Trace Makers Research Articles

A New Ichnospecies of Gyrolithes from the Austin Chalk, Upper Cretaceous, Texas, USA

ABSTRACTGyrolithes, a helical marine trace fossil, occurs in beds of the Austin Chalk near Waco, McLennan County, Texas. The new ichnospecies Gyrolithes texanus is characterized by unique morphology and wall construction. This discovery expands the current geographic and environmental range of Gyrolithes, extending this ichnogenus into the chalk-dominated beds of the Cretaceous of Texas. Irregular bedding features from the Gyrolithes locality indicate this section of the Austin Chalk was deposited within a storm-dominated depositional regime, interspersed with periods of quiescence which allow for firm ground formation and colonization by the trace maker. Occurrences of Gyrolithes have been associated by previous publications with marginal marine settings but not associated with storm deposits; therefore, this discovery constitutes an expansion of associated environment for this ichnogenus.

Beyond Coprinisphaera : fossil nests of dung beetles

Forty-two remains of fossil nests of dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae), which were recorded in four formations of the Cenozoic of South America, are described herein for the first time. Most of them are represented by nesting chambers containing a fossil brood ball (Coprinisphaera). However, in the most remarkable cases, parts of the burrows constructed by the parents and/or the vertical emergence burrows constructed by the offspring are preserved too. The preservation of the dung beetle nests is very unusual but more recurrent in younger formations probably because of the short-term action of the diagenetic processes. Considering that the construction of brood balls always involves the construction of nests, the ichnotaxonomical proposal is that the remains of fossil nests should be considered as ‘structures associated with Coprinisphaera’ and added to the diagnosis to avoid the proliferation of names. The study of the fossil nests provides new palaeoetological inferences for dung beetles, such as the Nesting Pattern of the trace makers of Coprinisphaera tonnii and Coprinisphaera akatanka, and how phylogenetically related were they with the extant necrophagous species of the genera Coprophanaeus and Canthon, respectively. Additionally, the fossil evidence suggests that simple nests of dung beetles predate compound nests.

Large dendrinids meet giant clam: the bioerosion trace fossil <i>Neodendrina carnelia</i> igen. et isp. n. in a <i>Tridacna</i> shell from Pleistocene–Holocene coral reef deposits, Red Sea, Egypt

Abstract. The rosette-shaped microboring trace fossil Neodendrina carnelia igen. et isp. n. – a large representative of the ichnofamily Dendrinidae – is identified on the inner side of the giant clam Tridacna maxima from Pleistocene to Holocene coral reef deposits of the El Quseir district at the Egyptian Red Sea coast. The new dendritic bioerosion trace fossil is diagnosed as a radial rosette comprised of a prostrate system of roofless canals that ramify in a strictly dichotomous fashion forming intermittent branches of uniform width and rounded terminations. The trace appears to be rare, although in the type material it occurs in a cluster of more than a hundred specimens. The location of traces on the interior surface of the shell suggests that boring occurred post-mortem to the host. Its record is presently restricted to shallow marine, euphotic, tropical coral reef settings in the Western Indo-Pacific (Red Sea and Madagascar). The biological identity of the trace maker cannot be resolved yet, but several lines of reasoning allow speculations directed towards a complex attachment scar, perhaps produced by a benthic foraminiferan or a macrophyte.

Hillichnus lobosensis, an unusually complex trace fossil of burrowing bivalves from the Paleogene of southern California, U.S.A.

Several specimens of the complex trace fossil Hillichnus lobosensis have been recovered from the Middle Eocene Scripps Formation in San Diego County, California. These specimens represent the second undoubted occurrence of the ichnospecies. This report extends the geographic range of the ichnospecies from central to southern California, the stratigraphic range from Late Paleocene to Middle Eocene, and the paleoenvironmental range from deep-water turbidite to shallow-marine nearshore settings. The San Diego specimens are the only known specimens of Hillichnus to be housed safely within a curated natural history collection (San Diego Natural History Museum), whereas the originally designated type specimens of H. lobosensis are subject to weathering and erosional processes at the type locality in Monterey County, California. The San Diego specimens also are important, because the trace fossils are the first of their ichnospecies that have been found in association with body fossils of the presumed bivalve (tellinacean) trace makers.

A new etching trace from the Savignone Conglomerate (Oligocene), NW Italy, probably produced by limpet gastropods

A new ichnogenus and ichnospecies ( Solealites ovalis ) of etching trace is preserved on the surfaces of clasts from the Savignone Conglomerate (Oligocene) in the Palaeogene Piemonte Basin in NW Italy. It is a shallow, oval depression with a central elevation, which was produced probably by limpet gastropods and served as their home scar, but other gastropods or even sea anemones are not excluded as the trace makers. The conglomerate is interpreted as a deposit of a fan delta, whose clasts have been bioeroded in an intertidal and shallow subtidal shore zone and redeposited to the deeper sea.

Large Camborygma isp. in fluvial deposits of the Lower Permian (Asselian) Dunkard Group, southeastern Ohio, U.S.A.

The lower Washington Formation of the Lower Permian (Asselian) Dunkard Group in southeastern Ohio contains large burrows exposed in cross section in a laterally discontinuous sandstone bed. This study examined the morphology of the burrows and their associated lithofacies to interpret the environmental conditions under which they were produced as well as the behavior and identity of the trace maker. Mudstone facies below and above the burrow-bearing sandstone consist of reddish-brown to variegated paleosols containing rhizohaloes, argillans, and large-scale slickensides, as well as thinly laminated, organic-rich shales containing plant fossils. The sandstone facies is 94–147cm thick, thinly bedded to massive, and fine- to medium-grained. The lithofacies are interpreted as deposits of crevasse splays, abandoned channels, and proximal to distal floodplains. Sixty burrows consist of vertical, subvertical, J-shaped, Y-shaped, and complex networks of branching shafts and tunnels. The burrows range from 5 to 180cm in length and 0.8–3.6cm in width. The main shaft's angles are typically ~90°, although are rarely 30–70°. Branching angles of subvertical and Y-shaped burrows vary from 0 to 90°. Many burrows extend to the top of the sandstone bed, but others turn into or out of the bed. The morphology of the burrows is most similar to Camborygma, known from continental deposits of the Permian to recent. While Camborygma has been previously reported from the Permian, this is the first occurrence in the Late Paleozoic Appalachian Basin extending its geographic range. The Dunkard burrows are similar to those of modern freshwater decapods, particularly crayfish. Decapod body fossils are not known from the Dunkard Group, yet these burrows are highly suggestive of their presence. Therefore, these fossil burrows contribute to the paleoecological interpretation of the Dunkard Group, helping to fill in gaps of the terrestrial fauna not otherwise preserved in the fossil record. Decapod burrow morphologies are highly variable depending on burrow function and environment. The Dunkard burrows are similar to secondary dwellings, with few open water attachments, multiple branches, and shafts likely extending to the water table.

Recent biogenic traces from the coastal environments of the southern Red Sea coast of Saudi Arabia

A neoichnological study was done at a site west of Abha on the southern Red Sea coast of Saudi Arabia. This area covers Wadi Hali and its surroundings (180 49′35.27″N: 410 22′44.23″E). The objective of the study is to document biogenic traces that occur in the upper intertidal ripple-marked sand flats and supratidal flats that include microbial mats, mud flats, and scattered patches of mangrove stands and their muddy environments. Based on morphological descriptions, four different kinds of burrows are identified and their fossil equivalents are Psilonichnus upsilon (burrow type 1), Cylindricum (burrow types 2 and 3), and Arenicolites (burrow type 4). Tracks of land hermit crabs Coenobita clypeatus are described as ichnospecies Coenobichnus currani. Gastropod grazing trails and their fossil equivalent Planolites is identified as well. Supratidal algal mats and their microscopic contents are presented. Fossil plant roots (rhizomes) are reported from a localized fluvial deposit from a dry channel (wadi). The morphology of the traces, trace maker, and ethology and the environmental setting indicate that the ichnofauna and botanical traces belong to the Psilonichnus ichnofacies.

The Impact of Hydrodynamics, Authigenesis, and Basin Morphology On Sediment Accumulation In An Upwelling Environment: The Miocene Monterey Formation At Shell Beach and Mussel Rock (Pismo and Santa Maria Basins, Central California, U.S.A.)

ABSTRACT: In the sections at Shell Beach (Pismo Basin) and Mussel Rock (Santa Maria Basin)—both along the central California coast—the Miocene Monterey Formation is composed of laminated, biosiliceous, organic-rich and phosphate-rich sediments, which are intercalated with carbonates and volcanogenic deposits. The presence of small- and large-scale scours, conglomerates, gravity-flow deposits, slumps, and condensed intervals reveals the importance of sediment reworking, which is related to the presence of bottom currents, the general morphology of the basins, and recurrent high-energy events of likely seismic origin. The lithologies reflect strong upwelling, enhanced primary productivity, and the presence of an oxygen-minimum zone, which is indicated by ubiquitous lamination, a general absence of bioturbation (with the rare exception of traces related to the gravity-flow displacement of trace makers), high pyrite, Mo, and U concentrations, and molar ratios of total organic carbon and organic phosphorus (TOC/P org ) of up to 2000. Oxygen depletion was particularly severe during the early Langhian, and the late Serravallian and early Tortonian, and favored the preservation of organic matter. Episodes of deposition of organic-rich sediment were followed by longer phases of subdued sediment accumulation and early diagenetic phosphogenesis, which resulted in the formation of a low-porosity, less permeable “lid” in the near-surface sediments that assisted in preserving organic matter. Phosphogenesis occurred throughout the time interval considered (approximately 17.5–6.5 Ma), and phosphate-rich sediments formed especially during periods of sedimentary condensation in the Langhian and earliest Serravallian, and the latest Tortonian and early Messinian. A comparison of temporal trends in the type and quantity of deposited sediments between the two sections at Shell Beach and Mussel Rock, and three sections of the Santa Barbara Basin (El Capitan State Beach, Naples Beach, and Haskell Beach) confirms that towards the top of the Monterey Formation, sediments become enriched in biosilica in all three basins. The transition into this lithology occurred diachronously, during the Serravallian in the Pismo and Santa Maria basins and Tortonian in the Santa Barbara Basin, and was probably related to a diachronous shift to more intense upwelling in all three basins. A phase of important condensation and phosphogenesis terminated Monterey-“type” sedimentation during the latest Tortonian and early Messinian in both the Santa Maria and Santa Barbara basins. The uniform expression of this phase is interpreted as the result of improved connections between the two basins.

A tetrapod swimming traceway from the Triassic of Winterswijk, the Netherlands

AbstractWe describe a tetrapod swimming traceway from the Middle Triassic Vossenveld Formation of the Netherlands. Forty-five individual traces, each consisting of two parallel claw drag marks, were followed over 9 m in a roughly east–west direction. The asymmetry of the traceway geometry indicates the trace maker negotiated a lateral current. The trace maker could not be identified, but the traces described here are markedly different fromDikoposichnustraces attributed to swimming nothosaurs.

The Faraoni event (latest Hauterivian) in ichnological record: The Río Argos section of southern Spain

The Early Cretaceous (latest Hauterivian) Faraoni Oceanic Anoxic Event (F-OAE) in the Río Argos section (Caravaca region, southern Spain), the candidate for the Global Boundary Stratotype Section and Point (GSSP) of the Hauterivian–Barremian transition, has been studied. Its ichnological bed-by-bed analysis allows for interpretation of oxygenation changes through the Faraoni Level interval and improvement upon previous characterization of oxygen conditions prior, during and after the F-OAE. The trace fossil assemblage belongs to the Zoophycos ichnofacies and it includes Chondrites intricatus, Chondrites targionii, Halimedides isp., Palaeophycus isp., ?Patagonichnus isp., Planolites isp., Rhizocorallium isp., Taenidium isp., Thalassinoides isp., Trichichnus linearis, Zavitokichnus fusiformis, and Zoophycos isp. Their diversity in particular beds fluctuates. Beds with four to six ichnotaxa reflect a multi-tiered macrobenthic trace maker assemblage living in good oxic and trophic conditions. In one bed below and one bed above the Faraoni Level (both marls without primary lamination), there are only two or three, mostly opportunistic ichnotaxa (Trichichnus, Chondrites, Planolites). They record dysoxic conditions. At the base of the Faraoni Level, one thicker and two thinner beds of marly mudstones (21.2 and 3.5 cm thick, respectively) are characterized by primary lamination. At the top and in the basal part of the thicker bed and in the thinner beds some trace fossils are present. These beds were deposited under anoxic conditions and later colonized by trace makers either from overlying beds deposited under oxic conditions or from the level of a greenish lamina in the lower part of the thicker bed, recording short episodes of dysoxic conditions. The thinner anoxic beds are separated by marls deposited under dysoxic conditions.

Classical and new bioerosion trace fossils in Cretaceous belemnite guards characterised via micro-CT

Abstract. The ongoing technical revolution in non-destructive 3-D visualisation via micro-computed tomography (micro-CT) finds a valuable application in the studies of bioerosion trace fossils, since their three-dimensional architecture is hidden within hard substrates. This technique, in concert with advanced segmentation algorithms, allows a detailed visualisation and targeted morphometric analyses even of those bioerosion traces that are otherwise inaccessible to the widely applied cast-embedding technique, because they either are filled with lithified sediment or cement or are preserved in inherently insoluble or silicified host substrates, or because they are established type material and should not be altered. In the present contribution selected examples of such cases are illustrated by reference to bioerosion trace fossils preserved in Late Cretaceous belemnite guards from the European Chalk Province. These case studies comprise an analysis of a diverse ichno-assemblage found associated with the lectotype of the microboring Dendrina dendrina (Morris, 1851) in a belemnite from the upper Campanian to lower Maastrichtian chalk of Norfolk, England, and the description of two new bioerosion trace fossils with type specimens found in belemnite guards from the lower Campanian limestones of Höver, Germany. The latter are Lapispecus hastatus isp. n., a tubular and occasionally branched macroboring for which a sipunculan or a phoronid trace maker are discussed, and Entobia colaria isp. n., a camerate network formed by an excavating sponge that eroded diagnostic grated apertures at the locations of the presumed inhalant papillae or exhaling pores, adding to or replacing filtering devices that are otherwise made of tissue and spicules. As an added value to the non-destructive visualisation procedure, the processed X-ray micro-CT scans of the studied type material provide 3-D models that may now serve as digitypes that can be studied as digital facsimile without the necessity of consulting the actual type specimens.

A new trace fossil assemblage from the Middle Permian Broughton Formation, southern Sydney Basin (southeastern Australia): Ichnology and palaeoenvironmental significance

The Permian-Triassic sedimentary succession of the southern Sydney Basin in southeastern Australia contains a wealth of well-preserved trace fossils that are important for systematic ichnological, palaeoecological, and palaeoenvironmental interpretations. In this study, a new ichnofossil assemblage comprising Macaronichnus, Palaeophycus, Psammichnites, Protovirgularia, Rosselia, and Teichichnus is documented from the tide-influenced shoreface deposit of the Middle Permian Jamberoo Sandstone Member of the Broughton Formation. Two distinct ichnofabrics are recognized: i) the Psammichnites ichnofabric characteristic of the upper–middle shoreface deposit; and ii) the crowded Rosselia ichnofabric (CRI) representing the lower shoreface. The Psammichnites-dominated ichnofabric is interpreted to have resulted from opportunistic behaviours of unknown trace makers, whereas the CRI is interpreted to represent possible strategic behaviours of stress-tolerant polychaetes (e.g., terebellid, spionid, and cirratulid polychaetes) in a distal shoreface with high sedimentation rate. Thus, the Psammichnites–crowded Rosselia ichnofabric succession can be considered to represent a response to an environmental shift from proximal to distal shoreface. As such, this study highlights the utility of these two ichnofabrics as stressed environmental indicators.

Beyond the stony veil: Reconstructing the Earth’s earliest large animal traces via computed tomography X-ray imaging

Trace fossils are superb lines of evidence for examining the ancient biologic world because they offer an opportunity to infer behavioral ecology of organisms. However, traces can be difficult to parse from their matrix, which leads to the loss of important morphological and behavioral data. This is especially true for the earliest marine animal traces from the Ediacaran Period (635–541Ma), which are usually small (<5mm in diameter) and simple (mostly small horizontal trails and burrows), and are sometimes difficult to be distinguished from co-existing tubular body fossils. There is also evidence that the prevalence of microbial substrates in Ediacaran oceans may have influenced emerging trace makers in non-actualistic ways from a late Phanerozoic perspective (e.g., microbial mats may have facilitated a strong geochemical gradient across the sediment-water interface). Therefore, the discovery of the relatively large traces of Lamonte trevallis from the Ediacaran Shibantan Member of the Denying Formation (∼551–541Ma) in the Yangtze Gorges area of South China provides a unique opportunity to study early bioturbators. These trace fossils are large enough and have sufficient compositional contrast (relative to the matrix) for in situ analysis via X-ray computed tomography (CT) and microcomputed tomography (microCT). Each analytical method has its own advantages and disadvantages. CT scans can image larger specimens, but cannot adequately resolve small features of interest. MicroCT scans can achieve higher resolution, but can only be used with small samples and may involve more post-processing than CT scans. As demonstrated in this study, X-ray CT and microCT in combination with other 3D imaging techniques and resources have the potential to resolve the 3D morphology of Ediacaran trace fossils. A new Volumetric Bioturbation Intensity (VBI) is also proposed, which quantifies whole rock bioturbation using 3D analysis of subsurface traces. Combined with the ability to examine trace fossils in situ, the VBI can enhance our view of ancient ecologies and life’s enduring relationship with sediments.

Reniformichnus katikatii (New Ichnogenus and Ichnospecies): Continental Vertebrate Burrows from the Lower Triassic, Main Karoo Basin, South Africa

ABSTRACTThe formal ichnotaxonomic assignment of a new ichnogenus and ichnospecies, Reniformichnus katikatii, is presented based on the holotype and several field specimens from the Lower Triassic Katberg Formation in the main Karoo Basin of South Africa. The holotype is an inclined, burrow cast with bilobate base and reniform cross-section. Its width ranges from 12.6 to 14.7 cm, and its height is 5 to 7.4 cm resulting in an aspect ratio of 1.89 to 2.74. The surface preserves 70–180 mm long ridges running parallel to the long axis of the burrow on the upper parts of the walls and lower parts of the dorsum and shorter ridges (average length ∼27 mm) are preserved on the more ventral areas in two opposite orientations, cross-cutting each other in a rhomboid pattern. Burrow fills are passive and consist of slightly bedded, laminated, or massive clastic rocks that are coarser than the host mudstones. The burrow casts are isolated, never occurring in clusters. This simple burrow shows no evidence for branching, spiralling, interconnected tunnels, burrow linings, terminal chambers, or entrances. Preserved in fluvial floodplain mudstone units, the burrows were passively filled by layered, laminated, or massive sand and other coarser clastic sediments. The burrow casts are morphologically similar to unnamed Antarctic ichnotaxa that have been attributed to tetrapods (e.g., therapsids, procolophonids), extending the geographic range of the potential producers of Reniformichnus isp. to continental settings in southern Gondwana. Biostratigraphic evidence on the temporal distribution of Reniformichnus isp. suggests that the trace maker emerged in the aftermath of the Permo-Triassic mass extinction event to successfully burrow throughout the Early Triassic.

Outcrop and core integrative ichnofabric analysis of Miocene sediments from Lepe, Huelva (SW Spain): Improving depositional and paleoenvironmental interpretations

Ichnofabric analysis was conducted in Miocene sediments from Lepe (Huelva, SW Spain) based on integrative outcrop and core research, to improve interpretations of depositional and paleoenvironmental conditions, with special attention to sequence stratigraphy. Seven intervals were differentiated in outcrops based on stratigraphic and ichnological features, consisting of two ichnofabrics: Ophiomorpha-Thalassinoides-Spongeliomorpha ichnofabric characterizes intervals 1, 2, 6, 7 and 8, while Palaeophycus-Planolites-Phycosiphon ichnofabric characterizes intervals 3, 4 and 5. Fourteen ichnofabrics were differentiated in the core, mainly in view of lithological features, including ferruginous material, grain size, mottled background, ichnotaxa, and Bioturbation Index. A comparison between outcrop and core ichnofabrics through the upper 13.5m, corresponding to the uppermost Tortonian-lowermost Messinian interval, revealed certain similarities as well as some differences. A continuous and relatively slow siliciclastic deposition with punctual variations in the sedimentation rate can be interpreted that, associated with favorable paleoenvironmental parameters such as aerobic conditions and nutrient availability, evidence that a well-developed and diverse macroinvertebrate trace maker community existed at that time. Softgrounds are dominant, but occasionally loosegrounds and even firmgrounds could develop. The ichnofabric distribution shows long-range patterns in outcrop and core, and short-range patterns exclusively in core. Long-range patterns reflect the last phases of a transgressive system tract, with a “maximum flooding zone” at the end, and then a highstand normal regression. High-frequency, short-range, repetitive patterns in ichnofabrics from core, mainly between ichnofabrics 6/8 to 9 from lower to upper part of the pattern, can be linked to “local flooding surfaces”, subdividing the “maximum flooding zone” into parasequences. Our results reveals the usefulness of the integrative ichnofabric analysis, including outcrop and core materials, in sedimentary basin analysis, assessing paleoenvironmental conditions and improving sequence stratigraphy characterization.

Life beneath ammonite shells – A unique Late Cretaceous habitat for the trace maker of Chondrites and its impact on taphonomy of the shells

In a unique middle Campanian horizon at Rzeżuśnia, southern Poland, the trace fossil Chondrites occurs densely and preferentially on the lower side of horizontally oriented ammonite moulds but it is absent in the surrounding sediment and on the upper side of the moulds. The ammonite shells created an ideal microenvironment for the Chondrites trace maker, with a higher organic matter content and shallower redox boundary than in the sediment outside the shells. Detailed microscopic (microfacies, SEM, CL and XRD) analyses revealed different taphonomic histories of shell for the upper and lower side of the ammonite specimens. Probably, the chemosymbiotic worm-like trace maker uses the burrow tunnels for pumping the hydrogen sulfide-rich water. This changes the pH of pore water only below the horizontally lying ammonite shells and enabled the aragonite dissolution. Slower rate of sedimentation in combination with downward migration of geochemical zones cause iron sulfide oxidation, calcite cement precipitation and glauconitization.

Canid Coprolites from the Late Pleistocene of Hidalgo, Central Mexico: Importance for the Carnivore Record of North America

ABSTRACTWe present the first reported occurrence of canid coprolites from the late Pleistocene of central Mexico. The sample consists of five associated coprolites recovered from Quaternary deposits that crop out in southeastern Hidalgo, central Mexico. The material shows several of the typical features of canid feces, including elongated cylindrical shape, uncommon and nondistinct constrictions, and one tapered end. The coprolites are similar in size to feces of North American foxes, such as Vulpes macrotis, V. lagopus, V. vulpes, and Urocyon cinereoargenteus; likewise, their size might be comparable to those of the Pleistocene canid Canis cedazoensis. The content of the studied coprolites consists of numerous teeth and bone fragments referable to the pocket gophers Pappogeomys or Cratogeomys. The coprolite content is related to a mostly carnivorous diet comparable to that of C. cedazoensis, wolves (Canis lupus, C. rufus, and C. dirus), and some foxes (V. macrotis and V. velox). As a result, it is proposed that the potential trace maker of the coprolites could be a form similar to a carnivorous fox or a small dog. These trace fossils represent the first indirect evidence of canids in the late Pleistocene of Hidalgo and provide additional information regarding the geographic distribution of the Canidae in temperate areas of North America that now are part of central Mexico during the second half of the Pleistocene.

Middle Jurassic tetrapod burrows preserved in association with the large sauropod Omeisaurus jiaoi from the Sichuan Basin, China

Here we report a Jurassic tetrapod burrow preserved in association with the partial skeleton of a large sauropod specimen of Omeisaurus jiaoi from Zigong, Sichuan Province, China. The ichnofossil can be divided into two parts, which may indicate two individual trace makers and some social behavior, although the possibility that they are two portions of one trace by a single trace maker cannot be ruled out. The burrow trace was examined via petrographic thin sections and carbonate analysis. Considering the spatial relationship of the burrows and the skeleton, it is likely that decomposition of the sauropod carcass preceded the formation of the burrows. It is possible that the process of decomposition improved the humus level of the soil, which would have attracted more soil-dwelling invertebrates and, by consequence, tetrapod predators thereof. The discovery of ZDM5051 has increased our understanding of global ichnofossil diversity.

Evaluating macrobenthic response to the Cretaceous–Palaeogene event: A high-resolution ichnological approach at the Agost section (SE Spain)

The Agost section (Betic Cordillera, Alicante Province, south-eastern Spain) is one of only a few places in the world where complete sedimentary successions across the Cretaceous–Palaeogene (K–Pg) boundary are available. Agost enables a high-resolution ichnological analysis illustrating the influence of environmental perturbations on burrowing organisms before, during and after the K–Pg boundary event. The uppermost Maastrichtian calcareous marlstones and marly limestones of the Raspay Formation (Plummerita hantkeninoides Biozone), beside the light-filled Maastrichtian trace fossils, contain dark-coloured early Danian trace fossils including Chondrites targionii, Chondrites ?affinis, Chondrites isp., Pilichnus isp., Planolites isp., ?Teichichnus isp., Thalassinoides isp., Trichichnus linearis, Trichichnus isp., and Zoophycos isp. The ichnotaxonomic composition of the late Maastrichtian and early Danian trace fossil association does not reveal major differences, indicating no significant influence on composition of their trace makers immediately after the K–Pg event. The main factors that most likely promoted survivorship of the trace makers were their feeding strategy (deposit feeders, microbe gardeners) and an increased delivery of organic matter to the seafloor due to the high mortality during the K–Pg boundary event. However, the differences in the size of trace fossils are noted: They are distinctly smaller in the dark boundary layer (Guembelitria cretacea Biozone) than in the underlying uppermost Maastrichtian calcareous marlstones. This is an example of the Lilliput Effect. The dwarfed ichnoassociation was produced during and shortly after sedimentation of the dark boundary layer pointing to a delayed reaction of the burrowing organisms to the K–Pg boundary event compared to other groups of organisms. The dwarfing might be caused by environmental stress resulting from lower food supply due to collapse of primary production in the later phases of the K–Pg boundary event.

ENIGMATIC CONTINENTAL BURROWS FROM THE EARLY TRIASSIC TRANSITION OF THE KATBERG AND BURGERSDORP FORMATIONS IN THE MAIN KAROO BASIN, SOUTH AFRICA

Abstract: An Early Triassic continental ichnofossil assemblage dominated by ∼ 4 cm diameter burrow casts was discovered in the transitional zone of the Katberg and Burgersdorp formations in the SE main Karoo Basin (Eastern Cape, South Africa). Analyses of the burrow architecture and associated sedimentary facies aim to identify the possible trace makers, their behavior, and the local depositional conditions in the Olenekian (Early Triassic) in this part of Gondwana. The burrows were excavated into a floodplain where alternating periods of flooding, drying, and pedogenesis occurred, a set of conditions often mentioned for the Lower and Middle Triassic continental deposits in southern Gondwana. However, the burrow architecture and superficial morphology are distinct from previously reported older and younger burrows in this part of Pangea. These burrows are simple vertical shafts that are occasionally J-shaped with a circular to slightly elliptical cross-section (average aspect ratio 1.2), ∼ 4 cm in diamete...