The late Paleozoic ice age (LPIA) began in the Mississippian period (Visean-Serpukhovian) and is associated with a global mass extinction. This study examines how the development of high-amplitude glacioeustasy at the start of the LPIA affected the taxonomic richness and ecologic diversity of tropical marine macro-invertebrate assemblages from the Illinois Basin (United States). Rarefaction and faunal turnover analyses reveal that regional taxonomic and guild richness persist nearly unchanged across the inferred onset of the LPIA and through multiple glacioeustatic cycles spanning a total duration of ∼3 to 5 myr. In addition, low levels of taxonomic turnover characterize the LPIA transition and subsequent glacioeustatic cycles; 76% to 92% of pre-LPIA taxa persist into the ice age where they account for 63% to 75% of LPIA taxa. Thus, the onset of high-amplitude glacioeustasy was not a main driver of regional biotic change or extinction in the Illinois Basin at the start of the LPIA. Potential mechanisms for the regional persistence of taxonomic diversity and faunal composition despite major glacioeustasy include habitat tracking and an immigration rescue effect, where localized extinction is balanced by immigration of taxa from nearby areas. Finally, evidence from this and other studies of late Paleozoic faunal turnover suggest that persistence, not change, is the normal biotic response to high-amplitude glacioeustasy during the LPIA.

A singular lower Aptian lithofacies from the western Maestrat Basin (Iberian Chain) highlights the reaction of carbonate platform paleocommunities to natural disturbances of regional to global significance. It is composed mainly of sand- to cobble-sized coral rubble rigidly bound by Lithocodium aggregatum and is coeval with the early Aptian Oceanic Anoxic Event (OAE1a) and the intensified greenhouse conditions connected with this event. Severe storms induced by high atmospheric concentrations of CO₂ had a recurrent catastrophic impact on coral populations, giving rise to sub-basin–wide coral rubble levels. Physical responses to elevated atmospheric CO₂ levels, such as increased nutrient fluxes, together with low sedimentation rates, and the presence of a hard substratum, favored the mass occurrence of Lithocodium crusts, large flattened Palorbitolina lenticularis, and bioeroders such as lithophagid bivalves and endolithic sponges. These encrusted coral rubble deposits are here interpreted as records of chemical and physical disturbances linked to the OAE1a. Due to significant extension and normal faulting recorded in the lower Aptian of the western Maestrat Basin, however, earthquake-induced natural stresses might also have played a part in the generation and reworking of these coral rubble deposits.

Upper Barruelian, “Saberian,” and Stephanian B (Kasimovian–lower Gzhelian) strata in northwestern Spain represent a strongly subsiding alluvial plain connected to the Paleotethys and adjacent to a mountainous hinterland. The rocks have been deformed into steeply dipping, often isoclinal synclines delimited by foreland-directed thrust faults; a steep basin margin with paleovalleys occurs on the hinterland side. One of these tectonic outliers is the La Magdalena Coalfield, of “Saberian” age, where the quantification of a substantial floral record (140 taxa) from 85 localities in 1200 m of strata allows us to observe changes in floral composition through time matched with broad changes in sedimentary facies corresponding to increased remoteness from a receding basin margin. Within the context of a humid environment, a predominantly fluvial facies changed upward and in time into more generalized semi-lacustrine and peat-forming facies. Although pteridosperms and marattialean tree ferns (pecopterids) are dominant throughout, a proportional increase in tree ferns is observed for the higher part of the succession where calamitaceans become less common and lycopsids more noticeable. These floral changes reflect wetter sedimentary conditions, conducive to the production of coals (high ash) of limited lateral extent.

Cerro de los Batallones fossil sites are distinguished by large and diverse accumulations of Miocene vertebrate fauna. Little taphonomic research has been conducted on these assemblages so far, however. Results of Rare Earth Element (REE) analyses constrain diverse aspects of the taphonomic history undergone by the bones and constitute a starting point for subsequent taphonomic studies. Cerro de los Batallones localities were formed as cavities and seem to be composed of two types of assemblages that differ in their stratigraphic position, internal stratigraphic architecture, taxonomic composition and several taphonomic features. Despite these differences, chemically analyzed bones from the Batallones-1 upper and lower level assemblages exhibit undistinguishable REE patterns both within and between them. This, together with other taphonomic features, indicates that bones are autochthonous and that the depositional context remained constant during the sedimentation of the cavity filling. In addition, REE analyses are a key tool in unveiling the provenance of those fossil bones that could be regarded as allochthonous considering their peculiar macroscopic modifications. Negative Ce anomalies exhibited by isolated fossil bones lead to the proposal that the ponds that existed in the lower level of Batallones-1 were oxic. This inference clarifies the mode of accumulation of individuals in this assemblage: the carcasses did not accumulate massively over a brief period of time but rather they concentrated and, therefore, decayed over a relatively prolonged time span.

Tubificids are important conveyor-belt feeders in freshwater settings because dense populations can rapidly rework bottom deposits through selective ingestion of silt and clay. The rate at which these organisms redistribute sedimentary particles is the focus of this research in which a new method is presented to address specific disadvantages of previous studies documenting tubificid bioadvection. The new approach incorporates an aquarium inoculated with sediment and worms in which the sediment surface is photographed through time as tubificids produce fecal mounds. Employing computer software, mounds are traced, and using a known pixel length, the program calculates the traced area, which is converted to volume of upturned sediment by assuming an idealized conical shape. This method resulted in a particle redistribution rate for a population of Limnodrilus and Tubifex at 0.042–0.139 cm/d/100,000 individuals/m² at 21 °C. During sediment reworking, segregation of silt and clay forms biogenic graded bedding defined by a poorly sorted bed with an overall decrease in mean, modal, and median grain sizes upward. This tubificid-formed graded bedding could be recognized in the rock record through careful analyses of grain-size distributions that distinguish biogenic reworking from physically graded beds. Ichnologically, this occurrence corresponds to the broad conditions defined by the Mermia Ichnofacies, but is yet unrecognized and may actually obliterate typical traces associated with this ichnofacies. Identification of ancient tubificid-formed graded beds has the potential to enhance interpretations of environmental conditions (sedimentation rate and current velocities), provide evidence for a previously unrecognized paleobiomass, and broaden the definition of the Mermia Ichnofacies.