IDEAN   23403
INSTITUTO DE ESTUDIOS ANDINOS "DON PABLO GROEBER"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Interpretation of “Saccocoma microfacies” and their significance in the Tithonian of the Neuquén Basin, Vaca Muerta Formation, Mendoza, Argentina
Autor/es:
KIETZMANN, D.A.; PALMA, R.M; B. FERRÉ
Lugar:
Bahía Blanca
Reunión:
Simposio; IV Simposio Argentino del Jurásico y sus Límites; 2010
Resumen:
Microfacies studies conducted in the Vaca Muerta Formation have recorded thepresence of saccocomid microcrinoids in the Neuquén Basin. This finding is the firstrecord of Saccocomidae outside the Tethys/North Atlantic area. Samples withsaccocomids come from the middle and upper Tithonian (Pseudolissoceras zitteli toCorongoceras alternans zones) of the Río Salado, Arroyo La Manga, Arroyo Loncoche,Bardas Blancas, Sierra Azul and Sierra de Cara Cura sections. A northeast-southwesttransect of Sequence-1 is used here to establish the distal proximal gradient of thecarbonate ramp. Saccocomid remains occur in laminated bioclastic wackestones,wackestones with HCS as sparse elements, as well as in sedimentary concentrations(Saccocoma microfacies) forming laminated packstones with intralaminar normalgradation. These deposits are interpreted as proximal and distal tempestites. Sparseelements are typical of middle-ramp and proximal outer-ramp facies in HST deposits,whereas “Saccocoma microfacies” is typically found in outer-ramp facies associatedwith TST deposits. Taphonomic and sedimentologic studies clearly demonstrate that thedifferential hydrodynamic behaviour of the different elements is minimal. However, thedominance (relative to the ideal ratio in Saccocoma tenella) of primaxilar (IBr2) andsecundibrachials (IIBr2, IIBr4-7 and IIBr8-17) on radials (R), primibrachials (IBr1), andnon-ornamented secundibrachials (IIBr1 and IIBR 3), could be used as a distally index.Additionally, future detailed studies of the temporal distribution of genera Saccocomaand Crassicoma could contribute to the biostratigraphy of the Tithonian of the NeuquénBasin.