PALYNOLOGICAL DATA FROM THE HAUTERIVIAN AVILE MEMBER, AGRIO FORMATION, NEUQUEN BASIN, ARGENTINA

MEGO, N.; M.B. PRÁMPARO; VEIGA, G.D.

Nottingham

Encuentro; The Golden Anniversary Meeting of AASP; 2017

AASP The Palynological Society, CIMP-TMS

The NeuquénBasin, North Patagonia, is famous for a well exposed sedimentary record, richfossil content, and very productive oil and gas reservoirs in subsurface. TheJurassic and Cretaceous infill of the Neuquén Basin include a complex series oftransgressive-regressive cycles of different magnitude controlled by thecombination of changes in subsidence rates, local uplift, and eustaticsea-level oscillations known as Mendoza Group. TheAgrio Fm., which is one of the units of the group, is divided into threemembers:  Pilmatué (lower), Avilé (middle) and Agua de la Mula(upper). The lower and upper members represent a mixed clastic carbonate succession,comprising shales, sandstones, and limestones, interpreted as storminfluenced shoreface to offshore deposits. The Avilé Membercorresponds to non-marine deposits that represent a low-order regressive event.Based on facies and architectural analysis fluvial, aeolian and lacustrinesystems were recognized within the unit. A long-termwetting-upward trend is recorded throughout the entire unit, with an increasein fluvial activity towards the top and the development of a more permanentfluvial system. The upward increase in water-table influence might be relatedto relative sea-level rise together with a long-term climatic change towardswetter conditions (Veiga et al. 2002).The onlyprevious record of palynomorphs from this unit, come from Cerro La Parvasection (Prámparo et al. 1999). New palynological data from the Avilé Member,Agrio Fm. Neuquén basin, Argentina are presented here. Thestudied samples were collected from the upper part of the Avilé Member, at PampaTril and San Eduardo outcropping sections, central-eastern part of the basin. High-sinuosity channelsassociated with floodplain deposits characterize the upper part of the unit. Acontinental palynological association was recovered which is mainly representedby: Cyclusphaera radiata, Cyclusphaera psilata, Balmeiopsis limbatus, Classopollis spp., Callialasporites dampieri, Podocarpiditesspp., Alisporites sp.,Araucariacites australis, Cycadopites sp., among gymnosperms. Triletespores related to ferns, bryophytes and lycophytes are mainly characterized by Anapiculatisporites dawsonensis, Interulobites lajensis, Interulobites variabilis, Taurocusporites sp., Januasporites sp., Foraminisporis sp., and Triporoletesreticulatus. Furthermore, oxidized small pieces of cuticles and planttissues complete the association. The palynoflora of the Avilé Member providesimportant data about the paleovegetation of this particular moment (late Earlyto early Late Hauterivian) related to a sea fall in the basin.