Formation Of F1 Research Articles

Thermal evolution of a Variscan syn-orogenic intracontinental basin (Servoz basin, Western Alps): RSCM geothermometry and geochronology

The Variscan basement of the Aiguilles-Rouges massif (Western Alps) exposes the Servoz syncline which consists of a metavolcano-sedimentary sequence composed of (i) a volcanic unit of unknown age and origin, (ii) Early Carboniferous sedimentary series affected by the Variscan orogeny and intruded by the Montées-Pélissier pluton, and (iii) a Late Carboniferous late-orogenic sedimentary sequence. We combined field investigations, Raman Spectroscopy on Carbonaceous Material geothermometry, and LA-ICPMS U-Th-Pb geochronology on zircon in order to reappraise the sedimentary sequence of the Servoz syncline. Our results allow us to identify three distinct sedimentary formations (F1, F2 and F3). The F1 formation is composed of metagreywackes, bimodal volcanic and magmatic rocks formed during basin opening at an early rifting stage (370–350 Ma) within a back-arc geodynamic setting. This extensional regime was responsible for a high thermal event recorded by a ca. 115 °C/km apparent geothermal gradient. Local anatexis of the basement rocks under the basin is dated at 351 ± 5 Ma. Basin inversion occurred between 350 and 330 Ma in response to oblique collision, with the development of large-scale dextral shear zones and syn-kinematic 340–330 Ma granite intrusions. Subsequent dextral transtension was responsible for the opening of a pull-apart basin between ca. 330 and 310 Ma with the deposition of the F2 phyllite formation that was later deformed by the ongoing dextral transcurrent Variscan tectonics at temperatures between 200 and 350 °C. Finally, the F3 terrigenous sedimentary rocks deposited at ca. 310–290 Ma in a late-orogenic extensional basin. The Alpine-related tectonic event overprinted all the temperatures below 350 °C. Although similar basins have been recognized in other External Crystalline Massifs of the Alps, the Servoz syncline is the first example that allows a major part of the polyphase tectonic evolution, since the early stages of the Devonian, to be recognized. Comparison with similar back-arc basins from the French Central massif, the Vosges massif and the Bohemian massif suggests that the External Crystalline Massifs initially belonged to the Moldanubian hinterlands of the Variscan belt.

Formation and Immediate Deformation of a Small Filament Through Intermittent Magnetic Interactions

It is generally believed that filament formation involves a process of the accumulation of magnetic energy. However, in this paper we discuss the idea that filaments will not erupt and will only deform when the stored magnetic energy is released gradually. Combining high-quality observations from Solar Dynamics Observatory and other instruments, we present the formation and immediate deformation of a small filament (F1) in the active region (AR) 12760 on 28-30 April 2020. Before the filament formation, three successive dipoles quickly emerged with separation motions in the center of AR 12760. Due to the magnetic interaction between magnetic dipoles and pre-existing positive polarities, coronal brightenings consequently appeared in the overlying atmosphere. Subsequently, because of the continuous cancellation of magnetic flux that happened around the adjacent ends of F1 and another nearby filament (F2), the magnetic reconections occurred intermittently occurred between F1 and F2. Finally, F1 lessened in the shear, and F2 became shorter. All the results show that the formation of F1 was closely associated with intermittent interactions between the sequence of emerging dipoles and pre-existing magnetic polarities, and the immediate deformation of F1 was intimately related to intermittent interactions between F1 and F2. We also suggest that the intermittent magnetic interactions driven by the continuous magnetic activities (magnetic-flux emergence, cancellation, and convergence) play an important role in the formation and deformation of filaments.

Site‐to‐site differences in pollinator visitation patterns in a Louisiana iris hybrid zone

We studied pollinator visitation rates and movement patterns in experimental arrays of irises at two sites within a Louisiana iris hybrid zone. Arrays contained single‐flowered stems of red‐flowered I. fulva, blue‐flowered I. hexagona, and purple‐flowered F1 hybrids. At one site, where I. hexagona was the only wild‐growing iris, queen bumble bees were the most common pollinator, and the rank order of pollinator visit rates was I. hexagonaI. fulva. At a second site, where I. fulva predominated in the wild, hummingbirds were the most common pollinators, and this order was reversed: I. hexagona<F1<I. fulva. Thus, at both sites, the naturally occurring iris was visited most frequently and F1 flowers were visited more frequently than the non‐native species. Pollinators used both long‐distance and short‐distance cues to discriminate among flowers, and differences in visit rates seemed to be based on differences in the ease of access to pollen and nectar rewards on flowers of different size. Analysis of movement patterns between flowers showed that pollinators were more likely to make parental‐F1 transitions than heterospecific transitions. These data suggest that pollinator behavior acts as a partial barrier to initial hybridization, although this barrier largely breaks down after F1 formation. Our results help to explain the existence of many introgressed populations of Louisiana iris, despite the fact that F1s are extremely rare in the wild.

Possible hybridization of Brazilian planorbid snails and its importance in population dynamics.

This study focuses on the possibility of experimental hybridization among host snail species for Schistosoma mansoni in Brazil, with morphological characterization of the hybrids found. By using albinism as a genetic marker, intraspecific crossbreedings were performed between two strains of each species involved, in addition to interspecific crossbreedings; the only viable crossbreeding was between pigmented Biomphalaria glabrata (Paulista, PE) and albino B. tenagophila (Joinville, SC), with the formation of F1 and F2 generations. All offspring in F1 displayed black eyes and a renal ridge on the mantle, while F2 displayed dissociated morphological traits. With regard to reproduction, F1 was more efficient than F2. The experiment's results suggest post-zygotic reproductive isolation.

Vertical soundings at Ahmedabad during partial solar eclipse on 14th December 1955

The results of vertical ionospheric soundings at Ahmedabad during the partial (magnitude 47%) solar eclipse on 14th December 1955 are discussed. The critical frequency of the E layer on control days varied according to the lawf oE=kcos n X, k andn having the mean values 4·06 Mc./s. and 0·37 respectively. The variation off oE during eclipse period was roughly consistent with that of Chapman Layer with a recombination coefficient of about 0·8 × 10−8 cm.3 sec.−1 The critical frequencies of E1, E2 and F1 layers decreased during eclipse, though the variations were irregular. The percentage deviation off 0F2 on the eclipse day from the control day values showed a minimum at about the middle of the eclipse period. There were indications of the formation off 1·5 during the latter part of the eclipse. Semi-thickness of the F2 layer had increased during the eclipse period. Sporadic E layer was not affected by the eclipse.