Geology of the Golfo San Jorge Basin, Argentina. Geología de la Cuenca del Golfo San Jorge, Argentina.
TL;DR: La cuenca del Golfo San Jorge (Golfo san Jorge) as mentioned in this paper is the most prolifica productora de petroleo de la Argentina, ubicandose sus reservas in segundo lugar tras de la Cuenca Neuquina.
Abstract: La cuenca del Golfo San Jorge esta ubicada en la Patagonia central, entre las latitudes 44° y 47°S, cubriendo una superficie de aproximadamente 170.000 km2. Es la mas prolifica productora de petroleo de la Argentina, ubicandose sus reservas en segundo lugar tras de la Cuenca Neuquina. De tipo intracratonica, predominantemente extensional, tiene una orientacion general E-W, desde la Cordillera de los Andes al Oceano Atlantico; su basamento economico esta compuesto por un complejo volcanico-sedimentario, asociado a un proceso de rift de edad Jurasico Medio a Superior. Posteriormente, comienza el ciclo sedimentario Neocomiano, bajo condiciones de rift tardio, cuyos depositos se encuentran rellenando sintectonicamente los grabenes y hemigrabenes con sedimentos lacustres y esporadicas transgresiones marinas del Pacifico. Luego de un basculamiento regional del eje principal de la cuenca hacia el Este, comienza el ciclo sedimentario Chubutiano. La Formacion Pozo D-129 (Barremiano-Aptiano), de origen principalmente lacustre, es la roca madre mas importante de la cuenca. Sobreyaciendo a esta unidad, un conjunto de sedimentos fluviales y lacustres someros se depositan en condiciones de subsidencia termal generalizada. Estos depositos contienen los reservorios con las mayores acumulaciones de hidrocarburos de la cuenca. Durante el Terciario se alternan depositos marinos y continentales. La fase compresional principal levanta la Faja Plegada de San Bernardo, de sentido N-S, por inversion tectonica de estructuras distensivas preexistentes. Los depositos glaciales del Cuaternario, representan un drastico cambio climatico. La actividad volcanica a lo largo de la historia de la cuenca se refleja en la alta participacion de material tobaceo en la columna sedimentaria, afectando la calidad de los reservorios. La generacion y posterior expulsion del petroleo comienza hace 80-50 Ma. La migracion se ve favorecida por la presencia de fallas, que originan una red de migracion a traves de la cual los hidrocarburos alcanzan los niveles reservorio, para alojarse finalmente en trampas estructurales, estratigraficas y combinadas.
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TL;DR: The evolution of Patagonia as an independent and exotic microcontinent from the rest of South America was a recurrent hypothesis since the XIX century, reaching notoriety during the discussion times of continental drift theory.
250 citations
TL;DR: The Southern Andes have been built through stacking of crustal sheets in discrete periods during the last 100my as discussed by the authors, where rather anhydrous subducted slabs generated a discontinuous arc emplaced in the foreland area at the time of mountain building.
140 citations
University of New Hampshire1, Pennsylvania State University2, National University of Comahue3, Utrecht University4, National Museum of Natural History5, University of Arizona6, University of Wisconsin-Madison7, National Scientific and Technical Research Council8, National University of La Plata9, Boise State University10, University of Buenos Aires11
TL;DR: In this paper, a multi-disciplinary geochronologic study of the Salamanca Formation and overlying Rio Chico Group in the western part of the San Jorge Basin (Patagonia, Argentina) is presented.
Abstract: The Salamanca Formation of the San Jorge Basin (Patagonia, Argentina) preserves critical records of Southern Hemisphere Paleocene biotas, but its age remains poorly resolved, with estimates ranging from Late Cretaceous to middle Paleocene. We report a multi-disciplinary geochronologic study of the Salamanca Formation and overlying Rio Chico Group in the western part of the basin. New constraints include (1) an 40Ar/39Ar age determination of 67.31 ± 0.55 Ma from a basalt flow underlying the Salamanca Formation, (2) micropaleontological results indicating an early Danian age for the base of the Salamanca Formation, (3) laser ablation HR-MC-ICP-MS (high resolution-multi collector-inductively coupled plasma-mass spectrometry) U-Pb ages and a high-resolution TIMS (thermal ionization mass spectrometry) age of 61.984 ± 0.041(0.074)[0.100] Ma for zircons from volcanic ash beds in the Penas Coloradas Formation (Rio Chico Group), and (4) paleomagnetic results indicating that the Salamanca Formation in this area is entirely of normal polarity, with reversals occurring in the Rio Chico Group. Placing these new age constraints in the context of a sequence stratigraphic model for the basin, we correlate the Salamanca Formation in the study area to Chrons C29n and C28n, with the Banco Negro Inferior (BNI), a mature widespread fossiliferous paleosol unit at the top of the Salamanca Formation, corresponding to the top of Chron C28n. The diverse paleobotanical assemblages from this area are here assigned to C28n (64.67–63.49 Ma), ∼2–3 million years older than previously thought, adding to growing evidence for rapid Southern Hemisphere floral recovery after the Cretaceous-Paleogene extinction. Important Peligran and “Carodnia” zone vertebrate fossil assemblages from coastal BNI and Penas Coloradas exposures are likely older than previously thought and correlate to the early Torrejonian and early Tiffanian North American Land Mammal Ages, respectively.
113 citations
TL;DR: Mitrovica et al. as discussed by the authors found that the early Holocene sea-level rise reached the modern coastline by 8100 14C years ago (c. 8600 14C) at the latest.
91 citations
TL;DR: In this paper, structural, 2D and 3D seismic data at the San Bernardo FTB and the adjacent Rio Mayo Basin were analyzed to unravel the different evolutionary stages of the Chubut Group Basin.
86 citations
References
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TL;DR: In this article, the Cretaceous Chubut Group, San Jorge Basin, Argentina, was studied in outcrop to provide analogs for adjacent subsurface hydrocarbon-bearing strata.
Abstract: Fluvial deposits of the Cretaceous Chubut Group, San Jorge Basin, Argentina, were studied in outcrop to provide analogs for adjacent subsurface hydrocarbon-bearing strata. Outcrops were described using photomosaics and detailed sedimentological logs. Particular attention was paid to describing the geometry (e.g., width, thickness), lithofacies, and spatial distribution of sandstone bodies. Sediment accumulation rates were calculated using radiometric ages obtained from the tuffs and ignimbrites that are an important component of these strata. Interpretation of depositional environment included quantitative reconstruction of the geometry, hydraulics, and mode of migration of paleochannels. The proportion, connectedness, and spatial distribution of channel-belt sandstone bodies were interpreted using alluvial stratigraphy models. Sandstone bodies are generally meters thick and tens to hundreds of meters across (normal to paleocurrent direction). Channel-form sandstone bodies represent channel bars and fills within channel belts, whereas sandstone sheets, wedges, and lenses represent the deposits of overbank sheet floods, levees, and crevasse splays, respectively. Most of the rivers were single-channel and sinuous (sinuosity less than 1.2), but there were also braided rivers. The rivers flowed eastward and were perennial. Individual channel widths were on the order of tens of meters (mainly 35 to 65 m) and maximum channel depths were on the order of meters (mainly 2 to 6 m). The thickest and widest sandstone bodies (up to 16 m thick and in excess of 1 km wide) represent the largest channel belts or superimposed channel belts. Inasmuch as the proportion of channel-belt deposits is generally less than 0.5, most channel belts are unconnected. Channel-deposit proportion varies laterally and vertically on a 100-m scale. These variations are related to changes in the dimensions of channel belts, but they may also be related to variations in the deposition rate, floodplain width, and the timing and location of avulsions. These factors may in turn be related to intrinsic fluvial processes, tectonic tilting of the floodplain, or variations in sediment supply related to climate, tectonism, and igneous activity. Thickness and orientation of the sandstone bodies are similar to those interpreted from adjacent subsurface data. However, the width of subsurface sandstone bodies estimated from well-to-well correlation is greater than measured in outcrop. This discrepancy is because: (1) subsurface sandstone-body width less than the well spacing (typically 300 m) cannot be resolved; (2) the width of some of the subsurface sandstone bodies may be overestimated in well-to-well correlation; and (3) the full extent of the widest sandstone bodies cannot be observed in the smaller outcrops.
170 citations
TL;DR: The limits of three distinct upper Palaeozoic to lower Mesozoic tectono-stratigraphic zones of the ancestral Pacific margin of Gondwana in southern South America are documented in this paper.
Abstract: The limits of 3 distinct upper Palaeozoic to lower Mesozoic tectono-stratigraphic zones of the ancestral Pacific margin of Gondwana in southern South America are documented These are: a fore-arc region consisting in part of ‘oceanic’ components; a magmatic arc that is coincident with Carboniferous to Triassic continental sedimentation; and a back-arc region comprising the upper Palaeozoic epicratonic sequences of the ‘Samfrau Geosyncline’ These zones, traceable 2300 km from 29–56 ° S (Cape Horn), document the semi-continuous subduction of the ancestral Pacific floor from the Middle Devonian to the Triassic Between 29 ° S and 37 ° S the palaeo-subduction zone was roughly coincident with the present Pacific coast line Between 37 ° S and Cape Horn, the subduction zone migrated progressively westward as an ‘Alaskan’ style accretionary prism grew to a width of 250 km While in the northern sector, Jurassic are intrusions are coincident with the upper Palaeozoic are intrusions, in the S they intruded the upper Palaeozoic to lower Mesozoic accretionary prism 200 km W of their Palaeozoic equivalents No post middle Palaeozoic ‘sutures’ have been identified in southern South America Hence, there is no evidence of late Palaeozoic, Mesozoic, or Cenozoic accretion of discrete microplates
160 citations
TL;DR: The age and significance of sequence boundaries on Jurassic to Early Cretaceous rifted continental margins in three ocean basins have been documented in this article, where large industry data bases were used for the interpretation of each area.
Abstract: The age and significance of sequence boundaries on Jurassic to Early Cretaceous rifted continental margins in three ocean basins have been documented. The margins are the Santos basin in the South Atlantic, the Grand Banks in the North Atlantic, and the Beaufort Sea in the Arctic Ocean. Large industry data bases were used for the interpretation of each area. Megasequence boundaries separate the major phases of basin evolution, for example syn-rift and post-rift. Boundaries developed with an average periodicity of 49 m.y. Sequence boundaries define the component parts of each megasequence and developed with a modal periodicity of 10-15 m.y. Out of 27 total boundary ages, most (16) are developed on just one margin. Only two possible age ranges overlap on all three margins. ighty percent of the megasequence boundaries and 50% of the sequence boundaries show a direct causal connection with coeval faulting and/or folding. The rest of the boundaries appear as unstructured surfaces separating transgressive and/or regressive sedimentary wedges and are interpreted to result from changes in the rate of basin subsidence, sediment input, and long-term eustatic sea level. These data do not support theories advocating synchronous worldwide boundary development resulting from periodic, short-term falls in global eustatic sea level. Only in like basins of the same age, with identical subsidence and sediment input rates, are boundaries likely to develop synchronously. Hence, the concept of global synchroneity of sequence boundary development may well be an illusion creat d by the similarity in age of the majority of basins studied. As a result of this study, it seems wise discard the global approach to basin analysis.
156 citations
Book•
03 Oct 2014
TL;DR: In this paper, the authors bridge the gap between process-related outcrop studies of sedimentary rocks and three-dimensional subsurface world of the mineral fuel geologist and hydrogeologist.
Abstract: This edition bridges the gap between process-related outcrop studies of sedimentary rocks and three-dimensional subsurface world of the mineral fuel geologist and hydrogeologist. It focuses on the application of subsurface facies analysis to problems of petroleum, coal, uranium, and ground water resource discovery, delineation, and production. New chapters summarize applications of sequence stratigraphy to facies analysis and the use of detailed facies interpretation in reservoir and aquifer characterization.
139 citations
TL;DR: The San Jorge basin is the most important hydrocarbon-producing basin in Argentina as discussed by the authors, and the remaining untested potential is high because of the presence of good source rock, favorable structural complexity, and multiple reservoirs.
Abstract: The San Jorge basin, although small, is the most important hydrocarbon-producing basin in Argentina. Remaining untested potential is high because of the presence of good source rock, favorable structural complexity, and multiple reservoirs. Reservoir quality is commonly low because of the highly tuffaceous sandstones. The sedimentary fill of the basin is closely related to its tectonic history. Northwest-southeast-trending grabens formed and filled during a Triassic and Early Jurassic early rift phase, climaxing with a pervasive Middle Jurassic volcanic episode; continued growth and filling of the basin occurred during a Late Jurassic-earliest Cretaceous late rift phase and Cretaceous early and late sag phases. Late Cretaceous-early Tertiary extension set up many of the present-day structural traps along normal faults. Middle Tertiary Andean compression produced the narrow, north-south San Bernardo structural belt, which exhibits reversed movement on older, normal, graben-bounding faults and on local, low-angle thrust faults. Marked early to middle Tertiary erosion produced a significant unconformi y within Cretaceous beds around basin margins. Origin of Upper Jurassic and lowermost Cretaceous sedimentary fill is primarily lacustrine or fluvial in origin. Lacustrine, organic-rich black shales are fringed by oolitic and other limestones and fluvial-deltaic sandstones derived mostly from the north. A significant southern source of sand existed during the Valanginian. Interbedded marine shales occur mostly to the west toward a presumed marine seaway connection to the northern Magallanes basin. Middle to Upper Cretaceous sedimentary rocks, sourced mostly from the north, are mainly fluvial sandstone-shale successions with some minor lacustrine influence. Reservoir-quality glauconitic sands were deposited during a Late Cretaceous-early Tertiary marine incursion from the Atlantic. After development of a lower Tertiary regional unco formity, relatively undisturbed younger Tertiary sediments completed the basin fill. Lower Cretaceous lacustrine shales of the D-129 Formation are the best source rocks yet identified. However, most hydrocarbon production occurs above the source in middle and Upper Cretaceous sandstones along the basin flanks. The most obvious hydrocarbon emplacement mechanism is vertical migration along reactivated graben faults.
131 citations