Shallow to deeply penetrating bioturbation by organisms on carbonate shelves can alter the original depositional texture of carbonate sediments, rearrange and modify the primary porosity and permeability patterns, and effectively increase the overall flow properties in multiple intervals. To explore the impact of bioturbation on reservoir quality and its spatial and vertical patterns, this study examined sedimentologically, ichnologically, and geostatistically ubiquitous bioturbated strata throughout outcrops of the Middle Jurassic Tuwaiq Mountain Formation and Upper Jurassic Hanifa Formation in central Saudi Arabia. Each lithofacies within the studied intervals had an ichnofabric index (ii) range from nonbioturbated (ii1) to beds completely homogenized by bioturbation (ii6). Most important was the occurrence of laterally extensive (>5 km) Glossifungites Ichnofacies, which represent firmgrounds with ii2 to ii5. These Glossifungites Ichnofacies are composed of complex and deep, three-dimensional Thalassinoides burrow networks (TBN) in mud-dominated lithofacies. These TBN have pore systems that consist of (1) open and partially open macropores (size of several centimeters), and (2) interparticle and moldic pores within the burrow filling, which consists of peloids, skeletal grains, and coated grains in a grain-dominated packstone texture. The TBN pore system, which typically penetrates the entire extent of the mud-dominated bioturbated beds, provides permeability pathways in an otherwise less permeable medium. Outcrop data and three-dimensional models suggest that these permeable pathways can contribute to overall reservoir flow in three ways: (1) TBN beds contribute to the overall reservoir flow as a single flow unit if bound above and below by impermeable beds (e.g., lateral flow in vertical well). (2) TBN breach the bed boundaries and, thus, connect above and below into more porous, more permeable grainy beds, providing overall reservoir connectivity for the carbonate reservoir and contributing to vertical and lateral flow. (3) TBN beds connect otherwise laterally compartmentalized reservoirs and contribute to vertical flow. Controls on the lateral and vertical variability of the TBN in the study area can be attributed to changes in water chemistry of the depositional environments, which are likely linked to global and local controls. This spatial and temporal relationship impacts the lateral and vertical distribution of flow properties of TBN strata in bioturbated reservoirs. Understanding such relationships is critical for secondary and tertiary recovery of oil by water flooding because such relationships can provide a prediction about the trend of vertical and lateral flow properties.

Abstract Actualistic studies of modern continental environments and the spatial and temporal distribution of terrestrial and aquatic organisms are summarized and synthesized to understand how to better interpret the significance of trace fossils to differentiate lacustrine from fluvial, eolian, and marine deposits in the geologic record. The purpose of this approach is to develop an understanding of the physicochemical factors that control the occurrence, diversity, abundance, and tiering of organism behavior and parallels what is known for benthic and other trace-making organisms in marine environments. The distribution of traces observed in Lake Tanganyika and Lake Eyre, an overfilled lake in a tropical rift basin setting and an underfilled lake in an arid midlatitude ephemeral playa setting, respectively, are described, synthesized, and compared with the Mermia, Coprinisphaera, Termitichnus, Skolithos , and Scoyenia ichnofacies models proposed for continental environments. The comparisons show that all the models are inappropriate for the fluvial-lacustrine settings of Lake Tanganyika and Lake Eyre because the models do not support the environmental uniqueness or distinctive collection of traces across these environments, nor do they provide sufficient interpretive power. The multiple ichnocoenoses for each subenvironment observed in the balanced-filled and underfilled lacustrine systems more accurately record the environmental uniqueness and distinctive collection of traces found in each environment. Ichnocoenoses are better suited for continental depositional systems and their environments because they reflect the nature of processes and distribution of life in continental settings, which are inherently heterogeneous spatially and temporally. Ichnocoenoses also provide sufficient interpretive power for trace-fossil associations formed under different physicochemical conditions for each type of environment. General trends in trace-fossil diversity, abundance, distribution, and tiering are predicted for alluvial (fluvial), lacustrine, and eolian environments so that new models based on the distribution of ichnocoenoses and their sedimentary and pedogenic characteristics from outcrop and core can be constructed.

Abstract The diversity, abundance, distribution, and depth of trace fossils in the Cambrian–Ordovician deposits in Laurentia, from California and Nevada to New York (United States) and Quebec (Canada), are a series of biozones that record the early evolution and radiation of metazoans in shallow-marine environments. The Neoproterozoic–Paleozoic transition (NPT) plays a significant part in understanding the diversity, timing, rate, circumstance of first appearances and subsequent metazoan radiations, and trends in ecospace utilization through the Cambrian–Ordovician as recorded in carbonate and mixed carbonate-siliciclastic deposits. The first burrows with spreiten and complex branching, designated as the Phycodes (Treptichnus) pedum Zone, delineate the base of the Cambrian. This zone overlies the uppermost Neoprotero-zoic Harlaniella podolica Zone and is composed of relatively simple horizontal burrows. The Rusophycus avalonensis Zone, characterized by the occurrence of more complex burrow architectures, overlies the Phycodes (Treptichnus) pedum Zone and represents the last pretrilobite biozone. As recorded by ichnofabric through the Cambrian–Ordovician, trends in the depth and extent of bioturbation illustrate the spatial and temporal change in ecospace utilization. With the onset of the substrate (media) revolution across the NPT, animals adapted, and evolved new innovations to penetrate microbial-mediated sedimentary environments. This change reflects ongoing Cambrian–Ordovician evolution and radiation of metazoans from shallow inner-shelf environments to middle-shelf environments with increasing biogenic reworking through time. Nonetheless, a mixing depth of 6 cm (2.4 in.) was not surpassed until later in the Ordovician. This pattern ismirrored by the first appearances of trace-fossil ichnotaxa in shallow-water environments that later gradually moved offshore to shelf environments. The ichnological patterns are debated, however, asevidence of deep burrowing (i.e.,>6cm[>2.4in.]) has been described from the Cambrian and the Ordovician deposits in the Mackenzie Mountains (western Canada) and the Great Basin (western United States). Evidence for the early evolution of continental ecosystems does not exist in Laurentian deposits until the Late Ordovician, although some evidence for the invasion of land in the Early Cambrian and the Early Ordovician exists.

Abstract The Upper Triassic Chinle Formation of the Colorado Plateau in the western United States was deposited as a continental fluvial-floodplain-lacustrine-eolian depositional system near the west coast of Pangea just north of the paleoequator. The deposystem evolved in response to regional tectonics and long-term climate change. Clastic and volcanic sediment was supplied by uplifted highlands and arc magmatism on the margins of the basin. Climate changed from a Pangean megamonsoon regime in the early Late Triassic to an arid climate setting at the close of the Triassic. Chinle fluvial discharge and sediment load varied through time in response to climate, producing degradational and aggradational cycles. Degradation eroded paleovalleys, and aggradation filled them with both meandering and braided fluvial systems, as well as varying amounts of floodplain mudstones. Paleosols developed on paleovalley fills, interfluves, and floodplain siltstones and mudstones, all of which combine to define several scales of degradational and aggradational cycles. An upward stratigraphic trend in Chinle paleosols from Oxisols and Gleysols, to Alfisols (Argillisols) and Vertisols, culminating in Inceptisols (Prototsols) and Aridisols (Calcisols), supports previous interpretations that climate evolved from monsoonal or humid conditions at the beginning of Chinle deposition to progressively more arid climate conditions at the end of deposition.

Abstract The Upper Triassic Chinle Formation and the Upper Jurassic Morrison Formation preserve a record of lacustrine deposition along the western margin of tropical Pangaea and post-Pangaean North America. The lake deposits in these formations contain archives of sedimentary and geochemical paleoclimatic indicators, paleoeco-logical data, and characteristic stratal architecture that provide glimpses into the evolution of basins linked to global- and continental-scale tectonic events and processes, and the establishment of a mosaic of continental paleoecosystems. This field trip highlights the lacustrine and associated fluvial deposits of the Monitor Butte Member of the Chinle Formation and the Tidwell and Brushy Basin Members of the Morrison Formation in the southern part of the Colorado Plateau region, with emphases on: (1) sedimentary facies analysis and paleogeography of the paleolakes; (2) stratal architecture and high-frequency sequence stratigraphy; (3) recognition of lake basin-fill types; and (4) paleontology and ichnology of lake strata and their paleoecologic, paleohydrological, and paleoclimatic interpretation .

Abstract The type, distribution, and tiering of continental trace fossils (ichnofossils) are useful tools for deciphering continental environments in both outcrop and core. This atlas presents the latest ichnological concepts and provides a comprehensive photocatalogue of nearly the entire suite of major terrestrial and freshwater trace fossils that geoscientists will encounter. The atlas is separated into two sections: 1) concepts and fundamental principles that explain how terrestrial and freshwater trace fossil behavior is interpreted and used to define environments of deposition; and 2) a photocatalogue of outcrop and core examples of continental trace fossils with explanations and idealized line drawings. Section one formulates fundamental concepts of continental ichnology by examining the life cycle of organisms in modern depositional systems. It discusses some of the shortcomings in the current philosophy of ichnology and elaborates on the differences between continental and marine organisms and resultant differences in their traces. The report illustrates how the controls on behavior and distribution of continental organisms can be applied to define continental environments. An ichnological framework for continental systems is presented that is based on analogy to specific environmental controls operating in modern terrestrial and freshwater environments. The framework uses examples of modern and ancient trace fossils to define specific environments. Alluvial, lacustrine, eolian, and transitional depositional settings form potential ichnofacies, which are defined in detail by their ichnologic composition. Section two is a photocatalogue of outcrop and core examples of continental trace fossils. Each type of trace fossil is presented with a description, interpretation of the architecture and surficial burrow morphologies, geologic range, trophic classification, and environmental and climatic settings. The trace fossils are illustrated with idealized line drawings as seen in outcrop and in core. Color photographs are used to show the trace fossils as hand specimens, in outcrop, and core from different geologic formations and ages. Many of the continental traces occur in paleosols where the color differences between the trace fossils and surrounding matrix accentuate the trace fossil’s morphology. The combination of text, line drawings, photographs, and figure explanations allows the user to determine what the trace fossil he or she is working with as well as what the paleoenvironmental and paleoclimatic settings were of the accompanying strata. The last two pages in Section 2 (pages 131–132) are summary sheets of the trace fossil and contain representative color photographs and line drawings of each trace fossil in the photoglossary. It is organized by the orientation of trace fossils in outcrop (or core), and the morphologic complexity of the traces. The summary sheets can also be referred to by the user to key a trace fossil morphology into a particular section in the photoglossary. These sheets also include a list of abbreviations of continental trace fossils to be used when measuring sections in the field or describing core at an offsite location. A separate, laminated reference sheet of these two pages is available from SEPM (Product 55004). The laminated reference sheet allows you to have your guide to continental trace fossils readily available wherever you go.

Abstract Trace fossils are presented alphabetically by the type of organism thought to have constructed the burrow, trail, trackway, or nest. Such trace fossils as adhesive meniscate burrows and U-shaped burrows are listed separately because of their distinct morphologies. Rhizolith and vertebrate traces are also included. Each section has a description; interpretation of the behavior of the tracemaker and significance of the structure(s); its geologic range; trophic classification; and environmental and climatic implications. The traces are illustrated with idealized line drawings as seen in outcrop and in core. Color photographs depict trace fossils in hand specimens, outcrop, and core from different geologic formations and ages. Many of these traces occur in paleosols, where differences in color between the trace fossils and surrounding matrix accentuate the trace fossil’s morphology. This format allows the user to determine what the trace fossil he or she is working with as well as what the paleoenvironmental and paleoclimatic settings were of the accompanying strata. The last two pages in this section (pages 131–132) are summary sheets of the trace fossil and contain representative color photographs and line drawings of each trace fossil in the photoglossary. It is organized by the orientation of trace fossils in outcrop (or core), and the morphologic complexity of the traces. The summary sheets can also be referred to by the user to key a trace fossil morphology into a particular section in the photoglossary. This sheet also includes a list of abbreviations of continental trace fossils to be used when measuring

Abstract Continental Trace Fossils - The type, distribution, and tiering of continental tracefossils (ichnofossils) are useful tools for deciphering continental environments in both outcrop and core. This atlas presents the latest ichnological concepts and provides a comprehensive photocatalogue of nearly the entire suite of major terrestrial and freshwater trace fossils that geoscientists will encounter. The book is separated into two sections: 1) concepts and fundamental principles that explain how terrestrial and freshwater trace fossil behavior is interpreted and used to define environments of deposition; and continental trace fossils with explanations and idealized line drawings. The trace fossils are illustrated with idealized line drawings as seen in outcrop and in core.