Root Traces Research Articles

Identification of Macrofossils within Stone Tools: a possibility for tracing the source of artifacts?

This paper discusses the application of malacological identification of macrofossils in stone tools. A macroscopically distinct toolstone utilized by prehistoric peoples, reported widely in archaeological consulting literature across central and southern Alberta (Meyer et al. 2007; de Mille 2009; Bohach 2010; Porter 2014), features fossilized root traces and occasional large fossil shells. These fossils can be identified, and correlated with temporal and geologic formations indicative of the environments within which the taxa occurred. Artifacts with fossils morphologically coherent with Hydrobia, Lioplacodes, and Viviparus spp. are identified in stone artifacts analyzed in this paper. These taxa are consistent with depositional environments of Paleocene period Paskapoo Formation sedimentary rocks, particularly, as identified at the Blindman-Red Deer River confluence and Joffre roadcut paleontological localities (Hoffman and Stockey 2011). In this paper we explore how the identification of these fossils offer clues to the procurement areas which were sought out by prehistoric toolmakers. We do not suggest that all Red Deer Mudstone is from these localities, though the fossil molluscs presented so far do not refute this conclusion, but we do suggest that identifying large fossil shells can be a critical diagnostic tool for identifying the geologic origin of artifacts.

Paleosol and ichnofossil evidence for significant Neotropical habitat variation during the late middle Miocene (Serravallian)

We use paleopedology and ichnology to elucidate the habitat of the late middle Miocene fossil site of Quebrada Honda, southern Bolivia. The paleosols represent three pedotypes, Type 1 and Type 2 paleosols are interpreted as Inceptisols (Eutrudepts) and Entisols (Udifluvents), respectively, which formed on proximal and distal floodplains in a seasonal, sub-humid to humid wooded grassland-like vegetative community. Type 3 paleosols are interpreted as Inceptisols (Calciustepts) that formed in more densely vegetated wooded grassland-like vegetative communities on distal floodplains in a strongly seasonal sub-humid to semi-arid environment. The ichnofossil assemblage of Quebrada Honda includes Celliforma, Coprinisphaera, Taenidium, Fictovichnus, Planolites, Skolithos, Katarrhedrites, and root traces and represents heterogeneous communities dominated by soil arthropods and plants. The physical and geochemical properties of the paleosols, including low maturity, poor development of horizons, and the overall moderate estimates of mean annual precipitation, indicate changes in soil moisture due to seasonal precipitation and flooding and low but varying degrees of temporal stability. The diverse ichnofossil assemblage of Quebrada Honda reflects environments with greater primary productivity and temporal stability than those of nearby Cerdas, Bolivia, which are several million years older. Quebrada Honda's inferred paleoenvironments differ markedly from those of La Venta, Colombia, indicating that dissimilar habitats may partly or principally account for the vastly different faunas of these two well-sampled and contemporaneous fossil localities.

Risk factors of 12-month recurrence in patients with pancreatic ductal adenocarcinoma undergoing pancreatoduodenectomy

Studies of the palaeobiology of titanosaur eggs are significantly more common than studies of titanosaur-egg-bearing strata. Nevertheless, the latter provide significant insight into palaeoenvironmental conditions associated with the egg-laying behaviour. This study examines titanosaur-egg-bearing strata of the Upper Cretaceous Los Llanos Formation (La Rioja, Argentina) and relates them to the laying and preservation of titanosaur egg clutches. Los Llanos Formation is a predominantly sandstone succession throughout represented by palaeosol profiles. Five titanosaur egg clutches were recovered from the Bw horizon of an Inceptisol profile. This palaeosol type, named Tama pedotype, constitutes 69% of the entire succession, by thickness. Rare planar, and undulating lamination and cross stratification, quartz-grain surface microtextures and ventifacts are indicative of the interaction of fluvial-aeolian processes of sedimentation during accumulation of the parent material on the distal part of a coalescent alluvial fan system (bajada). Highly abundant root traces, reddish colour, clay coatings and calcium carbonate nodules testify that the Tama pedotype had abundant vegetation cover, and was developed in well-drained conditions under the influence of a semiarid climate regime. Palaeosol horizons with exaggerated thickness and diffuse boundaries indicate a cumulative pedotype, whereby the soil developed in response to continuous accretion via on-going sedimentary processes.Morphological features of eggshells suggest that titanosaurs dug holes in the topographic surface to lay eggs. Thus, palaeosols seem to have been putative areas for the laying of titanosaur eggs. Actually, it is uncommon for palaeosols to constitute sites for the preservation of eggs, since soils typically develop in response to long episodes of weathering. However, cumulative palaeosols can provide ideal conditions for egg burial and preservation. In cumulative soils, the residence time of an object within the weatherable thickness of a soil is reduced to < 103 years, thereby significantly increasing the long-term preservation potential of eggs.

Rhizometer root tracing techniques and digital image analysis for assessing and quantifying seedling root growth in substrates

Rhizometer root tracing techniques and digital image analysis for assessing and quantifying seedling root growth in substrates

Preservation of titanosaur egg clutches in Upper Cretaceous cumulative palaeosols (Los Llanos Formation, La Rioja, Argentina)

Studies of the palaeobiology of titanosaur eggs are significantly more common than studies of titanosaur-egg-bearing strata. Nevertheless, the latter provide significant insight into palaeoenvironmental conditions associated with the egg-laying behaviour. This study examines titanosaur-egg-bearing strata of the Upper Cretaceous Los Llanos Formation (La Rioja, Argentina) and relates them to the laying and preservation of titanosaur egg clutches. Los Llanos Formation is a predominantly sandstone succession throughout represented by palaeosol profiles. Five titanosaur egg clutches were recovered from the Bw horizon of an Inceptisol profile. This palaeosol type, named Tama pedotype, constitutes 69% of the entire succession, by thickness. Rare planar, and undulating lamination and cross stratification, quartz-grain surface microtextures and ventifacts are indicative of the interaction of fluvial-aeolian processes of sedimentation during accumulation of the parent material on the distal part of a coalescent alluvial fan system (bajada). Highly abundant root traces, reddish colour, clay coatings and calcium carbonate nodules testify that the Tama pedotype had abundant vegetation cover, and was developed in well-drained conditions under the influence of a semiarid climate regime. Palaeosol horizons with exaggerated thickness and diffuse boundaries indicate a cumulative pedotype, whereby the soil developed in response to continuous accretion via on-going sedimentary processes.Morphological features of eggshells suggest that titanosaurs dug holes in the topographic surface to lay eggs. Thus, palaeosols seem to have been putative areas for the laying of titanosaur eggs. Actually, it is uncommon for palaeosols to constitute sites for the preservation of eggs, since soils typically develop in response to long episodes of weathering. However, cumulative palaeosols can provide ideal conditions for egg burial and preservation. In cumulative soils, the residence time of an object within the weatherable thickness of a soil is reduced to <103years, thereby significantly increasing the long-term preservation potential of eggs.

Efficient Complex Root Tracing Algorithm for Propagation and Radiation Problems

An efficient complex root tracing algorithm for propagation and radiation problems is presented. The proposed approach is based on a discretization of Cauchy’s Argument Principle and its generalization to the $\mathbb {C}\times \mathbb {R}$ space. Moreover, an engagement of the tracing process with a global root finding algorithm recently presented in the literature is performed. In order to confirm a validity and efficiency of the proposed technique, a few different types of structures have been analyzed.

Need for re-apprehension of basin tectono-depositional set-up during initial stage of Himalayan orogeny from pedogenic evidences

The collision and suturing of Indian and Eurasian plates about 50Ma ago closed the Tethys Ocean, initiated Himalayan orogen and a foreland basin developed towards its south. The last phase of marine sedimentation in Indian sub-continent during Paleocene-Eocene is represented by Subathu Formation overlain by continental Dagshai sediments and nature of this transition, named as ‘Passage beds’ (sensu Bhatia and Mathur, 1965), is controversial. Further, it is poorly understood both in terms of depositional environment and age. Surprisingly, these beds show evidences of pedogenesis but no such palaeopedological studies have been reported so far. The degree and nature of pedogenesis is widely used in solving diverse geological problems in complex geological settings. Therefore, pedogenesis of these beds exposed in the Shimla hills of Subathu sub-basin has been worked out. Morphological and micromorphological studies divide them into older green/greenish-grey pedofacies (GP) and younger red/reddish-brown pedofacies (RP) units. Pedons are up to tens of centimeters thick. Structure largely comprises sub-angular to sub-rounded blocky peds. A suite of pedogenic features include burrows, root traces, infillings, mottling, cutans, segregations, and nodules which vary in dominance from GP to RP unit. Greenish-grey pedons are characterized by mottles, Fe-Mn oxide segregations whereas reddish-brown pedons by root traces commonly filled with carbonates, presence of carbonate segregations and cutans. Detailed field and laboratory studies at various local and regional exposures can reveal the nature and extent of pedogenesis which will be significant to enact depositional environment as well as stratigraphic position, of Passage beds co-relatable at different localities throughout length of the Himalaya from Pakistan to Nepal because of their distinctive lithology and stratigraphic position. Such studies bear global significance in demonstrating the use of palaeosols as a geologic archive in complex geological settings.

Uniqueness Deposit of Sediment on Floodplain Resulting From Lateral Accretion on Tropical Area

Kampar rivers has a length of 413 km with average depth of 7.7 m and width of 143 m. Sixty percent of this rivers are meandering fluvial system which transport and deposit a mixture of suspended and bed-load (mixed load) along low energy. River channel that moving sideways by erosion is undergoing lateral migration and the top of the point bar becomes the edge of the floodplain and the fining-upward succession of the point bar will be capped by overbank deposits of Kampar River. Along the Kampar Rivers, there are more than 60% of floodplain sediments and almost all of the floodplain formed by bend migration on the suspended-load channels of Kampar watershed. This formation consist of succession of fine to medium sand and silt/mud, with root traces, that form as drapes on the prograding bank. These beds dip mostly channel wards and quickly wedge out as they grade up and onto the floodplain. The depositional model is presented showing how lateral accretion can make a significant contribution to the preservation of fine-grained within channel deposits in contemporary floodplains. The examples presented here demonstrate that analogues to ancient point-bar deposits containing alternating sandstone and shale sequences are common in the low-energy fluvial environments of Riau rivers especially Kampar rivers.

Paleosols of the upper Paleozoic Sangre de Cristo Formation, north-central New Mexico: Record of early Permian palaeoclimate in tropical Pangaea

The lower Permian (Wolfcampian) Sangre de Cristo Formation of northern New Mexico consists of silty mudstones and laterally discontinuous sandstones deposited on an aggrading alluvial plain. Locally, mudstones display a variety of pedogenic features. Common mudstone fabrics vary from platy to prismatic; some beds display prominent pedogenic slickensides. Drab-colored root traces are common throughout the section, as are calcareous nodules, which vary from small bodies with diffuse boundaries to vertically stacked, discrete, cm-scale nodules (rhizocretions), and less commonly form coalescing horizons. Vertisols occur only in the lower portion of the ca. 90-m measured section. Most of the mudstone beds contain calcretes that are immature (calcic Protosols to calcic Argillisols), but the lower to middle portion of the section also contains mature calcrete horizons (argillic Calcisols and Calcisols).Intercalated micritic limestone beds with sharp contacts containing root traces, are of laterally variable thickness and grade to nodular calcretes. These are interpreted as floodplain pond carbonates that have undergone pedogenic alteration (palustrine limestones), indicating long periods of exposure under strongly seasonal climatic conditions. The isotopic composition of the pedogenic carbonate displays a substantial range of values, but most of the range of variation in isotopic composition is accounted for by isotopically heavier carbonate (both carbon and oxygen) precipitated in shallow ponds subject to intense pedogenic reworking (palustrine carbonate).During the early Permian, northern New Mexico was situated in a near equatorial position (ca. 4° N). The overall character of the paleosols suggests a persistent warm, semi-humid, seasonal climate throughout most of the interval of deposition during the Wolfcampian, but with episodically increased aridity during formation of the more mature calcretes. No long-term trend of climate change is evident in the stratigraphic section examined for this study.

Exploring the role of otariids in the subsistence of hunter gatherers from Pampean archaeological sites at the Late Holocene (Argentina)

New taxonomical, anatomical, taphonomic and chronological information about archaeological remains of otariids from Puente de Fierro site (Pampean region, Argentina) is presented. Two species, Arctocephalus australis and Otaria flavescens, were identified. Fragmentation and traces of roots were the predominant taphonomic effects; also slight weathering stages were recognized and scarce gnawing marks of carnivora were identified. Frequencies of skeletal parts suggest that only certain anatomical pieces, especially limbs, entered the site or were preserved. We propose that hunter-gatherers occasionally obtained otariids from the Atlantic coast (transported them 7km away to the residential camp) or some individuals that enter freshwaters in the fluvial environment near the site. Puente de Fierro record stands out from regional Late Holocene inland sites, because otariids NISP and MNI are notably higher than in similar and synchronic assemblages.

Facies analysis and depositional model of the Serravallian-age Neurath Sand, Lower Rhine Basin (W Germany)

AbstractThe up to 60 m thick Neurath Sand (Serravallian, late middle Miocene) is one of several marine sands in the Lower Rhine Basin which were deposited as a result of North Sea transgressive activity in Cenozoic times. The shallow-marine Neurath Sand is well exposed in the Garzweiler open-cast mine, which is located in the centre of the Lower Rhine Basin. Detailed examination of three sediment profiles extending from the underlying Frimmersdorf Seam via the Neurath Sand and through to the overlying Garzweiler Seam, integrating both sedimentological and palaeontological data, has enabled the depositional setting of the area to be reconstructed.Six subenvironments are recognised in the Neurath Sand, commencing with the upper shoreface (1) sediments characterised by glauconite-rich sands and an extensive biota (Ophiomorphaichnosp.). These are associated with the silt-rich sands of a transitional subenvironment (2), containingSkolithos linearis, Planolitesichnosp. andTeichichnusichnosp. These silt-rich sands grade up to the upper shoreface subenvironment (1), which is indicative of an initial regressive trend. The overlying intertidal deposits can be subdivided into a lower breaker zone (3), characterised by ridge-and-runnel systems, and the swash zone (4) where the surge and backwash of waves resulted in the deposition of high-energy laminites. The intertidal deposits were capped by aeolian backshore sediments (5). Extensive root traces present in this latter subenvironment reflect the development of the overlying peatland (i.e. Garzweiler Seam). Within the Garzweiler Seam, restricted sand lenses indicate a lagoonal or estuarine depositional environment (6). Regional correlation with adjacent wells establishes that shallow-marine conditions were widespread across the Lower Rhine Basin in middle Serravallian times. The shoreline profile, characterised by both tidal and wave activity and influenced by fluvial input from the adjacent Rhenish Massif, is indicative of the complexity of the coastal depositional setting within the Lower Rhine Basin.

Trace fossils from the Baltoscandian erratic boulders in SW Poland

Many well preserved trace fossils were found in erratic boulders and the fossils preserved in them, occurring in the Pleistocene glacial deposits of the Fore-Sudetic Block (Mokrzeszow Quarry, Świebodzice outcrop). They include burrows ( Arachnostega gastrochaenae , Balanoglossites isp., ? Balanoglossites isp., ? Chondrites isp., Diplocraterion isp., Phycodes isp., Planolites isp., ? Rosselia isp., Skolithos linearis , Thalassinoides isp., root traces) and borings ? Gastrochaenolites isp., Maeandropolydora isp., Oichnus isp., Osprioneides kampto , ? Palaeosabella isp., Talpina isp., Teredolites isp., Trypanites weisei , Trypanites isp., ? Trypanites isp., and an unidentified polychaete boring in corals. The boulders, Cambrian to Neogene (Miocene) in age, mainly came from Scandinavia and the Baltic region. The majority of the trace fossils come from the Ordovician Orthoceratite Limestone, which is exposed mainly in southern and central Sweden, western Russia and Estonia, and also in Norway (Oslo Region). The most interesting discovery in these deposits is the occurrence of Arachnostega gastrochaenae in the Ordovician trilobites (? Megistaspis sp. and Asaphus sp.), cephalopods and hyolithids. This is the first report of Arachnostega on a trilobite (? Megistaspis ) from Sweden. So far, this ichnotaxon was described on trilobites from Baltoscandia only from the St. Petersburg region (Russia). Arachnostega on a trilobite ( Asaphus ), a cephalopod and hyolithids is from Russia or Estonia. Another interesting ichnotaxon is Balanoglossites , which also was encountered in the erratic boulders from the Ordovician Orthoceratite Limestone of Sweden. So far, this ichnotaxon was known only from Russia (St. Petersburg region). Some rare borings (e.g., Osprioneides kampto , ? Palaeosabella isp.) also were found in glacial erratics of Silurian stromatoporoids, excellent outcrops of which are located in Gotland (Sweden) and Saaremaa (Estonia). In addition, stromatoporoid/coral, coral/coral and some new fossil associations are reported. The material studied probably was transported from the N, the NE, and less commonly from the NW.

Central projections and connections of lumbar primary afferent fibers in adult rats: effectively revealed using Texas red-dextran amine tracing

Signals from lumbar primary afferent fibers are important for modulating locomotion of the hind-limbs. However, silver impregnation techniques, autoradiography, wheat germ agglutinin-horseradish peroxidase and cholera toxin B subunit-horseradish peroxidase cannot image the central projections and connections of the dorsal root in detail. Thus, we injected 3-kDa Texas red-dextran amine into the proximal trunks of L4 dorsal roots in adult rats. Confocal microscopy results revealed that numerous labeled arborizations and varicosities extended to the dorsal horn from T12-S4, to Clarke's column from T10-L2, and to the ventral horn from L1-5. The labeled varicosities at the L4 cord level were very dense, particularly in laminae I-III, and the density decreased gradually in more rostral and caudal segments. In addition, they were predominately distributed in laminae I-IV, moderately in laminae V-VII and sparsely in laminae VIII-X. Furthermore, direct contacts of lumbar afferent fibers with propriospinal neurons were widespread in gray matter. In conclusion, the projection and connection patterns of L4 afferents were illustrated in detail by Texas red-dextran amine-dorsal root tracing.

Accuracy of tree root biomass sampling methodologies for carbon mitigation projects

Tree root biomass contributes significantly to forest carbon pools but is difficult and costly to estimate. Accurate estimates of carbon fluxes from tree roots are required for specific mitigation projects, national accounts and global climate models. However, methodologies for the estimation of tree root biomass are varied and their effectiveness in terms of the precision of biomass and carbon estimates is difficult to evaluate. In this study tree root systems of 2 and 7year old Eucalyptus globulus (Labill) trees were sampled volumetrically to a depth of 6m using soil coring and excavation. These root mass data were used for Monte Carlo simulation of four different but typically used sampling strategies.The uncertainty of estimates increased with tree age as a result of increased heterogeneity of root mass due to the presence of large diameter roots. Coring had the largest sampling uncertainty when applied to estimate coarse root biomass which did not include the root bole. Bulk excavation was the simplest and potentially the most time efficient method to attain a sampling uncertainty of 10%. Excavation to a root diameter limit enables better association of root biomass to individual sample trees however, more effort is required if roots are directly related to the sample tree by tracing of roots to a small diameter. Although root ball methods required the least amount of excavation and soil coring to attain a sampling uncertainty of 10%, this method requires sieving of excavated soil through a small mesh size and is more time consuming and difficult to apply in heavier textured soils. The efficiency of coring and precision of root mass estimates can be improved if coring is concentrated in closer proximity of the sample tree or within the boundary of the larger diameter proximal roots.

AN ABANDONED-CHANNEL FILL WITH EXQUISITELY PRESERVED PLANTS IN REDBEDS OF THE CLEAR FORK FORMATION, TEXAS, USA: AN EARLY PERMIAN WATER-DEPENDENT HABITAT ON THE ARID PLAINS OF PANGEA

Abstract A well preserved plant assemblage at the Colwell Creek Pond locality of Leonardian (Kungurian) age provides an opportunity to evaluate taphonomic conditions in a dryland alluvial setting. A narrow channel body incised to 5 m depth through red paleo-Vertisols contains 2 m of varicolored laminated mudstone with graded layers and plant material. X-ray diffraction analysis of individual laminae indicates the presence of chlorite, illite, kaolinite, and mixed-layer clay, with hematite in red and gray layers and goethite in yellow-brown laminae. No carbonate was identified, and the total organic carbon content is minimal. The fine sediment accumulated in a shallow abandoned channel from suspension and gentle underflows, probably linked to seasonal inflow, and analysis of lamina thickness suggests that standing water may have persisted for up to a few millennia. The preservation of lamination is attributed to a lack of bioturbation, possibly linked to a paucity of subsurface oxygen, low productivity, elevated salinity, rapid deposition, or a combination of these factors; minimal bioturbation may also reflect the limited use of freshwater ecospace during the Early Permian. Clay-rich paleo-Vertisols complete the fill, with drab root traces that indicate growth of vegetation in a strongly seasonal setting. Abundant plant material in the laminated beds includes branches of walchian conifers, the possible cycadophyte Taeniopteris spp., and the comioid, possible peltasperm, Auritifolia waggoneri. They were derived from an adjacent riparian zone and preserved as 3D goethite petrifactions. Much of the foliage shows evidence of arthropod herbivory. Although a humid climatic episode cannot be ruled out, the exceptional abundance and preservation of the plants probably reflects the persistence of an oxbow lake on a relatively arid alluvial plain, where riparian plants experienced periodic moisture stress but had access to groundwater nearly year round. Rapid burial in standing water, the lack of bioturbation in the laminated sediments, and early biomineralization probably explain the exceptional preservation of the plant remains.

Bee cell trace fossils associations on paleosols from the Santa Cruz Formation: Palaeoenvironmental and palaeobiological implications

Numerous isolated fossil bee cells and other trace fossils are documented from the Santa Cruz Formation (Santa Cruz, Argentina). The trace fossils are described from paleosols of 7 coastal localities. The paleosols are composed of massive to laminated claystone to siltstone or massive to diffuse laminated very fine tuff and reworked tuff. They are poorly developed but include rich trace fossils and root traces assemblages. The isolated bee cells (n=47) are barrel to oval shaped, with one end rounded to flattened and the other flattened. They lack discrete walls and antechambers but have a smooth lining. They are ascribed to Celliforma rosellii (n=28) and to a new ichnospecie, Celliforma argentina (n=19). The new ichnospecies differs from C. rosellii on the shape of the inferior end of the chamber, been the first rounded to flattened and the C. rosellii rounded to pointed, resulting in a final barrel shape in C. argentina and an oval shape in C. rosellii. C. rosellii has an average length and width of 17mm and 9.8mm. C. argentina average length and width are 9.2 and 5.1mm. In some specimens of C. rosellii below the basal mark in the cell, the infill has a strong organic component that has been identified under SEM. This could indicate the exceptional preservation of the fluid deposited by the adult bee for the nutrition of the larva. The trace fossils assemblage shows moderate diversity and abundance. The ichnoassemblage recorded consist in Celliforma rosellii, Celliforma argentina, Palaeophycus tubularis, Planolites beverleyensis, Feoichnus challa, Fictovichnus gobiensis, Taenidium barretti and a variety of root traces. These trace fossils are considered to be part of a Celliforma ichnofacies but with a scarce presence of calcareous components. Considering pedogenic features, compositional aspects and ichnoasemblage a relatively warm, semiarid–subhumid and seasonal climate where herbaceous communities dominated can be established for the middle to upper interval of the Santa Cruz Formation.

The terrestrial landscapes of tetrapod evolution in earliest Carboniferous seasonal wetlands of SE Scotland

The Lower Mississippian (Tournaisian) Ballagan Formation in SE Scotland yields tetrapod fossils that provide fresh insights into the critical period when these animals first moved onto land. The key to understanding the palaeoenvironments where they lived is a detailed analysis of the sedimentary architecture of this formation, one of the thickest and most completely documented examples of a coastal floodplain and marginal marine succession from this important transitional time anywhere in the world. Palaeosols are abundant, providing a unique insight into the early Carboniferous habitats and climate.More than 200 separate palaeosols are described from three sections through the formation. The palaeosols range in thickness from 0.02 to 1.85m and are diverse: most are Entisols and Inceptisols (63%), indicating relatively brief periods of soil development. Gleyed Inseptisols and Vertisols are less common (37%). Vertisols are the thickest palaeosols (up to 185cm) in the Ballagan Formation and have common vertic cracks. Roots are abundant through all the palaeosols, from shallow mats and thin hair-like traces to sporadic thicker root traces typical of arborescent lycopods.Geochemical, isotope and clay mineralogical analyses of the palaeosols indicate a range in soil alkalinity and amount of water logging. Estimates of mean annual rainfall from palaeosol compositions are 1000–1500mm per year. The high mean annual rainfall and variable soil alkalinities contrast markedly with dry periods that developed deep penetrating cracks and evaporite deposits. It is concluded that during the early Carboniferous, this region experienced a sharply contrasting seasonal climate and that the floodplain hosted a mosaic of closely juxtaposed but distinct habitats in which the tetrapods lived. The diversification of coastal floodplain environments identified here may link to the evolution and movement of tetrapods into the terrestrial realm.

The significance of trace fossils in the McMurray Formation, Alberta, Canada

Abstract This paper considers the paleoecological and paleodepositional significance of bioturbated channel-associated sands of the McMurray Formation, Alberta, Canada. The facies associations described in this paper include: 1) thalweg-associated cross-stratified sand; 2) bar-related Inclined Heterolithic Stratification; and 3) bar-top / tidal-flat deposits. Thalweg-associated cross-stratified sands contain mud-lined Skolithos and Cylindrichnus, with rare Planolites, Palaeophycus, Siphonichnus, Conichnus, and bivalve-generated equilibrichnia and fugichnia. Bar-related inclined heterolithic stratification contains Planolites-Teichichnus-Cylindrichnus associations, Cylindrichnus-Skolithos-Planolites assemblages, and monospecific Gyrolithes-dominated facies, any of which may contain subordinate Siphonichnus, Palaeophycus, Psilonichnus, and Arenicolites. Bar-top/tidal-flat deposits are characterized by gently dipping to horizontal, bioturbated, heterolithic media containing Planolites and Cylindrichnus, with rare Skolithos, Thalassinoides and Arenicolites. The trace-fossil assemblages in the three facies associations show numerous features characteristic of brackish-water environments: 1) suites are of low diversities; 2) suites contain marine-derived ichnogenera; 3) ichnogenera are characterized by size diminution; 4) ethological associations correspond to the activities of trophic generalists; 5) intervals locally indicate high infaunal biomasses; and 6) intervals display evidence of r-selected (opportunistic) colonization strategies. Such trace-fossil assemblages are only consistent with examples of brackish-water ichnocoenoses in modern settings and in high-certainty brackish-water deposits documented from around the world. These ichnological observations are supported by the abundance of tidally generated sedimentary structures (sigmoidal bedding, draped foresets, reactivation surfaces and bidirectionally oriented cross-stratification) as well as marine dinocysts recovered from these facies. The paleontological and physical sedimentological characteristics require the presence of tidal currents and brackish-water to explain middle McMurray Formation deposition. Bioturbation ascribable to fresh-water conditions is present, albeit rarely, in the McMurray Formation. This includes occurrences of irregularly shaped shafts and tunnels displaying variable diameters, as well as Taenidium and Naktodemasis observed in bar-top units. These trace fossils are normally found in association with root traces and pedogenically altered sediments situated near the top of the lower McMurray. These assemblages confirm that during McMurray time, freshwater and brackish-water ichnocoenoses were present and yielded discrete and readily discernible trace fossil suites. Brackish-water thalweg, bar, and bartop units, which are consistently devoid of pedogenic alteration and root traces, are explained by: 1) the presence of brackish-water in the depositional setting; and 2) the presence of tides to facilitate the landward transport of marine-derived larvae and the establishment of a bar-top tidal zone. As such, contrary to some recent interpretations, assertions that the McMurray Formation channels can be broadly interpreted as fluvial channels are not tenable.

Rhabdoxylon taiyuanense n. sp.: A new botryopterid fern from the Lower Permian of Shanxi Province, North China

This paper described a new early leptosporangiate fern occurring in the Lower Permian coal balls from Shanxi Province, North China. The fossil materials include stems, attached and detached petioles and roots, belonging to a same kind of plant. Stems are relatively small in diameter and branch dichotomously. They possess a haplostele with metaxylem tracheids decreasing outward in diameter and showing uniseriate scalariform thickenings. There are no distinguished protoxylem groups in the xylem cylinder. Cortex is parenchymatous and can be divided into three zones according to cell size. Petiolar traces bear different shapes in cross section and show a spiral diverging sequence. Petioles are circular in cross section and cortical cells are much smaller than those of stems. Petiolar traces and petioles possess a single protoxylem group at the adaxial side of the xylem strand. Root traces originate from the cauline stele and go through the cortex in a way perpendicular or oblique to the cauline stele. These characters show great similarities to the genus Rhabdoxylon but are not consistent with its any known species, so it is necessary to create a new species Rhabdoxylon taiyuanense n. sp. for the present plant. The new species probably possesses an upright habit. This is the first report of the existence of the genus Rhabdoxylon in the Cathaysian Flora. The discovery of a new type of the Palaeozoic leptosporangiate fern in China has led to reevaluation of the systematic relationships among species of the Botryopteridaceae.

Miocene global change recorded in Columbia River basalt–hosted paleosols

Paleosols preserved between flows of the Columbia River Basalt Province record hiatuses in basalt emplacement and provide detailed information about paleoclimatic and pedogenic conditions during pedogenesis. The relatively long duration of pedogenesis (104 to >106 yr) for these paleosols makes them unlikely to have been influenced by short-duration climate fluctuations and allows them to accurately reflect long-term climate trends related to global climate change. Ten paleosols hosted by the Grande Ronde and Wanapum Formations of the Columbia River Basalts were identified on the basis of pedogenic features such as horizon development, root traces, and saprolitization, and they were studied as paleoclimatic indicators. Relationships between the ages of the paleosols and their clay-mineral compositions suggest that pedogenic processes changed in the eastern Columbia River Basalt Province at ca. 15.8 Ma. Analyses of mass-balance trends and chemical alteration in a ca. 16.0 Ma paleosol indicate that it formed under warm, humid climate conditions. We suggest that the absence of similar warm, humid paleosols and the presence of 2:1 clay-rich paleosols that formed after ca. 15.8 Ma represent a cooling and drying climate change related to the termination of the middle Miocene climate optimum, a development not previously captured in paleosol studies. In addition, the well-constrained dates of the basalts provide better resolution on the timing of this termination. When combined with other middle Miocene paleoclimate estimates from the Columbia River Basalt Province, our results suggest a geographic control on mean annual precipitation in the middle Miocene Columbia River Basalt Province leading to an increasing-to-the-east precipitation gradient.