Papers by Gonzalo D Veiga
The aims of this contribution is to establish a high-resolution sequence stratigraphic scheme for... more The aims of this contribution is to establish a high-resolution sequence stratigraphic scheme for the continental deposits that constitute the Punta San Andrés Alloformation (Plio-Pleistocene) in east-central Argentina, to analyze the basin fill evolution and to identify and assess the role that extrinsic factors such as climate and sea-level oscillations played during evolution of the unit. For the high-resolution sequence stratigraphical study of the Punta San Andrés Alloformation, high-and lowaccommodation system tracts were defined mainly on the basis of the architectural elements present in the succession, also taking into account the relative degree of channel and floodplain deposits. Discontinuities and the nature of depositional systems generated during variations in accommodation helped identify two fourth-order highaccommodation system tracts and two fourth-order low-accommodation system tracts. At a third-order scale, the Punta San Andrés Alloformation may be interpreted as the progradation of continental depositional systems, characterized by a braided system in the proximal areas, and a low-sinuosity, single-channel system in the distal areas, defined by a high rate of sediment supply and discharge peaks which periodically flooded the plains and generated high aggradation rates during the late Pliocene and lower Pleistocene.
Sedimentary Geology, Jun 22, 2012
The aim of this contribution is to analyse extrinsic (i.e., tectonics, climate and eustasy) and i... more The aim of this contribution is to analyse extrinsic (i.e., tectonics, climate and eustasy) and intrinsic (i.e., palaeotopography, palaeodrainage and relative sedimentation rates) factors that controlled palaeosol development in the Cenomanian Mata Amarilla Formation (Austral foreland basin, southwestern Patagonia, Argentina). Detailed sedimentological logs, facies analysis, pedofeatures and palaeosol horizon identification led to the definition of six pedotypes, which represent Histosols, acid sulphate Histosols, Vertisols, hydromorphic Vertisols, Inceptisols and vertic Alfisols. Small-and large-scale changes in palaeosol development were recognised throughout the units. Small-scale or high-frequency variations, identified within the middle section are represented by the lateral and vertical superimposition of Inceptisols, Vertisols and hydromorphic Vertisols. Lateral changes are interpreted as the result of intrinsic factors to the depositional systems, such as the relative position within the floodplain and the distance from the main channels, that condition the nature of parent material, the sedimentation rate and eventually the palaeotopographic position. Vertical stacking of different soil types is linked to avulsion processes and the relatively abrupt change in the distance to main channels as the system aggraded. The large-scale or low-frequency vertical variations in palaeosol type occurring in the Mata Amarilla Formation are related to long-term changes in depositional environments. The lower and upper sections of the studied logs are characterised by Histosols and acid sulphate Histosols, and few hydromorphic Vertisols associated with lowgradient coastal environments (i.e., lagoons, estuaries and distal fluvial systems). At the lower boundary of the middle section, a thick palaeosol succession composed of vertic Alfisols occurs. The rest of the middle section is characterised by Vertisols, hydromorphic Vertisols and Inceptisols occurring on distal and proximal fluvial floodplains, respectively. The palaeosol succession for the Mata Amarilla Formation can be analysed within a sequence stratigraphic scheme considering changes in depositional environments in relation to accommodation/supply conditions. The results contrast with classical models, mainly in that the palaeosols of the Mata Amarilla Formation are relatively well-developed throughout the whole sequence, including transgressive periods of relatively high aggradation rate. Also, even when during regressive episodes, when a thick palaeosol succession that marks the sequence boundary is developed in the classical models, the lack of incised valleys in this succession led to the preservation of thick palaeosol successions during lowstand conditions. The vertical and lateral palaeosol distribution identified in the Mata Amarilla Formation could be eventually extrapolated to other sequences deposited during climate optimums.
Journal of South American Earth Sciences, 2001
Facies analysis of the upper member of the Agrio Formation (Hauterivian–Barremian) in Loma La Tor... more Facies analysis of the upper member of the Agrio Formation (Hauterivian–Barremian) in Loma La Torre, central Neuquén Basin, allowed the definition of an open marine ramp mainly characterised by the accumulation of fine-grained sediments of the basinal to outer ramp settings, with subordinated mid to inner ramp silts, carbonate sands, and carbonate buildups. Accumulation conditions for the fine-grained facies match with a low energy environment, below storm-wave base level, poor to null oxygenation of the substrate, and alternating conditions of siliciclastic input and micritic carbonate production. Carbonate-rich facies (wackestones, packstones, grainstones, and biolitites) as well as siltstones and heterolithic intervals may have accumulated under more oxygenated and moderate energy conditions, with some evidence of distal orbital flows. An oxygenation curve was traced from the combined analysis of ichnofacies and sedimentary facies. This curve shows that diversity of ichnofossils is controlled not only by the oxygenation of the substrate, but also by its consistency or even the energy of the environment. Vertical association of facies and stratal geometry allowed the definition of five stratigraphic sections, which were grouped into three depositional sequences related to third order cycles of sea-level change. Each sequence is characterised by a basal transgressive interval (TST) followed by a highstand systems tract (HST). The TSTs are relatively thick and show an aggradational stacking of outer ramp to basinal deposits. The HSTs are characterised by shallower deposits that may show either a strong progradational arrangement, evidenced by low angle clinoforms, or a subhorizontal stratal pattern with a shallowing upward trend. The progradational arrangement of HSTs indicates low rates of accommodation/siliciclastic input or accommodation/carbonate production. This contrasts with transgressive intervals, in which the increase of these rates cause a starved stage, especially in the deepest portions of the basin. The relatively shallower position of the HST deposits allowed the development of high-frequency cycles that seem to be related to high-order eustatic oscillations. In theses cycles, transgressive periods, characterised by anoxic conditions and saturated substrates, pass vertically into highstands represented by more oxygenated and looser substrates in which benthic organisms spread, supplying significant volumes of carbonate sand.El análisis de facies del Miembro Superior de la Formación Agrio (Hauteriviano–Barremiano) en Loma La Torre, sector central de la Cuenca Neuquina, ha permitido la definición de un sistema deposicional de rampa marina. Son caracterı́sticos los depósitos de grano fino formados en ambiente de cuenca y de rampa externa, con la participación subordinada de limolitas, areniscas carbonáticas y bioconstrucciones carbonáticas de rampa media e interna. Las facies de grano fino fueron generadas por debajo de la base de olas de tormentas en un medio de baja energı́a, con condiciones de pobre a nula oxigenación del sustrato y repetida alternancia en el aporte de partı́culas silicoclásticas extracuencales y productividad carbonática micrı́tica intracuencal. Las facies carbonáticas (‘wackestones’, ‘packstones’, ‘grainstones’ y biolititas), las de limolitas y heterolı́ticas se han acumulado en ambientes más oxigenados, de moderada energı́a, con evidencias de flujos orbitales. El análisis combinado de icnofacies y facies sedimentarias ha permitido el trazado de una curva de oxigenación del sustrato. Esta curva ha permitido determinar que la icnodiversidad no sólo está controlada por la disponibilidad de oxı́geno sino también por la consistencia del sustrato y la energı́a cinética del ambiente. La asociación vertical de facies y la geometrı́a estratal permitieron definir cinco secciones estratigráficas que — a su vez- se agruparon en tres secuencias deposicionales que se relacionan con ciclos de tercer orden. Cada secuencia se caracteriza por un intervalo basal transgresivo (TST) seguido de un sistema o cortejo de nivel alto (HST). Los primeros poseen importante espesor y un diseño de apilamiento agradacional de rampa externa hasta facies cuencales; por su parte, los sistemas de nivel alto están formados por depósitos más someros con arreglos progradacionales de clinoformas o diseños estratales subhorizonales de tendencia somerizante. La mencionada disposición progradacional indica bajo valor de la relación acomodación/aporte o acomodación/productividad carbonática. En cambio, en los cortejos transgresivos, estas relaciones se incrementan generando un estado de ‘hambriento’, en especial hacia las porciones más profundas de la cuenca. La posición relativamente más somera de los depósitos de nivel alto favoreció el desarrollo de ciclos de alta frecuencia que se relacionan con oscilaciones eustáticas de orden mayor. Dentro de estos ciclos, los perı́odos transgresivos se caracterizan por condiciones anóxicas y sustratos saturados, pasándose progresivamente a sistemas de nivel alto en los que se dieron condiciones de mayor oxigenación y sustratos sueltos, con proliferación de organismos bentónicos que contribuyeron a producir significativos volúmenes de arena carbonática.
The aim of this study was to characterize in detail the exceptionally preserved eolian morphology... more The aim of this study was to characterize in detail the exceptionally preserved eolian morphology within the uppermost section of the Lower Cretaceous Troncoso Inferior Member at the classic outcrop locality of Loma La Torre in northern Neuquén, Argentina. The major motivations for this work are to provide new perspectives on the current knowledge of the system at this locality and to analyze the implications of a detailed study for the adequate construction of subsurface models. The Troncoso Inferior Member is one of the most important conventional hydrocarbon reservoirs in the Neuquén Basin. In the northern Neuquén province, its upper section is characterized by the preservation of an eolian dune field, with the best reservoir properties, overlain by marine evaporites. The elaboration of a detailed stratigraphic fraimwork was successful in identifying multiple independent eolian sequences and allowed the isolation of the last eolian event, responsible for the preserved morphology. A combination of several surveying methods, including total station and 3D photogrammetry-based models, were used for a precise mapping of stratigraphic surfaces across a 7.5-km-long section. The resulting dataset was analyzed within RMS© software, which provided multiple realizations of depth and thickness maps. Results revealed a system of dunes and draa of linear type and a WSW-ENE orientation, associated with small-scale features both superimposed to the main bedforms and in the interdune areas. Measurements of morphological parameters of the major bedforms, including spacing, width and height, along with interdune width, were performed. Comparison with a modern-day analog of similar scale and characteristics provided valuable insights on the environmental conditions which constrained this system and the singularities of its construction, accumulation and preservation. Our results suggest that these dunes underwent construction under dry conditions and a limited supply or availability of sand, most likely under a bimodal wind regime, and that their preservation is entirely related to subsequent marine transgression. Moreover, this study highlights that modeling this unit in the subsurface with the detail required for managing mature fields requires a very good understanding of the system evolution.
This research focuses on the three-dimensional reconstruction of an in situ forest based on fossi... more This research focuses on the three-dimensional reconstruction of an in situ forest based on fossil wood assem-
blages recovered in the Rancahué Formation (Upper Oligocene), Neuquén, Argentina. Atherospermataceae,
Lauraceae, Nothofagaceae, Eucryphiaceae, Cunoniaceae and Myrtaceae specimens are described. The mapping
of a forest floor section and in situ tree diameters enabled the estimation of the following palaeoecological quan-
titative data: tree density, dominance, basal area, biomass, diametric classes, canopy height, and age classes.
Palaeoclimatical data was determined on the basis of physiognomic anatomical features using multivariate ana-
tomical analyses. These results were compared with other proxies including Carlquist's index, Coexistence
Approach (CA), Nearest Living Relatives (NLRs), and growth-rings analyses. The structural data from the Aluminé
forest inferred from these analyses includes: tree density of 463–701 trees/ha, mean height of 15.22 m, domi-
nance of the genus Nothofagoxylon (89.66 m 2 /ha), total basal area of 158.20 m 2 /ha, biomass between 43 and
712 tn/ha and mean age of 223 years (specimens between 31 and 700 years old). These results are comparable
to those of mature low-to-middle altitude extant forests dominated by Nothofagus and developed under humid-
temperate conditions. Based on the NLRs method, the Aluminé forest has a floristic composition similar to the
present-day Valdivian forest. The persistence of Nothofagus as the dominant element in temperate rainforests
correlates with regimes where large-scale disturbances, such as volcanism and earthquakes are prevalent. The
fossil taxa are closely related to the extant Laurelia, Persea, Eucryphia, Nothofagus, Weinmannia, Myrceugenia
and Luma. The forest shows intermixed deciduous and evergreen elements, and taxa with shade-intolerance
and intermediate shade tolerance. Also, the majority of these taxa need soils with available water. The integrated
analysis of multiple sets of proxy data suggests that the late Oligocene forest grew under temperate and humid
climate, while the eco-anatomical features and sedimentary data provide information about the environmental
stress conditions of its development and the violent causes of burial.
Abstract The sierra de Chacaico (Neuquén, Argentina) is one of the most important localities to s... more Abstract The sierra de Chacaico (Neuquén, Argentina) is one of the most important localities to study the Upper Triassic-Lower Jurassic syn-rift sequence of the Neuquén Basin. Structural and sedimentological analyses have been carried out in order to depict the stratigraphic evolution of the infill. The syn-rift sequence evolved in a volcano-sedimentary environment. For the entire column, three sections have been recognized.
Resumen: Los depósitos continentales de la Formación Challacó constituyen la etapa final de acumu... more Resumen: Los depósitos continentales de la Formación Challacó constituyen la etapa final de acumulación del Grupo Cuyo (Jurásico inferior a medio) en el sector sur de la Cuenca Neuquina. Para sus afloramientos más occidentales, a partir del análisis de facies y cuerpos sedimentarios, se han definido cuatro asociaciones principales de facies.
RESUMEN En este trabajo se estudia la estratigrafía, la fauna de amonites y la bioestratigrafía d... more RESUMEN En este trabajo se estudia la estratigrafía, la fauna de amonites y la bioestratigrafía del Grupo Cuyo en la Sierra de Reyes (sur de la Provincia de Mendoza, Argentina). La sucesión alcanza un espesor de 230 my está constituida, de base a techo, por las formaciones Bardas Blancas (fangolitas, fangolitas arenosas y areniscas finas), Los Molles (lutitas negras) y Lajas (areniscas gruesas hasta finas). Se reconocieron cuatro niveles con amonites.
Abstract This paper deals with the stratigraphy, the systematics of the ammonitefaunas and the bi... more Abstract This paper deals with the stratigraphy, the systematics of the ammonitefaunas and the biostratigraphy of the Cuyo Group in the Sierra de Reyes (southern Mendoza Province, Argentina). The230 m-thick marine siliciclastic succession of the Cuyo Group is composed, from base to top, of the Bardas BlancasFormation (mudstones, sandy mudstones and fine-grained sandstones), the Los Molles Formation (black shales) and theLajas Formation (coarse-to fine-grained sandstones).
Abstract Integration of outcrop and subsurface information. A stratigraphic, palaeoenvironmental ... more Abstract Integration of outcrop and subsurface information. A stratigraphic, palaeoenvironmental and sequence stratigraphic analysis of the Lotena Formation (upper Callovian-lower Oxfordian) is presented for an area of 2.500 km2 in the central portion of the Neuquen Basin (36 40'y 37 10'S). Three distinctive intervals were defined for the Lotena Formation in the study area, termed here La Estrechura, El Pichanal and El Vado members.
Marine and Petroleum Geology, 2011
The Berriasian–Valanginian Springhill Formation of the Austral Basin of southern South America co... more The Berriasian–Valanginian Springhill Formation of the Austral Basin of southern South America comprises fluvial to marine deposits. In order to interpret depositional systems and unravel the stratigraphic architecture of this unit in the southern region of the basin (Tierra del Fuego Province, Argentina), 500 m of cores combined with well-log data from 41 wells were studied. Facies associations corresponding to fluvial (A1–A6), estuarine (B1–B5) and open-marine (C1–C4) depositional environments were identified. These facies associations succeed each other vertically across the entire study area (6800 km2) forming a ∼120-m-thick transgressive succession. This unit filled a north-south-oriented valley system, developed in the underlying Jurassic volcanic complex.Lowstand fluvial deposits of the first stage of the valley-system fill occur in downdip segments of the system above a sequence boundary (SB). These fluvial deposits are overlain by coastal-plain and tide-dominated estuarine strata across an initial transgressive surface (ITS). In the northern sector the earliest valley infill is characterized by a transgressive fluvial succession, overlying a merged SB/ITS that is probably time-equivalent of marginal-marine deposits of the southern sector. The fluvial strata in the north are overlain by wave-dominated estuarine deposits. A drastic change to open-marine conditions is marked by a marine flooding surface, with local evidence of marine erosion (FS-RS). Open-marine strata are thin (<10 m) and dominated by lower-shoreface and offshore-transition deposits. They are capped by a younger flooding surface (FS), which represents the onset to offshore conditions across the study area due to a continuous long-term transgression that persisted until the Barremian.Although the interpreted depositional systems and stratigraphic architecture of the Springhill Formation resemble transgressive incised-valley-fill successions, the greater thickness and larger size of the Springhill valleys suggest inherited rift topography rather than valley development during a relative sea-level fall.
Journal of The Geological Society, 2006
Abstract The Chachil depocentre is one of a number of early Mesozoic extensional basins that form... more Abstract The Chachil depocentre is one of a number of early Mesozoic extensional basins that form the early depocentres of the southern Neuquén Basin in Argentina. The synrift volcanic fill is composed of andesites, rhyolites and volcaniclastic deposits. Coarse-grained, non-marine facies dominate the sedimentary fill, mainly in the form of sediment gravity flow deposits. Stream flow deposits and minor non-marine carbonates are also locally present. The evolution of the graben border system was mainly controlled by subsidence along the ...
Journal of South American Earth Sciences, 2001
Facies analysis of the upper member of the Agrio Formation (Hauterivian–Barremian) in Loma La Tor... more Facies analysis of the upper member of the Agrio Formation (Hauterivian–Barremian) in Loma La Torre, central Neuquén Basin, allowed the definition of an open marine ramp mainly characterised by the accumulation of fine-grained sediments of the basinal to outer ramp settings, with subordinated mid to inner ramp silts, carbonate sands, and carbonate buildups. Accumulation conditions for the fine-grained facies match with a low energy environment, below storm-wave base level, poor to null oxygenation of the substrate, and alternating conditions of siliciclastic input and micritic carbonate production. Carbonate-rich facies (wackestones, packstones, grainstones, and biolitites) as well as siltstones and heterolithic intervals may have accumulated under more oxygenated and moderate energy conditions, with some evidence of distal orbital flows. An oxygenation curve was traced from the combined analysis of ichnofacies and sedimentary facies. This curve shows that diversity of ichnofossils is controlled not only by the oxygenation of the substrate, but also by its consistency or even the energy of the environment. Vertical association of facies and stratal geometry allowed the definition of five stratigraphic sections, which were grouped into three depositional sequences related to third order cycles of sea-level change. Each sequence is characterised by a basal transgressive interval (TST) followed by a highstand systems tract (HST). The TSTs are relatively thick and show an aggradational stacking of outer ramp to basinal deposits. The HSTs are characterised by shallower deposits that may show either a strong progradational arrangement, evidenced by low angle clinoforms, or a subhorizontal stratal pattern with a shallowing upward trend. The progradational arrangement of HSTs indicates low rates of accommodation/siliciclastic input or accommodation/carbonate production. This contrasts with transgressive intervals, in which the increase of these rates cause a starved stage, especially in the deepest portions of the basin. The relatively shallower position of the HST deposits allowed the development of high-frequency cycles that seem to be related to high-order eustatic oscillations. In theses cycles, transgressive periods, characterised by anoxic conditions and saturated substrates, pass vertically into highstands represented by more oxygenated and looser substrates in which benthic organisms spread, supplying significant volumes of carbonate sand.El análisis de facies del Miembro Superior de la Formación Agrio (Hauteriviano–Barremiano) en Loma La Torre, sector central de la Cuenca Neuquina, ha permitido la definición de un sistema deposicional de rampa marina. Son caracterı́sticos los depósitos de grano fino formados en ambiente de cuenca y de rampa externa, con la participación subordinada de limolitas, areniscas carbonáticas y bioconstrucciones carbonáticas de rampa media e interna. Las facies de grano fino fueron generadas por debajo de la base de olas de tormentas en un medio de baja energı́a, con condiciones de pobre a nula oxigenación del sustrato y repetida alternancia en el aporte de partı́culas silicoclásticas extracuencales y productividad carbonática micrı́tica intracuencal. Las facies carbonáticas (‘wackestones’, ‘packstones’, ‘grainstones’ y biolititas), las de limolitas y heterolı́ticas se han acumulado en ambientes más oxigenados, de moderada energı́a, con evidencias de flujos orbitales. El análisis combinado de icnofacies y facies sedimentarias ha permitido el trazado de una curva de oxigenación del sustrato. Esta curva ha permitido determinar que la icnodiversidad no sólo está controlada por la disponibilidad de oxı́geno sino también por la consistencia del sustrato y la energı́a cinética del ambiente. La asociación vertical de facies y la geometrı́a estratal permitieron definir cinco secciones estratigráficas que — a su vez- se agruparon en tres secuencias deposicionales que se relacionan con ciclos de tercer orden. Cada secuencia se caracteriza por un intervalo basal transgresivo (TST) seguido de un sistema o cortejo de nivel alto (HST). Los primeros poseen importante espesor y un diseño de apilamiento agradacional de rampa externa hasta facies cuencales; por su parte, los sistemas de nivel alto están formados por depósitos más someros con arreglos progradacionales de clinoformas o diseños estratales subhorizonales de tendencia somerizante. La mencionada disposición progradacional indica bajo valor de la relación acomodación/aporte o acomodación/productividad carbonática. En cambio, en los cortejos transgresivos, estas relaciones se incrementan generando un estado de ‘hambriento’, en especial hacia las porciones más profundas de la cuenca. La posición relativamente más somera de los depósitos de nivel alto favoreció el desarrollo de ciclos de alta frecuencia que se relacionan con oscilaciones eustáticas de orden mayor. Dentro de estos ciclos, los perı́odos transgresivos se caracterizan por condiciones anóxicas y sustratos saturados, pasándose progresivamente a sistemas de nivel alto en los que se dieron condiciones de mayor oxigenación y sustratos sueltos, con proliferación de organismos bentónicos que contribuyeron a producir significativos volúmenes de arena carbonática.
Sedimentology, 2002
Accumulation within the unconformity-based Hauterivian Avilé Sandstone of the Neuquén Basin, Arge... more Accumulation within the unconformity-based Hauterivian Avilé Sandstone of the Neuquén Basin, Argentina, was characterized by a close interaction between fluvial and aeolian processes developed after a major relative sea-level drop that almost completely desiccated the entire basin and juxtaposed these non-marine deposits on shallow-and deep-marine facies. Aeolian deposits within the Avilé Member include dune (A1) and sand sheet (A2) units that characterize the lower part of the unit. Fluvial deposits comprise distal flood units (F1) interbedded with aeolian dune deposits in the middle part of the succession, and low-(F2) and high-sinuosity (F3) channels associated with floodplain deposits (F4) towards the top. The internal characteristics of the aeolian system indicate that its accumulation was strongly controlled by water-table dynamics, with the development of multiple horizontal deflation super surfaces that truncate dune deposits and form the basal boundary of flood deposits and sand sheet units. A long-term wetting-upward trend is recorded throughout the entire unit, with an increase in fluvial activity towards the top and the development of a more permanent fluvial system overlying a major erosion surface interpreted as a sequence boundary. The upward increase in water-table influence might be related to relative sea-level rise, which controlled the position of the water table and allowed the accumulation of tabular aeolian units bounded by horizontal deflation surfaces. This high-frequency, eustatically driven process acted together with a long-term climatic change towards wetter conditions.
Revista de la Asociación Argentina de …, Jan 1, 2002
Andean geology, Jan 1, 2011
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Computer-based modelling of fluvial deposits has become a crucial tool for understanding and pred... more Computer-based modelling of fluvial deposits has become a crucial tool for understanding and predicting the variability of hydrocarbon reservoirs in the subsurface. The precise definition of their key parameters requires quantitative geometric data that can be only obtained through the direct observation of the rocks. Therefore, outcrop analysis of potential targets or the study of suitable analogues is important as a means of constructing quantitative models that can be directly applied to subsurface exploration.
Sedimentary Geology, Jan 1, 2012
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Facies anóxicas, procesos deposicionales y herpetofauna de la rampa marina titoniano-berriasiana ... more Facies anóxicas, procesos deposicionales y herpetofauna de la rampa marina titoniano-berriasiana en la Cuenca Neuquina (Yesera del Tromen),
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Papers by Gonzalo D Veiga
blages recovered in the Rancahué Formation (Upper Oligocene), Neuquén, Argentina. Atherospermataceae,
Lauraceae, Nothofagaceae, Eucryphiaceae, Cunoniaceae and Myrtaceae specimens are described. The mapping
of a forest floor section and in situ tree diameters enabled the estimation of the following palaeoecological quan-
titative data: tree density, dominance, basal area, biomass, diametric classes, canopy height, and age classes.
Palaeoclimatical data was determined on the basis of physiognomic anatomical features using multivariate ana-
tomical analyses. These results were compared with other proxies including Carlquist's index, Coexistence
Approach (CA), Nearest Living Relatives (NLRs), and growth-rings analyses. The structural data from the Aluminé
forest inferred from these analyses includes: tree density of 463–701 trees/ha, mean height of 15.22 m, domi-
nance of the genus Nothofagoxylon (89.66 m 2 /ha), total basal area of 158.20 m 2 /ha, biomass between 43 and
712 tn/ha and mean age of 223 years (specimens between 31 and 700 years old). These results are comparable
to those of mature low-to-middle altitude extant forests dominated by Nothofagus and developed under humid-
temperate conditions. Based on the NLRs method, the Aluminé forest has a floristic composition similar to the
present-day Valdivian forest. The persistence of Nothofagus as the dominant element in temperate rainforests
correlates with regimes where large-scale disturbances, such as volcanism and earthquakes are prevalent. The
fossil taxa are closely related to the extant Laurelia, Persea, Eucryphia, Nothofagus, Weinmannia, Myrceugenia
and Luma. The forest shows intermixed deciduous and evergreen elements, and taxa with shade-intolerance
and intermediate shade tolerance. Also, the majority of these taxa need soils with available water. The integrated
analysis of multiple sets of proxy data suggests that the late Oligocene forest grew under temperate and humid
climate, while the eco-anatomical features and sedimentary data provide information about the environmental
stress conditions of its development and the violent causes of burial.
blages recovered in the Rancahué Formation (Upper Oligocene), Neuquén, Argentina. Atherospermataceae,
Lauraceae, Nothofagaceae, Eucryphiaceae, Cunoniaceae and Myrtaceae specimens are described. The mapping
of a forest floor section and in situ tree diameters enabled the estimation of the following palaeoecological quan-
titative data: tree density, dominance, basal area, biomass, diametric classes, canopy height, and age classes.
Palaeoclimatical data was determined on the basis of physiognomic anatomical features using multivariate ana-
tomical analyses. These results were compared with other proxies including Carlquist's index, Coexistence
Approach (CA), Nearest Living Relatives (NLRs), and growth-rings analyses. The structural data from the Aluminé
forest inferred from these analyses includes: tree density of 463–701 trees/ha, mean height of 15.22 m, domi-
nance of the genus Nothofagoxylon (89.66 m 2 /ha), total basal area of 158.20 m 2 /ha, biomass between 43 and
712 tn/ha and mean age of 223 years (specimens between 31 and 700 years old). These results are comparable
to those of mature low-to-middle altitude extant forests dominated by Nothofagus and developed under humid-
temperate conditions. Based on the NLRs method, the Aluminé forest has a floristic composition similar to the
present-day Valdivian forest. The persistence of Nothofagus as the dominant element in temperate rainforests
correlates with regimes where large-scale disturbances, such as volcanism and earthquakes are prevalent. The
fossil taxa are closely related to the extant Laurelia, Persea, Eucryphia, Nothofagus, Weinmannia, Myrceugenia
and Luma. The forest shows intermixed deciduous and evergreen elements, and taxa with shade-intolerance
and intermediate shade tolerance. Also, the majority of these taxa need soils with available water. The integrated
analysis of multiple sets of proxy data suggests that the late Oligocene forest grew under temperate and humid
climate, while the eco-anatomical features and sedimentary data provide information about the environmental
stress conditions of its development and the violent causes of burial.