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Reply to 'Discussion of "Magnetostratigraphic confirmation of a much faster tempo for sea-level change for the Middle Triassic Latemar platform carbonates" by D.V Kent, G. Muttoni and P. Brack [Earth Planet. Sci. Lett. 228 (2004), 369-377]' By L. Hinnov
No full textHigh-resolution magnetostratigraphic and lithostratigraphic correlations in Middle Triassic pelagic carbonates from the Dolomites (northern Italy)
No full textNew magnetostratigraphic and lithostratigraphic data are reported from the Pedraces and Belvedere limestone sections from the Dolomites region of northern Italy. These sections are comprised of the Buchenstein Beds of Late Anisian to Ladinian (Middle Triassic) age. The results from Pedraces and Belvedere are compared with data from the biostratigraphically and isotopically constrained Frotschbach and Seceda sections from the literature. A satisfactory magnetostratigraphic correlation is obtained on laterally traceable limestone and volcaniclastic intervals. These marker beds are then used to extend lithostratigraphic correlations to additional key sections from a palaeogeographically coherent area of around 500 km2. The aim of this study is to unravel the spatial and temporal evolution of the Buchenstein basin and the surrounding carbonate platforms. Platforms in the northwestern Dolomites show an early stage of aggradation followed by progradation, whereas in the central Dolomites the Cernera platform, after fast initial aggradation, drowned and became a pelagic seamount. In the intervening Buchenstein basin, the differential subsidence between the northwestern and central Dolomites is manifested by the lateral increase of thickness of 'Lower Pietra Verde' volcaniclastic sediments. Accumulation of volcaniclastic material reworked from adjacent carbonate platform slopes characterised the more subsiding and unstable central Dolomites. In the pelagic carbonate intervals, the persistence over tens of kilometres of bedding patterns suggests that carbonate material presumably washed out from the surrounding, still active carbonate platforms was volumetrically small and homogeneously distributed throughout the uniformly subsiding Buchenstein basin. A Milankovitch precessional origin for the platform interior cycles at Latemar as suggested elsewhere implies a net accumulation rate of 2 m/Ma or less for the correlative interval of pelagic Buchenstein Beds. This value differs significantly from the average value of around 10 m/Ma as calculated using high-resolution isotopic age data for the Buchenstein Beds. (C) 2000 Elsevier Science B.V
Comment on: `Magnetostratigraphy and biostratigraphy of the Middle Triassic Margon section (Southern Alps, Italy)' by P.R. Gialanella, F. Heller, P. Mietto, A. Incoronato, V. De Zanche, P. Gianolla, G. Roghi
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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
The Global Boundary Stratotype Section and Point (GSSP) of the LADINIAN STAGE (Middle Triassic) at Bagolino (Southern Alps, Northern Italy) and its implications for the Triassic time scale
No full textThe Global boundary Stratotype Section and Point (GSSP) for the base of the Ladinian Stage (Middle Triassic) is defined in the Caffaro river bed (45°49’09.5’’N, 10°28’15.5’’E), south of the village of Bagolino (Province of Brescia, northern Italy), at the base of a 15–20-cm-thick limestone bed overlying a distinct groove (“Chiesense groove”) of limestone nodules in a shaly matrix, located about 5 m above the base of the Buchenstein Formation. The lower surface of the thick
limestone bed has the lowest occurrence of the ammonoid Eoprotrachyceras curionii (base of the E. curionii Zone; onset of the Trachyceratidae ammonoid
family). Secondary global markers in the uppermost Anisian include the lowest occurrence of conodont Neogondolella praehungarica and a brief normal-polarity
magnetic zone recognized in closely correlated sections including the principal auxiliary section at Seceda in the Dolomites. The GSSP-level is bracketed by U-Pb
single zircon age data from volcaniclastic horizons, indicating a boundary age of ca 241 Ma
Slope Facies of High-Relief, Steep-Slope Triassic Carbonate Platforms (Esino Limestone, Southern Alps, Italy): Sedimentary Processes and Marine Cementation
No full textlope facies in carbonate platforms are characterized by a wide range of textural and sedimentologic features resulting from different types of carbonate producers, source area and depositional processes. Steep slopes are common in high-relief platforms, where they were produced by the dismantling and re-deposition of materials from the slope and reef portions and by carbonate production on the slope itself.
The greenhouse Late Anisian-Carnian high-relief (up to >500 m of platform top to basin relief) carbonate platforms of the Central Southern Alps (Italy) are characterized by prograding steep (25-35° on average) slope facies generally consisting of massive looking, coarse-grained, clast-supported bodies. Volumetrically the slope facies represents the prevailing facies of these carbonate systems. Prograding breccias are organized in m-thick clinostratified, clast-supported layers consisting of boulder to cobbles derived from the erosion of reef-upper slope, as documented by the facies of the clast. Size distribution and internal organization of the slope facies (vertical fining-upward trend and decrease in grain size basinward) indicate the deposition of breccia layers by mass-flow phenomena due to the episodic collapse of portions of the reef-upper slope , separated by periods of carbonate production on the slope (automicrite). The absence of fine-grained sediments indicates a good selection of the clastic carbonate material (original porosity is around 45% on average), whereas crusts of marine isopachous cements indicate a rapid and pervasive cementation, which rapidly reduced the porosity to 4-6% . The nature of the deposits and the interfingering of slope breccias with basinal calciturbidites suggests a different source for the slope and basinal deposits.
The sedimentological analysis of the slope facies of the Late Anisian-Early Carnian platforms of the Central Southern Alps records the sedimentary and early diagenetic processes that resulted in the deposition of huge volumes of massive coarse-grained slope facies, which were characterized by rapid marine cementation. Cement precipitation was thus responsible for 1) the rapid lithification of the reef and upper slope facies (i.e. the source of the clasts of the slope breccias) and 2) the rapid occlusion of the pore space of the slope facies, responsible for the stabilization of the slope itself
Geological Evidences For Late Paleozoic Intra-pangea Dextral Shear
No full textThe Wegenerian configuration of Pangea at Jurassic times, also known as Pangea A, is not questione damong Earth scientists. Debate exists on its pre-Jurassic configu- ration since Ted Irving (1977 Nature) introduced twenty-five years ago Pangea B by placing Gondwana to the East by 2500km with respect to Laurasia on the basis of paleomagnetic data. Pangea B is mainly necessitated by paleolatitude discrepancy be- tween Africa (Gondwana) and North America (Laurasia), which would overlap by about 1700km if reconstructed in a Pangea A configuration at Early Perian times. West Gondwana/Adria poles support Pangea B in the Early Permian, but allow transi- tion to Pangea A by the end of the Permian in the late. stages of the Variscan/Hercynian orogeny (Muttoni et al., 1996 EPSL). Importantly, some of the Early Permian pale- opoles are in igneous rocks and/or from low paleolatitude sites (e.g., Adria), hence making inclination error less likely as an explanation for Pangea B as envisaged by Rochette and Vandamme (2001 Annali di Geofisica). A few Earth scientists tried to seek geological evidence for the pre-Jurassic dextral mega-shear between Gondwana and Laurasia necessary to go from Pangea B or similar configuration to the Pangea A configuration at the time of Atlantic opening in the Jurassic (e.g., Ricou, The Ocean Basins and Margins, Vol. 8, Plenum Press, 1996). Nevertheless, it is fair to say that Pangea B and its tectonic implications have not been broadly accepted but this leaves the problem of the supportive paleomagnetic data unresolved. The ultimate option is to abandon the geocentral axial dipole (GAD) hypothesis by introducing a non-dipole component in the Late Paleozoic paleomagnetic field to explain
the paleolatitude dis- crepancy between Africa and North America (Van der Voo and Torsvik, 2001 EPSL). We are not so distressed by the geological consequences of Pangea B to abandon the GAD hypothesis which has been the basis for virtually all tectonic interpretations us- ing paleomagnetic data. We present new paleomagnetic data from Adria (i.e., West Gondwana) to verify whether Pangea B is paleomagnetically defensible, and review recent geological data from the literature in support of any pre-Jurassic intra-Pangea dextral mega-shear which could be reconciled with the necessary Pangea B to A tran- sition. Relevant geological lines of evidence for Gondwana vs. Laurasia Pangean mo- tions which build on the interpretations of late Hercynian faults sensu Arthaud and Matte (1977 GSA Bulletin) are as follows: (i) Late Paleozoic mantle-scale dextral 1 shear with simultaneous emplacement of orogen-scale granitoids characterized late Hercynian Pyrenees
D2 deformation (e.g., Leblanc et al., Tectonophysics, 261, 1996; Gleizes et al., J. Struct. Geol., 20, 1998, Druguet and Hutton, J. Struct. Geol., 20, 1998). (ii) The Hercynian orogen of Gondwanan France and Iberia has been recently interpreted as the result of the juxtaposition of far-travelled terranes bounded by Late Paleozoic mainly dextral transpressive faults with up to 2000km of dextral displace- ment (Shelley and Bossiere, J. Struct. Geol., 22, 2000). (iii) the Alps preserve evidence for an orogen-scale Permian (trans)tensional event characterized by the emplacement of mafic and ultramafic rocks at the crust-mantle boundary (the Ivrea-Verbano Zone: e.g., Handy and Zingg, Geol. Soc. Am. Bull., 103, 1987; Handy and Streit, Earth Pl. Sc. Lett., 165, 1999; the Malenco Unit: e.g., Trommsdorff et al., Ofioliti, 24, 1999). A similar scenario characterized also the northern Apennines (Marroni et al., Tectono- physics, 292, 1998). Permian magmatic underplating is accompanied by coeval em- placement of granitic and rhyolitic magmatism in shallower levels of the (southern) Alpine crust (e.g., Bozen porphyrites), and volcanosedimentary sequences deposited in dextral pull-apart basins (i.e., Collio Fm.). (iv) central Europe is occupied by ca. 48000km3 of Permian volcanics erupted in a general trans(tensional) regime proba- bly along mantle-scale faults (Beneck et al., Tectonophysics, 266, 1996). These and other geological evidences suggest that docking of Gondwana to Laurasia occurred in a general dextral tectonic regime involving lithosphere-scale processes such as ana- tectic melting and/or magma channeling along shear zones, terranes tectonics, as- thenosphere unroofing and magma underplating which we reconcile with Pangea B to Pangea A transformation in the Late Paleozoic (and therefore not in the Triassic as proposed by Torcq et al. (1997 EPSL). Finally, we would point out that where de- formation is known to be dominated by continental large-scale transcurrent motions (e.g., San Andreas fault system, N. America Cordilleran terranes, New Zealand Alpine fault), it is difficult to find field evidence for more than half of the total displacement of juxtaposed plates/terranes (Umhoefer 2000 Tectonophysics)
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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