An estuarine fossil assemblage from the Yacoraite Formation (Maastrichtian-Danian) and his paleoenvironmental significance. Jujuy - Northwestern Argentine.

CÓNSOLE GONELLA C.A.; HORTA L.R.; HERRERA OVIEDO E. P .; GRIFFIN M.; GEORGIEFF S.M.; ACEÑOLAZA, F.G.

San Miguel de Tucuman. Argentina

Otro; 9th International Conference On Fluvial Sedimentology 24th ? 28th August, 2009; 2009

IESGLO- Instituto de Estratigrafia Global, Fundacion Miguel Lillo

We  describe  a  fossils  assemblage  of  brackish  water  identified  on  sedimentary sequences of  the Yacoraite Formation  (Maastrichtian ? Danian),  in the  localities of Maimará  and  Jueya,  Jujuy  -   Northwest Argentine.  The  dominant  lithology  of  the study  levels  are  characterized  by  a  calcareous  sandstones  succession,  with ripplestratified structure, upward-fining. Fine to very fine sandstone lenses occur in this  fossiliferous  interval.  The  sandstones  are  interpreted  as  storm  washover deposits.  In  these  sequences we  have  found  numerous  disarticulated  remains  of  fishes  (Pycnodontiforms  and  Siluriforms),  fragments  of  tetrapods?  (Tetrapoda),  a tooth  of  crocodile  (Crocodylidae),  mollusks  badly  preserved  (Gastropods  and Bivalves)  of  problematic  taxonomy,  estromatolites  (LLHC,  LLHS  and  dome  type). Also was  identified a  set of  fossil  traces  integrated by  traces of birds  (Avipedidae) and  Skolitos  ichnofacies    ,  besides  a  Domichnia  trace  on  an  estromatolitic  rock, caused by a perforant bivalve, also preserved. Our study of the fossils assemblage, traces,  sediments,  and  sedimentary  structures  indicates  a  brackish  mixed environment, of low depth and high energy, probably estuarine.