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Language Spanish journal of palaeontology. 2014. Vol. 29, no. 2
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- Isotopic and mineralogical variations in the infill of Chondrites from organic-rich black shale (Posidonia Shale, Germany) for assessing the mode of colonization(2020) Izumi, KentaroThe compositional variations of the infill of Chondrites within the Toarcian (Lower Jurassic) organic-rich black shale of southern Germany were evaluated on the basis of organic carbon-isotope and XRD analyses of the infill, surrounding black shale, and overlying greenish-grey mudstone for assessing the mode of colonization by the trace-maker. Both carbon-isotope rations and the mineralogical compositions (i.e., quartz/calcite peak-height-ratio) of the infill show much larger variations than those of the overlying mudstone and ambient black shale. These limes of evidence strongly confirm the prolonged upward migration model, and the short-term opportunistic colonization model is not likely in this case. Although the obtained data cannot directly provide any evidence of the chemosymbiotic trace-maker model, this study also indicates that the isotopic and mineralogical variations recorded in the infill of Chondrites can be used as good indicators to assess the trace-maker’s colonization style, furthermore to distinguish opportunistic/climax trace fossil
- Ichnology and sedimentology of estuarina deposits, Mata Amarilla Formation, Austral Basin, Argentina(2020) Richiano, Sebastián; Varela, Augusto N; Cereceda, Abril; Poiré, Daniel GThe Mata Amarilla Formation (Upper Cretaceous) is part of the infilling of the Austral Basin (Patagonia, Argentina). This unit is mainly composed of grey to black mudstones interbedded with fine-to coarse-grained sandstones, deposited in littoral and continental environments. Three informal sections have been defined; the littoral deposits of the lower and upper sections constitute the object of this study. The intervals contain Arenicolites, Chondrites, Cylindrichnus, Ophiomorpha, Palaeophycus, Skolithos, Thalassinoides, Teredolites and fugichnia. The sedimentological and ichnological analyses allowed the distinction of three facies associations (FA) developed in an estuarine palaeoenvironment The more proximal FA1 is the bay-head delta, comprising delta-front bars of course-grained sandstone, containing Arenicolites, Skolithos and allochthonous petrified wood with Teredolites. This trace fossils association indicates high-energy conditions. The FA2, interpreted as estuarine bars, is composed of fine-to medium-grained containing herringbone cross-stratification and mud drapes with Cylindrichnus, Ophiomorpha, Skolithos, Thalassinoides and fugichnia. This reflects a setting with a high sedimentation rates, moderate energy, unstable substrates, and normal salinity. Finally, the FA3 (fine-grained estuarine deposits) are characterized by heterolithic rocks with synaeresis cracks and Arenicolites, Chondrites, Cylindrichnus, Palaeophycus, Thalassinoides and Skolithos. These ichnogenera are generally characterized by small sizes, consistent with a Salinity stressed paleoenvironment. The distribution, size and abundance of the trace fossils were controlled by several environmental factors, e.g. energy, sedimentation rate and salinity contents. The palaeoenvironmental factors variability is directly related to the fresh water and sediment input from rivers flood, which took place during the wet season of a warm, temperate climate
- Is Macaronichnus an exclusively small, horizontal and unbranched structure? Macaronichnus segregatis degiberti isubsp. nov.(2020) RodrĂguez-Tovar, Francisco Javier; Aguirre, JulioThe new ichnosubspecies Macaronichnus segregatis digiberti from Miocene deposits of Cádiz, SW Spain, is described. This ichnotaxa shows the characteristic presence of a mineralogical segregation within the tube, with a core made up of low density material, surrounded by a rim of glauconite. However significant differences in size, orientation and branching with respect to the type species of Macaronichnus are observed. Macaronichnus segregatis digiberti is characterized by a diameter between 4 mm and 12 mm, with common obliquely an even vertically oriented galleries, and the presence of frequent branching. Different types of branching can be observed, including false, primary/secondary successive, and true, simultaneous branching. Specimens occur in a wide range of palaeoenvironmental contexts, from inner to outer siliciclastic shelf. This includes deeper and more distal habitats than those usually interpreted for Macaronichnus. Macaronichnus segregatis digiberti could be produced by a new tracemaker showing a composite behaviour, pascichnia being the main strategy an dominichnia/cubichnia or repichnia, a secondary, sporadic one
- Artichnus giberti isp. nov., a possible holothurian burrow from the Miocene of El camp de Tarragona Basin (NE Spain)(2020) Belaústegui, Zain; Domènech, Rosa; Martinell, JordiA new ichnotaxon, Artichnus giberti isp. nov., is described in the marine middle Miocene (Serravallian) of the El Camp de Tarragona Basin, north eastern Spain. It is a mostly horizontal and rectilinear, tubular burrow with laminated lining. Artichnus giberti is interpreted as the result of the burrowing activity of a deposit- or suspension-feeding, worm- like animal, most likely a holothurian. This new Iberian occurrence extends the known temporal and geographical records of the ichnogenus Artichnus, which was previously restricted to the Eocene of Poland
- Ichnology and sedimentary environment of Cretaceous redbeds in the Ruyang Basin, western Henan Province, China(2020) Bin, Hu; Changzheng, Wang; Yuanyuan, WangA sequence of terrestrial clastic redbeds of Cretaceous age is exposed in the Ruyang Basin of western Henan Province in China. The rocks consist of conglomerate, sandstone, siltstone and mudstone containing the ichnofossils Psilonichnus, Arenicolites, Palaeophycus, Scoyenia, Planolites, Skolithos and other burrows and rhizoliths. The beds also contain the dinosaur fossil Huanghetitan ruyangensis and Zhongyuansaurus luoyangensis. On the basis of the lithology, sedimentary structures and ichnofossils, it is suggested that the sedimentary environments of the Ruyang Basin during the Cretaceous were primarily alluvial fan in character including middle fan and fan edge subfacies. In this sedimentary setting, eight lithofacies types are distinguished, and two ichnoassemblages are recognized: (1) Scoyenia-Skolithos ichnoassemblage occcuring in braided fluvial deposits of an alluvial fan system, and (2) Psilonichnus-Palaeophycus ichnoassemblage occurring in shallow pond or lake deposits at the fan edge
- Crassostrea patagonica (d'Orbigny, 1842) shell concentrations from the late Miocene of RĂo Negro province, NE Patagonia, Argentina(2020) Domènech, Rosa; Farinat, Ester A; Martinell, JordiThe RĂo Negro Formation (late Miocene-early Pliocene) mainly consists of continental deposits, but it contains a middle member of marine origin. It represents a transgressive-regressive sequence that can be seen at several outcrops along the N Patagonian coast. The taphonomical approach to the El EspigĂłn marine deposits permits the identification of four main layers containing different kinds of skeletal accumulation, which mainly consists of oyster shells [Crassostrea patagonica (d'Orbigny, 1842)]. These concentrations display three different morphologies (pouches, pavements and bouquets) with a different taphonomic signature. These deposits were formed in shallow marine environments influenced by wave activity that produced valve concentrations of different entities. They contain several shell beds that represent event, composite, hiatal to lag skeletal concentrations. Trace of bioturbation in the sediment (Thalassinoides, Teichichnus) and bioerosion on the shells (Entobia, Gastrochaenolites, Caulostrepsis), and encrusters (cirripeds, bryozoans), are also abundant in the outcroup and constitute common components of these Miocene materials. Layers 1 and 2 of the sequence were deposited in shoreface(foreshore environments at the beginning of a highstand systems tract, while layers 3 and 4 were deposited at the end, or at the beginning of a forced regression, in foreshore environments, A final erosional episode cut the top of layer 4, which truncated the abundant bioturbation developed there
- On small quadrupedal ornithopod tracks in Jurassic-Cretaceous transition intertidal deposits (El Castellar, Teruel, Spain)(2020) Alcalá, Luis; Mampel, Luis; Royo-Torres, Rafael; Cobos, AlbertoThe study of an undescribed part of the El Pozo tracksite in El Castellar (Teruel, Spain) has revealed two new trackways made by small ornithopods showing new evidences of basal ornithopods pes and manus track morphologies in the Jurassic-Cretaceous transition. The site lies within the Villar del Arzobispo Formation, which was deposited during the Tithonian-Berriasian in an environment under the influence of tides. The pes tracks are small tridactyl tracks, the digits are similar in size, and the heel is open and rounded. The presence of oval manus tracks in front of the tridactyl tracks is one of the trackways confirms that the dinosaur is a representative of the dryosaurid or the basal Ankylopollexia clades. These tracks are smaller than those described for the Las Cerradicas site, also located in Teruel and in the same formation; consequently, these tracks from El Pozo site constitute some of the smallest ornithopods trackways with quadrupedal locomotion ever described in the world. In addition, in the same tracksite bed, there are some poorly preserved tracks attributed to big quadrupedal dinosaur
- The Bichordites ichnofabric in the Pleistocene ocean current-generated sand ridge complex(2020) Nara, MasakazuThe ichnofabric characterised by Bichordites monastiriensis, a fossil burrow of the echinocardiid spatangoid echinoid, is first reported from the large-scale subaqueous dune (sand wave) deposits of the ocean current-generated shelf sand ridge complex of the middle Pleistocene Ichijiku Formation of the Boso peninsula, Japan. It consists of dominant B. monastiriensis and associated Alcyonidiopsis, large Macaronichnus, Piscichnus, Scolicia, Skolithos and unnamed escapes structures. Similar Bichordites-dominant ichnofabrics have been reported from Neogene to Quaternary sand wave deposits formed by various agents (such as tidal currents, storm-induced currents, or fair-weather wave-generated currents) whose depositional environments range from the deep sea floor to the shallow shelf. Although sand wave systems are commonly characterised by rapid sedimentation and highly shifting substrates, preventing colonisation by most benthic animals, rapid burrowers such as the echinocardiids were likely able to inhabit these regions regardless of the dominant depositional agents or the water depths of the habitats. The fossils record of Bichordites dates back to the Oligocene, although the trace fossil became particularly common in the Miocene and the known tracemakers (i.e., the echinocardiids and the maretiids) appeared in the Eocene. Moreover, these tracemakers now described here may be used as an indicator of highly shifting substrates, such as those found in sand wave systems, in the Cenozoic
