Hydrodynamic behaviour of nummulitids

Großforaminiferen unterschiedlicher systematischer Zugehörigkeit bildeten in verschiedenen geologischen Zeiten mächtige Ablagerungen, die sich räumlich weit erstrecken. Solche Ablagerungen von Nummulites sind über einen Zeitraum von ca. 30 Millionen Jahren vom Jüngeren Paleozän bis in das Ältere Oligozän immer wieder anzutreffen. Die Interpretation der Umweltbedingungen zum Zeitpunkt dieser Ablagerungen war in den letzten 50 Jahren ein heißer Diskussionspunkt. Dies liegt teilweise in den Schwierigkeiten der Interpretation fossiler Gesteine selbst, insbesondere wenn der aktualistische Bezug durch das Fehlen rezenter vergleichbarer Organismen nicht angewendet werden kann. Ein Weg zur Klärung ist die Untersuchung der hydrodynamischen Eigenschaften von Nummuliten-Gehäusen. In den letzten 50 Jahren konnten Sedimentologen in zahlreichen Arbeiten die hydrodynamischen Eigenschaften von Sedimentkörnern erklären, insbesondere was den Transport und die Ablagerung während unterschiedlicher Wasserbewegungen (oszillatorisch oder gerichtet) sowohl im seichten als auch im tieferen Wasser betrifft. Zur selben Zeit erklärten Paläontologen die Verbreitung lebender Groß-Foraminiferen unter Verwendung komplexer statistischer Methoden. Mit diesem Datensatz ist es nun möglich, mit wenigen Kennzahlen (Parametern), die Anreicherung der fossilen Formen zu erklären. Innerhalb der Nummuliten, bei denen zahlreiche Gehäusemerkmale von Umweltbedingungen beeinflusst wurden, benötigt man nur zwei, nämlich die Gehäuseform und die Dichte, um das Abheben, die Transportweite und das Absinken zu berechnen. Zur Berechnung der beiden oben genannten Kennzahlen genügen zwei Abmessungen, nämlich der Gehäusedurchmesser und die Gehäusedicke. Nach Berechnung der hydrodynamischen Parameter wurden diese mit experimentellen Werten verglichen. Da diese Korrelation extrem signifikant ist, lassen sich die hydrodynamischen Parameter für alle Formen mit nummulitiden Gehäusen berechnen. Die Transportfähigkeit der Gehäuse konnte anhand ihrer Sinkgeschwindigkeit definiert werden: man findet Foraminiferen am häufigsten in jener Wassertiefe, wo die Wasserenergie schon zu schwach ist, um die Gehäuse abzuheben. Weil die Foraminiferen, um die Photosynthese ihrer Symbionten zu ermöglichen, so viel Licht wie möglich zu absorbieren versuchen, leben sie bevorzugt in jener kritischen Tiefe, wo einerseits das Licht noch intensiv ist, andererseits die Wasserenergie nicht zu hoch ist. Um vom Substrat nicht abgehoben zu werden, müssen die Foraminiferen Gehäuse mit bestimmten Widerstandkoeffizienten bauen. Durch die hohe Korrelation zwischen den hydrodynamischen Gehäuseparametern und der Wasserenergie, die durch die oszillatorische Wellenbewegung am Boden wirkt, lässt sich die durchschnittliche Wassertiefe, in der die Foraminiferen lebten, ermitteln. Wichtig ist jedoch, dass nicht nur die Transportfähigkeit der Gehäuse, sondern auch die Funktion von strukturellen Gehäusemerkmalen die Tiefeverteilung der einzelnen Arten charakterisieren.Larger foraminifera occurred abundantly in many Paleogene shelf carbonate platforms and were influenced by global and local factors. Ecology (e.g. temperature), geology (e.g. sea level changes) and evolution (e.g. population dynamics) affect the abundance and structure of larger foraminiferal communities. Water motion is the most important physical factor in shallow water environments directing the distribution of living individuals, and the distribution of empty shells mainly follows the input produced by water motion. The relationship between the biotic composition and the fossil association must always be taken into account for interpreting the palaeoenvironment. The shape of nummulitids and its relation with systematics on the one and water motion on the other side allows fascinating results. Concerning larger foraminifera, especially nummulitids, shape variation, size and internal structures are highly correlated with taxonomy. These parameters strongly influence the distribution of foraminiferal tests on a slope induced by water motion. Because of these correlations, estimations of palaeodepth can be based on the species distribution in the fossil environment. The calculation to obtain the hydrodynamic answer of nummulitid tests was applied to species belonging to the genera Nummulites and Assilina, as well as to some operculinids. The value of the hydrodynamic answer of a single test considers size, shape and density, and it is the combination of these variables that express the hydrodynamic behaviour of the specimen. Consequently, the diversity of forms collected within a layer is characterized by the same hydrodynamic behaviour. From a palaeoenvironmental point of view, due to sorting induced by water motion, transported tests with similar hydrodynamic behaviour are deposited in the same hydrodynamic environment. The measured and the calculated parameters allowed the definition of transport / deposition boundary and the location of accumulation areas

Growth oscillation in larger foraminifera

This work shows the potential for applying three-dimensional biometry to studying cell growth in larger benthic foraminifera. The volume of each test chamber was measured from the three-dimensional model obtained by means of computed tomography. Analyses of cell growth based on the sequence of chamber volumes revealed constant and significant oscillations for all investigated specimens, characterized by periods of approximately 15, 30, 90, and 360 days. Possible explanations for these periods are connected to tides, lunar cycles, and seasonality. The potential to record environmental oscillations or fluctuations during the lifetime of larger foraminifera is pivotal for reconstructing short-term paleoenvironmental variations or for gaining insight into the influence of tides or tidal current on the shallow-water benthic fauna in both recent and fossil environments. \uc2\ua9 2014 The Paleontological Society

Growth Rate Biometric Quantification by X-ray Microtomography on Larger Benthic Foraminifera: Three-dimensional Measurements Push Nummulitids into the Fourth Dimension

This work demonstrates the potential of three-dimensional biometric quantification using microtomography on larger benthic foraminifera. We compare traditional linear and area measures used for calculating three-dimensional characters with actual 3D measurements made from volume images obtained using X-ray microtomography (microCT). Two specimens of recent larger benthic foraminifera, i.e., Palaeonummulites venosus and Operculina ammonoides, were imaged with a high-resolution microCT scanner. This method enables three-dimensional imaging and calculation of measurements like 3D distances, surfaces and volumes. The quantitative high-resolution images enabled the extraction of the lumina from the proloculus to the last complete scanned chamber and of the canal system spreading into marginal chord and septa. External surfaces and volumes were calculated on the extracted parts. These measurements allowed the calculation of porosity and microporosity to obtain the test density, which is the basis for many inferences about foraminifera, e.g., reconstructions of transport and deposition. Volume and surface measurements of the proloculus allow the calculation of sphericity deviation, which is useful for determining evolutionary trends in species based on individuals resulting from asexual reproduction (A forms). The three-dimensional data presented here show the actual growth of the foraminiferal cell and the development of the test. Measurements made on an equatorial section cannot be considered representative of a three-dimensional test, unless a correspondence between 2D data with 3D data shows significant correlation. Chamber height, septal distance, spiral growth and chamber area were measured on the equatorial section and correlated with the volume measurements from 3D images to determine the predictive value of the 1D and 2D measures for estimating the 3D morphological parameters. In particular, we show that the equatorial section area of chambers correlates significantly with the chamber volume and can be used to differentiate between nummulitid genera according to their different growth patterns. \uc2\ua9T\uc3\u9cB\uc4\ub0TAK

Lunar cycles and rainy seasons drive growth and reproduction in nummulitid foraminifera, important producers of carbonate buildups

Representatives of the foraminifer Nummulites are important in Earth history for timing Cenozoic shallow-water carbonates. Taphonomic complexity explains the construction of carbonate buildups, but reproduction and life span of the constructing individuals are unknown. During the 15-month investigation period, asexually reproduced schizonts and gamonts showed equal proportions in the first half of this period, whereas gamonts predominated in the second half. Oscillations in cell growth are mainly caused by light intensities during chamber construction when minor differences in water depth increase the photosynthetic rate of endosymbiotic diatoms during neap tides. The continuous reproduction rate of N. venosus throughout the year is increased in subtropical calms by higher summer temperatures and the marginal input of inorganic nutrients during rainy seasons. The expected life span of both gamonts and schizonts are 18 month

Growth of Heterostegina depressa under natural and laboratory conditions

The use of micro-computed tomography (\uce\ubcCT) provides a unique opportunity to look inside the shells of larger benthic foraminifera to investigate their structure by measuring linear and volumetric parameters. For this study, gamonts/schizonts and agamonts of the species Heterostegina depressa d'Orbigny were examined by \uce\ubcCT; each single chamber's volume was digitally measured. This approach enables cell growth to be recognised in terms of chamber volume sequence, which progressively increases until reproduction occurs. This sequence represents the ontogeny of the foraminiferal cell and has been used here to investigate controlling factors potentially affecting the process of chamber formation. This is manifested as instantaneous or periodic deviations of the realised chamber volumes derived from modelled growth functions. The results obtained on naturally grown specimens show oscillations in chamber volumes which can be modelled by sums of sinusoidal functions. A set of functions with similar periods in all investigated specimens points to lunar and tidal cycles.To determine whether such cyclic signals are genuine and not the effects of a theoretical model, the same analysis was conducted on specimens held in a closed laboratory facility, as they should not be affected by natural environmental effects. Surprisingly, similar cyclicities were observed in such samples. However, a solely genetic origin of these cycles couldn't be verified either. Therefore, detailed analysis on the phase equality of these growth oscillations have been done. This approach is pivotal for proving that the oscillatory patterns discovered in LBF are indeed genuine signals, and on how chamber growth might be influenced by tidal currents or lunar months

Flammability reduction in a pressurised water electrolyser based on a thin polymer electrolyte membrane through a Pt-alloy catalytic approach

Various Pt-based materials (unsupported Pt, PtRu, PtCo) were investigated as catalysts for recombining hydrogen and oxygen back into water. The recombination performance correlated well with the surface Pt metallic state. Alloying cobalt to platinum was observed to produce an electron transfer favouring the occurrence of a large fraction of the Pt metallic state on the catalyst surface. Unsupported PtCo showed both excellent recombination performance and dynamic behaviour. In a packed bed catalytic reactor, when hydrogen was fed at 4% vol. in the oxygen stream (flammability limit), 99.5% of the total H 2 content was immediately converted to water in the presence of PtCo thus avoiding safety issues. The PtCo catalyst was thus integrated in the anode of the membrane-electrode assembly of a polymer electrolyte membrane electrolysis cell. This catalyst showed good capability to reduce the concentration of hydrogen in the oxygen stream under differential pressure operation (1-20 bar), in the presence of a thin (90 µm) Aquivion® membrane. The modified system showed lower hydrogen concentration in the oxygen flow than electrolysis cells based on state-of-the-art thick polymer electrolyte membranes and allowed to expand the minimum current density load down to 0.15 A cm -2 . The electrolysis cell equipped with a dual layer PtCo/IrRuOx oxidation catalyst achieved a high operating current density (3 A cm -2 ) as requested to decrease the system capital costs, under high efficiency conditions (about 77% efficiency at 55°C and 20 bar). Moreover, the electrolysis system showed reduced probability to reach the flammability limit under both high differential pressure (20 bar) and partial load operation (5%), as needed to properly address grid-balancing service

Morphological variations in Cycloclypeus carpenteri: Multiple embryos and multiple equatorial layers

In this work, 17 specimens of Cycloclypeus carpenteri have been analysed by means of microCT scanning. It has been observed that many specimens possess multiple embryos, multiple nepionts and some tests show more than one equatorial layer. The diameter of each proloculus has been measured, and it seems that they are very variable even within the same specimen, therefore questioning the long known theory that schizonts have smaller proloculi than gamonts and also questioning the fact that proloculi in the same species should all have comparable size. Whenever the nepionts are positioned on different planes, thus creating an angle between them, this angle has a significant correlation to the angle connecting different equatorial layers. T-shaped connections are located at the junction between two equatorial layers; these junctions are made by a chamberlet, which possesses an unusually higher number of apertures, resembling the chamberlet structure of the genus Spiroclypeus

Strontium isotope stratigraphy of late Cenozoic fossiliferous marine deposits in North Borneo (Brunei, and Sarawak, Malaysia)

Neogene marine deposits of North Borneo are locally very rich in fossils that provide glimpses into the past biodiversity. However, dating these onshore sediments with biostratigraphy is often hampered by the lack and/or the poor preservation state of index fossils. Therefore, the fossiliferous sites were targeted with strontium isotope stratigraphy (SIS) to obtain higher precision relative dating. Well-preserved macrofossils were screened using a multidisciplinary approach, and 87Sr/86Sr ratios of the most pristine remains were used to date the embedding sediments. Most of the measured ages fall in the expected chronostratigraphic framework established by large scale studies for the region. The oldest, Burdigalian (early Miocene) ages were measured for the Sibuti Formation in Sarawak (17.71 \ub1 0.2My and 16.7 \ub1 0.2My) followed by a Serravallian (middle Miocene) age within the Belait Fm in Brunei (12.1 +1.4/-1.2My). Eight localities from the younger units, the Miri and Seria formations in Brunei, gave a range in age from 10.5 \ub1 1 to 7.0 +0.9/-0.5My (Tortonian-Messinian). Reworked fossil assemblages from Tutong beach were also investigated and the SIS ages of Late Miocene support an origin from the younger part of the Seria Fm. One locality, in Lumapas where limestone crops out in Brunei, gave an unexpected younger age (Tortonian, late Miocene, 10.6 \ub1 1My) compared to estimates projected for its assumed stratigraphic position in the lower Belait Formation (late Burdigalian). These challenging data require more research, yet if the young age is accepted, the stratigraphic situation of the limestone needs further revision