An analysis is presented of the diversity and faunal turnover of Jurassic ammonites related to transgressive/regressive events. The data set contained 400 genera and 1548 species belonging to 67 ammonite zones covering the entire Jurassic System. These data were used in the construction of faunal turnover curves and ammonite diversities, that correlate with sea-level fluctuation curves. Twenty-four events of ammonite faunal turnover are analyzed throughout the Jurassic. The most important took place at the Sinemurian-Carixian boundary, latest Carixian-Middle Domerian, Domerian-Toarcian boundary, latest Middle Toarcian-Late Toarcian, Toarcian-Aalenian boundary, latest Aalenian-earliest Bajocian, latest Early Bajocian-earliest Late Bajocian, Early Bathonian-Middle Bathonian boundary, latest Middle Bathonian-earliest Late Bathonian, latest Bathonian-Early Callovian, earliest Early Oxfordian-Middle Oxfordian, earliest Late Oxfordian-latest Oxfordian, latest Early Kimmeridgian, Late Kimmeridgian, middle Early Tithonian and Early Tithonian-Late Tithonian boundary. More than 75 percent of these turnovers correlate with regressive-transgressive cycles in the Exxon, and/or Hallam′s sea-level curves. In most cases, the extinction events coincide with regressive intervals, whereas origination and radiation events are related to transgressive cycles. The turnovers frequently coincide with major or minor discontinuities in the Subbetic basin (Betic Cordillera).

The late Pliocene to early Pleistocene siliciclastic succession of western Emilia (northern Italy) forms part of the infill of the Po Plain-Adriatic foredeep, a collisional basin with active thrusting during deposition, and is characterized by 5-to-20-m-thick fining-upward sedimentary cycles. Late Pliocene cycles were deposited in an inner-to-middle shelf setting at the end of a long-term uplift-denudation cycle controlled by tectonics. Cycles are characterized by shell beds of biogenic origin, particularly abundant in the middle of each cycle. The stacking pattern of paleocommunities, with particular reference to their paleodepths, reflects that each cycle is the product of sea-level variation. In particular, early transgressive deposits are marked by a Nuculana community, indicating a shelly-sand bottom of the inner shelf; late transgressive deposits and the condensed section are marked by a shelly bottom Timoclea community developed at times of lowered clastic input; highstand deposits are characterized by a muddy soft bottom Pinna community.

The situation changed near the boundary of the early Pleistocene, when a new uplift-denudation cycle started, renewing sediment availability and increasing the slope of the nearby mountain front. Local climatic conditions periodically triggered the sudden delivery on the shallow shelf of large amounts of sediment through hyperpycnal flows and related turbidity currents generated by catastrophic river floods. Sandy shelfal lobes form the lower reaches of the delta front. These are characterized by densely packed shell beds and the occurrence of echinoderm obrution deposits. Recurring sedimentological assemblages from sandstones, characterized by the sandy bottom Spisula and Ditrupa communities, and in situ faunas from intervening mudstones, characterized by the muddy-bottom, hypoxic Arctica (and Corbula?) community, suggest that the lower part of a cycle formed during deglaciation following glacial maxima, at times of high input of freshwater and river-borne nutrients and high summer pelagic productivity. Mudstones from the upper part of the cycle, with dispersed remains of the muddy-bottom Venus community, indicate return to full interglacial conditions and to humid, low seasonality climates. Thus, early Pleistocene cycles could be correlative to sapropel-non sapropel cycles typical of the eastern Mediterranean deep water successions. Moreover, the western Emilia fossil and sedimentary records suggest that cyclic deposition was controlled by factors other than eustasy, providing a case study for future sequence stratigraphic modeling in active tectonic settings.

Articulated and disarticulated shells of Anadara ovalis, Anomia simplex, Argopecten irradians, Astarte castanea, Crassostrea virginica, Divalinga quadrisulcata, Donax variabilis, Ensis directus, Geukensia demissa, Mercenaria mercenaria, Mya arenaria, Mytilus edulis, Petricola pholadiformis, Spisula solidissima, and Tagelus plebeius collected from New Jersey intertidal life and death assemblages were measured, and the frequency, type (scalloped, divoted, cleft, embayed), location (ventral, anterior, posterior), and shell size at inception of repair determined. Repair frequency ranges from zero (D. quadrisulcata) to 0.30 (M. arenaria). Size refuge from sublethal breakage was attained by S. solidissima and C. virginica. Posterior repairs necessitated by siphon-nipping characterize M. mercenaria and E. directus. Ventral repairs associate with species subjected to valve-wedging (S. solidissima, M. mercenaria) or with ventral egress of the foot (A. ovalis). Ventral repairs among deep infaunal clams (M. arenaria, E. directus, T. plebeius) may have been induced by sediment-loading stress during burrowing. Anterior repairs are characteristic of deep infaunal species with foot exposure (M. arenaria, T. plebeius). Repair frequencies were compared statistically with valve surface area, ventral margin thickness, burrowing rate, depth of sediment penetration, shell microstructure, shell ornament, and tissue exposure when valves adducted. Of these comparisons, the only significant correlation was between frequency of embayed repairs and valve surface area. The complex relationship between repair frequency and these variables is underscored by factor analysis. New quantitative approaches are employed that advocate phyletic rather than assemblage-level tests of escalation involving Tertiary congeners from the Atlantic Coastal Plain.

Stability of Cenozoic reefs has been documented previously by assessing stability of coral assemblages; however, the stability of other components of reef communities, such as mollusks, is unknown. To investigate whether reef mollusks form stable associations of species, mollusks from a reef decimated by brief sea-level fall within the Sangamon interglacial were compared to those of the reef that reassembled when sea level returned (after 1100–1500 years) at Cockburn Town, San Salvador Island, Bahamas. Additionally, to investigate whether mollusks within reefs were unique to that environment, assemblages from fossil reefs were compared to the assemblage of the adjacent subtidal carbonate-sand facies.

A total of 54 species and 4832 individuals were observed within twenty-one quadrats of both reefs and the subtidal sand. Taphonomic alteration was documented to determine if taphonomic histories were similar. Taxonomic composition of assemblages was compared with Detrended Correspondence Analysis. To test whether reef mollusk assemblages were distinctive and recurring, MANOVA tests were performed on transformed data with rare taxa excluded. Two null hypotheses were evaluated: (1) H_o: there is no difference in mollusks from different reef building episodes, suggesting stability; and, to test if assemblages from reefs are unique, (2) H_o: there is no difference in mollusks from reefs and subtidal sands.

Reef mollusk assemblages from different periods of reef building were not significantly different. Additionally, reef mollusks formed unique assemblages that were distinct from those of adjacent subtidal sand areas. Taphonomic differences between deposits were minor. Reef mollusks followed the same pattern of stability that has been documented for coral assemblages over longer time intervals. Therefore, despite community reassembly during the late Pleistocene, mollusks associated with the reef communities show evidence of stability.

Annual-oxygen isotope profiles from two live-collected specimens of Chione cortezi Carpenter were analyzed in conjunction with daily growth-increment width profiles and high-resolution temperature records from the same site in the northern Gulf of California. The daily growth-increment profiles serve to date the deposition of the δ¹⁸O samples. Then the δ¹⁸O values were compared with high-resolution temperature records from the same site. Shell deposition began in late March or early April and ended in late November or early December. δ¹⁸O-derived estimates of the maximum and minimum temperature thresholds of growth agree well with those obtained from the dated increment width profile. Shell deposition in these two specimens of C. cortezi from the northern Gulf began when temperature warmed above ∼17°C and slowed or halted when temperature rose above ∼31°C. The temporal resolution of stable isotope samples varies throughout the year. Samples with the coarsest resolution (>3 weeks) were taken from parts of the shell deposited near the minimum and maximum temperature thresholds of growth. Higher resolution samples have intermediate δ ¹⁸O values and most represent less than five days of growth. Calculated temperatures from the dated oxygen-isotope samples are similar to observed temperatures. Differences reflect the effects of daily temperature variation, tidal emergence, and enrichment in δ¹⁸O of the water in which the clams grew. Stable oxygen-isotope samples used in conjunction with increment-width profiles can provide paleoenvironmental information at sub-weekly to sub-monthly resolution.

At Apo Reef, Mindoro, a small, isolated, moderate-energy platform reef in the central Philippines, foraminifera comprise a significant portion (c.40%) of the sediment. This study examines four assemlages of foraminifera: live foraminifera; dead, unabraded foraminifera; abraded and fragmented foraminifera; and the three data sets combined into a total assemblage in order to determine their relative usefulness in identifying reefal sub-environments. The time averaged assemblages, the product of taphonomic processes, prove to be much more effective in delineating reefal physiographic sub-environments than do the live assemblages. The abundance of live foraminifera, except for minute sediment-attached rotaliines, is strongly controlled by the distribution of algal turf and filamentous algal mat. Filamentous algae, with abundant live delicate species, occur in both high- and low-energy reef zones. The time-averaged assemblages are characterized by robust calcarinids in the shallow seaward zones; by free-living miliolids and small rotaliines in the leeward zones; and by planktonics and large thin rotaliines in the fore reef. This enhanced fidelity of the time-averaged assemblages in relation to physiographic zones reflects a combination of the ecological distribution of robust, abrasion-resistant species, the selective destruction of small, delicate tests in higher-energy zones, and the failure of storms and other mechanisms to homogenize the reefal sands.

At the locality of La Posa, Isona, Spain, an extensive Upper Cretaceous bedding plane is exposed and exhibits thousands of ovate prints that had been interpreted as dinosaur tracks. Detailed study of these trace fossils allows the proposal of an alternative hypothesis that they were produced by the feeding activity of rays or other fish with similar behavior. Comparison with modern stingray pits from a tidal flat in Puerto Peñasco, Sonora, Mexico, reveals a great deal of similarity with the Cretaceous trace fossils in their distribution, morphology, environmental setting, and associated invertebrate bioturbation. Moreover, ray body fossils are known from neighboring contemporaneous deposits. The trace fossils here are attributed to the ichnogenus Piscichnnus.