U and Th content in the Central Apennines continental crust: a contribution to the determination of the geo-neutrinos flux at LNGS

The regional contribution to the geo-neutrino signal at Gran Sasso National Laboratory (LNGS) was determined based on a detailed geological, geochemical and geophysical study of the region. U and Th abundances of more than 50 samples representative of the main lithotypes belonging to the Mesozoic and Cenozoic sedimentary cover were analyzed. Sedimentary rocks were grouped into four main "Reservoirs" based on similar paleogeographic conditions and mineralogy. Basement rocks do not outcrop in the area. Thus U and Th in the Upper and Lower Crust of Valsugana and Ivrea-Verbano areas were analyzed. Based on geological and geophysical properties, relative abundances of the various reservoirs were calculated and used to obtain the weighted U and Th abundances for each of the three geological layers (Sedimentary Cover, Upper and Lower Crust). Using the available seismic profile as well as the stratigraphic records from a number of exploration wells, a 3D modelling was developed over an area of 2^{\circ}x2^{\circ} down to the Moho depth, for a total volume of about 1.2x10^6 km^3. This model allowed us to determine the volume of the various geological layers and eventually integrate the Th and U contents of the whole crust beneath LNGS. On this base the local contribution to the geo-neutrino flux (S) was calculated and added to the contribution given by the rest of the world, yielding a Refined Reference Model prediction for the geo-neutrino signal in the Borexino detector at LNGS: S(U) = (28.7 \pm 3.9) TNU and S(Th) = (7.5 \pm 1.0) TNU. An excess over the total flux of about 4 TNU was previously obtained by Mantovani et al. (2004) who calculated, based on general worldwide assumptions, a signal of 40.5 TNU. The considerable thickness of the sedimentary rocks, almost predominantly represented by U- and Th- poor carbonatic rocks in the area near LNGS, is responsible for this difference.Comment: 45 pages, 5 figures, 12 tables; accepted for publication in GC

Speciation in Callitriche (Plantaginaceae): the allopolyploid origin of C. platycarpa

Genomic in situ hybridisation (GISH) experiments involving hybridising labelled genomic DNA from the diploid species C. stagnalis, C. obtusangula and C. cophocarpa to chromosome spreads of the tetraploid C. platycarpa (2n = 4× = 20) show that C. stagnalis and C. cophocarpa DNA each hybridise with a different ten chromosomes of the C. platycarpa complement, whereas C. obtusangula DNA does not differentiate between the two genomes. We conclude on the basis of this and other evidence that C. platycarpa is likely to be an allotetraploid derivative of C. cophocarpa and C. stagnalis. This work demonstrates the successful application of GISH to the study of polyploid evolution in the genus Callitriche

Applying thick-skinned tectonic models to the Apennine thrust belt of Italy - Limitations and implications

Fold-thrust belts are commonly interpreted as "thin-skinned" structures, developed above a detachment, with the underlying basement remaining undeformed. However, in many areas, particularly where compressional tectonism was preceded by rifting, models of basement fault reactivation may be more appropriate. The contrasts between thin-skinned and deep-rooting, inversion-dominated deformation in building fold-thrust complexes are investigated using a case history from the Italian Apennines. Three sectors were chosen to represent the marked lateral variations in structural style evident in the thrust belt. The outer portion of the Marche (in the north) is contrasted with a section through the Lucanian Apennines in the south and with the Molise district of the Central Apennines. The Marche structures are readily explained in terms of inversion, a model that is consistent with new deep seismic data onshore and conventional seismic from the nearby Adriatic Sea. The displacements implicit for the inversion model are a factor of five less than for existing thin-skinned interpretations. However, these styles are not applicable throughout the Apennines. Well data in the Southern Apennines of Lucania demonstrate large-scale thin-skinned thrusting, with 57 km of horizontal displacement since earliest Pliocene time. This includes 14 km of shortening that ramps up through the buried Apulian Platform carbonates. These deeper structures may be restored using ramp-dominated thrust geometries. The Molise sector shows broadly the same structural style as for Lucania: allochthonous shallow-water carbonates and pelagic basin units overlie the carbonates of the Apulian Platform, with the major difference being that here, the pelagic basin units are detached at the level of the Oligocene-lower Miocene Argille Varicolori. In this setting, the Apulian carbonates may be restored using only 5 km of displacement. The overlying allochthon probably has accommodated about 45 km of displacement since the earliest Pliocene. Therefore, the Apennines show differing structural styles with differing displacements along their length. Thick-skinned thrusting models may be applied to the Marche and to structures in the buried Apulian units

Time and space variability of “thin-skinned” and “thick-skinned” thrust tectonics in the Apennines (Italy)

In the Apennine fold and thrust belt of Italy, «thin-skinned» (i.e. detachment-dominated) and «thick-skinned» (i.e. crustal ramp-dominated) structures coexist, but with marked differences in both time and space. The external part of the northern Apennines and the deeper and younger portions (buried Apulian carbonates) of the thrust belt in the central and southern Apennines show limited amounts of shortening (in the range of 5–14 km). These result from similar deformation styles, involving the occurrence of relatively low-displacement, thick-skinned thrust ramps. The latter represent, at least in the northern Apennines, preexisting basement structures reactivated and inverted during contractional deformation. Interposed between the northern and southern parts of the fold and thrust belt, the central Apennines appear to constitute a transitional area in which strike-slip tectonics is relevant and carbonate platform units become predominant over pelagic basin ones, whereas the overall structure of the thrust belt becomes similar to that of the southern Apennines. In the latter, a peculiar structural style is revealed by the integrated analysis of surface and subsurface data. Structurally, the upper part of the thrust belt consists of allochthonous units made of Mesozoic peritidal carbonate platform and pelagic basin successions, and of Miocene foredeep sediments. These are completely detached from their original substratum and transported onto the 6–7 km thick, foreland carbonates of the Apulian platform. Based on available seismic data, the latter appears to be involved, together with the underlying Permo-Triassic clastics and, we infer, also the basement, in relatively low-displacement, thick-skinned structures. Therefore, in the southern Apennines, a transition from thin-to thick-skinned tectonics appears to have occurred through time. Thin-skinned structures characterise the shallower — and older — part of the thrust belt made of detached units, while a thick-skinned tectonic style is dominant in the buried Apulian carbonates of most recent accretion. The present boundary between the two different, superposed portions of the thrust belt consists of a low-angle, large-displacement thrust fault penetrated by numerous oil wells. Different styles and modes of contractional deformation in the investigated sectors of the Apennines appear to result from the geometrical requirement of maintaining strain compatibility and overall displacement continuity along a highly segmented orogen characterised by variable mechanical stratigraphy and southward increasing amounts of shortening

Applying thick-skinned tectonic models to the Apennine thrust belt of Italy: Limitations and implications

Fold-thrust belts are commonly interpreted as “thin-skinned” structures, developed above a detachment with the underlying basement remaining undeformed. However, in many areas, particularly where compressional tectonics was preceded by rifting, models of basement fault reactivation may be more appropriate. The contrasts between “thin-skinned” and deep-rooting, inversion-dominated deformation in building fold-thrust complexes are investigated using a case-history from the Italian Apennines. Three sectors were chosen to represent the marked lateral variations in structural style evident in the thrust belt. The outer portion of the Marche (in the north) is contrasted with a section through the Lucanian Apennines in the south and with the Molise district of the Central Apennines. The Marche structures are readily explained in terms of inversion, a model that is consistent with new deep seismic data onshore and conventional seismic from the nearby Adriatic sea. The displacements implicit for the inversion model are a factor of five less than for existing “thin-skinned” interpretations. However, these styles are not applicable throughout the Apennines. Well data in the Southern Apennines of Lucania demonstrate large-scale thin-skinned thrusting with 57 km of horizontal displacement since earliest Pliocene times. This includes 14 km of shortening that ramps up through the buried Apulian platform carbonates. These deeper structures may be restored using ramp-dominated thrust geometries. The Molise sector shows broadly the same structural style as for Lucania: Allochthonous shallow-water carbonates and pelagic basin units overly the carbonates of the Apulian platform, with the major difference being that here the pelagic basin units are detached at the level of the Oligocene-lower Miocene Argille varicolori. In this setting the Apulian carbonates may be restored using only 5 km of displacement. The overlying allochthon probably accommodated about 45 km displacement since the earliest Pliocene. Therefore the Apennines show differing structural styles with differing displacements along their length. Thick-skinned thrusting models may be applied to the Marche and to structures in the buried Apulian units