Carbonate clumped isotope thermometry is a powerful tool for reconstructing paleotemperature and paleosalinity. Despite its broad application in biotic and abiotic materials, its use in paleoclimate studies has been limited due to the large amount of material and high precision required for each temperature estimate. In addition, it is still uncertain to what extent the clumped isotope signal is modified during calcification in various organisms. Using an analytical approach that minimizes sample size, we analysed clumped isotopes (Delta(47)) in two bivalve shells from the upwelling-dominated Gulf of Panama to reconstruct seasonal temperature and salinity variations. Using the high-resolution profiles in delta O-18(shell), we grouped Delta(47) measurements into several intervals to obtain robust average temperature estimates. The reconstructed temperatures agree with available observational data at the 95% confidence level, reflecting seasonal temperature changes of at least similar to 6 degrees C. By combining bivalve delta O-18(shell) and Delta(47)-based temperatures, we obtain realistic estimates of seasonal delta O-18(seawater) and salinity changes. Our results suggest that clumped isotopes in bivalve shells can be used for seasonal temperature reconstructions and for disentangling the temperature and delta O-18(seawater) signals in delta O-18(shell) variations. (C) 2020 The Authors. Published by Elsevier Ltd.

Paired lithium-to-calcium (Li/Ca-shell) and oxygen isotope (delta O-18(shell)) ratios were measured in four aragonitic Megapitaria aurantiaca bivalve shells from the tropical Eastern Pacific and evaluated with respect to their linkage to seasonal coastal upwelling. The Li/Ca-shell and delta O-18(shell) of two specimens from the upwelling-dominated Gulf of Panama are positively correlated and consistently reveal large seasonal variations of up to similar to 300 mu mol/mol and similar to 3 parts per thousand, respectively. The Li/Ca-shell and delta O-18(shell) of two shells from the adjacent non-upwelling Gulf of Chiriqui are not correlated and show a reduced seasonal variability rarely exceeding 20 mu mol/mol and similar to 1.0 parts per thousand, respectively. In some M. aurantiaca specimens the Li/Ca-shell shows a weak positive correlation with growth increment width, indicating that physiological growth rate effects might in part control the 'background' Li/Ca-shell. Unambiguous seasonal delta O-18(shell) signals, used for a precise chronology for a live-collected specimen from the Gulf of Panama, imply that distinct parallel peaks in Li/Ca-shell and delta O-18(shell) mark the cold and highly productive coastal upwelling season during February to April. A comparison with environmental data reveals a negative correlation between Li/Ca-shell and water temperature, and a strong positive correlation between Li/Ca-shell and chlorophyll a in the Gulf of Panama. While a causal link between Li/Ca-shell and temperature remains uncertain, we argue that Li/Ca-shell peaks in M. aurantiaca are consistent with the concept of an incorporation of additional Li provided by diatom-dominated phytoplankton blooms during coastal upwelling. Our findings suggest that Li/Ca-shell in M. aurantiaca may serve as a new proxy for seasonal coastal upwelling, the potential of which should be tested for other mollusk species and upwelling regions.

Four trepostome bryozoan species are described from the Upper Triassic of New Caledonia. They include one new genus Metastenodiscus n. gen. The studied fauna shows strong paleobiogeographic relations to New Zealand and less so to Japan. Morphological similarities between Middle Paleozoic and Triassic trepostome bryozoans (e.g., abundant diaphragms) are explained by homeomorphy.

In this study two carbonate environments are compared and contrasted; the Gulf of Panama and the Gulf of Chiriqui on the Pacific side of Panama. These two embayments are in close geographic proximity at latitudes between 7 degrees N and 9 degrees N. The Gulf of Panama and the Gulf of Chiriqui are characterized by contrasting oceanographic conditions with year-round stable non-upwelling conditions in the Gulf of Chiriqui and strong seasonal upwelling in the dry season (December to April) in the Gulf of Panama. The upwelling variations only have a limited influence on the amount of carbonate produced; however, they do have a major impact on the occurrence of specific carbonate producing biota. In addition, carbonate production and distribution is influenced in both gulfs by the occurrence of islands and by terrigenous input. Terrigenous material is found mainly in the smaller grain sizes (<63 to 250 mu m) that can be transported easily by currents and waves. Carbonate dominant sediments (carbonate sands and mixed carbonate-siliciclastic sands) mainly occur around the islands and are dominated by larger grain-sizes (>500 mu m). The Gulf of Panama and the Gulf of Chiriqui both show warm and temperate carbonate-producing biota, with carbonate producers from tropical (corals) to mixed tropical to cool-water (coralline red algae) and cold-water (balanids) environments. The Gulf of Chiriqui is characterized by oligotrophic to mesotrophic conditions resulting in a photozoan (coral) and/or rhodolith-facies in shallow-water areas surrounding the islands and a mollusc-dominated facies in deeper waters towards the shelf edge. Seasonal upwelling causes temporary eutrophic conditions in the Gulf of Panama, which results in a heterozoan facies around the islands dominated by balanids, echinoderms and molluscs. Thus a cool-water carbonate fauna and eutrophic conditions can exist in the tropics within an area prone to seasonal upwelling. The distinct facies differences found on the Pacific shelf of Panama stress the importance of variations in oceanographic conditions, upwelling versus non-upwelling, in determining carbonate production and associated facies patterns in the tropics.

Distribution, growth rate, and carbonate production of non-geniculate and unattached coralline red algal beds (rhodoliths) were studied in the Gulfs of Panama and Chiriqui along the Pacific coast of Panama. This is the first attempt to quantify coralline carbonate production in this region based on a newly developed algorithm. Although situated at the same latitude, the two gulfs are characterized by distinctly different environmental conditions; Chiriqui is mesotrophic throughout the year, whereas the Gulf of Panama is eutrophic due to intense seasonal upwelling. Coralline algal carbonate production is similar to 10x greater in the Gulf of Chiriqui (11.258 x 10(10) gr CaCO3 yr(-1)) than in the Gulf of Panama (1.69 x 10(10) gr CaCO3 yr(-1)), which is characterized mostly by siliciclastics with minor carbonates. Corallines display a patchy distribution in both gulfs being concentrated mainly around the islands. In Chiriqui, they occur as thin crusts as well as massive-nodular and open-branching growth types; encrusting types are most common in the Gulf of Panama. Growth rates of branching corallines were calculated based on annual growth bands matched to their skeletal Mg/Ca ratios. Ratios are higher in the less dense portions of growth bands corresponding to higher growth rates during the dry season, whereas both Mg/Ca ratios and growth rates in the dense portions (wet season) drop. Growth rates of branch tips in both sites are similar to those reported from other temperate-subtropical regions. Extremely slow growth rates combined with the old ages of individual thalli document the overall stability of this algal ecosystem.

The Miocene to Pleistocene Limon Group of Costa Rica is a mixed carbonate-siliciclastic succession that formed in association with the emergence of the Central American Isthmus. Our study focuses on a lower Late Pliocene reef unit, the newly excavated Contact Cut, which is located at the contact between the siliciclastic sediments of the Rio Banano Formation and the mixed reefal and coral bearing deposits and siliciclastic sediments of the Quebrada Chocolate Formation. The siliciclastic sediments were deposited in a thick, deltaic setting sourced by erosion of the Cordillera de Talamanca. Deposits of the Limon Group preserve a sequence of progressively shallowing, near-shore sediments that were exposed by uplift during the early to middle Pleistocene.The Contact Cut outcrop shows the first reef sequence in the stratigraphic sequence and thus illustrates the reestablishment of Caribbean coral reef predominance in the Neogene. It shows extensive reef growth during a rise in sea level and a slight progradation during the succeeding sea-level highstand. Three stages of reef evolution are recognized based on faunal diversity. The Contact Cut reef complex is comparable to the time equivalent reef of the Las Islas roadcut, situated west of Limon, which shows a rapid burial of the corals by siliciclastics. Both reefs document a distinct facies diversification during the final stages of the closing of the Central American Seaway. The reefs developed in an environment stressed by siliciclastic input, which ultimately caused a decrease in coral diversity and abundance followed by a temporary demise of the reefs. The biotic composition of the patch reefs that occurred during the sea-level rise, Las Islas and Contact Cut, did not differ from the reefs that developed during the final highstand in sea level, the reefs of the overlying Moin formation (Limon Group). Differences in the position on the shelf relative to the source of the siliciclastics might have been the cause for the different response to the rise in sea level of the transgressive reefs, with a very fast give up scenario for Las Islas reef and a catch up followed by a give up phase for Contact Cut reef. (C) 2011 Elsevier B.V. All rights reserved.

Carbonate production and benthic mollusk abundance and diversity were studied in a series of samples from the Gulfs of Panama and Chiriqui to investigate the contribution of coralline algae to carbonate production and its role in benthic community structure. Preliminary results show that maerl and rhodoliths are important components of the shelf contributing significantly to the total carbonate production, which is much higher in the Gulf of Chiriqui. Silty and sandy-mud bottoms predominate in the Gulf of Panama, while a mixture of marel, rhodoliths and coral is commonly found in the Gulf of Chiriqui. Corallines support multilayered communities, with a low trophic diversity, few predators, abundant sessile forms, thick-shelled grazers and detritus feeders. Material is highly bio-eroded and incrustated. Soft sediment communities are dominated by thin-shelled, well preserved filter feeders and vagile predators.

Abstract From the Aseelah Unit (Saal Formation), Batain Coast (eastern Oman), 48 bryozoan species were described. Eight species of them are new: cystoporids Cystodictya angusta n. sp. and Sulcoretepora orientalis n. sp., trepostomid Ulrichotrypella omanica n. sp., rhabdomesids Streblotrypa (Streblotrypa) binodata n. sp., Rhabdomeson coniforme n. sp., R. latum n. sp., Orthopora punctata n. sp., and phyloporine Rhombocladia quasiminor n. sp. A new combination is erected: Streblotrypa (Strebloscopora) katoi Sakagami, 2000 n. comb. Fifteen species are described in open nomenclature. The fauna shows mainly Lower to Middle Permian age, and paleobiogeographic connections to the Urals, southeast Asia and Australia.

A novel technique was applied to estimate differences in core shortening in three gravity cores taken at the same core location on the Portuguese continental slope using different coring devices. No obvious deformational features are visible in the fresh core sediments; the isotope stratigraphy and abundance maxima of ice-rafted debris, representing North Atlantic Heinrich-events, indicate identical stratigraphic range in all three cores. However, one of the cores is significantly shorter than the others. X-ray radiographs of the cores reveal that the shorter core shows typical deformation structures, whereas the two other cores are lacking signs of deformation. This serious disturbance had likely gone unnoticed had it not been for the X-ray radiographs. As an approach to semi-quantitatively estimate the core shortening, we used the fragmentation and displacement of the pyritized trace fossil Trichichnus that is easily recognizable in X-ray radiographs through its high contrast. The Trichichnus data indicate that a shortening of 50–60% occurred in the lower part of the shorter core. This estimate is in good agreement with variations in apparent sedimentation rates for the interval considered. Accurate flux rates are essential for our understanding marine biogeochemical cycles in general and the marine budgets of nutrients such as carbon and phosphorus in particular. X-ray radiographs are very useful in assessing the intactness of the sedimentary records and the presented method has potential to become a valuable tool in correcting sedimentation rates in disturbed gravity cores.