposits linked to the evolution of the foreland in the context of the Andean orogeny in the Eastern Cordillera, Central Andes. The Cenozoic synorogenic deposits arerepresented by Casa Grande, Río Grande, and Pisungo formations with thicknesses up to 5000 m. The detailedsedimentological and paleoenvironmental analysis on the north-central sector of the Tres Cruces basin allowedthe recognition of an unconformity over post-rift Salta Group, marked by the progradation of an ephemeralfluvial system (Casa Grande Formation) over the Lumbrera Formation during the middle Eocene. Theestablishment of a meandering fluvial system with flow directions to the east, and an increase of lithic contentversus quartz content, support the idea of a distal orogenic front uplifting to the west. During the late Oligocene,an erosive unconformity and the change to a braided fluvial system characterize the Río Grande Formation,where the coarsening-upwards arrangement, paleocurrents with a distributary pattern, and the increase ofvolcanic fonts are related to the approach of the orogenic front. From the late Miocene, Pisungo Formationdeposits are restricted to local syncline depressions, characterized by diffuse geometries and boulder clast sizewith a rotation of the paleocurrent directions, indicating the development of local highs and the low capacity ofriver systems. Our analyses suggest an environmental progradation from meandering to braided and later to analluvial fan fluvial system linked with a change from distal to proximal foreland between Casa Grande and RíoGrande formations, to an intermontane system in Pisungo Formation. These results provide an adequate temporalframework for the study of environmental and landscape evolution of Eastern Cordillera and have directimplications for the local and regional development of the Andean orogenesis.