Postgondwanic-preandean lacustrine successions in the Famatina Belt (La Rioja and Catamarca provinces)

Abstract

On the eastern edge of the central Famatina Belt, west of the Angulos town, we describe a ~180-m thick sedimentary section compound of a basal grey silcrete covered by gypsum beds and a thick succession of purple mudstones interlayered by varicolored fine sandstones sheets and laminated yellowish dolomites. The study region is acknowledged as La Yesera, because of the recurrence of tectonicallythicken gypsum layers, which locally are ~23 m thick. The whole succession overlies the fluvio-eolian Permian and unconformably underlies Early Miocene synorogenic strata (Del Crestón Formation), both sequences already described in the literature. The sedimentary facies associations allow interpreting that after an important discontinuity evidenced by a siliceous duricrust, extent hypersaline lacustrine systems developed, which support low-relief settings. The stratigraphic position and regional distribution of these strata, together with the facies, color and stratofabric features would allow differentiating a new stratigraphic unit. Thus, we propose to name it the Veteada Formation, localizing its stratotype on the eastern limb of the Colorados anticline (La Yesera region), close to its northern plunging zone. Preliminary micropaleontological analyses on some of these beds have been unfortunately infertile. Yet, lithostratigraphic correlations across and along strike the Famatina Belt, plus indirect deductions coming from termochronologic data from Famatina and nearby regions, would suggest a Triassic or Jurassic age, although we cannot reject the Cretaceous or even Paleogene.