The changing face of the deep: Colonization of the Early Ordovician deep-sea floor, Puna, northwest Argentina

An Upper Tremadocian deep-sea ichnofauna from the Chiquero Formation of Puna, northwest Argentina, represents a link between Ediacaran and Cambrian microbial-mat dominated ecosystems and younger Ordovician deep-marine trace-fossil assemblages. This ichnofauna is preserved at the base of thin-bedded turbidites formed in the lobe fringe of a back-arc deep-sea fan. While Ediacaran–Cambrian deep-marine trace fossils are typically linked to matground grazing and feeding, microbial textures in the Chiquero Formation are rare and not associated with trace fossils. Morphologic patterns (e.g. radial trace fossils and networks) of the Chiquero ichnofauna indicate the onset of novel trophic types, recording trapping of microorganisms and bacterial farming. However, in comparison with younger Ordovician deep-sea ichnofaunas, graphoglyptids are relatively rare, poorly diverse, and geometrically simpler. This study indicates that the Early Ordovician was a pivotal point in the ecology of deep-sea infaunal communities. This Upper Tremadocian ichnofauna records the arrival of the Agronomic Revolution to the deep sea. Comparisons with slightly older and younger deep-sea ichnofaunas demonstrate that the colonization of the deep sea was a protracted process spanning the Early Paleozoic, lagging behind colonization of nearshore and offshore substrates.     

Palaeoenvironmental implications of the ichnology and geochemistry of the Westbury Formation (Rhaetian), Westbury‐on‐Severn,south‐west England

Abstract: The Westbury Formation (Rhaetian) beds of Westbury Garden Cliff, Westbury‐on‐Severn, west of Gloucester, Britain, show an unusual combination of features. Both deep water and emergent characteristics are present within the sediments and the trace fossils. The ichnoassemblage consists of abundant Selenichnites, Planolites beverlyensis and Lockeia with rarer Oniscoidichnus, Chondrites, Rhizocorallium irregulare, Taenidium serpentium, an unusual form of Walcottia and Merostomichnites‐like traces. These trace fossils display an interesting relationship with the sediments: low‐energy Cruziana ichnofacies is found within high‐energy sandstones. The sandstones are interbedded with laminated mudstones, apparently deposited in deep water, but some aspects of the ichnoassemblage, preservation and sedimentation indicate shallower water. One new trace fossil, Radichnus allingtona igen. et isp. nov., closely resembles the traces of modern fiddler crabs and imply emergence, by analogy. This ichnofauna is similar to early stage disaster colonisation in recent experiments in Long Island Sound (south of Connecticut, USA) and with storm‐influenced deposits within the Cardium Formation (Seebe, Alberta, Canada). This indicates a lagoonal environment with influxes of sand and oxygen. Total organic carbon levels were found to fluctuate greatly between stratigraphic layers but remained relatively high. This implies low oxygen conditions. The abundance of sulphur (in pyrite) also supports an interpretation of anoxic conditions, and low sedimentation rates within the shale layers. A restricted shallow basin or lagoonal environment is proposed for the palaeoenvironment, with fluctuating oxygen influencing diversity.     

The Ichnofossils of the Triassic Hope Bay Formation,Trinity Peninsula Group,Antarctic Peninsula

The Triassic Hope Bay Formation (Trinity Peninsula Group) includes a diverse ichnocoenosis in the Puerto Moro succession (Hope Bay, Antarctic Peninsula). The Hope Bay Formation is a thick turbidite succession with a minimum vertical exposure of 533 meters along the Hope Bay coast. The rocks are locally affected by contact metamorphism related to later arc magmatism. The ichnofossils are found mainly in thick- and thin-bedded sandstone-mudstone facies composed of a monotonous repetition of sandstone-mudstone cycles. The sandstones are usually medium grained, massive or parallel laminated; the mudstones are massive and rarely laminated. In the fine-grained rocks, mainly the mudstones, there are distinct densities of bioturbation, and at least six patterns were observed. The following ichnogenera were recognized: Arenicolites Salter 1857, Lophoctenium Richter 1850, Taenidium Heer 1877, Palaeophycus Hall 1847, Phycosiphon von Fischer-Ooster 1858 and Rhizocorallium Zenker 1836. All appear to be feeding-traces. The trace fossil assemblages occur mainly in black mudstones rich in organic material that suggest a low oxygen environment. The stratigraphic interval in which they occur is interpreted as progradational supra-fan lobes with channel fill and levee deposits. The thin-bedded turbidite and mudstone lithofacies, where the ichnofossils are abundant, is interpreted as a distal fan turbidite or levee deposit related to a long-term channel fill. This study is the first significant report of trace fossils in the Hope Bay Formation.     

塔里木盆地西北缘志留系塔塔埃尔塔格组上段的遗迹化石

通过对塔里木盆地柯坪地区志留系塔塔埃尔塔格组上段遗迹化石的研究,识别出8属8种。根据组成、产状、分布规律及其围岩沉积特征,划分为2种不同沉积环境条件下的遗迹组合,即(1)Thalassinoides-Maca-ronichnus遗迹组合,主要组成分子有Thalassinoides suevicus,Macaronichnus segregatis和Rhizocorallium ganx-iensis等,形成于高氧高能的砂坪沉积环境;(2)Scoyenia-Beaconites遗迹组合,常见组成分子有Scoyenia gracilis,Beaconites antarcticus,Planolites vulgaris,Palaeophycus wutingensis和Monocraterioncf.tentaculatum,形成于混合坪-泥坪沉积环境。     

河南泌阳凹陷古近纪核桃园组遗迹化石组合及其环境意义——兼论深水湖泊遗迹相特征

南襄盆地泌阳凹陷古近纪核桃园组湖泊沉积中发育大量遗迹化石,含5个遗迹组合,形成于从滨湖到深湖的不同沉积环境中。Taenidiumserpentinum遗迹组合反映稍有覆水并周期性暴露的低能滨湖环境;Skolithos linearis遗迹组合代表湖泊中上临滨环境;Planolites montanus遗迹组合与低能浅湖环境有关;Skolithos verticalis遗迹组合形成于浅湖的远源风暴沉积中;Semirotundichnus dongyingensis遗迹组合发育在贫氧的半深湖-深湖沉积环境中。     

A diverse Upper Jurassic dinosaur ichnofauna from central‐west Portugal

Mateus, O. & Milàn, J. 2009: A diverse Upper Jurassic dinosaur ichnofauna from central‐west Portugal. Lethaia, Vol. 43, pp. 245–257. A newly discovered dinosaur track‐assemblage from the Upper Jurassic Lourinhã Formation (Lusitanian Basin, central‐west Portugal), comprises medium‐ to large‐sized sauropod tracks with well‐preserved impressions of soft tissue anatomy, stegosaur tracks and tracks from medium‐ to large‐sized theropods. The 400‐m‐thick Lourinhã Formation consists of mostly aluvial sediments, deposited during the early rifting of the Atlantic Ocean in the Kimmeridgian and Tithonian. The stratigraphic succession shows several shifts between flood‐plain mud and fluvial sands that favour preservation and fossilization of tracks. The studied track‐assemblage is found preserved as natural casts on the underside of a thin bivalve‐rich carbonate bed near the Tithonian–Kimmeridgian boundary. The diversity of the tracks from the new track assemblage is compared with similar faunas from the Upper Jurassic of Asturias, Spain and the Middle Jurassic Yorkshire Coast of England. The Portuguese record of Upper Jurassic dinosaur body fossils show close similarity to the track fauna from the Lourinhã Formation. □Dinosaur tracks, Lusitanian Basin, Portugal, skin impressions, Upper Jurassic.     

内蒙古宁城道虎沟地区中侏罗世非海相双壳类Ferganoconcha

Ferganoconcha是广泛分布于我国北部、中亚、西伯利亚和乌拉尔地区下、中侏罗统的一类非海相双壳类。Ferganoconchasibirica的产出表明道虎沟地区道虎沟层与辽西地区的海房沟组和冀北地区的九龙山组层位相当,时代介于早侏罗世晚期至中侏罗世之间。结合昆虫和叶肢介化石反映的时代,认为道虎沟层的时代可能为中侏罗世早中期。综合近年来在Ferganoconchidae的分类方面取得的进展,对F.sibirica进行了重新厘定。     

The earliest fossil evidence of bone boring by terrestrial invertebrates,examples from China and South Africa

We report the oldest fossil evidence of osteophagia by terrestrial invertebrates on both the Asian and African continents. Bones attributable to the Middle Jurassic dinosaur Chuanjiesaurus (Dinosauria: Sauropoda) were found with post-mortem insect modification in the Chuanjie Formation, Yunnan Province, China. The morphology of the borings closely matches the ichnogenus Cubiculum. Based on the lack of bioglyphs observed in Cubiculum ornatus, a new ichnospecies is proposed here. The new trace fossil, Cubiculum inornatus isp. nov., is interpreted to have been constructed for pupation by an unknown taxon of insect. Additionally, we report even older borings from Early Jurassic dinosaur bones of the Elliott Formation in the Karoo Basin, which represent the second oldest occurrence of insect traces in bone from continental settings. Both trace fossils sites have palaeogeographic implications for the origins and dispersal of osteophagia amongst terrestrial invertebrates during the Mesozoic. These discoveries push back the antiquity of pupation in animal bones by more than 100 million years to the Middle Jurassic, indicating that this behaviour, and osteophagy more generally, originated early in the Mesozoic, roughly comparable with the origination of insect pupation in woody substrates (Late Triassic).     

Ichnology of deep‐sea fan overbank deposits of the Ganei slates (Eocene,Switzerland)— a classical flysch trace fossil locality studied first by Oswald Heer

Ganei (Switzerland) is a classical locality for trace fossils. At this site, Heer (1877) described a large number of trace fossils, several of which were new taxa. The trace fossils occur in thin‐bedded turbidites in which the basal divisions of the Bouma sequence are typically absent; the turbidites are assigned to the Ganei Slates and are Eocene in age. They are interpreted to have been deposited in an overbank environment within an upper to middle fan area distal to a channel. Two trace‐fossil associations occur: the first (I) is characterized by bulldozing organisms producing biodeformational structures, Scolica, and Nereites irregularis; the second (II) association shows a distinct tiering pattern with near‐surface graphoglyptids and a mixed layer with simple tubes such as cf. Palaeophycus and Planolites, plus patterned tubes such as Nereites cirrinalis, and Chondrites. Deeper turbidite layers were colonized by Chondrites and Gyro‐phyllites. All trace fossils show a normal size spectrum compared to previously studied trace‐fossil associations, so the degree of oxygenation probably did not influence the composition of either trace‐fossil association. Seafloor sediment was probably soft and did not affect the trace‐fossil associations. Sedimentation rate and event frequency did not change and are estimated to have been in a range of 5–10 cm/1000 years and 2–5 events per 1000 years, respectively. The composition of trace‐fossil associations I and II is therefore interpreted to have been controlled by the benthic food content being higher for trace‐fossil association I than for II.     

A Late Triassic Invertebrate Ichnofauna from Ghost Ranch,New Mexico

Invertebrate trace fossils are reported from the Late Triassic Chinle Formation at Ghost Ranch, New Mexico, for the first time. They occur in beds higher in the section than the Coelophysis Quarry. Six ichnotaxa are recognized: Steinichnus milfordensis, Planolites montanus, Palaeophycus tubularis, Taenidium serpentium, ?Arenicolites sp. and Skolithos sp. This ichnofauna is consistent with the Scoyenia ichnofacies, considered typical of lake margins in semiarid to arid regions.     

Ichnology and sedimentology of a tide‐influenced delta in the Ordovician from the northeastern Alborz range of Iran (Kopet Dagh region)

The Middle–Late Ordovician Ghelli Formation in the Kopet Dagh region northeastern Alborz range of Iran is composed of siliciclastic rocks deposited in a variety of turbidite to marginal marine environments (deep marine clastic fan and related environments and prodelta, distal delta front, proximal delta front and distributary channels). The ichnology of the middle member of the Ghelli Formation is here reported. Combined sedimentological and ichnological analysis allows recognition of a tide‐influenced deltaic succession in the middle member of the Ghelli Formation consisting of three main facies associations: lower distributary channels, delta front and prodelta facies. Twenty‐two ichnogenera have been identified in this marginal marine succession: Arenicolites, Arthrophycus, Bergaueria, Chondrites, Conichnus, Cruziana, Cylindrichnus, Didymaulichnus, Diplichnites, Diplocraterion, Helminthopsis, Gyrochorte, Lockeia, Macaronichnus, Monomorphichnus, Palaeophycus, Planolites, Rosselia, Rusophcus, Skolithos, Teichichnus and ?Scolicia. Their distribution is clearly linked with lithofacies and depositional palaeoenvironments. The ichnological analysis reveals that the trace fossil suites developed in these environments indicate low diversity and low to moderate abundance of burrows, poor development of tiering and sporadic distribution. Low ichnodiversity and low bioturbation intensities with higher bioturbation clusters consist of facies‐crossing ichnogenera, and the impoverishment of suspension‐feeding trophic types indicates ‘stressed’, non‐archetypal expression of the Cruziana ichnofacies. The periodic higher intensities of bioturbation due to variations in hydrodynamic regimes of tidal currents reflect the archetypal of the Cruziana ichnofacies (and rare Skolithos ichnofacies).     

Ichnology and sedimentology of the early Permian deep-water deposits from the Lercara-Roccapalumba area (Western Sicily,Italy)

Summary Diverse and abundant trace fossils of the deep-waterNereites ichnofacies have been found in well-dated Early Permian deep-water turbidites (Lercara Formation) of western Sicily (Italy). Conodonts indicate a latest Artinskian to Cathedralian (late Early Permian) age. Microfossils (pelagic conodonts, albaillellid Radiolaria, paleopsychrospheric ostracods, foraminiferal associations dominated byBathysiphon), trace fossils (deep-bathyal to abyssalNereites ichnofacies) and sedimentologic data collectively indicate a deep-water environment for the Early Permian turbidites of the Lercara Formation. The dominance ofAgrichnium and of thePaleodictyon subichnogeneraSquamodictyon andMegadictyon suggests that this icnofauna is closely related in ichnotaxonomic composition to other late Paleozoic deep-water ichnofaunas. The occurrence ofAcanthorhaphe. Dendrotichnium andHelicoraphe, to date only reported from Cretaceous or Tertiary flysch deposits, suggests that the entire ichnofauna corresponds well to previously documented Silurian-Tertiary flysch ichnofaunas. Eight new ichnospecies and a new ichnosubgenus,Megadictyon, are described.     

First occurrence of the Ichnogenus Selenichnites from the Middle Jurassic Strata of the Skoura Syncline (Middle Atlas,Morocco); Palaeoecological and palaeoenvironmental context

Mesozoic strata of North Africa yield the first occurrence of the ichnogenus Selenichnites. The trace fossils occur on the top surface of a sandy carbonate deposit in the axis of a Middle Atlas syncline (Skoura Syncline, NE Morocco). The ichnofossil-bearing horizon belongs to the Late Bajocian–Early Bathonian Ich Timellaline/Bou Akrabene Formation. The trace fossils are crescent-shaped and the best preserved exhibits a posterior central axial impression (possible telson tail impression). They are interpreted as feeding burrows (fodinichnia) or hiding depressions of Xiphosurids or Limulids (horseshoe crabs) on a sandy carbonate substrate beneath a veneer of muddy deposits. The sedimentological character suggests a relatively protected shallow water subtidal palaeoenvironment preceding the Bathonian regression of the Atlas domain. This discovery provides the first evidence of xiphosurans or xiphosuran-like organisms inhabiting the southern shores of the Tethys in the Middle Jurassic.     

First Occurrence of Tetrapod Footprints from Westphalian Strata of the Sidi Kassem Basin,Central Morocco

The Sidi Kassem Basin is the only limnic basin of Westphalian age in Morocco. It is built up of 1,250 m of alluvio-fluvial to lacustrine deposits that have so far yielded plant fossils and invertebrate remains only. Recent exploration for fossil tetrapod footprints in floodplain-deposits of the basin revealed a moderately diverse vertebrate ichnofauna composed of tracks assigned to cf. Batrachichnus Woodworth, 1900; cf. Hylopus Dawson, 1882; Dimetropus Romer and Price, 1940; and Notalacerta Butts, 1891. The tracks can be referred to temnospondyl, anamniote reptiliomorph, non-therapsid synapsid (pelycosaur), and captorhinomorph trackmakers. The described ichnoassemblage is important in at least three aspects: (1) It suggests an Early to mid-Pennsylvanian age for the footprint-bearing strata of the study area. (2) It is the oldest association of tetrapod footprints from Africa. (3) It is the first evidence of the relatively rare ichnogenera cf. Hylopus and Notalacerta outside of North America and Europe. Judged from the variety of tetrapod tracks and previously collected floral remains, the Sidi Kassem Basin must have represented a well-established continental ecosystem during Pennsylvanian time. Further exploration for trace and body fossils of Palaeozoic vertebrates in this basin may be important for the reconstruction of early tetrapod evolution.     

Trace fossils in the Ediacaran-Cambrian transition: Behavioral diversification, ecological turnover and environmental shift

After taxonomic revision, trace fossils show a similarly explosive diversification in the Ediacaran-Cambrian transition as metazoan body fossils. In shallow-marine deposits of Ediacaran age, trace fossils are horizontal, simple and rare, and display feeding strategies related to exploitation of microbial matgrounds. Equally notable is the absence of arthropod tracks and sinusoidal nematode trails. This situation changed in the Early Cambrian, when a dramatic increase in the diversity of distinct ichnotaxa is associated was followed by the onset of vertical bioturbation and the disappearance of a matground-based ecology (‘‘agronomic revolution’’). On deep sea bottoms, animals have been present already in the Ediacaran, but ichnofaunas were poorly diverse and dominated by the horizontal burrows of undermat miners. As shown by the ichnogenus Oldhamia, this life style continued to be predominant into the Early, and to a lesser extent, Middle Cambrian. Nevertheless, there was an explosive radiation of behavioral programs during the Early Cambrian. When exactly the bioturbational revolution arrived in the deep sea is uncertain. In any case, the Nereites ichnofacies was firmly established in the Early Ordovician. The rich ichnofauna in the Early Cambrian Guachos Formation of northwest Argentina probably marks a first step in this ecological onshore-offshore shift.     

西北地区潮水盆地侏罗系青土井群轮藻化石

潮水盆地青土井群为一套含煤碎屑岩,在盆地东部潮参l井青土井群三段发育大量以Aclistochara占优势的轮藻化石群,其组合特征显示浓厚的晚侏罗世色彩。青土井群一、二段轮藻化石稀少,结合地层层序,推测其地质时代为早侏罗世。围岩沉积特征表明本井轮藻化石群为浅水生物群。     

Silurian trace fossils in carbonate turbidites from the Alexander arc of southeastern Alaska

Early to Late Silurian (Llandovery‐Ludlow) body and trace fossils from the Heceta Formation of southeastern Alaska are preserved in the oldest widespread carbonates in the Alexander terrane. These fossils represent the earliest benthos to inhabit diverse shallow and deep subtidal environments in the region and are important indicators of early stages in benthic community development within the evolving Alexander arc. The ichnofossils are particularly significant because they add to a small but growing body of knowledge about trace fossils in deep‐water carbonates of Paleozoic age.

Carbonate turbidites that originated along a deep marine slope within the arc yield a low‐diversity suite of trace fossils consisting of five distinct biogenic forms. Simple burrows (Planolites, two forms), ramifying tunnels (Chondrites), and tiny cylindrical burrows (?Chondrites) represent the feeding activities (fodinichnia) of pre‐turbidite animals that burrowed in the lime mud before the influx of coarser sediment deposited by turbidity currents. These trace fossils are associated locally with cross‐cutting burrows created as domichnia (Palaeophycus). Rarer hypichnial burrows and endichnial traces were created by post‐turbidite animals that fed soon after the deposition of coarse detritus from turbidity flows.

Trace fossils in these deposits reflect much lower diversity levels than in Paleozoic siliciclastic turbidites. This difference may represent unfavorable environmental conditions for infaunas, differential preservation, or significant paleogeographic isolation of the Alexander terrane during the Silurian. Greater utilization of trace fossils in terrane analysis may help to resolve this issue and provide new data for reconstructing the paleogeography of circum‐Pacific terranes.     

A new arthropod resting trace and associated suite of trace fossils from the Lower Jurassic of Warwickshire, England

Abstract:  A new suite of arthropod trace fossils, attributed to a decapod crustacean, is described from the Lower Jurassic Saltford Shale Member of the Blue Lias Formation of Southam Cement Works Quarry, eastern Warwickshire, England. Solusichnium southamensis igen. et isp. nov. consists of small, isolated, bilaterally symmetrical, suboval hypichnia, comprising three regions. The concave anterior region contains imprints of chelate appendages, antennae and antennules. The elongate middle region contains abdominal appendage imprints that extend laterally, separated by a bifurcated medial imprint. The convex posterior region terminates in a globular V-shaped telson imprint. The large sample size and range of trace morphologies allows identification of five morphotypes within a taphoseries. S. southamensis is found on the base of siltstone lenses in what is otherwise a dysaerobic laminated mudstone unit, associated with epichnial Rusophycus , and the suite of trace fossils is interpreted as the resting traces (Cubichnia) and escape reactions (Fugichnia) of small decapods that were trapped below a distal storm deposit. The producer of S. southamensis was possibly an Eryon -like decapod, similar to those known from the slightly older Wilmcote Limestone Member of southwestern Warwickshire.     

Short-term colonization trace-fossil assemblages in a carbonate lacustrineKonservat-Lagerstätte (Las Hoyas fossil site, Lower Cretaceous, Cuenca, Central Spain)

Summary Rhythmically laminated fine-grained lacustrine carbonatcs of the Cretaceous La Huérguina Limestone Formation at Las Hoyas fossil site, central Spain, contain not only a spectacular body fossil fauna, but also vertebrate and invertebrate trace fossils. The study of the Las Hoyas invertebrate ichnofauna provides valuable taphonomic, paleoecological and paleoenvironmental information and represents one of the first attempts to study in detail a lacustrine trace-fossil assemblage in carbonate rocks. The Las Hoyas ichnofauna includesCruziana problematica, Helminthoidichnites tenuis, Lockeia isp.,Palaeophycus tubularis, andTreptichnus pollardi. This assemblage is characterized by low ichnodiversity and small burrow size, and it is dominated by surface trails and extremely shallow burrows produced mostly by detritus feeders. The Las Hoyas ichnofauna indicates low to moderately low energy, permanently submerged, shallow-lacustrine areas. The ichnofauna is suggestive of environmental stress, most likely oxygen-depleted conditions in interstitial waters. Occurrence of traces in event beds indicates opportunistic colonization by epifauna and very shallow infauna during brief periods of improved oxygenation related to the passage of density underflows and dilute turbidity currents. The Las Hoyas ichnofauna resembles other shallow lacustrine trace-fossil assemblages of the archetypalMermia ichnofacies and differs significantly from the archetypalScoyenia ichnofacies. It is therefore best regarded as a proximal, depauperate example of theMermia ichnofacies. The Las Hoyas assemblage is similar to the slightly older lacustrine Montsec ichnofauna, but it is remarkably different from marine ichnocoenoses of other Mesozoickonservat-lagerst?tten in lithographic limestones such as those of Cerin, Solnhofen and Nusplingen.     

Composite Trace Fossil Assemblage in a Distal Carbonate Setting from the Tethys (Middle Jurassic,Betic Cordillera,Southern Spain)

Ichnological analysis of a Middle Jurassic carbonate surface from the Betic Cordillera (southern Spain) reveals a complex trace fossil assemblage, including softground Ophiomorpha, firmground Arenicolites, Thalassinoides and Gastrochaenolites, and hardground Trypanites as well as possible Gastrochaenolites. The ecological replacement in the macrobenthic community is interpreted according to successive suites that are controlled mainly by substrate consistency. Variations in composition and abundance of trace fossils between suites can be ecologically and/or taphonomically determined.