Composite Ichnofabrics Research Articles

Trace-fossil suites and composite ichnofabrics from meandering fluvial systems: The Oligocene Lower Freshwater Molasse of Switzerland

The Oligocene Lower Freshwater Molasse of Switzerland is host to spectacular outcrops of fluvial deposits. In distal areas of the Swiss Molasse Basin, deposits of a north-eastward draining meandering system are exposed. Combined sedimentologic and ichnologic observations in the Chli Sunnhalde and Roggwil quarries allow an improved understanding of animal-substrate interactions in deposits of meandering fluvial systems. Strata include meander-belt sandstone, levee sandstone and mudstone, crevasse-channel and splay sandstone, floodplain mudstone and sandstone, and paleosols. While the meander belt and the more proximal crevasse-channel deposits are typically unbioturbated, the more distal deposits show a clear biogenic overprint, with distal crevasse-channel, crevasse-splay, and floodplain deposits being intensely bioturbated.Simple grazing and locomotion trails (included in the Cochlichnus anguineus-Helminthoidichnites tenuis suite) were formed subaqueously in ponded areas of the floodplain. Meniscate burrows (Taenidium isp. suite) and root trace fossils occur along the margin of these floodplain water-bodies and at the top of crevasse-splay deposits. Some of the floodplain, crevasse-splay, and crevasse-channel deposits are pervasively bioturbated by crayfish burrows (Camborygma litonomos suite). Crevasse-splay deposits locally host escape trace fossils.Where cross-cutting relationships are apparent, a colonization sequence can be established as follows: the Cochlichnus anguineus-Helminthoidichnites tenuis suite is cross-cut by the Taenidium isp. suite, which in turn is cross-cut by the Camborygma litonomos suite and root trace fossils. Composite ichnofabrics are common in these meandering river deposits, recording progressive lowering of the water table in overbank subenvironments. Frequency of depositional events was a first-order control on degree of bioturbation. Position of the water table and degree of substrate consolidation exerted considerable influence over the types of trace fossils produced. Distinct bioturbation phases may result in the formation of different trace-fossil suites - representative of disparate ichnofacies - preserved on a single bedding plane. This study further supports the notion that meandering fluvial systems are characterized by trace-fossil suites belonging to the Scoyenia, Camborygma and/or Mermia ichnofacies.

Upper Cretaceous bottom current deposits, north‐east Greenland

AbstractReported ancient bottom current deposits in deep marine settings are scarce and most of them remain contentious. This study describes sedimentological, ichnological and petrographical characteristics of a drill core that covers ca 10 Myr of Upper Cretaceous stratigraphy at Hold with Hope, north‐east Greenland. The core is divided into four facies associations, which are interpreted to reflect deposition from bottom currents, turbidity flows and hemipelagic settling in slope and/or near slope environments. The evidence for bottom current influence is three‐fold. Firstly, pervasive indications of winnowing such as marine bioclast‐rich lags and outsized clasts on ‘mud on mud’ contacts are suggestive of low‐sediment concentration flows capable of transporting up to pebble‐sized clasts. Common Mn–Fe–Mg rich carbonate matrix cements and various types of hiatal chemogenic lag deposits showing glauconite, apatite and carbonate clasts also point to condensation, prolonged exposure at the sediment–water interface and recurrent phases of sea‐floor erosion. Secondly, such deposits can show indicators for tidal processes such as double mud‐drapes, tangential bottom sets in dune‐scale cross‐bedding and cyclic rhythmites. Thirdly, inverse to normal grading at various scales is common in fully marine, commonly seafloor‐derived sediments. Ichnological data indicate considerable taxonomic variability in the bottom current deposits, but recurrent fabrics are characteristically dominated by morphologically simple burrows such as Thalassinoides and Planolites, with secondary Phycosiphon, Nereites, Zoophycos and/or Chondrites. In general, opportunistic taxa are common whereas mature composite ichnofabrics are rare. The omission surfaces are locally burrowed with stiffground to firmground trace fossil suites. The results contribute to establishing sedimentological, ichnological and mineralogical criteria for recognition of bottom current deposits as well as to the understanding of the Late Cretaceous palaeoenvironmental evolution of the Arctic region.

Image processing techniques to improve characterization of composite ichnofabrics

Image processing techniques, including the Analyze Particles tool offered by Fiji software and the Intensity Profile by ICY (IP-ICY), were applied in core and outcrop examples to improve characterization of autocomposite ichnofabrics. Analyze Particles gives information about particle shape and size in the studied image. This tool was applied to Chondrites assemblages in composite ichnofabrics in view of selected images of modern marine hemipelagic cores from Site U1385 of IODP Expedition 339. Differences in size, relative abundance, density and distribution of Chondrites were interpreted as related to variations within the population of Chondrites tracemakers. Intensity Profile quantifies pixel values of the infilling material of traces, proving helpful to discriminate between specimens, evaluate the horizon of colonization, and approach the penetration depth. Its application to the analysis of Zoophycos improves characterization of composite ichnofabrics from deep-sea pelagic calcilutites of the Petra Tou Romiou section (Eocene Lefkara Formation; southern Cyprus). Some suites of Zoophycos were interpreted as associated with different phases of colonization from several horizons. Moreover, it was possible to discriminate structures pertaining to different specimens, as opposed to those from the same specimen.

Ichnology and depositional environments of the Upper Ordovician Stony Mountain Formation in the Williston Basin, Canada: Refining ichnofacies and ichnofabric models for Epeiric Sea carbonates

Ordovician epeiric sea carbonates in intracratonic basins of Laurentia are enigmatic due to their unique depositional settings and the absence of modern analogs. Integrated ichnologic and sedimentologic analysis of the Upper Ordovician Stony Mountain Formation in the Williston Basin of Canada allows recognition of neritic-marine, nearshore-marine, open-lagoon, restricted-lagoon, peritidal sand-shoal and peritidal-flat subenvironments. The Cruziana ichnofacies occurs in neritic (between fair-weather and storm wave bases) and nearshore (around fair-weather wave base) marine environments. The depauperate Cruziana ichnofacies is present in open- and restricted-lagoon environments, indicating a shift from fully marine to stressed conditions. In the open lagoon, composite ichnofabrics related to omission surfaces illustrate the low rates of background sedimentation interrupted by event deposition and early cementation, illustrating the Glossifungites and Trypanites ichnofacies. The decreased size of discrete burrows in the restricted lagoon is attributed to reduced oxygenation under stagnation rather than hypersalinity. The peritidal complex includes high-energy sand shoals and low-energy tidal flats. Only monospecific colonization took place sporadically in associated subtidal environments within the peritidal complex deposits.

Ichnological and sedimentological features of the Hongguleleng Formation (Devonian–Carboniferous transition) from the western Junggar, NW China

Two sections of the Late Devonian to Early Carboniferous Hongguleleng Formation in the Sha'erbuerti and Xiemisitai mountains of western Junggar, NW China were logged in detail and studied with particular reference to their trace fossil content and sedimentary features. The Hongguleleng Formation is composed essentially of shallow marine deposits formed in a volcanic arc-related setting. It contains trace fossils including indeterminate ellipsoid structures, indeterminate shallow-pit structures, Chondrites intricatus, Chondrites targionii, Chondrites isp., Dolopichnus gulosus,?Multina isp., Nereites missouriensis, Nereites isp., Palaeophycus tubularis, ?Phycosiphon isp., ?Phymatoderma isp., Rhizocorallium commune, Rosselia cf. socialis, Teichichnus rectus, Teichichnus ispp., Thalassinoides isp., and Zoophycos ispp. These ichnofossils and related bioturbation structures constitute five distinct groups of ichnofabrics: Chondrites–?Phymatoderma, Rhizocorallium commune, anemone dwelling/burrowing, Teichichnus, and Zoophycos ichnofabrics, conforming to an upward trend from the Cruziana to Zoophycos ichnofacies. The volcanic arc setting provides a natural laboratory to investigate the colonisation styles of benthic faunas during the Devonian, especially for environments with widespread and relatively frequent depositional events disturbing background deposition. The distal event beds are especially suitable for the distinction of the relationship between background and post-event ichnofaunas. Simple and composite ichnofabrics have been distinguished. The simple ichnofabrics are typified by the indeterminate ellipsoid “ichnofabric” made by sea anemones, representing short colonisation event and in situ death and burial resulted from relatively high sedimentation rates even during the periods between volcanic explosions. The composite ichnofabrics are characterised by the Chondrites–?Phymatoderma, ?Multina–Zoophycos and multi-tier Zoophycos ichnofabrics, representing vertical migration of benthic faunas in pace with either distal event deposition or steadily accreted sea floor. The colonisation window in the arc-related setting is closely related to sedimentation rates and frequency of depositional events, determining the completeness of burrow system structure and maturity of benthic communities.

Digital image treatment applied to ichnological analysis of marine core sediments

Characterization of trace fossils in marine core sediments is, most times, difficult due to the weak differentiation between biogenic structures and the host sediment, especially in pelagic and hemipelagic facies. This problem is accentuated where a high degree of bioturbation is associated with composite ichnofabrics. Simple methods are presented here based on modifications to image features such as contrast, brightness, vibrance, saturation, exposure, lightness, and color balance using the software Adobe Photoshop CS6 (Adobe Systems, San Jose, CA, USA) to enhance visibility and thus allow for a better identification of the trace fossils. Adjustments involving brightness, levels and vibrance generally give better results. This approach was applied to marine cores of pelagic and hemipelagic sediments obtained from the Integrated Ocean Drilling Program Expedition 339, Site U1385. Enhancing the digital images facilitates ichnological analysis through improving the visibility of weakly observed trace fossils, and in some cases revealing traces not detected previously.

Zoophycos composite ichnofabrics and tiers from the Permian neritic facies in South China and south-eastern Australia

Gong, Y.-M., Shi, G.R., Zhang, L.-J. & Weldon, E.A. 2009: Zoophycos composite ichnofabrics and tiers from the Permian neritic facies in South China and south-eastern Australia. Lethaia, Vol. 43, pp. 182–196. Zoophycos composite ichnofabrics (ZCI) comprising two or more suites of the same form of Zoophycos are widespread and densely distributed in Early and Middle Permian (Cisuralian–Guadalupian) neritic limestones (Qixia and Maokou Formations) of palaeotropical origin in the Laibin area, Guangxi, South China. Similar ZCI also occur in neritic greywackes of glaciomarine origin from the Middle Permian (Guadalupian) Westley Park Sandstone Member (Broughton Formation) in the southern Sydney Basin, south-eastern Australia. Zoophycos from both regions consists of planar spreite with major and minor lamellae and a cylindrical tunnel interpreted as a marginal tube and/or axial shaft. The cylindrical tunnel is herein considered to be an essential component of Zoophycos, and thus can be used to define and characterize the morphological variability of Zoophycos. It is suggested that the variation of spreite and major and minor lamellae originated from the different morphologies and migration manners of the cylindrical tunnel. The shallowest, shallow, middle and deepest Zoophycos tiers have been distinguished in ZCI on the basis of cross-cutting relationships, the soft-sediment deformation and the contrast in colour between Zoophycos and its host rock. The multiple tiers may represent the substrate consistency spectrum from a softground through a stiffground to a firmground. The different Zoophycos tiers may have been constructed by tracemakers of either different or the same taxonomic affinities in response to the gradual accretion and lithification of sediment layers on the seafloor. The tracemakers appeared to be very sensitive to neither climate nor lithology. The width of the planar spreiten of Zoophycos decreases slightly with the depth of tiering in ZCI. □Composite ichnofabric, Permian, South China, south-eastern Australia, tier, Zoophycos.

Applications of ichnology in lacustrine sequence stratigraphy: Potential and limitations

In comparison with their marine counterparts, lacustrine ichnofaunas have not been extensively used in sequence stratigraphy. Application of trace fossils in continental sequence stratigraphy cannot be based simply on the extrapolation of marine sequence stratigraphy. Marine substrate-controlled ichnofacies, in particular the firmground Glossifungites ichnofacies, develop in stable and cohesive substrates, reflecting erosive exhumation of the sediment. In contrast, in lacustrine sequences, substrate-controlled ichnofossils only rarely indicate erosional exhumation because they are commonly related to desiccation of water bodies. The tripartite division of overfilled, balanced-fill, and underfilled lakes provides a comprehensive framework to evaluate the potential and limitations of lacustrine ichnofaunas in sequence stratigraphy. Based on a number of case studies spanning the three lake-basin types, a model of trace-fossil distribution in overfilled, balanced-fill, and underfilled basins is proposed. Overfilled lake basins contain well-developed softground trace fossils ( Mermia and Skolithos ichnofacies, and the softground suite of the Scoyenia ichnofacies) that are useful to delineate parasequences and parasequence sets. Fluvial discharge into overfilled lakes usually generates density currents that oxygenate lake bottoms, allowing the establishment of epifaunal and infaunal communities. Additionally, these are freshwater lakes where no stress due to hypersalinity occurs, leading to the development of a relatively diverse benthos. Land–plant derived organic matter is the prime source of nutrients, favoring the development of a deposit-feeding benthic fauna in permanently subaqueous, low-energy zones. Firmground suites are rare because such large lakes usually do not experience desiccation. Abundant firmground trace-fossil suites of the Scoyenia ichnofacies occur in balanced-fill lakes, but softground assemblages are usually depauperate. Lowstand deposits contain abundant and widespread ichnofaunas, commonly meniscate trace fossils and arthropod trackways of the Scoyenia ichnofacies. Lake hydrology is closed during lowstands and salinity usually increases, imposing a stress factor on the lake biota and, therefore, softground ichnofaunas are depauperate. Ichnofaunas from turbidite systems in balanced-fill lakes are less abundant and diverse than those from overfilled lacustrine turbidites. Freshwater conditions are common during transgression, but dysaerobic conditions may prevail, imparting a stress factor on the benthic biota. In hydrologically closed lakes, the Scoyenia ichnofacies is widespread, but the Mermia ichnofacies is commonly absent or impoverished. The Scoyenia ichnofacies is associated with lowstand desiccated substrates in underfilled lakes. The density of arthropod trackways may be high, forming tracked omission surfaces. Some of these omission surfaces may represent sequence boundaries expressed by co-planar surfaces of lowstand and subsequent flooding. Rapid changes in depositional conditions reflecting desiccation during vertical aggradation can lead to the formation of composite ichnofabrics that reflect successive bioturbation events.

An approach to the description and interpretation of ichnofabrics in palaeosols

Abstract Studies on ichnofabrics have focused mainly on marine environments. Attempts to apply the ichnofabric methodology and theoretical framework to continental deposits bearing palaeosols are few and poorly developed. Methodologies analysed in this contribution include the applicability of current ichnofabric indexes and diagrams, the assessment of the destruction of the original bedding by ichnofabrics and by other soil characters separately, and the relationships between different stages of palaeosol and ichnofabric development. Many soil features may be formed without the intervention of bioturbation, or may be the result of interactions of physical, chemical and biological processes, in which traces of organisms may have only a subsidiary role. Ichnofabrics can be well developed in palaeosols devoid of other soil characters and, conversely, palaeosols showing a well-developed soil structure can bear almost no trace fossils. This fact adds a third component to classical methods that normally consider only original bedding and ichnofabrics. Theoretical analysis includes the possibility of recording composite ichnofabrics in palaeosols, and the value of individual ichnotaxa as possible indicators of subaerial conditions and environmental changes. The ecological preferences and requirements of trace-makers provide the key to understanding composite ichnofabrics; however, only complex traces can be certainly attributed to particular modern taxa. Insect nests, pupal chambers and earthworm burrows are the most reliable indicators of subaerial exposure and, in many cases, very particular environmental conditions.

Trace Fossils and Trolls: Report of the First International Ichnofabric Workshop in Norway

Ichnofabric is a relatively new concept in paleontology and sedimentary geology, having been introduced in the literature less than a decade ago. Ichnofabric is an important component of ichnology, as it deals with how organisms affect sediment properties, produce preservable sedimentary structures, and create biogenic sedimentary fabrics. Ichnologic research traditionally has centered on identifiable trace fossils, although the processes of bioturbation and bioerosion are quite important and have received significant attention by some workers. The advent of the ichnofabric concept during the 1980's has added a new dimension to the field of ichnology, because it provides a more comprehensive picture of the original depositional environment by emphasizing biogenic aspects of the fabric of sediments. In September of 1991, a very enthusiastic group of ichnofabric researchers from all over the world gathered in Oslo, Norway, for the First International Ichnofabric Workshop, which was sponsored by Norsk Hydro and several other oil companies that operate in the North Sea region. The meeting was organized by Fredrik Bockelie (Norsk Hydro, Stabekk, Norway) and Tony Ekdale (University of Utah, Salt Lake City). Other participants in the workshop included David Bottjer (University of Southern California, Los Angeles), Richard Bromley (Institute for historisk Geologi, Copenhagen, Denmark), Allen Curran (Smith College, Northampton, Massachusetts), Mary Droser (University of California at Riverside), Christian Gaillard (University Claude Bernard, Lyon, France), Roland Goldring (Sedimentology Institute, Reading, England), Niels-Martin Hanken (University of Tromso, Norway), Chris Maples (Kansas Geological Survey, Lawrence), Tom Mason (University of Natal Durban, South Africa), Molly Miller (Vanderbilt University, Nashville, Tennessee), John Pollard (University of Manchester, England), Charles Savrda (Auburn University, Auburn, Alabama), Ronald Steel (University of Bergen, Norway), Andrew Taylor (University Manchester, England), Guanzhong Wang (Sedimentology Institute, Reading, England), and Andreas Wetzel (University of Basel, Switzerland). The purpose of the workshop was to examine the concept of ichnofabric, to come to a consensus regarding its terminology, and to develop applications of ichnofabric in facies recognition, event correlation, reservoir prediction, sedimentologic modeling, and paleontologic reconstruction. Major themes that were addressed at the conference included the manner in which the tiered structure of infaunal organism communities is reflected in composite ichnofabrics, the application of empirical ichnofabric indices in assessing the degree of bioturbation of sediment packages, the utility of ichnograms in basin wide reconstructions, the recognition and correlation of recurrent ichnofabrics and strata in both the subsurface and outcrop sections, and the potentially widespread use of ichnofabric correlation in petroleum exploration and reservoir prediction. The workshop began in the Vaekero Research Center of Norsk Hydro Oil Company in Oslo. A long first day of oral presentations and free-wheeling discussions by all participants set the stage and established the major themes of the conference. On the second and third days, a field trip from Oslo to Bergen allowed the group to examine a variety of lower Paleozoic ichnofabrics in outcrop settings. The group went to Bygdoy Peninsula southwest of Oslo to examine Lower Ordovician limestone and shale sequences, where the Huk Formation contains three suites of trace fossils at successive omission surfaces. Complex, composite ichnofabrics are well displayed in these rocks. A pre-omission episode of biogenic homogenization caused chaotic orientation of trilobite fragments. This event was followed by development of an omission surface, including an omission suite of Thalassinoides-like firmground burrows, upon which a postomission set of light-colored burrows penetrating the tops of the firmground and the omission suite burrow fills was emplaced. A second stop was at Kalvoya, near Sandvika, where the group observed Upper Ordovician nodular limestones in the Husberoya Formation. Abundant trace fossils occur in positive hyporelief, and there are three main trace fossil associations occurring in distinct ichnofabrics representing mid to upper-shoreface, lower to mid-shoreface, and offshore facies. At Kolsas Hill along Tyri Fjord the participants observed rippled sandstones of Silurian age that contained epichnial arthropod trackways (Steinfjordichnus). At Langodden on the shores of Lake Mjosa, the group examined ichnofabrics in Lower Cambrian sandstones of the Ringsaker Quartzite. Trace fossils are patchy but locally well displayed, and the Skolithos Ichnofacies is exemplified by Skolithos, Monocraterion and Diplocraterion. Discussions on the outcrop

Paleoecologic aspects of ichnofabrics (biogenic sedimentary fabrics) in deep-sea sediment

The paleoecology of deep-sea, benthic, macroinvertebrate communities is largely confined to the trace fossil record. While a few taxa have preservable hard parts, most of the deep-sea macrofauna are unpreservable as body fossils below the aragonite or calcite compensation depths. The ichnologic record provides important synecologic information regarding the behavioral diversity and endobenthic habitat partitioning of at least some community members.The deep-sea trace fossil record is strongly influenced by sediment composition (biogenic calcite vs. terrigenous clay), sedimentation regime (pelagic vs. turbidite deposition) and bioturbation history (continuous vs. discontinuous burrowing). These influences are directly reflected in the ichnofabric, or biogenic sedimentary fabric.Ichnofabrics of deep-sea sediments can shed light on the ecologic relationships of the infaunal community (trophic and tiering relationships), occupation of the sea floor by successive and different communities (deciphered from the different trace fossil suites in a composite ichnofabric), stability and firmness of the sedimentary substrate (revealed by burrow distinctness and deformation), interstitial oxygen conditions below the sea floor (determined from the abundance and preservation state of deposit-feeding burrows, such as Chondrites and Zoophycos), and effects of bioturbation patterns on early diagenetic processes (differential cementation and mineralization).The sedimentary habitat of the ancient deep-sea floor changes through time via compaction, dewatering, cementation and secondary mineralization. The benthos that inhabit this changing habitat likewise change according to their differing requirements for burrowing and endobenthic feeding. The resulting ichnofabric reflects a successive occupation of the sea floor by different types of organisms, ranging from shallow burrowers to deep burrowers to hard-substrate borers. Composite ichnofabrics thus can reveal a complex sequence of ecologic and diagenetic events.The tiered structure of infaunal communities in late Cretaceous and early Tertiary shelf-sea chalks is well-known, and because of their pelagic depositional aspect, these situations provide good analogues in outcrop for truly deep-sea environments. In the European and North American chalks, deeply emplaced fodinichnia (Thalassinoides, Chondrites and Zoophycos) typically are superimposed upon shallowly emplaced fodinichnia and pascichnia (Planolites and Teichichnus). Tracks and trails of epifaunal animals certainly were produced at the sediment-water interface, but they are not preserved. Very similar ichnofabrics occur in late Cretaceous and early Tertiary pelagic carbonates in New Zealand, where composite ichnofabrics reveal at least five main phases of occupation of the substrate by burrowers and borers. Multiple generations of Thalassinoides include both burrows and borings, each produced at different stages in the development of a major regional unconformity.Deep-sea pelagic deposits (in kilometers of water) represent a continuous accretion of the sea floor during sediment accumulation, accompanied by a continuous vertical shift of a tiered endobenthic community of burrowers that does not change appreciably over short time intervals. In partial contrast, shelf-sea pelagic deposits (in hundreds of meters of water) are affected more directly by short-term changes in bathymetry, salinity and oxygenation. The response of benthic communities to environmental shifts at the sea floor, therefore, is more pronounced in shelf-sea than in deep-sea settings.

Analysis of Composite Ichnofabrics: An Example in Uppermost Cretaceous Chalk of Denmark

Analysis of Composite Ichnofabrics: An Example in Uppermost Cretaceous Chalk of Denmark

Composite ichnofabrics and tiering of burrows

AbstractInfaunal communities in marine environments typically are tiered; that is, different taxa live at different depths within the sediment. Tiered suites of biogenic structures yield complex biogenic sedimentary fabrics (ichnofabrics), with the traces of deep-burrowing organisms overprinted on those of shallow-burrowing organisms. Careful analysis of crosscutting relationships of burrows in such composite ichnofabrics allows reconstruction of the tiered nature of fossil endobenthic communities. It is important to recognize that the best preserved and most prominently displayed trace fossils in most assemblages usually represent the deepest tier. Thus, they were farther removed from the sea floor and therefore less indicative of actual sea floor conditions than the more poorly preserved traces of the shallower tiers, on which the deeper traces are juxtaposed.