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Alfred Uchman - One of the best experts on this subject based on the ideXlab platform.
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feeding Traces of recent ray fish and occurrences of the Trace Fossil piscichnus waitemata from the pliocene of santa maria island azores northeast atlantic
PALAIOS, 2018Co-Authors: Alfred Uchman, Markes E. Johnson, Ricardo S. Ramalho, Paulo Torres, Bjorn Berning, Ana Cristina Rebelo, Carlos S MeloAbstract:The bowl-shaped Trace Fossil Piscichnus waitemata Gregory 1991 appears in Pliocene sandstones from Santa Maria Island (Azores Archipelago), extensively excavated during a stage of island evolution when the volcanic edifice was a guyot (flat-topped seamount) isolated in the NE Atlantic. The host sediments were deposited at depths from the intertidal zone to fair-weather wave base in a tropical climate under the influence of periodic storms and hurricanes. The Traces were produced by ray fishes hunting for polychaetes, crustaceans and bivalves living in the sediment, similar to present-day nearshore, warm waters in the Azores, Baja California Sur (Mexico), and New Zealand, from which examples of feeding depressions are drawn (incipient Piscichnus). While P. waitemata is abundantly present in planar sediments on top of the guyot, far fewer Trace Fossils occur in sandstone deposited on the guyot's margins. Presumably, the different densities of ray holes in the two sedimentary bodies were a response to lesser availability of prey, lower seawater temperatures (due to greater depths), and a more dynamic environment in which life conditions were less favorable. Moreover, the potential preservation of bowl-shaped depressions was lower in this setting, given the steepness of the seafloor, stronger currents, and constant sediment mobility. The top of the guyot was a more favorable habitat, refuge and/or nursery ground for many ray fishes. Measurement of the diameters of the ray holes indicate three distinct size classes, which may suggest that several species were responsible for their formation.
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vertically oriented Trace Fossil macaronichnus segregatis from neogene of santa maria island azores ne atlantic records vertical fluctuations of the coastal groundwater mixing zone on a small oceanic island
Geobios, 2016Co-Authors: Alfred Uchman, Markes E. Johnson, Ricardo S. Ramalho, Ana Cristina Rebelo, Carlos Ranulfo Melo, Ricardo Cordeiro, Sérgio P. ÁvilaAbstract:Abstract The Trace Fossil Macaronichnus segregatis is interpreted to be produced by opheliid polychaetes that feed on epigranular microbes and organic matter commonly abundant in shallow-marine foreshore sands. Resulting Traces are horizontal and typically random in orientation, but sometimes perpendicular to the shoreline. However, M. segregatis in Neogene sandy sediments from Santa Maria Island in the Azores shows a vertical or sub-vertical orientation. This is explained by vertical flow of pore waters and oxygenation fluctuations within the mixing zone between interstitial marine and freshwater aquifers–where epigranular microbes and organic matter are most enriched. On reefless volcanic oceanic islands like the Azores, insular shelves are invariably steep, narrow, and exposed to strong swell. Aquifers in this setting respond rapidly to small changes on account of limited shelf space and a high potential differential that stimulates a vertical shift in habitats. Freshwater aquifers on small, low-relief oceanic islands form a thin lens, the edges of which are wedged against marine interstitial waters and migrate up and down in response to changes caused by tides, storm surges and precipitation. During the Late Miocene–Early Pliocene, Santa Maria was an island fitting this description. Due to a waning volcanism, intense marine erosion and gradual submersion, the island developed a wide shallow platform covered by sandy shoals, as exemplified by the Malbusca section with vertical Macaronichnus. The process, however, is more acute on small, reflective beaches perched on rocky island coasts. Here, sand blankets cover small ramps cut in the basaltic bedrock, resulting in very limited freshwater aquifers subject to strong changes due to the low permeability of basalts. The mixing zone is therefore forced to migrate chiefly up and down, mostly due to tides. The same response is dramatic in sandy fillings trapped in basalt fissures. As a consequence, the producer of Macaronichnus was tightly constrained in movement. Both situations occur in the “Pedra-que-pica” section on Santa Maria.
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The Trace Fossil Gyrophyllites in deep-sea siliciclastic deposits of the Istebna Formation (Upper Cretaceous–Palaeocene) of the Carpathians: An example of biologically controlled distribution
Palaeogeography Palaeoclimatology Palaeoecology, 2015Co-Authors: Piotr Strzeboński, Alfred UchmanAbstract:Abstract Gyrophyllites kwassizensis Glocker occurs abundantly in deep-sea, density current siliciclastics of the Istebna Formation (Silesian Nappe, Outer Western Carpathians; Poland, Slovakia and Czech Republic), close to the Cretaceous–Palaeogene boundary. It is composed of petal-shaped lobes radiating from a thin shaft, forming rosettes on a few levels in the sediment. The Trace Fossil is interpreted as a feeding structure produced by a soft-body “worm”, which actively filled the lobes with mud transported from the underlying layer, probably in response to migration of redox boundary in a generally poorly oxygenated environment. Probably due to microbial decomposition of cellulose and other organic particles, the mud from below was more nutritional than the more fresh mud from the sea floor. The number of lobes in a rosette (from 7 to 15) is referred to ontogenetic development of the Tracemaker and indirectly to time of burrow occupation. The number varies between localities and may indicate a more hospitable habitat in the areas where the number is higher. G. kwassizensis occurs only in a narrow stratigraphic interval after a significant drop of sedimentation rate caused by non-eustatic reasons, in facies conditions, which are not unique during the long history (Late Jurassic–Miocene) of the external Carpathian subbasins. This suggests that facies control was less important for distribution of this Trace Fossil than some undetermined biological factors, which enabled successful, but incidental invasion of the Tracemaker to deep-sea floor of one of the subbasins – the Silesian Basin.
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the Trace Fossil lepidenteron lewesiensis a taphonomic window on diversity of late cretaceous fishes
Palaeontologische Zeitschrift, 2015Co-Authors: Malgorzata Bienkowskawasiluk, Alfred Uchman, Agata Jurkowska, Ewa świerczewskagladyszAbstract:The Trace Fossil Lepidenteron lewesiensis (Mantell 1822) provides an exceptional taphonomic win- dow to diversity of fishes as shown for the Upper Creta- ceous of Poland, in the Middle Turonian-Lower Maastrichtian deposits of the Opole Trough, Miechow Trough, Mazury-Podlasie Homocline, and SE part of the Border Synclinorium. Lepidenteron lewesiensis is an un- branched burrow lined with small fish scales and bones, without a constructed wall. It contains scales, vertebrae, and bones of the head belonging to ten taxa of teleostean fishes: two undetermined teleosteans, six undetermined Clupeocephala, one Dercetidae, and one undetermined euteleostean. The preservation of fish remains suggests that fishes were pulled down into the burrow by an animal, probably by eunicid polychaetes.
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a delayed response of the Trace Fossil community at the cretaceous paleogene boundary in the bottaccione section gubbio central italy
Geobios, 2015Co-Authors: Paolo Monaco, Francisco J Rodrigueztovar, Alfred UchmanAbstract:Abstract A bed-by-bed ichnological analysis at the classic Bottaccione section (Gubbio area, Italy), reveals an unusual response of ichnofauna to the environmental changes associated with the Cretaceous-Paleogene (K-Pg) boundary event. The Trace Fossil assemblage, consisting of Chondrites isp., Planolites isp., Thalassinoides isp., Trichichnus isp., and Zoophycos isp., is similar to that registered during Cenomanian and Turonian times, showing persistence of the same community for a long time interval in deep-sea carbonate deposits. Absence of significant changes through the K-Pg boundary confirms that the extinction did not touch the ichnofauna. The decline of Trace Fossils occurs at 6 cm above the K-Pg boundary, with the total absence of biogenic structures in a 3 cm-thick layer showing parallel laminations. A gradual record of Zoophycos and Planolites resumes in the overlying layers. This suggests a progression of inhospitable conditions for the macrobenthos, followed by a delayed response of ichnofauna to drastic diminution of available food starting about 15 k.y. after the K-Pg boundary event, and then a gradual recovery leading to pre-event environmental conditions.
Ludvig Lowemark - One of the best experts on this subject based on the ideXlab platform.
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morphological variability of the Trace Fossil schaubcylindrichnus coronus as a response to environmental forcing
Palaeontologia Electronica, 2016Co-Authors: Ludvig Lowemark, Masakazu NaraAbstract:Schaubcylindrichnus is an important Trace Fossil used in the characterization of offshore and shoreface depositional environments. Our understanding of this Trace has followed a winding path including the introduction of several new ichnospecies and the subsequent recent synonymization into one ichnospecies. Likewise, our understanding of the ethological interpretation of the Trace Fossil has evolved from gregarious headdown deposit feeders to filter feeders, until it recently was shown that the Tracemaker probably was a funnel feeder. Although several ichnospecies were recently synonymized into one ichnospecies, Schaubcylindrichnus coronus, variability in the number of tubes per sheaf and abundance of nested tubes, i.e., tubes that break up older tubes, were observed between different settings. These differences were studied in close detail at Miocene outcrops in Japan and Taiwan where the Trace Fossil occurs copiously and therefore allows the intraspecific morphological variability to be addressed. Around 2000 specimens from Japan and Taiwan were studied. The results show a distinct tendency for higher tube numbers in the offshore facies where sediments are characterized by higher silt/mud content, suggesting that S. coronus with higher tube numbers were constructed in a calm environment allowing longer dwelling periods. The increased abundance of nested tubes in settings characterized by thin sand layers indicate that the nested tubes are a reparation response to erosional events destroying the feeding funnels at the sediment-water interface. Consequently, tube number per sheaf and abundance of nested tubes may be used to further characterize the depositional environment in shoreface to offshore facies.
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testing ethological hypotheses of the Trace Fossil zoophycos based on quaternary material from the greenland and norwegian seas
Palaeogeography Palaeoclimatology Palaeoecology, 2015Co-Authors: Ludvig LowemarkAbstract:Abstract Despite the fact that the Trace Fossil Zoophycos has been found in rocks from most of the Phanerozoic, little consensus has been reached on how and why this intricate burrow was constructed. The Cenozoic morphotypes of Zoophycos typically include a helically coiled spreite arranged around a vertical shaft connected to the sediment surface. Morphological details and environmental preferences of the Zoophycos producer were studied using 156 cores from the Norwegian and Greenland Seas in order to test the different ethological hypothesis proposed for this Trace Fossil. The spreiten were constructed during interglacial or interstadial intervals and consist of a repeated alternation of lamellae consisting of fine-grained pelleted material, and coarse-grained unpelleted material, respectively. Spreiten were encountered in vigorously bioturbated sediment, in turbidite layers, and in layers dominated by coarse ice-rafted debris. This indifference to the composition of the substrate effectively rules out ethological models based on different forms of deposit-feeding, and the large size and wide spacing of the whorls of the spreiten also make the cesspit model unlikely. Rather, the observed features best agree with a cache behaviour, where the main purpose of the deep penetration was to store food and to prevent access by other burrowers, likely combined with some gardening of microbes. However, no indubitable evidence of a reworking of the cached material could be found, and probably the answer to how the cache was accessed by the producer is to be found in the marginal tube. The difference in diameter between marginal tube and spreiten lamellae, together with the presence of both open and filled marginal tubes indicate that the marginal tube is the result of a far more complex behaviour than simply a lateral shift through the sediment.
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ethological analysis of the Trace Fossil zoophycos hints from the arctic ocean
Lethaia, 2012Co-Authors: Ludvig LowemarkAbstract:The distribution of the Trace Fossil Zoophycos in Quaternary marine sediments from the Arctic Ocean was studied in twelve piston and gravity cores retrieved during the Swedish icebreaker expedition ...
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temporal variations of the Trace Fossil zoophycos in a 425 ka long sediment record from the south china sea implications for the ethology of the zoophycos producer
Geological Magazine, 2005Co-Authors: Ludvig Lowemark, Michael SarntheinAbstract:A 425 ka long record from piston core GIK17925-3 taken in the northeastern South China Sea was used to study the environmental conditions controlling the distribution of the Zoophycos Trace Fossil. The 12 m long core offers a unique opportunity to study the response of the Zoophycos -producing animal to environmental variations over four glacial–interglacial cycles. The Trace Fossils show a strong glacial to interglacial variation in their abundance with a special preference for intervals with low sedimentation rates. Additional X-ray radiograph studies of piston cores from the Southeast Asian Marginal Seas show that the Trace Fossil Zoophycos is widespread in slope and deep-marine sediments, with the highest abundances encountered in low sedimentation rate settings. The preference of the Zoophycos producer for low sedimentation rates in a setting with strong seasonal fluctuations in food supply due to the shift between winter and summer monsoons, is interpreted to be the result of a cache-model behaviour, where food is collected during rich times and squirrelled away for poor times. Core GIK17925-3 also offers an opportunity to assess the impact of Zoophycos bioturbation on various palaeoenvironmental proxies. In this core, more than 30 % of the measured data points were more or less strongly affected by Zoophycos bioturbation. Together with the widespread occurrence this percentage indicates that Zoophycos may pose a serious threat to palaeoclimatic reconstructions in cores from low to moderate sedimentation rate sites.
John Paul Zonneveld - One of the best experts on this subject based on the ideXlab platform.
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the co occurence of trypanites and glossifungites substrate controlled Trace Fossil assemblages in a triassic mixed siliciclastic carbonate depositional system baldonnel formation williston lake b c canada
Journal of Sedimentary Research, 2016Co-Authors: Sarah K Schultz, Carolyn M Furlong, John Paul ZonneveldAbstract:Abstract Detailed outcrop analysis of an Upper Triassic, shallow marine, mixed siliciclastic–carbonate ramp succession in northwestern Canada reveals numerous disconformities that are characterized by substrate-controlled Trace-Fossil assemblages. Although Glossifungites assemblages, and to a lesser extent, Trypanites assemblages, are common in the Upper Carnian Baldonnel Formation, in several horizons, a pattern of paired Trypanites–Glossifungites-demarcated discontinuity surfaces occurs. These paired surfaces occur in the same overall environmental setting and are interpreted to have the same general stratigraphic implications in each case. The Trypanites surfaces invariably occur lower in the section. They penetrate into sandy bioclastic limestone and are infilled and overlain by a coarse-grained detrital lag. Their development indicates early cementation in a coastal setting. The Trypanites surfaces form coplanar maximum regressive surfaces and transgressive surfaces of erosion and are correlatable on a regional scale. The lags are overlain, in turn, by laminated calcareous siltstone (denoting offshore deposition) and bioclastic sandstone (a return to shoreface depositional conditions). The siltstone–sandstone contacts are characterized by low-diversity Glossifungites assemblages, which are interpreted as an amalgamated succession of storm-induced wave ravinement surfaces emplaced in front of a rapidly prograding shoreface. Paired Trypanites–Glossifungites surfaces in the Baldonnel Formation reflect fluctuations in relative sea level and sediment input in an overall low accommodation mixed siliciclastic–carbonate ramp setting.
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lingulide brachiopods and the Trace Fossil lingulichnus from the triassic of western canada implications for faunal recovery after the end permian mass extinction
PALAIOS, 2007Co-Authors: John Paul Zonneveld, Tyler W Beatty, George S PembertonAbstract:Abstract The environmental distribution of lingulide brachiopods in western Canadian Triassic marine successions, their relationship with other infaunal organisms occupying the same ecospace, and their role in the aftermath of the Permian-Triassic extinction event is summarized. Western Canada is an ideal location to assess lingulide distribution patterns as upper Paleozoic and lower Mesozoic strata are extensively exposed, and lingulides (cf. Lingularia Biernat and Emig) and the Trace Fossil Lingulichnus Hakes are both common. A distribution comparison of in situ lingulides and Lingulichnus Hakes with concordantly emplaced lingulide shells and shell beds shows clearly that the latter is a poor indicator of true environmental distribution of these infaunal suspension feeders. Lingulides are rare in uppermost Paleozoic strata in the study area. Most occurrences consist of isolated valves or abraded material in erosional lags. Lingulides remain minor components of infaunal communities during the earliest Tr...
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lunulichnus tuberosus ichnogen and ichnosp nov from the early eocene wasatch formation Fossil butte national monument wyoming an arthropod constructed Trace Fossil associated with alluvial firmgrounds
Ichnos-an International Journal for Plant and Animal Traces, 2006Co-Authors: John Paul Zonneveld, Jason M Lavigne, William S Bartels, Gregg F GunnellAbstract:A new Trace Fossil, Lunulichnus tuberosus, is described from fluvial deposits of the Wasatch Formation (early Eocene) at Fossil Butte National Monument, southwestern Wyoming, USA. L. tuberosus are straight, vertical to obliquely oriented, unlined cylindrical burrows with pronounced crescent-shaped wall sculptings. In situ examples of these Trace Fossils are most commonly preserved as sand-filled casts emanating from the erosional bases of fluvial channel sandstone bodies into underlying floodplain mudstone/siltstone beds. L. tuberosus is interpreted as the dwelling Trace of a stream-dwelling decapod crustacean. Excellent preservation of fine detail, particularly their diagnostic crescent-shaped wall sculptings, support the hypothesis that L. tuberosus were excavated in firm substrata subjacent to fluvial erosional surfaces. As such, they are interpreted as constituents of alluvial Glossifungites Trace Fossil assemblages.
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colonization of brackish water systems through time evidence from the Trace Fossil record
PALAIOS, 2005Co-Authors: Luis A Buatois, Gabriela M Mangano, Murray K Gingras, John Paul Zonneveld, James A Maceachern, George S Pemberton, Renata Guimaraes Netto, Anthony J MartinAbstract:Abstract Trace Fossils in estuarine deposits of different ages have been compared to evaluate colonization history of brackish-water ecosystems and to calibrate Trace-Fossil, brackish-water models with respect to geologic time. This comparative analysis reveals that, although the colonization of marginal-marine, brackish-water environments was a long-term process that spanned most of the Phanerozoic, this process of invasion of fully marine organisms into restricted, marginal-marine habitats did not occur at a constant rate. Five major colonization phases can be distinguished. The first phase (Ediacaran–Ordovician) represents a prelude to the major invasion that occurred during the rest of the Paleozoic. While Ediacaran–Cambrian ichnofaunas seem to be restricted to the outermost zones of marginal-marine depositional systems, Ordovician assemblages show some degree of landward expansion within brackish-water ecosystems. Intensity of bioturbation and ichnodiversity levels were relatively low during this pha...
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Trace Fossil assemblages in a middle triassic mixed siliciclastic carbonate marginal marine depositional system british columbia
Palaeogeography Palaeoclimatology Palaeoecology, 2001Co-Authors: Murray K Gingras, John Paul Zonneveld, S G PembertonAbstract:Abstract A diverse ichnoFossil assemblage characterizes the mixed siliciclastic-carbonate marginal marine succession of the upper Liard Formation (Middle Triassic), Williston Lake, northeastern British Columbia. Sedimentary facies within this succession consist of five recurring facies associations: FA1 (upper shoreface/foreshore); FA2 (washover fan/lagoon); FA3 (intertidal flat); FA4 (supratidal sabkha) and FA5 (aeolian dune). Shoreface/foreshore sediments (FA1) accumulated on a storm-dominated, prograding barrier island coast and are characterized by a low-diversity Skolithos assemblage (Diplocraterion, Ophiomorpha, Palaeophycus, Planolites, Skolithos and Thalassinoides). Washover fan/lagoonal sediments (FA2) are dominated by trophic generalists. (Cylindrichnus, Gyrochorte, Palaeophycus, Planolites, Skolithos, Trichichnus and an unusual type of bivalve resting Trace), consistent with deposition in a setting subject to periodic salinity and oxygenation stresses. Intertidal flat deposits (FA3) are characterized by a diverse mixture of dwelling, feeding, and crawling forms (Arenicolites, Cylindrichnus, Diplocraterion, Laevicyclus, Lingulichnus, Lockeia, Palaeophycus, Planolites, Rhizocorallium, Siphonichnus, Skolithos, Teichichnus, Taenidium, and Thalassinoides, reflecting the presence of adequate food resources in both the substrate and in the water column. Vertical burrow-dominated Trace Fossil assemblages within thin, sharp-based sand beds are interpreted as intertidal tempestites and reflect post-event colonization of the intertidal zone by shoreface organisms. Supratidal sabkha deposits (FA4) are characterized by an exceptionally low-diversity Trace Fossil assemblage (Cylindrichnus, Monocraterion and rare diminutive Ophiomorpha). Solution collapse breccia and root Traces overprint many primary physical and biogenic sedimentary structures, reflecting numerous cycles of desiccation and flooding. Aeolian dune deposits (FA5) consist of unFossiliferous, exceptionally well-sorted sandstone beds.
Soren Jensen - One of the best experts on this subject based on the ideXlab platform.
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Trace Fossils from the dividalen group of northern finland with remarks on early cambrian Trace Fossil provincialism
Gff, 2006Co-Authors: Ylo Systra, Soren JensenAbstract:Abstract The Dividalen Group is exposed in a narrow zone along the eastern Caledonian front of northern Fennoscandia. Trace Fossils provide important age constraints in these largely siliciclastic strata and demonstrate that in Sweden the entire Dividalen Group is of Cambrian age. Here we provide the first detailed description of Trace Fossils from the Dividalen Group in Finland, based on new material from the Kilpisjarvi area. This material includes the vertical spiral Gyrolithes polonicus and Trace Fossils with a three-lobed lower surface, here informally described as the Bure ichnocomplex. These Trace Fossils have a wide distribution in Baltica and probably represent a rare case of Trace Fossil provincialism.
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a complex Trace Fossil from the spitskop member terminal ediacaran lower cambrian of southern namibia
Geological Magazine, 2005Co-Authors: Soren Jensen, Bruce RunnegarAbstract:Streptichnus narbonnei igen. et isp. nov., a new Trace Fossil from the upper part of the Spitskop Member of the Urusis Formation, southern Namibia, consists of clusters of unidirectionally curved radial elements, in which individual elements typically are composed of imbricated sickle-shaped segments somewhat comparable to those of Treptichnus pedum . Such complex Trace Fossils generally are found only in Cambrian or younger strata. This opens to question the position of the Ediacaran–Cambrian boundary in the Nama Group, suggesting that it may locally be within the uppermost part of the Urusis Formation, rather than at the base of the Nomtsas Formation.
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Trace Fossil preservation and the early evolution of animals
Palaeogeography Palaeoclimatology Palaeoecology, 2005Co-Authors: Soren Jensen, Mary L Droser, James G GehlingAbstract:Abstract The Trace Fossil record is an important element in discussions of the timing of appearance of bilaterian animals. A conservative approach does not extend this record beyond about 560–555 Ma. Crucial to the utility of Trace Fossils in detecting early benthic activity is the preservational potential of Traces made close to the sediment–water interface. Our studies on the earliest Cambrian sediments suggest that shallow tiers were preserved to a greater extent than typical for most of the Phanerozoic. This can be attributed both directly and indirectly to the low levels of sediment mixing. The low levels of sediment mixing meant that thin event beds were preserved. The shallow depth of sediment mixing also meant that muddy sediments were firm close to the sediment–water interface, increasing the likelihood of recording shallow tier Trace Fossils in muddy sediments. Preservation of surficial Trace Fossils in this type of setting remains problematic but the above factors suggest that also these can be expected to have left a reasonable record. Overall, the Trace Fossil record can be expected to provide a sound record of the onset of bilaterian benthic activity. The lack of convincing Trace Fossils significantly before the Cambrian supports models of late appearance of macroscopic benthic bilaterians.
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the proterozoic and earliest cambrian Trace Fossil record patterns problems and perspectives
Integrative and Comparative Biology, 2003Co-Authors: Soren JensenAbstract:SYNOPSIS. The increase in Trace Fossil diversity across the Neoproterozoic-Cambrian boundary often is presented in terms of tabulations of ichnogenera. However, a clearer picture of the increase in diversity and complexity can be reached by combining Trace Fossils into broad groups defined both on morphology and interpretation. This also focuses attention on looking for similarites between Neoproterozoic and Cambrian Trace Fossils. Siliciclastic sediments of the Neoproterozoic preserve elongate tubular organisms and structures of probable algal origin, many of which are very similar to Trace Fossils. Such enigmatic structures include Palaeopascichnus and Yelovichnus, previously thought to be Trace Fossils in the form of tight meanders. A preliminary two or tripartite terminal Neoproterozoic Trace Fossil zonation can be be recognized. Possibly the earliest Trace Fossils are short unbranched forms, probably younger than about 560 Ma. Typical Neoproterozoic Trace Fossils are unbranched and essentially horizontal forms found associated with diverse assemblages of Ediacaran organisms. In sections younger than about 550 Ma a modest increase in Trace Fossil diversity occurs, including the appearance of rare three-dimensional burrow systems (treptichnids), and Traces with a three-lobed lower surfaces.
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Complex Trace Fossils from the terminal Proterozoic of Namibia
Geology, 2000Co-Authors: Soren Jensen, James G Gehling, Beverly Z. Saylor, Gerard J.b. GermsAbstract:We document for the first time the occurrence of the complex Trace Fossil Treptichnus from the terminal Proterozoic Nama Group, Namibia. These Traces differ in detail from the Cambrian index Fossil Treptichnus pedum , but document precursors with the same basic behavior. The producer of the Trace is not known. In its complexity, however, this Trace Fossil provides strong evidence for advanced latest Proterozoic bilaterians.
Michael Sarnthein - One of the best experts on this subject based on the ideXlab platform.
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temporal variations of the Trace Fossil zoophycos in a 425 ka long sediment record from the south china sea implications for the ethology of the zoophycos producer
Geological Magazine, 2005Co-Authors: Ludvig Lowemark, Michael SarntheinAbstract:A 425 ka long record from piston core GIK17925-3 taken in the northeastern South China Sea was used to study the environmental conditions controlling the distribution of the Zoophycos Trace Fossil. The 12 m long core offers a unique opportunity to study the response of the Zoophycos -producing animal to environmental variations over four glacial–interglacial cycles. The Trace Fossils show a strong glacial to interglacial variation in their abundance with a special preference for intervals with low sedimentation rates. Additional X-ray radiograph studies of piston cores from the Southeast Asian Marginal Seas show that the Trace Fossil Zoophycos is widespread in slope and deep-marine sediments, with the highest abundances encountered in low sedimentation rate settings. The preference of the Zoophycos producer for low sedimentation rates in a setting with strong seasonal fluctuations in food supply due to the shift between winter and summer monsoons, is interpreted to be the result of a cache-model behaviour, where food is collected during rich times and squirrelled away for poor times. Core GIK17925-3 also offers an opportunity to assess the impact of Zoophycos bioturbation on various palaeoenvironmental proxies. In this core, more than 30 % of the measured data points were more or less strongly affected by Zoophycos bioturbation. Together with the widespread occurrence this percentage indicates that Zoophycos may pose a serious threat to palaeoclimatic reconstructions in cores from low to moderate sedimentation rate sites.