3-D crustal structure of the extensional Granada Basin in the convergent boundary between the Eurasian and African plates

Three-dimensional P and S wave velocity models of the crust under the Granada Basin in Southern Spain are obtained with a spatial resolution of 5 km in the horizontal direction and 2 to 4 km in depth. We used a total of 15407 P and 13704 S wave high-quality arrival times from 2889 local earthquakes recorded by both permanent seismic networks and portable stations deployed in the area. The computed P and S wave velocities were used to obtain three-dimensional distributions of Poisson's ratio (σ) and the porosity parameter (V_p×V_s). The 3-D velocity images show strong lateral heterogeneities in the region. Significant velocity variations up to ±7% in P and S velocities are revealed in the crust below the Granada Basin. At shallow depth, high-velocity anomalies are generally associated with Mesozoic basement, while the low-velocity anomalies are related to the neogene sedimentary rocks. The south–southeastern part of the Granada Basin exhibits high σ values in the shallowest layers, which may be associated with saturated and unconsolidated sediments. In the same area, V_p×V_s is high outside the basin, indicating low porosity of the mesozoic basement. A low-velocity zone at 18-km depth is found and interpreted as a weak–ductile crust transition that is related to the cut-off depth of the seismic activity. In the lower crust, at 34-km depth, a clear slow V_p and V_s anomalous zone may indicate variations in lithology and/or with the rigidity of the lower crust rocks.     

Pattern of sedimentary infilling of fossil mammal traps formed in pseudokarst at Cerro de los Batallones,Madrid Basin,central Spain

Fossil mammal sites of late Miocene age (ca 9 Ma) occur in hourglass‐shaped, non‐interconnected cavities up to 15 m deep, hosted in mudstone (mostly sepiolite), chert and carbonate bedrock in Cerro de los Batallones. This paper provides a model for the sedimentary infilling of the cavities, which functioned as traps for vertebrate faunas and contain one of the richest and best preserved Neogene mammal assemblages of the Iberian Peninsula. Generation of the mammal‐bearing cavities started with the solution of underlying evaporites, which resulted in fissures that were subsequently enlarged by subsurface piping, a process rarely preserved in the ancient sedimentary record. The system of subterranean cavities evolved into a pseudokarst landscape, resulting in doline‐like shafts reaching the ancient land surface. The sedimentary infilling of the cavities comprises both clastic and carbonate lithofacies that were investigated by outcrop observation, standard and scanning electron microscope petrography, mineralogical analysis, and stable isotope geochemistry. Gravel and breccia talus deposits, clast and mud‐supported gravel, pebbly sandstone and mudstone are common detrital infill deposits mostly derived by overflow erosion of bedrock. The deposits containing the mammal bones are marls, and occur both in subsurface cavities and doline‐like depressions. In the underground cavities, marlstone was mainly of clastic origin and accumulated in ponds scattered over the floor of the cavity. In contrast, marlstone deposits in the surface dolines formed mostly as a result of biochemical carbonate deposition in small shallow lakes subjected to fluctuation of the water level. The δ¹⁸O and δ¹³C carbonate values indicate different origins for the two kinds of marls. During the final phases of pipe infill the doline marlstone sealed the mammal sites, usually off‐lapping the adjacent bedrock.     

The influence of the environmental status of Casa Caiada and Rio Doce beaches (NE-Brazil) on beaches users

This paper describes the environmental status and the social perception of Casa Caiada (bay 1) and Rio Doce (bay 2 and bay 3) as a consequence of the several impacts that these beaches have been suffering. The methodology adopted in this work was based on interviews with beach users and direct observations of the physical, biological and human aspects. The obtained result denotes that in Casa Caiada the better beach quality is a consequence of the better water quality, infrastructure and services permitting a higher investment in housing development, recreation, commercialization, fishing, tourism, amongst others. In contrast, northward of Rio Doce (bay 3), the beach has been considered of bad quality for the beach users. In Casa Caiada the users were the most demanding when describing the status of the beach and the necessary changes to mitigate the actual situation. On the other hand, in the most degradated area (bay 3) the users were less demanding when proposing possible changes to improve the beach/water and life quality.     

Estimating the Density and Compressibility of Seawater to High Temperatures Using the Pitzer Equations

The density and compressibility of seawater solutions from 0 to 95 °C have been examined using the Pitzer equations. The apparent molal volumes (X = V) and compressibilities (X = κ) are in the form $$ X_{\phi } = \bar{X}^{0} + A_{X} I/(1.2 \, m)\ln (1 + 1.2 \, I^{0.5} ) + \, 2{\text{RT }}m \, (\beta^{(0)X} + \beta^{(1)X} g(y) + C^{X} m) $$ where $ \bar{X}^{0} $ is the partial molal volume or compressibility, I is the ionic strength, m is the molality of sea salt, A_X is the Debye–Hückel slope for volume (X = V) or adiabatic compressibility (X = κ _s), and g(y) = (2/y ²)[1 ? (1 + y) exp(?y)] where y = 2I ^0.5. The values of the partial molal volume and compressibility ( $ \bar{X}^{0} $ ) and Pitzer parameters (β ^(0)X , β ^(1)X and C ^X ) are functions of temperature in the form $$ Y^{X} = \sum_{i} a_{i} (T-T_{\text{R}} )^{i} $$ where a _i are adjustable parameters, T is the absolute temperature in Kelvin, and T _R = 298.15 K is the reference temperature. The standard errors of the seawater fits for the specific volumes and adiabatic compressibilities are 5.35E?06 cm³ g^?1 and 1.0E?09 bar^?1, respectively. These equations can be combined with similar equations for the osmotic coefficient, enthalpy and heat capacity to define the thermodynamic properties of sea salt to high temperatures at one atm. The Pitzer equations for the major components of seawater have been used to estimate the density and compressibility of seawater to 95 °C. The results are in reasonable agreement with the measured values (0.010E?03 g cm^?3 for density and 0.050E?06 bar^?1 for compressibility) from 0 to 80 °C and salinities from 0 to 45 g kg^?1. The results make it possible to estimate the density and compressibility of all natural waters of known composition over a wide range of temperature and salinity.     

Rock‐Magnetic and Archaeointensity Investigation of Pottery and a Burned Floor at the Tzintzuntzan Archaeological Site,Western Mexico

We report a detailed rock‐magnetic and archaeointensity analysis of four pottery fragments and a burned floor recovered from the Tzintzuntzan archaeological site in western Mexico. Results from rock‐magnetic experiments (x‐T curves and first‐order reversal curves [FORC] diagrams) indicate the suitability of most of these materials as faithful geomagnetic field recorders. Potsherds were archaeomagnetically dated by comparing their mean intensity values against the paleosecular variation curve CALS3k, suggesting A.D. 600–941 as the most probable age range. This is younger than ¹⁴C‐dated charcoal from the same burned floor (A.D. 1294–1426). More precise age estimates will require the use of the full geomagnetic vector (declination, inclination, and intensity). Multiple reheatings of the ceramic pieces, evidenced as secondary components in Zijderveld plots, could reflect multiple heating of these objects, perhaps from use as incense burners. Our study demonstrates the potential of archaeomagnetic analysis to both date burned ceramics recovered in situ and provide insight into their use‐history.     

Coastal Impacts of the March 11th Tohoku, Japan Tsunami in the Galapagos Islands

On March 11, 2011 at 5:46:23 UTC (March 10 11:46:23 PM Galapagos Local Time), the M_w 9.0 Great East Japan Earthquake occurred near the Tohoku region off the east coast of Japan, spawning a Pacific-wide tsunami. Approximately 12,000 km away, the Galapagos Islands experienced moderate tsunami impacts, including flooding, structural damage, and strong currents. In this paper, we present observations and measurements of the tsunami effects in the Galapagos, focusing on the four largest islands in the archipelago; (from west to east) Isabela, Santiagio, Santa Cruz, and San Cristobal. Access to the tsunami affected areas was one of the largest challenges of the field survey. Aside from approximately ten sandy beaches open to tourists, all other shoreline locations are restricted to anyone without a research permit; open cooperation with the Galapagos National Park provided the survey team complete access to the Islands coastlines. Survey locations were guided by numerical simulations of the tsunami performed prior to the field work. This numerical guidance accurately predicted the regions of highest impact, as well as regions of relatively low impact. Tide-corrected maximum tsunami heights were generally in the range of 3–4 m with the highest runup of 6 m measured in a small pocket beach on Isla Isabela. Puerto Ayora, on Santa Cruz Island, the largest harbor in the Galapagos experienced significant flooding and damage to structures located at the shoreline. A current meter moored inside the harbor recorded relatively weak tsunami currents of less than 0.3 m/s (0.6 knot) during the event. Comparisons with detailed numerical simulations suggest that these low current speed observations are most likely the result of data averaging at 20-min intervals and that maximum instantaneous current speeds were considerably larger. Currents in the Canal de Itabaca, a natural waterway between Santa Cruz Island and a smaller island offshore, were strong enough to displace multiple 5.5-ton navigation buoys. Numerical simulations indicate that currents in the Canal de Itabaca exceeded 4 m/s (~8 knots), a very large flow speed for a navigational waterway.     

Rock-magnetic and paleomagnetic results from the Tepic-Zacoalco rift region (western Mexico)

A rock-magnetic and paleomagnetic investigation was carried out on eleven Pleistocene and Pliocene ⁴⁰Ar/³⁹Ar dated lava flows from the Tepic-Zacoalco rift region in the western sector of the Trans-Mexican Volcanic Belt (TMVB) with the aim of obtaining new paleomagnetic data from the study region and information about the Earth’s magnetic field recorded in these rocks. Rock-magnetic experiments including measurement of thermomagnetic curves, hysteresis parameters and isothermal remanence acquisition curves were carried out to find out the carriers of remanent magnetisation and to determine their domain structure. Although some samples were characterised by the presence of a single ferromagnetic phase (magnetite), in most cases more phases were observed. Analysis of hysteresis parameters showed a mixture of single domain and multidomain particles, the fraction of the latter varying between 40% and 80%. Paleomagnetic results were obtained in all sites, although in 7 sites characteristic remanence directions and remagnetisation circles had to be combined in order to calculate site means. The six Pliocene sites not showing intermediate polarity yielded a paleomagnetic pole (latitude ? = 81.1°, longitude λ = 94.3°) which roughly agrees with the expected one. Paleomagnetic directions do not indicate significant vertical-axis block rotations in the western TMVB area. Reversed polarities observed can be correlated to the Gilbert chron, normal polarities to the Gauss chron or the Brunhes chron and intermediate polarities to the Cochiti-Gilbert or the Gilbert-Gauss transition. The reversed or intermediate polarity magnetisation recorded in one of the sites (542 ± 24 ka) corresponds either to the West Eifel 4 or the West Eifel 5 excursion, while the reversed polarity observed in the other site (220 ± 36 ka) very likely provides new evidence for the Pringle Falls excursion or the event recorded in the Mamaku ignimbrite.     

EURD Data Provide Strong Evidence Against the Sciama Model of Radiative Decay of Massive Neutrinos

Data obtained with a high resolution, high sensitivity spectrometer flown on the Spanish MINISAT 01 satellite wereused to test the Sciama model of radiatively decaying massive neutrinos. The observed emission is far less intense than that expected in the Sciama model.     

An improved algorithm to compute circular functions of Poisson series

The efficiency in the computation of circular functions, such as cos(u) or sin(u), where u is a Poisson series, is important to derive accurate solutions of many problems of Celestial Mechanics, for instance, the orbital or rotational perturbed motion of natural or artificial bodies, since expansions in terms of Legendre functions and multiple Fourier series appear almost everywhere. Therefore, it is worth searching for alternative algorithms with lower computational cost. In this article, we propose a method based on the idea of elimination, which was originally applied to solve numerical problems, mainly in the case of matrix functions. Our comparisons with the traditional Taylor expansion prove that this new method can be more efficient when applied to compute the sine and cosine of a Poisson series.     

EURD: The Mission and the Stellar Absolute Fluxes of B-Type Stars

We present here stellar spectra of B stars obtained with the EURD spectrograph, one of the three instruments on board MINISAT-01. EURD is a spectrograph specially designed to detect diffuse radiation in thewavelength range between 350 and 1100 Å with 5 Å spectral resolution. EURD main scientific targets are: the spectrum of interstellar medium,atmospheric airglow, decaying neutrinos, Moon and early type stars.