Alfred Uchman

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

Various trace fossils from the Hassberge Formation and the Löwenstein Formation (Middle Keuper, Upper Triassic) of the Haßberge region are described. Twenty-three different forms have been identified, 17 of which are named, includingCruziana pascens n. isp.,Lockeia cunctator n. isp., andRusophycus versans n. isp.Lockeia siliquariaJames, 1879,L. amygdaloides (Seilacher, 1953),L. triangulichnusKim, 1994, andL. elongata (Yang, 1984) are revised and synonymized under the oldest available name,L. siliquariaJames, 1879.Rusophycus eutendorfensis (Linck, 1942) andR. carbonariusDawson, 1864 are revised. The diagnosis ofPolykladichnusFürsich, 1981 is emended, and a diagnosis forHelminthoidichnitesFitch, 1850 is given for the first time. Among the described ichnotaxa,Skolithos ispp.,Rusophycus carbonarius, andTaenidium barretti are the most common forms. The trace fossil association is typical of theScoyenia ichnofacies, which indicates non-marine, periodically or completely inundated environments, such as floodplains and lake margins. Two palaeoichnocoenoses are identified. One ichnocoenosis, dominated byCruziana problematica, cf.Polykladichnus isp., andSkolithos isp. B characterizes margins of trough cross-bedded sandstones. Another ichnocoenosis, dominated byRusophycus versans n. isp.,Taenidium barretti,Scoyenia gracilis andSkolithos isp. A is related to ephemeral lake deposits. Taxonomic recommendations for the use of hitherto described and figured invertebrate Keuper trace fossils from Germany are given.ZusammenfassungAus dem mittleren Keuper (Hassberge Formation, Löwenstein Formation) der Haßberge in Unterfranken wird eine sehr reichhaltige Spurenfauna beschrieben. Es können insgesamt 23 verschiedene Formen unterschieden werden, wovon 17 formell beschrieben werden. Unter ihnen werdenCruziana pascens n. isp.,Lockeia cunctator n. isp undRusophycus versans n. isp. erstmals beschrieben.Lockeia siliquariaJames, 1879,L. amygdaloides (Seilacher, 1953),L. triangulichnusKim, 1994 undL. elongata (Yang, 1984) werden revidiert und unter dem ältesten verfügbaren SynonymL. siliquariaJames, 1879 zusammengefaßt.Rusophycus eutendorfensis (Linck, 1942) undR. carbonariusDawson, 1864 werden ebenfalls revidiert. Die Diagnose vonPolykladichnusFürsich, 1981 wird emendiert, und zuHelminthoidichnitesFitch, 1850 wird erstmals eine Diagnose erstellt. Unter den bearbeiteten Formen sindSkolithos ispp.,Rusophycus carbonarius undTaenidium barretti die häufigsten Spurenfossilien. Die Spurengemeinschaft kann derScoyenia-Ichnofazies zugeordnet werden, die charakteristisch für nichtmarine Ablagerungen randlicher Bereiche ephemerer Seen sowie für Überflutungsebenen ausgedehnter Flusssysteme ist. Innerhalb der gesamten Spurenassoziation können zwei Paläoichnozönosen unterschieden werden: (1) Eine vonCruziana prolematica, cf.Polykladichnus isp. sowieSkolithos isp. B dominierte Ichnozönose, die auf randliche Bereiche rinnenförmiger Sandsteinkörper beschränkt ist, und (2) eine hauptsächlich vonRusophycus versans n. isp.,Taenidium barretti, Scoyenia gracilis sowieSkolithos isp. A aufgebaute Ichnozönose. Diese Ichnocoenose ist typisch für die Ablagerungen ephemerer Seen. Abschließend werden Vorschläge zur Nomenklatur von Spurenfossilien gegeben, die bereits früher aus dem Keuper Deutschlands beschrieben wurden.

Deep-sea benthic food content recorded by ichnofabrics; a conceptual model based on observations from Paleogene flysch, Carpathians, Poland

Fluctuations in the input of organic matter into a deep-sea environment can be deciphered from ichnofabrics if the continuous processes of hemipelagic sedimentation and bioturbation are episodically interrupted by turbidite deposition. Below turbidites, the bioturbated zone may be preserved almost intact; the benthic food content in such frozen tiers can be interpreted from the ethology, size, penetration depth, and density of trace fossils. Especially high benthic food content is characterized by (1) dark sediment color, (2) complete bioturbation, (3) high density of burrows produced near-surface in several levels, (4) rarity or absence of graphoglyptids, and (5) deep tiers completely bioturbated by feeding burrows having an open connection to the surface. Oxygen-deficiency can be eliminated as a reason for the black color of the sediment; the size, diversity, and penetration depth of the trace fossils are similar to that of modern and fossil counterparts formed under well-oxygenated settings that are not restricted in benthic food. An increase in sedimentation rate enhances the burial of benthic food and is indicated by the downward extension of the bioturbated zone and by increasing burrow density. Our analysis suggests that several other black shale occurrences may result from increased organic matter input rather than from water-column anoxia due to sluggish circulation. Our model is supported by similarities with other deposits that contain many frozen tiers.

The oldest deep-sea Ophiomorpha and Scolicia and associated trace fossils from the Upper Jurassic–Lower Cretaceous deep-water turbidite deposits of SW Bulgaria

Deep-sea trace fossils of the Nereites ichnofacies occur in the uppermost Kimmeridgian–Berriasian deep-water turbidite deposits of the Kostel Formation in SW Bulgaria. The trace fossil assemblage contains Tithonian Ophiomorpha isp. and Ophiomorpha annulata, which are the oldest deep-sea representatives of this ichnogenus. They indicate much older invasion of Ophiomorpha into deep-sea, which was hitherto dated as to mid-Cretaceous. It is not clear whether the invasion failed or Ophiomorpha survived in deep-sea refuge and became widespread after improving oxygenation of the deep seas after the Cenomanian/Turonian anoxic event. Tithonian Scolicia, produced by irregular echinoids, exhibits a similar distribution pattern.

Phanerozoic history of deep-sea trace fossils

Abstract The Phanerozoic diversity of deep-sea trace fossils, based on 151 flysch formations, displays distinct, non-linear changes through the Phanerozoic, with peaks in the Ordovician-Early Silurian and Early Carboniferous, lowered in the Permian-older Late Jurassic, a peak in the Tithonian-Aptian, lowered in the Albian, and the maximum in the Eocene. The contribution of graphoglyptids in trace fossil assemblages rises gradually up to the end of the Cretaceous, shows a peak in the Palaeocene-Eocene but a depression in the Oligocene. All the changes were probably influenced by competition for food and food supply, bottom water temperatures and oxygenation, and frequency of flysch habitats. There is no clear influence of major biotic crises (Ordovician/Silurian, Cretaceous/Tertiary, Palaeocene/Eocene) on the diversity of deep trace fossils, except the Eocene/Oligocene crisis.

Trends in diversity, frequency and complexity of graphoglyptid trace fossils: evolutionary and palaeoenvironmental aspects

Graphoglyptids, a characteristic component of the Nereites ichnofacies, are patterned, mainly meander-, star-, and net-shaped trace fossils, which reveal complex burrow systems used most likely for trapping of meiobenthos or cultivation of microbes in oligotrophic deep-sea environments. They show considerable changes of diversity, frequency and adaptive radiation through Phanerozoic. Rapid radiation and increase of their diversity and density in the Late Cretaceous, probably in the Turonian, is correlated with large-scale biotic changes in marine environments, which are rooted in palaeogeographic and palaeoclimatic changes. The changes of graphoglyptids have been distinctly caused by most of the major biotic crises, especially in the Cretaceous and Cenozoic. Graphoglyptids also display an increase of complexity, which accelerated in the Late Cretaceous, when the farming activity of their trace makers became more common. The distinct changes in development of graphoglyptids challenge the time-stability hypothesis for explanation of their evolution.

Revision of the ichnogenus sabellarifex richter, 1921 and its relationship to skolithos haldeman, 1840 and polykladichnus fürsich, 1981

Synopsis The trace fossil Sabellarifex Richter, 1921 is revised and a lectotype for the type ichno‐species, Sabellarifex eifliensis, is designated which unambiguously puts the ichnogenus Sabellarifex into synonymy with generally unbranched, vertical, tubular structures of the ichnogenus Skolithos Haldeman, 1840. Polykladichnus Fürsich, 1981, a vertically orientated trace fossil with upward‐directed Y‐ to U‐shaped branching, remains a valid ichnotaxon, although some specimens in the type series of Sabellarifex eifliensis also show this feature. Further use of Sabellarifex is not recommended. The potential value of ichnotaxobases for simple, tubular, vertically orientated trace fossils is discussed. Branching is considered an ichnotaxobase of high significance in simple, vertically orientated structures, thus relevant for ichnogeneric distinction. Wall‐lining is considered less important but suitable for ichnospecific differentiation. Funnel‐shaped apertures are not considered suitable ichnotaxobases in this case. This does not affect the classification of non‐tubular, plug‐ or funnel‐shaped structures such as Conichnus or Bergaueria. In the course of evaluating ichnotaxobases of simple, tubular, vertically orientated structures, Monocraterion Torell, 1870 is also revised. The morphology of the lectotype of Monocraterion tentaculatum clearly differs from Skolithos in showing radiating tubular structures. Their origin is unique and remains dubious hence Monocraterion should only be used for the type material. The palaeoecology of Skolithos and Polykladichnus is discussed. Marine Skolithos is best explained as a domichnion made by phoronids or annelids. Non‐marine Skolithos may be produced by insects or spiders; sculptured terminations of Skolithos have hitherto only been observed in non‐marine finds. If this may be diagnostic for all non‐marine Skolithos remains open. Marine Polykladichnus are best interpreted as domichnia of polychaetes or cerianthid anemones. Non‐marine Polykladichnus are most likely produced by insects or insect larvae.

Trace fossils after the K–T boundary event from the Agost section, SE Spain

Palaeogene trace fossils penetrate the uppermost Cretaceous sediments in the Agost section, Betic Cordillera, SE Spain. Chondrites ? targionii , Zoophycos isp., Planolites isp. A, Planolites isp. B, ? Thalassinoides isp. A, Thalassinoides isp. B, Thalassinoides isp. C, Alcyonidiopsis longobardiae , and Diplocraterion ? parallelum have been identified. A well-developed endobenthic tiering pattern is interpreted. The uppermost tier (A) represents major benthic activity in the shallowest sediments at or just below the seafloor, recorded as bioturbated background (only discrete rare Planolites ). The next upper tier (B) displays the highest trace-fossil diversity, with Planolites in the shallow levels, and Thalassinoides and Alcyonidiopsis at slightly deeper ones. The intermediate tier (C) contains randomly distributed Thalassinoides and Alcyonidiopsis , cross-cut by Zoophycos and large and medium-sized Chondrites . The deepest tier (D) contains Zoophycos , cross-cut by medium- and mainly small-sized Chondrites . Two interpretations are proposed: (1) vertical partitioning of a singled multi-tiered community under steady-stable conditions in well-oxygenated water bottom, reflecting gradual changes deep into the sediment, with decreasing oxygen pore water and benthic food, and increasing substrate consistency, and (2) sequential colonization and community replacement, reflecting the work of two successive communities. The first community, mainly represented by Planolites , Alcyonidiopsis and Thalassinoides , was produced in a shallow, oxygenated soft substrate. Probably related to decreasing oxygen content and benthic food availability, this community was replaced by deeply burrowing organisms that produced Zoophycos and Chondrites . This sequential colonization can be determined by changes in environmental parameters related to the Cretaceous–Palaeogene (K–T) event, or may have resulted from normal ecological and early diagenetic processes.

Deep-Sea Ichnology: Development of Major Concepts

SUMMARY: Invertebrate life on the deep-sea floor today and in the geological past is less-known than in lands and shallow seas. Complex paleo- and especially neoichnological research can help to better understand this hidden habitat. After several decades, deep-sea habitats are known to be diverse and complex at least in respect to oxygenation, trophic level, substrate variability, tiering pattern, distribution of tracemakers or mode of colonization. Deep-sea trace fossils also display long-term changes throughout the Phanerozoic, for instance in the diversity or contribution of graphoglyptids. For a comparison of largely increasing amount of data, a consistent and precise terminology and taxonomy are required, including an ichnotaxonomy based on the Linnaean system.

Deep-Sea Ichnology: The Relationships Between Depositional Environment and Endobenthic Organisms

Trace fossils and bioturbational structures are import ant component of deep-sea sediment fabric. Various ecological factors controlling distribution of their producers can be recognized Therefore, they curry important data on palaeoenvironmental parameters, such as mode of deposition, oxygenation, trophic level, bathymetry, rate of sedimentation, substrate consistency, direction of current flow and others. Trace fossils in turbiditic environment can be grouped in the pre- and post-depositional forms. They belong to the Zoophycos and Nereites ichnofacies. Within the latter, roughly, the Ophiomorpha rudis–Paleodictyon–Nereites ichnosubfacies may express a bathymetric trend from inner to outer deep-sea fan. Trace fossils were subjected to evolutionary processes influencing their producers. This is reflected in composition of trace fossil assemblages, overall changes in diversity and environmental shift of some individual ichnotaxa.

ICHNOFABRIC EVIDENCE FOR THE LACK OF BOTTOM ANOXIA DURING THE LOWER TOARCIAN OCEANIC ANOXIC EVENT IN THE FUENTE DE LA VIDRIERA SECTION, BETIC CORDILLERA, SPAIN

Abstract The early Toarcian (Early Jurassic) global marine mass extinction is usually related to the development of organic-rich sediments preserved as black shales and interpreted as a global oceanic anoxic event—the Toarcian Oceanic Anoxic Event (T-OAE). In the Betic Cordillera, southern Spain, the deep-marine Fuente de la Vidriera section contains the T-OAE as recorded at the westernmost part of the European Tethys. Ichnological analysis of the section indicates a relatively abundant and moderately diverse trace-fossil assemblage composed of Alcyonidiopsis isp., Chondrites isp., Nereites isp., Palaeophycus heberti, Planolites isp., Teichichnus isp., Thalassinoides isp., and Trichichnus linearis. A well-developed endobenthic multi-tiered community is characterized by an upper tier represented by homogenized sediment—individual burrows difficult to discern, a middle tier with a relatively diverse trace-fossil assemblage of mainly vagile deposit feeders, and a lower tier with activities of semisessile deposit feeders. The ichnoassemblage indicates oxic or slightly dysoxic bottom waters that were relatively favorable for benthic organisms. The absence of anoxia is confirmed by previously published geochemical and isotopic data. The T-OAE did not induce extreme conditions for macrobenthic organisms inhabiting the seafloor in this area of the westernmost Tethys. Local factors probably limited the influence of the anoxic event in bottom waters but may have induced oxygen deficiency in upper water masses, producing unfavorable living conditions for pelagic biota and, consequently, a sudden decrease in ammonite abundance.