Abstract Recent work has focused on erecting new Seilacherian ichnofacies for depositional environments subject to recurring temporal and spatial variations in physico-chemical stress. In marine deltaic settings, these correspond to the Phycosiphon Ichnofacies for mudstone-dominated prodeltaic deposits and the Rosselia Ichnofacies for sandstone-dominated delta-front successions. The archetypal expressions of these ichnofacies, however, are founded on mixed process (wave- and river-influenced) systems, because the juxtaposition of ambient marine conditions during periods of prolonged wave energy with rapid deposition and physico-chemically stressed conditions during heightened fluvial discharge best expresses the deltaic signal. As deltaic settings shift towards end-member processes (e.g. river domination, wave domination and tide domination), or towards mixed-process conditions other than river and wave influence, the resulting ichnological suites and bioturbation fabrics depart from the recently published archetypes. Using selected studies of marine deltaic deposits, predictable departures from the archetypes can be recognized on the basis of these changing processes and their associated physico-chemical stresses. River-dominated delta deposits and tide-dominated delta successions display the greatest deviation from the published archetypes. River-dominated examples show elevated deposition rates, periods of salinity reduction, slumping and dewatering, elevated water turbidity, flood-induced sediment gravity flows and hypopycnal-generated fluid mud. As a result, river-dominated successions are largely devoid of bioturbation. Evidence of marine conditions is commonly restricted to isolated occurrences of dwelling structures such as Arenicolites , Ophiomorpha or Rosselia in sandstone, and Chondrites , Phycosiphon or Zoophycos in mudstone beds, particularly in prodeltaic intervals. Tide-dominated deltaic successions are markedly heterolithic and typified by highly mobile substrates manifested by incrementally migrating asymmetric bedforms and abundant fluid mud. Such settings are also prone to marked changes in salinity and shifts in the position of the turbidity maximum zone. Successions typically show low intensities of bioturbation and sporadically distributed burrows, as well as deposit-feeding structures, deeply penetrating dwelling structures or fugichnia. Many trace fossil suites consist entirely of facies-crossing elements, making assignment to an ichnofacies impossible. Storm flood-dominated deltaic successions are characterized by tempestites that are typically interstratified with river flood-induced sediment-gravity flow deposits and/or mantled by largely unburrowed mudstone drapes derived from hypopycnal plumes associated with river floods. Where these storm flood cycles are interstratified with ambient fairweather beds, assignment to the archetypal deltaic ichnofacies is straightforward. However, as storm beds become increasingly erosionally amalgamated, the preservation potential of the fairweather beds is reduced and the resulting trace fossil suites are biased towards those recording opportunistic colonization of the event beds. The presence of mudstone layers with low bioturbation intensity (BI) containing small numbers of ichnogenera positively correlated with marine conditions (e.g. Chondrites , Phycosiphon and/or Zoophycos ) may be the only evidence that the suites should be assigned to one of the deltaic ichnofacies. Wave-dominated deltas lacking significant storm influence are typically challenging to differentiate from their archetypal strandplain shoreface counterparts and, correspondingly, the resulting trace fossil suites are broadly comparable to the archetypal Cruziana and Skolithos ichnofacies. Most of the preserved record of wave-dominated delta successions is related to fairweather ambient conditions, and so facies typically show high BI values and uniformly distributed bioturbation. Key to recognizing that the suites should be assigned to one of the deltaic ichnofacies is the presence of rare river-generated mudstone and sandstone beds that display evidence of physico-chemical stress and/or the paucity of domichnia typical of suspension-feeding organisms. In most delta types, the prodeltaic facies are most readily discerned to contain trace fossil suites of the Phycosiphon Ichnofacies, owing to the higher preservation potential of all depositional processes, including marine fairweather beds, river-supplied hyperpycnites and other sediment gravity flow deposits, tempestites and fluid mud derived from river flood-related hypopycnal plumes. Assignment of trace fossil suites to the Rosselia Ichnofacies requires some record of the fairweather conditions, which are generally diminished in river-, tide- and storm-dominated successions. The dominance of structures positively correlated to deposit-feeding ethologies at the expense of those attributed to suspension-feeding strategies may point to elevated water turbidity and assignment of the suite to the Rosselia Ichnofacies. However, in many cases, the ichnological suites of delta fronts are so depauperate that assignment to an ichnofacies is problematic and should be avoided.

Abstract: Criteria for recognizing a high-paleolatitude context for sedimentary successions are not widely established. Herein, we provide a facies analysis of the Permian succession of the high-paleolatitude Denison Trough in the southwestern Bowen Basin of Queensland, eastern Australia, and we use this analysis to highlight criteria that may be used to diagnose a high-paleolatitude context in this and other successions. A unified facies scheme for several formations, combining sedimentological and ichnological criteria, recognizes both deltaic and nondeltaic facies within the succession. Whereas a full array of deltaic facies is evident, ranging from distal prodelta to coastal plain, a more limited array of nondeltaic facies is recognized, ranging from shelfal to lower shoreface. The dominance of deltaic facies in the succession suggests that coastlines were overwhelmingly deltaic in aspect. The absence of middle and upper (nondeltaic) shoreface deposits suggests that shallow-water settings were constantly under physico–chemical stresses associated with deltaic efflux, and/or that such deposits were excised by transgressive ravinement following deposition. Deltas were mostly arcuate in planform, consistent with strong wave influence, although some show a more irregular or lobate plan morphology, suggesting significant fluvial influence. Four intervals within the Permian succession (coded P1 to P4) preserve evidence of formation under the direct or indirect (glaciomarine) influence of glacial ice. Palpable evidence of the high-paleolatitude context of the succession is preserved only in these intervals, most commonly in the form of dropstones, glendonite pseudomorphs after ikaite, gravel-grade clasts with modified shapes, and diamictites. In addition to vertical changes into and out of glacial intervals, paleolatitudinal changes in glacially influenced facies are evident across the 25- to 30-degree meridional transect from the Bowen Basin south to the Tasmanian Basin. Outside of glacial intervals P1 to P4, there are few sedimentological or ichnological indicators of high-paleolatitude deposition. Facies characteristics of deposition under glacial influence are therefore crucial to diagnosing the high-paleolatitudinal context of this and other successions.

Abstract The facies characteristics of the shallow marine environment are largely determined by the complex interplay and relative importance of wave energy, tidal flux, storm magnitudes and frequencies, and river-sediment input. Ichnology is a valuable tool in constraining these processes when integrated with sedimentological and stratigraphic analysis. Trace fossils are biogenic sedimentary structures, strongly facies controlled, and generally temporally long ranging, making them ideal for facies analysis. Ichnofossils are also readily observable at outcrop and core scales, making their identification and interpretation as routine as that of primary physical sedimentary structures. The ichnofacies paradigm is exceptionally well poised to offer critical information about the conditions operating during deposition (e.g., softground ichnofacies) or during development of stratigraphic discontinuities (e.g., substrate-controlled ichnofacies and palimpsest softground suites). The ichnofacies concept stands as one of the most elegant but also most widely misunderstood and misused concepts in ichnology. Softground ichnofacies have been refined to include proximal, archetypal, and distal expressions, permitting high-resolution subdivision of depositional environments such as strandline shoreface complexes. Models addressing brackish-water-induced stresses, substrate consistency changes, reduced oxygen levels, and energy variations on bioturbation have enhanced the identification and subdivision of estuarine incised-valley, embayment, and interdistributary-bay deposits. The ichnological characteristics of these brackish-water settings include: (1) suites characterized by reductions in the numbers and diversities of ichnogenera, corresponding to impoverished marine assemblages; (2) traces that are generally diminutive compared to their fully marine counterparts; (3) a predominance of simple opportunistic structures of inferred trophic generalists; (4) suites comprising elements that record variations in substrate consistency and depositional rates; and (5) successions showing locally high degrees of bioturbation, as well as monogeneric trace suites. Ongoing work concentrates on the effects of hypopycnal-induced water turbidity, hyperpycnal discharge, freshets, fluid-mud deposition, heightened depositional rates, and storm events on infaunal behavior, and helps to identify the deltaic ichnological signal, elucidating the relative importance of waves, tides, and fluvial discharge. Generally reduced and sporadically distributed bioturbation intensities, common unburrowed and mud-draped event beds, abrupt juxtaposition of fully marine suites with impoverished suites, predominance of facies-crossing deposit-feeding structures adapted to sandy substrates, and a paucity of dwelling structures attributable to suspension-feeding organisms constitute the recurring ichnological deltaic signal that has been elucidated to date.Ultimately, such models could be applied to along-strike variations in linked depositional systems, enhancing paleogeographicreconstructions.

Abstract The lithological characteristics of wave- and/or storm-dominated delta-front deposits are fundamentally similar to those of facies deposited on the wave-formed shorefaces of strandplain settings. Differentiating ancient shoreface deposits from those that record deposition in proximity to contemporaneous wave-dominated deltas, therefore, is challenging, especially where the facies represent deposits that are intermediate between end-member strandplains and delta fronts. To date, archetypal facies models are inadequate to describe and distinguish between such deposits. The challenge is further accentuated where studies are limited entirely to core and other subsurface data. Depositional processes typical of deltaic settings influence infaunal organisms in subtle but significant ways. The resulting ichnological signatures clearly reflect the innate differences in physicochemical conditions and paleoenvironmental stresses operating in these settings, such as variations in sedimentation rates, substrate consistencies, oxygenation, salinities, energy conditions, increased turbidity levels, and episodic deposition associated with river floods. Lower Permian successions of the Wasp Head, Pebbley Beach, and Snapper Point Formations of the southern Sydney Basin in southeastern Australia are spectacularly exposed in extensive coastal outcrops. The preserved lithologies and many of the primary sedimentary structures are virtually identical to those characteristic of offshore and strandplain shoreface deposits. Integration of the lithological, sedimentological, and subtle ichnological differences, however, demonstrate that these units were deposited under the influence of paleoenvironmental stresses. There is also considerable evidence of very cold climatic conditions and concomitant effects on the depositional environment from ice rafting, which imposed additional paleoenvironmental stresses. For the most part, fair-weather beds closely resemble strandplain shoreface deposits, with trace-fossil suites that are very diverse and contain a mixture of structures that reflect a variety of feeding strategies characteristic of the Cruziana and Skolithos Ichnofacies. Variations in the ichnological signatures, and departures from the archetypal ichnofacies expressions, in the form of sporadic bioturbation levels, reduced assemblage diversities, and reductions in ichnogenera sizes compared to their unstressed counterparts, suggest intermittent physicochemical stresses. Associated storm deposits display many of the sedimentological and ichnological characteristics associated with river influx and deltaic conditions, including: soft-sediment deformation structures and sediment-gravity-flow deposits, recording rapid sediment emplacement; mudstone drapes that are characteristic of hyperpycnally emplaced fluid muds and rapidly flocculated muds that are produced along the zone of mixing at the base of a hypopycnal (buoyant) mud plume; unbioturbated, carbonaceous mudstone interbeds with synaeresis cracks consistent with freshet-induced salinity fluctuations; an abundance of phytodetrital material, and allochthonous wood and large logs; and sandstone beds with “stressed” trace-fossil suites attributable to the Cruziana Ichnofacies, where ordinarily suites representative of the Skolithos Ichnofacies would be expected. These characteristics suggest that fair-weather beds reflect ambient wave shoaling, but during and immediately following storms, increased river discharge strongly influenced the depositional environment and thus the characteristics of the resultant event beds. Overall, the successions are therefore interpreted as wave- and storm-dominated prodelta to proximal delta-front deposits. Variations in storm signature throughout the successions reflect temporal and spatial variations in the preservation and, therefore, abundance of fair-weather beds. Such variations may represent changing storm climates, climatic seasonality, fluctuations in river discharge, increased amalgamation of beds by persistent storm activity, subtle changes in storm tracks with respect to delta-front orientation, and subtle shallowing or deepening along the delta front.

Abstract Trace fossils or ichnofossils are the fossilized tracks, excavations, and domiciles of animals. In general, these are taken to represent the vestiges of animal behavior. As such, trace fossils can be related to animal coping strategies in sedimentary environments. Those strategies can be associated with sedimentary / environmental conditions. Burrows are classified according to their overall morphologies. The morphology of trace fossils is evaluated using the following nomenclature: shafts, tunnels, tubes, lining, infill, meniscae, spreite, and trample. The shape and form of trace fossils is also considered. Behavioral classifications are inferred, and provide a higher level of organization for ichnofossils. Behavioral inferences form the basis for the definition of ichnofacies. Preservation of trace fossils depends on sedimentological and diagenetic factors. The fundamental physical parameters regarding ichnofossil preservation are the net sedimentation rate, the biogenic mixing rate, and the magnitude of physical reworking. Physical parameters relate to the presence or absence of textural contrast. Ichnofossil diagenesis comprises: (1) cementation of a finer-grained burrow wall [preferred tube cementation]; (2) cement precipitation or cement dissolution within a coarser-grained burrow fill [preferred burrow cementation]; (3) cement precipitation or dissolution adjacent to an ichnofossil [fabric-mimicking hypoburrow cementation]; and (4) concretion formation [nodular hypoburrow cementation]. This paper also documents the various animal responses to physical processes, referred to herein as “process ichnology”. Considered are ichnofossils associated with high or sporadically high sedimentation rates, the use of ichnofossils for their potential in revealing the cohesiveness of a substrate at the time of burrowing, trace fossils and burrow linings as sediment traps, and finally, trace fossils as penecontemporaneous strain indicators. Other general applications of ichnology, including ichnofacies, stratigraphic utility, and reservoir analysis, are considered. These reside in a well-established framework and thus serve as a brief summary of previously conducted research.

Abstract The ichnofacies paradigm endures as the elegant, unifying framework within which accurate ichnological observations and their reliable environmental interpretations can be derived from the rock record. These recurring, strongly facies-controlled groupings of trace fossils, reflecting specific combinations of organism behavior (ethology), constitute the benchmark animal-sediment responses to optimum environmental conditions. Seilacherian ichnofacies are therefore distinctive, recurrent, archetypal associations of traces, made most useful when placed into the context of the original suites (i.e. traces that record the activities of coherent, environmentally related infauna). Ichnofacies are part of the total aspect of the rock, and consist of primary features imparted by the organisms inhabiting the depositional environment (biogenic structures). Insights into the depositional environment are derived from the fact that organisms respond in predictable ways to variations in energy conditions, food resource types, substrate consistency, water salinity, oxygenation, subaerial exposure, substrate moisture, temperature and others. Although in the marine realm many of these conditions change progressively with increasing water depth, ichnogenera display, at most, a passive relationship to bathymetry. Additionally, like lithofacies, ichnofacies are subject to Walther's Law. The utility of ichnofacies to paleoenvironmental reconstruction, therefore, also lies in their lateral continuity and predictable vertical succession, leading to mappable constructs. Accurate interpretations of depositional environments favor reliable predictions of laterally adjacent settings and their associated ichnofacies. Like all facies analyses, interpretations of ichnofaunas are improved substantially when they are evaluated in the context of the host rocks and their sedimentologic (i.e., lithofacies) and stratigraphic implications. Archetypal ichnofacies are especially effective for characterizing deep marine through to shallow marine settings, though more recent studies have investigated and expanded their utility in continental regimes as well. Intergradations between the archetypal ichnofacies are also common and demonstrate a continuum of changing depositional conditions. As a result, very high-resolution analyses can be achieved. Departures from the archetypal ichnofacies are common, but their recognition and interpretation are only possible by comparison with these established temporally and globally recurring groupings. By their very nature, such anomalous ichnological suites yield valuable insights into the specific characteristics of the depositional setting, highlighting animal-sediment interactions in response to imposed environmental stresses. In this way, brackish-water environments, anoxic to dysaerobic settings, and areas of fluvio-deltaic deposition can be readily recognized. Thirteen temporally and geographically recurring archetypal ichnofacies that demonstrate temporal and global recurrence have been defined. Most are named for a representative ichnogenus: Scoyenia , Mermia , Coprinisphaera , Trypanites , Entobia , Gnathichnus , Teredolites , Glossifungites , Psilonichnus , Skolithos , Cruziana , Zoophycos , and Nereites . Traces in freshwater (continental) (i.e., Scoyenia , Mermia , Coprinisphaera ), and brackish-water settings are in need of further study. The marine softground ichnofacies (i.e., Psilonichnus, Skolithos, Cruziana, Zoophycos, and Nereites ) are comparatively better understood and constitute robust models. Current research has demonstrated that the marine softground ichnofacies form a continuum along the depositional profile, adding precision to paleoenvironmental interpretations. Traces in the firmground ( Glossifungites ), woodground ( Teredolites ), and hardground ( Trypanites , Entobia , and Gnathichnus ) ichnofacies are principally distributed on the basis of substrate type and consistency. Ongoing research of these substrate-controlled ichnofacies continues to highlight subtle, previously overlooked complexities, expanding their utility in the rock record.

Abstract Many depositional settings are characterized by temporally and spatially variable physico-chemical stresses, leading to trace fossil suites that depart from those attributable to the archetypal ichnofacies. These departures impart critical information about the depositional setting that could not be derived using physical sedimentology alone. Organisms are sensitive to subtle changes in the environment and hence, are particularly adept at highlighting a range of physico-chemical stresses. Recurring departures from the archetypal ichnofacies have been identified from numerous depositional settings, including estuarine incised valleys, open bays and lagoons, storm-dominated shorelines, deltaic complexes, stagnant or stratified water bodies, and oxygen-depleted shelves and slopes. Settings prone to physiological stress are characterized by ichnological suites that are dominated by facies-crossing elements showing high degrees of infaunal opportunism. Suites display general reductions in diversity and commonly, by decreases in the range of ethological groupings. Stressed settings, as well, generally result in a greater proportion of simple structures generated by inferred trophic generalists. Environmental stresses occur along a continuum from toxic to ambient, and hence, familiarity with unstressed suites is essential to recognizing their presence and magnitude in the rock record. The most common ichnologically delineated environmental stresses are salinity reductions, increased depositional rates, episodic deposition, heightened water turbidity, and reduced oxygenation. The fundamental characteristics of the brackish-water ichnological model are 1) suites characterized by reductions in the numbers and diversities of ichnogenera, corresponding to an impoverished marine suite; 2) traces that are generally diminutive compared to their fully marine counterparts; 3) a predominance of simple opportunistic structures of inferred trophic generalists; 4) Suites comprising elements that record variations in substrate consistency and depositional rates and 5) successions showing locally high degrees of bioturbation, though locally with monogeneric suites. Rapid deposition rates are reflected by 1) overall decreases in bioturbation intensity and 2) a paucity of elaborate, specialized-feeding structures, in favor of more mobile or temporary (sessile) deposit-feeding structures. Dwellings that facilitate readjustment or re- equilibration are locally common. Where settings record sporadic deposition, partitioning of fair-weather infaunal communities and post-event communities are apparent. Turbidites and tempestites, in particular, show juxtaposition of substrate types in much of the shallow marine realm. Successions record partial to complete extermination of fair-weather communities, organism escape through the event bed, initial recolonization of the new substrate and (depending upon the magnitude of environmental contrast between the ambient and event bed conditions) a replacement of the event suite with the fair-weather suite. Juxtaposed suites may range from Skolithos Ichnofacies elements juxtaposed with Nereites Ichnofacies elements (e.g., deep-sea turbidites), to suites attributable to the Skolithos Ichnofacies juxtaposed against other suites of the Skolithos Ichnofacies (e.g., lower and middle shoreface settings). In all cases, the alternation of such suites record in loco changes in energy and depositional rates. Mud turbidites, contourites, phytodetrital pulses, and freshet-induced, hyperpycnal flood deposits are common to river- and/or tide-dominated deltaic lobes, tidal shelves, continental slopes, and more rarely, large restricted bays or central basins adjacent to bay-head deltas in estuarine incised valleys, but are less well-studied. The depositional positions of these event beds, their substrate types, and the nature of food resources contained therein yield markedly different organism responses. Biogenic structures tend to be overwhelmingly those of facies-crossing deposit-feeders, locomotion and resting structures, or deep-tier structures that exploit these anomalous layers after burial. Increased water turbidity is commonly associated with persistent, suspended sediment-laden distributary discharge on deltas and brackish-water bays, or mixing at the turbidity maximum zone of tidal-fluvial channels. Ichnological suites are characterized by reduced bioturbation intensities, reduced ichnogenera assemblage diversities, and the limitation of ethological categories to those of locomotion, resting, deposit-feeding, and grazing behaviors. Turbid water reduces primary productivity, clogs the feeding apparatus of endobenthic filter feeders, and increases the clastic content to be processed by suspension feeders and some carnivores. Consequently, highly turbid settings display a pronounced impoverishment of ichnogenera normally attributed to the Skolithos Ichnofacies, and consist, instead, of facies-crossing elements attributable to the Cruziana Ichnofacies. Settings characterized by fluid muds include estuarine channel systems prone to development of a turbidity maximum zone, or to delta distributaries and delta front complexes, particularly in river- and tide-dominated systems. Initial deposition of the flocculated clay yields soupground conditions. Ichnological characteristics include surface pascichnia, indistinct mottling, and rare, open, mucous-lined tubes that collapse readily during compaction. Few of these structures are likely to survive into the rock record, Biogenic structures generated after compaction are more commonly preserved, and include surface trails and resting structures, intrastratal deposit-feeding structures, and deep-tier dwelling and/or deposit-feeding structures from higher levels. Reduced oxygenation models yield oxygen-restricted ichnocoenoses (ORI). Reduced oxygen settings range from the deep sea, slope, and shelf, as well as stratified lagoons, bays, estuaries, and abandoned tidal and distributary channels. Ichnological responses to dysoxic to anoxic conditions are reflected by 1) reductions in ichnogenera diversities; 2) reduced trace fossil abundances; 3) decreasing burrow diameters; and 4) decreasing depth of burrow penetration into the substrate. Ethological distributions or discrete ichnogenera linked to reduced oxygen conditions remain the subject of some debate.

Abstract Trace fossils and trace fossil suites can be employed to aid in the recognition of various discontinuity types and to assist in their genetic interpretation. Ichnology can be employed to resolve surfaces of stratigraphic significance in two main ways: 1) through the recognition of discontinuities using omission suites reflecting palimpsest softground ichnofacies and substrate-controlled ichnofacies (i.e., Glossifungites , Trypanites , and Teredolites ichnofacies), and 2) through careful analysis of vertical softground (penecontemporaneous) ichnologic successions (analogous to facies successions). Integrating the data derived from omission suites with paleoecological data from vertically and laterally juxtaposed softground ichnological suites greatly enhances the recognition and interpretation of a wide variety of stratigraphically significant surfaces. This, coupled with conventional sedimentary facies analysis and sequence stratigraphy, constitutes a powerful approach to the interpretation of the rock record. Continued analysis of the utility of omission suites has shown that autocyclically generated breaks are common to the terrestrial realm, inshore, intertidal settings, and to some slope settings. Autocyclicity is less of an issue in shelf and shallow marine settings, where erosion of the substrate is typically associated with deposition, closing the colonization window. In the case of cohesive substrates, autocyclic breaks are associated with less indurated “stiffgrounds” that demonstrate smaller, less penetrative and commonly somewhat compacted structures compared to true firmground counterparts that characterize allocyclic discontinuities. Allocyclic discontinuities vary in character spatially, depending upon the lithologic character of the exhumed substrate, the degree of coherence of the exhumed substrate, the energy regime at the time of colonization, and the paleoenvironment that prevailed during colonization. Modern and ancient studies demonstrate that a single discontinuity may host omission suites that span the entire range from palimpsest softground, through firmground, woodground to hardground. Further, within the firmground suites, recurring proximal to distal variability has been documented, recording depositional conditions that prevailed during colonization. Proximal expressions tend to be characterized by vertical structures of inferred suspension-feeding and passive-carnivore infauna. Distal expressions, in contrast, are wholly dominated by the horizontal dwellings of inferred deposit feeders. Surfaces of sequence stratigraphic importance such as regressive surfaces of erosion (RSE) and subaqueous extensions of sequence boundaries (SB) locally host omission suites. In particular, the bases of forced regressive and lowstand shorefaces and deltas may contain palimpsest softground and firmground trace suites. Such deposits pass seaward into correlative conformities (CC) that lack omission suites, though the preservation potential of the CC is exceedingly low in forced regressive settings. Transgressive surfaces widely host omission suites, particularly where they are erosional, or where they onlap earlier sequence boundaries. Non-erosional transgressive surfaces include marine flooding surfaces (MFS) and bay-margin flooding surfaces (BFS). In shelf and offshore settings, MFS dominate and commonly demarcate parasequences boundaries, and are locally associated oxygen-restricted ichnocoenoses (ORI) and condensed sections. Sediment starvation coupled with oceanic bottom currents, which may prevail on slope environments, may lead to firmground and stiffground omission surfaces that correlate with the MFS. In the inshore settings, embayment and estuarine incised valleys may contain BFS within their successions that correlate with MFS seaward. In shallower or higher-energy positions, the BFS may onlap an older sequence boundary during coastal retreat, and permit omission suite development. Higher energy conditions lead to wave or tidal-scour ravinement, which exhumes older deposits and/or incises through or modifies earlier discontinuities. This is particularly common in the coastal-margin realm, where transgressive surfaces of erosion (TSE) cut through older sequence boundaries (FS/SB). Coastal embayments, and estuarine incised valleys are particularly prone to such amalgamation of discontinuities. Continued transgression results in flooding over embayment and valley margins and transgressive ravinement of the interfluve areas. If transgression is incremental or shows pauses in the rate of deepening, short-lived periods of shoreline progradation can occur over the transgressive surface. This results in a distinctive transgressive facies relationship. In distal positions, the discontinuity is overlain by offshore to shelf deposits that accumulated below fair-weather wave base, but overlie an erosional discontinuity that was cut above fair-weather wave base. Firmground omission suites associated with the discontinuity highlight its erosional character and permit its differentiation from the correlative conformity of the lowstand shoreface. Resumed transgression may lead to the development of condensed section accumulation and associated ORI. These relationships demonstrate that the integration of ichnology with facies analysis and sequence stratigraphy is essential for high-resolution reconstructions of paleogeography, paleoenvironment, and depositional architecture.

Abstract Biogenically modified sedimentary flow media can occur as well-defined, highly contrasting permeability fields (i.e., dual-permeability networks), or slightly contrasting permeability fields (i.e., dual-porosity networks). Dual porosity reduces the resource quality of a sedimentary rock, in that although the entire rock contributes to fluid flow, the presence of more than one fluid phase can induce preferential flow along tortuous permeability pathways. Additionally, fluid moves via diffusion and advection, making the pathways difficult to model. Dual-permeability flow media have even poorer resource characteristics because the higher permeability portions of the rock provide the only transmissive conduits, and fluid resources may be absent in the tighter (unburrowed) rock. Secondary recovery attempts in dual permeability media can isolate large parts of the active flow network, which may contain resource fluids or gasses. The presence of a dual porosity versus a dual permeability network, and the stratigraphic configuration of burrow-enhanced permeability are the primary considerations when classifying the type of biogenic flow media encountered. These parameters define the five flow-media types: 1) surface-constrained textural heterogeneities; 2) non-constrained, discretely packaged textural heterogeneities; 3) selectively sorted, weakly defined textural heterogeneities; 4) cryptically bioturbated sandstone; and 5) diagenetic heterogeneities. Other factors that influence the quality and behavior of the flow media are burrow density, burrow connectivity and burrow/matrix permeability contrast, burrow surface area, and burrow architecture. With respect to permeability fabrics, 3-D imaging techniques are an essential component of burrow-fabric analysis. Computer Tomography (CT) scans, Micro-CTscans, and MRI techniques have the most potential in burrow-reservoir analysis. These techniques can be used collaboratively to fully assess the nature of burrow-modified flow media.

Abstract Ichnology has proven to be one of the most useful criteria for the recognition of brackish-water deposits in the Phanerozoic sedimentary record. The study of modern brackish settings has demonstrated organized patterns of physical sedimentary processes and faunal distributions. Through comparison with modern systems, it is possible to work out the spatial relations of ancient marginal marine deposits with increased precision. Within the Lower Cretaceous McMurray Formation of northeast Alberta, deposits with inclined heterolithic stratification (IHS) have come to be interpreted as the accretionary bank deposits of estuarine channels. While ichnologically and sedimentologically diverse, many of these IHS packages exhibit characteristics that are consistent with longitudinal variations in a river-fed, channelized estuary. Within such a scheme, sediment character exhibits a tripartite distribution. Towards the fluvial end of the system, poorly sorted sands with decimeter-scale cross-stratification dominate. Bioturbation is exceedingly rare and is restricted to sporadic tidally influenced fine-grained beds. The central zone is characterized by clay- and silt-rich deposits, with mudstone beds grading seaward from finely interlaminated to structureless in character. The marine end of the channelized system is dominated by well-sorted, ripple cross-laminated, very fine-grained sand, displaying comparatively abundant and diverse bioturbation within both the sand and mudstone beds. The combination of physical sedimentology and ichnology also provides insight into the processes responsible for the heterolithic character of the IHS, as well as the temporal scale upon which they operated. The observed features can be accounted for through seasonal variations in fluvial discharge, and resulting changes in water circulation and sedimentation patterns within the estuary. An understanding of the primary depositional relationships of IHS deposits should facilitate the refinement of the stratigraphic architecture within the McMurray Formation, and add to the efficiency of bitumen exploration.

Abstract The Lower Permian Rio Bonito and Palermo Formations represent part of the infill of the Paraná Basin, southern Brazil. Integrated analysis of cores, outcrops and well logs from coal fields in Rio Grande do Sul allows sedimentologic, ichnologic, and sequence-stratigraphic characterization of these successions. The Río Bonito Formation has been typically interpreted as fluvio-deltaic. However, the transgressive nature of the succession, the vertical increase in ichnodiversity and bioturbation intensity, and the vertical passage from brackish-water ichnofaunas to fully marine assemblages argue against a prograding delta and suggest deposition in fluvio-estuarine settings. The lowstand fluvial deposits are unbioturbated. Estuarine deposits of the transgressive systems tract comprise tidal channel, point bar, coal-bearing marsh, and estuary mouth deposits. Estuarine ichnofaunas are characterized by simple tiering structures, low degrees of bioturbation, low diversity, and dominance of simple burrows produced by inferred trophic generalists. The top of the Rio Bonito Formation is represented by a shoreface unit consisting of high-energy, storm-dominated, lower to middle shoreface sandstones, laterally grading into moderate-energy shoreface deposits. High-energy shoreface deposits typically lack bioturbation, but deep burrows may be present locally. Moderate-energy shoreface deposits show alternations of opportunistic and climax suites. The transitional interval between the Rio Bonito and Palermo formations displays features indicative of deposition in a restricted, brackish-water lagoon. The Palermo Formation mostly represents transgressive deposition in open marine environments. A wave ravinement surface separates the underlying marginal-marine deposits from the overlying open marine interval. Open marine strata form regional parasequences. Offshore transition to upper and lower offshore deposits are punctuated by transgressive surfaces of erosion, demarcated by suites attributable to the Glossifungites Ichnofacies. Upper offshore to offshore-transition softground trace fossil assemblages are the most diverse. Degrees of bioturbation are high and tiering structures are relatively complex. Lower offshore deposits are highly variable in their degrees of bioturbation. Shelf deposits are unbioturbated, probably reflecting oxygen-depleted conditions, and delineate maximum flooding of the basin. Comparison with other ichnofaunas suggests that Permian brackish-water assemblages are more similar to Mesozoic ichnofaunas than to earlier Paleozoic ones. However, Permian brackish-water deposits are less pervasively bioturbated and contain less diverse trace fossil suites than their Cretaceous equivalents.

Abstract The early Late Permian Freitag Formation comprises mudrocks, sandstones and thin conglomerates of shallow marine to coastal plain origin, formed along the western margin of the Bowen Basin, Queensland, Australia. The unit is up to 166 m thick in this area, thinning eastward (distally) and southward (laterally) into offshore deposits. The Freitag Formation is considered to be prospective for gas in the northern Denison Trough on the basis of several discoveries in channelized sandstone bodies, the origins and stratigraphic context of which are complex and not fully understood. A re-evaluation of the Freitag Formation, using outcrops, core data, and wireline logs has been completed, and the succession has been subdivided into four unconformity-bounded sequences. The unit, as a whole, can be described as a progradational-retrogradational sequence set, recording a long-term (∼1.5 m.y.) cycle of relative sea-level fall and rise, with shorter-term (?400 k.y.) cycles superimposed on this trend. Depositional facies include non-deltaic, nearshore marine deposits, subaqueous deltaic deposits, and coastal embayment/lagoon deposits. Distinction between these variants is based principally on ichnological criteria. Ichnological signatures throughout much of the formation and in most parts of the study area reflect the overall deltaic aspect of the succession. Key surfaces commonly contain palimpsest trace fossil suites, including many that clearly represent the Glossifungites Ichnofacies. The complex internal architecture is interpreted to be the result of repeated cycles of 10's of meters amplitude relative sea-level fluctuation, possibly related to ice volume fluctuations at the close of the late Paleozoic Gondwanan Ice Age. This revised model for the Freitag Formation suggests that there is an unaddressed potential for gas discoveries in channel sandstones at various levels within the formation.

Abstract Detailed logging of ichnological variations within parasequences of several Cretaceous (Upper Turonian) delta complexes from Wyoming and Utah are correlated with inferred short and long-term changes in depositional processes. These changes reflect various proportions of river, flood, wave, storm, and tide influences. Event beds, such as storm and river-flood deposits, tend to show low BI (Bioturbation Index) values of 0-2, owing to high accumulation rates, although this also depends on event frequencies. Upper surfaces of individual storm/river-flood beds may show BI values of 4-5, reflecting the transition to longer-lived fair-weather conditions. Fair-weather waves facilitate persistent agitation near the bed, buffering environmental stresses. Therefore, wave-dominated deposits that are not affected by storms yield climax communities with robust and diverse ichnofacies signatures reflecting “uniform and high” BI trend with values that average 4. River-dominated intervals show the least uniform trends of BI, because of the highly variable conditions related to river jet and plume behavior. BI values vary from 0 to 4, with generally low ichnogenera diversities. These alternations likely record seasonal to centennial fluctuations in sedimentation rate (river discharge) and water turbidity, which influences substrate conditions near distributary mouths. Tide-dominated intervals tend to show the most ‘stressed’ conditions, reflecting “non-uniform and low” trend of BI, with values of 0-2. These reflect salinity fluctuations, heightened water turbidity, rapidly shifting substrates, and narrow colonization windows associated with daily and monthly changes in tidal periodicity. Individual parasequences are characterized by either upward-increasing and upward-decreasing trends of BI, indicating protection from storm erosion and proximity to river input, respectively. Ichnological signatures change significantly across initial flooding surface, principally showing a marked increase in BI as delta lobes are quickly abandoned and transgressed. In contrast, across the maximum flooding surface, changes in ichnological signatures are subtle and rather uniform. We suggest that different parts of a single delta may experience marked differences in river, wave, and tide influence over time, reflecting the enormous complexity of operative processes at various temporal and spatial scales. Detailed intra-parasequence, bed-scale analyses of trace fossils help to reveal this complex evolutionary history of a single delta.

Abstract Analyses of a number of Cretaceous intervals of the Western Interior Seaway of Alberta have led to ichnological and sedimentological criteria aiding in the identification and differentiation of river-dominated delta, wave-dominated delta, and non-deltaic shoreface successions. Dunvegan Allomember E constitutes a markedly river-dominated deltaic lobe in west-central Alberta, whereas Dunvegan Allomember D constitutes a strongly wave-dominated delta system. The Viking Formation, in contrast, displays characteristics typical of non-deltaic strandplain shoreface successions. Comparison of the sedimentary successions from these two stratigraphic units is valuable in establishing their unique ichnological characteristics. The principal differences lie in prodelta and lower delta-front deposits, and their analogous offshore and shoreface counterparts. Prodelta mudstones of river-dominated delta successions are largely devoid of burrowing, and contain low numbers of deposit-feeding and grazing structures that record low abundance and low diversity expressions of the Cruziana Ichnofacies. Current-generated structures, syndepositional deformational structures, and synaeresis cracks are abundant. Many intervals include beds of structureless mudstone, reflecting abundant deposition of fluid mud and development of soupground conditions. In contrast, wave-dominated systems yield prodelta mudstones with higher diversity, but low abundance expressions of the Cruziana Ichnofacies. Facies-crossing structures of trophic generalists and opportunists dominate the ichnological suites. Hummocky cross-stratification and storm-induced oscillation ripple laminated tempestites are abundant, though soft-sediment deformational structures and synaeresis cracks are commonly intercalated. Offshore units associated with non-deltaic shoreface intervals are typically intensely bioturbated and contain diverse, archetypal to distal expressions of the Cruziana Ichnofacies or more rarely, the Zoophycos Ichnofacies. Intervals display a close affinity with prodelta units of wave-dominated deltas and although there are subtle differences, discrimination can be difficult. Non-deltaic offshore deposits grade along-strike into wave-dominated prodelta units. The reduced numbers of burrows in prodelta mudstones correspond to significantly higher sedimentation rates and heightened physico-chemical stresses, compared to non-deltaic offshore deposits. Sediment-gravity deposits are restricted to the deltaic intervals exposed to hyperpycnal flows. Synaeresis cracks associated with these mass-flow deposits record freshet emplacement, and commonly accompany mud turbidites. The presence of structureless unburrowed mudstones, consistent with deposition of fluid muds and development of soupground conditions, are atypical of offshore settings but common to prodeltaic areas. Their recurring presence is diagnostic of deltaic influence. River-dominated delta-front deposits are largely characterized by structureless silty sandstones and sandstones with zones of intense synsedimentary deformation. Numerous intervals are devoid of bioturbation. Ichnological suites are typified by very low numbers of deposit-feeding and grazing structures with exceedingly rare suspension-feeding structures. Diversities are very low, reflecting a highly impoverished but proximal expression of the Cruziana Ichnofacies. Wave-dominated delta-front deposits, in contrast, mainly consist of stacked, hummocky and swaley cross-stratified tempestites, interbedded with oscillation-rippled sandstones and draped by largely unburrowed, black fissile mudstones. These tempestite-dominated intervals are commonly capped by trough cross-stratified, current rippled and low angle planar cross-stratified proximal delta-front deposits. Soft-sediment deformation features and structureless beds are less common than in river-dominated counterparts. Facies show low intensities of bioturbation, though diversities are moderately high. Suites are dominated by deposit-feeding structures, reflecting a proximal expression of the Cruziana Ichnofacies alternating with event beds low numbers of opportunistic (facies crossing) elements of the Skolithos Ichnofacies. The delta-front deposits contrast markedly with facies of non-deltaic shorefaces, which typically possess large numbers and diversities of both deposit-feeding and suspension-feeding structures, accompanied by lesser grazing structures. Intervals comprise a transition from proximal expressions of the Cruziana Ichnofacies (lower shoreface) to the archetypal Skolithos Ichnofacies (middle to upper shoreface). With increased storm reworking, differences between shoreface and delta-front deposits are obscured. This is due to erosion of the fairweather beds and/or reduction of the colonization window. Delta-front deposits lack abundant suspension-feeding structures, probably as a consequence of heightened water turbidity (which interferes with filter feeding apparatuses) and dilution of food resource concentrations with respect to the total sediment volume. Additionally, post-storm mantling of the substrate with carbonaceous muds shields the event beds from infauna, and depletes bottom-water O 2 values during oxidation of the organic debris. Fluid muds mantle sandy substrates and yield soupground conditions. The combination of these unique ichnological and physical characteristics may be sufficient, in many cases, to differentiate deltaic successions from non-deltaic shoreface systems with relatively few cored intervals.

Abstract The early to mid-Campanian Basal Belly River Formation in the Ferrybank, Keystone, and eastern Pembina fields of central Alberta, reflects a mixed wave- and river-influenced deltaic succession with strong storm overprinting. Prodelta deposits consist of mud-dominated heterolithic successions, characterized by a low abundance yet moderately diverse trace fossil assemblage attributable to a “stressed” expression of the Cruziana Ichnofacies. Proximal prodelta to distal delta front intervals comprise interbedded sandy siltstones and very fine- to fine-grained sandstones exhibiting convolute bedding and sporadic bioturbation. Trace fossil assemblages range from very low to moderate abundance, and low to moderate diversity; the suites are attributable to a “stressed” expression of the Cruziana Ichnofacies. Distal delta front deposits coarsen upwards into fine- to medium-grained sandstones of the proximal delta front. High-energy conditions, coupled with strong storm influences, resulted in erosional amalgamation of tempestites, and led to sporadic distribution of ichnogenera. Proximal delta front intervals are weakly bioturbated, and trace fossil assemblages are characterized by low abundances and low to moderate diversity. Most forms within the sandstone facies represent the structures of deposit-feeding organisms. Suites reflect a “stressed” infaunal community and contain a mixture of elements characteristic of both the Skolithos and Cruziana ichnofacies. Analysis of more than fifty cored wells has revealed prodelta and delta front deposits that vary markedly along depositional strike. The along-strike variations fit well with the recently proposed asymmetric delta model. The model is based on observations of modern wave-influenced deltas such as the Danube. This study provides an ancient analogue. Continued research will seek to further delineate delta lobe asymmetry and concomitant along-strike facies variations, both attributable to longshore drift and deflection of river-induced stresses downdrift of distributary channel mouths. Organisms are exceedingly sensitive to fluvial influence and this “stress” is reflected in the relatively low diversity and low abundance assemblages that characterize many deltaic successions. Ethological preferences and burrow sizes further reflect the level of “stress” imparted on infaunal organisms within the subaqueous delta environment. Trace fossil suites of river influenced deltaic successions signify a departure from the archetypal ichnofacies characteristic to shoreface successions, and their mapped distributions may serve as a predictive tool for determining distributary channel proximity.

Abstract This study integrates ichnological, sedimentological and stratigraphic analyses of the Lower Cretaceous (Albian) Viking Formation in west-central Alberta, facilitating the recognition of sand- and mud-prone heterolithic central basin deposits in wave-dominated, estuarine incised valley fills. Core descriptions from 110 wells in four fields (26 wells from Crystal, 4 from Cyn-Pem, 50 from Willesden Green, and 30 from Sundance-Edson) comprise the data set. Central basin settings diverge from open marine settings based on conditions of reduced and fluctuating salinity. Indications of brackish-water conditions can be subtle, often leading to the misidentification of central basin deposits as open marine “Regional Viking” parasequences. Ichnology is ideally suited to assist in the identification of such brackish-water deposits. Ichnological suites, bioturbation intensities, and physical sedimentary structures are used to differentiate five recurring brackish-water, central basin facies associations. Although central-basin deposits are not significant hydrocarbon producers, associated sand-prone facies of incised valley-fills are lucrative. Central basins comprise the most volumetrically extensive deposits of the valley fills and, as a result, exploration and early development wells are most likely to intersect these heterolithic successions. Facies Association CB1 is mud-dominated, and contains trace fossil suites indicative of the most marine conditions of all the central basin deposits. Facies of CB1 are interpreted to record deposition in marine-influenced bays of incompletely barred estuaries. Intervals encompass BI 3-5, with abundant Planolites , Teichichnus , Palaeophycus , Chondrites , “Terebellina” ( sensu lato ), and Thalassinoides , and subordinate Ophiomorpha , Helminthopsis , Phycosiphon , Asterosoma , Skolithos , Lockeia , Cylindrichnus , Rhizocorallium , Arenicolites and fugichnia. CB1 bay deposits are particularly common to the Sundance-Edson valley system. Facies Association CB2 is also mud-dominated, but generally lacks those ichnogenera considered to be restricted to fully marine settings (e.g., Phycosiphon , Asterosoma , Rhizocorallium , and Helminthopsis ). Intervals display variable and generally reduced bioturbation intensities (BI 1-4). Suites comprise Planolites , “Terebellina” ( sensu lato ), Teichichnus , and secondary Cylindrichnus , Ophiomorpha , Rosselia , Palaeophycus , Diplocraterion , Arenicolites , Skolithos and fugichnia. Very rare occurrences of Chondrites and Lockeia are locally present. Facies of CB2 reflect accumulation in low-energy, strongly brackish bays of well-barred estuaries, and is common to Willesden Green and some Crystal successions. Facies Association CB3 comprises sand-prone heterolithic successions, deposited along shallow bay margins of well-barred estuaries (where it grades upwards from CB2), and/or adjacent to bay-head deltas. The facies displays BI 0-3, with a low-diversity suite of Planolites , Teichichnus , “Terebellina” ( sensu lato ), Ophiomorpha , diminutive Palaeophycus , and fugichnia. Rarely, Rosselia , Cylindrichnus , Thalassinoides , Diplocraterion , Arenicolites , and Skolithos , and very uncommon occurrences of Chondrites , Rhizocorallium , and Phycosiphon are present. Facies of CB3 are common to the Willesden Green valley and landward portions of the Crystal valley. Facies Association CB4 corresponds to sand-dominated heterolithic intervals. The facies display BI 1-4, with robust ichnogenera and high diversity suites (e.g., Planolites , Teichichnus , fugichnia, Palaeophycus , Ophiomorpha , Thalassinoides , Rosselia , Arenicolites , Cylindrichnus , Diplocraterion , Skolithos , Lockeia , Chondrites , Phycosiphon , Siphonichnus , Taenidium , Asterosoma , and “Terebellina” ( sensu lato ). Facies Association CB4 is interpreted to represent bay-margin positions of incompletely barred estuaries (e.g., the Sundance-Edson valley, where it grades upwards out of Facies CB1), as well as late-stage bay infill associated with the early stages of transgression (e.g., all Viking incised valleys studied). Facies Association CB5 encompasses sandstones deposited along the seaward edges of central basins, adjacent to the estuary mouth (e.g., associated with flood-tidal deltas and storm-washover fans). This facies displays BI 0-3, with a strongly marine-influenced trace fossil suite. Ichnogenera comprise Planolites , Ophiomorpha , Palaeophycus , Skolithos , and fugichnia, with secondary Teichichnus , Diplocraterion , Arenicolites , Rosselia , “Terebellina” ( sensu lato ), Thalassinoides , Chondrites , Phycosiphon , Asterosoma , Bergaueria , and Conichnus . Facies of CB5 are common to Willesden Green and Crystal valley successions. Ongoing research seeks to identify characteristic geophysical well-log signatures for central-basin deposits, in order to enhance recognition of estuarine incised-valley fills. Bay-fill signatures in wave-dominated estuaries are commonly misidentified as open-marine parasequences, as bays are generally characterized by sanding-upward successions. Central basins constitute the most areally extensive subenvironments of wave-dominated estuaries, and their deposits are the most likely to be encountered during drilling. Consequently, reliable identification of central basins could facilitate future discoveries of incised valleys. Estuarine incised valley fills are under-represented in the Viking Formation, given the abundance of forced regressive, lowstand, and transgressively incised shoreline trends that have been identified. Integrating ichnology with sedimentology and stratigraphy will assist in the recognition of incised valley fills in the rock record.

Abstract The Late Albian Viking Formation contains a number of coarsening-upward sediment bodies displaying subtle deltaic character. Deltaic deposition is implied through evidence of high sedimentation rates, variable salinity, riverine influx and stressed ichnological assemblages. The sedimentological and ichnological attributes of these deposits reflect riverine, fair-weather basinal (waves and tides), and storm induced processes. The influences of these processes on Viking Formation deposition are illustrated utilizing examples from two study areas in south-central Alberta. In the Hamilton Lake area, coarsening-upward successions are dominated by wave-formed structures. Subtle evidence of riverine input is present in the form of local synaeresis cracks, soft sediment deformation features, carbonaceous mudstone deposits, and reduced bioturbation intensities. Low diversity and abundance of biogenic structures are observed in prodelta deposits, with the resultant assemblage interpreted to reflect moderately to subtly stressed expressions of the archetypal Cruziana Ichnofacies. The distal delta front is characterized by deposit feeding and grazing traces, with fewer suspension feeding structures. This suite is consistent with a low-diversity, moderately stressed proximal expression of the Cruziana Ichnofacies. Ichnological suites from proximal delta front deposits include elements of both the proximal expression of the Cruziana Ichnofacies and the Skolithos Ichnofacies. This suite is interpreted as a stressed expression of the mixed Skolithos - Cruziana “ichnofacies”. Sedimentological and ichnological characteristics of the Hamilton Lake deposits reflect the dominance of wave-induced processes over the associated riverine influx, and are best described as wave-influenced. Cores from the Wayne-Rosedale to Chain area comprise thick sandstone units dominated by low-angle laminations and lesser wave-formed structures. Significant river-derived influx and high sedimentation rates are indicated by common synaeresis cracks, sideritized intervals, convolute bedding, carbonaceous mudstone deposits, and coal fragments. Distal and proximal prodelta deposits contain subtly to moderately stressed expressions of the archetypal Cruziana Ichnofacies, respectively. The proximal and distal delta front display strongly and moderately stressed proximal expressions of the Cruziana Ichnofacies, respectively. In general, trace fossil suites display low diversities and abundances of traces, and an impoverishment of structures of inferred suspension-feeding organisms. This ichnological assemblage is a result of harsh environmental stresses, such as heightened water turbidity, rapid sediment influx, and high concentrations of suspended sediment. Based on the sedimentary and ichnological observations, deposits of the Wayne-Rosedale to Chain area are interpreted to reflect deposition in a mixed river- and wave-influenced deltaic system. In general, deltaic deposits contain trace fossil assemblages impoverished in structures associated with suspension-feeding behaviors. Comparison of the Hamilton Lake and Wayne-Rosedale-Chain deltaic deposits results in a noticeable paucity of suspension-feeding structures in facies of the Wayne-Rosedale-Chain area. This is a result of the stronger wave action in the Hamilton Lake area, which mitigated the effects of environmental stresses related to riverine discharge and facilitated suspension-feeding behaviors.

Abstract The Upper Cretaceous (Cenomanian) Doe Creek Member, encased in the predominantly marine mudstones of the Kaskapau Formation in northwest Alberta, comprises a series of retrogradationally stacked northeast-southwest trending shoreline deposits. An integrated ichnological and sedimentological analysis of these shorelines reveals a complex depositional relationship between deltaic and open-marine shoreface successions. The shoreline trends in the Doe Creek Member display substantial variability in thickness, sedimentology, and ichnological character along depositional strike stemming from proximity to deltaic point sources. The Doe Creek Member exhibits excellent core control in the subsurface, allowing detailed facies analysis of these multifaceted shoreline deposits. The integration of ichnological and sedimentological analysis yields eleven distinct facies in the Doe Creek Member. The facies represent a variety of depositional environments, including fully marine offshore to shoreface deposits and deltaic deposits (e.g., prodelta, delta front, distributary channels and distributary mouth bars). These facies can be divided into two facies associations, based on recurring vertical successions of regressive delta deposits and open-marine shoreface deposits. The deltaic shorelines consistently develop thicker delta front sandstone packages, fed by associated distributary channels. Penecontemporaneous open marine shoreface sandstones, deposited laterally adjacent to the delta fronts, are typically much thinner and display significantly higher bioturbation intensities, resulting in a lower quality reservoir. This dichotomy of reservoir potential and quality has significant implication for hydrocarbon exploration and exploitation. Unfortunately, the deltaic and open-marine shoreface successions appear almost indistinguishable on gamma-ray well log signatures; this renders well-log cross-sections meaningless in terms of understanding the Doe Creek depositional system. In contrast, detailed core-based cross-sections reveal the complex facies architecture of the coeval deltaic and non-deltaic successions. The facies successions and facies architecture of the ancient shorelines of the Doe Creek Member highlight the inherent complexities induced by deltaic influences on a given coastal environment. Deltaic and open-marine shoreface successions are merely the end-members of a spectrum of coastal regimes in which there exist degrees of deltaic influence. Within each regressive shoreline trend, it can be shown that the degree of deltaic character is determined by the lateral proximity to a riverine point source. Therefore it is possible, based on integrated ichnological and sedimentological facies analysis, to locate riverine point sources on a given shoreline trend in the subsurface, which could provide significant economic returns.