La edad del primer pulso de rifting continental asociado a la ruptura de Pangea en el suroeste ibérico: nueva evidencia palinológica

ABSTRACT: In this work, we report the first palynological age for the base strata of the Silves Sandstones of the Silves Group in the Algarve Basin, located in Southern Portugal. The group is the oldest sedimentary unit of the Algarve Basin and was deposited unconformably over late Pennsylvanian turbidites of the Mira Formation, which were folded and faulted during the Variscan Orogeny. The Silves Group comprises a detrital red bed succession, representing the earliest phase of sedimentation associated with the initial rifting of Pangaea. Macrofossils are rare, occurring predominantly in the top layers of this group, and do not accurately constrain the age of the entire group's deposition. From an outcrop exposed in the central Algarve, a grey mudstone bed positioned 2.5 m above the Variscan unconformity plane yielded palynomorphs that date the beginning of sedimentation in this basin to the early Carnian age (Late Triassic). The moderately well preserved and low-diversity palynological association comprises Aulisporites astigmosus, Enzonalasporites densus, Ovalipollis pseudoalatus, Samaropollenites speciosus, Tulesporites briscoensis and Vallasporites ignacii, among others, and is indicative of an early Carnian age.RESUMEN: Mediante datos de asociaciones palinológicas, describimos por primera vez la edad de los niveles de la base de la Formación Areniscas de Silves, del Grupo Silves, en la cuenca del Algarve, sur de Portugal. Este grupo representa la unidad sedimen taria más antigua del Mesozoico de la Cuenca del Algarve, y fue depositada discordantemente sobre las areniscas de edad Pensilvaniense superior de la Formación Mira, un registro sedimentario que fue plegado y fallado durante la Orogenia Varisca. El Grupo Silves muestra unos sedimentos detríticos rojos que representan la fase más temprana de la sedimentación y que está asociada a las primeras fases de la ruptura de Pangea. Los macrofósiles son escasos, se encuentran en los niveles superiores del grupo y no proporcionan una edad determinada. Una asociación palinológica ha sido encontrada y descrita en un nivel de lutitas grises situado a 2,5 cm por encima de la discordancia varisca, y que proporcionan una edad Carniense (Triásico Superior) para el comienzo de la sedimentación de esta unidad. Se trata de una asociación moderadamente bien conservada y con baja diversidad de elementos, que contiene Aulisporites astigmosus, Enzonalasporites densus, Ovalipollis pseudoalatus, Samaropollenites speciosus, Tulesporites briscoensis y Vallaspollites ignacii entre otros, y es indicativa de un Carniense inferior.info:eu-repo/semantics/publishedVersio

A 2MASS Analysis of the Stability of Southern Bok Globules

We used near-infrared 2MASS data to construct visual extinction maps of a sample of Southern Bok globules utilizing the NICE method. We derived radial extinction profiles of dense cores identified in the globules and analyzed their stability against gravitational collapse with isothermal Bonnor-Ebert spheres. The frequency distribution of the stability parameter xi_max of these cores shows that a large number of them are located in stable states, followed by an abrupt decrease of cores in unstable states. This decrease is steeper for globules with associated IRAS point sources than for starless globules. Moreover, globules in stable states have a Bonnor-Ebert temperature of T = 15 +- 6 K, while the group of critical plus unstable globules has a different temperature of T = 10 +- 3 K. Distances were estimated to all the globules studied in this work and the spectral class of the IRAS sources was calculated. No variations were found in the stability parameters of the cores and the spectral class of their associated IRAS sources. On the basis of 13CO J = 1-0 molecular line observations, we identified and modeled a blue-assymetric line profile toward a globule of the sample, obtaining an upper limit infall speed of 0.25 km/s.Comment: 53 pages, 15 figures, accepted for publication in Ap

The Stellar Content of Obscured Galactic Giant HII Regions V: G333.1--0.4

We present high angular resolution near--infrared images of the obscured Galactic Giant HII (GHII) region G333.1--0.4 in which we detect an OB star cluster. For G333.1--0.4, we find OB stars and other massive objects in very early evolutionary stages, possibly still accreting. We obtained $K$--band spectra of three stars; two show O type photospheric features, while the third has no photospheric features but does show CO 2.3 $\mu$m band--head emission. This object is at least as hot as an early B type star based on its intrinsic luminosity and is surrounded by a circumstellar disc/envelope which produces near infrared excess emission. A number of other relatively bright cluster members also display excess emission in the $K$--band, indicative of disks/envelopes around young massive stars. Based upon the O star photometry and spectroscopy, the distance to the cluster is 2.6 $\pm$ 0.4 kpc, similar to a recently derived kinematic (near side) value. The slope of the $K$--band luminosity function is similar to those found in other young clusters. The mass function slope is more uncertain, and we find $-1.3 \pm 0.2 < \Gamma < -1.1 \pm 0.2$- for stars with M $> 5$ M$_\odot$ where the upper an lower limits are calculated independently for different assumptions regarding the excess emission of the individual massive stars. The number of Lyman continuum photons derived from the contribution of all massive stars in the cluster is 0.2 $\times$ $10^{50}$ $s^{-1}$ $< NLyc < 1.9$ $\times$ $10^{50}$ $s^{-1}$. The integrated cluster mass is 1.0 $\times$ $10^{3}$ $M_\odot < M_{cluster} < 1.3$ $\times$ $10^{3}$ $M_\odot$.Comment: 31 pages, including 12 figures and 3 tables. Accepted for publication in the A

Enteric methane emission of Nellore cattle in extensive grazing or integrated systems.

Brazilian beef cattle production is primarily based in grazing systems which in general present low productivity as a result of extensive monoculture pastures. Integrated systems come up as alternatives to overcome this scenario which in turn may have impacts on agricultural greenhouse gas emission. In 2015, we reported the first results on enteric methane (CH4) emissions comparing extensive and integrated systems (Gomes et al., 2015). However, it is important to observe how results behave over time, in order to draw robust conclusions. The aim was to evaluate the enteric methane emission of beef cattle grazing extensive pastures (EXT), integrated crop-livestock (ICL) and crop-livestock-forest systems (ICLF) in two seasons, over a two-year study