Nuevos aportes a la palinología, cronología y paleoambiente de la Precordillera Occidental de Argentina: Formaciones El Planchón, Codo (Devónico) y El Ratón (Mississippiano).

AMENÁBAR, C.R., DI PASQUO, M.M.

San Miguel de Tucumán

Jornada; 2ª Jornadas Geológicas de la Fundación Miguel Lillo; 2008

Fundación Miguel Lillo

New palynological data from the Devonian and the Mississippian rocks from the Calingasta area, placed at the south of the San Juan river of the Western Precordillera of Argentina are presented. The palynological assemblage obtained from the Codo Formation, is mainly composed of acritarchs (Lophosphaeridium spp., Cerastum sp.), and scarce spores poorly preserved (Apiculiretusispora sp., Cyclogranisporites sp.). The assemblage is tentatively attributed to the Givetian-Frasnian based on the age of the genera Cerastum Turner. The El Ratón Formation, yielded an assemblage mainly composed of densospores (70 %) dominated by the genera Cristatisporites; less frequent are acavate apiculate (20 %), verrucate (6 %) and smooth (0.4 %) trilete spores and others patinate (2.4 %) and pseudosaccate (1.2 %). The diagnostic species such as Anapiculatisporites amplus Playford and Powis, Anapiculatisporites hystricosus Playford, Colatisporites decorus (Bharadwaj and Venkatachala) Williams in Neves et al., Verrucosisporites morulatus Potonié and Kremp emend. Smith and Butterworth and Verrucosisporites papulosus Hacquebard allow the assignment of an early Viséan age. Considering these palynological results, the hiatus between Codo and El Ratón Formations would span part of the Late Devonian and the Tournaisian. Besides, a correlation between the middle part of the Malimán and the El Raton Formations is here supported on the basis of shared palynomorphs such as Verrucosisporites papulosus, Colatisporites decorus, Apiculatisporites sp. cf. A. variocorneous and Lophotriletes sp. The Upper Member of the El Panchón Formation (Devonian?) resulted palynologically barren. Although, new sedimentological information obtained here suggests a shallow marine palaeoenvironment disagreeing from previous deep marine interpretation.