A complex variety of marginal-marine microtidal environments from Kouchibouguac Bay, New Brunswick, Canada, present an opportunity to ichnologically and sedimentologically characterize microtidal settings in a high-latitude, temperate subarctic climate. Variations in bioturbate fabrics and distribution of infauna, analysis of the distributions of sediments and physical sedimentary structures, and the distribution of total organic carbon (TOC) can be associated with characteristic depositional processes. From these data typical sedimentary facies associations are produced. In outer estuary tidal inlets and areas of the flood-tidal deltas, strong currents and wave action eradicate the ichnological signature, resulting in variably laminated and bedded sand. In the central estuary, infauna activity coupled with generally low hydraulic energy levels lead to an absence of primary sedimentary structures. The inner estuary near bay-head deltas experiences riverine currents and freshwater influence. As a consequence, primary sedimentary structures are preserved. Mapping of infauna, sediment texture, TOC, and salinity reveals strong links between animal distribution and these three physicochemical parameters. Consequently, the distribution and type of bioturbation observed is at least passively related to grain size, TOC, and salinity. In outer estuaries and lower-central estuaries, salinity is near marine levels and fluctuates minimally. The distribution of infauna in these areas corresponds directly to sediment texture and TOC. Further up the estuaries, lower and fluctuating salinities—in addition to sediment texture and TOC content—control the distribution and diversity of infauna. Mapping of diversity and infaunal size up-estuary reveals two significant trends attributable to salinity stresses: (1) vermiform diminution, and (2) a significant decrease in infaunal diversity.

The application of oxygen isotope ratios (δ¹⁸O) from freshwater bivalves as a proxy for river discharge conditions in the Rhine and Meuse rivers is investigated. We compared a dataset of water temperature and water δ¹⁸O values with a selection of recent shell δ¹⁸O records for two species of the genus Unio in order to establish: (1) whether differences between the rivers in water δ¹⁸O values, reflecting river discharge conditions, are recorded in unionid shells; and (2) to what extent ecological parameters influence the accuracy of bivalve shell δ¹⁸O values as proxies of seasonal, water oxygen isotope conditions in these rivers. The results show that shells from the two rivers differ significantly in δ¹⁸O values, reflecting different source waters for these two rivers. The seasonal shell δ¹⁸O records show truncated sinusoidal patterns with narrow peaks and wide troughs, caused by temperature fractionation and winter growth cessation. Interannual growth rate reconstructions show an ontogenetic growth rate decrease. Growth lines in the shell often, but not always, coincide with winter growth cessations in the δ¹⁸O record, suggesting that growth cessations in the shell δ¹⁸O records are a better age estimator than counting internal growth lines. Seasonal predicted and measured δ¹⁸O values correspond well, supporting the hypothesis that these unionids precipitate their shells in oxygen isotopic equilibrium. This means that (sub-) fossil unionids can be used to reconstruct spring-summer river discharge conditions, such as Meuse low-discharge events caused by droughts and Rhine meltwater-influx events caused by melting of snow in the Alps.

Silicification of higher plants associated with active, alkali-chloride hot springs in Yellowstone National Park, Wyoming, USA, occurs dominantly in areas of geothermally influenced wetlands. Plants grow in an environment with many of the characteristics of an oligosaline marsh and are subjected to brackish salinity and high pH, temperature, silica, and heavy metal concentrations. As such, the plants undergoing silicification at Yellowstone are predominantly those more typically found colonizing widespread evaporation-driven inland waters and coastal salt marshes (e.g., Eleocharis rostellata, Triglochin maritimum) and are in some ways preadapted to hot-spring settings. This paper documents hydrochemistry and physical parameters in a typical geothermally influenced wetland at Big Blue Hot Spring, Elk Park in Yellowstone and records the taphonomic processes involved in silicification of the most common wetland plant Eleocharis rostellata. Silicification of plants in situ results in the three-dimensional preservation of tissues and cells characteristic of plants preserved around the Lower Devonian Rhynie chert hot-spring system. Sinter deposition at active and fossil hot-spring areas is typically associated with alkali-chloride springs above low-sulfidation epithermal systems. As mineralogical and geological evidence indicates that such a system was responsible for preservation of the Rhynie plants, it is hypothesized that they too, at least periodically, withstood comparable physiological stresses to the modern analogs.

Biostratinomic and bone-diagenesis parameters are used to evaluate the effects of abiotic and biotic processes on the final composition of two late Eocene vertebrate assemblages preserved in a swampy circum-lake environment from the Zambrana site (Basque-Cantabrian Region, northern Iberian Peninsula). No significant transport or bone sorting by fluvial action is observed, and complete and fragmentary bones in the assemblages (Z4 and Z6 beds) show the same biostratinomic features. The attritional bone accumulation in both excavated beds was caused mostly by biotic factors related to routine ecological deaths of population members, probably with some input from predators on the most vulnerable ungulate individuals (autochthonous), although a weak input of small remains by superficial water currents from nearby areas (parautochthonous) cannot be rejected. The vegetation and wet conditions of the swampy environment, together with possible predator and scavenger activity, could have caused the disarticulation and dispersion of some vertebrate remains, mainly those of ungulates. The bones were buried relatively quickly in the phreatic zone under reducing conditions and suffered considerable crushing and fragmentation because of lithostratigraphic compaction. Mineralogic similarities between sedimentary fillings in the fossils and the host sediment, as well as the homogeneous rare earth element (REE) trends of the fossils, are indicative of a uniform and unique diagenetic history and the absence of reworked elements. The fossil bone mineral is well-crystallized francolite (carbonate fluorapatite). The REE enrichment of bones and their calcite and pyrite crusts and fillings were formed during early diagenetic phases. The black coloration of the bones may be explained by their high hydrocarbon (n-alkane components) contents.

Landmark- and semilandmark-based geometric morphometrics were used to explore morphological variation in the occlusal surface and linea sinuosa (enamel-dentine junction) of first lower molars (m1s) of Ogmodontomys sawrockensis and O. poaphagus from the Meade Basin in southwestern Kansas. Morphological differences between the two species were determined in an effort to explore interspecific variation and to test the power of landmark geometry of dental variation for species discrimination. Significant differences were found between O. sawrockensis and O. poaphagus in both occlusal surface and the linea sinuosa patterns. Multivariate tests demonstrate that the most significant morphological changes occurred at the presumed O. sawrockensis-O. poaphagus speciation event. An intraspecific multivariate analysis of O. poaphagus m1s, however, also identified directional evolutionary tendencies in shape of both the occlusal surface and linea sinuosa.

The drainage system of the Granada Basin in southern Spain has evolved from endorheic to exorheic since the basin emerged and became continental in the latest Tortonian (late Miocene). The age of implementation for the recent exorheic, east-west drainage can now be identified by small mammal dating. This drainage configuration began in the latest Pliocene–earliest Pleistocene due to the capture of the Genil River by a Cacín River tributary. It represented an important change in the behavior of the basin and therefore in the geomorphology, as depositional forms and processes were replaced by erosive ones. While the basin was endorheic, sedimentation was active throughout the basin. Afterward the change to exorheic and up to the present, erosion dominates and sedimentation occurs only in some small, fault-controlled depositional depocenters.