La carta magnetica d'Italia della componente orizzontale al 1940,0 edita recentemente dall'Istituto Geografico Militare

Riassunto L'A., dopo aver brevemente esposto il metodo pratico di misura seguito nelle determinazioni della componente orizzontale del campo magnetico terrestre, riporta un esempio di osservazione ed i valori ottenuti nelle stazioni fondamentali della rete nazionale. Tratta poi della carta italiana delle isodinamiche al 1940,0 pubblicata recentemente dall'Istituto Geografico Militare di cui allega copia alla scala ridotta di 1:4.000.000, pone in rilievo le isodinamiche di particolare andamento anomalo ed accenna infine ai primi lavori di raffittimento magnetometrico posti in programma.

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Zusammenfassung Nachdem der Verfasser kurz das Verfahren besprochen hat, welches zur praktischen Bestimmung der horizontalen Komponente des erdmagnetischen Feldes führt, bringt er ein Beobachtungsbeispiel und die an den Grundstationen des italienischen Netzes erhaltenen Werte. Dann erläutert er die Karte der isodynamischen Linien von Italien für die Epoche 1940,0 die vor kurzem vom Istituto Geografico Militare veröffentlicht und hier in reduziertem Massstab von 1:4.000.000 wiedergegeben worden ist. Es folgen Betrachtungen über die betreffenden Anomalien, sowie über einen Plan zur Abdichtung der erdmagnetischen Stationen in einigen Zonen.

     

La carta magnetica della Libia recentemente compilata dall'Istituto Geografico Militare

Riassunto L'A., richiamate alcune notizie sull'importante rilevamento geomagnetico eseguito nel quinquennio 1932–37 in Italia dall'Istituto Geografico Militare, tratta di quello effettuato recentemente dallo stesso Istituto in Libia negli anni 1938–40, illustrando come è stata compilata la relavita carta delle isogone al 1° gennaio 1941, della quale allega copia. Da tale rilievo risultano zone particolarmente anomale a sud di Tripoli.

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Zusammenfassung Anknüpfend an die geomagnetische Aufnahme Italiens welche in den Jahren 1932–37 vom Istituto Geografico Militare durchgeführt wurde, beschreibt der Verf. die Entwicklungen der geomagnetischen Vermessungsarbeiten in Lybien die in den folgenden Jahren 1938–40 dasselbe Institut gemacht hat. Die betreffenden Ergebnisse sind in einer Isogonen-Karte dargestellt, welche zu den 1. Januar 1941 sich bezieht. Daraus lässt sich u. a. zeigen, dass südlich von Tripoli besonders starke Anomalien auftreten.

     

Tectonic evolution of the internal sector of the Central Apennines, Italy

A wide sector of the internal portion of the Central Apennines, which comprises the southern Lepini Mtns up to the northern Simbruini Mtns has been investigated through detailed field mapping and integrated with structural analyses. A few small productive oil fields and a large number of hydrocarbon seeps and oil impregnations are located in this sector. This area offers good opportunities for testing the use of structural fieldwork methodologies in order to highlight oil migrating paths, from Triassic source rocks, and prospecting chances for oil field exploitation.The main stages of the structural evolution of the area took place after deposition of the foredeep sediments (Frosinone Fm.), i.e. after Late Tortonian, under a stress field characterised by a NE–SW trending σ₁, which was responsible for the early emplacement of major thrust faults present in the area. The Messinian-Early Pliocene thrust-top basin deposits allowed the reconstruction of an in-sequence evolution of the thrust system. The development of out-of-sequence thrusting post-dates these structures leading to a further strong shortening phase in the area during the Pliocene. This phase is characterised by a roughly NNE–SSW trending σ₁. Some peculiar tectonic features evidenced by thrust faults with younger-over-older relationships and an inversion of the original stacking of thrust sheets developed during this phase.Successively, a block-faulting tectonic, mainly with NE–SW extension stress field, occurred and dismembered the compressive tectonic edifice.Later on up to the Middle Pleistocene, N–S to NNE–SSW trending dextral strike-slip faults also acted in the area. Associated to the strike-slip tectonics are local volcanic centres as well as necks, whose compositions show a mantle origin, thus indicating deep seating and a possible lithospheric significance of these structures.In the light of this study, the reduced extension of the productive oil area as well as the spotting of oil seeps, may indicate that the migration conditions are not tied to well defined structures but that likely the cross-cutting points among structures facilitate the conditions for an upwards rising of oil. These conditions in particular are achieved at least in two cases: (1) where the Late Triassic source rocks do not have great depth due to normal or reverse faults, or (2) at a major depth when encountered by transcurrent-oblique roughly N–S trending faults—in both cases oil can easily migrate along the damage zone associated to the fault plane.     

The occurrence and significance of Pleistocene and Upper Pliocene sapropels in the Tyrrhenian Sea

Numerous sapropels and sapropelic strata from Upper Pliocene and Pleistocene hemipelagic sediments of the Tyrrhenian Sea show that intermittent anoxia, possibly related to strongly increased biological productivity, was not restricted to the eastern Mediterranean basins and may be a basin-wide result of Late Pliocene-Pleistocene climatic variability. Even though the sapropel assemblage of the Tyrrhenian Sea clearly originates from multiple processes such as deposition under anoxic conditions or during spikes in surface water productivity and lateral transport of organic-rich suspensates, many “pelagic sapropels” have been recognized. Stratigraphic ages calculated for the organic-rich strata recovered during ODP Leg 107 indicate that the frequency of sapropel formation increased from the lowermost Pleistocene to the base of the Jaramillo magnetic event, coinciding with a period when stable isotope records of planktonic foraminifera indicate the onset of climatic cooling in the Mediterranean. A second, very pronounced peak in sapropel formation occurred in the Middle to Late Pleistocene (0.73-0.26 Ma). Formainifers studied in three high-resolution sample sets suggest that changes in surface-water temperature may have been responsible for establishing anoxic conditions, while salinity differences were not noted in the faunal assemblage. However, comparison of sapropel occurrence at Site 653 with the oxygen isotopic record of planktonic foraminifers established by Thunell et al. (Proc. ODP, Sci. Results 107, 1990) indicates that sapropel occurrences coincide with negative δ¹⁸O excursions in planktonic foraminifers in thirteen of eighteen sapropels recognized in Hole 653A. A variant of the meltwater hypothesis accepted for sapropel formation in the Late Pleistocene eastern Mediterranean may thus be the cause of several “anoxic events” in the Tyrrhenian as well. Model calculations indicate that the amount of oxygen advection from Western Mediterranean Deep Water exerts the dominant control on the oxygen content in deep water of the Tyrrhenian Sea. Inhibition of deep-water formation in the northern Adriatic and the Balearic Basin by increased meltwater discharge and changing storm patterns during climatic amelioration may thus be responsible for sapropel formation in the Tyrrhenian Sea.     

Sedimentary evidence for late Messinian uplift of the SE margin of the Central Anatolian Plateau: Adana Basin,southern Turkey

The Adana Basin of southern Turkey, located at the SE margin of the Central Anatolian Plateau in the vicinity of the Arabia‐Eurasia collision zone, is ideally suited to record Neogene and Quaternary topographic and tectonic changes in the easternmost Mediterranean realm. On the basis of our correlation of 34 seismic reflection profiles with corresponding exposed units along the margins of the Adana Basin, we identify and characterize the seismic facies that corresponds to the upper part of the Messinian Handere Formation (ca. 5.45 to 5.33 Ma), which consists mainly of fluvial conglomerates and marls. The seismic reflection profiles indicate that ca. 1100 km³ of the Handere Formation upper sub‐unit is distributed over ca. 3000 km², reflecting local sedimentation rates of up to 12.5 mm year^?1. This indicates a major increase in both sediment supply and subsidence rates at ca. 5.45 Ma. Our provenance analysis of the Handere Formation upper sub‐unit based on clast counting and palaeocurrent measurements reveals that most of the sediment is derived from the Taurus Mountains at the SE margin of the Central Anatolian Plateau and regions farther north. A comparison of these results with the composition of recent fluvial conglomerates and the present‐day drainage basins indicates major changes between late Messinian and present‐day source areas. We suggest that these changes in drainage patterns and lithological characteristics result from uplift and ensuing erosion of the SE margin of the plateau. We interpret the tectonic evolution of the southern flank of the Anatolian Plateau and the coeval subsidence and sedimentation in the Adana Basin to be related to deep lithospheric processes, particularly lithospheric delamination and slab break‐off.     

Earthquakes in Switzerland and surrounding regions during 2011

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2011. During this period, 522 earthquakes and 92 quarry blasts were detected and located in the region under consideration. With a total of only 10 events with M _L????2.5, the seismic activity in the year 2011 was far below the average over the previous 36?years. Most noteworthy were the earthquake sequence of Sierre (VS) in January, with two events of M _L 3.3 and 3.2, the M _L 3.3 earthquake at a depth of 31?km below Bregenz, and the M _L 3.1 event near Delémont. The two strongest events near Sierre produced shaking of intensity IV.     

Three‐dimensional to two‐dimensional cross‐strata transition in the lower Pleistocene Catanzaro tidal strait transgressive succession (southern Italy)

Sandstone tidal cross‐strata are the predominant sedimentary feature of strait‐fill stratigraphic successions. However, although widely described in numerous studies, tidal strait‐fill two‐dimensional and three‐dimensional cross‐strata have rarely been reported to occur in discrete intervals which are laterally adjacent or vertically stacked, and the meaning of this stratigraphic architecture has not yet been fully investigated. Understanding of the processes responsible for changes in the internal features of modern and ancient tidal bedforms is essential in order to predict lateral and vertical heterogeneities in analogous reservoir strata. This facies‐based study aims to interpret the three‐dimensional to two‐dimensional cross‐strata transition observed in the lower Pleistocene mixed siliciclastic/bioclastic sandstone filling the Catanzaro Strait, in southern Italy, during a continuous phase of tectonically driven marine transgression. Tidal cross‐strata disappear in the uppermost interval of the studied succession, where mudstone strata prevail. This stratigraphic trend is interpreted as the evidence of an important change in the tidal strait hydrodynamics due to a phase of relative sea‐level rise. At the beginning of the transgression, three‐dimensional tidal dunes migrated throughout the ca 3 to 4 km wide and ca 30 km long, WNW–ESE‐oriented Catanzaro Strait, due to strong tidal currents amplified through the seaway and flowing in semi‐diurnal phase opposition. As the intermediate phase of transgression enlarged the seaway width, the tidal current strength decreased as tidal water exchange occurred over a larger cross‐sectional area. The progressive reduction of the bed shear stress modified three‐dimensional tidal dunes into an extensive two‐dimensional bedform field. At the end of the transgression, the further widening of the Catanzaro Strait into a ca 10 to 12 km wide marine passageway changed the tidally dominated strait into a non‐tidal open shelf. The results of this research suggest the presence of a ‘critical cross‐sectional area’ in the narrowest strait‐centre zone which controls the activation and deactivation of tidal current amplification along a marine seaway.     

Could the Twin Towers collapse teach the interaction of dilute pyroclastic density currents with buildings?

Particle-laden turbulent flows, called dilute pyroclastic density currents, can be generated during explosive volcanic eruptions. They are the most hazardous events of interaction with buildings and human environments in volcanic areas. A qualitative comparison with the dusty turbulent shear currents generated after the Twin Towers collapse on September 11, 2001 shows that turbulent, multiphase flow-building interaction causes flow separation and recirculation around the buildings. This simple idea could be applied to dilute pyroclastic density currents, and improved in future by adhoc numerical simulations of flow-building interaction.     

Migration of geothermal fluids in extensional terrains: the ore deposits of the Boccheggiano-Montieri area (southern Tuscany, Italy)

An integrated study based on fluid inclusion, δ¹⁸O composition and structural analyses was carried out on a Pliocene fossil hydrothermal system, located to the South of the present active Larderello geothermal field, in the Boccheggiano-Montieri area. The study area is typified by mineralized cataclastic levels related to Late Oligocene–Early Miocene thrust surfaces, and to the following two generations of normal faults of Miocene and Pliocene ages, respectively. Within the damage zone of the Pliocene Boccheggiano fault, the mineralization is mainly made up of quartz and pyrite. Quartz + Pb–Zn sulfides, or quartz + Pb–Zn sulfides + fluorite + carbonates assemblages occur instead in the older cataclastic levels. Two generations of liquid-rich fluid inclusions were recognized in quartz and fluorite: the first one, with homogenization temperatures ranging between 172 and 331°C and salinity between 0.0 and 8.8 wt.% NaCl_equiv., records the early stage of hydrothermal activity. The second generation of fluid inclusions documents a later stage, with homogenization temperature from 124 to 288°C and salinity from 0.2 to 1.9 wt.% NaCl_equiv.. Fluid inclusions analyses also indicate that mixing of fluid with distinct salinities and/or temperatures was a widespread process during the early stage, and that fluid temperatures decreased moving from the Boccheggiano fault toward the more distal and older cataclastic levels. The δ¹⁸O values of water in equilibrium with hydrothermal quartz, which range from −5.7 to −0.1‰, are related to the circulation of meteoric water mixed with saline water that leached the evaporite level and enriched in δ¹⁸O through water–rock interaction, and/or with magmatically derived fluids. Results indicate that the damage zone of the Pliocene Boccheggiano fault represented the main channel for the flow of meteoric water, which was heated at depth, then mixed with high salinity fluids, and finally ascend to infiltrate along the older cataclastic levels. Our results, based on fluid inclusions, oxygen isotopic compositions and structural analyses indicate that a single fluid flow path run through the damage zone of the Boccheggiano fault and the older cataclasites, which were thus hydraulically connected.     

Diagnostics,deterioration and provenance of stone materials from the Jefferson Page tomb (Non-Catholic Cemetery of Rome,Italy)

The monumental tomb of Jefferson Page, an officer in the American Navy, was built in 1899 and is located in the Non-Catholic Cemetery of Rome (Italy). This study presents complementary diagnostic studies characterizing the stone of the tomb and the weathering and decay phenomena it has undergone. The monument is made of a single type of whitish marble, variously veined and often covered with black patinas. Petrographic, isotopic and LA-ICP-MS analyses attribute the marble to the Carrara district. SEM/EDS and microbiological analyses indicate that the black patinas are due to cyanobacterial autotrophic and fungin heterotrophic colonization. Fourier-transform infrared spectroscopy revealed the presence of organic material on some portions of the tomb, due to undocumented restoration carried out with a mixture of marble powder and a polyester resin.