Stratigraphy, Geochronology and Paleoenvironments of Miocene - Pliocene Boundary of San Fernando, Belén (Catamarca, Northwest of Argentina)

BONINI, R., GEORGIEFF, S.M., CANDELA, A.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2017

0895-9811

The Santa María-Hualfín Basin was proposed as a regional synchronous lithostratigraphic depocenter in thegeological province of Northwestern Pampean Ranges, Northwestern of Argentina. However, new 40Ar?39Ar datingindicates that deposits toward the east, in Santa María Valley (Santa María Department), are younger than thewestern depocenter in San Fernando (Belén Department). Therefore, it would be more appropriate to study thesevalleys as separate basins, each one with its own tecto-sedimentary features. The east basin, named in this paperVillavil-Quillay, constitutes an elongated basin that developed along the front of the eastern Puna bordering withPampachacra and Durazno Ranges. This Basin is composed of more than 3,000 m of mudstone, sandstone,conglomerates, volcaniclastic and pyroclastic deposits. Villavil-Quillay Basin developes onto a peneplain ofPrecambrian and Lower Cambrian rocks, most metamorphic and granites rocks. The sedimentary fill consists ofCretaceous? and Cenozoic continental deposits. The Cenozoic record is composed of a) the Santa María Group(Miocene-Pliocene), formed by Las Arcas, Chiquimil, Andalhuala and Corral Quemado Formations, and b) thePunaschotter (Puna?s Gravels in German, Pleistocene). This study involves the Andalhuala, Corral Quemado andPunaschotter deposits cropping out in San Fernando area (Belén Department, Catamarca Province). The set ofidentified facies assemblages corresponding to the Andalhuala Formation shows a vertical variation of fluvial subenvironments,varying from permanent sandy braided rivers to gravel rivers and aeolian dunes culminating in analluvial dry cycle. While facies assemblages of the Corral Quemado Formation allowed inferring ephemeral waterbodies development of secondary channels on the floodplain, the Punaschotter conglomerates indicate thedevelopment of the gravel channels and bars. Three samples of tuffs interbedded in the sedimentary levels ofAndalhuala Formation were dated indicating that the Miocene-Pliocene boundary is represented in the AndalhualaFormation cropping out in San Fernando area. The lower tuff beds, outcropping at the southwest of San Fernando Sur,provided an age of 5.59 ± 0.04 Ma (Late Miocene, Messinian). The others tuffs beds, both outcropping at the westnorthwestof San Fernando Norte and overlaying the first one, gave an age of 4.79 ± 0.15 Ma and 4.72 ± 0.08 Ma(Early Pliocene, Zanclean), respectively. These absolutes ages, joined to the results of a sedimentological analysis,allow identifying that toward the west of San Fernando River, much of the areas mapped as Corral QuemadoFormation correspond to the Andalhuala Formation; while part of the area considered Punaschotter must be assignedto Corral Quemado Formation. Also, a thick bed of tuff, recognized at the contact of Corral Quemado andPunaschotter, was considered as the previous one dated in 3.66 Ma, in Puerta de Corral Quemado locality.