Middle-Upper Devonian palynoflora from the Tonono X-1 borehole, Salta Province, northwestern Argentina

Sol Noetinger

Abstract


The surveyed microflora was recovered from six cores from the Tonono x-1 well in northwestern Argentina. Most of the studied interval corresponds to the Tonono Formation, i.e., the upper part to the Jollín Member and the basal part of the interval may be related to the Michicola Formation. The microflora totals 73 species represented by trilete spores (35 species), microplankton (30 species) including prasinophycean, acritarch and chlorophycean algae and chitinozoans (8 species). The stratigraphic distribution of these species allowed the definition of three associations. The palynoassemblage To1 (3946,5 - 3638,5 m) is characterized by species such as Grandispora douglastownense Mc Gregor, Dibolisporites eifeliensis (Lanninger) McGregor, Verrucosisporites sp. cf. V. loboziakii Marshall and Fletcher, Alpenachitina matogrossensis Burjack and Paris, Alpenachitina sp. cf. A. eisenacki Dunn and Miller and Ancyrochitina simplex Grahn, Bergamaschi and Pereira suggesting a late Eifelian to earliest Givetian age. Based on the presence of Geminospora lemurata Balme, Aneurospora greggsii (McGregor) Streel, Biharisporites parviornatus Richardson, Raistrickia aratra Allen and Leiotriletes balapucencis di Pasquo a Givetian age is proposed for palynoassemblage To2 (3367,35 - 3285 m). Palynoassemblage To3 (3073,2 - 3137,5 m) is predominantly composed of marine elements together with AOM. Few key species are recognized; however the presence of Acinosporites sp. cf. A. eumammillatus Loboziak, Streel and Burjack together with the chitinozoans Angochitina katzeri Grahn and Melo and Angochitina mourai Lange support an early Frasnian age. The distinctive increase of marine elements and AOM between To2 and To3 suggests that a máximum flooding event would have occurred there during this period.

PALINOFLORA DEL DEVÓNICO MEDIO-SUPERIOR DEL POZO TONONO X-1, PROVINCIA DE SALTA, NOROESTE DE ARGENTINA. Se presenta el estudio de seis coronas del pozo Tonono x-1 ubicado en el noroeste Argentino. La mayor parte del intervalo estudiado corresponde a la Formación Tonono; la porción superior al Miembro Jollíny la porción basal podría relacionarse con la Formación Michicola. La microflora recuperada se compone de 73 especies representadas por diversos grupos palinológicos como esporas trilete (35 especies), microplancton incluyendo prasinofitas, acritarcas, algas clorofitas (30 especies) y quitinozoos (8 especies). La distribución estratigráfica de las especies permite distinguir tres asociaciones, la asociación To1 (3946,5 - 3638,5 m), caracterizada por Grandispora douglastownense Mc Gregor, Dibolisporites eifeliensis (Lanninger) McGregor, Verrucosisporites sp. cf. V. loboziakii Marshall y Fletcher, Alpenachitina matogrossensis Burjack y Paris, Alpenachitina sp. cf. A. eisenacki Dunn y Miller y Ancyrochitina simplex Grahn, Bergamaschi y Pereira sugieren una edad eifeliana tardía–givetiana temprana. Debido a la presencia de Geminospora lemurata Balme, Aneurospora greggsii (McGregor) Streel, Biharisporites parviornatus Richardson, Raistrickia aratra Allen y Leiotriletes balapucencis di Pasquo se propone una edad givetiana para la asociación To2 (3367,35 - 3285 m). La asociación To3 (3073,2 - 3137,5 m) comprende predominantemente elementos marinos incluyendo MOA. Se reconocen las siguientes especies clave Acinosporites sp. cf. A. eumammillatus Loboziak, Streel y Burjack junto a los quitinozoos Angochitina katzeri Grahn y Melo y Angochitina mourai Lange las cuales sugieren una edad frasniana temprana. El notable incremento de material de origen marino y MOA entre To2 y To3 sugiere que un evento de máxima inundación podría haber ocurrido allí durante este período.

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