Fabrizio Felletti

A database approach for constraining stochastic simulations of the sedimentary heterogeneity of fluvial reservoirs

Quantitative databases storing analog data describing the geometry of sedimentologic features are commonly used to derive input for geostatistical simulations of reservoir sedimentary architecture; however, geometrical information alone is inadequate for the detailed characterization of sedimentary heterogeneity. A relational database storing fluvial architecture data has been developed and populated with literature- and field-derived data from modern rivers and ancient successions. The database scheme characterizes fluvial architecture at three different scales of observation—recording style of internal organization, geometries, and spatial relationships of genetic units—classifying data sets according to controlling factors (e.g., climate type) and context-descriptive characteristics (e.g., river pattern). The database can therefore be filtered on both architectural features and boundary conditions to yield outputs tailored on the system being modeled to generate input to object- and pixel-based stochastic simulations of reservoir architecture. When modeling heterogeneity with stochastic simulations, the choice of input parameters quantifying spatial variation is problematic because of the paucity of primary data and the partial characterization of supposed analogs. This database-driven approach permits the definition of various constraints referring to either genetic units (e.g., architectural elements) or material units (i.e., contiguous volumes of sediment characterized by the same value of a given categorical or discretized variable; e.g., same lithofacies type, clay and silt content, and others), which permit the realistic description of fluvial architecture heterogeneity. Applications of this database approach include the computation of relative dimensional parameters and the generation of auto- and cross-variograms and transition-probability matrices, which are necessary to effectively model spatial complexity.

Planform geometry, stacking pattern, and extrabasinal origin of low strength and intermediate strength cohesive debris flow deposits in the Marnoso-arenacea Formation, Italy

The Miocene Marnoso-arenacea Formation (Italy) is the only ancient sequence where deposits of individual submarine density flow deposits have been mapped in detail for long (>100 km) distances, thereby providing unique information on how such flows evolve. These beds were deposited by large and infrequent flows in a low-relief basin plain. An almost complete lack of bed amalgamation aids bed correlation, and resembles some modern abyssal plains, but contrasts with ubiquitous bed amalgamation seen in fan-lobe deposits worldwide. Despite the subdued topography of this basin plain, the beds have a complicated character. Previous work showed that a single flow can commonly comprise both turbidity current and cohesive mud-rich debris flows. The debris flows were highly mobile on low gradients, but their deposits are absent in outcrops nearest to source. Similar hybrid beds have been documented in numerous distal fan deposits worldwide, and they represent an important process for delivering sediment into the deep ocean. It is therefore important to understand their origin and flow dynamics. To account for the absence of debrites in proximal Marnoso-arenacea Formation outcrops, it was proposed that debris flows originated within the study area due to erosion of mud-rich seafloor; we show that this is incorrect. Clast and matrix composition show that sediment within the cohesive debris flows originated outside the study area. Previous work showed that intermediate and low strength debris flows produced different downflow-trending facies tracts. Here, we show that intermediate strength debris flows entered the study area as debris flows, while low strength (clast poor) debris flows most likely formed through local transformation from an initially turbulent mud-rich suspension. New field data document debrite planform shape across the basin plain. Predicting this shape is important for subsurface oil and gas reservoirs. Low strength and intermediate strength debrites have substantially different planform shapes. However, the shape of each type of debrite is consistent. Low strength debrites occur in two tongues at the margins of the outcrop area, while intermediate strength debrite forms a single tongue near the basin center. Intermediate strength debrites are underlain by a thin layer of structureless clean sandstone that may have settled out from the debris flow at a late stage, as seen in laboratory experiments, or been deposited by a forerunning turbidity current that is closely linked to the debris flow. Low strength debrites can infill relief created by underlying dune crests, suggesting gentle emplacement. Dewatering of basal clean sand did not cause a long runout of debris flows in this location. Hybrid beds are common in a much thicker stratigraphic interval than was studied previously, and the same two types of debrite occur there. Hybrid flows transported large volumes (as much as 10 km3 per flow) of sediment into this basin plain, over a prolonged period of time.

A History of Ideas in Ichnology

Abstract Although the concept of ichnology as a single coherent field arose in the nineteenth century, the endeavor of understanding traces is old as civilization and involved cultural areas worldwide. In fact, fossil and recent traces were recognized since prehistoric times and their study emerged from the European Renaissance. This progression, from empirical knowledge toward the modern concepts of ichnology, formed a major research field which developed on a global scale. This report outlines the history of ichnology by (1) exploring the individual cultural areas, (2) tracing a comprehensive bibliographic database, and (3) analyzing the evolution of ichnology semiquantitatively and in a graphical form (“tree of ichnology”). The results form a review and synthesis of the history of ichnology, establishing the individual and integrated importance of the different ichnological schools in the world.

Connectivity and single/dual domain transport models: tests on a point-bar/channel aquifer analogue

In porous aquifers, groundwater flow and solute transport strongly depend on the sedimentary facies distribution at fine scale, which determines the heterogeneity of the conductivity field; in particular, connected permeable sediments could form preferential flow paths. Therefore, properly defined statistics, e.g. total and intrinsic facies connectivity, should be correlated with transport features. In order to improve the assessment of the relevance of this relationship, some tests are conducted on two ensembles of equiprobable realizations, obtained with two different geostatistical simulation methods—sequential indicator simulation and multiple point simulation (MPS)—from the same dataset, which refers to an aquifer analogue of sediments deposited in a fluvial point-bar/channel association. The ensembles show different features; simulations with MPS are more structured and characterised by preferential flow paths. This is confirmed by the analysis of transport connectivities and by the interpretation of data from numerical experiments of conservative solute transport with single and dual domain models. The use of two ensembles permits (1) previous results obtained for single realizations to be consolidated on a more firm statistical basis and (2) the application of principal component analysis to assess which quantities are statistically the most relevant for the relationship between connectivity indicators and flow and transport properties.RésuméDans les aquifères poreux, l’écoulement d’eau souterraine et le transport de solutés dépend fortement de la distribution des faciès sédimentaires à l’échelle fine, ce qui détermine l’hétérogénéité du champ de conductivité hydraulique; en particulier, les sédiments perméables connectés peuvent donner lieu à des écoulements préférentiels. Ainsi, la connectivité totale et intrinsèque de faciès définie correctement de manière statistique devrait être corrélée avec les propriétés du transport. Afin d’améliorer l’évaluation de la signification de cette relation, des tests ont été menés sur deux ensembles de réalisations équiprobables, obtenues à partir de deux méthodes différentes de simulation numérique—simulation séquentielle à indicateurs et simulation en points multiples (SPM)—construites à l’aide du même jeu de données se rapportant à un analogue aquifère de sédiments déposés dans un environnement fluvial avec une association de barres et de chenaux ponctuels. Les ensembles montrent différentes caractéristiques ; les simulations avec SPM sont plus structurées et caractérisées par des écoulements préférentiels. Ceci est confirmé par l’analyse des connectivités lors du transport et par l’interprétation des données expérimentales numériques de transport conservatif issues de modèles en domaine simple et dual. L’utilisation des deux ensembles permet (1) de consolider des résultats obtenus au préalable pour des réalisations simples sur une base statistique plus solide et (2) l’application de l’analyse en composante principale pour évaluer quelles quantités sont les plus significatives du point de vue statistique pour la relation entre les indicateurs de connectivité et les propriétés d’écoulement et de transport.ResumenEn acuíferos porosos, el flujo del agua subterránea y el transporte de soluto dependen fuertemente de la distribución de las facies sedimentarias a una escala fina, lo cual determina la heterogeneidad del campo de conductividad; en particular los sedimentos permeables conectados pueden forman trayectorias preferenciales de flujo. Por lo tanto, la estadística correctamente definida, por ejemplo la conectividad total e intrínseca de las facies, debe ser correlacionada con las características del transporte. Con el objeto de mejorar la evaluación de la relevancia de esta relación, se llevaron a cabo algunos ensayos en dos conjuntos de realizaciones equiprobables, obtenidas con dos métodos de simulación geoestadística diferente—simulación de indicador secuencial y simulación de múltiples puntos (MPS)—a partir de un mismo conjunto de datos, los cuales se refieren a una analogía de acuífero sedimentos depositados en una asociación albardón/canal fluvial. Los conjuntos muestran diferentes características; las simulaciones con MPS son más estructuradas y caracterizadas por trayectorias preferenciales de flujo. Esto está confirmado por el análisis de las conectividades del transporte y por la interpretación de datos de experimentos numéricos del transporte conservativo de soluto con modelos de dominios simples y dobles. El uso de los dos conjuntos permite (1) consolidar, sobre una base estadística más firme, los resultados previos obtenidos para realizaciones simples y (2) la aplicación del análisis de la componente principal para evaluar cuales cantidades son estadísticamente más relevantes para la relación entre los indicadores de conectividad y las propiedades de flujo y transporte.摘要在孔隙含水层中地下水流和溶质运移强烈依赖于沉积物中颗粒精细分布的特征,它确定了传导场地的不均匀性,特别是相关联的可渗透沉积层形成优先的水流。因而,适当确定统计资料,例如:总的和固有的连通特质,需要关联其运移特征。以便评价其关系,这些实验产生了两个同等的认识,根据相同的资料以两种不同的地质统计方法—序次指标模拟和多重点模拟(MPS)—获得。其利用了沉积地层在水流的点状阻障/通道中含水层模拟评价。整体效果显示出不同的特征,MPS模拟更突出了优先水流的结构和特点。它根据分析传导连通性和稳定溶质在单/双域传导模型数值实验数据解译确认。应用在两个总体认识上:(1) 原结果在观测单域内的认识是以更牢靠的统计数据为基数,(2) 主成分分析的应用定量统计了在连通指标和流量及传导特性之间的相互关系。ResumoEm aquíferos porosos, o fluxo de água subterrânea e o transporte de solutos dependem fortemente da distribuição das fácies sedimentares à escala fina, que determina a heterogeneidade do campo de condutividades; em particular, os sedimentos permeáveis interconetados que podem formar caminhos de fluxo preferenciais. Por essa razão, é de esperar que certas estatísticas, definidas de forma adequada, tais como a conetividade total e intrínseca das fácies, se correlacionem com as caraterísticas de transporte. A fim de melhorar a avaliação da importância desta correlação, efetuaram-se alguns testes em dois conjuntos de realizações equiprováveis, obtidos com dois métodos geoestatísticos de simulação diferentes—simulação sequencial de indicadores e simulação por múltiplos pontos (MPS)—a partir do mesmo conjunto de dados, referente a um análogo de um aquífero de sedimentos depositados numa sequência fluvial de meandro/canal. Os dois conjuntos apresentam caraterísticas diferentes; as simulações com MPS são mais estruturadas e caraterizam-se por caminhos de fluxo preferenciais. Este facto é confirmado pela análise de conetividades de transporte e pela interpretação de dados de experiências numéricas de transporte de solutos conservativos com modelos de domínio único e duplo. O uso de dois conjuntos permite (1) que os resultados anteriores obtidos por realizações únicas possam ser consolidados numa base estatística mais firme e (2) a aplicação da análise de componentes principais para avaliar quais as quantidades estatisticamente mais relevantes para a relação entre os indicadores de conetividade e as propriedades de fluxo e transporte.

Validation of Hurst statistics: a predictive tool to discriminate turbiditic sub-environments in a confined basin

ABSTRACT Turbidite sequences within confined basins constitute important hydrocarbon reservoirs world-wide and, for this reason, the discrimination of sedimentary sub-environments based on an objective statistical method is of interest for pure and applied science. We investigated the potential use of the Hurst test as a statistical tool to discriminate sub-environments within geologically complex turbiditic units that fill a confined basin with well-exposed facies transitions and onlaps, at the scale of several stacked reservoirs (Cengio and Bric la Croce–Castelnuovo Turbidite Systems in the Tertiary Piedmont Basin, Oligocene, northern Italy). In vertical stratigraphic sections, the Hurst test determines the degree of clustering of low and high values of sedimentological variables, such as bed thickness, grain size and sand/mud ratio, which are dependent on sub-environments of deposition. We applied the Hurst test to depocentral and marginal sub-areas across the basin (parallel and perpendicular to the main palaeocurrent direction), documenting a different clustering of thick and thin beds, and of high and low values of the sand/mud ratio, in the depocentre–distal sector with respect to the onlap areas. A new field (onlap sub-environment) could thus be added to the classification diagram of turbidite settings based on the Hurst index. The Hurst phenomenon (clustering of high and low values of the selected variables) was also able to distinguish between proximal and distal (depocentral) lobe settings, and to recognize the fingerprint of the different depositional lobes (fully confined aggrading, prograding, backstepping). The map of turbidite sub-environments obtained by interpolation of the Hurst index is quite comparable to the field-observed facies map, providing impressive robust validation of the Hurst statistics. This method seems to represent a very promising predictive tool for subsurface studies of turbiditic oil fields based on core and log analyses.

Simulation of Fine-Scale Heterogeneity of Meandering River Aquifer Analogues: Comparing Different Approaches

We compare different approaches to fine scale simulation of aquifer heterogeneity of meandering river depositional elements, based on the study of a 3-D quarry exposure of historical point bar-channel sediments of the Lambro River (Po plain, Northern Italy). The starting point is a sedimentological and hydrostratigraphic hierarchic model obtained after mapping of five quarry faces with centimeter-scale detail. The vertical facies maps show the shape and size of two superimposed composite bars, of their component unit bars and channel fills and the distribution of the individual facies within them. Textural and poro-perm analyses allowed the definition of the properties of four basic hydrofacies (Open Framework Gravels, Gravelly Sands and Sandy Gravels, Clean Sands, Sandy Silts and Clays), with permeability contrasts by at least one order of magnitude \((1{0}^{-9} < \mathrm{K} < 1{0}^{-1})\). The correlation of hydrofacies has been quantified after discretization of the maps with square cells (side 0.05 m), by both transition-probability geostatistics and variographic analysis, to support 3-D pixel-oriented simulation of the volume. We found a high level of correspondence between the semivariogram ranges and the experimental transition probabilities computed on the entire dataset. Several realizations of 3-D conditioned simulations, that honour the vertical facies maps, were computed using Sequential Indicator Simulation (SIS) and T-Progs (transition-probability geostatistics software). Both methods yield more realistic results if the highest rank depositional elements are simulated separately than if the sedimentary volume is simulated on the whole. Image analyses on random sections through selected realizations shows that, in this specific case, SIS yields the most realistic simulations. However, both techniques are not capable of accounting for trends of depositional features that determine a non-stationary behaviour at the facies scale.

From seismic to bed: surface–subsurface correlations within the turbiditic Cellino Formation (central Italy)

The area east of the Gran Sasso Chain in central Italy has been explored in detail because it holds a hydrocarbon field (Cellino Field), located in the Lower Pliocene foredeep turbidites of the Cellino Formation. Correlation has been made between the hydrocarbon-bearing sedimentary bodies and the same stratigraphic intervals cropping out only few kilometres to the west. The area, thus, offers a rare example where comparison can be made between lithofacies – observed in the field, electrofacies – displayed by the electric logs of the wells, and seismofacies – revealed by seismic survey. This surface–subsurface integrated study of the Cellino Formation has revealed the presence of different turbiditic facies associations, their related electrical expressions and the possibility of a seismostratigraphic subdivision of the unit. These correlations exemplify the different resolution of these three complementary methods of investigation.

Models for guiding and ranking well-to-well correlations of channel bodies in fluvial reservoirs

A probabilistic method has been devised to assess the geologic realism of subsurface well-to-well correlations that entail the lateral tracing of geologic bodies across well arrays with constant spacing. Models of geo-body correlability (based on the ratio between correlatable and penetrated geo-bodies) are obtained from total probabilities of penetration and correlation, which are themselves dependent on the distribution of lateral extent of the geo-body type. Employing outcrop-analog data to constrain the width distribution of the geo-bodies, it is possible to generate a model that describes realistic well-to-well correlation patterns for given types of depositional systems. This type of correlability model can be applied for checking the quality of correlation-based subsurface interpretations by assessing their geologic realism as compared with one or more suitable outcrop analogs. The approach is illustrated by generating total-probability curves that refer to fluvial channel complexes and that are categorized on the basis of outcrop-analog classifications (e.g., braided system, system with 20% net-to-gross), employing information from a large fluvial geo-body database, Fluvial Architecture Knowledge Transfer System (FAKTS), which stores information relating to fluvial architecture. From these total-probability functions, values can be drawn to adapt the correlability models to any well-array spacing. The method has been specifically applied to rank three published alternative interpretations of a stratigraphic interval of the Travis Peak Formation (Texas), previously interpreted as a braided fluvial depositional system, in terms of realism of correlation patterns as compared to (1) all analogs recorded in FAKTS and considered suitable for large-scale architectural characterization, and (2) a subset of them including only systems interpreted as braided.

Hierarchical simulation of aquifer heterogeneity: implications of different simulation settings on solute-transport modeling

The fine-scale heterogeneity of porous media affects the large-scale transport of solutes and contaminants in groundwater and it can be reproduced by means of several geostatistical simulation tools. However, including the available geological information in these tools is often cumbersome. A hierarchical simulation procedure based on a binary tree is proposed and tested on two real-world blocks of alluvial sediments, of a few cubic meters volume, that represent small-scale aquifer analogs. The procedure is implemented using the sequential indicator simulation, but it is so general that it can be adapted to various geostatistical simulation tools, improving their capability to incorporate geological information, i.e., the sedimentological and architectural characterization of heterogeneity. When compared with a standard sequential indicator approach on bi-dimensional simulations, in terms of proportions and connectivity indicators, the proposed procedure yields reliable results, closer to the reference observations. Different ensembles of three-dimensional simulations based on different hierarchical sequences are used to perform numerical experiments of conservative solute transport and to obtain ensembles of equivalent pore velocity and dispersion coefficient at the scale length of the blocks (meter). Their statistics are used to estimate the impact of the variability of the transport properties of the simulated blocks on contaminant transport modeled on bigger domains (hectometer). This is investigated with a one-dimensional transport modeling based on the Kolmogorov-Dmitriev theory of branching stochastic processes. Applying the proposed approach with diverse binary trees and different simulation settings provides a great flexibility, which is revealed by the differences in the breakthrough curves.RésuméL’hétérogénéité à échelle fine des milieux poreux affecte le transport de solutés et de contaminants à grande échelle dans les eaux souterraines et elle peut être reproduite au moyen de nombreux outils de simulation géostatistique. Cependant, il est souvent difficile d’intégrer l’information géologique disponible avec ces outils. Une procédure de simulation hiérarchique basée sur un arbre binaire est proposée et testée sur deux blocs réels de sédiments alluviaux, d’un volume de quelques mètres cubes, qui représentent des analogues d’aquifère à petite échelle. La procédure est implémentée en utilisant la simulation d’un indicateur séquentiel. Néanmoins, elle est suffisamment générale pour pouvoir être adaptée à de nombreux outils de simulation géostatistique, améliorant ainsi leur facilité à incorporer de l’information géologique, i.e., la caractérisation de l’hétérogénéité en termes sédimentologique et d’architecture. Lorsqu’elle est comparée à une approche d’indicateur séquentiel standard pour des simulations en 2D, la procédure proposée fournit des résultats fiables, plus près des observations de référence, en termes d’indicateurs de proportions et de connectivité. Différents ensembles de simulations 3D, basées sur différentes séquences hiérarchiques, sont utilisées pour réaliser des expériences numériques de transport conservatif de solutés et pour obtenir des ensembles de vitesse de pore équivalente et de coefficient de dispersion à l’échelle de longueur des blocs (mètre). Leurs statistiques sont utilisées pour estimer l’impact de la variabilité des propriétés de transport des blocs simulés sur le transport de contaminants modélisé sur de plus grands domaines (hectomètre). Ceci est investigué avec un modèle de transport 1D basé sur la théorie de Kolmogorov-Dmitriev de processus stochastiques en branches. L’application de l’approche proposée avec différents arbres binaires et différentes configurations de simulation fournit une grande flexibilité, qui est mise en lumière par les différences des courbes de restitution.ResumenLa heterogeneidad a escala fina de loa medios porosos afecta el transporte a gran escala de los solutos y contaminantes en el agua subterránea y puede ser reproducida por medio de varias herramientas de simulación geoestadística. Sin embargo, la inclusión de la información geológica disponible en estas herramientas es a menudo engorrosa. Se propone y se prueba un procedimiento de simulación jerárquica basada en un árbol binario y en dos bloques de sedimentos aluviales de existencia real de un volumen de unos pocos metros cúbicos, que representan una analogía del acuífero en pequeña escala. El procedimiento se implementa utilizando un indicador de la simulación secuencial, pero es tan general que puede ser adaptado a diversas herramientas de simulación geoestadística, mejorando su capacidad para incorporar la información geológica, es decir, la caracterización sedimentológica y arquitectónica de la heterogeneidad. Cuando se los compara con el enfoque de un indicador secuencial estándar en simulaciones bidimensionales, en términos de proporciones e indicadores de conectividad, el procedimiento propuesto produce resultados confiables, más cercanos de las observaciones de referencia. Se usan diferentes conjuntos de simulaciones tridimensionales basadas en distintas secuencias jerárquicas para realizar experimentos numéricos de transporte conservativos de solutos y para obtener conjuntos de velocidad de equivalente poral y coeficientes de dispersión a escala de los bloques (metros). Sus estadísticas se utilizaron para estimar el impacto de la variabilidad de las propiedades de transporte de los bloques simulados sobre el transporte de contaminantes modelados en dominios más grandes (hectómetro). Esto se investigó con una modelización del transporte unidimensional basada en la teoría de Kolmogorov-Dmitriev de los procesos estocásticos ramificados. La aplicación del enfoque propuesto con distintos árboles binarios y diferentes configuraciones de simulación proporciona una gran flexibilidad, que está ilustrada por las diferencias en las curvas de rotura.摘要多孔介质小尺度异质性影响着地下水中溶质和污染物大规模迁移,可通过几个地质统计模拟工具再现此情景。然而,包含现有地质信息的这些工具常常是笨重的。本文提出了基于二元树的分等级模拟程序,并在两个现实生活中几立方的冲积沉积地块中进行了测试,这几立方的冲积沉积地块代表着小尺度的含水层类似物。采用连续指示物模拟完成了模拟过程,但过程非常普通,以至于可以用到各种地质统计模拟工具中,提高综合地质信息的能力,即沉积学和建筑学上的异质性描述。在与二维模拟标准的连续指示物方法相比,在比例和连通性指示物方面,提出的程序可得到可靠的结果,更接近参考观测值。基于不同分等级序列的三维模拟不同的总结果用于进行保守的溶质迁移数值实验,并获取地块标尺长度(米)相等孔隙速度和弥散系数的总结果。其统计结果用于估算模拟地块迁移特性的变化性对较大域(百米)污染物迁移的影响。利用基于分支随机程序Kolmogorov-Dmitriev理论的一维迁移模型对此进行了研究。采用各种各样的二元树和不同的模拟背景应用所提出的方法提供了很大的灵活性,而此灵活性通过突破曲线的差别得到显现。RiassuntoL’eterogeneità dei mezzi porosi a scala fine influenza il trasporto a larga scala di soluti e contaminanti negli acquiferi, e può essere riprodotta tramite diversi metodi di simulazione geostatistica. Tuttavia, non è sempre semplice includere informazioni geologiche in questi metodi di simulazione. Si propone quindi una procedura di simulazione gerarchica basata sul concetto di albero binario, e la si verifica su due blocchi di sedimenti alluvionali aventi un volume di pochi metri cubi e che rappresentano analoghi di acquiferi a piccola scala. La procedura è implementata tramite la simulazione sequenziale con indicatori, ma il principio è generale e può essere adattato ad altri metodi di simulazione geostatistica, migliorandone la capacità di includere informazioni geologiche legate per esempio alla caratterizzazione sedimentologica e architetturale dell’eterogeneità. Confrontata con una procedura di simulazione sequenziale con indicatori standard in termini di proporzioni e di indicatori di connettività, la procedura proposta restituisce risultati affidabili e più vicini alle osservazioni di riferimento. Diversi ensemble di simulazioni tridimensionali, basate su diverse sequenze gerarchiche, sono utilizzati in simulazioni numeriche di trasporto conservativo e per ottenere ensemble di velocità di poro equivalente e di coefficiente di dispersione alla scala dei blocchi (metri). Le loro statistiche sono usate per stimare l’impatto della variabilità delle proprietà di trasporto dei blocchi simulati sul trasporto di inquinanti modellato su domini più grandi (ettometri). Queste stime sono effettuate tramite simulazioni monodimensionali di trasporto basate sulla teoria dei processi stocastici ramificati di Kolmogorov-Dmitriev. Applicare l’approccio proposto utilizzando alberi binari differenti e diverse configurazioni di simulazione risulta in una notevole flessibilità, messa in evidenza dalle differenze osservate nelle curve di restituzione.ResumoA heterogeneidade em pequena escala do meio poroso afeta o transporte de solutos e contaminantes nas águas subterrâneas em grande escala e estes podem ser reproduzidos por diversas ferramentas de simulação geoestatísticas. Entretanto, incluir as informações geológicas disponíveis nestas ferramentas é frequentemente trabalhoso. Um procedimento de simulação hierárquica baseado em uma árvore binaria é proposta e testada em dois blocos de sedimentos aluviais reais com volume de poucos metros cúbicos, que representam aquíferos em pequena escala análogos. O procedimento é implementado usando simulação sequencial indicadora, porém isto é tão genérico que pode ser adaptado para diversas ferramentas geoestatísticas, melhorando a capacidade de incorporar as informações geológicas, por exemplo, a caracterização sedimentológica e arquitetural da heterogeneidade. Quando comparada com uma abordagem tradicional de simulação sequencial indicadora em bidimensionais, em termos de indicadores de proporções e conectividade, o procedimento proposto apresenta resultados confiáveis, próximos as observações de referência. Diferentes conjuntos de simulações tridimensionais baseadas em diferentes sequências hierárquicas são usados para gerar experimentos numéricos de transporte de solutos conservativos e para obter conjuntos de velocidade equivalente em poros e coeficientes de dispersão na escala do comprimento dos blocos (metros). Suas estatísticas são usadas para estimar o impacto da variabilidade das propriedades de transporte dos blocos simulados no trans

Behaviors mapped by new geographies: Ichnonetwork analysis of the Val Dolce Formation (lower Permian; Italy-Austria)

The Pramollo Basin (Italy-Austria) is one of the richest body and trace fossil sites of the Alps, and exhibits a well-preserved Permian–Carboniferous fluvio-deltaic to marginal-marine sedimentary succession. Despite the exceptionally abundant and well-preserved ichnological heritage, the trace fossils of the Pramollo Basin are not well studied, particularly those of Permian units. This study focuses on the ichnofauna of the Val Dolce Formation (Permian; partly Asselian to partly Sakmarian), with the goal of documenting its ichnological heritage and reconstructing its paleoenvironment. These research questions are addressed by applying network theory, an emerging field of complexity science that focuses on web-like systems made of interconnected entities. An ichnological system can be seen as a set of interlinked ichnotaxa, the topology of which depends on the organism-environment interactions. In addition, traditional paleontological and sedimentological observations are used to reconstruct the paleoenvironment. The following ichnotaxa are documented from the Val Dolce Formation: Archaeonassa isp., Curvolithus simplex , Cylindrichnus isp., Helminthoidichnites tenuis , Nereites missouriensis , Planolites isp., Phymatoderma isp., Pramollichnus pastae , Psammichnites plummeri , Taenidium isp., and Zoophycos isp. Network analysis indicates that the Val Dolce ichnological system is structured, with ichnotaxa organized in environment-driven ichnoassociations: Cylindrichnus - Planolites (proximal delta front), Phymatoderma - Zoophycos (prodelta with dysoxic porewaters), Cylindrichnus - Helminthoidichnites - Curvolithus - Zoophycos (distal delta front–proximal prodelta), and Helminthoidichnites - Taenidium - Curvolithus - Nereites - Zoophycos (prodelta). Furthermore, the delta front–prodelta gradient is accompanied by increasing bioturbation intensity and diversity, reflecting the decreasing intensity of major environmental stressors (hydrodynamics, freshwater input, turbidity). Centrality measures of network analysis allow the topological position of traces to be discerned within the studied system, detecting the paleoenvironmental resolution of individual ichnotaxa. As intersections of sets can be described by networks, the studied ichnoassociations can be considered as occupying intersecting behavioral niches. In analogy with the concept of a Hutchinsonian niche, an ichnotaxon’s niche exists in a multidimensional abstract space defined by environmental parameters, which are expressed as spatial variables in the paleolandscape. Consequently, ichnoassociations are not just association patterns, but represent spatial, environmental, and topological entities. This approach allows the reconstitution of spatial relationships between the geographical ranges of ichnotaxa and ichnoassociations, providing information on the physical arrangement of different subenvironments, that is, the structure of the paleoenvironment.