Jon J. Smith

Naktodemasis bowni: New Ichnogenus and Ichnospecies for Adhesive Meniscate Burrows (AMB), and Paleoenvironmental Implications, Paleogene Willwood Formation, Bighorn Basin, Wyoming

Abstract Adhesive meniscate burrows (AMB) are common in alluvial paleosols of the Paleogene Willwood Formation, Bighorn Basin, Wyoming. AMB are sinuous, variably oriented burrows composed of a nested series of distinct, ellipsoidal packets containing thin, tightly spaced menisci subparallel to the bounding packet. Menisci are non-pelleted and texturally homogeneous with each other and the surrounding matrix. AMB were constructed most likely by burrower bugs (Hemiptera: Cydnidae), cicada nymphs (Hemiptera: Cicadae), and less likely by scarabaeid (Coleoptera: Scarabaeidae) or carabid beetles (Coleoptera: Carabidae), based on burrow morphology and comparison to similar structures produced by these organisms in modern soils. Extant burrowing insects excavate backfilled burrows in well-rooted A and upper B horizons of soils generally below field capacity depending on soil type. This study demonstrates that AMB are distinct morphologically from such previously described ichnofossils as Beaconites, Laminites, Scoyenia, Taenidium, and Ancorichnus. Naktodemasis bowni, a new ichnogenus and ichnospecies, represents burrows composed of nested ellipsoidal packets backfilled with thin, tightly spaced, menisci subparallel to the bounding packet. The presence of N. bowni indicate periods of subaerial exposure associated with pedogenic modification under moderately to well-drained soil conditions, or during periods of better drainage in imperfectly drained soils. N. bowni, therefore, can differentiate alluvial paleoenvironments from marine and lacustrine paleoenvironments, as well as periods of subaerial exposure of sediments deposited in aquatic settings.

Traces and burrowing behaviors of the cicada nymph Cicadetta calliope: Neoichnology and paleoecological significance of extant soil-dwelling insects

Abstract This study documents the traces and burrowing behaviors of nymphs of the prairie cicada Cicadetta calliope (Hemiptera: Cicadidae), as observed in neoichnological experiments. Cicada nymphs were collected from the C horizons of sandy Fluvents along the Kansas River east of Lawrence, Kansas. The nymphs appeared to be fifth instars, 13–17 mm long and 6–7 mm wide. Nymphs were placed in plastic enclosures containing layers of colored, moist, very fine-grained sand. They burrowed immediately, excavating air-filled, sediment-enclosed cells between 20 mm and 40 mm long and averaging 9 mm wide. Burrowing was completed in three stages: (1) sediment in the forward portion of the cell was excavated and rolled into a ball with the forelimbs; (2) the nymph turned 180° using a forward roll, and moved to the back of the cell; and (3) the sediment ball was pushed up against the back wall of the cell and kneaded with the forelimbs into a thin layer. Resulting burrow traces are sinuous and distinctly meniscate and demonstrate that insect larvae construct meniscate, backfilled burrows in well-drained terrestrial settings. Cicadetta calliope nymphs and their traces are excellent analogs for meniscate trace fossils commonly found in late Paleozoic–Cenozoic alluvial deposits and paleosols. Such meniscate trace fossils are useful for interpreting the paleoenvironment and paleohydrogeology of the units in which they are found. In addition, such backfilled burrows can be used to supplement the fossil record of cicada-like hemipterans, currently known only from the latest Permian to the Early Triassic.

Relationship of Floodplain Ichnocoenoses to Paleopedology, Paleohydrology, and Paleoclimate in the Willwood Formation, Wyoming, During the Paleocene–eocene Thermal Maximum

Abstract Vertical changes in distribution, abundance, and ichnodiversity of ichnocoenoses in alluvial deposits of the Willwood Formation suggest significantly drier moisture regimes in the Bighorn Basin, Wyoming, during the Paleocene–Eocene Thermal Maximum (PETM), a transient period of global warming. The Willwood Formation at Polecat Bench contains an abundant assemblage of ichnofossils, including various types of rhizoliths and invertebrate trace fossils, such as Naktodemasis bowni, Camborygma litonomos, Edaphichnium lumbricatum, cf. Cylindricum isp., cf. Planolites isp., cf. Steinichnus, and cocoon traces. These comprise six distinct ichnocoenoses, which are categorized as dominantly terraphilic, hygrophilic, or hydrophilic based on the inferred moisture regimes of their most abundant ichnofossil morphotypes and associated pedogenic features, including other trace fossils and rhizoliths. The interpreted moisture regimes correlate well with the paleoenvironments of their host lithofacies, as inferred from sedimentology and paleopedology. Outside the PETM interval at Polecat Bench, abundant avulsion deposits and thin, compound paleosols containing hygrophilic and hydrophilic ichnocoenoses suggest frequent depositional events and predominantly poor to imperfect soil-drainage conditions. Within the PETM interval, thick, cumulative paleosol profiles with abundant terraphilic to hygrophilic ichnocoenoses suggest significantly improved drainage conditions. Lithofacies and ichnocoenoses above the PETM interval are not significantly different from those below the interval, indicating a return to pre-PETM moisture regimes. These conclusions support previous studies that suggest the Bighorn Basin experienced transient drying during this interval. This study demonstrates that ichnocoenoses and their ichnopedologic associations can be used to refine paleohydrologic and paleoclimatic generalizations inferred from paleoclimate models.

Transient dwarfism of soil fauna during the Paleocene-Eocene Thermal Maximum

Soil organisms, as recorded by trace fossils in paleosols of the Willwood Formation, Wyoming, show significant body-size reductions and increased abundances during the Paleocene–Eocene Thermal Maximum (PETM). Paleobotanical, paleopedologic, and oxygen isotope studies indicate high temperatures during the PETM and sharp declines in precipitation compared with late Paleocene estimates. Insect and oligochaete burrows increase in abundance during the PETM, suggesting longer periods of soil development and improved drainage conditions. Crayfish burrows and molluscan body fossils, abundant below and above the PETM interval, are significantly less abundant during the PETM, likely because of drier floodplain conditions and lower water tables. Burrow diameters of the most abundant ichnofossils are 30–46% smaller within the PETM interval. As burrow size is a proxy for body size, significant reductions in burrow diameter suggest that their tracemakers were smaller bodied. Smaller body sizes may have resulted from higher subsurface temperatures, lower soil moisture conditions, or nutritionally deficient vegetation in the high-CO2 atmosphere inferred for the PETM. Smaller soil fauna co-occur with dwarf mammal taxa during the PETM; thus, a common forcing mechanism may have selected for small size in both above- and below-ground terrestrial communities. We predict that soil fauna have already shown reductions in size over the last 150 years of increased atmospheric CO2 and surface temperatures or that they will exhibit this pattern over the next century. We retrodict also that soil fauna across the Permian-Triassic and Triassic-Jurassic boundary events show significant size decreases because of similar forcing mechanisms driven by rapid global warming.

Manganese-bearing rhizocretions in the Willwood Formation, Wyoming, U.S.A.: implications for paleoclimate during the Paleocene-Eocene Thermal Maximum

ABSTRACT Changes in the stratigraphic distribution of manganese (Mn)-bearing columnar structures interpreted as rhizocretions indicate a shift in paleohydrological conditions in the Bighorn Basin during the Paleocene–Eocene Thermal Maximum (PETM). While most studies agree that significant warming occurred during the PETM, interpretations differ as to the effects of warming on the paleohydrologic regime. The columns consist of sand and silt cemented by calcite that also contains black, Mn-bearing nodules. The rhizocretions are typically vertically oriented and range from a few cm to over 50 cm in diameter and up to 75 cm tall. They are interpreted to have formed in the rhizospheres of relatively large root systems. The rhizocretions are restricted to intervals, showing only weak paleopedogenic development, that are interpreted as crevasse-splay or avulsion deposits. While such deposits are present throughout the study section at Polecat Bench in the northern Bighorn Basin, Wyoming, the Mn-bearing rhizocretions are found only below and above the PETM interval and within the initial carbon isotope excursion (CIE) marking the onset of the PETM. The abundance of black, Mn-rich nodules (< 1 cm in diameter) in the rhizocretions and presence of other pedogenic features indicate that the soils in which the plants were growing underwent seasonal flooding and repeated redox alternations. Their distribution in similar host deposits throughout the study interval, except for the main body of the PETM, supports climate as the driving factor in preservation of the Mn-bearing rhizocretions. The Mn-bearing rhizocretions support recent studies that suggest transient drying in northern Wyoming during the PETM.

Experimental Approaches to Understanding Fossil Organisms

Part I Functional Morphology 1. Crinoids Aweigh: Experimental Biomechanics of Ancyrocrinus Holdfasts Roy E. Plotnick and Jennifer Bauer 2. Ultra-elongate freshwater pearly mussels (Unionida): Roles for function and constraint in multiple morphologic convergences with marine taxa Laurie C. Anderson 3. Relationships of Internal Shell Features to Chemosymbiosis, Life Position, and Geometric Constraints within the Lucinidae (Bivalvia) Laurie C. Anderson 4. Modern Analogs for the Study of Eurypterid Paleobiology Danita S. Brandt and Victoria McCoy 5. New Applications for Constrained Ordination: Reconstructing Feeding Behaviors in Fossil Remingtonocetinae (Cetacea: Mammalia) Lisa Noelle Cooper, Tobin L. Hieronymus, Christopher J. Vinyard, Sunil Bajpai, and J.G.M. Thewissen Part II Taphonomy and Environment 6. Patterns in Microbialites Throughout Geologic Time: Is the Present Really the Key to the Past? Kristen L. Myshrall, Christophe Dupraz, Pieter T. Visscher 7 The Relationship Between Modern Mollusk Assemblages and their Expression in Subsurface Sediment in a Carbonate Lagoon, St. Croix, U.S. Virgin Islands Karla Parsons-Hubbard, Dennis Hubbard, Caitlin Tems, and Ashley Burkett 8. Biotic Segregation In An Upper Mesotidal Dissipative Ridge And Runnel Succession, West Salish Sea, Vancouver Island, British Columbia John-Paul Zonneveld, Murray K. Gingras, Cheryl A. Hodgson, Luke P. McHugh, Reed A. Myers, Jesse A. Schoengut, and Bryce Wetthuhn 9. Using X-ray Radiography to Observe Fe distributions in Bioturbated Sediment Murray K. Gingras, John-Paul Zonneveld, and Kurt O. Konhauser 10. Phytoliths as Tracers of Recent Environmental Change Ethan G. Hyland Part III Organism-Substrate Interaction 11. Large Complex Burrows of Terrestrial Invertebrates: Neoichnology of Pandinus imperator (Scorpiones: Scorpionidae) Daniel I. Hembree 12. Biomechanical Analysis of Fish Swimming Trace Fossils (Undichna): Preservation and Mode of Locomotion Maria Cristina Cardonattoand Ricardo Nestor Melchor 13. The Neoichnology of Two Terrestrial Ambystomatid Salamanders: Quantifying Amphibian Burrows Using Modern Analogues Nicole D. Dzenowski and Daniel I. Hembree 14. Biogenic Structures of Burrowing Skinks: Neoichnology of Mabuya multifaciata (Squamata: Scincidae) Angeline Catena and Daniel I. Hembree 15. Novel Neoichnology of Elephants: Nonlocomotive Interactions with Sediment, Locomotion Traces in Partially Snow-Covered Sediment, and Implications for Proboscidean Paleoichnology Brian F. Platt and Stephen T. Hasiotis 16. Burrows and Related Traces in Snow and Vegetation Produced by the Norwegian Lemming (Lemmuslemmus) Dirk Knaust 17. Near-Surface Imaging (GPR) of Biogenic Structures in Siliciclastic, Carbonate, and Gypsum Dunes Ilya V. Buynevich, H. Allen Curran, Logan A. Wiest, Andrew P.K. Bentley, Sergey V. Kadurin, Christopher T. Seminack, Michael Savarese, David Bustos, Bosiljka Glumac, and Igor A.Losev

PALEOENVIRONMENTAL AND PALEOGEOGRAPHIC IMPLICATIONS OF PALEOSOLS AND ICHNOFOSSILS IN THE UPPER PENNSYLVANIAN HALGAITO FORMATION, SOUTHEASTERN UTAH

Abstract The Upper Pennsylvanian (Virgilian) Halgaito Formation (HF) is an ∼ 125–155-m-thick succession of carbonate and carbonate-cemented siliciclastic strata exposed along Cedar Mesa on the Colorado Plateau in southeastern Utah. Defining the stratigraphic standing of the HF has been problematic due to differing paleoenvironmental and paleogeographic interpretations. This stratigraphic confusion is likely because the HF and overlying Cedar Mesa Sandstone lie at the interface between the underlying, predominately marine carbonate Honaker Trail Formation and the overlying, alluvial-eolian Organ Rock Formation. This study uses a combined ichnological, paleopedological, and sedimentological approach to refine the paleoenvironmental and paleogeographic history of the HF. The lower, marine portion of the HF is predominately fossiliferous packstone and calcareous sandstone, containing abundant Scalichnus and Thalassinoides. Marine sandstone beds contain shallow rhizoliths and indicate a relative sea-level drop that was punctuated by at least four, small-scale transgressions. The upper, continental section contains predominately eolian siltstone with siliciclastic Entisols and mottled Inceptisols. These paleosols contain large rhizohaloes and calcareous rhizocretions that are commonly associated with abundant Naktodemasis bowni. The uppermost ∼ 40 m of strata are laminated and crossbedded siltstone that contain little to no paleopedogenic development and few ichnofossils. These eolian beds were likely sourced from the erosion of underlying marine strata of the Hermosa Group as the Elephant Canyon Seaway regressed northward during the Pennsylvanian. Thin, coarse-grained fluvial strata can be observed throughout the HF and were likely sourced from the highlands of the Uncompahgre Uplift.

NEOICHNOLOGY OF SEMIARID ENVIRONMENTS: SOILS AND BURROWING ANIMALS OF THE SONORAN DESERT, ARIZONA, U.S.A.

Abstract: Whereas soils in semiarid environments have received considerable attention, specific biogenic structures produced by the plants and animals that inhabit them are less well understood. Soils in a field site in the Santa Catalina Critical Zone Observatory in the semiarid Sonoran Desert of southern Arizona were investigated to develop a model to improve the interpretation of analogous paleosols and associated soil ecosystems in the geologic record. A flat plateau of desert scrubland was divided into thirty-six 4 m2 plots for description and study. Field methods included mapping of soil surfaces, imaging with ground-penetrating radar, casting of open burrows, description of soil trenches, and soil coring. Laboratory methods included analysis of soil bulk geochemistry, clay mineralogy, and thin sections as well as detailed descriptions of burrow casts. Soils included 10–40 cm thick Entisols and Aridisols with blocky peds, pervasive, coarse (3–5 mm) to very fine (< 1 mm) roots, and were dominated by the burrows of ground squirrels and ants, as well as those of various lizards, snakes, scorpions, spiders, centipedes, termites, and insect larvae. Burrow morphologies included small (< 1 cm) to large (> 1 cm) diameter simple vertical shafts, isolated ovoid chambers, subhorizontal tunnels, subvertical to subhorizontal networks of branching tunnels, and complex branching galleries. Bioturbation was concentrated in the upper 20 cm of the soil profile, whereas roots often extended to the base of the profile. Results from this study advance our understanding of the traces produced by different soil organisms and their impact on soil development in modern settings and will be valuable for the interpretation of the paleosols from semiarid environments in the rock record.