A new Late Jurassic assemblage of “conchostracans”, ostracods, bivalves and caddisfly cases from the locality “Estancia La Sin Rumbo”, Chubut Province (Patagonia, Argentina) is recorded. The fossils occur in the upper part of an outcropping 45 m thick volcaniclastic lacustrine sequence of yellowish tuffs and tuffites of the Puesto Almada Member, which is the upper member of the Cañadón Asfalto Formation with U/Pb age of 161 ± 3 Ma. The sequence represents one sedimentary cycle composed of a (lower) hemicycle of expansion and a (higher) hemicycle of contraction of the water body. The invertebrates lived in small freshwater bodies during the periods of expansion of the lake. The occurrence of a great number of small spinicaudatans, associated with mud-cracks, is evidence of dry climatic conditions and suggests several local mortality events. The spinicaudatan record of the fushunograptid–orthestheriid (component of the Eosestheriopsis dianzhongensis fauna) and the presence of Congestheriella rauhuti Gallego and Shen, suggest a Late Jurassic (Oxfordian to Tithonian) age. Caddisfly cases are recorded for the first time in the Cañadón Asfalto Basin. 相似文献
Underground hard coal mining usually disrupts the mechanical equilibrium of rock sequences, creating fractures within minor permeable rocks. The present study employs a dual-continuum model to assess how both fractured and porous sandstone media influence the percolation process in postmining setups. To test the approach, the software TOUGH2 was employed to simulate laminar fluid flow in the unsaturated zone of the Ibbenbüren Westfield mining area. Compared to other coal mining districts in Germany, this area is delineated by the topography and local geology, leading to a well-defined hydrogeological framework. Results reveal good agreement between the calculated and measured mine water discharge for the years 2008 and 2017. The constructed model was capable of reproducing the bimodal flow behavior of the adit by coupling a permeable fractured continuum with a low-conductivity rock matrix. While flow from the fractured continuum results in intense discharge events during winter months, the rock matrix determines a smooth discharge limb in summer. The study also evaluates the influence of individual and combined model parameters affecting the simulated curve. A detailed sensitivity analysis displayed the absolute and relative permeability function parameters of both continua among the most susceptible variables. However, a strong a priori knowledge of the value ranges for the matrix continuum helps to reduce the model ambiguity. This allowed for calibration of some of the fractured medium parameters for which sparse or variable data were available. However, the inclusion of the transport component and acquisition of more site-specific data is recommended to reduce their uncertainty.
Elastic behavior and pressure-induced structural evolution of synthetic boron-mullite “Al5BO9” (a = 5.678(2) Å, b = 15.015(4) Å and c = 7.700(3) Å, space group Cmc21, Z = 4) were investigated up to 7.4 GPa by in situ single-crystal X-ray diffraction with a diamond anvil cell under hydrostatic conditions. No phase transition or anomalous compressional behavior occurred within the investigated P range. Fitting the P–V data with a truncated second-order (in energy) Birch-Murnaghan Equation-of-State (BM-EoS), using the data weighted by the uncertainties in P and V, we obtained: V0 = 656.4(3) Å3 and KT0 = 165(7) GPa (βV0 = 0.0061(3) GPa?1). The evolution of the Eulerian finite strain versus normalized stress (fE–FE plot) leads to an almost horizontal trend, showing that a truncated second-order BM-EoS is appropriate to describe the elastic behavior of “Al5BO9” within the investigated P range. The weighted linear regression through the data points gives: FE(0) = 159(11) GPa. Axial compressibility coefficients yielded: βa = 1.4(2) × 10?3 GPa?1, βb = 3.4(4) × 10?3 GPa?1, and βc = 1.7(3) × 10?3 GPa?1 (βa:βb:βc = 1:2.43:1.21). The highest compressibilities observed in this study within (100) can be ascribed to the presence of voids represented by five-membered rings of polyhedra: Al1–Al3–Al4–Al1–Al3, which allow accommodating the effect of pressure by polyhedral tilting. Polyhedral tilting around the voids also explains the higher compressibility along [010] than along [001]. The stiffer crystallographic direction observed here might be controlled by the infinite chains of edge-sharing octahedra running along [100], which act as “pillars”, making the structure less compressible along the a-axis than along the b- and c-axis. Along [100], compression can only be accommodated by deformation of the edge-sharing octahedra (and/or by compression of the Al–O bond lengths), as no polyhedral tilting can occur. In addition, a comparative elastic analysis among the mullite-type materials is carried out. 相似文献
Terebratuloid and cancellothyridoid brachiopods from the South-Helvetic Lutetian (Eocene) of the Fäneren region (NE Switzerland) are described: Carneithyris subregularis (Quenstedt) and two forms of Terebratulina s.l. under open nomenclature. Several species of Alpine and non-Alpine origin, related to Carneithyris subregularis, like Terebratula kickxi Galeotti, Terebratula aequivalvis Schafhäutl and Terebratula hilarionis Davidson show characters, which compare well with Carneithyris subregularis. Two of them, T. aequivalvis and T. hilarionis, are assigned to the genus Carneithyris. The stratigraphy and lithology of the sediments in the study area are reassessed. Life habits and palaeoecology of the brachiopods are discussed. C. subregularis apparently was a free living brachiopod without attachment to the substrate, as indicated by massive accumulations of callosities in the posterior parts of the shell. The variability of the cardinal process, as seen in the studied Carneithyris group can be interpreted as a morphological element to enlarge the surface of attachment of strong diductor muscles in relation to the internal thickening of the individual. 相似文献
We study collective wind configurations produced by a number of massive stars, and obtain densities and expansion velocities
of the stellar wind gas that is to be target, in this model, of hadronic interactions. We study the expected γ-ray emission from these regions, considering in an approximate way the effect of cosmic ray modulation. We compute secondary
particle production (electrons from knock-on interactions and electrons and positrons from charged pion decay), and solve
the loss equation with ionization, synchrotron, bremsstrahlung, inverse Compton, and expansion losses. We provide examples
where configurations can produce sources for GLAST satellite, and the MAGIC, HESS, or VERITAS telescopes in non-uniform ways,
i.e., with or without the corresponding counterparts. We show that in all cases we studied no EGRET source is expected. 相似文献
The Meseta Chile Chico (MCC, 46.4°S) is the westernmost exposure of Eocene (lower basaltic sequence, LBS; 55–40 Ma, K–Ar ages) and Mio–Pliocene (upper basaltic sequence, UBS; 16–4 Ma, K–Ar ages) flood basalt volcanism in Patagonia. The MCC is located south of the Lago General Carrera-Buenos Aires (LGCBA), southeast from the present day Chile Triple Junction (CTJ), east of the actual volcanic gap between Southern South Volcanic Zone and Austral Volcanic Zone (SSVZ and AVZ, respectively) and just above the inferred location of the South Chile Ridge segment subducted at 6 Ma (SCR-1). Erupted products consist of mainly ne-normative olivine basalt with minor hy-normative tholeiites basalt, trachybasalt and basanite. MCC lavas are alkaline (42.7–53.1 wt.% SiO2, 3–8 wt.% Na2O+K2O) and relatively primitive (Ni: 133–360 ppm, Cr: 161–193 ppm, Co: 35–72 ppm, 4–16.5 MgO wt.%). They have a marked OIB-like signature, as shown by their isotopic compositions (87Sr/86Sro=0.70311–0.70414 and εNd=+4.7–+5.1) and their incompatible trace elements ratios (Ba/La=10–20, La/Nb=0.46–1.09, Ce/Pb=15.52–27.5, Sr/La<25), reflecting deep mantle origin. UBS-primitive lavas have characteristics similar to those of the Eocene LBS basalts, while UBS-intermediate lavas show geochemical imprints (La/Nb>1, Sr/La>25, low Ce/Pb, Nb/U) compatible with contamination by arc/slab-derived and/or crustal components. We propose that the genesis and extrusion of magmas is related to the opening of two slab windows due to the subduction of two active ridge segments beneath Patagonia during Eocene and Mio–Pliocene. 相似文献
This is an exploratory study on the high-pressure (HP) structural evolution of a zeolitic framework (with LEV topology) on the basis of geometric modelling and previously published accurate unit-cell constants measured by means of single-crystal X-ray diffraction. The geometric simulations for 11 P values from 0 to 5 GPa gives more insight into the HP-behaviour of levyne, showing that the anomalous elastic behaviour of this zeolite observed under hydrostatic conditions at low P (P<1 GPa) is due to a double change in the compressional mechanism. Since the geometric simulation is not restricted to using the experimentally determined cell parameters, simulations of uniaxial compression along the [001] direction and of compression in the (001) plane have been performed, shedding more light on the compression mechanisms under non-hydrostatic regimes, which are difficult to access experimentally. The mechanisms associated with compressions along different axes provide insight into the hydrostatic compression mechanisms leading to the anomalous elastic behaviour.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献