Bioturbation Index Research Articles

RESPONSE OF TRACEMAKERS TO TEMPORARY PLATFORM DROWNING: LOWER CENOMANIAN OF SOUTHERN ISTRIA (WESTERN CROATIA)

The Early–Late Cretaceous transition marked the beginning of the final disintegration of the Adriatic Carbonate Platform, which eventually resulted in the formation of the Dinarides mountain belt in the Paleogene, Neogene, and Quaternary. In southern Istria (Croatia) a continuous succession crops out that shows deepening from shallow subtidal to carbonate ramp in the latest Albian followed by gradual shallowing in the early Cenomanian, including well-preserved Ophiomorpha and Thalassinoides burrow systems in sections from Cintinera Cove and Vinkuran quarry. Burrow systems that overlie hummocky cross-stratified deposits are good indicators of specific environmental conditions during deposition. During transgression, favorable conditions for suspension- and deposit-feeding crustaceans were established which resulted in complex networks of Ophiomorpha and Thalassinoides. The increase in bioturbation up-section is recorded by a gradual increase in the bioturbation index as well as the size of burrow systems during transgressive events; a completely bioturbated interval in Vinkuran quarry indicates the maximum flooding surface. Formation of burrow systems was interrupted by subsequent clinoform progradation interpreted as a highstand shedding of shallow-marine bioclasts caused by high carbonate production and intense bioerosion of rudist and chondrodont shells, causing the relatively rapid infilling of the basin and re-establishment of the shallow-marine peritidal deposition in the entire northwestern part of the Adriatic Carbonate Platform.

Linking invertebrate burrow distributions (neoichnology) to physicochemical stresses on a sandy tidal flat: implications for the rock record

AbstractInvertebrate burrow distributions (neoichnology) across a modern tidal flat are presented as an analogue for interpreting the ichnology of palaeo‐tidal‐flat successions. Burrow distributions are linked to physical and chemical (physicochemical) stresses to establish the main controls on the distribution of biosedimentary structures. Across the tidal flat, there is clear heterogeneity in both the diversity of traces and the intensity of burrowing. This heterogeneity reflects a myriad of physicochemical stresses, with the sedimentation rate dominating burrow distributions. Across all substrates, the total area occupied by organisms rarely exceeds 3% of the tidal‐flat surface, and is commonly <1%; this equates to a bioturbation index value of one. To reach bioturbation index values of two to six, sediments must be available to biogenic reworking and/or recolonization. With an increasing sedimentation rate, substrates are rapidly buried and re‐exposed, which limits the time when a substrate is available to colonization. For palaeo‐ichnological studies, this research presents several key results. (i) Burrow cross‐cutting relationships in tidal‐flat successions commonly reflect natural heterogeneities in the areal distribution of infaunal communities, rather than infaunal tiering. (ii) Ichnofabric analysis of palaeo‐tidal flats with a high sedimentation rate would yield fabrics that reflect heterogeneities in the areal distribution of infaunal communities rather than variability in the physicochemical stresses of the environment. (iii) The composite trace‐fossil assemblage of tidal flats cannot be attributed to a single ichnofacies, but instead comprises elements typical of multiple ichnofacies. (iv) The main controls on trace assemblages across tidal flats in fully marine settings are sedimentological and include the sedimentation rate and, to a lesser extent, grain size.

Caracterização de Microfácies Sedimentares em Folhelhos da Formação Ponta Grossa (Devoniano) na Borda Leste da Bacia do Paraná

This study aims a microfacies characterization of outcropping shales in the Eastern border of Paraná Basin (34 samples) representing a transgressive system tract (lower Jaguariaíva Member, 20 samples) and a highstand system tract (upper São Domingos Member, 14 samples) of the Ponta Grossa Formation, inserted in a 3rd order depositional sequence cycle (megasequence), and their interpretation in terms of sedimentary processes and paleoenvironments. The study is based on petrographic microscopy, aided by XRD (clay mineralogy) and geochemical (TOC) data. The microfacies analysis took into consideration the mineralogy, microtexture, microfabric, microstructure (physical and biogenic), microfossils, particulate organic content, stratal variation, and colour in plugues and thin sections. Results point out 9 microfacies, 2 of them typical of the TST (M1 and M2) and 7 of the HST (M3 to M9). The microfacies from the TST show in general a chaotic microfabric (in part resulted from a higher bioturbation index), and a fine sand and silt rich composition (except one, associated to the 3rd order MFS); whereas the HST are silt and clay rich, and show a fairly oriented microfabric, and better preserved physical structures. Bottom wave reworking followed by biogenic activity (bioturbation) in proximal offshore paleoenvironmets are responsible for the best reservoir sedimentological characteristics of the microfacies M1 (associated to the TST) among all of them. Distal hyperpycnal flows, decantation from bottom wave resuspension plumes, microbial mats development, and low biogenic activity in prodelta/offshore paleoenvironments are responsible for best sedimentological sealing characteristics of the microfacies M3-M9 (associated to the HST).

Two episodic changes of trace fossils through the Permian-Triassic transition in the Meishan cores, Zhejiang Province

Six ichnogenera, Chondrites, Palaeophycus, Planolites, Rhizocorallium, Skolithos, and Thalassinoides, were identified from the drilling cores near the Global Stratotype Section and Point (GSSP) of Permian-Triassic boundary at Meishan, Zhejiang Province. The ichnological indices, including abundance, bioturbation index, and disturbed depth of trace fossils, show two episodes of intense changes near the Permian-Triassic Boundary (PTB). Episode I occurred in Beds 25–27b when the ecologically complicate forms such as Chondrites, Skolithos, Rhizocorallium, and Thalassinoides disappeared hereafter, the bioturbation index reduced from 1–5 to 1–3, and the disturbed depth declined from 5–66 to 2–5 cm. Episode II took place at the base of Bed 33 with the disappearance of Palaeophycus and Planolites, and subsequent absence of trace fossils and bioturbation till the middle-upper part of Bed 41 when the disturbed structures reoccurred, but they are only tiny Planolites and the bioturbation index was never higher than 3 and the disturbed depth less than 4 mm. Episode I shows an intense change, corresponding to the main stage of the end-Permian mass extinction, whereas Episode II is relatively weak, corresponding to the epilogue of the mass extinction of trace makers in the Early Triassic. Subsequently, ichnofossils were dominated by surface tracks in simple ecological habit and structures. This phenomenon indicates that the Early Triassic benthonic fauna is changed from sessile benthic system to mobile benthic system after the end-Permian mass extinction. In other words, the evolution of the trace fossils across the Permian-Triassic transition had an episodic process similar to the body fossils. In addition, the change of ichnofabrics is well coincided with the negative excursion of carbon isotopes and the expansion of cyanobacteria. As the results of physical and biogenic processes, trace fossils provided unique materials for the study of the biotic and environmental events, as well as their coupling evolution through the great Permian-Triassic transition.

Assinaturas icnológicas da sucessão sedimentar Rio Bonito no bloco central da jazida carbonífera de Iruí, Cachoeira do Sul (RS)

The subsurface deposits of the Rio Bonito sedimentary succession in the central block of the Irui coal mine (Cachoeira do Sul, Rio Grande do Sul State, S Brazil) is composed of sedimentary facies associations that represent deposition in dominantly marginal-marine and shallow-marine settings, the later in minor scale. Ichnofabrics of Chondrites , Chondrites-Helmintopsis-Planolites , Cylindrichnus-Thalassinoides , Helminthopsis , Macaronichnus , Ophiomorpha , Palaeophycus, Planolites , Thalassinoides , and Thalassinoides-Palaeophycus occur in the marginal marine settings , whereas the Thalassinoides-Palaeophycus-Helminthopsis ichnofabric is present in the shallow marine deposits. The marginal-marine ichnofabrics are characterized by the low bioturbation index, the reduced size of burrows, and the low ichnodiversity, whereas the marine ones show a moderate to high degree of bioturbation and low ichnodiversity. The ichnofabric pattern, its stratigraphic distribution, and its sedimentological relationships allow recognizing four ichnological signatures, three suggesting stress caused by changes in the salinity gradient, and one substrate-controlled. Ichnofabrics of Helmithopsis, Palapeophycus , and Planolites in lithofacies SiltArg suggest the dominance of oligohaline to freshwater conditions. Ichnofabrics of Thalassinoides-Palaeophycus and Cylindrichnus-Thalassinoides refl ect the dominance of mesohaline conditions, each one representing, respectively, more quiet and stable environments (impoverished Cruziana Ichnofacies suite), and moderate to high energy settings (mixed Skolithos-Cruziana Ichnofacies suite). The Thalassinoides-Palaeophycus-Helminthopsis ichnofabric represents an arquetypical Cruziana Ichnofacies suite, indicating shallow marine settings. The reduced size of the burrows, however, suggests dominance of polyhaline rather than stenohaline conditions and its local distribution allow infer deposition in embayments, which mimic the environmental conditions found in the lower shorefce / offshore transition zones. The Thalassinoides ichnofabric is substrate-controlled, representing a Glossifungites Ichnofacies suite. It demarks two autogenic stratigraphic surfaces, and one allogenic stratigraphic surface interpreted as a sequence boundary. The integrated ichnological and sedimentological analysis in high resolution scale, allowed refining the existent paleoenvironmental and stratigraphic interpretations of the Rio Bonito sedimentary succession in the study area. Key words: ichnology, sedimentology, ichnofabrics, ichnological signatures, coastal deposits.

Assinaturas icnológicas da sucessão sedimentar Rio Bonito no bloco central da jazida carbonífera de Iruí, Cachoeira do Sul (RS)

The subsurface deposits of the Rio Bonito sedimentary succession in the central block of the Iruí coal mine (Cachoeira do Sul, Rio Grande do Sul State, S Brazil) is composed of sedimentary facies associations that represent deposition in dominantly marginal-marine and shallow-marine settings, the later in minor scale. Ichnofabrics of Chondrites, Chondrites-Helmintopsis-Planolites, Cylindrichnus-Thalassinoides, Helminthopsis, Macaronichnus, Ophiomorpha, Palaeophycus, Planolites, Thalassinoides, and Thalassinoides-Palaeophycus occur in the marginal marine settings, whereas the Thalassinoides-Palaeophycus-Helminthopsis ichnofabric is present in the shallow marine deposits. The marginal-marine ichnofabrics are characterized by the low bioturbation index, the reduced size of burrows, and the low ichnodiversity, whereas the marine ones show a moderate to high degree of bioturbation and low ichnodiversity. The ichnofabric pattern, its stratigraphic distribution, and its sedimentological relationships allow recognizing four ichnological signatures, three suggesting stress caused by changes in the salinity gradient, and one substrate-controlled. Ichnofabrics of Helmithopsis, Palapeophycus, and Planolites in lithofacies SiltArg suggest the dominance of oligohaline to freshwater conditions. Ichnofabrics of Thalassinoides-Palaeophycus and Cylindrichnus-Thalassinoides refl ect the dominance of mesohaline conditions, each one representing, respectively, more quiet and stable environments (impoverished Cruziana Ichnofacies suite), and moderate to high energy settings (mixed Skolithos-Cruziana Ichnofacies suite). The Thalassinoides-Palaeophycus-Helminthopsis ichnofabric represents an arquetypical Cruziana Ichnofacies suite, indicating shallow marine settings. The reduced size of the burrows, however, suggests dominance of polyhaline rather than stenohaline conditions and its local distribution allow infer deposition in embayments, which mimic the environmental conditions found in the lower shorefce/ offshore transition zones. The Thalassinoides ichnofabric is substrate-controlled, representing a Glossifungites Ichnofacies suite. It demarks two autogenic stratigraphic surfaces, and one allogenic stratigraphic surface interpreted as a sequence boundary. The integrated ichnological and sedimentological analysis in high resolution scale, allowed refining the existent paleoenvironmental and stratigraphic interpretations of the Rio Bonito sedimentary succession in the study area. Key words: ichnology, sedimentology, ichnofabrics, ichnological signatures, coastal deposits.

Image analysis techniques and gray-level co-occurrence matrices (GLCM) for calculating bioturbation indices and characterizing biogenic sedimentary structures

Aspects of texture and structure in a bed resulting from bioturbation can provide valuable information about the ecology and environment at the time of deposition. However, not only the degree of bioturbation, but the structure of the burrows is important for interpreting biogenic fabrics. Here, image analysis is applied to real and artificial images of biogenic sedimentary structures. Image segmentation was applied to images of Middle Ordovician biogenic sedimentary structures from Dixon, Illinois (Pecatonica Formation), isolating the biogenic sedimentary structures. A gray-level co-occurrence matrix (GLCM) is calculated from the segmented image and eight artificial images representing different levels of image noise. Texture measures were calculated from the GLCMs and compared with identify scale and directional structural differences between the images. Principal component analysis was used to statistically group the images. Artificial images were found to be distinguishable from the real images by GLCM texture measures, and the real images differed most significantly at the largest scales.

The importance of Planolites in the Cambrian substrate revolution

Early Cambrian subtidal shelf substrates were characterized by low water content and steep chemical gradients, conditions likely facilitated by the presence of microbial mats as reflected by an abundance of microbially-mediated sedimentary structures in Lower Cambrian strata. Such substrate conditions would have been unfavourable for burrowing by benthic metazoans. A combination of environmental restrictions and a lack of adaptations to vertical burrowing likely prevented most benthic metazoans from burrowing infaunally in Early Cambrian subtidal shelf substrates. The eventual acquisition of burrowing adaptations by benthic metazoans later in the Cambrian promoted an increase in the depth and intensity of bioturbation and initiated a transition toward well-hydrated substrates in which extensive infaunal activity was possible. Siliciclastic units of the Lower Cambrian succession in the White–Inyo Mountains, eastern California, contain abundant horizontal bioturbation on bedding planes, as documented by bedding plane bioturbation indices, but little vertical bioturbation, as shown by ichnofabric indices and x-radiography. Planolites, a simple horizontal trace fossil, represents the dominant type of bioturbation in these units. Planolites is found in a range of diameters, indicating that more than one species of tracemaker likely produced this type of trace. Although these Planolites do not have a vertical component, their abundance on bedding planes indicates that the activities of Planolites tracemakers had a significant impact on subtidal shelf substrates, represented by Lower Cambrian units in the White–Inyo Mountains, early in the Cambrian substrate revolution.

The Temporal Significance of Bioturbation in Backshore Deposits: Waterside Beach, New Brunswick, Canada

Abstract This paper provides an estimate of the temporal nature and environmental implications of bioturbation in upper-foreshore and backshore deposits resulting from the burrowing activity of talitrid amphipods at Waterside Beach, Bay of Fundy, Canada. Short-term preservation potential is assessed by comparing shore-normal variations in burrow morphologies and densities to grain-size distribution, and hydraulic and eolian processes. The intensity and distribution of burrowing is linked to depositional environment and provides a temporal framework for bioturbation indices in ancient upper-foreshore and backshore deposits. Bioturbation in foreshore and backshore successions provides a means for predicting short-term, autocyclic processes in the rock record, in that: (1) the initial occurrence of burrowing marks the transition from the foreshore to the backshore, and (2) the degree of bioturbation may be used to predict depositional rates and processes. At Waterside, bioturbation indices (BI) of two or les...

Estructuras de escape y equilibrio asociadas a Conichnus conicus como indicadores de tasas de sedimentación variables en medios litorales tortonienses del SO de España

Numerous and large vertically extensive specimens of Conichnus conicus are described from the Tortonian deposits of the central Guadalquivir Basin (SW Spain). These burrowing structures form a low bioturbation index of the ichnofabric, which allows one to infer the original depositional setting. Both ichnological and sedimentological features suggest a coastal to shallow marine environment dominated by high sediment supply and high-energy sedimentary processes. Conichnus exhibits a characteristic internal fabric that reflects changes in sedimentation rates linked to various processes: (1) initial substrate penetration by the tracemaker; (2) gradual retrusive movement in response to rapid but continuous sediment aggradation; 3) moderate to high rates of retrusive migration as a consequence of rapid to very rapid sediment aggradation and tracemaker escape; and, finally, (4) abandonment of the burrow or burial of the tracemaker subsequently in response to extremely high sediment accumulation rates. Conichnus has been also described from other areas with similar deposits of different ages, where its important value as a paleoenvironmental indicator similarly has been indicated.

Biogeochemistry of methylmercury in sediments of Long Island Sound

Cycling of toxic monomethylmercury (MMHg) in biologically productive coastal marine systems is affected by geochemical and macro/microbiological factors that control its production and mobilization from sediment. We examined the biogeochemistry of MMHg in sediment at three sites in Long Island Sound (LIS) in March, June, and August. Bioturbation homogenizes profiles of inorganic Hg (Hg(II)=total Hg−MMHg) in the upper 10 cm of sediment, whereas MMHg is enriched in surface material, indicating rapid and dynamic cycling of the toxic species. Sediment–water partitioning of MMHg and Hg(II) is controlled largely by sedimentary organic matter. Distribution coefficients ( K D; l kg −1) of MMHg and Hg(II) are correlated with those for organic carbon, which suggests that adsorption/desorption of Hg species with sediment particles is mediated by partitioning of associated organic ligands. A fraction of MMHg and Hg(II) on sediment particles is associated with Fe complexes, presumably oxyhydroxides. Bioturbation enhances Hg methylation; subsurface peaks in 200Hg methylation potentials coincide with anomalies in a bioturbation index (d[organic matter]/d z) that indicate non-local disturbance of sediment. The estimated diffusive sediment–water flux of MMHg in LIS (55±20 mol year −1) exceeds inputs from external sources. This indicates that in situ production is the major source of MMHg to LIS, and by extension, other comparable near-shore systems. Furthermore, sedimentary methylation can account for most of the MMHg in primary producers of LIS. Hence, through dietary bioaccumulation, much of the MMHg in higher trophic levels within the Sound may be attributed to MMHg production in the sediments.

Analysis and application of ichnofabrics

Bioturbation at all scales, which tends to replace the primary fabric of a sediment by the ichnofabric (the overall fabric of a sediment that has been bioturbated), is now recognised as playing a major role in facies interpretation. The manner in which the substrate may be colonized, and the physical, chemical and ecological controls (grainsize, sedimentation rate, oxygenation, nutrition, salinity, ethology, community structure and succession), together with the several ways in which the substrate is tiered by bioturbators, are the factors and processes that determine the nature of the ichnofabric. Eleven main styles of substrate tiering are described, ranging from single, pioneer colonization to complex tiering under equilibria, their modification under environmental deterioration and amelioration, and diagenetic enhancement or obscuration. Ichnofabrics may be assessed by four attributes: primary sedimentary factors, Bioturbation Index (BI), burrow size and frequency, and ichnological diversity. Construction of tier and ichnofabric constituent diagrams aid visualization and comparison. The breaks or changes in colonization and style of tiering at key stratal surfaces accentuate the surfaces, and many reflect a major environmental shift of the trace-forming biota due to change in hydrodynamic regime (leading to non-deposition and/or erosion and/or lithification), change in salinity regime, or subaerial exposure. The succession of gradational or abrupt changes in ichnofabric through genetically related successions, together with changes in colonization and tiering across event beds, may also be interpreted in terms of changes in environmental parameters. It is not the ichnotaxa per se that are important in discriminating between ichnofabrics, but rather the environmental conditions that determine the overall style of colonization. Fabrics composed of different ichnotaxa (and different taphonomies) but similar tier structure and ichnoguild may form in similar environments of different age or different latitude. Appreciation of colonization and tiering styles places ancient ichnofabrics on a sound process-related basis for environmental interpretation.

Trace fossils of the Jurassic, blue Lias, Lyme Regis, Southern England

The Lower Jurassic, Blue Lias Formation at Lyme Regis, Dorset, England is rhythmically bedded with symmetrical rhythms consisting of laminated black shale followed by dark then pale marls (sometimes cemented into pale limestones) and back to laminated black shale. Its trace fossil fauna includes nine ichno‐genera and represents a shallow shelf paleoenviron‐ment. The ichnofauna occurs in three assemblages named after consistently occurring ichnogenera. A Chondrites assemblage (diversity = 1 ichnogenus) and a Chondrites‐Arenicolites assemblage (diversity = 2–3 ichnogenera) are typical of dark marls but may penetrate tops of laminated black shales. A thalassi‐noides‐Chondrites‐Arenicolites assemblage (diversity up to 7 ichnogenera) is typical of pale marls or limestones. Blue Lias limestones are diagenetic: dark laminated limestones and pale bioturbated limestones are cemented equivalents of laminated black shales and pale marls, respectively. However, pale burrow fills in darker sediments and vice versa confirm the rhythms are primary. Rhythms represent redox cycles, fluctuating from anoxic laminated black shales lacking mac‐robenthos or infauna (bioturbation index = 0) to oxic, bioturbated, pale marls or limestones with large mac‐robenthos such as Gryphaea or Plagiostoma and diverse infauna (bioturbation index = 5).

Ichnofabric analysis of the Pliocene marine sediments of the Var basin (Nice, SE France)

The ichnological content of the Pliocene Saint-Isidore outcrop (Nice, SE France) is studied. The deposits belong to the sedimentary filling of the Pliocene Var ria and correspond to the distal part of a medium-depth submarine fan. Dominant trace fossils are feeding burrows, such as Phycosiphon, Scalarituba and Teichichnus. Three ichnofabrics have been defined from their bioturbation indices, ichnotaxonomic composition, and trace fossil tiering, and each is related with a particular facies association. Diversity, degree of bioturbation, and complexity of tiering in those facies decrease as palaeoenvironments become more unstable.

Sun Hats and Ichnofabrics: Fourth International Ichnofabric Workshop, San Salvador Island, Bahamas, March 15-22, 1997

Sun Hats and Ichnofabrics: Fourth International Ichnofabric Workshop, San Salvador Island, Bahamas, March 15-22, 1997

A Semiquantitative Field Method for Evaluating Bioturbation on Bedding Planes

Amount of bioturbation on bedding planes records the relationship between physical and chemical depositional conditions and biological activity. We propose a simple and easy-to-use method for field estimation of horizontal disruption using bedding-plane bioturbation indices that allow rapid generation of large data sets. Photographs of a representative subset of observations can be evaluated in the laboratory using image analysis and statistical analysis programs, providing a check on accuracy and potentially yielding additional information on the size, shape, and distribution of burrows and bioturbated patches. Extent of bioturbation on bedding planes can be integrated with other sedimentologic and ichnologic characteristics to interpret the infaunal community paleoecology and to reconstruct the history of the depositional, erosional, and burrowing events. Furthermore, use of the bedding-plane bioturbation indices and ichnofabric indices on vertical surfaces facilitates comparison of the extent of bioturbation through time, within and between facies, and across and between basins. It therefore enhances recognition of significant changes in physical processes, chemical conditions, and biological activity, and is a powerful tool in identifying long-term biological trends.

Secular distribution of Burgess‐Shale‐type preservation

Burgess-Shale-type preservation is defined as a taphonomic pathway involving the exceptional organic preservation of non-mineralizing organisms in fully marine siliciclastic sediments. In the Phanerozoic it occurs widely in Lower and Middle Cambrian sequences but subsequently disappears as a significant taphonomic mode. The hypothesis that this distribution derives solely from a secular increase in the depth of bioturbation is falsified: low bioturbation indices do not prevent the rapid enzymatic degradation of organic structure, nor do they account for the conspicuous absence of comparable preservation during the Vendian. An earlier, Late Riphean (ca. 750–850 Ma), interval of enhanced organic-walled fossil preservation suggests a long-term recurrence in Burgess-Shale-type taphonomy that is independent of metazoan activity. A model based on the potentially powerful anti-enzymatic and/or stabilizing effects of clay minerals on organic molecules is proposed to account for Burgess-Shale-type preservation. Long-term changes in average clay mineralogies and the ocean chemistry that determines their interaction with organic molecules are likely to have induced the pronounced secular distribution of these fossil biotas, while regional variations in tectonism, weathering, etc., explain their non-uniform geographic distribution; the close correlation between exceptional, organic-walled fossil preservation and volcano-genic sedimentation in Tertiary lake deposits provides a compelling analogue. Recognition of a temporal control on Burgess-Shale-type preservation constrains the evolutionary scenarios that can be drawn from such biotas; significantly, neither the initial rate of appearance, nor the ultimate fate of Burgess-Shale-type taxa can be directly assessed. □Taphonomy, exceptional preservation, organic preservation, fossil Lagerstatten, Burgess Shale, clay mineralogy, clay-organic interactions, secular change, Cambrian, Proterozoic.

Description and analysis of bioturbation and ichnofabric

A new scheme for the description and analysis of bioturbation and the resultant ichnofabrics is proposed. This system can be used in core and field-based studies and consists of two parts. (1) A bioturbation index in which a descriptive grade is assigned to the degree of bioturbation. This integrates the sedimentology and ichnology, where the higher grades of bioturbation result from increased burrow overlap and the subsequent loss of the primary sedimentary fabric. (2) An ichnofabric constituent diagram which records the detail of the ichnofabric by graphically plotting the dimensional data of the ichnotaxa and their order of emplacement against their coverage. This scheme differs from previous attempts to characterize bioturbation using semi-quantatitive methods and visually portrays the ichnofabric so that comparative studies can be carried out. This is of particular use in facies analysis, the establishment of the ichnocoenoses and tier diagrams, and within sequence stratigraphic studies so that hiatal surfaces can be recognized.