Abstract Geologic Problem Solving with Microfossils: A Volume in Honor of Garry D. Jones SEPM Special Publication No. 93, Copyright © 2008 SEPM (Society for Sedimentary Geology), ISBN 978-1-56576-137-7, p. 83–92. Beds of benthic macro-vegetation are important in shallow-water, carbonate-producing regimes. Seagrass blades baffle currents, leading to deposition of fine sediment, and grass root systems effectively bind the sediment, preventing erosion. Seagrass and benthic macroalgae are substrates for a variety of epibionts, including foraminifera. Due to their higher preservation potential, foraminifera can be used as proxies in studies of ancient vegetation-bed environments. In this actualistic study, we investigated the potential of using foraminifera to reconstruct the taxonomic composition and density of the vegetation, water depth, and a range of other environmental variables. At each of the six localities selected, vegetation densities were recorded in 50 cm x 50 cm grids located at 10 m intervals along transects. A sediment sample from the top 1 cm of the seafloor was taken at each station, and samples of each of the major genera of vegetation algae, seagrass, and macroalgae were collected at each locality. In the laboratory, vegetation was examined, and relatively large foraminifers were picked from the 2.0–0.5 mm sediment fractions. Total foraminiferal density was recorded as the number of individuals per plant and per gram of sediment picked. Dead foraminifers were categorized by taphonomic condition: pristine, good, altered, and extremely altered. Sorites and Planorbulina are the dominant large foraminifers living on the preferred substrates, Thalassia and Halimeda , in proportions that vary according to locality. However, sediment assemblages are dominated by Archaias, Cyclorbiculina , and Valvulina , with very few live individuals. In vegetation beds dominated by seagrasses, foraminiferal density in the sediment appears to reflect the standing Thalassia density to a degree, but maximum test density occurs in moderately dense seagrass beds. The most reliable proxy for the presence and density of seagrass beds is the relatively high quality of test preservation as assessed by the quality of preservation index (QPI), the percent of live, pristine, and good tests in an assemblage. Medium- to high-density seagrass beds consistently rank in the range of 70–85%, whereas sparse beds are much lower. In addition, processes of alteration, such as abrasion versus encrustation and cementation, are promising areas for further study. These preliminary results indicate strongly that taphonomic state and mode of alteration should be included in future carbonate-platform foraminiferal studies

A bstract Upper Cenomanian limestones exposed in southern and western Istria, Croatia, are rich in radiolitid remains and also containdinosaur footprints. As documented in measured sections at Lovrecica, Ladin Gaj, Grakalovac, and Fenoliga, as well as in a new sectionat Karigador, rudists and dinosaur tracks occur together in peritidal sediments that are organized into shallowing-up cycles. These cycleswere deposited in the interior of the carbonate platform and are commonly capped by intertidal laminites. At these localities, the rudistsare elevator types and mud-supported sediment dwellers that thrived in the soft substrate where dinosaurs made footprints. Dinosaurtracks are preserved in both types of subtidal limestones, and radiolitid congregations are laterally discontinuous in foraminiferal-peloidal limestone. The presence of dinosaur footprints on the upper bedding plane of rudist floatstone implies that the Istrian part of the Late Cenomanian carbonate platform was a shallow, protected platform interior. Dinosaurs strode across the muddy bottom of the shallow-water platformin water depths equivalent to their estimated hip heights. These dinosaur-track-rich levels in Upper Cenomanian shallow marinelimestones of the Adriatic carbonate platform underlines the relevance of dinosaur footprints as a tool for paleoenvironmental reconstruction.

Abstract The Mesozoic, mid-Cretaceous (Barremian to Cenomanian) deposits of southern Croatia comprise a succession of shallow tropical-water, inner-platform deposits that formed on a Bahama-type isolated Adriatic carbonate platform in the Dinarides. This succession is dominated by benthic foraminifers and dasycladalean algae, and is exposed in a nearly continuous outcrop section on the islands and along the coast of southern Croatia. It has been studied in terms of sedimentary facies, paleoecology, and biostratigraphy. The present study documents that several species of benthic foraminifers (cuneolinids, orbitolinids, alveolinids) and dasycladalean algae (Salpingoporella) have exceptional age-diagnostic value for mid-Cretaceous biostratigraphy. These are abundant, and they have a widespread distribution and a restricted stratigraphic range. They evolved rapidly and became extinct suddenly. The mid-Cretaceous benthic associations, including a total of 106 species and 57 genera of benthic foraminifers and 48 species and 20 genera of dasycladalean algae, were analyzed to establish the principal diversity patterns at (sub)stage level of resolution. The Early Aptian marked the foraminiferal diversity maximum, whereas significant diversity drops are recorded in the Late Aptian and Early Cenomanian. The foraminiferal distribution within the oligotrophic habitats of the platform interior was controlled primarily by relative sea-level oscillations, variations in oceanic circulation rate, and nutrient availability in surface waters. There is a positive correlation between episodes of increased diversification and the regional relative sea-level rises, whereas regressive episodes resulted in reduction of oligotrophic habitats and decreased species richness. The dasycladaleans were the most diversified during the tidal-flat-dominated Barremian, and from that peak diversity decreased through the Early Aptian. A significant diversity drop occurred in the Late Aptian, and it was contemporaneous with the maximum abundance of Salpingoporella dinarica . The mid-Cretaceous dasycladaleans never fully recovered from the Early Aptian platform deepening event, and their post-Aptian diversity pattern implies dependence on factors other than relative sea level and associated changes in habitats. Geologic Problem Solving with Microfossils: A Volume in Honor of Garry D. Jones SEPM Special Publication No. 93, Copyright © 2009 SEPM (Society for Sedimentary Geology), ISBN 978-1-56576-137-7, p. 153–170.