Chemostratigraphy and stratigraphic distribution of keeled planktonic foraminifera in the Cenomanian of the North German Basin

The record of keeled planktonic foraminifera during the Cenomanian in boreal epicontinental basins is discontinuous. Micropalaeontologic and bulk carbonate carbon and oxygen isotope investigations from two cores in the centre of the North German Basin (NGB, Wunstorf, Lower Saxony) showed keeled praeglobotruncanids and rotaliporids to exclusively appear during three stratigraphic intervals of varying duration in the lower and middle Cenomanian. Our new highresolution carbon isotope (\u3b413Ccarb) composite curve shows that keeled foraminifera are absent during the Mid-Cenomanian Event (MCE) I. In the aftermath of MCE I, keeled planktonic foraminifera are present throughout. The data are correlated to previously published sequence stratigraphic models for the NGB. The presence/absence of keeled planktonic foraminifera in the epicontinental NGB is believed to be controlled by sea level and according environmental conditions in the epicontinental basin.In den Cenoman-zeitlichen Abfolgen der epikontinentalen Becken der borealen Kreide lassen sich gekielte planktonische Foraminiferen nicht durchgehend nachweisen. Neue Untersuchungen an zwei Bohrungen aus dem Norddeutschen Becken bei Wunstorf in Niedersachsen zeigen, dass sich die Vorkommen von gekielten Praeglobotruncanen und Rotaliporiden auf drei stratigraphisch klar abtrennbare Intervalle des Untercenomaniums und Mittelcenomaniums beschr\ue4nken. Die hier pr\ue4sentierte neue und hochaufl\uf6sende Kohlenstoffisotopenkurve (\u3b413Ccarb) belegt u ferdem ein Fehlen gekielter planktonischer Foraminiferen w\ue4hrend der positiven C-Isotopen-Exkursion des Mid-Cenomanian Event (MCE) I. Oberhalb des MCE I ist das Vorkommen gekielter planktonischer Foraminiferen kontinuierlich. Die Korrelation unserer Daten mit etablierten sequenzstratigraphischen Untergliederungen f\ufcr das Cenomanium Norddeutschlands weist auf einen Zusammenhang zwischen Meeresspiegelschwankungen und dem Vorkommen gekielter Formen hin. Offensichtlich erm\uf6glichten die Umweltbedingungen w\ue4hrend hoher Meeresspiegelst\ue4nde das Leben gekielter Formen in den Randbecken

Single-stage, single-phase, ac–dc buck–boost converter for low-voltage applications

The suitability of a single-stage ac–dc buck–boost converter for low-voltage applications is investigated. In-depth discussion and analysis of the converter's operating principle, basic relationships that govern converter steady-state operation and details of the necessary control structures needed to comply with the grid code are provided. The validity of the proposed system is confirmed using power system computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) simulations, and is substantiated experimentally. The buck–boost converter under investigation has good dynamic performance in both buck and boost modes, and ensures near unity input power factor over the full operating range, whilst having fewer devices and passive elements than other published versions of the buck–boost converter

Along-Path Evolution of Biogeochemical and Carbonate System Properties in the Intermediate Water of the Western Mediterranean

A basin-scale oceanographic cruise (OCEANCERTAIN2015) was carried out in the Western Mediterranean (WMED) in summer 2015 to study the evolution of hydrological and biogeochemical properties of the most ubiquitous water mass of the Mediterranean Sea, the Intermediate Water (IW). IW is a relatively warm water mass, formed in the Eastern Mediterranean (EMED) and identified by a salinity maximum all over the basin. While it flows westward, toward and across the WMED, it gradually loses its characteristics. This study describes the along-path changes of thermohaline and biogeochemical properties of the IW in the WMED, trying to discriminate changes induced by mixing and changes induced by interior biogeochemical processes. In the first part of the path (from the Sicily Channel to the Tyrrhenian Sea), respiration in the IW interior was found to have a dominant role in determining its biogeochemical evolution. Afterward, when IW crosses regions of enhanced vertical dynamics (Ligurian Sea, Gulf of Lion and Catalan Sea), mixing with surrounding water masses becomes the primary process. In the final part of the investigated IW path (the Menorca-Mallorca region), the role of respiration is further masked by the effects of a complex circulation of IW, indicating that short-term sub-regional hydrological processes are important to define IW characteristics in the westernmost part of the investigated area. A pronounced along-path acidification was detected in IW, mainly due to remineralization of organic matter. This induced a shift of the carbonate equilibrium toward more acidic species and makes this water mass increasingly less adequate for an optimal growth of calcifying organisms. The carbonate buffering capacity also decreases as IW flows through the WMED, making it more exposed to the adverse effects of a decreasing pH. The present analysis indicates that IW evolution in the sub-basins of the WMED is currently driven by complex hydrological and biogeochemical processes, which could be differently impacted by coming climate changes, in particular considering expected increases of extreme meteorological events, mainly due to the warming of the Mediterranean basin

Age, depositional history and tectonics of the Indo-Myanmar Ranges, Myanmar

The Indo-Myanmar Ranges make up an enigmatic mountain belt occupying a complex tectonic zone in western Myanmar, extending from the northern continuation of the active Sunda–Andaman arc into the eastern Himalayan Syntaxis. The Indo-Myanmar Ranges are part of an accretionary forearc basin–arc complex that includes the Central Myanmar Basin and the Wuntho–Popa Arc to the east. New biostratigraphic, petrological and detrital zircon U–Pb age data are presented and used to test and refine the divergent tectonic models that have been proposed for western Myanmar. These data suggest that: (1) the Upper Triassic Pane Chaung Formation was originally deposited adjacent to the NE Indian continental margin within northern Gondwana during the Late Triassic; and (2) the Upper Cretaceous–Paleogene rocks of the Indo-Myanmar Ranges were mainly derived from the Wuntho–Popa Arc and Inner Belt, with a subordinate input from a crustal source, potentially from the Naga metamorphic-type Paleozoic basement. The Kalemyo Ophiolite has an Early Cretaceous age similar to the ages of ophiolites in the Indus–Yarlung Tsangpo Suture Zone, south Tibet and Nagaland, reinforcing the hypothesis that they were once part of the same Neotethyan ocean floor. Supplementary material: Sample locality details, detailed methodologies and geochemical data are available at https://doi.org/10.6084/m9.figshare.c.648710

Did Late Cretaceous cooling trigger the Campanian–Maastrichtian Boundary Event?

The Campanian-Maastrichtian (83-66 Ma) was a period of global climate cooling, featuring significant negative carbon-isotope (delta C-13) anomalies, such as the Late Campanian Event (LCE) and the Campanian-Maastrichtian Boundary Event (CMBE). A variety of factors, including changes in temperature, oceanic circulation and gateway opening, have been invoked to explain these delta C-13 perturbations, but no precise mechanism has yet been well constrained. In order to improve our understanding of these events, we measured stable carbon and oxygen isotopes of hemipelagic sediments from the Shuqualak-Evans cored borehole (Mississippi, USA) and compared the data with previously published sea-surface temperature (SST) estimates from the same core. We found that the CMBE can be recognised, unambiguously, in the Shuqualak-Evans core, and that it is associated with an interval of cooler SSTs suggesting a possible mechanistic link between palaeotemperat ure change and this event. Determining the precise position of the LCE in the Shuqualak-Evans core is more problematic, but it may also be associated with cooler SSTs. Our combined records of carbon cycling and SSTs compare well with other studies and provide evidence that cooling during the CMBE (and possibly LCE) was global in nature and affected surface waters, in addition to the deep-ocean. We suggest that short-term cooling drove intensification of high-latitude deep-water formation, which in turn led to changes in the ratio of carbonate to organic carbon burial that led to a negative delta C-13 excursion. Critically, the absence of warming during these intervals implies that the Late Cretaceous events must not have been associated with an appreciable increase in atmospheric pCO(2), and was likely associated with decreased pCO(2)

High resolution multibeam and hydrodynamic datasets of tidal channels and inlets of the Venice Lagoon

Tidal channels are crucial for the functioning of wetlands, though their morphological properties, which are relevant for seafloor habitats and flow, have been understudied so far. Here, we release a dataset composed of Digital Terrain Models (DTMs) extracted from a total of 2,500 linear kilometres of high-resolution multibeam echosounder (MBES) data collected in 2013 covering the entire network of tidal channels and inlets of the Venice Lagoon, Italy. The dataset comprises also the backscatter (BS) data, which reflect the acoustic properties of the seafloor, and the tidal current fields simulated by means of a high-resolution three-dimensional unstructured hydrodynamic model. The DTMs and the current fields help define how morphological and benthic properties of tidal channels are affected by the action of currents. These data are of potential broad interest not only to geomorphologists, oceanographers and ecologists studying the morphology, hydrodynamics, sediment transport and benthic habitats of tidal environments, but also to coastal engineers and stakeholders for cost-effective monitoring and sustainable management of this peculiar shallow coastal system

Testing the robustness of primary production models in shallow coastal areas: a case study

In this paper we investigate the robustness of a dynamic model, which describes the dynamic of the seagrass Zostera marina, with respect to the inter-annual variability of the two main forcing functions of primary production models in eutrophicated environments. The model was previously applied to simulate the seasonal evolution of this species in the Lagoon of Venice during a specific year and calibrated against time series of field data. In the this paper, we present and discuss the results which were obtained by forcing the model using time series of site-specific daily values concerning the solar radiation intensity and water temperature. The latter was estimated by means of a regression model, whose input variable was a site-specific time series of the air temperature. The regression model was calibrated using a year-long time series of hourly observations. The Z marina model was first partially recalibrated against the same data set that was used in the original paper. Subsequently, the model was forced using a 7-year-long time series of the driving functions, in order to check the reliability of its long-term predictions. Even though the calibration gave satisfactory results, the multi-annual trends of the output variables were found to be in contrast with the observed evolution of the seagrass biomasses. Since detailed information about the air temperature and solar radiation are often available, these findings suggest that the testing of the ecological consistency of the evolution of primary production models in the long term would provide additional confidence in their results, particularly in those cases in which the scarcity of field data does not allow one to perform a formal corroboration/validation of these models

The Global Stratotype Sections and Points for the bases of the Selandian (Middle Paleocene) and Thanetian (Upper Paleocene) stages at Zumaia, Spain

The global stratotype sections and points for the bases of the Selandian (Middle Paleocene) and Thanetian (Upper Paleocene) stages have been defined in the coastal cliff along the Itzurun Beach at the town of Zumaia in the Basque Country, northern Spain. In the hemipelagic section exposed at Zumaia the base of the Selandian Stage has been placed at the base of the Itzurun Formation, ca. 49 m above the Cretaceous/ Paleogene boundary. At the base of the Selandian, marls replace the succession of Danian red limestone and limestone-marl couplets. The best marine, global correlation criterion for the basal Selandian is the second radiation of the important calcareous nannofossil group, the fasciculiths. Species such as Fasciculithus ulii, F. billii, F. janii, F. involutus, F.pileatus and F. tympaniformis have their first appearance in the interval from a few decimetres below up to 1.1 m above the base of the Selandian. The marker species for nannofossil Zone NP5, F. tympaniformis, first occurs 1.1 m above the base. Excellent cyclostratigraphy and magnetostratigraphy in the section creates further correlation potential, with the base of the Selandian occuring 30 precession cycles (630 kyr) above the top of magnetochron C27n. Profound changes in sedimentology related to a major sea-level fall characterize the Danian-Selandian transition in sections along the margins of the North Atlantic. The base of the Thanetian Stage is placed in the same section ca. 78 m above the Cretaceous/Paleogene boundary. It is defined at a level 2.8 m or eight precession cycles above the base of the core of the distinct clay-rich interval associated with the Mid-Paleocene Biotic Event, and it corresponds to the base of magnetochron C26n in the section. The base of the Thanetian is not associated with any significant change in marine micro-fauna or flora. The calcareous nannofossil Zone NP6, marked by the first occurrence of Heliolithus kleinpelli starts ca. 6.5 m below the base of the Thanetian. The definitions of the global stratotype points for the bases of the Selandian and Thanetian stages are in good agreements with the definitions in the historical stratotype sections in Denmark and England, respectively