Taxonomic and Biostratigraphic analyses of the Ordovician graptolites from La Ciénaga de Purmamarca, Jujuy Province, Argentina

NAVARRO, J. MATÍAS; TORO, BLANCA A.; MUÑOZ, DIEGO F.; HERRERA SÁNCHEZ, NEXXYS C.

Puerto Madryn

Congreso; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2018

The detailed paleontological sampling of the Acoite Formation, carried out at La Ciénaga de Purmamarca area, allowed to obtain a variety of graptolites among which we can highlight Kiaerograptus kiaeri Monsen, recorded for the first time in this section. The taxonomic study confirmed the occurrence of Paratetragraptus approximatus Nicholson in the lower part of the Acoite Formation, and permitted the identification of numerous specimens of  Cymatograptus rigoletto Maletz, Rushton and Lindholm. Baltograptus vacillans Tullberg and Baltograptus geometricus Törnquist were recorded at the intermediate levels, while Baltograptus cf. B. turgidus Lee and Baltograptus kunmingensis Ni at the upper levels of the mentioned unit. The biostratigraphic analysis indicates that the Tetragraptus phyllograptoides? (Fl 1), Tetragraptus akzharensis (Fl 1) and the lower part of Baltograptus cf. B. deflexus (Fl2) Biozones are present in La Ciénaga de Purmamarca, documenting the early Floian to early middle Floian age of the studied deposits. The species K. kiaeri, corresponding to the Aorograptus victoriae Biozone, indicates a late Tremadocian age for the fossil-bearing levels, which are considered a section of the Santa Rosita Formation. Additionally, the studied stratigraphic interval is regionally correlated with the lower to middle part of the Acoite Formation of Los Colorados, Sierra de Aguilar and Santa Victoria, in Argentina; and with equivalent levels exposed in Cieneguillas and Chaupi Uno, in Bolivia. It is also globally correlated with Baltoescandinavia, Avalonia and Morocco, confirming the paleobiogeographic affinities of the Central Andean Basin with other regions of intermediate to high latitudes.