Stratigraphic record and palaeogeographical context of the Neogene basins in the Betic Cordillera, Spain

The Betic Cordillera (Southern Spain) acquired its present configuration during the Neogene. The formation, evolution and total or partial destruction of Neogene sedimentary basins were highly controlled by the geodynamic situations and the positions of the basins in the Betic Cordillera. It is impossible to reconstruct the geometry of basins formed during the Early and Middle Miocene, concurrently with the westward drift of the Internal Zones, because in many cases only small outcrops remain. The basins formed on the mobile substratum (the Internal Zones) are characterized by a sedimentary infill made up of synorogenic deposits, which were intensely deformed towards the end of the Middle Miocene, and which were heavily eroded before the beginning of the Late Miocene. In the External Zones, deposition mainly took place in the North Betic Strait, an area across which there was wide communication between the Atlantic and the Mediterranean, which received huge olistostromic masses in its more mobile sector (the foredeep basin), and which evolved differently in its eastern and western sectors. The palaeogeography of the Cordillera changed radically at the beginning of the Late Miocene, when the westward drift of the Internal Zones ceased. During this time the North Betic Strait disappeared and, in what had been its northwestern half approximately, the Guadalquivir Basin became individualized. This basin, which was located between the Betic Chain and the emerged Hercynian Massif, acquired a structure similar to that of the present basin and its extension was also similar to that of the present Neogene outcrops. Intramontane basins became individualized in the recently formed and progressively emerged mountain chain, reaching a development and size in this Cordillera much greater than in other Alpine chains. These basins are characterized by their thick infills, which are unconformable on the folded and deformed substratum, and which can be subdivided according to the different movements of the fault sets that controlled their evolution.     

Onshore Neogene stratigraphy in the North of the Alboran Sea (Betic Internal Zones): Paleogeographic implications

The Neogene is the period in which the Betic Cordillera, the Rif, and the Alboran Sea acquired their present configuration. The Neogene sediments of the Betic Internal Zones (located directly to the North of the Alboran Sea) show the effects of important periods of deformation. Deposition was clearly controlled by tectonics. Therefore the generation, evolution, and total or partial destruction of basins and the formation of new, often superimposed, basins are common phenomena, according to the locations of the basins in the Betic Cordillera and to the different geodynamic situations.     

Keck observations of the 2002-2003 jovian ring plane crossing

We present new observations of Jupiter's ring system at a wavelength of 2.2 μm obtained with the 10-m W.M. Keck telescopes on three nights during a ring plane crossing: UT 19 December 2002, and 22 and 26 January 2003. We used conventional imaging, plus adaptive optics on the last night. Here we present detailed radial profiles of the main ring, halo and gossamer rings, and interpret the data together with information extracted from radio observations of Jupiter's synchrotron radiation. The main ring is confined to a 800-km-wide annulus between 128,200 and 129,000 km, with a ∼5000 km extension on the inside. The normal optical depth is 8×¹⁰⁻⁶, 15% of which is provided by bodies with radii a?5 cm. These bodies are as red as Metis. Half the optical depth, τ≈4×¹⁰⁻⁶, is attributed to micron-sized dust, and the remaining τ≈3×¹⁰⁻⁶ to grains tens to hundreds of μm in size. The inward extension consists of micron-sized (a?10 μm) dust, which probably migrates inward under Poynting-Robertson drag. The inner limit of this extension falls near the 3:2 Lorentz resonance (at orbital radius r=122,400 km), and coincides with the outer limit of the halo. The gossamer rings appear to be radially confined, rather than broad sheets of material. The Amalthea ring is triangularly shaped, with a steep outer dropoff over ∼5000 km, extending a few 1000 km beyond the orbit of Amalthea, and a more gradual inner dropoff over 15,000-20,000 km. The inner edge is near the location of the synchronous orbit. The optical depth in the Amalthea ring is ∼5×¹⁰⁻⁷, up to 20% of which is comprised of macroscopic material. The optical depth in the Thebe ring is a factor of 3 smaller.     

EVA: GPS-based extended velocity and acceleration determination

In this work, a new GPS carrier phase-based velocity and acceleration determination method is presented that extends the effective range of previous techniques. The method is named ‘EVA’, and may find applications in fields such as airborne gravimetry when rough terrain or water bodies make difficult or impractical to set up nearby GPS reference receivers. The EVA method is similar to methods such as Kennedy (Precise acceleration determination from carrier phase measurements. In: Proceedings of the 15th international technical meeting of the satellite division of the Institute of Navigation. ION GPS 2002, Portland pp 962–972, 2002b) since it uses L1 carrier phase observables for velocity and acceleration determination. However, it introduces a wide network of stations and it is independent of precise clock information because it estimates satellite clock drifts and drift rates ‘on-the-fly’, requiring only orbit data of sufficient quality. Moreover, with EVA the solution rate is only limited by data rate, and not by the available precise satellite clocks data rate. The results obtained are more robust for long baselines than the results obtained with the reference Kennedy method. An advantage of being independent of precise clock information is that, beside IGS Final products, also the Rapid, Ultra-Rapid (observed) and Ultra-Rapid (predicted) products may be used. Moreover, the EVA technique may also use the undifferenced ionosphere-free carrier phase combination (LC), overcoming baseline limitations in cases where ionosphere gradients may be an issue and very low biases are required. During the development of this work, some problems were found in the velocity estimation process of the Kennedy method. The sources of the problems were identified, and an improved version of the Kennedy method was used for this research work. An experiment was performed using a light aircraft flying over the Pyrenees, showing that both EVA and the improved Kennedy methods are able to cope with the dynamics of mountainous flight. A RTK-derived solution was also generated, and when comparing the three methods to a known zero-velocity reference the results yielded similar performance. The EVA and the improved-Kennedy methods outperformed the RTK solutions, and the EVA method provided the best results in this experiment. Finally, both the improved version of the Kennedy method and the EVA method were applied to a network in equatorial South America with baselines of more than 1,770 km, and during local noon. Under this tough scenario, the EVA method showed a clear advantage for all components of velocity and acceleration, yielding better and more robust results.     

Methodology for the combination of sub-daily Earth rotation from GPS and VLBI observations

A combination procedure of Earth orientation parameters from Global Positioning System (GPS) and Very Long Baseline Interferometry (VLBI) observations was developed on the basis of homogeneous normal equation systems. The emphasis and purpose of the combination was the determination of sub-daily polar motion (PM) and universal time (UT1) for a long time-span of 13 years. Time series with an hourly resolution and a model for tidal variations of PM and UT1-TAI (dUT1) were estimated. In both cases, 14-day nutation corrections were estimated simultaneously with the ERPs. Due to the combination procedure, it was warranted that the strengths of both techniques were preserved. At the same time, only a minimum of de-correlating or stabilizing constraints were necessary. Hereby, a PM time series was determined, whose precision is mainly dominated by GPS observations. However, this setup benefits from the fact that VLBI delivered nutation and dUT1 estimates at the same time. An even bigger enhancement can be seen for the dUT1 estimation, where the high-frequency variations are provided by GPS, while the long term trend is defined by VLBI. The estimated combined tidal PM and dUT1 model was predominantly determined from the GPS observations. Overall, the combined tidal model for the first time completely comprises the geometrical benefits of VLBI and GPS observations. In terms of root mean squared (RMS) differences, the tidal amplitudes agree with other empirical single-technique tidal models below 4 μas in PM and 0.25 μs in dUT1. The noise floor of the tidal ERP model was investigated in three ways resulting in about 1 μas for diurnal PM and 0.07 μs for diurnal dUT1 while the semi-diurnal components have a slightly better accuracy.     

Ground-based near infrared spectroscopy of Jupiter's ring and moons

The backscattered reflectivity of Jupiter's ring has been previously measured over distinct visible and near infrared wavelength bands by a number of ground-based and spaceborne instruments. We present spectra of Jupiter's main ring from 2.21-2.46 μm taken with the NIRSPEC spectrometer at the W.M. Keck observatory. At these wavelengths, scattered light from Jupiter is minimal due to the strong absorption of methane in the planet's atmosphere. We find an overall flat spectral slope over this wavelength interval, except for a possible red slope shortward of 2.25 μm. We extended the spectral coverage of the ring to shorter wavelengths by adding a narrow-band image at 1.64 μm, and show results from 2.27-μm images over phase angles of 1.2°-11.0°. Our images at 1.64 and 2.27 μm reveal that the halo contribution is stronger at the shorter wavelength, possibly due to the redder spectrum of the ring parent bodies as compared with the halo dust component. We find no variation in main ring reflectivity over the 1.2°-11.0° phase angle range at 2.27 μm. We use adaptive optics imaging at the longer wavelength L′ band (3.4-4.1 μm) to determine a 2-σ upper limit of 22 m of vertically-integrated I/F. Our observing campaign also produced an L′ image of Callisto, showing a darker leading hemisphere, and a spectrum of Amalthea over the 2.2-2.5 and 2.85-3.03 μm ranges, showing deep 3-μm absorption.     

Numerical Studies of Fluid Flow in Microgravity Conditions for Confined Crystal Growth

We study the convective flow induced by residual accelerations in microgravity conditions for different geometric arrangements which are relevant to crystal growth experiments. We consider both constantand oscillating acceleration and focus mostly on the transient relaxation dynamics. Results are relevant to estimate impact of more realistic residual accelerations in crystal growth experiments.