Late Turonian ammonites from Haute-Normandie, France

Upper Turonian chalks of Haute-Normandie yield a distinctive ammonite fauna within the Subprionocyclus neptuni ammonite Zone and the Plesiocorys (Sternotaxis) plana echinoid Zone. Well-localised material all comes from the phosphatic fauna of the Senneville 2 Hardground that marks the boundary between the Formation de Senneville and the Életot Member of the succeeding Formation de Saint-Pierre-en-Port. The association is dominated by Lewesiceras mantelli Wright and Wright, 1951, accompanied by Mesopuzosia mobergi (de Grossouvre, 1894), Lewesiceras woodiWright, 1979, Subprionocyclus hitchinensis (Billinghurst, 1927), Subprionocyclus branneri (Anderson, 1902), Subprionocyclus normalis (Anderson, 1958), Allocrioceras nodiger (F. Roemer, 1870), Allocrioceras billinghursti Klinger, 1976, Hyphantoceras reussianum (d’Orbigny, 1850), Sciponoceras bohemicum bohemicum (Fritsch, 1872), and Scaphites geinitzii d’Orbigny, 1850. The fauna represents the Hyphantoceras reussianum Event of authors, elements of which have been recognised on the north side of Tethys from Northern Ireland to the Mangyschlak Mountains of western Kazakstan, a distance of more than 3,500 kilometres

Trans-Tethyan correlation of the Lower–Middle Cenomanian boundary interval; southern England (Southerham, near Lewes, Sussex) and Douar el Khiana, northeastern Algeria

A 480 m section of marls with widely separated levels of nodular limestone in the Fahdene Formation north of Bou Khadra in Tebessa Province, northeastern Algeria, spans the Lower/Middle Cenomanian boundary. A total of 30 ammonite species are present, of which two: Forbesiceras reversum and Calycoceras (Newboldiceras) algeriense are new. The fauna allows recognition of the Northwest European upper Lower Cenomanian Mantelliceras dixoni Zone, the succeeding lower Middle Cenomanian Cunningtoniceras inerme Zone, the Acanthoceras rhotomagense Zone and its subzones of Turrilites costatus and Turrilites acutus. The sequence of index species occurs in the same order in both north-eastern Tunisia and the Southerham Grey Pit in Sussex (and indeed elsewhere in North-west Europe), indicating these to be robust assemblage zones and subzones that can be recognised on both the north and south sides of the Tethys. Other occurrences of taxa that are common in both sections and regions are markedly different, and include the co-occurrence of Cunningtoniceras inerme (Pervinquière, 1907) with Acanthoceras rhotomagense (Brongniart, 1822) in the costatus Subzone in north-eastern Algeria and central Tunisia, the extension of Acompsoceras renevieri (Sharpe, 1857) into the lower Middle Cenomanian in north-eastern Tunisia, whilst the acme of Turrilites scheuchzerianus Bosc, 1801, is in the dixoni Zone in Northwest Europe, and in the inerme Zone in northeasten Algeria and adjacent parts of Central Tunisia. These differences are not a result of collection failure or non-preservation, but must rather reflect environmental controls on occurrence and abundance

Agglutinated foraminifera from the Turonian–Coniacian boundary interval in Europe – paleoenvironmental remarks and stratigraphy

Agglutinated foraminiferal assemblages of the Turonian–Coniacian from the GSSP (Global Boundary Stratotype Section and Point) of Salzgitter–Salder (Subhercynian Cretaceous Basin, Germany) and other sections, including Bielefeld–Ostwestfalendamm (Münsterland Cretaceous Basin, Germany) and the Dover–Langdon Stairs (Anglo-Paris Basin, England), from the temperate European shelf realm were studied in order to collect additional stratigraphic and paleoenvironmental information. Stable carbon isotopes were measured for the Bielefeld–Ostwestfalendamm section to establish a reliable stratigraphic correlation with other sections. Highly diverse agglutinated foraminiferal assemblages were obtained from sections in the German basins, whereas the fauna from Dover is less rich in taxa and less abundant. In the German basinal sections, a morphogroup analysis of agglutinated foraminifera and the calculated diversities imply normal marine settings and oligotrophic to mesotrophic bottom-water conditions. Furthermore, acmes of agglutinated foraminifera correlate between different sections and can be used for paleoenvironmental analysis. Three acmes of the species Ammolagena contorta are recorded for the Turonian–Coniacian (perplexus to lower striatoconcentricus zones, lower scupini Zone, and hannovrensis Zone) and likely imply a shift to more oligotrophic bottom-water conditions. In the upper scupini Zone below the Turonian–Coniacian boundary, an acme of Bulbobaculites problematicus likely indicates enhanced nutrient availability. In general, agglutinated foraminiferal morphogroups display a gradual shift from Turonian oligotrophic environments towards more mesotrophic conditions in the latest Turonian and Coniacian

Evolving spiking networks with variable resistive memories

Neuromorphic computing is a brainlike information processing paradigm that requires adaptive learning mechanisms. A spiking neuro-evolutionary system is used for this purpose; plastic resistive memories are implemented as synapses in spiking neural networks. The evolutionary design process exploits parameter self-adaptation and allows the topology and synaptic weights to be evolved for each network in an autonomous manner. Variable resistive memories are the focus of this research; each synapse has its own conductance profile which modifies the plastic behaviour of the device and may be altered during evolution. These variable resistive networks are evaluated on a noisy robotic dynamic-reward scenario against two static resistive memories and a system containing standard connections only. The results indicate that the extra behavioural degrees of freedom available to the networks incorporating variable resistive memories enable them to outperform the comparative synapse types. © 2014 by the Massachusetts Institute of Technology

Midlatitude shelf seas in the Cenomanian-Turonian greenhouse world: Temperature evolution and North Atlantic circulation

An 8 million year record of subtropical and midlatitude shelf-sea temperatures, derived from oxygen isotopes of well-preserved brachiopods from a variety of European sections, demonstrates a long-term Cenomanian temperature rise (16–20°C, midlatitudes) that reached its maximum early in the late Turonian (23°C, midlatitudes). Superimposed on the long-term trend, shelf-sea temperatures vary at shorter timescales in relation to global carbon cycle perturbations. In the mid-Cenomanian and the late Turonian, two minor shelf-sea cooling events (2–3°C) coincide with carbon cycle perturbations and times of high-amplitude sea level falls. Although this evidence supports the hypothesis of potential glacioeustatic effects on Cretaceous sea level, the occurrence of minimum shelf-sea temperatures within transgressive beds argues for regional changes in shelf-sea circulation as the most plausible mechanism. The major carbon cycle event in the latest Cenomanian (oceanic anoxic event 2) is accompanied by a substantial increase in shelf-sea temperatures (4–5°C) that occurred ∼150 kyr after the commencement of the δ13C excursion and is related to the spread of oceanic conditions in western European shelf-sea basins. Our oxygen isotope record and published δ18O data of pristinely preserved foraminifera allow the consideration of North Atlantic surface water properties in the Cenomanian along a transect from the tropics to the midlatitudes. On the basis of fossil-derived δ18O, estimated δw ranges, and modeled salinities, temperature-salinity-density ranges were estimated for tropical, subtropical, and midlatitude surface waters. Accordingly, the Cenomanian temperate shelf-seas waters have potentially the highest surface water density and could have contributed to North Atlantic intermediate to deep waters in the preopening stage of the equatorial Atlantic gateway

Discrete integrable systems and Poisson algebras from cluster maps

We consider nonlinear recurrences generated from cluster mutations applied to quivers that have the property of being cluster mutation-periodic with period 1. Such quivers were completely classified by Fordy and Marsh, who characterised them in terms of the skew-symmetric matrix that defines the quiver. The associated nonlinear recurrences are equivalent to birational maps, and we explain how these maps can be endowed with an invariant Poisson bracket and/or presymplectic structure. Upon applying the algebraic entropy test, we are led to a series of conjectures which imply that the entropy of the cluster maps can be determined from their tropical analogues, which leads to a sharp classification result. Only four special families of these maps should have zero entropy. These families are examined in detail, with many explicit examples given, and we show how they lead to discrete dynamics that is integrable in the Liouville-Arnold sense.Comment: 49 pages, 3 figures. Reduced to satisfy journal page restrictions. Sections 2.4, 4.5, 6.3, 7 and 8 removed. All other results remain, with minor editin