Solar constant and sunspots

Summary The relationship, already found by the authors, between sunspot numbers and the solar constant, as deduced from the highest global irradiance values at noon, is here reexamined and confirmed. Some attempts at explanation and further inferences are presented.     

Neogene and quaternary volcanism of the Bijar Area (Western Iran)

In the Bijar region (Western Iran) two distinct volcanic cycles have been recognized. The first, of Upper Miocene age, consists of high-K cale-alkaline volcanic rocks interpreted as final products of the cale-alkaline Tertiary phase of central Iran. The second volcanic cycle, mostly of Pleistocene age (0.5–1.3 m.v.) consists of undersaturated, mainly potassic, alkaline products. As the lavas of this last phase are slightly fractionated, the chemical differences shown by these rocks have been interpreted as primitive features related to the physical conditions governing the partial melting in the mantle and/or the mantle heterogeneity. In a volcanic center (Sarajukh volcano) contemporaneous basic and acid magmas have been found, and interpreted as derived from two different and independent sources. The alkaline basic volcanism is considered as an expression of disjunctive processes that have affected the western margin of the Iranian plate after the Pliocene.     

The geological significance of the manganese-ore mineral facies in the Miocene of the Matese Mountains (Central-Southern Apennines,Italy)

The geologic significance of the Mn-ore existing in sediments of Serravallian and/or Tortonian age of The Matese Mts. (Central-Southern Appennines) has been reinvestigated, according to more recent criteria. Such deposits originated under the influence of peculiar environments, where the instability of the sedimentary basin, preluding to greater tectonic movements, should have created conditions cyclically euxinic, very similar to those occurring in the strata located between Longano and Pietraroia Formations. Unequal tectonics acting upon Miocene sediments after their deposition, should have caused the secondary remobilisation of Mn-minerals, resulting in irregular patterns of lenses and layers of various thickness.     

L'Erosione del litorale di Belvedere Marittimo

Riassunto Si segnala la notevole regressione subita dalla linea di spiaggia di Belvedere Marittimo nel periodo 1913–1938 e se ne discutono i possibili fattori, specie l'effetto del vento sull'erosione del fondo marino, accennando alle indagini intraprese dal R. Istituto Geofisico e Geodetico di Messina.     

Comparison of four meteorite penetration funnels in the Campo del Cielo crater field,Argentina

Abstract– More craters may be discovered in the future, but as it is currently known, the Campo del Cielo crater field is 18 km long by 4 km at its widest point. Such a distribution of craters suggests that the parent meteoroid entered and traversed the atmosphere at a very low angle relative to horizontal. The crater field contains at least 20 small craters produced by the larger fragments of the parent meteoroid. Four of these are explosion analog craters and the rest are penetration funnels. During four field seasons, we have constructed topographic and magnetic maps of four of the penetration funnels as found, and then dug trenches across them to learn their original structures and recover meteorites preserved within them. Structures of these penetration funnels indicate very low angles of impact, i.e., 9–16° relative to horizontal. This supports the idea that the parent meteoroid traversed the atmosphere at a low angle. Data given here for the four penetration funnels include projectile masses, lengths, widths, depths, and estimates of impact angles and azimuths. One of the penetration funnels described here (No. 6) can almost be classified as an explosion analog crater.     

A Rhaetian 40Ar/39Ar age for the Rochechouart impact structure (France) and implications for the latest Triassic sedimentary record

Abstract– ⁴⁰Ar/³⁹Ar dating of potassium feldspar (primary spherulitic‐blocky and secondary idiomorphic K‐feldspar) separated from impact‐metamorphosed gneiss found near Videix in the western central part of the Rochechouart impact structure (NW Massif Central, France) yielded a Rhaetian combined age of 201 ± 2 Ma (2σ), indistinguishable within uncertainty from the age of the Triassic/Jurassic boundary. Ballen quartz intergrown with the primary K‐feldspar indicates post‐shock temperatures exceeding approximately 1000 °C that affected the precursor gneiss. Geochemically, both feldspar types represent essentially pure potassium end‐members. Apart from the approximately 15 km diameter impact deposit area, the youngest crystallization age known for basement rocks in this part of the Massif Central is approximately 300 Ma. No endogenic magmatic‐thermal events are known to have occurred later in this region. The K‐feldspar recrystallized from local feldspar melts and superimposed post‐shock hydrothermal crystallization, probably within some thousands of years after the impact. It is, therefore, suggested that the ⁴⁰Ar/³⁹Ar age for the Videix gneiss (as a potassic “impact metasomatite”) dates the Rochechouart impact, in consistence with evidence for K‐metasomatism in the Rochechouart impactites. The new age value is distinctly younger than the previously obtained Karnian–Norian age for Rochechouart and, thus, contradicts the Late Triassic multiple impact theory postulated some years ago. In agreement with the paleogeographic conditions in the western Tethys domain around the Triassic/Jurassic boundary, the near‐coastal to shallow marine Rochechouart impact is compatible with the formation of seismites and tsunami deposits in the latest Triassic of the British Isles and possible related deposits in other parts of Europe.     

Establishing a 14.6 ± 0.2 Ma age for the Nördlinger Ries impact (Germany)—A prime example for concordant isotopic ages from various dating materials

Abstract– ⁴⁰Ar/³⁹Ar dating of recrystallized K‐feldspar melt particles separated from partially molten biotite granite in impact melt rocks from the approximately 24 km Nördlinger Ries crater (southern Germany) yielded a plateau age of 14.37 ± 0.30 (0.32) Ma (2σ). This new age for the Nördlinger Ries is the first age obtained from (1) monomineralic melt (2) separated from an impact‐metamorphosed target rock clast within (3) Ries melt rocks and therewith extends the extensive isotopic age data set for this long time studied impact structure. The new age goes very well with the ⁴⁰Ar/³⁹Ar step‐heating and laser probe dating results achieved from mixed‐glass samples (suevite glass and tektites) and is slightly younger than the previously obtained fission track and K/Ar and ages of about 15 Ma, as well as the K/Ar and ⁴⁰Ar/³⁹Ar age data obtained in the early 1990s. Taking all the ⁴⁰Ar/³⁹Ar age data obtained from Ries impact melt lithologies into account (data from the literature and this study), we suggest an age of 14.59 ± 0.20 Ma (2σ) as best value for the Ries impact event.     

Search for Phobos and Deimos gas/dust tori using in situ observations from Mars Global Surveyor MAG/ER

More than 490 elliptical aerobraking and science phasing orbits made by Mars Global Surveyor (MGS) in 1997 and 1998 provide unprecedented coverage of the solar wind in the vicinity of the orbits of the martian moons Phobos and Deimos. We have performed a comprehensive survey of magnetic field perturbations in the solar wind to search for possible signatures of solar wind interaction with dust or gas escaping from the moons. A total of 1246 solar wind disturbance events were identified and their distribution was examined relative to Phobos, the Phobos orbit, and the Deimos orbit. We find that the spatial distribution of solar wind perturbations does not increase near or downstream of Phobos, Phobos’ orbit, or Deimos’ orbit, which would have been expected if there is significant outgassing or dust escape from the martian moons. Of the 1246 magnetic field perturbation events found in the MGS data set, 11 events were found within 2000 km of the Phobos orbit, while three events were found within 2000 km of the Deimos orbit. These events were analyzed in detail and found to likely have other causes than outgassing/dust escape from the martian moons. Thus we conclude that the amount of gas/dust escaping the martian moons is not significant enough to induce detectable magnetic field perturbations in the solar wind. In essence we have not found any clear evidence in the MGS magnetic field data for outgassing or dust escape from the martian moons.