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The Main Glauconite Bed (MGB) is a pelleted greensand located at Stone City Bluff on the south bank of the Brazos River in Burleson County, Texas. It was deposited during the Middle Eocene regional transgression on the Texas Gulf Coastal Plain. Stratigraphically it lies in the upper Stone City Member, Crockett Formation, Claiborne Group. Its mineralogy and geochemistry were examined in detail, and verdine facies minerals, predominantly odinite, were identified. Few glauconitic minerals were found in the green pelleted sediments of the MGB. Without detailed mineralogical work, glaucony facies minerals and verdine facies minerals are easily mistaken for one another. Their distinction has value in assessing paleoenvironments. In this study, several analytical techniques were employed to assess the mineralogy. X-ray diffraction of oriented and un-oriented clay samples indicated a clay mixture dominated by 7 and 14Å diffraction peaks. Unit cell calculations from XRD data for MGB pellets match the odinite-1M data base. Electron microprobe analyses (EMPA) from the average of 31 data points from clay pellets accompanied with Mössbauer analyses were used to calculate the structural formula which is that of odinite: Fe(3+) 0.89 Mg0.45 Al0.67 Fe(2+) 0.30 Ti0.01 Mn0.01) Σ = 2.33 (Si1.77 Al0.23) O5.00 (OH)4.00. QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) data provided mineral maps of quantitative proportions of the constituent clays. The verdine facies is a clay mineral facies associated with shallow marine shelf and lagoonal environments at tropical latitudes with iron influx from nearby runoff. Its depositional environment is well documented in modern nearshore locations. Recognition of verdine facies clays as the dominant constituent of the MGB clay pellets, rather than glaucony facies clays, allows for a more precise assessment of paleoenvironmental conditions.

The widespread mass extinctions at the end of the Cretaceous caused world-wide disruption of ecosystems, and faunal responses to the one-two punch of severe environmental perturbation and ecosystem collapse are still unclear. Here we report the discovery of in situ terrestrial fossil burrows from just above the impact-defined Cretaceous-Paleogene (K/Pg) boundary in southwestern North Dakota. The crisscrossing networks of horizontal burrows occur at the interface of a lignitic coal and silty sandstone, and reveal intense faunal activity within centimeters of the boundary clay. Estimated rates of sedimentation and coal formation suggest that the burrows were made less than ten thousand years after the end-Cretaceous impact. The burrow characteristics are most consistent with burrows of extant earthworms. Moreover, the burrowing and detritivorous habits of these annelids fit models that predict the trophic and sheltering lifestyles of terrestrial animals that survived the K/Pg extinction event. In turn, such detritus-eaters would have played a critical role in supporting secondary consumers. Thus, some of the carnivorous vertebrates that radiated after the K/Pg extinction may owe their evolutionary success to thriving populations of earthworms.

Paleodictyon is one of the most iconic and widespread of trace fossils in the geological record. However, modern examples are less well known and restricted to deep-sea settings at relatively low latitudes. Here, we report the distribution of Paleodictyon at six abyssal sites near the Aleutian Trench. This study reveals for the first time the presence of Paleodictyon at Subarctic latitudes (51°–53°N) and at depths over 4500 m, although the traces were not observed at stations deeper than 5000 m suggesting that there is some bathymetric constraint for the trace maker. Two small Paleodictyon morphotypes were recognized (average mesh size of 1.81 cm), one having a central hexagonal pattern, the other being characterized by a non-hexagonal pattern. Within the study area, Paleodictyon shows no apparent correlation with local environmental parameters. Finally, based on a worldwide morphological comparison, we conclude that the new Paleodictyon specimens represent distinct ichnospecies that are associated with the relatively eutrophic conditions in this region. Their smaller size may reflect this more eutrophic setting in which sufficient food can be obtained from a smaller area in order to satisfy the energetic requirements of the tracemakers. If so, then Paleodictyon size may provide some assistance when interpreting paleoenvironmental conditions.

Graphoglyptids are deep-marine trace fossils, often found preserved as casts in positive relief on the base of turbidites. Previous analyses of the behavioral evolution of graphoglyptids suggested they were slowly diversifying, becoming optimized, and getting smaller over time until the Late Cretaceous, when a sudden increase in diversification occurred. This current study quantifies the morphology of approximately 400 different graphoglyptid specimens, ranging in age from the Cambrian to the present, in order to evaluate the behavioral evolutionary interpretations made previously. Results from this study indicate that although some general evolutionary patterns can be discerned, they are not as straightforward as previously reported. Different topological categories of trace fossils represent organisms' responses to evolutionary pressures in unique ways. While burrow widths of meandering traces were becoming smaller over time, as predicted by previous workers, the burrow widths of the network traces were becoming smaller only until the Late Cretaceous, when they started to get larger again. The times of significant evolutionary changes in behavior were not consistent among various topological categories, with some morphological features being affected in the Late Cretaceous and others during the beginning of the Eocene. It is likely that the behavioral evolution of graphoglyptids was influenced by deep-marine global influences linked to climate change, glaciation, and deep-ocean warming. These influences affected each topological group uniquely, suggesting that different species or genera of trace makers were creating each of the topological categories. This is contrary to the hypothesis that all graphoglyptids were created by closely related species.

This study documents the association of glauconitic pellets and trace fossils at two Cambrian sites: the Reno Member, Lone Rock Formation, in southern Wisconsin and the Lion Mountain Member, Upper Riley Formation, in central Texas. Each site reflects a marine paleoenvironment on the Cambrian Laurentian margin rich in marine life that was affected by shifts in shoreline and wavebase. Both units contain abundant glauconitic fecal pellets, which were mixed with terrigenous quartz, and ichnofauna that characterize siliciclastic sublittoral marine environments of variable energy. This combination of ichnologic features is suggestive of multiphase depositional histories. Initial stages are represented by intense invertebrate feeding and pelletizing large quantities of seafloor sediment. Glauconitization of the pellets in relatively quiet-water environments represents intermediate stages. Burrowing of the units rich in relict glauconitic pellets in high-energy settings represents the final episode at each site. Findings demonstrate a major shift in benthic paleoecology in response to a changing paleoenvironment. The glauconitic pellets were sufficiently resistant to survive processes associated with a shallowing marine environment, as they were incorporated into primary sedimentary structures (ripplemarks and crossbeds) and biogenic structures (burrows). The combined ichnologic, mineralogic and sedimentologic observations offer insight for depositional interpretation.

The analysis of trace fossils usually is performed qualitatively, which makes comparing trace fossils from different units less objective than quantitative approaches. Quantifying the shape of trace fossils enables scientists to compare trace fossils described by different people with greater precision and accuracy. This paper describes several methods for quantifying invertebrate trace fossils, including morphology dependent methods (motility index, mesh size, topology, tortuosity, branching angle, and the number of cell sides) and morphology independent methods (fractal analysis, burrow area shape, and occupied space percentage (OSP)). These tools were performed on a select group of graphoglyptid trace fossils, highlighting the benefits and flaws of each analytical approach. Combined together, these methods allow for more objective comparisons between different trace fossils.

The Upper Triassic/Lower Jurassic Nugget Sandstone represents a portion of a vast inland erg of eolian sand dunes that were populated by diverse vertebrates and invertebrates, represented primarily by their trace fossils. Body fossils are rare, making the trace fossil record essential for deciphering the paleoecology of the ancient dune system. Trace fossils in the Nugget Sandstone near Vernal, Utah, include invertebrate burrows (Entradichnus meniscus, Entradichnus isp., Planolites beverleyensis, Taenidium isp. \"A\", Taenidium isp. \"B\", Skolithos, and Planolites isp., burrow clusters, large oblique burrows, flared burrows) and trackways (Paleohelcura and Octopodichnus). Arthropods (insects and arachnids) probably were the tracemakers of most, if not all, the trace fossils. Sediment moisture must have played a key role in the production and preservation of the trace fossils, indicating that moisture was important for supporting such complex ecosystems. Extended wet climatic intervals must have persisted intermittently between arid intervals. New fossil evidence for plants (sphenophytes, cycads, and algal buildups), ichnologic evidence of herbivorous insects and carnivorous arachnids, as well as indirect evidence for environmental moisture content during deposition of the Nugget Sandstone, provide a picture of the paleoecology of this ancient sea of sand.

Graphoglyptids are a group of deep-sea trace fossils that exhibit ornate burrow geometries. Feeding patterns represented by these burrows have been interpreted as fodinichnial (mining), pascichnial (grazing), and/or agrichnial (farming). In this study, several different graphoglyptid trace fossils were analyzed quantitatively using fractal analysis to determine which of these three feeding modes is most appropriate as an interpretation. Graphoglyptid burrows lend themselves to fractal geometric analysis, because they commonly exhibit the essential fractal characteristics of scale invariance and self similarity. Fractal analysis is presented as a tool for analyzing geometric configurations by combining shape complexity and space usage into one number, the fractal dimension. Fractal dimensions of such graphoglyptid burrows as Paleodictyon and Spirorhaphe were compared with those of known fodinichnial burrows, such as Zoophycos, and pascichnial trails, such as Scolicia, all from Zumaia, Spain. Results indicate that the deposit-feeding burrows (fodinichnia and pascichnia) illustrate a high fractal dimension, as would be expected for a deposit-feeding-optimal foraging strategy. Graphoglyptids illustrate a consistently lower fractal dimension than the deposit-feeding burrows, thus providing evidence against the suggestion that they represent fodinichnial or pascichnial behaviors. This observation supports the hypothesis that graphoglyptids represent agrichnial activity rather than mining or grazing activities.

Tiny sinuous trace fossils have been found within probable gut contents of an exceptionally preserved specimen of a hadrosaurid dinosaur, Brachylophosaurus canadensis, from the Judith River Formation of Montana. Approximately 280 examples of the trace fossils were observed in 19 samples of gut region material. The tubular structures typically are about 0.3 mm across. Many have thin calcareous linings or layers, and some exhibit fine surficial striae. At least two dozen of these trace fossils share walls with adjacent tubular traces, and this association can extend for several millimeters. While the trace fossils share some characteristics with fine rhizoliths, these features are most consistent with tiny burrows, or possibly body impressions, of worms (vermiform organisms) of uncertain biologic affinity. Such trace fossils have not been reported previously, and herein described as Parvitubulites striatus n. gen. n. sp. Either autochthonous (parasites) or allochthonous (scavengers) worms may have created the trace fossils, but taphonomic factors suggest that autochthonous burrowers are more likely. Several lines of evidence, such as constant diameters and matching directional changes, suggest that the paired trace fossils were made by two individuals moving at the same time, which implies sustained intraspecific contact. Parvitubulites striatus provides a rare record of interactions between terrestrial, meiofaunal-sized, soft-bodied invertebrates and a dinosaur carcass. The evidence that the worms may have parasitized a living hadrosaur and subsequently left traces of intraspecific behavior between individual worms adds unique information to our understanding of Mesozoic trophic interactions.

Bioglyphs are features in burrow or boring walls produced by such animal activity as scratching, drilling, plucking, gnawing, poking, and etching. Bioglyphs are important aspects to consider when making paleoethologic interpretations of trace fossils, because they can offer direct clues to understanding the mechanism of excavation of the trace fossil, the identity of the tracemaker, the purpose of the burrow or boring, and the character of the sediment in which the trace fossil has been produced.