Bioerosive structures of sclerozoan foraminifera from the lower pliocene of southern Spain: a contribution to the palaeoecology of marine hard substrate communities

A palaeoecological study of sclerozoan foraminifera of the families Saccamminidae (aff. Sagenina), Lituolidae (Placopsilina), Cibicididae (Cibicides, Dyocibicides, Cibicidella) and Planorbulinidae (Planorbulina and Planorbulinella) that colonized epifaunal bivalves (ostreids and pectinids) during the early Pliocene in southern Spain has led to the recognition of two new boring ichnogenera: Camarichnus ichnogen. nov., with two ichnospecies, C. subrectangularis ichnosp. nov. and C. arcuatus ichnosp. nov., and Canalichnus ichnogen. nov., with one ichnospecies, C. tenuis ichnosp. nov. The first two ichnospecies were produced by adnate lituolids and cibicidids, the last by saccamminids. Their recognition is very important when quantifying populations of these organisms. Colonisation took place after death of the host bivalves, when they acted as very stable substrates whose topography probably controlled the initial settlement pattern of the foraminifera. The colonisation sequence started with the foraminifera (lituolids-saccamminids-cibicidids-planorbulinids) and was followed by vermetid gastropods, serpulids, spirorbids, cheilostome bryozoans and/or ostreids. Preferred orientations and over-growth relationships between cheilostome bryozoans and serpulids have been detected in this material.info:eu-repo/semantics/publishedVersio

Two stories outside Boltzmann-Gibbs statistics: Mori's q-phase transitions and glassy dynamics at the onset of chaos

First, we analyze trajectories inside the Feigenbaum attractor and obtain the atypical weak sensitivity to initial conditions and loss of information associated to their dynamics. We identify the Mori singularities in its Lyapunov spectrum with the appearance of a special value for the entropic index q of the Tsallis statistics. Secondly, the dynamics of iterates at the noise-perturbed transition to chaos is shown to exhibit the characteristic elements of the glass transition, e.g. two-step relaxation, aging, subdiffusion and arrest. The properties of the bifurcation gap induced by the noise are seen to be comparable to those of a supercooled liquid above a glass transition temperature.Comment: Proceedings of: 31st Workshop of the International School of Solid State Physics, Complexity, Metastability and Nonextensivity, Erice (Sicily) 20-26 July 2004 World Scientific in the special series of the E. Majorana conferences, in pres

Contribución al estudio de las facies de tránsito Mioceno-Plioceno en el sector noroccidental de la Cuenca del Guadalquivir (Valencina de la Concepción, Sevilla)

Se dan a conocer las principales características mineralógicas,  sedimentológicas e icnológicas de una secuencia rítmica lutítico-arenosa que define el tránsito Mioceno-Plioceno en el sector Noroccidental de la Cuenca del Guadalquivir (Valencina de la Concepción, Sevilla).Estos depósitos reflejan unas condiciones de sedimentación discontinua, alternante, lenta y rápida, posiblemente ligada a eventos de carácter energético alto  (tormentas) dentro de un medio de plataforma marina somera relativamente estable

Tsallis' q index and Mori's q phase transitions at edge of chaos

We uncover the basis for the validity of the Tsallis statistics at the onset of chaos in logistic maps. The dynamics within the critical attractor is found to consist of an infinite family of Mori's $q$-phase transitions of rapidly decreasing strength, each associated to a discontinuity in Feigenbaum's trajectory scaling function $\sigma$. The value of $q$ at each transition corresponds to the same special value for the entropic index $q$, such that the resultant sets of $q$-Lyapunov coefficients are equal to the Tsallis rates of entropy evolution.Comment: Significantly enlarged version, additional figures and references. To be published in Physical Review

Multifractality and nonextensivity at the edge of chaos of unimodal maps

We examine both the dynamical and the multifractal properties at the chaos threshold of logistic maps with general nonlinearity $z>1$. First we determine analytically the sensitivity to initial conditions $\xi_{t}$. Then we consider a renormalization group (RG) operation on the partition function $Z$ of the multifractal attractor that eliminates one half of the multifractal points each time it is applied. Invariance of $Z$ fixes a length-scale transformation factor $2^{-\eta}$ in terms of the generalized dimensions $D_{\beta}$. There exists a gap $\Delta \eta$ in the values of $\eta$ equal to $\lambda _{q}=1/(1-q)=D_{\infty}^{-1}-D_{-\infty}^{-1}$ where $\lambda_{q}$ is the $q$-generalized Lyapunov exponent and $q$ is the nonextensive entropic index. We provide an interpretation for this relationship - previously derived by Lyra and Tsallis - between dynamical and geometrical properties. Key Words: Edge of chaos, multifractal attractor, nonextensivityComment: Contribution to the proceedings of 2nd International Conference on News and Expectations in Thermostatistics (NEXT03), Cagliari, Italy, 21-28/09/2003. Submitted to Physica