Shell boring is one of the few quantifiable, well-preserved biotic interactions in the fossil record. While some workers have used boring intensity as a proxy for predation pressure in both Recent and fossil assemblages, others have warned that taphonomic and other effects can alter the boring intensity and lead to paleoecological misinterpretation. When the biocoenosis is known, however, taphonomic effects can be “undone” a posteriori. Because the valve ratio of any bivalved organism must be 1:1 in the biocoenosis, strengths of between-valve taphonomic biases can be calculated directly for any disarticulated assemblage of bivalved fossils. By back-calculating the biocoenotic boring intensities, improved estimates of boring stereotypy may be obtained. These “restored” boring intensities can provide more accurate paleoecological interpretations of boring habit while remaining numerically conservative.

Taphonomic analysis of a bored Ordovician brachiopod assemblage shows that (1) the assemblage had experienced negligible differential transport; and (2) convex (pedicle) valves have been preferentially crushed in place. Comparing the taphonomy of the assemblage to a set of laboratory taphonomic regimes reveals that valve-valve contact may be of great consequence in skeletal taphonomy. In particular, valve-valve contacts appear to promote (1) preferential destruction of convex valves; and (2) subequal destruction of bored vs. unbored valves. Taking into account these taphonomic effects, numerous hypotheses of boring habit—including mixed-motive boring—have been tested using a probabilistic model. The model herein presented indicates a likely contribution of 10–15% predatory boring in the assemblage. The usefulness of probabilistic models for providing simultaneous, realistic tests of multiple hypotheses is emphasized.

A low-diversity halysitid-heliolitid autobiostrome from the Late Wenlock Halla Formation at Blåhäll 1, Gotland, indicates a brief period of particular environmental conditions. The reef is 0.3–0.5 m thick, internally without bedding structures, and had a sheet-like distribution on a low-relief soft-bottom, in marginal platform, graptolitiferous strata (height-width ratio is 1:900 in outcrop). The dominating coral species building this mud-facies biostrome were the tabulates Stelliporella cf. parvistella and Halysites laticatenatus. The rugose coral fauna is dominated by fixosessile and rhizosessile forms with well developed holdfasts, for example Dokophyllum elegantulum. Coral growth forms generally indicate high background sedimentation rates during the growth of the biostrome.

Four successive stages of sea-floor development are discussed: (1) a pre-biostrome stage, (2) a pioneering community stage, (3) a climax-community stage, and (4) a post-biostrome stage. Stratigraphically, these stages show an increased carbonate-siliciclastic ratio, a decreased phosphorus content, somewhat lighter δ¹⁸O stable isotopes, and an increased rate of bioturbation. The climax-community stage coincides with a bloom(?) in paleocopid and metacopid ostracodes.

The biostrome differs from all other Wenlock-Ludlow reefs on Gotland in its geographic and stratigraphic isolation on the seaward slope of the carbonate platform. It was the first re-appearance of a reefal stucture following the oceanic Mulde Event and associated eustasy. On a regional scale, this appearance coincided with an inferred highstand systems tract and the onset of widespread reef growth in the basin indicating that, at least, basin-regional factors controlled reef growth.

Fossil plants are abundant in dolomite of the Clear Fork Group (Leonardian; late Early Permian) in the North Robertson Unit of the Robertson Clear Fork oil field of Gaines County, West Texas. The unit is a portion of the larger Robertson field. Thirty-seven separate collections were made from drill cores taken in three wells, spanning an interval 300 m thick from a depth below the surface of > 2000 m. The flora is depauperate, comprised of Comia sp. (most abundant), Taeniopteris sp., Delnortea abbottiae, callipterid-like foliage of uncertain affinity, calamite stems, and unidentified foliage of cycad-like character. Plants occur in discrete intervals that are a few cm to 3 m thick and have limited lateral continuity (less then 0.5 km). Plant-bearing dolomites contain interspersed fossil roots and burrows, weakly developed soil horizons, thin coaly accumulations of organic material, and pedogenic and collapse breccias. Fusain is common throughout. Between the plant-bearing layers are heavily bioturbated dolomites with anhydrite-filled burrows, interpreted as lagoonal to shallow subtidal in origin, up to 50 m thick. Contacts between marine units and plant-bearing beds are sharp.

The North Robertson Unit and the field is believed to be internal to the Central Basin Platform and bordered by a shallow seaway to the east. The Central Basin Platform probably represented a broad peninsula between the Midland Basin to the east and the Delaware Basin to the west. The site probably consisted of innumerable little islands separated by a network of waterways. Plants occur in “island complexes” consisting of deposits formed in ponded water, beach fronts, and lagoons. Vegetation must have been tolerant of salt or salt spray, seasonal drought, wind, and storms; all species were robust in construction, with either thick leaves or heavy cuticles. This flora, although clearly allied with other Early Permian floras from western North America, is sufficiently peculiar to indicate that habitat differentiation was well developed within the tropical lowlands during the Late Paleozoic.

The Lower Triassic (Smithian-Spathian) Union Wash Formation (east-central California), deposited along the western edge of Pangea, is generally barren of macrofossils with the exception of ammonoids. To better understand the paleoenvironmental conditions that existed in the region of Union Wash Formation deposition, data were gathered concerning the taphonomy, sedimentology, and distribution of these ammonoids. Results indicate Meekoceras bed deposition was due to a drop in background sedimentation rates, perhaps coupled with favorable environmental conditions. Disappearance of ammonoid shells in the stratigraphic interval above the Meekocerasbed appears to be the result of a shallow aragonite compensation depth (ACD); the return of ammonoids higher in the section is associated with the appearance of seafloor calcium carbonate cements that represent an increase in the degree of calcium carbonate supersaturation, related to the upwelling of anoxic, alkaline waters. The subsequent disappearance of seafloor cements suggests that seawater calcium carbonate chemistry returned to normal prior to deposition of the Parapopanocerasbed. The condensed nature of the Parapopanocerasbed, coupled with poor shell preservation, indicates deposition as a lag deposit. Bedding plane occurrences of ammonoids elsewhere in the sequence imply deposition as mass mortality events possibly related to anoxia (indicated by the depauperate and laminated nature of much of the unit) and/or hypercapnia (related to the growth of seafloor cements). The results of this study further attest to the unusual paleoceanographic conditions that were present off the western margin of Pangea during the Early Triassic recovery from the end-Permian mass extinction.

Diplocraterion parallelum with exclusively protrusive spreite are documented at particular horizons in fine-grained Lower Kimmeridgian (Upper Jurassic) deposits from the Prebetic Zone (Betic Cordillera, southern Spain). The occurrence of D. parallelum and the interpreted change from a Cruziana ichnofacies to a mixed Skolithos-Cruziana assemblage is related to increasing energy and more proximal and unstable substrates resulting from relative sea-level falls. These relative sea-level changes agree with a proposed Type-II sequence boundary inferred from sequence stratigraphic analysis. Bio-chronostratigraphic control shows the persistent occurrence of Diplocraterion close to the Platynota/Hypselocyclum Zone boundary (Lower Kimmeridgian); that is, these occurrences correlate between sections irrespective of slight deviations in the sedimentary package. Thus, Diplocraterion occurrence is proposed as a reference level for stratigraphy within epicontinental deposits of the northern margin of the westernmost Tethys. This work supports the usefulness of the trace fossil approach in basin analysis, either in sequence stratigraphic studies of deposits characterized by correlative conformities and/or stratigraphic correlation in basins wherein guide fossils are scarce.

An exhumed Pliocene estuarine sequence is preserved in exquisite detail in the Quinault Formation of coastal western Washington. The thick fill of the Quinault estuarine basin (∼700 m) represents a single transgressive-regressive system that was punctuated by subduction-related tectonic events, and may reflect erosion and sediment accumulation during accelerated uplift of the Olympic Mountains in the Pliocene. Sedimentation patterns in the ancient Quinault estuary were influenced strongly both by floods on the paleo-Quinault River, and by storm waves on the high-energy, open Pacific coast. Body fossils were derived from both marine and brackish faunal elements. Trace fossil suites indicate that the benthos flourished in the fluctuating physicochemical conditions of an estuary in dynamic equilibrium. An estuarine-specific trace fossil, a new ichnospecies of Psilonichnus that is attributed to burrows of the mud shrimp Upogebia pugettensis, is restricted to inlet-mouth, muddy sandstone facies. The marine-marginal marine transition is well-preserved in Quinault estuarine strata (exposed in the Point Grenville and Cape Elizabeth areas), as evidenced by: (1) distinctive sedimentologic signatures characteristic of lower shoreface, estuarine mouth, central basin, tidal creek/flat, and fluvial subenvironments; and, (2) systematic changes in trace fossil associations in the up-estuary direction, from Skolithos ichnofacies elements to a mixed Skolithos-Cruziana assemblage to Glossifungites associations with rhizome phytoburbation. Hence, Quinault strata record a classic tripartite division of an ancient estuarine system, allowing a fine-scale delineation of subenvironments in an active tectonic regime.