First record of the Xiphograptus genus (Graptolithina) in the Cordillera Oriental, Argentina

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

San Luis

Congreso; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2017

New graptolite collections were made in the Jujuy Province, Argentina, related to the Doctoral Thesis of one of the authors (N.C.H.S.). This material (CEGH-UNC24943) was found in fair weather shale deposits exposed at the eastern side of the route Tuxa-Los Colorados, in the western flank of the Cordillera Oriental. It is biostratigraphically interesting the appearance of a slender tubarium, which is composed by two slightly declined stipes, with triangular sicula possessing a conspicuous virgella. The characteristic proximal end allows us to assign the specimen to the genus Xiphograptus Cooper and Fortey, 1982, while the sicular length and sicular apertural diameter, as well as the stipes divergence angle and proximal width are in agreement with Xihograptus lofuensis (Lee, 1961).This finding, from overlying levels with respect to deposits corresponding to the Didymograptellus bifidus (Fl3) and Azygograptus (Dp1) zones, suggests a Dapingian age (Dp2). Previous records of X. lofuensisare scarce and poorly known in the South American Central Andean Basin. They come from the Huatiquina section, in the western flank of the Argentine Puna, which were assigned to X. svalbardensis (Archer and Fortey, 1974) and considered indicative of a Dapingian age (Dp2? Dp3), and from the Chala Mayu section in southern Bolivia (Isograptus victoriae Zone). The present record indicates the correlation between the mentioned bearer deposits, extends the geographic distribution of the analyzed taxon in the Argentine Cordillera Oriental, and increases the biostratigraphic potential of the group for understanding the Lower-Middle Ordovician transitional interval, and possibly younger successions of northwestern Argentina.