FIRST PALYNOLOGICAL RECORD FOR THE LOWER MEMBER OF CERRO MORADO FORMATION ( MIOCENE), LA RIOJA PRECORDILLERA. The finding of palynological remains in the lower member of the Cerro Morado Formation is reported for the first time. The fossiliferou

BARREDA, V.; LIMARINO, C.O; FAUQUET,L; TRIPALDI, A; NET, L.

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2003 vol. 40 p. 81 - 88

0002-7014

Abstract. FIRST PALYNOLOGICAL RECORD FOR THE LOWER MEMBER OF CERRO MORADO FORMATION ( MIOCENE), LA RIOJAPRECORDILLERA. The finding of palynological remains in the lower member of the Cerro Morado Formation is reportedfor the first time. The fossiliferous levels are located at the headwaters of the Guandacol river in southwestern LaRioja Province. In this area the Cerro Morado Formation has been divided into two members. The lower member,composed of sandstones, mudstones and scarse conglomerates and limestones, contains the palynological remainsdescribed in this paper. The palynological assemblages are not diverse, they are poorly preserved and dominated byaquatic elements mainly related to colonial green algae (Pediastrum spp., Botryococcus sp.) and dinoflagellates. Sporepollenassemblages consist of aquatic herbs of Restionaceae (Milfordia sp.) and Malvaceae (Baumannipollis chubutensisBarreda, Baumannipollis sp., Malvacipolloides comodoroensis Barreda). Typical lake shore vegetation consisted of membersof Ephedraceae [Equisetosporites claricristatus (Shakmundes) Barreda, E. notensis (Cookson) Romero, E. lusaticus(Krutzsch) Barreda] and scarse Chenopodiaceae (Chenopodipollis chenopodiaceoides (Martin) Truswell). Pollen grains relatedto Podocarpaceae (Podocarpidites marwickii Couper, P. elegans Romero) and Fagaceae (Nothofagidites acromegacanthusMenéndez and Caccavari, N. americanus Zamaloa, N. saraensis Menéndez and Caccavari) are also present, althoughin low percentages. The known stratigraphic ranges of the recognized species, and the similarities of these assemblagesto others previously described from Argentina, point to an Early to Middle Miocene age for this unit.Finally, sedimentological and palynological evidences suggest the development of a large and perennial water bodyduring the time of deposition of the lower member of Cerro Morado Formation.