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Roland Goldring - One of the best experts on this subject based on the ideXlab platform.
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Spatangoid-produced Ichnofabrics (Bateig Limestone, Miocene, Spain) and the preservation of spatangoid trace fossils
Palaeogeography Palaeoclimatology Palaeoecology, 2008Co-Authors: J.m. De Gibert, Roland GoldringAbstract:A spatangoid-produced Ichnofabric is described from the Miocene Bateig Limestone, SE Spain. This Ichnofabric is characterized by the dominant presence of large meniscate burrows (Bichordites) produced by irregular echinoids. This constitutes an unusual mode of occurrence for spatangoid bioturbation, as their traces are most typically preserved in bases and tops of sandstone event beds. In fact, despite their important role as burrowers in modern settings (that can be extended back to the Early Cretaceous based on their body fossil record), spatangoid trace fossils (Scolicia and Bichordites) are comparatively rare. Several factors play an important role in their preservation: mechanism of burrowing, sediment characteristics, early diagenesis and presence/absence of deep-tier burrowers. Spatangoid-produced Ichnofabrics, such as those from the Bateig Limestone, characterize depositional settings with intermittent deposition of event beds where there is an absence of deeper-tier bioturbation.
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An Ichnofabric approach to the depositional interpretation of the intensely burrowed Bateig Limestone, Miocene, SE Spain
Sedimentary Geology, 2006Co-Authors: Jordi M. De Gibert, Roland GoldringAbstract:Abstract The foraminiferal-rich pelagic Bateig Limestone forms several varieties of the important building stones quarried at Bateig Hill in southeastern Spain. Three principal Ichnofabrics (Bichordites, mottled-Palaeophycus and mottled-Ophiomorpha) are recognized, which are present in at least two (possibly up to four) repeated successions (cycles). Each succession begins with an erosional event. The Bichordites Ichnofabric represents a new type of facies, formed as thin turbidity/grain flow, stratiform units derived from sediment slips off a fault into deep water. Each slipped unit became almost completely bioturbated by infaunal echinoids, colonizing by lateral migration. Because of the thinness of the units, successive colonizations tended to truncate the underlying burrows giving rise to a pseudo-stratification. As the Bichordites Ichnofabric accumulated on the fault apron, thus reducing the effective height of the fault scarp, the substrate gradually came under the influence of currents traversing the shelf. This led to a change in hydraulic regime, and to the mottled-Palaeophycus and mottled-Ophiomorpha Ichnofabrics in sediment deposited under bed load transport, and associated with laminar and cross-stratified beds and local muddy intervals. Reactivation of the fault triggered erosion and channeling and a return to grain flow sedimentation, and to the Bichordites Ichnofabric of the succeeding cycle. The highest unit of the Bateig Limestone is formed entirely of cross-stratified calcarenites with occasional Ophiomorpha (Ophiomorpha-primary lamination Ichnofabric) and is similar to many shallow marine facies but they still bear a significant content of pelagic foraminifera. The sedimentary setting bears resemblance with that described for the Pleistocene Monte Torre Paleostrait and the modern Strait of Messina (Italy), where the narrow morphology of the depositional area enhanced tidal currents and allowed for high-energy sandy deposition in relatively deep areas. More data on the Miocene paleogeography of the Bateig area should provide further testing for this hypothesis. The ichnofacies and stacking of the Bateig Limestone differ from the classic Seilacherian model in that they reflect changes in hydraulic process and are associated with faulting and subsidence and changes in sediment supply. Recognition of the unusual Ichnofabrics and their relationships provides a clear indication of the overall dynamic setting.
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The application of Ichnofabrics towards bridging the dichotomy between siliciclastic and carbonate shelf facies: examples from the Upper Jurassic Fulmar Formation (UK) and the Jubaila Formation (Saudi Arabia)
Proceedings of the Geologists' Association, 2005Co-Authors: Roland Goldring, Andrew M. Taylor, G. Wyn HughesAbstract:An initial study of the Ichnofabrics of the Upper Jurassic (Kimmeridgian) Jubaila Formation of Saudi Arabia shows that the Ichnofabrics are closely matched to the relatively well-described Ichnofabrics of the contemporary Fulmar Formation of the UK Continental Shelf (North Sea), in respect of the lower shoreface/offshore transition facies to offshore facies. The ichnology and Ichnofabrics of the Lower Jubaila Formation show that deposition took place on an open-marine platform on the Arabian craton subject to periodic storm activity, but under a persisting equilibrium between sediment accumulation and subsidence. This is consistent with the moderately deep-marine foraminiferal assemblages and the presence of calcareous nannofossils. Cyclicity is absent, though storm beds may be grouped, in contrast with the genetic sequences present in the rift and halokinetic scenario of the North Sea. In contrast with the siliciclastic setting hardgrounds (with Gastrochaenolites ), more common firmground omission surfaces, and micritic mudstones with Chondrites and Zoophycos are notable features of the carbonate facies. In siliciclastic successions (parasequences) the latter ichnotaxa are generally regarded as having been deposited in rather deeper water, but in the carbonate Jubaila Formation are interpreted as being associated with local areas of lower turbulence. Likewise, the hardgrounds and firmgrounds, which have not been traced laterally, are tentatively regarded to be of local significance.
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Analysis and application of Ichnofabrics
Earth-Science Reviews, 2002Co-Authors: Andrew M. Taylor, Roland Goldring, Stuart GowlandAbstract: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.
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Description and analysis of bioturbation and Ichnofabric
Journal of the Geological Society, 1993Co-Authors: A. M. Taylor, Roland GoldringAbstract: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.
J.m. De Gibert - One of the best experts on this subject based on the ideXlab platform.
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proximal distal Ichnofabric changes in a siliciclastic shelf early pliocene guadalquivir basin southwest spain
Palaeogeography Palaeoclimatology Palaeoecology, 2010Co-Authors: Julio Aguirre, J.m. De Gibert, Angel PugabernabeuAbstract:Abstract The lower Pliocene deposits, cropping out along the Atlantic coast of Cadiz, in the Conil–Cabo Roche area, formed on a shelf gently deepening towards the W–NW. Up to five types of facies can be recognized, distributed in belts from proximal to distal parts of the shelf: 1) Coarse-grained sandstone with trough cross-stratification facies on the most proximal parts of the shelf (inner-shelf deposits). 2) Medium-grained sandstone with low-angle planar cross-stratification facies deposited in a more distal position due to storm currents transporting sediment offshore. This facies intercalates with the previous trough cross-bedded sandstone. 3) Massive fine-grained sandstone and siltstone facies laterally and vertically related with the previous facies type and representing sediments formed in the middle shelf close to the storm wave-base. 4) Tabular sandstone bed facies corresponding to storm-bed deposits intercalated within the two previous facies. 5) Greenish–bluish shale facies accumulated on the outer shelf below storm wave-base. Three Ichnofabrics associated with these facies are recognized: 1) The two cross-bedded facies are dominated by a Macaronichnus Ichnofabric, characterized by Macaronichnus and Bichordites traces that represent colonization of a shifting sandy substrate by polychaetes (Macaronichnus tracemakers) and by sea urchins (Bichordites producers). 2) A Rosselia Ichnofabric, consisting of vertical traces of Rosselia cross-cutting Macaronichnus, characterizes the interval of massive fine-grained sandstone and silt facies and interbedded tabular sandstones. This Ichnofabric formed under high sedimentation rates with Rosselia traces exhibiting stacked patterns that indicate vertical readjustment following deposition. 3) Massive fine-grained sandstone and silt facies are distinguished by a Cylindrichnus Ichnofabric. This fabric was produced by the activity of a moderately diverse community dominated by sessile, burrow-dwelling, probably superficial-detritus-feeding polychaetes (Rosselia and Cylindrichnus tracemakers) and vagile, deposit-feeding polychaetes (Planolites producers). In addition, infaunal deposit/detritus-feeders producing spreiten structures (Teichichnus) are found in distal areas. Pervasive indistinct mottling of the sediment of this facies was probably due to the activity of very shallow burrowers in the uppermost sediment tiers. This proximal–distal replacement of Ichnofabrics reflects the change of benthic communities across the shelf. This distribution does not fit the traditional Seilacherian ichnofacies model for soft-ground shallow-marine settings, in which proximal, vertical-dwelling burrows of the Skolithos ichnofacies dominate high-energy environments. In the Pliocene of Cadiz, shallow-tier burrows of deposit/detritus-feeders characterize the high-energy facies instead, which fit better with the Cruziana ichnofacies. This deviation can be related with the particular palaeoenvironmental conditions. Thus, vagile, opportunistic deposit-feeders colonized the dune foreset when the dunes were stable, and the progradation of the structure favored the preservation of the traces.
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Proximal–distal Ichnofabric changes in a siliciclastic shelf, Early Pliocene, Guadalquivir Basin, southwest Spain
Palaeogeography Palaeoclimatology Palaeoecology, 2010Co-Authors: Julio Aguirre, J.m. De Gibert, Ángel Puga-bernabéuAbstract:Abstract The lower Pliocene deposits, cropping out along the Atlantic coast of Cadiz, in the Conil–Cabo Roche area, formed on a shelf gently deepening towards the W–NW. Up to five types of facies can be recognized, distributed in belts from proximal to distal parts of the shelf: 1) Coarse-grained sandstone with trough cross-stratification facies on the most proximal parts of the shelf (inner-shelf deposits). 2) Medium-grained sandstone with low-angle planar cross-stratification facies deposited in a more distal position due to storm currents transporting sediment offshore. This facies intercalates with the previous trough cross-bedded sandstone. 3) Massive fine-grained sandstone and siltstone facies laterally and vertically related with the previous facies type and representing sediments formed in the middle shelf close to the storm wave-base. 4) Tabular sandstone bed facies corresponding to storm-bed deposits intercalated within the two previous facies. 5) Greenish–bluish shale facies accumulated on the outer shelf below storm wave-base. Three Ichnofabrics associated with these facies are recognized: 1) The two cross-bedded facies are dominated by a Macaronichnus Ichnofabric, characterized by Macaronichnus and Bichordites traces that represent colonization of a shifting sandy substrate by polychaetes (Macaronichnus tracemakers) and by sea urchins (Bichordites producers). 2) A Rosselia Ichnofabric, consisting of vertical traces of Rosselia cross-cutting Macaronichnus, characterizes the interval of massive fine-grained sandstone and silt facies and interbedded tabular sandstones. This Ichnofabric formed under high sedimentation rates with Rosselia traces exhibiting stacked patterns that indicate vertical readjustment following deposition. 3) Massive fine-grained sandstone and silt facies are distinguished by a Cylindrichnus Ichnofabric. This fabric was produced by the activity of a moderately diverse community dominated by sessile, burrow-dwelling, probably superficial-detritus-feeding polychaetes (Rosselia and Cylindrichnus tracemakers) and vagile, deposit-feeding polychaetes (Planolites producers). In addition, infaunal deposit/detritus-feeders producing spreiten structures (Teichichnus) are found in distal areas. Pervasive indistinct mottling of the sediment of this facies was probably due to the activity of very shallow burrowers in the uppermost sediment tiers. This proximal–distal replacement of Ichnofabrics reflects the change of benthic communities across the shelf. This distribution does not fit the traditional Seilacherian ichnofacies model for soft-ground shallow-marine settings, in which proximal, vertical-dwelling burrows of the Skolithos ichnofacies dominate high-energy environments. In the Pliocene of Cadiz, shallow-tier burrows of deposit/detritus-feeders characterize the high-energy facies instead, which fit better with the Cruziana ichnofacies. This deviation can be related with the particular palaeoenvironmental conditions. Thus, vagile, opportunistic deposit-feeders colonized the dune foreset when the dunes were stable, and the progradation of the structure favored the preservation of the traces.
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Spatangoid-produced Ichnofabrics (Bateig Limestone, Miocene, Spain) and the preservation of spatangoid trace fossils
Palaeogeography Palaeoclimatology Palaeoecology, 2008Co-Authors: J.m. De Gibert, Roland GoldringAbstract:A spatangoid-produced Ichnofabric is described from the Miocene Bateig Limestone, SE Spain. This Ichnofabric is characterized by the dominant presence of large meniscate burrows (Bichordites) produced by irregular echinoids. This constitutes an unusual mode of occurrence for spatangoid bioturbation, as their traces are most typically preserved in bases and tops of sandstone event beds. In fact, despite their important role as burrowers in modern settings (that can be extended back to the Early Cretaceous based on their body fossil record), spatangoid trace fossils (Scolicia and Bichordites) are comparatively rare. Several factors play an important role in their preservation: mechanism of burrowing, sediment characteristics, early diagenesis and presence/absence of deep-tier burrowers. Spatangoid-produced Ichnofabrics, such as those from the Bateig Limestone, characterize depositional settings with intermittent deposition of event beds where there is an absence of deeper-tier bioturbation.
Francisco J. Rodríguez-tovar - One of the best experts on this subject based on the ideXlab platform.
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Applied ichnology in sedimentary geology: Python scripts as a method to automatize Ichnofabric analysis in marine core images
Computers & Geosciences, 2020Co-Authors: Santiago Casanova-arenillas, Francisco J. Rodríguez-tovar, Francisca Martínez-ruizAbstract:Abstract Image analysis has been succesfully applied in core research, especially in studies from modern deposits, to enhance the visibility of ichnological features and characterize ichnoassemblages and Ichnofabrics. Its application to ichnological research provides useful information for marine core studies, hence sedimentary geology, but also for hydrocarbon exploration. Here we develop a new methodology, using Python programming language, which significantly improve the ichnological analysis. The method automatizes the process of obtaining continuous ichnological information, in this case about the percentage of bioturbation as a key aspect of the Ichnofabric approach. The method affords the possibility of automatically generating continuous percentage and other index records using pixel counts in previously treated images. The resulting data sets are easy to correlate with the information usually obtained from cores (e.g., geochemical and mineralogical data). Such an integration of different proxies for to the field of sedimentary geology especially in the use of ichnological analysis, making it easier for the researcher, less time consuming, and more likely to be undertaken. The coding and sharing of open software tools allow for great flexibility, giving researchers in ichnology or related fields the option to implement new features, develop more complex tools to improve the package, and share findings with the scientific community.
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Lateral variability of Ichnofabrics in marine cores: Improving sedimentary basin analysis using Computed Tomography images and high-resolution digital treatment
Marine Geology, 2018Co-Authors: Francisco J. Rodríguez-tovar, Anxo Mena, Javier Dorador, F. Javier Hernández-molinaAbstract:Abstract Major Ichnofabric attributes may be related to a number of limiting marine parameters for tracemakers with paleoenvironmental significance, including ocean/atmosphere dynamics. This is why Ichnofabric analysis has proven to be a very useful tool in sedimentary basin analysis — as well as in other Earth Science disciplines — although it is a comparatively recent approach in ichnological research. Ichnofabric characterization is usually based on 2D visual observations of a single view in both outcrops and cores. Yet Ichnofabric features can vary vertically and laterally within a very short-distance, which may lead to misinterpretations. Here, a new methodological approach is presented, allowing for a more objective evaluation of Ichnofabric features, based on the high-resolution digital treatment of Computed Tomography images on marine sediments cores. The method evaluates variations in ichnoassemblages, cross-cutting relationships, and the degree of bioturbation structures in nearby selected images pertaining to several sections of the same interval of a core. Average values of the obtained data imply a significant improvement of the resolution than 2D observations, and therefore a more precise and objective characterization of Ichnofabrics. The usefulness of the method and its differences with respect to traditional Ichnofabric analysis are exemplified by a study of the gravity core FSG09-10 (Galicia Bank domain, NW Iberian Peninsula), showing as a very significant tool to interpret paleoenvironmental changes (i.e., sedimentation rate, nutrient availability, and bottom water oxygenation) from the Last Glacial Maximum (LGM) to Heinrich Event 1 (HE1). This example reveals the importance of proposed methods in order to characterize the Ichnofabrics, including their lateral variability, with clear implications for future research on basin analysis.
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Outcrop and core integrative Ichnofabric analysis of Miocene sediments from Lepe, Huelva (SW Spain): Improving depositional and paleoenvironmental interpretations
Sedimentary Geology, 2017Co-Authors: Francisco J. Rodríguez-tovar, Javier Dorador, Eduardo Mayoral, Ana M. SantosAbstract:Abstract Ichnofabric analysis was conducted in Miocene sediments from Lepe (Huelva, SW Spain) based on integrative outcrop and core research, to improve interpretations of depositional and paleoenvironmental conditions, with special attention to sequence stratigraphy. Seven intervals were differentiated in outcrops based on stratigraphic and ichnological features, consisting of two Ichnofabrics: Ophiomorpha-Thalassinoides-Spongeliomorpha Ichnofabric characterizes intervals 1, 2, 6, 7 and 8, while Palaeophycus-Planolites-Phycosiphon Ichnofabric characterizes intervals 3, 4 and 5. Fourteen Ichnofabrics were differentiated in the core, mainly in view of lithological features, including ferruginous material, grain size, mottled background, ichnotaxa, and Bioturbation Index. A comparison between outcrop and core Ichnofabrics through the upper 13.5 m, corresponding to the uppermost Tortonian-lowermost Messinian interval, revealed certain similarities as well as some differences. A continuous and relatively slow siliciclastic deposition with punctual variations in the sedimentation rate can be interpreted that, associated with favorable paleoenvironmental parameters such as aerobic conditions and nutrient availability, evidence that a well-developed and diverse macroinvertebrate trace maker community existed at that time. Softgrounds are dominant, but occasionally loosegrounds and even firmgrounds could develop. The Ichnofabric distribution shows long-range patterns in outcrop and core, and short-range patterns exclusively in core. Long-range patterns reflect the last phases of a transgressive system tract, with a “maximum flooding zone” at the end, and then a highstand normal regression. High-frequency, short-range, repetitive patterns in Ichnofabrics from core, mainly between Ichnofabrics 6/8 to 9 from lower to upper part of the pattern, can be linked to “local flooding surfaces”, subdividing the “maximum flooding zone” into parasequences. Our results reveals the usefulness of the integrative Ichnofabric analysis, including outcrop and core materials, in sedimentary basin analysis, assessing paleoenvironmental conditions and improving sequence stratigraphy characterization.
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Stratigraphic variation in Ichnofabrics at the “Shackleton Site” (IODP Site U1385) on the Iberian Margin: Paleoenvironmental implications
Marine Geology, 2016Co-Authors: Javier Dorador, Francisco J. Rodríguez-tovarAbstract:Abstract Ichnofabric analysis was conducted on cores from Site U1385 (IODP Expedition 339) to interpret paleoenvironmental conditions at the southwest margin of the Iberian Peninsula during the Pleistocene. Site U1385 provides an important record for the study of orbital and suborbital-scale climate variability, changes related to ocean/atmosphere dynamics, and affected environmental parameters. A detailed study of the Ichnofabric characterization is presented, focusing on the types of Ichnofabrics, relative abundance, amount of bioturbation, grouping, Ichnofabric succession/transitions and vertical distribution. Seven Ichnofabrics were differentiated; green mottled Ichnofabric, Planolites Ichnofabric, Taenidium & Planolites Ichnofabric, Thalassinoides -like & Palaeophycus Ichnofabric, Planolites & Thalassinoides / Thalassinoides -like Ichnofabric, Zoophycos Ichnofabric, and Chondrites Ichnofabric. They exhibit significant differences in terms of Ichnofabric features as well as in their stratigraphic distribution. The most abundant Ichnofabrics are Planolites & Thalassinoides / Thalassinoides -like Ichnofabric and green mottled Ichnofabrics, with a dominance of the middle tier Ichnofabrics. The degree of bioturbation is moderate, with a mean BI around 3, but showing a clear bimodal distribution: one group of intervals is characterized by high bioturbation (BI = 6), while another displays low-moderate BI values (BI = 1–2). In general, Ichnofabric features confirm generally good environmental conditions (oxic environment and high food availability) for the macrobenthic tracemaker community, especially favorable in the uppermost part of the sediment. A complete Ichnofabric succession, from deep to shallow tier Ichnofabrics, is commonly registered (i.e., Zoophycos Ichnofabric or Chondrites Ichnofabric to Planolites & Thalassinoides / Thalassinoides -like Ichnofabric, and then either to green mottled Ichnofabric, or to Planolites Ichnofabric and then green mottled Ichnofabric). However, there are some intervals where an incomplete succession between deep and shallow Ichnofabrics is observed (i.e., Chondrites Ichnofabric to green mottled Ichnofabric or Zoophycos Ichnofabric to green mottled Ichnofabric), indicating relevant modifications of environmental parameters such as oxygen or food supply. Types of Ichnofabrics and the Bioturbation Index show significant short-term changes through the studied core. Such variations are probably correlated to millennial-scale climatic perturbations, such as glacial terminations and related phenomena (Heinrich events, ice-rafting events, etc.), or long-term cyclic patterns related to orbital climate variability. The patterns could be tied to a significant change in the climate system, such as the one associated with the middle Pleistocene transition.
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Ichnofabric characterization in cores : a method of digital image treatment
Annales Societatis Geologorum Poloniae, 2015Co-Authors: Francisco J. Rodríguez-tovar, Javier DoradorAbstract:Ichnofabric analysis, as a relatively young ichnological approach, has witnessed rapid growth, showing its usefulness in basin analysis, with special attention to palaeoenvironmental interpretations. The Ichnofabric approach has evolved from the description of trace composition and the intensity of bioturbation to integrate detailed information on numerous Ichnofabric features, such as primary sedimentary structures, ichnological diversity, ichnological features, cross-cutting relation ships or tiering structures. This development has been associated with its application to the study of deep-sea sediments, especially in research on cores, which is not easy, owing to the particular features of cores. Here a method for improving Ichnofabric characterization in modern marine cores is presented, on the basis of digital high-resolution image treatment, with special emphasis on the quantification of Ichnofabric attributes. The proposed methodology is based on the modification of three image adjustments ( image adjustment ), the estimation of the percentage of the area occupied by bioturbation ( digital estimation ), the lateral and vertical quantification and comparison of pixel values for the infill of the trace fossils and the host sediment ( pixel counting ), and the integration of the information obtained in the visual representations of Ichnofabrics (the Ichnofabric representation ). The sequential application of these proposed steps allow, 1) better identification of trace fossils, together with cross-cutting relation ships and the characterization of trace-fossil assemblages, 2) estimation of the percent age of bioturbation associated to each ichnotaxon, the whole ichnocoenosis, or a complete Ichnofabric, 3) differentiation between biodeformational structures and trace fossils, discrimination between ichnotaxa, distinction between passively and actively infilled structures, and 4) evaluation of the depth of penetration by particular tracemakers.
Julio Aguirre - One of the best experts on this subject based on the ideXlab platform.
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proximal distal Ichnofabric changes in a siliciclastic shelf early pliocene guadalquivir basin southwest spain
Palaeogeography Palaeoclimatology Palaeoecology, 2010Co-Authors: Julio Aguirre, J.m. De Gibert, Angel PugabernabeuAbstract:Abstract The lower Pliocene deposits, cropping out along the Atlantic coast of Cadiz, in the Conil–Cabo Roche area, formed on a shelf gently deepening towards the W–NW. Up to five types of facies can be recognized, distributed in belts from proximal to distal parts of the shelf: 1) Coarse-grained sandstone with trough cross-stratification facies on the most proximal parts of the shelf (inner-shelf deposits). 2) Medium-grained sandstone with low-angle planar cross-stratification facies deposited in a more distal position due to storm currents transporting sediment offshore. This facies intercalates with the previous trough cross-bedded sandstone. 3) Massive fine-grained sandstone and siltstone facies laterally and vertically related with the previous facies type and representing sediments formed in the middle shelf close to the storm wave-base. 4) Tabular sandstone bed facies corresponding to storm-bed deposits intercalated within the two previous facies. 5) Greenish–bluish shale facies accumulated on the outer shelf below storm wave-base. Three Ichnofabrics associated with these facies are recognized: 1) The two cross-bedded facies are dominated by a Macaronichnus Ichnofabric, characterized by Macaronichnus and Bichordites traces that represent colonization of a shifting sandy substrate by polychaetes (Macaronichnus tracemakers) and by sea urchins (Bichordites producers). 2) A Rosselia Ichnofabric, consisting of vertical traces of Rosselia cross-cutting Macaronichnus, characterizes the interval of massive fine-grained sandstone and silt facies and interbedded tabular sandstones. This Ichnofabric formed under high sedimentation rates with Rosselia traces exhibiting stacked patterns that indicate vertical readjustment following deposition. 3) Massive fine-grained sandstone and silt facies are distinguished by a Cylindrichnus Ichnofabric. This fabric was produced by the activity of a moderately diverse community dominated by sessile, burrow-dwelling, probably superficial-detritus-feeding polychaetes (Rosselia and Cylindrichnus tracemakers) and vagile, deposit-feeding polychaetes (Planolites producers). In addition, infaunal deposit/detritus-feeders producing spreiten structures (Teichichnus) are found in distal areas. Pervasive indistinct mottling of the sediment of this facies was probably due to the activity of very shallow burrowers in the uppermost sediment tiers. This proximal–distal replacement of Ichnofabrics reflects the change of benthic communities across the shelf. This distribution does not fit the traditional Seilacherian ichnofacies model for soft-ground shallow-marine settings, in which proximal, vertical-dwelling burrows of the Skolithos ichnofacies dominate high-energy environments. In the Pliocene of Cadiz, shallow-tier burrows of deposit/detritus-feeders characterize the high-energy facies instead, which fit better with the Cruziana ichnofacies. This deviation can be related with the particular palaeoenvironmental conditions. Thus, vagile, opportunistic deposit-feeders colonized the dune foreset when the dunes were stable, and the progradation of the structure favored the preservation of the traces.
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Proximal–distal Ichnofabric changes in a siliciclastic shelf, Early Pliocene, Guadalquivir Basin, southwest Spain
Palaeogeography Palaeoclimatology Palaeoecology, 2010Co-Authors: Julio Aguirre, J.m. De Gibert, Ángel Puga-bernabéuAbstract:Abstract The lower Pliocene deposits, cropping out along the Atlantic coast of Cadiz, in the Conil–Cabo Roche area, formed on a shelf gently deepening towards the W–NW. Up to five types of facies can be recognized, distributed in belts from proximal to distal parts of the shelf: 1) Coarse-grained sandstone with trough cross-stratification facies on the most proximal parts of the shelf (inner-shelf deposits). 2) Medium-grained sandstone with low-angle planar cross-stratification facies deposited in a more distal position due to storm currents transporting sediment offshore. This facies intercalates with the previous trough cross-bedded sandstone. 3) Massive fine-grained sandstone and siltstone facies laterally and vertically related with the previous facies type and representing sediments formed in the middle shelf close to the storm wave-base. 4) Tabular sandstone bed facies corresponding to storm-bed deposits intercalated within the two previous facies. 5) Greenish–bluish shale facies accumulated on the outer shelf below storm wave-base. Three Ichnofabrics associated with these facies are recognized: 1) The two cross-bedded facies are dominated by a Macaronichnus Ichnofabric, characterized by Macaronichnus and Bichordites traces that represent colonization of a shifting sandy substrate by polychaetes (Macaronichnus tracemakers) and by sea urchins (Bichordites producers). 2) A Rosselia Ichnofabric, consisting of vertical traces of Rosselia cross-cutting Macaronichnus, characterizes the interval of massive fine-grained sandstone and silt facies and interbedded tabular sandstones. This Ichnofabric formed under high sedimentation rates with Rosselia traces exhibiting stacked patterns that indicate vertical readjustment following deposition. 3) Massive fine-grained sandstone and silt facies are distinguished by a Cylindrichnus Ichnofabric. This fabric was produced by the activity of a moderately diverse community dominated by sessile, burrow-dwelling, probably superficial-detritus-feeding polychaetes (Rosselia and Cylindrichnus tracemakers) and vagile, deposit-feeding polychaetes (Planolites producers). In addition, infaunal deposit/detritus-feeders producing spreiten structures (Teichichnus) are found in distal areas. Pervasive indistinct mottling of the sediment of this facies was probably due to the activity of very shallow burrowers in the uppermost sediment tiers. This proximal–distal replacement of Ichnofabrics reflects the change of benthic communities across the shelf. This distribution does not fit the traditional Seilacherian ichnofacies model for soft-ground shallow-marine settings, in which proximal, vertical-dwelling burrows of the Skolithos ichnofacies dominate high-energy environments. In the Pliocene of Cadiz, shallow-tier burrows of deposit/detritus-feeders characterize the high-energy facies instead, which fit better with the Cruziana ichnofacies. This deviation can be related with the particular palaeoenvironmental conditions. Thus, vagile, opportunistic deposit-feeders colonized the dune foreset when the dunes were stable, and the progradation of the structure favored the preservation of the traces.
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Lateral variability of Ichnofabrics in marine cores: Improving sedimentary basin analysis using Computed Tomography images and high-resolution digital treatment
Marine Geology, 2018Co-Authors: Francisco J. Rodríguez-tovar, Anxo Mena, Javier Dorador, F. Javier Hernández-molinaAbstract:Abstract Major Ichnofabric attributes may be related to a number of limiting marine parameters for tracemakers with paleoenvironmental significance, including ocean/atmosphere dynamics. This is why Ichnofabric analysis has proven to be a very useful tool in sedimentary basin analysis — as well as in other Earth Science disciplines — although it is a comparatively recent approach in ichnological research. Ichnofabric characterization is usually based on 2D visual observations of a single view in both outcrops and cores. Yet Ichnofabric features can vary vertically and laterally within a very short-distance, which may lead to misinterpretations. Here, a new methodological approach is presented, allowing for a more objective evaluation of Ichnofabric features, based on the high-resolution digital treatment of Computed Tomography images on marine sediments cores. The method evaluates variations in ichnoassemblages, cross-cutting relationships, and the degree of bioturbation structures in nearby selected images pertaining to several sections of the same interval of a core. Average values of the obtained data imply a significant improvement of the resolution than 2D observations, and therefore a more precise and objective characterization of Ichnofabrics. The usefulness of the method and its differences with respect to traditional Ichnofabric analysis are exemplified by a study of the gravity core FSG09-10 (Galicia Bank domain, NW Iberian Peninsula), showing as a very significant tool to interpret paleoenvironmental changes (i.e., sedimentation rate, nutrient availability, and bottom water oxygenation) from the Last Glacial Maximum (LGM) to Heinrich Event 1 (HE1). This example reveals the importance of proposed methods in order to characterize the Ichnofabrics, including their lateral variability, with clear implications for future research on basin analysis.
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Outcrop and core integrative Ichnofabric analysis of Miocene sediments from Lepe, Huelva (SW Spain): Improving depositional and paleoenvironmental interpretations
Sedimentary Geology, 2017Co-Authors: Francisco J. Rodríguez-tovar, Javier Dorador, Eduardo Mayoral, Ana M. SantosAbstract:Abstract Ichnofabric analysis was conducted in Miocene sediments from Lepe (Huelva, SW Spain) based on integrative outcrop and core research, to improve interpretations of depositional and paleoenvironmental conditions, with special attention to sequence stratigraphy. Seven intervals were differentiated in outcrops based on stratigraphic and ichnological features, consisting of two Ichnofabrics: Ophiomorpha-Thalassinoides-Spongeliomorpha Ichnofabric characterizes intervals 1, 2, 6, 7 and 8, while Palaeophycus-Planolites-Phycosiphon Ichnofabric characterizes intervals 3, 4 and 5. Fourteen Ichnofabrics were differentiated in the core, mainly in view of lithological features, including ferruginous material, grain size, mottled background, ichnotaxa, and Bioturbation Index. A comparison between outcrop and core Ichnofabrics through the upper 13.5 m, corresponding to the uppermost Tortonian-lowermost Messinian interval, revealed certain similarities as well as some differences. A continuous and relatively slow siliciclastic deposition with punctual variations in the sedimentation rate can be interpreted that, associated with favorable paleoenvironmental parameters such as aerobic conditions and nutrient availability, evidence that a well-developed and diverse macroinvertebrate trace maker community existed at that time. Softgrounds are dominant, but occasionally loosegrounds and even firmgrounds could develop. The Ichnofabric distribution shows long-range patterns in outcrop and core, and short-range patterns exclusively in core. Long-range patterns reflect the last phases of a transgressive system tract, with a “maximum flooding zone” at the end, and then a highstand normal regression. High-frequency, short-range, repetitive patterns in Ichnofabrics from core, mainly between Ichnofabrics 6/8 to 9 from lower to upper part of the pattern, can be linked to “local flooding surfaces”, subdividing the “maximum flooding zone” into parasequences. Our results reveals the usefulness of the integrative Ichnofabric analysis, including outcrop and core materials, in sedimentary basin analysis, assessing paleoenvironmental conditions and improving sequence stratigraphy characterization.
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Stratigraphic variation in Ichnofabrics at the “Shackleton Site” (IODP Site U1385) on the Iberian Margin: Paleoenvironmental implications
Marine Geology, 2016Co-Authors: Javier Dorador, Francisco J. Rodríguez-tovarAbstract:Abstract Ichnofabric analysis was conducted on cores from Site U1385 (IODP Expedition 339) to interpret paleoenvironmental conditions at the southwest margin of the Iberian Peninsula during the Pleistocene. Site U1385 provides an important record for the study of orbital and suborbital-scale climate variability, changes related to ocean/atmosphere dynamics, and affected environmental parameters. A detailed study of the Ichnofabric characterization is presented, focusing on the types of Ichnofabrics, relative abundance, amount of bioturbation, grouping, Ichnofabric succession/transitions and vertical distribution. Seven Ichnofabrics were differentiated; green mottled Ichnofabric, Planolites Ichnofabric, Taenidium & Planolites Ichnofabric, Thalassinoides -like & Palaeophycus Ichnofabric, Planolites & Thalassinoides / Thalassinoides -like Ichnofabric, Zoophycos Ichnofabric, and Chondrites Ichnofabric. They exhibit significant differences in terms of Ichnofabric features as well as in their stratigraphic distribution. The most abundant Ichnofabrics are Planolites & Thalassinoides / Thalassinoides -like Ichnofabric and green mottled Ichnofabrics, with a dominance of the middle tier Ichnofabrics. The degree of bioturbation is moderate, with a mean BI around 3, but showing a clear bimodal distribution: one group of intervals is characterized by high bioturbation (BI = 6), while another displays low-moderate BI values (BI = 1–2). In general, Ichnofabric features confirm generally good environmental conditions (oxic environment and high food availability) for the macrobenthic tracemaker community, especially favorable in the uppermost part of the sediment. A complete Ichnofabric succession, from deep to shallow tier Ichnofabrics, is commonly registered (i.e., Zoophycos Ichnofabric or Chondrites Ichnofabric to Planolites & Thalassinoides / Thalassinoides -like Ichnofabric, and then either to green mottled Ichnofabric, or to Planolites Ichnofabric and then green mottled Ichnofabric). However, there are some intervals where an incomplete succession between deep and shallow Ichnofabrics is observed (i.e., Chondrites Ichnofabric to green mottled Ichnofabric or Zoophycos Ichnofabric to green mottled Ichnofabric), indicating relevant modifications of environmental parameters such as oxygen or food supply. Types of Ichnofabrics and the Bioturbation Index show significant short-term changes through the studied core. Such variations are probably correlated to millennial-scale climatic perturbations, such as glacial terminations and related phenomena (Heinrich events, ice-rafting events, etc.), or long-term cyclic patterns related to orbital climate variability. The patterns could be tied to a significant change in the climate system, such as the one associated with the middle Pleistocene transition.
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Ichnofabric characterization in cores : a method of digital image treatment
Annales Societatis Geologorum Poloniae, 2015Co-Authors: Francisco J. Rodríguez-tovar, Javier DoradorAbstract:Ichnofabric analysis, as a relatively young ichnological approach, has witnessed rapid growth, showing its usefulness in basin analysis, with special attention to palaeoenvironmental interpretations. The Ichnofabric approach has evolved from the description of trace composition and the intensity of bioturbation to integrate detailed information on numerous Ichnofabric features, such as primary sedimentary structures, ichnological diversity, ichnological features, cross-cutting relation ships or tiering structures. This development has been associated with its application to the study of deep-sea sediments, especially in research on cores, which is not easy, owing to the particular features of cores. Here a method for improving Ichnofabric characterization in modern marine cores is presented, on the basis of digital high-resolution image treatment, with special emphasis on the quantification of Ichnofabric attributes. The proposed methodology is based on the modification of three image adjustments ( image adjustment ), the estimation of the percentage of the area occupied by bioturbation ( digital estimation ), the lateral and vertical quantification and comparison of pixel values for the infill of the trace fossils and the host sediment ( pixel counting ), and the integration of the information obtained in the visual representations of Ichnofabrics (the Ichnofabric representation ). The sequential application of these proposed steps allow, 1) better identification of trace fossils, together with cross-cutting relation ships and the characterization of trace-fossil assemblages, 2) estimation of the percent age of bioturbation associated to each ichnotaxon, the whole ichnocoenosis, or a complete Ichnofabric, 3) differentiation between biodeformational structures and trace fossils, discrimination between ichnotaxa, distinction between passively and actively infilled structures, and 4) evaluation of the depth of penetration by particular tracemakers.
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Ichnological analysis of Pleistocene sediments from the IODP Site U1385 “Shackleton Site” on the Iberian margin: Approaching paleoenvironmental conditions
Palaeogeography Palaeoclimatology Palaeoecology, 2014Co-Authors: Francisco J. Rodríguez-tovar, Javier DoradorAbstract:Ichnological analysis, focused on trace fossil assemblages and an Ichnofabric approach, with special attention to cross-cutting relationships, tiering, relative abundances and bioturbation degrees, has been used to assess environmental parameters affecting the Pleistocene macrobenthic tracemaker community at the IODP Expedition 339, Site U1385 “Shackleton Site” on the Iberian margin. The trace fossil assemblage consists of abundant Planolites, frequent yet sparsely distributed Palaeophycus, Thalassinoides (and Thalassinoides-like structures), and Taenidium, and localized Zoophycos and Chondrites. Other ichnotaxa, such as Phycosiphon and ?Scolicia, are rare. This assemblage is typical of the Zoophycos ichnofacies, though the distal expression of the Cruziana ichnofacies has a similar composition. Ichnofabrics reveal variable substrate colonization, with well defined cross-cutting relationships and tiering distribution. Differentiated Ichnofabrics are: green mottled Ichnofabric, Planolites Ichnofabric, Taenidium and Planolites Ichnofabric, Thalassinoides-like and Palaeophycus Ichnofabric, Planolites and Thalassinoides/Thalassinoides-like Ichnofabric, Zoophycos Ichnofabric, and Chondrites Ichnofabric, usually showing gradual transitions. A multi-tiered assemblage can be envisaged, with differentiation of the shallowest (biodeformational structures), shallow (Planolites, Palaeophycus and even Taenidium), middle (Thalassinoides/Thalassinoides-like structures), and lower (Zoophycos and Chondrites) tiers. According to the ichnological data, a general context of good bottom and pore-water oxygen conditions and organic matter availability can be interpreted, but localized dysaerobic intervals might be related with the record of Zoophycos and Chondrites. A constant rate of sedimentation shows only minor variations as revealed by Ichnofabric succession. Soupy, soft, and stiffgrounds are interpreted as inducing changes in ichnological features. Salinity and temperature have a minor incidence on the macrobenthic tracemaker community, causing only small changes in the trace fossils.