Chaco-Parana Basin Research Articles

Early Devonian Marine and Terrestrial Palynomorphs from the Chacoparaná Basin, Uruguay

The Cordobes Formation and the basal section of the La Paloma Formation, from the borehole La Paloma a-186 and the Devonian oucrops of the Chacoparana Basin, in Uruguay, yielded diverse and well-preserved marine and terrestrial palynomorphs. The palynological assemblages show a clear predominance of marine palynomorphs, with 75 species composed mainly of acritarchs and chlorophytes with subordinated chitinozoans and scolecodonts, and 48 terrestrial palynomorphs species composed mainly of trilete spores and subordinated cryptospores, non-marine palynomorphs and phytodebris. The palynological assemblages enable the constraining of the age of the lower and middle parts of the Cordobes Formation to the late Pragian–early Emsian, while the upper part of this unit and the basal part of the La Paloma Formation can be assigned to the early Emsian. The relative palynomorph abundances throughout the studied samples support the palaeoenvironment interpretation, based on sedimentology and depositional sequences studies, that indicates the transition from transgressive deposits in a restricted platform of the Cordobes Formation to wave-dominated shelf deposits of the La Paloma Formation. The Gondwanan affinities of the Devonian of Uruguay are confirmed by the presence of marine and terrestrial palynomorph taxa restricted to this palaeocontinent. A new trilete spore species, Distaverrusporites steemansii, is described and a new informal acritarch group, the Evittia sommeri-Evittia geometrica Group, is proposed.

Exhumed subglacial landscape in Uruguay: Erosional landforms, depositional environments, and paleo-ice flow in the context of the late Paleozoic Gondwanan glaciation

A well-exposed glacial surface sculpted on Precambrian crystalline basement rocks occurs below the glacial succession of the San Gregorio Formation on the eastern border of the Chaco-Parana Basin in Uruguay and was formed in the context of the late Paleozoic Gondwana Ice Age. On the glacial surface are asymmetric parallel streamlined bedrock landforms interpreted as whalebacks. The downglacier (lee-side) faces of the whalebacks have gentle slopes dipping NNW with striated and sometimes polished surfaces on crystalline rocks. These landforms are covered by 10–100-cm-thick layers of tillites and shear-laminated siltstones, suggesting glacial abrasion produced mainly by subglacial till sliding. The subglacial facies are ice-molded, and exhibit meso-scale glacial lineations such as ridges and grooves up to 30 m long and 30 cm deep. The subglacial association is directly overlain by proglacial fine-grained facies (rhythmites) with dropstones indicating a subaqueous depositional environment following ice-margin retreat. The fine-grained facies are erosively cut by a succession of sandstones with wave-generated stratification resting on a basal conglomerate. Intraformational striated surfaces, NNE-oriented, were found on four distinct bedding planes within the sandstone package and interpreted as ice keel scour marks produced by floating ice. The San Gregorio deposits are partially confined in a wide and shallow subglacial trough and the stratigraphic succession is interpreted as the record of a glacial advance-retreat cycle comparable to deglacial sequences from other late Paleozoic localities. The paleo-ice flow to the NNW indicated by subglacial lineations is parallel to that verified in the southernmost Paraná Basin located north of the study area, suggesting a paleogeographic scenario in which glaciers advanced northward into a glaciomarine environment. The proposed palaeogeography does not confirm the previous hypothesis of an ice center on the Sul-Riograndense Shield but, instead, it corroborates a south-derived Uruguayan Ice Lobe advancing to the north, probably with provenance far afield in terranes of the present-day southern African.

El petróleo de San Cristóbal. ¿Realidad o leyenda?

El presente trabajo tiene como objetivo hacer un resumen de las actividades exploratorias desarrolladas en la zona de San Cristóbal, provincia de Santa Fe (República Argentina) desde el año 1913 a la actualidad. Trata de valorar, dentro del análisis del Sistema Petrolero, las manifestaciones de hidrocarburos descriptas tanto en el pozo N° 8, perforado por el Ministerio de Agricultura en la búsqueda de agua para el ferrocarril del Estado, como en el perforado por Yacimientos Petrolíferos Fiscales (YPF) entre los años 1933 y 1935.Es importante destacar que con la perforación del pozo San Cristóbal-1 se inició formalmente la exploración de petróleo en el sector argentino de la cuenca Chacoparaná. Las manifestaciones de hidrocarburos descriptas en ambos pozos durante la perforación, desataron en su momento expectativas en la sociedad y fueron responsables de grandes títulos en la prensa provincial y nacional sobre lo que podría constituirse en un nuevo yacimiento de petróleo. Pero lamentablemente no fue así. Sin embargo, la lectura crítica realizada sobre legajos de pozos, informes técnicos y diarios de la época, como también la incorporación de nuevos datos de laboratorio, han posibilitado mejorar el análisis de los elementos y procesos del Sistema Petrolero. Estos avances permiten aseverar que niveles de areniscas de probable edad mesozoica del sondeo San Cristóbal-1, cercanos a la profundidad de 1.350 mbbp, han estado expuestos a procesos de migración de hidrocarburos líquidos.

Magnetotellurics applied to the study of the Guaraní aquifer in Entre Ríos Province, N–E Argentina

Abstract The South American Guarani Aquifer System covers the entire Parana basin and part of the Chaco-Parana basin. This system is one of the most important groundwater reservoirs; it is shared by four neighboring countries covering an area larger than one million square kilometers. The geological units closely related to the Guarani Aquifer are the Piramboia and Botucatu Formations that consist of Triassic–Jurassic aeolian, fluvial and lacustrine sandstones, and the Serra Geral basalts with clastic intercalations. Serra Geral, an effusive Cretaceous complex, covers the sandstones and provides a high degree of confinement to the system. This paper presents the interpretation of magnetotelluric (MT) data collected during 2007–2008 in Entre Rios Province, Argentina. These data, recorded in three profiles, mainly provide the depth to the crystalline basement, determinant for the presence of aquifer-related sediments. Models showed that the discrimination of the basalts strongly depends on local electrical characteristics. Model information is quite consistent with the information from oil and thermal wells located close to the profiles.

A synthesis of palynological data from the Lower Permian Cerro Pelado Formation (Parana Basin, Uruguay): A record of warmer climate stages during Gondwana glaciations

This paper presents a synthesis of the palynological record in the Cerro Pelado Formation deposits (Lower Permian, Parana 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 Parana/ Chacoparana 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.

A stratigraphical-geochemical study on the Chaco Paraná continental rift basin—An approach study based on regional sedimentology and drill-hole core analyses, South América

A stratigraphical-geochemical study on the Chaco Paraná continental rift basin—An approach study based on regional sedimentology and drill-hole core analyses, South América

Hydrogeology of the Mercosul aquifer system in the Paraná and Chaco-Paraná Basins, South America, and comparison with the Navajo-Nugget aquifer system, USA

The giant Mercosul aquifer system consists of Triassic-Jurassic eolian-fluvio-lacustrine sandstones confined by Cretaceous basalt flows, and it covers about 1,195,500 km2 (461,583 miles2) in South America. The aquifer system encompasses all of the Parana Basin and part of the Chaco-Parana Basin and is one of the world's largest. The eolian Botucatu Sandstone and its equivalents form an important part of this system. Maps of structure, thickness of overlying rocks, and water temperature, and a potentiometric map, all based on 322 wells, define hydrogeologic characteristics and provide the basis for establishing guidelines for the long-term equilibrium use of this important multinational aquifer system. The Mercosul aquifer system is divided into two domains – the larger and better understood Parana Basin and the smaller and less well understood Chaco-Parana Basin. Most of the northern part of the Parana Basin has axially-directed groundwater flow, whereas the southern part of the aquifer discharges mostly to the southwest into the Corrientes Province of Argentina, with negligible discharge into the Atlantic Ocean. The Mercosul aquifer system is conservatively estimated to have been flushed at least 180 times since deposition. Various factors are responsible for this flushing, including appreciable rainfall since the end of the Cretaceous Period, probable uplift of the basins' borders in Late Cretaceous time, simple basin geometry, long-term riverine and groundwater flow to the southwest (ancestral and present Parana River Systems), and stable cratonic setting.

Upper Paleozoic strata of the Chaco-Parana basin, Argentina, and the great Gondwana glaciation Winn R.D. Jr & Steinmetz J.C., Journal of South American Earth Sciences, 1998, 11/2 (153?168)

Upper Paleozoic strata of the Chaco-Parana basin, Argentina, and the great Gondwana glaciation Winn R.D. Jr & Steinmetz J.C., Journal of South American Earth Sciences, 1998, 11/2 (153?168)

Preliminary correlation of palynological assemblages from Oman with the Granulatisporites confluens Oppel Zone of the grant formation (lower Permian), Canning Basin, Western Australia

The presence of Granulatisporites confluens Archangelsky and Gamerro indicates an Asselian-Tastubian (lowermost Permian) age for glaciogene sediments in the Amal-6 borehole, Oman. This suggests that the Al Khlata Formation is in part coeval with glaciogene sediments of the Canning Basin, Western Australia, and sediments of the Chacoparana Basin, Argentina.

Upper Paleozoic Deposits of the Chaco-Parana Basin, Argentina, and the Great Gondwana Glaciation: ABSTRACT

Upper Paleozoic Deposits of the Chaco-Parana Basin, Argentina, and the Great Gondwana Glaciation: ABSTRACT

TheGranulatisporites confluensOppel-zone and Early Permian marine faunas from the Grant Formation on the Barbwire Terrace, Canning Basin, Western Australia

A taxonomically diverse plant microfossil assemblage recovered from a fully cored, marine, glacigene sequence of the Grant Formation, Canning Basin, Western Australia, contains 68 palynomorph species derived mostly from ferns, lycopods, gymnosperms and algae. The assemblage has been assigned to the newly defined Granulatisporites confluens Oppel-zone. G. confluens was first described from Late Palaeozoic sequences of the Chaco-Parana Basin, Argentina, and together with other key species indicates close correlation with assemblages from South America, India, Africa and, to a lesser extent, Antarctica. The associated marine fauna is diverse and includes foraminiferids, crinoids, bryozoans, molluscs and brachiopods. Twenty species of Mollusca and Brachiopoda have been identified, including the new species Terrakea capillata Waterhouse. The presence of Strophalosia cf. subcircularis Clarke indicates strong links with younger Asselian faunas of eastern and southern Australia (lower Wasp Head, lower Tiverton an...

Palinomorfos pérmicos del subsuelo de la cuenca colorado, en la plataforma del mar Argentino, provincia Buenos Aires

Several pollen and spore species found in the Puelche x-1 off-shore drilling, Colorado Basin, Argentina, are here illustrated. The material is distributed in a section of about 1.500 m, in which two palynozones have been recognized and correlated to the Striatites and Cristatisporites zones defined for the Chaco-Parana basin in Central Argentina. The age is Lower Permian and early Upper Permian, but the basal diamictites might have been deposited during the uppermost Carboniferous. Infrared microscopy was used to photograph dark specimens not determinable under normal light conditions.