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Geology and petrology of the Sasso di Castro ophiolites and associated plagiogranites.
No full textThe Sasso di Castro ophiolite is a huge olistolith within the chaotic complex (late Cretaceous) of the external Liguride unit at Futa Pass, Tuscan Apennines. The ophiolite consists of massive basalts cut by few dykes and overlain by pillow basalts which grade up into pillow basalt breccia covered by red cherts. The whole sequence was affected by ocean-floor metamorphism under static conditions from lower amphibolite to zeolite facies. As opposed to other occurrences in the Northern Apennines, the Sasso di Castro plagiogranites (trondhjemites and very scarce diorites) occur as two small stock-like bodies intruded in the lower part (massive basalt) of the effusive complex. The largest intrusion produced a small thermometamorphic aureole whose hornfelses reached lower amphibolite facies. The thermal effect was associated with fragmentation of the wall-rock and locally also with plastic deformation. Chemical exchange between the host massive basalts and the intruded plagiogranite body has been recognized. The plagiogranites, particularly the trondhjemites, have extremely low K2O (50) ratio. However the presence of a small amount of modal biotite indicates crystallization from a relatively K2O-rich 'granitic' liquid. Low K2O and CaO contents and absence of K-feldspar in the Sasso di Castro plagiogranite probably result from K/Na and Ca/Na exchange in feldspars related to hydrothermal ocean-ridge metamorphism. All the analysed basalts were sampled closely to one another in a quarry. The ratios between refractory elements such Ti, Zr, Nb, Y allow the subdivision of the Sasso di Castro basalts into two groups with high and low Zr/Y; they can be interpreted as two series fractionated from two different parental magmas, which are more enriched in incompatible element than normal MORB. Melting models of the Sasso di Castro basalts as well as of basaltic rocks from Northern Apennines, Western Alps and Corsica ophiolites point to at least two significantly different types of mantle sources: one LREE enriched (Maggiorasca, external Ligurides, Montgenevre, Balagne), the other LREE depleted (Inzecca, Eastern Liguria). It is shown that the Western Mediterranean ophiolite basalts (which are more enriched in incompatible elements than normal MORB) are clearly distinguishable from both transitional and enriched MORB
Glass chemistry in volcaniclastic sediments of ODP Leg 107, Site 650, sedimentary sequence: provenance and chronological implications
No full textA detailed chemical investigation of volcanic glass fragments from volcaniclastic strata (6 tephras, 1 volcanic debris flow, 12 volcanic turbidites) of ODP Leg 107, Site 650, sedimentary sequence, leads to a varied pattern in terms of both provenance and age constraints. The six analyzed tephra strata indicate a provenance from at least three different volcanic provinces: Aeolian, Campanian, and Sicilian Channel (Pantelleria Island). The older tephra strata (021, 018, 012) have a large amount of "orogenic" rhyodacite/rhyolite deposits that may be attributed to the Aeolian province, although no subaerial coeval volcanic activity of similar composition has so far been documented in the Aeolian Arc. Tephra 007 is related to the Pantelleria Island activity and, particularly, to an ignimbrite episode dated circa 130 ka. Tephra strata 005 and 003, have a clear Campanian provenance, and are correlated with analogous tephra layers, observed in the Tyrrhenian and Ionian seas, dated circa 107 and 60 ka respectively. In the oldest portion of the sequence (from 1.3 to 0.13 Ma), the volcaniclastic sediments were only derived from the Aeolian domain whereas in the latest 130 ka, the Campanian influx becomes much more predominant. Therefore, a general K-enrichment trend is observed in the temporal sequence of all the analyzed samples (almost 700 point analyses) which may be related both to a variation in the source area and to the specific Pleistocene magmatic evolution of the peri-Tyrrhenian volcanic provinces. © 1994
I terrazzi marini dell'isola di Panarea (Isole Eolie): loro utilizzo nella definizione dell'eustatismo e del sollevamento tardo-pleistocenico.
No full textTephra layers in late Quaternary sediments of the central Adriatic Sea
No full textMagnetic susceptibility curves of ten cores, collected in the western Adriatic shelf and in the Mid-Adriatic Deep, allowed us to recognize thirty tephra layers whose age, based on physical and biostratigraphic data, encompass a time interval ranging from less than 70 ka to the Present. Chemical features of the tephra, defined by SEM-EDS analyses performed on glass shards, indicate alkaline affinity, mainly with K/Na > 1, and trachytic compositions with two minor benmoreitic and phonolitic groups. These characteristics are consistent with Campanian and subordinate Etnean provenances. Because of chemical and age constraints the glass shards can be referred to six tephra layers already described in the literature, such as C20, C14 (Citara/Ischia), C10 (Campanian Ignimbrite), C2/NYT (Neapolitan Yellow Tuff), AMS/PF (Agnano Monte Spina/Phlegrean Fields) from Campanian area, and Y1 from Etna volcano, indicating an age ranging from about 70 to 4 ka. AMS/PF and C2/NYT, dated 4.4 and 12.3 ka respectively, are the most widespread tephra beds in the study cores. The occurrence of AMS/PF, never recorded in marine sequences up to now, represents a very good marker for Holocene Adriatic sediments; C2/NYT already recorded in the central Tyrrhenian Sea, in lacustrine sediments from southern Italy and in the Campanian area, is a good stratigraphic marker for inter-sea and sea-land correlations. Y1 tephra, dated 14.2 ka, also occurs in on-land sediments of central Italy and in marine sediments from the Tyrrhenian and Ionian seas: it now represents one of the most widespread stratigraphic markers in the central Mediterranean region
Comment to: Volcanic geomorphology and tectonics of the Aeolian Archipelago (Southern Italy) based on integrated DEM data
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
The Strait of Sicily Continental Rift Sistem: Physiography and Petrochemistry of the Submarine Volcanic Centre.
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