Trace Fossil Associations Research Articles

Controversies in anesthesia for carotid endarterectomy: General versus regional anesthesia

Shorefaces can display strong facies variability and integration of sedimentology and ichnology provides a high-resolution model to identify variations among strongly storm-dominated (high energy), moderately storm-affected (intermediate energy), and weakly storm-affected (low energy) shoreface deposits. In addition, ichnology has proved to be of help to delineate parasequences as trace-fossil associations are excellent indicators of environmental conditions which typically change along the depositional profile. Shallow-marine deposits and associated ichnofaunas from the Mulichinco Formation (Valanginian, Lower Cretaceous) in Puerta Curaco, Neuquén Basin, western Argentina, were analyzed to evaluate stress factors on shoreface benthos and parasequence architecture.During storm-dominated conditions, the Skolithos Ichnofacies prevails within the offshore transition and lower shoreface represented by assemblages dominated by Thalassinoides isp. and Ophiomorpha irregulaire. Under weakly storm-affected conditions, the Cruziana Ichnofacies is recognized, characterized by assemblages dominated by Thalassinoides isp. and Gyrochorte comosa in the offshore transition, and by Gyrochorte comosa within the lower shoreface. Storm-influenced conditions yield wider ichnologic variability, showing elements of both ichnofacies.Storm influence on sedimentation is affected by both allogenic (e.g. tectonic subsidence, sea-level, and sediment influx) and autogenic (e.g. hydrodynamic) controls at both parasequence and intra-parasequence scales. Four distinct types of parasequences were recognized, strongly storm-dominated, moderately storm-affected, moderately storm-affected – strongly fair-weather reworked, and weakly storm-affected, categorized based on parasequence architectural variability derived from varying degrees of storm and fair-weather wave influence. The new type of shoreface described here, the moderately storm-affected – strongly fair-weather reworked shoreface, features storm deposits reworked thoroughly by fair-weather waves. During fair-weather wave reworking, elements of the Cruziana Ichnofacies are overprinted upon relict elements of the Skolithos Ichnofacies from previous storm induced deposition. This type of shoreface, commonly overlooked in past literature, expands our understanding of the sedimentary dynamics and stratigraphic architecture in a shoreface susceptible to various parasequence and intra-parasequence scale degrees of storm and fair-weather wave influence.

Stromatolitic and Trace Fossils Community of the Cerro Victoria Formation, Arroyo del Soldado Group (Lowermost Cambrian, Uruguay)

The Cerro Victoria Formation of the Arroyo del Soldado Group (Uruguay) comprises 400 m of mainly stromatolitic, micritic and oolitic limestones. In this low-diversity stromatolite paleocommunity, moundlike and planar laminites dominate, but columnar forms, ooids and pisoids occur as well. Stromatolites played a major role in the construction of the carbonate ramp, which developed onto a passive (eastern) margin of the Río de la Plata Craton. A paleobiological reconstruction of the stomatolite community, which includes subtidal, intertidal and supratidal environments, is presented. A low-diversity trace fossil association, dessignated as “Thalassinoides-Gyrolithes-Palaeophycus” assemblage, is preserved in syngenetic concretions. The stromatolite community, ichnofossil assemblage and ichnofabrics are typical for the lowermost Cambrian, corroborating earlier age estimations. The unit represents a shallowing-upward sequence deposited under predominantly subtidal, normal marine, high energy conditions. Tropical climate prevailed, as shown by thick carbonate deposits, evaporitic minerals (halite, gypsum) and abundance of ooids. The Cambrian of western Gondwana is characterized by scarcity of carbonate ramps. This was mainly determined by high siliciclastic input related to erosion of the Pan African-Rio Doce orogenic belts. Carbonate ramps developed in blocks located at tropical paleolatitudes and characterized by low clastic input, such as the Nico Pérez Terrane and Argentine Precordillera.

Climatic control of trace fossil distribution in the marine realm

Abstract Modern coastal and shoreface faunas exhibit strong latitude (climate) controlled distributions. In contrast, most ichnotaxa are long-ranging, and ichnofacies are widely distributed geographically. This is readily explained by the dominantly warmer and more equable climates of much of the past, as well as the diversity of the producers of most ichnotaxa. Nevertheless, in the Pleistocene, and in the Eocene, cool-water ichnofabrics can be recognized. The latitudinal distributions of thalassinidean crustaceans and infaunal spatangoid echinoids are examined because of their propensity to form distinctive and often abundant trace fossils. Three climatic zones are tentatively recognized from modern shore and shoreface sediments, and which are considered to extend back to the Mesozoic: tropical and subtropical with pellet-lined burrows ( Ophiomorpha ), echinoid burrows and other traces; temperate with echinoid burrows and mud-lined or non-lined thalassinidean burrows ( Thalassinoides ), but without Ophiomorpha ; and arctic (cold waters) with only a molluscan and annelid trace fossil association. Examples demonstrating this climatic trend are drawn from the Cenozoic and Pleistocene.

Cambro‐Ordovician trace fossils from the SW‐Norwegian Caledonides

AbstractA diverse trace fossil association is described for the first time from low‐grade metamorphic rocks of the SW‐Norwegian Caledonides. The investigated cliff sections with autochthonous to parautochthonous metasediments comprise a coarsening‐ and thickening‐upward succession interpreted as prograding delta deposits. Sedimentary features indicate a tide‐influenced environment. Twenty‐one ichnospecies have been identified and assigned to the Cruziana and Skolithos ichnofacies, including the oldest record of Beaconites capronus and Macaronichnus segregatis. Cruziana ichnostratigraphy (sensu lato), previously rarely used in other palaeocontinents than Gondwana, allows an age determination for these metasediments of Middle Cambrian to Lower Ordovician as indicated by the presence of Cruziana barbata, C. furcifera, C. rugosa, C. semiplicata, Didymaulichnus rouaulti and Rusophycus ramellensis. Baltica was geographically the most isolated from the other three large continents (Gondwana, Laurentia and Siberia) during Cambro‐Ordovician time, and provinciality of faunal assemblages (e.g. brachiopods, conodonts) has been proved and is also supposed for trilobites by some authors. However, although the Cruziana ichnospecies result from a high specialization of their tracemakers, and therefore only a small group of trilobite species is eligible for its origin, the ichnospecies reported from Baltica occur also on other palaeocontinents and do not support the assumption of trilobite provincialism. Copyright © 2004 John Wiley & Sons, Ltd.

Paleobiology of complex trace fossils

Complex trace fossils include structurally elaborate biogenic structures such as the large, spiral forms of Zoophycos and the intricately organized graphoglyptids; compound structures consisting of connected parts that would receive different ichnotaxonomic labels if preserved in isolation; and recurrent spatial associations of different trace fossils that probably represent strong ecologic interaction. These complicated animal artefacts should not be viewed so much as preservational rarities or taxonomic puzzles, but rather as neglected sources of information on the ethologic, ecologic and evolutionary characteristics of trace producers. Trying to fit these structures into the traditional behavioral classification scheme of Seilacher is bound to fail. Many complex trace fossils appear to have been occupied for long intervals and to record re-engineering or active control of proximal habitats by the trace-producing organisms. Attempting to understand their actual biologic significance will require new descriptive and interpretive approaches. One possible descriptive approach involves making comprehensive inventories of structural elements that record particular kinds of adaptive behavior or interaction (behavioral tokens). Portraying the spatial and temporal order of tokens could be done using a kind of systems diagram (paleoethologic ‘blueprint’) that summarizes construction, operation and maintenance of complex biogenic structures. New approaches to interpretation involve viewing the structures as evidence of physiologic projection of the trace producers, or as the extended phenotypes of these organisms. A reorganized approach to the study of complex biogenic structures emphasizing biologic properties would not only lead to some very old puzzles finally being solved, but also would revitalize ichnology and forge new and productive connections to ecology and evolutionary biology.

Ichnology, Sedimentology and Paleontology of Eocene Calcareous Paleosols From a Palustrine Sequence, Argentina

Other| February 01, 2002 Ichnology, Sedimentology and Paleontology of Eocene Calcareous Paleosols From a Palustrine Sequence, Argentina RICARDO N. MELCHOR; RICARDO N. MELCHOR 1CONICET & Universidad Nacional de La Pampa, Av. Uruguay 151, 6300 Santa Rosa, La Pampa, Argentina Search for other works by this author on: GSW Google Scholar JORGE F. GENISE; JORGE F. GENISE 2CONICET & Departamento de Icnología, Museo Paleontológico “Egidio Feruglio”, Av. Fontana 140, 9100 Trelew, Chubut, Argentina Search for other works by this author on: GSW Google Scholar SERGIO E. MIQUEL SERGIO E. MIQUEL 3CONICET & Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Av. Ángel Gallardo 470, 1405 Buenos Aires, Argentina Search for other works by this author on: GSW Google Scholar PALAIOS (2002) 17 (1): 16–35. https://doi.org/10.1669/0883-1351(2002)017<0016:ISAPOE>2.0.CO;2 Article history accepted: 05 Jul 2001 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation RICARDO N. MELCHOR, JORGE F. GENISE, SERGIO E. MIQUEL; Ichnology, Sedimentology and Paleontology of Eocene Calcareous Paleosols From a Palustrine Sequence, Argentina. PALAIOS 2002;; 17 (1): 16–35. doi: https://doi.org/10.1669/0883-1351(2002)017<0016:ISAPOE>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search Abstract Integrated analysis of the ichnology, sedimentology, geochemistry, and fossil content of three trace fossil-bearing calcareous paleosols from the early Eocene Gran Salitral Formation is used to reconstruct the detailed paleoenvironmental and paleoecological setting of this insect-dominated ichnofossil association. This continental sequence, located in southwestern La Pampa province (Argentina), is composed of palustrine marls and minor lacustrine mudstones and sandstones arranged in shallowing-upward cycles. The ichnologic association is the first comprehensively described from a palustrine sequence and could be used for future comparisons with other similar assemblages. The ichnofauna is dominated by bee cells, Celliforma germanica, C. roselli, and Rosellichnus isp.; Teisseirei barattinia, an insect trace fossil that is redescribed and recorded for the first time outside its type locality; Taenidium barretti; and Skolithos linearis. The ichnologic association also includes ovoid structures, ornamented burrow fillings, and plant trace fossils (rootlets, rhizoliths, and a tree / shrub stump). Abundant freshwater (Pomacea sp.) and terrestrial gastropods (Plagiodontes spp., Bostryx sp., and Bulimulus sp.) are used to characterize the paleoenvironmental setting. The weakly developed paleosols are interpreted as Inceptisols, developed in a low-gradient lake margin periodically exposed to pedogenesis with low (probably saline) vegetation and sparse shrubs. They developed under a semi-arid and warm climate (mean annual temperature higher than 20°C). Short saline / alkaline conditions were prevalent during lake lowstands, accompanied by incipient karst development. The association of trace fossils is attributed provisionally to the Coprinisphaera ichnofacies, although its distinctive features and recurrence in time and space may deserve recognition as a separate ichnofacies. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Trace fossil associations in the Swedish Mickwitzia sandstone (Lower Cambrian): Did trilobites really hunt for worms?

The spatial and temporal associations between Cruziana, trace fossils dug by foraging trilobites, and back filled burrows made by infaunal “worms” in a Lower Cambrian sandstone are described and discussed. In three large slabs and several smaller pieces, all from the same bedding plane in the lowermost part of the Mickwitzia sandstone (File Haidar Formation) at Kinnekulle, Västergötland, Sweden, Cruziana and worm burrows coincided more frequently than would be expected by chance. Overall, however, the association was weak and independent of the size of the worm trace. In 24 out of 29 cases, the worm burrow had deformed the Cruziana, implying that the arthropod was first on the spot. No clear case of the opposite situation was found. It is concluded that for an unknown reason the infaunal worms preferentially dug in places which had been visited earlier by foraging trilobites, or, possibly, that worms and trilobites preferred to dig in the same spots independently of each other. There is no evidence from this surface that the trilobites had been searching for worms or predated on them.

Upper Triassic (Keuper) non-marine trace fossils from the Haßberge area (Franconia, south-eastern Germany)

Various trace fossils from the Hassberge Formation and the Lowenstein Formation (Middle Keuper, Upper Triassic) of the Hasberge region are described. Twenty-three different forms have been identified, 17 of which are named, includingCruziana pascens n. isp.,Lockeia cunctator n. isp., andRusophycus versans n. isp.Lockeia siliquariaJames, 1879,L. amygdaloides (Seilacher, 1953),L. triangulichnusKim, 1994, andL. elongata (Yang, 1984) are revised and synonymized under the oldest available name,L. siliquariaJames, 1879.Rusophycus eutendorfensis (Linck, 1942) andR. carbonariusDawson, 1864 are revised. The diagnosis ofPolykladichnusFursich, 1981 is emended, and a diagnosis forHelminthoidichnitesFitch, 1850 is given for the first time. Among the described ichnotaxa,Skolithos ispp.,Rusophycus carbonarius, andTaenidium barretti are the most common forms. The trace fossil association is typical of theScoyenia ichnofacies, which indicates non-marine, periodically or completely inundated environments, such as floodplains and lake margins. Two palaeoichnocoenoses are identified. One ichnocoenosis, dominated byCruziana problematica, cf.Polykladichnus isp., andSkolithos isp. B characterizes margins of trough cross-bedded sandstones. Another ichnocoenosis, dominated byRusophycus versans n. isp.,Taenidium barretti,Scoyenia gracilis andSkolithos isp. A is related to ephemeral lake deposits. Taxonomic recommendations for the use of hitherto described and figured invertebrate Keuper trace fossils from Germany are given.

High-Resolution Architecture and Paleoecology of an Active Margin, Storm-Flood Influenced Estuary, Quinault Formation (Pliocene), Washington

Other| December 01, 2000 High-Resolution Architecture and Paleoecology of an Active Margin, Storm-Flood Influenced Estuary, Quinault Formation (Pliocene), Washington KATHLEEN A. CAMPBELL; KATHLEEN A. CAMPBELL 1Department of Geology, University of Auckland, Private Bag 92019, Auckland, New Zealand Search for other works by this author on: GSW Google Scholar ELIZABETH A. NESBITT ELIZABETH A. NESBITT 2Department of Geological Sciences and Burke Museum of Natural History and Culture, Box 353010, University of Washington, Seattle, WA 98195-3010 Search for other works by this author on: GSW Google Scholar PALAIOS (2000) 15 (6): 553–579. https://doi.org/10.1669/0883-1351(2000)015<0553:HRAAPO>2.0.CO;2 Article history accepted: 08 Aug 2000 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation KATHLEEN A. CAMPBELL, ELIZABETH A. NESBITT; High-Resolution Architecture and Paleoecology of an Active Margin, Storm-Flood Influenced Estuary, Quinault Formation (Pliocene), Washington. PALAIOS 2000;; 15 (6): 553–579. doi: https://doi.org/10.1669/0883-1351(2000)015<0553:HRAAPO>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyPALAIOS Search Advanced Search Abstract An exhumed Pliocene estuarine sequence is preserved in exquisite detail in the Quinault Formation of coastal western Washington. The thick fill of the Quinault estuarine basin (∼700 m) represents a single transgressive-regressive system that was punctuated by subduction-related tectonic events, and may reflect erosion and sediment accumulation during accelerated uplift of the Olympic Mountains in the Pliocene. Sedimentation patterns in the ancient Quinault estuary were influenced strongly both by floods on the paleo-Quinault River, and by storm waves on the high-energy, open Pacific coast. Body fossils were derived from both marine and brackish faunal elements. Trace fossil suites indicate that the benthos flourished in the fluctuating physicochemical conditions of an estuary in dynamic equilibrium. An estuarine-specific trace fossil, a new ichnospecies of Psilonichnus that is attributed to burrows of the mud shrimp Upogebia pugettensis, is restricted to inlet-mouth, muddy sandstone facies. The marine-marginal marine transition is well-preserved in Quinault estuarine strata (exposed in the Point Grenville and Cape Elizabeth areas), as evidenced by: (1) distinctive sedimentologic signatures characteristic of lower shoreface, estuarine mouth, central basin, tidal creek/flat, and fluvial subenvironments; and, (2) systematic changes in trace fossil associations in the up-estuary direction, from Skolithos ichnofacies elements to a mixed Skolithos-Cruziana assemblage to Glossifungites associations with rhizome phytoburbation. Hence, Quinault strata record a classic tripartite division of an ancient estuarine system, allowing a fine-scale delineation of subenvironments in an active tectonic regime. You do not currently have access to this article.

Insect Trace Fossil Associations in Paleosols: The Coprinisphaera Ichnofacies

Fil: Genise, Jorge Fernando. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Regional de Investigaciones Cientificas y Transferencia Tecnologica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Cientificas y Transferencia Tecnologica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Cientificas y Transferencia Tecnologica de La Rioja. - Secretaria de Industria y Mineria. Servicio Geologico Minero Argentino. Centro Regional de Investigaciones Cientificas y Transferencia Tecnologica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Cientificas y Transferencia Tecnologica de La Rioja; Argentina

Palynofacies analysis of sediments from the Côte d'Ivoire-Ghana transform margin: Preliminary correlation with some regional events in the Equatorial Atlantic

Analyses of the palynofacies and sporomorph thermal alteration indices (TAI) of sediments from Ocean Drilling Program (ODP) Sites 959 to 962 in the Côte d'Ivoire-Ghana Transform Margin, West Africa were undertaken to (1) determine the source and depositional conditions of the organic matter in the sediments, (2) refine a paleobathymetric curve derived from other data for Site 959, which drilled the most continuous sedimentary sequence from Pleistocene to Albian and (3) interpret the paleothermal history of the area. Twelve types of dispersed organic matter were identified: amorphous organic matter (AOM), marine palynomorphs, algae, resins, black debris, yellow-brown fragments, black-brown fragments, cuticles, plant tissue, wood, sporomorphs and fungi. The relative abundances of these organic matter components at each site were analyzed using cluster analysis, resulting in the identification of seven palynofacies assemblages at Site 959, five each at sites 960 and 961, and four at Site 962. Amorphous organic matter (which is chiefly marine derived), black debris and wood have played the most significant role in defining palynofacies assemblages. The palynofacies assemblages show some correlation with lithologic units, sediment sources and depositional environments. Previous palynofacies studies in passive margins have demonstrated that changes in the ratio of AOM to terrestrial organic matter are related primarily to proximal-distal positions of depositional environments relative to the shoreline. However, this assumption does not always hold true for a transform margin where tectonic factors play an important role in the organic matter distribution, at least in the early stages of evolution. Lithofacies, CCD paleodepths for the North Atlantic, trace fossil association, benthic foraminifera and palynofacies data were the criteria used for reconstructing a paleobathymetric curve for Site 959. A cyclicity in the organic matter distribution of the Upper Miocene to Lower Pliocene pelagic sediments could be related to fluctuations in productivity of biosiliceous and calcareous organisms, and sedimentation rates. A drastic increase in the amount of AOM and a decrease in black debris and wood in the carbonate and clastic rocks (Lithologic Unit IV) overlying the tectonized Albian sediments (Lithologic Unit V) at Sites 959 and 960 coincide with the presence of an unconformity. Qualitative color analysis of palynomorphs was undertaken for all sites, although the main focus was on Site 959 where detailed organic geochemical data were available. At Site 959, TAI values indicate an immature stage of organic maturation (<2) down to the black claystones of Lithologic Unit III at about 918.47 mbsf. Below this, samples show an increase with depth to a moderately mature stage (>2 except for the claystone samples between 1012.52 and 1036.5 mbsf, and one limestone sample at 1043.4 mbsf), reaching peak levels of 2.58 to 3.0 in the tectonized Albian sediments below the unconformity. These TAI values show a positive correlation with the T max values derived from Rock-Eval pyrolysis data. The highest values recorded in the basal tectonized units at all the sites (Sites 960–962 have mean values between 2.25 and 3.13) may be related to high heat flow during the intracontinental to syntransform basin stage in the region.

Trace fossils from Fleckenmergel facies (Jurassic) of the Tatra Mts

The Lower-Middle Jurassic spotted marls and limestones known as the Fleckenmergel facies are the earliestbasinal sediments of Krizna succession (Fatricum domain) of the Tatra Mts. This facies, occurring in the Alpides from the Betic Range to Timor Island, belongs to the characteristic facies of the passive margins of the Tethys. Its thickness and stratigraphic extent differ from region to region. The Fleckenmergel deposits of the Tatra Mts. are characterised by the presence of high density but low diversity fodinichnia-dominated associations of trace fossils. Temporal changes in the bottom water oxygenation may be a reasonable explanation for the presence of two phases of bioturbation observed in many layers. First, the well-oxygenated marly sea bottom was colonized by an active infauna that produced a totally bioturbated ichnofabric. After a decrease in available oxygen, the bottom was successively colonized by organisms that produced burrows: Planolites, Zoophycos, Chondrites.

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

Intrastratal trace fossil zonation, Cretaceous flysch of northern California

Dissection of fine‐grained turbidites within the Franciscan complex at Trinidad Harbor reveals intrastratal zonation of biogenic structures. The pre‐depositional association comprises only three ichnotaxa (preserved in convex hyporelief) and is less diverse than the tiered post‐depositional association (comprised by at least seven ichnotaxa preserved in full relief). The latter association is dominated by Melatercichnus (n. ichnogen.). Post‐depositional trace‐makers exploited abundant plant detritus deposited with the turbidite sand. Temporal alternation of trace fossil associations resulted from the infrequent, but catastrophic, disturbance of pre‐turbidite communities and local replacement by assemblies of opportunistic organisms. Although probably short‐lived at specific sites, the post‐turbidite infauna was tiered, enabling a variety of deposit feeders to harvest phytodetritus of varied size or density simultaneously at different depths within newly deposited turbidite sand layers.

Ichnofabric Mapping and Interpretation of Jurassic Reservoir Rocks of the Norwegian North Sea

Recurrent sediment fabric and trace fossil associations in the Norwegian offshore Jurassic sequences have been interpreted by the ichnofabric concept. In the Sognefjord Formation (Oxfordian-Kimmeridgian) of the Troll Field five basic ichnofabrics were recognized and named after the dominant ichnogenus present, respectively: Helminthoida, Anconichnus, Palaeophycus, Ophiomorpha and Skolithos. These ichnofabrics developed in sediments deposited in marine environments ranging from quiescent offshore to high energy, shallow water nearshore situations. When sequence patterns of ichnofabrics were mapped within five chronostratigraphic reservoir zones of the Troll Field it was possible to recognize both how the frequency of a given ichnofabric may change in time in a restricted area or may change in its areal distribution in a restricted time interval. Such maps have been integrated with lithofacies maps and dip-meter studies in cored sequence to produce quantitative base maps for computerized reservoir models. The maps can also be used as a powerful tool for facies predictions.

Discontinuity surfaces in the Lower Cretaceous of the high Andes (Mendoza, Argentina): Trace fossils and environmental implications

The paleoecologic and paleoenvironmental significance of trace fossils related to discontinuity surfaces in the Lower Cretaceous marine deposits of the Aconcagua area are analysed here. Carbonate-evaporite shoaling-upward cycles, developed by high organic production in a shallow hypersaline restricted environment, make up the section. Two types of cycles are defined, being mainly distinguished by their subtidal unit. Cycle I begins with a highly dolomitized lower subtidal unit (Facies A), followed upward by an intensely bioturbated upper subtidal unit (Facies B). The nodular packstone facies (B 1) is capped by a discontinuity surface (firmground or hardground) and occasionally overlain by an oystreid bed (Facies C). Cycle II is characterized by a pelletoidal subtidal unit (Facies B 2) with an abnormal salinity impoverished fauna. Both cycles end with intertidal to supratidal evaporite deposits (Facies D and E, respectively). Attention is particularly focused on cycle I due to its ichologic content. The mode of preservation and the distribution of trace fossils in nodular packstone facies are controlled by original substrate consolidation. Thalassinoides paradoxicus (pre-omission suite) represents colonization in a soft bottom, while Thalassinoides suevicus (omission suite pre-lithification) is apparently restricted to firm substrates. When consolidation processes are interrupted early, only an embryonic hard-ground that represents a minor halt in sedimentation was developed. Sometimes, consolidation processes continued leading to an intraformational hardground. Colonization by Trypanites solitarius (omission suite post-lithification) and Exogyra-like oystreids possibly characterizes hard substrate stage. When two discontinuity surfaces follow closely, a post-omission suite may be defined in relation to the lower cemented surface. As trace fossils are so closely related to changes in the degree of bottom lithification, they prove to be very useful as indicators of substrate evolution. The presence of discontinuity surfaces, evidenced by trace fossil association, suggests changes of sedimentary rate and environmental conditions that should be taken into account in future studies seeking to erect depositional models for these Cretaceous deposits.

Lithofacies relationships in a late Quaternary gravel and loess fan delta complex, New Zealand

Coastal cliffs up to 70 m high provide a nearly continuous section along depositional strike of a small Quaternary fan delta complex south of Conway Flat, north Canterbury, New Zealand. A gentle northeasterly dip permits observation of all facies of the complex, from the offshore prodelta to an emergent interdeltaic embayment facies showing beds with abundant rhizoliths, and in situ roots and stumps of large 8000-yr old podocarp trees. Coarse gravels derived from the Hawkeswood Range (650 m high), 5 km west of the sea cliffs, were transporte largely by debris flow processes into the Pacific Ocean towards the Conway Trough (800 m deep), 10 km to the east of the cliffs. Narrow (up to 1 km wide) Gilbert-type gravel deltas built elongate lobes into channels created by slumping and sediment gravity flows which deeply incised muddy prodelta deposits. Between the fan deltas, embayment facies are dominated by loessial sediment with sand:silt:clay ratios of about 7:68:25; thin sand beds are present. Prodelta sediments also are composed largely of redeposited loess. Loessial sediment came from the distant glaciated Southern Alps, transported both in air and along major rivers that produced broad plumes of suspended sediment in the ocean which were carried northwards by the prevailing longshore currents. Laterally adjoining the fan delta lobes, on several wave-cut benches within them, and scattered in the distal embayment facies are winnowed wave-sorted bars of fine gravel and sand. The proximal embayment facies includes sparse, poorly sorted, gravelly storm bars, gravelly fluvial crevasse deposits, and shallow broad tidal channel filled with loessial sediment and fine sand. Well-displayed trace fossils permit close correlation of ichnofacies with lithofacies and extend paleoenvironmental interpretation in this young deposit. Trace fossil associations and interpretations are described in the following paper in this journal.

Trace fossils and paleoenvironmental control of ichnofacies in a late Quaternary gravel and loess fan delta complex, New Zealand

Remarkably well-preserved trace fossil assemblages of a small, Late Quaternary (> 3000 yr B.P.) fan delta complex are exposed in sea cliffs south of Conway Flat, North Canterbury, New Zealand. Marine trace fossils are common and well-preserved in the bar, embayment and prodelta facies, but deltaic distributary facies contain no trace fossils at all. The preceding paper in this journal ( Lewis and Ekdale, 1991) describes the lithofacies and their paleoenvironmental setting in this fan delta complex. Common trace fossils include the ichnogenera Anconichnus, Arenicolites, Asterosoma, Cylindrichnus, Diplocraterion, Gordia, Helminthoida, Ophiomorpha, Piscichnus, Planolites and Skolithos. One new ichnogenus ( Arborichnus), two new ichnospecies ( Arborichnus sparsus and Diplocraterion asymmetrium), and three informal varieties of Diplocraterion parallelum (var. lingum, arcum and quadrum) are introduced. Local ichnofacies include (a) low-divsity Anconichnus horizontalis Ichnofacies of densely packed burrows of deposit-feeding animals in shallow-marine, fine-grained sediment of bar and distal embayment facies, (b) high-diversity Diplocraterion parallelum var. lingum Ichnofacies of burrows of suspension-feeding animals in interbedded mud, clean sand and gravelly sand of the bar facies, (c) moderate-diversity Diplocraterion parallelum var. quadrum Ichnofacies in interbedded mud and sand of distal embayment facies, and (d) low-diversity Planolites montanus Ichnofacies of deformed burrows in bioturbated mud of the prodelta facies. In addition, sparse animal escape structures (fugichnia) occur locally in interbedded sand and gravel of the bar facies. The trace fossil associations of the Conway Flat fan delta complex are unusual in their excellent state of preservation, and many trace fossils are exposed in full-three-dimensional relief. Because of their very young age, they must reflect similar associations of biogenic sedimentary structures in modern deltaic settings that are as yet undescribed. This report appears to be the first documentation of a fully marine trace fossil assemblage in loessial sediments.

Study on lithofacies paleogeography of Zhungeer coal field and its methodology in Inner Mongolia of China

The Zhungeer coal field is located in the eastern part of Zhungeer, Inner Mongolia. It is a Permo-Carboniferous coal field, about 1730 km 2, and trends nearly south-north. The coal seams are thick, mineable, and of excellent quality. It will be one of the most important coal fields in China. As a result of lithofacies research and paleogeographical reconstruction of the Zhungeer coal field, some insights ar realized on the barier-island system of the epeiric sea in a coal-bearing sequence, the coal-forming environment of marine facies, the event deposits in coal-bearing sequences, and the method of preparing a lithofacies paleogeographical map in coal-bearing basins. The Shanxi Formation of Early Permian age in the Zhungeer coal field belong to the deltaic-fluvial system. In the author's research, however, the Benxi and Taiyuan Formations of Carboniferous age belong to the mutual system of barrier island-platform of the epeiric sea. Because of the transgression and regression of the epeiric sea, the alternative paleogeographical pattern of the barrier island and the lagoon-tidal flat are repeated many times in the same place. The platforms are located outside the barrier-island system. Along with the transgression and regressions, the terrigenous fragmental deposits of the are extensively mixed in space and time. There are two different types of coal-forming environments that also have two different features of coal quality and distribution in this coal field. The coal seams of the Shanxi formation are unevenly distributed. Coals with lower sulfur content are formed in the peat swamps of the deltaic-fluvial system. The author's research, however, shows that the coal seams of the Benxi and Taiyuan Formation are formed in coal-forming environments of the marine facies. The author calls this type of coal-forming environment “peat flats” (Liu Huanjie, 1982) defined as follows: Mangroves or tidal plants having a similar bioecology to mangroves could grow in the intertidal flats and some supertidal flats of the tropical and subtropical zones and could be formed into peats deposits over a large area; such direct coal-forming environments in the tidal flats are called “pet flats” including intertidal flats, supertidal flats, some subtidal flats, adn tidal channels. It can be divided into differnet types of peat flats such as: lagoon-peat flats, back barrier-peat flats, tidal delta-peat flats, carbonate platforms-peat flats, and estuary-peat flats distributed in the mutual system of the barrier island-platform. The coal seems formed in peat flats are distributed widely and stably and area easily contrasted; the thickness of oal seams changes greatly and their divergences are notable in some areas. Where organic sulfur is higher, it may be related to the presence of tidal plants. The event deposits, storm event and volcanic event deposits, are widely istributed in the coal-bearing sequence of the Benxi and Taiyuan Formations in this coal field. The main markings of storm deposits are as follows: the hummocks under the surface of the erosion, the storm detention bed, and hummock cross-bedding, the sequence association, and the trace-fossil association. The tempestites, according to the author's recent study, can be divided into carbonates and terrigenous clastics. The main types are as follows: the tempestite of the backflow type including the carbonate tempestite of distal, proximal, and proximal shallow water; the carbonate tempestite of stirring type; proximal storm sandstone type; and the gravel-fragment mudstone type. The volcanic event deposits occur in the middle and upper parts of the Taiyuan Formation. The main types are the clastic-fragment tuff, tuff lava, and tuff. The volcanic deposits can be divided into those that accumulated under water and those that accumulated above water. There are three to four seams of clastic fragment tuff formed in the lagoon between the No. 4 and No. 5 limestones. The thickness of each seam of clastic-fragment tuff is 5–10 cm and distributed very steadily. A large number of complete brachiopod fossils were often developed. This is a disaster induced from a volcanic event. In this research, the methodology utilized to reconstruct the lithofacies paleogeography of the Zhungeer coal field follows. The first is that the new theory of sedimentology is guided by the quantitative environmental analysis of the single section in the field; the second is from point to line, from line to face, and from face to three dimensions, field observation is combined with laboratory analysis; the third is based on the lithologic and lithofacies section from which single-factor basic maps are drawn; the fourth is using the sedimentary facies ratio to draw up the quantitative lithofacies-paleogeographical maps and from these to reconstruct the lithofacies-paleogeography of the coal basin and to determine the distribution law of coal seams. We are grateful to the Coal-Field Geological and Exploration Company of

Trace fossil associations related to facies of an upper Ordovician low wave energy shoreface and shelf, Oslo‐Asker district, Norway

Three trace fossil associations have been identified from facies interpreted as low wave energy upper, middle and lower shoreface deposits, transitional shoreface/shelf deposits and open epicontinental shelf deposits. These were developed in pre-regressive, regressive and transgressive phases associated with eustatic sea level changes caused by the upper Ordovician glaciation. The three associations are the Skolithos-Diplocraterion association, the Diplichnites-Phycodes association and the Thalassinoides association. The Skolithos-Diplocraterion association inhabited upper, middle and lower shoreface environments, the Diplichnites-Phycodes association a lowermost shoreface environment and the Thalassinoides association inhabited offshore epicontinental shelf environmcnts. The Skolithos-Diplocraferion and Diplichnites-Phycodes associations bear strong affinities with previously described Skolithos ichnofacies assemblages (indicating shoreline environments) and the Cruziana ichnofacies forms (indicating shallow water environments down to wave base) respectively. The Thalassinoides assemblage, however, closely compares with assemblages described from Mesozoic epicontinental shelf sequences. Trace fossil diversity achieves a maximum in the lowermost shoreface environment and reduces in deeper water and shallower water environments. This accords with diversity patterns identified in analogous Jurassic epicontinental palaeonvironments. The stratigraphic distribution of some trace fossil association boundaries accords with those of contemporary body fossil associations. However, several body fossil associations are included within the volume of distribution of a single trace fossil assemblage. □Trace fossil association, shoreface and shelf, Oslo district, upper Ordovician.