Palaeophycus Tubularis Research Articles

Are aeolian ichnofacies distinctive and useful? An analysis of trace fossil assemblages from Cretaceous aeolian facies in northern Patagonia, Argentina

In this paper, Cretaceous trace fossil assemblages are reported from aeolian facies within four units from Patagonia, Argentina, to evaluate the usefulness of the aeolian ichnofacies concept. From oldest to youngest, studied units comprise the Agrio (Valanginian-Hauterivian), Cerro Barcino (Aptian-Cenomanian), Candeleros (Cenomanian), and Allen (Campanian-Maastrichtian) formations. Twenty one ichnotaxa were recorded, including ten of invertebrate origin (Archaeonassa fossulata, Arenicolites tenuis, Beaconites isp., Digitichnus laminatus, Edaphichnium lumbricatum, cf. Octopodichnus isp., Palaeophycus tubularis, Skolithos linearis, Taenidium barretti, and an unidentified arthropod trackway), seven tetrapod footprints and burrows (Avipeda isp., Brasilichnium isp., cf. Chelonipus isp., Reniformichnus katikatii, two types of indeterminate footprints, and burrow fills) and four rhizolith types. Entradichnus meniscus (formerly used as eponym of an aeolian ichnofacies) is considered a junior synonym of Taenidium barretti. Common ichnotaxa in aeolian and fluvial sequences like Taenidium barretti, Skolithos linearis and Palaeophycus tubularis are facies-crossing ichnotaxa and should not be used to distinguish ichnofacies. Trace fossil assemblages and ichnofabrics from aeolian dune, dry interdune and wet interdune facies are interpreted in terms of the potential producers and their palaeoecological and palaeoenvironmental constraints. This procedure is more informative than the ichnofacies approach in aeolian deposits. Based on a literature review of 32 examples of trace fossil assemblages from Cretaceous aeolian sequences worldwide, we conclude that the most distinctive ichnotaxa occur in aeolian dunes, including Brasilichnium, Farlowichnus, lacertoid footprints, Octopodichnus and Paleohelcura. It is recommended to abandon the usage of the Chelichnus, Entradichnus and Entradichnus-Octopodichnus ichnofacies, which are poorly defined in terms of recurrence and environmental significance or based on uncharacteristic or unavailable ichnotaxa. We propose a new definition of the Octopodichnus ichnofacies, diagnosed by the presence of subequant tetrapod footprints in quadrupedal trackways and/or selected arachnid /insect trackways. This ichnofacies is a taphofacies recorded from the Permian to the Cretaceous, and probably extends to the Cenozoic.

Storm deposits and trace fossils of Xinji Formation (Cambrian Series 2) in the southern margin of North China Plate

The Xinji Formation (Cambrian Series 2) in the southern margin of the North China Plate developed typical siliciclastic storm deposits and abundant trace fossils. These deposits are characterized by essential indicators, such as erosional surfaces, lag deposits, blocky beddings, hummocky cross stratifications, horizontal or wavy beddings. Storm deposits in the study area are dominated by the development of hummocky cross stratifications, which is categorized into five storm deposit types based on the arrangement of different sedimentary units in the profile. These five types of storm deposits from I to V show the transition from proximal storm deposits to distal storm deposits, the gradual weakening of storm intensity, and the associated growth of quiescent intervals. The trace fossils are mainly developed in the sandstone-mudstone interbeds between storm events and include 14 ichnospecies in 11 ichnogenera: Didymaulichnus isp., Gordia marina, Helminthopsis tenuis, Oldhamia radiata, Palaeophycus striatus, Palaeophycus tubularis, Phycodes isp., Planolites beverleyensis, Planolites montanus, Planolites punctatus, Skolithos isp., Taenidium isp., Torrowangea rosei, Treptichnus pedum. By analyzing the ichnological index (burrow size, BPBI, ichnodiversity and ichnodisparity) from different storm deposits, it can be seen that from storm deposit type I to storm deposit type V, the ichnological index shows an increasing trend. Combined with the relationship between storm deposits and trace fossils, it is inferred that differences in storm intensity result in different colonization windows, and thus variations in ichnological index of preserved trace fossils. Based on the characteristics of storm deposits and distribution of trace fossils, the preservation forms of trace fossils under storm influence are explored.

Facies and trace fossils of the Upper Cretaceous Sillakudi Formation (Cauvery Basin, S. India) and their palaeoenvironmental significance

The Sillakudi Formation is a sandstone-dominated succession bounded by unconformities. It represents the oldest unit of the Ariyalur Group deposited during the Campanian under fully established passive margin depositional conditions. The present study is an attempt to interpret the depositional palaeoenvironment of Sillakudi Formation based on its trace fossil content, supported by sedimentological evidences. Detailed sedimentological and ichnological observations were undertaken in multiple traverses and spot locations across the Sillakudi Formation. The Sillakudi Formation is subdivided into four facies associations, each represented by a distinct ichnology and environment of deposition. Unit 1 comprises conglomerates grading upwards into pebbly sandstones almost devoid of trace fossils except a few Planolites isp. indicating a high-energy foreshore-to-shoreface environment. Unit 2 consists of glauconitic sandstones with Ophiomorpha nodosa, O. annulata, Thalassinoides isp. and Skolithos linearis, belonging to the Skolithos ichnofacies indicating deposition in shoreface to offshore transition environments. Unit 3 comprises pebbly to very coarse-grained massive sandstones, characterised by an almost monospecific Skolithos ichnofacies indicating rapid colonisation of beds in a delta-front associated debris flows and calcareous sandstones alternating with claystones containing a diverse Cruziana ichnofacies with an ichnoassemblage comprising of Trichichnus isp., Scolicia prisca var. laminites, S. ?prisca, S. vertebralis, Palaeophycus tubularis, Planolites beverleyensis, P. montanus, Taenidium isp., Thalassinoides suevicus, Ophiomorpha isp., Chondrites isp. and Phycodes isp., pointing towards deposition in calmer, possibly dysoxic outer shelf prodeltaic environments. Unit 4 has pebbly to gritty cross-bedded sandstones exhibiting the development of networks of Thalassinoides isp. and Ophiomorpha isp., indicating shallow sub-tidal to intertidal conditions of deposition. The overall succession is interpreted to show initial deepening followed by shallowing.

A new vertebrate ichnological association sheds light on the small metatherian record of the Middle Miocene in South America

Vertebrate ichnological associations recorded in Middle Miocene successions were unknown in South America. During that time, South America was isolated from other continents and had a unique endemic fauna and flora. The lower Vinchina succession occurred between 15.6 and 12.7 Ma and records the footprints of highly specialized mammals, reptiles, and birds for the first time. To identify all footprint producers, we focused on anatomical traits of the appendicular skeleton represented on the footprints together with body size estimations of the producers as body mass and the apparent trunk length (GAD). Carnivoripeda sudamericana nov. isp. reveals a weasel-like producer of ∼1 kg and a trunk length of 19–26 cm most likely attributed to metatherian carnivores (Sparassodonta). They represent the oldest carnivore footprints in South America. Small bipedal rodent-like mammals of ∼280 g using a jumping gait (Morphotype A) are interpreted as produced by highly specialized South American marsupials, argyrolagids, whose footprints were unknown until now. Other mammalian footprints recorded are Tacheria troyana most likely produced by dinomyid caviomorph rodents. They represent animals of ∼16 kg and a trunk length of 48–55 cm, like living dinomyids. Subcircular to oval structures (Morphotype B) seems to be produced by medium-sized ungulates, while stepping in cohesive and plastic soupy sediments. cf. Chelonipus torquatus suggests small freshwater turtles (Chelidae or Podocnemididae), of ∼400 g consistent with a trackmaker of carapace size of ∼9 cm. Aviadactyla vialovi was most likely produced by a small shorebird (Scopolacidae) of ∼40 g. All footprints are preserved on crevasse splay deposits of anastomosing fluvial systems together with meniscate feeding (Taenidium barretti) and simple dwelling trace fossils (Palaeophycus tubularis) produced by insects and are an example of the Scoyenia Ichnofacies.

Trace fossils from Furnas formation (Paraná Basin) reveal a marine depositional environment

Trace fossils are important biogenic signatures in sedimentary environments because they indicate the paleoecologic controls during deposition. In some cases, trace fossils are the unique preserved biologic evidence, allowing to infer paleoenvironments in controversial stratigraphic units. This is the case of Furnas Formation from Paraná Basin, Brazil. This unit was widely interpreted as fluvial-generated up to 1990's, but facies association analysis and the ichnologic data have been used as tools to suggest a marine origin for the unit. However, some recent studies have been ignored that information and continuous to interpret Furnas Formation as a fluvial-generated unit. In this study we analyzed some outcrops at northeast of the Ponta Grossa Arch aiming to infer depositional processes and paleoenvironments for basal and intermediated units of Furnas Formation (Lower Silurian). Nine ichnotaxa (Cruziana, Didymaulichnus lyelli, Didymauliponomos rowei, Heimdallia chatwini, Palaeophycus tubularis, Rusophycus, Skolithos, Taenidium dieslingi, and Thalassinoides) expressing proximal and depauperate Cruziana ichnofacies were reported for the studied outcrops, corroborating the shallow marine paleoenvironment inferred for the unit.

Ichnodiversity and facies of Triassic red beds in the Irohalene area (Argana Basin, Western High Atlas, Morocco): implications for palaeoenvironment

ABSTRACT From Middle-Late Triassic continental deposits of the Timezgadiouine Formation (Argana Basin, Morocco), 17 lithofacies are identified, with alluvial fan, fluvial, floodplain and lacustrine associations. Invertebrate traces include Archaeonassa fossulata, Arenicolites isp., cf. Arenituba, Beaconites isp., cf. Camborygma, Cruziana problematica, Diplocraterion isp., Fuersichnus isp., Helminthoidichnites tenuis, Lockeia isp., Palaeophycus striatus, Palaeophycus tubularis, Planolites isp., Rusophycus carbonarius, Scoyenia gracilis, Skolithos isp., Spongeliomorpha carlsbergi, Taenidium isp. and Taenidium barretti. Additionally, rhizoliths were observed. Six ichnoassemblages were distinguished: overbank facies with (1) Rhizolith ichnoassemblage in a low-energy floodplain environment and (2) Scoyenia-Palaeophycus ichnoassemblage in crevasse splay deposits. The fluvial ichnoassociation is of moderate ichnodiversity consisting of the following assemblages: (3) Arenicolites, developed under higher flow velocities of active channels, (4) Taenidium-Scoyenia, formed by the colonisation of inactive channels, (5) Arenicolites-horizontal meniscate burrows, reflecting a rapid transition between active and abandoned channels and (6) Lockeia-vertebrate footprint, formed in littoral lakes. The Aglegal and Irohalene members indicate climatic shifts between arid dry, semiarid and subhumid in a dryland river environment. The sudden onset and the high frequency of lacustrine deposits in the lower Irohalene Member point to a rapid climate change from dry to intermittent wet and dry. This change is discussed in terms of the Carnian Pluvial Event.

Ichnological study of the Palaeogene sedimentary succession of Botsa, Kohima District, Nagaland, India

The Palaeogene sedimentary succession of the Inner Fold Belt, exposed in Botsa, Kohima District of Nagaland, contains a rich ichnofossil assemblage, with trace fossils being common in the lower part. The present investigation was aimed at establishing the palaeoenvironmental conditions of the Palaeogene sedimentary rocks of the study area. Based on the various parameters, two lithofacies; siltstone‐sandstone and mudstone facies have been identified. The trace fossils recorded comprise 10 ichnogenera representing 12 ichnospecies namely, Chondrites intricatus, Diplocraterion isp., Lockeia siliquaria, Monocraterion isp., Nereites isp., Palaeophycus tubularis, Planolites beverleyensis, Scolicia plana, Scolicia prisca, Skolithos verticalis, Thalassinoides horizontalis and Thalassinoides suevicus. Based on integrated lithofacies and trace fossils analysis, an upper shoreface to offshore transition shallow marine palaeoenvironment with fluctuating energy conditions is envisaged for the Palaeogene sedimentary rocks of the study area.

Shallow marine trace-fossils from the Middle Miocene of the Tebessa Basin (NE Algeria) and their paleoenvironmental implications

The northeastern part of Algeria is characterized by Meso–Cenozoic fossiliferous deposits. All the previous studies have been focused on invertebrate and vertebrate body fossils from this region. In the present paper we provide the first ichnological study from the region of Ouenza, Tebessa Wilaya (northeastern Algeria). An ichnoassemblage composed of eight ichnotaxa, namely cf. Archaeonassa isp., Arenicolites isp., Diplocraterion isp., Helminthopsis isp., Palaeophycus tubularis, Skolithoscf. linearis, cf. Taenidium isp., and Thalassinoides isp., reported from the lower Langhian (Middle Miocene) of Aïn Sidi Salah locality (Tebessa Basin) is discussed. These trace-fossils belong to the Skolithos and proximal Cruziana ichnofacies indicating deposition within a shallow marine (littoral). The large size of Thalassinoides suggests well-oxygenated setting, under moderate- to high-energy conditions, with occasional storm events. Keywords: trace-fossils, paleoenvironments, shallow marine, Middle Miocene, Tebessa.

Ichnofauna from the Silurian–Devonian beds of the Parnaíba Basin at Poti River Canyon (Piauí State, NE Brazil)

This paper characterizes the ichnology and sedimentology of the Lower Paleozoic Parnaíba Basin beds exposed in the Poti River Canyon (Piauí State, NE Brazil) and discusses the paleoenvironmental significance of the ichnofauna. The sedimentary succession represents the Silurian–Devonian infill of the Parnaíba Basin and comprises mouth bar deposits (Ipu Formation) and shoreface deposits (Tianguá and Pimenteira formations). The Silurian ichnofauna is represented by Heimdallia isp. in the topmost beds of the Ipu Formation, and Musculopodus sedentarius, Didymaulichnus lyelli, Didymaulyponomos rowei, Diplocraterion isp., Heimdallia isp., Lockeia siliquaria, Nereites irregularis, Palaeophycus tubularis, and Thalassinoides cf. horizontalis in the Tianguá Formation. The Devonian ichnofauna occurs in the Pimenteira Formation and is represented by Beaconites antarcticus, Bifungites munizi, Bifungites crucifomis, Nereites isp., and Rhizocorallium commune. Horizontal burrows and furrows occupying shallow and middle tiers dominate the ichnofauna, suggesting proximal expressions of the Cruziana ichnofacies. The predominance of sandy, unbioturbated, storm-generated beds in the shoreface deposits indicates a high frequency of storm surges in shallower areas of the shelf, which often inhibited or frequently erased most of the post-event substrate colonization record. Thus, the trace fossil in the analyzed succession represents substrate colonization below the low-tide base and above the storm wave base in shoreface settings. The presence of Musculopodus sedentarius in this assemblage expands the geographic and temporal record of the ichnogenus. The similar composition of the trace fossil assemblage with other Lower Paleozoic ichnofaunas reinforces ichnostratigraphic correlations represented in coeval Gondwanan units.

First discovery of Mississippian trace fossils in the Świebodzice Unit from the Witoszów region (SW Poland)

Abundant and moderately diverse trace fossil assemblage have been discovered for the first time in mudstones of the Pogorzala Formation from the Witoszow region, SW Poland. Fifteen ichnospecies including fourteen ichnogenera are described. The ichnofauna is dominated by Dictyodora liebeana and contains numerous Palaeophycus tubularis , rarer Archaeonassa fossulata , Archaeonassa isp., Chondrites cf. intricatus , Curvolithus simplex , Diplopodichnus biformis , Lockeia isp., ? Lophoctenium isp., Nereites isp., Phycosiphon isp., Protovirgularia isp., ? Psammichnites isp., Taenidium isp. and one ichnospecies of fish swimming trails, Undichna cf. britannica. Some other structures (wave ripples influenced by microbial mats and zigzag structures) also occur. The trace fossil assemblages differ in various exposures, but three of them are similar and display the Dictyodora liebeana ichnoassemblage. It is represented mostly by the ethological categories fodinichnia and repichnia, with fewer pascichnia, domichnia and cubichnia. This new data from the Świebodzice Unit sheds light on the palaeontology, age and paleoenvironment of the Pogorzala Formation. The occurrence of D. liebeana and U . cf. britannica indicates the Mississippian age of most mudstones studied, formerly considered Upper Devonian. The trace fossil assemblage belongs to the non-standard Nereites ichnofacies, without graphoglyptids. The lithological features of mudstones, trace fossil assemblage and poverty of macrofauna, testify to their deposition in a deeper sedimentation zone below storm wave base, most likely in dysaerobic, pro-delta conditions. This study suggests that rocks containing D. liebeana may form a correlative horizon in the Świebodzice Unit.

First description of the ichnofauna from the type locality of the Famennian stage (Late Devonian) of S Belgium

Ichnofossils from the type locality of the Famennian are here described and figured for the first time. The siliciclastic supratidal alluvial to proximal subtidal deposits of S Belgium yield a diverse ichnofauna composed of Arenicolites ispp. (two morphotypes), Chondrites intricatus, Diplocraterion isp., Dolopichnus gulosus, Gordia marina, Helminthopsis isp., Lockeia cordata, L. siliquaria, Palaeophycus tubularis, P. sulcatus, Planolites isp., Protovirgularia obliterata, P. cf. rugosa, P. isp. and Psammichnites implexus. As a whole, these 16 ichnospecies and 11 ichnogenera form the typical assemblage of the Cruziana ichnofacies where Palaeophycus is largely dominant. However, the Belgian Famennian displays a large range of lithofacies corresponding to various environments in which distinct ichnofossil assemblages are identified. Arenicolites isp. collected from sabkha-type primary dolomite indicates the probable colonisation of hypersaline environment by Arenicolites tracemakers as early as the Late Devonian. The type material of Crossochorda marioni Dewalque, 1881 is revised and attributed to Protovirgularia obliterata and P. cf. rugosa.

First evidence of rooting lycopsids preserved as imprints and trace fossils from the Silves Sandstone (Upper Triassic, eastern Algarve, South Portugal)

Rooting lycopsids, preserved as imprints on the Upper Triassic Silves Sandstone in the Eastern Algarve region (South Portugal), are recorded for the first time in this area. The Silves Sandstone is composed of the characteristic dark red sandstone and conglomerates of this formation and contains all the studied imprints. These have a quadrate or pseudohexagonal outline corresponding to the departure of roots placed in four to six roughly symmetrical points around the stem bases. Two generations of plants are observed, including the imprints of seedings. Palaeoenvironmental conditions for the lower unit have been interpreted as a shallow lagoon or stationary bodies of water in a swap-like environment subjected to sporadic current activity. This would have uprooted stems and ripped off the leaves. The upper unit would correspond to a fluvial environment with the establishment of an inundated floodplain with periodic subaerial exposure; this is where root imprints, shallow vertebrate (Rhynchosauroides isp.) and invertebrate trace fossils (Cochlichnus anguineus, Vagorinchus cf. anyao, Palaeophycus tubularis, Taenidium isp., Scoicia isp.), tetrapod footprints and raindrop imprints were recorded. Lycopsids maw have colonized these marshy areas in between wet (occasional flash floods) and drier episodes. Uprooting of the stems was probably caused by sudden and strong mass flow produced during intervals of heavy rain

Ichnology of the Middle Jurassic Deposits of NE Iran: Depositional Environment Interpretation

The Kopet Dagh Basin of northeast Iran formed in the Neotethys Ocean after the closure of Paleotethys in the south of Turan plate. A thick sequence of Jurassic to Miocene sediments has been deposited in this basin without any major break. The siliciclastic Kashafrud Formation (Middle Jurassic), overlying unconformably on Triassic rocks and ultrabasic rocks of turbidite and fluvio-deltaic facies, consists of sandstone, shale and conglomerate. Trace-fossil assemblages are presented in some units with different environments. The most important ichnofossils in this formation are Skolithos, Palaeophycus tubularis, Belorhaphe, Taenidium, Planoloites beverleyensis, Thalassinoides suevicus, Conichnus, Psilonichnus, Lophoctenium, Palaeophycus striatus, Rhizocorallium jenense and Scolicia.. It is interpreted, based on identified ichnofossils, the starat may have been deposited in fluvio-deltaic and deep water (turbidity conditions) environment.

Ordovician trace fossils from southern Jordan with particular consideration to the Cruziana rugosa group: Taxonomy, stratigraphy and trans-regional correlation throughout the Middle East and northern Africa

First detailed palaeoichnological research is presented from all the Ordovician formations and members of the Southern Desert of Jordan. The exclusively siliciclastic succession is of fluvial, fluvial-deltaic and fully marine origin and develops continuously from Cambrian strata until late Hirnantian glacial deposits. The ichnofauna occurs on large outcrop surfaces and is quite rich and of high diversity. Based on numerous taxonomic identifications from the excellently preserved material of various stratigraphic levels a biostratigraphic determination of the sequence is concluded as late Early to early Late Ordovician. Twenty-four ichnotaxa, two morphotypes and fifteen ichnogenera within five ethological groups based on the categories of architectural designs were identified. (1) horizontal burrows and trails (arthropod traces): Cruziana rugosa, C. furcifera, C. goldfussi, C. rouaulti, C. almadenensis, C. isp., Diplichnites cf. D. gouldi, D. morphotype A, D. morphotype B, Monomorphichnus cf. lineatus, cf. Monomorphichnus, Rusophycus didymus, R. aff. petraeus, ?R. aff. almadenensis; (2) vertical burrows: Arenicolites isp., Monocraterion isp., Rosselia socialis, Skolithos linearis; (3) plug-shaped burrows: Bergaueria perata, B. sucta; (4) horizontal branched burrows: Treptichnus cf. T. pedum; (5) horizontal burrows and trails: Gyrochorte isp., Palaeophycus tubularis, Planolites beverleyensis, Psammichnites gigas, Zoophycos isp. Whereas the ichnofauna of the Early Ordovician upper Disi Formation (Fm.) is dominated by cruzianid (C. rugosa group) and diplichnid arthopod traces (“trilobite highways”), the late Middle to early Late Ordovician Dubaydib Fm. contains distinctly smaller, nearly monoichnospecific, but completely surface covering arthropod tracks (C. almadenensis). In places, an amazing monospecific mass occurrence (Skolithos piperock ichnofabric) points to very special palaeoecological conditions during the deposition of the lower Dubaydib Fm. Ichnoassociations of the lower part of the Mudawwara Fm. (middle Late Ordovician) indicate a primarily shallow environment (e.g., Zoophycos isp.). Based on the trace fossil content and lithofacial characteristics, a correlation with North African regions is possible. So, the upper part of the Disi Fm. and the lower part of the Umm Sahm Fm. From Jordan is correlated with the Early Ordovician strata from southeastern Libya by the occurrence of C. goldfussi and C. furcifera. Additional correlations are possible by the shared occurrence of C. rouaulti with western Egypt, Sudan and western Libya. Within the Middle East (Jordan, Saudi Arabia, United Arab Emirates, Iran and Turkey), similar trace fossil assemblages composed of the C. rugosa group and related traces as well as common lithofacies characteristics point to closer palaeogeographic vicinity on a connected shallow shelf region along the costal margin of the Gondwana palaeocontinent.

Ichnological Significance of Upper Disang Formation and Lower Barail Formation (Late Eocene to Early Oligocene) of Nagaland, Northeast India, in the Indo-Myanmar Ranges

ABSTRACT The Upper Disang-Lower Barail Transition Sequences of Nagaland in northeast India, Indo-Myanmar Ranges (IMR) are found to preserve reasonably diverse biological sedimentary structures. Three ichnofacies were observed, Skolithos ichnofacies consisting of Bergaueria hemispherica, Gyrochorte comosa, Ophiomorpha nodosa, Skolithos linearis and Thalassinoides paradoxicus; Cruziana ichnofacies – Curvolithus simplex, Scolicia plana, Scolicia strozzii, Scolicia vertebralis, Treptichnus pedum, Taenidium diesingi and Palaeophycus tubularis; and Nereites ichnofacies – Chondrites targionii and Paleomeandron elegans. Presence of Skolithos and Cruziana ichnofacies suggest well oxidising, substrate rich depositional environment in the foreshoreface to offshore setting in general; and an overall possible fluctuation in the depositional bathymetry which is supported by the presence of Nereites ichnofacies in horizons alternating with Skolithos and Cruziana ichnofacies. The depositional system is proposed to be proximal to distal hyperpycnal-delta-fed turbidite system. Observation of sand spherules also suggests possibility of shoreline as one of the depositional environments.

Ichnology of prodeltaic hyperpycnite–turbidite channel complexes and lobes from the Upper Cretaceous Prairie Canyon Member of the Mancos Shale, Book Cliffs, Utah, USA

AbstractThe Upper Cretaceous Prairie Canyon Member of the Mancos Shale, Book Cliffs, Utah, contain outstanding examples of prodeltaic turbidity and hyperpycnal flow deposits. Sandstone‐rich, heterolithic and mudstone‐rich channel fills occur near the north‐west entrance to Tusher Canyon, Gunnison Butte and Bootlegger Wash. Mudstone‐rich and heterolithic‐rich hyperpycnal channel deposits are mostly unbioturbated, locally displaying a few specimens of Phycosiphon incertum, Protovirgularia dichotoma, Rosselia socialis, Schaubcylindrichnus coronus and Palaeophycus tubularis. Sandstone‐rich channel deposits consist of wave‐reworked turbidites and hyperpycnites, containing Helminthoidichnites tenuis, Lockeia siliquaria, Phycodes isp., Phycosiphon incertum, Protovirgularia dichotoma, Rosselia socialis, Skolithos linearis and Fugichnia. Scolicia isp. and Chondrites isp. occur locally. Strata along the south‐west entrance of Tusher Canyon record deposition in a prodelta turbidite lobe, but far from its axis. With the exception of a few specimens of Ophiomorpha isp., bioturbation is restricted to the top of the succession, where Curvolithus simplex, Gyrochorte comosa, Lockeia siliquaria, Palaeophycus tubularis and Ptychoplasma excelsum occur. Strata at Hatch Mesa record deposition in a hyperpycnal lobe, near to its axis. Sandstone beds include Curvolithus simplex, Gyrochorte comosa, Ophiomorpha nodosa, Palaeophycus tubularis, Phycosiphon incertum, Protovirgularia dichotoma, Ptychoplasma excelsum, Schaubcylindrichnus freyi, Skolithos linearis, large specimens of Rosselia socialis and indeterminate crustacean burrows. Chondrites isp. is present in the mudstone. High rates of both episodic and sustained sedimentation, degree of substrate consolidation, freshwater discharge and water turbidity are the most important stress factors in both channels and lobes. Taxonomic composition, uneven distribution of bioturbation through the successions, and overall low ichnodiversity help to distinguish these prodeltaic deposits from bathymetrically equivalent offshore strata in the same basin. Hyperpycnal flow deposits are formed in a wide variety of environmental settings, therefore displaying high ichnological variability. Such variability is summarized by characterising ichnofaunas from four different depositional settings: (i) lakes; (ii) shelf deltas; (iii) shelf‐edge deltas; and (iv) deep‐marine systems.

Integrated Ichnological and Sedimentological Analysis of the Cambrian Kunzam La (Parahio) Formation, Shian Section, Pin Valley, Spiti, Northwest Himalaya

The Kunzam La (Parahio) Formation along the Shian section of the Pin Valley was previously interpreted as containing Ediacaran–Cambrian boundary trace fossils, but re-examination of the Shian section shows that the oldest part of the section belongs to the late part of Cambrian Series 2, Stage 4, which contradicts the previous interpretation. The trace fossil assemblage comprises ?Arborichnus isp., Archaeonassa isp., Diplichnites isp., Hormosiroidea isp., Monomorphichnus lineatus, Bergaueria aff. langi, Palaeophycus tubularis, Rusophycus isp., and Treptichnus-like fossils that occur stratigraphically below the Oryctocephalus indicus biozone (Series 3, Stage 5) along the section and belong to the late part of Series 2, Stage 4. Sedimentary structures recorded along the section include hummocky cross-stratification (HCS) with deeply bioturbated tops, trough- and low-angle cross stratification, ball and pillow structures and climbing-ripple cross stratification. Integrated ichnofabric and sedimentological data suggest a storm-dominated, lower to upper shoreface shallow-marine environment of deposition.

Ichnology and sedimentology of the trace fossil-bearing fluvial red beds from the lowermost member of the Paleocene Funing Formation in the Jinhu Depression, Subei Basin, East China

Abstract The lowermost member of the Paleocene Funing Formation, which is composed of bioturbated fluvial red beds, is extensively distributed throughout the Jinhu Depression, Subei Basin, East China. Despite its economic value as one of the most important oil-bearing reservoirs in the Subei Basin, the sedimentology, ichnology and paleoenvironment of this formation in the Jinhu Depression remain poorly understood. In this work, we investigated the ichnofossils and sedimentary facies, analyzed the ichnofacies and potential tracemakers and reconstructed the paleoenvironment of the Jinhu Depression based on cores from the lowermost member of the Paleocene Funing Formation. This formation contains a moderately diverse ichnofauna (9 ichnotaxa of the Scoyenia ichnofacies) that includes meniscate burrows (Taenidium barretti, Taenidium satanassi and Beaconites coronus), simple horizontal cylindrical burrows (Palaeophycus tubularis, Palaeophycus heberti and Planolites isp.), simple vertical or subvertical burrows (Skolithos linearis and Skolithos isp.) and plant root traces. The other complex branched and chambered burrows are left in open nomenclature. These ichnofossils are widespread throughout the three facies associations identified in this study: (1) ephemeral fluvial channel, (2) crevasse splay and (3) distal floodplain facies associations. Multiple lines of sedimentological and ichnological evidence, namely, the predominance of massive and upper flow regime structures, the occurrence of invertebrate burrows (e.g., Skolithos and Taenidium) in the lower and middle parts of the channel deposits and the dramatic changes in the color and mottling in channel and overbank sediments, indicate that the river discharge was short lived and that the water table was highly variable. The variations in the discharge and water level are attributed to the influence of seasonal rainfall. The cyclic nature of intense rainfall events and dry periods suggests that the Subei Basin was likely located in a semiarid region with a seasonal rainfall pattern during the early Paleocene. This study also reveals that the ephemeral fluvial channel is the facies association with the highest potential to yield oil-bearing reservoirs in the Paleocene red beds of the Jinhu Depression. Additionally, the influence of bioturbation on the reservoir quality in this region should be considered in future research.

A diverse deep-sea trace fossil assemblage from the Adriatic Flysch Formation (middle Eocene – middle Miocene), Montenegro (central Mediterranean)

Our study of ichnofossils in the Adriatic Flysch suggests that mid-fan environments, with 30 ichnospecies and 13 architectural designs, provided most productive and best preservation conditions in the fine-grained turbidite system of the Dinarides-Albanides-Helenides deep foreland basin. The Adriatic Flysch Formation at its type section in Crnjak Cove (Montenegro) represents a 300-m-thick turbidite succession deposited from the middle Eocene to the middle Miocene. The flysch is exposed in an asymmetrical syncline in a 750-m-long outcrop. The conglomerates, sandstones, and mudstones are arranged in seven distinct turbidite facies, which represent three superimposed submarine fans. The inner-, mid-, and outer-fan facies of the submarine fans contain sixteen ichnogenera and thirty three ichnospecies, which exhibit thirteen architectural designs. The inner fan conglomerates and coarse-grained sandstones contain a low diversity (Ophiomorpha rudis, Ophiomorpha annulata, and Halopoa imbricata), a low disparity (two architectural designs), and a low-density post-depositional trace fossil assemblages of the Ophiomorpha rudis ichnosubfacies of the Nereites ichnofacies. The mid-fan greywackes contain very diverse pre-depositional trace fossils (Belorhaphe zickzack, ?Cosmorhaphe isp., Desmograpton dertonensis, Gordia isp., Helminthopsis isp., Helminthorhaphe flexuosa, ?Megagrapton isp., Paleodictyon arvense, Paleodictyon hexagonum, Paleodictyon itallicum, Paleodictyon latum, Paleodictyon majus, Paleodictyon maximum, Paleodictyon strozzii, Paleodictyon isp., Scolicia strozzii, Squamodictyon isp.) having six architectural designs and abundant post-depositional trace fossils (Halopoa imbricata, Ophiomorpha annulata, Ophiomorpha nodosa, Ophiomorpha rudis, Planolites beverleyensis, Planolites montanus, Palaeophycus alternatus, Palaeophycus striatus, Palaeophycus tubularis, Rhizocorallium commune, Scolicia prisca, Scolicia strozzii, Zoophycos isp.) exhibiting seven architectural designs, which constitute the Paleodictyon-Ophiomorpha rudis ichnosubfacies of the Nereites icnhnofacies in the Adriatic Flysch. The waning turbidity currents with slower rates of sediment deposition and deficiency of nutrients favored grapholyptid colonization of the outer fans. Relatively low abundance, and great diversity of graphoglyptids (Helminthorhaphe flexuosa, Desmograpton dertonensis, ?Megagrapton isp., Paleodictyon arvense, Paleodictyon hexagonum, Paleodictyon majus, Paleodictyon minimum, Paleodictyon strozzii, Paleodictyon isp., Squamodictyon isp.), but low disparity (three architectural designs), represents the Paleodictyon ichnosubfacies of the Nereites ichnofacies in the outer fan facies of the Adriatic Flysch. The diversity of pre-depositional ichnofossils in the Adriatic Flysch exceeds post-depositional forms, reflecting a dominance of K-selected over r-selected population strategies in a stable oligotrophic environment.

Palaeoenvironmental Significance of Ichnofossil Assemblages from the Paleogene Sediments of Inner Fold Belt, Naga Hills, NE India

ABSTRACT Paleogene sediments of the inner fold belt, Naga hills, have very well preserved ichnofossils. 16 ichnospecies have been documented among 13 ichnogenera such as Arenicolites isp., Chondrites targionii, Cylindrichnus isp., Diplocraterion parallelum, Gyrochorte isp., Ophiomorpha annulata, O. irregulaire, O. nodosa, O. rudis, Palaeophycus tubularis, Planolites beverleyensis, Scolicia palaeobullia, Skolithos linearis, Trypinites weisei, Thalassinoides horizontalis and Zoophycos isp. The ichnofossil assemblages comprise mostly domichnia and fodinichnia benthos of the Skolithos and Cruziana ichnofacies. A shallow marine nearshore to offshore marine environment with fluctuating energy condition has been envisaged.