Seccion Paleontologia

Montevideo, Uruguay

Seccion Paleontologia

Montevideo, Uruguay
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Tapia C.A.,University of Otago | Wilson G.S.,University of Otago | Ishman S.E.,Southern University | Wilke H.G.,Católica del Norte University | And 3 more authors.
Global and Planetary Change | Year: 2015

We present new findings from Pliocene marine sediments from the Mejillones Peninsula Tiburon Basin of the northern Chile continental margin that provide constraints for the global sea level record. Sedimentologic and sequence stratigraphic studies reveal facies associations of a continental shelf setting. Textural variations indicate that coarsening and fining up of the succession are due to relative sea level rise and fall, respectively. Magnetostratigraphy was integrated with bio- and tephro- stratigraphic data to construct a record of high-resolution chronology. The age model constrains the Tiburon Basin lower section between 4.2 Ma and 2.8 Ma. The record is likely to be controlled in part by sea level change with orbital periodicities of obliquity (~40 ka of frequency) and, between 3.2 Ma and 2.9 Ma a high-amplitude sea level fall is correlated to global climatic deterioration and the onset of major Northern Hemisphere glaciations. © 2015 Elsevier B.V.

Beri A.,Seccion Paleontologia | Martinez-Blanco X.,Seccion Paleontologia | Mourelle D.,Seccion Paleontologia
Geologica Acta | Year: 2010

This paper presents a synthesis of the palynological record in the Cerro Pelado Formation deposits (Lower Permian, Paraná basin, Cerro Largo Department, north-eastern Uruguay) based on pre-existing data and new findings. The successions studied in this formation consist mainly of non-marine to glacial-marine mudstones and sandy mudstones. The palynological assemblages yielded by 32 samples collected from two outcrops and thirty borehole samples demonstrate that not significant floral changes took place through the considered stratigraphic range. The correlation of these assemblages with biostratigraphic palynozones, proposed previously for the Paraná/Chacoparaná Basin of Brazil, Argentina and Uruguay point to their Early Permian age. The most widespread spore genera in these assemblages are Punctatisporites, Lundbladispora, Vallatisporites and Granulatisporites. Among pollen grains, Caheniasaccites, Vittatina, Potonieisporites, Protohaploxypinus and Plicatipollenites are the most representative. Palynomorphs assigned to Chlorophyta, Prasinophyta, and acritarchs indicate the development of brackish to fresh water lacustrine environments. The results from the facies and palynological analyses suggest that these deposits were formed during interglacial or postglacial warmer climatic episodes. This fact would agree well with the proposal that Gondwana glaciations were characterized by discrete glacial phases (with multiple glacial lobe advance-retreat phases) alternating with warmer climatic episodes. These episodes could be recognized thanks to sub-glacial and melt water related continental deposits that would bear characteristic palynological assemblages, like the recorded in the Cerro Pelado Fm. successions.

Beri A.,Seccion Paleontologia | Gutierrez P.,CONICET | Balarino L.,CONICET
Review of Palaeobotany and Palynology | Year: 2011

A biozonation for the Permian strata of Uruguay is proposed based on published data from boreholes 201, 221, CLSC 3, 4, 11, 13 and 24 drilled by Dirección Nacional de Minería y Geología of Uruguay (DINAMIGE), as well as two superficial samples and the samples from borehole 254, which are described here. Eighteen samples were retrieved from borehole 254 (DINAMIGE), extending from the San Gregorio to the Yaguarí Formation. One hundred and eighty-four taxa were identified. From their vertical distribution in the column, two assemblages were recognised: a lower assemblage that encompasses the San Gregorio Formation up to the lower part of the Melo Formation (Assemblage I), and an upper assemblage that includes the upper part of the Melo Formation (Assemblage II). The boundary between these two assemblages lies in the Mangrullo Member of the Melo Formation. In ascending stratigraphic order, the zones proposed are the Cristatisporites inconstans-Vittatina saccata Assemblage Zone (IS) and the Striatoabieites anaverrucosus-Staurosaccites cordubensis Assemblage Zone (AC). In the IS Zone identified in the San Gregorio and Tres Islas Formations and in the basal part of the Melo Formation (Fraile Muerto Member), the assemblages are characterised by trilete spores and monosaccate pollen and, to a lesser extent, by non-taeniate bisaccate, taeniate bisaccate and plicate pollen grains. An early Cisuralian age is proposed for this Zone. The AC Zone was identified in the Melo Formation, in the Mangrullo and Paso Aguiar Members. It is characterised by assemblages that are dominated by bisaccate (both taeniate and non-taeniate) pollen grains. These palynological assemblages also include a few plicate and monosaccate pollen grains and trilete and monolete spores. A late Cisuralian-Guadalupian age is proposed for this zone. © 2011.

An assemblage of palynomorphs (acritarchs, algae, fungi among other constituent elements of uncertain affinity) both autochtonous and reworked from San Gregorio Formation and Melo (well DI.NA.MI.GE. No. 254 “Paso de Las Toscas”), Paraná Basin, Uruguay, was analysed in this study. The cisuaralians microfloras are mostly indicative of fresh to mixohaline water environments. Notwithstanding, palynomorphs indicative of marine conditions (mainly Micrhystridium) are registered at 349 and 306 mbbp (San Gregorio Formation), and 282, 241, 168 and 139 mbbp (Frayle Muerto Member). The reworked specimens are restricted to some samples of San Gregorio Formation and a sample in the base of Frayle Muerto Member. The results are in accordance to the depositional setting of the sedimentary units as well as with the sea level changes during the time interval considered © 2015 by the Sociedade Brasileira de Paleontologia.

Palynological content of nine samples extracted from borehole N° 254 "Paso de las Toscas" (DI.NA.MI.GE.) is analyzed. The samples derived from the Frayle Muerto, Mangrullo and Paso Aguiar formations, Permian in age. A total of 123 species were identified. This paper presents a systematic analysis of 25 species that are new records for Uruguay. Twelve of these species are assigned to spores, seven to pollen grains and six to acritarchs. Pollen grains are dominant in all assemblages except in the lower stratigraphic levels. Spores are present in relatively high proportions only at the lower and upper levels. Acritarchs and reworked material are found in two samples. The comparison of palynological assemblages with regional palynostratigraphic schemes suggests a Cisuralian age (probably Asselian-Artinskian) for the lower stratigraphic level (Cristatisporites Biozone for Argentina, Vittatina costabilis Biozone for Brasil and Cristatisporites inconstans-Vittatina saccata Biozone for Uruguay) and an age between the late Cisuralian and the Guadalupian for the remaining levels (Striatites Biozone for Argentina, Lueckisporites virkkiae Biozone for Brasil and Striatoabieites anaverrucosus-Staurosaccites cordubensis Biozone for Uruguay).

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