64 research outputs found
Low-angle normal faulting and focused exhumation associated with late Pliocene change in tectonic style in the southern Apennines (Italy)
No full textIn the southern Apennines, low-temperature thermochronometry data indicate that exhumation
of previous tectonically buried sedimentary units started at around 10Ma and took placemostly during the last
6Ma. Relatively high exhumation rates are obtained from apatite fission track (AFT) and (U-Th)/He (AHe)
analysis, pointing to a substantial contribution of tectonic processes to rock exhumation besides erosion.
Exhumation rates derived fromnew apatite (U-Th)/He data (AHe) for the last 3Ma are generally lower than rates
determined by AFT data and almost in line with erosion rates inferred from cosmogenic nuclides and sediment
yield, thus suggesting that tectonic exhumation was dominant during the older exhumation stages of
this region. However, younger cooling ages in the Monte Alpi area from both AFT and AHe analyses point
out focused exhumation during the last 3Ma. Structural and morphotectonic analyses indicate that fast
exhumation occurred specifically in this area—where the Apulian Platform reservoir carbonates, elsewhere
buried beneath a several kilometer-thick allochthonous cover, are exposed at the surface—as a result of a
complex interplay between steep-rooted reverse faulting and shallow low-angle extension. This deformation
involved the development of foreland-dipping low-angle normal faults affecting the allochthonous cover units
during the late stages of reverse fault-related anticlinal growth in the underlying buried carbonates. Extension
of the region triggered focused exhumation in the footwall of the extensional low-angle faults, which was
followed by widespread crustal extension and associated development of high-angle normal faults, leading to
surface uplift of Monte Alp
Decoding the role of tectonics, incision and lithology on drainage divide migration in the Mt. Alpi region, southern Apennines, Italy
No full textThe proclivity of river networks to progressively carve mountain surfaces and preserve markers of landscape adjustments has made analyses of fluvial systems fundamental for understanding the topographic development of orogens. However, the transient nature of uplift and erosion has posed a challenge for inferring the roles that tectonics and/or climate have played on generating topographic relief. The Mt. Alpi region in the southern Apennines has a heterogeneous distribution of elevated topography, erosionally-resistant lithology and uplift, making the area optimal for conducting topographic and river analyses to better understand the landscape development of a transient orogen. Stream length-gradient, normalized channel steepness, stream convexity and first-order channel gradient indices from 10 m digital elevation data from the region exhibit stream profile inconsistencies along the current drainage divide and a dominance of high values subparallel but inboard of the primary chain axis irrespective of known transient landscape factors, suggesting that the current river network may be in a state of transition. The location of these stream profile anomalies both near the modern drainage divide and subparallel to an isolated swath of high topography away from catchment boundaries is thought to be the topographic expression of an imminent drainage divide migration driven primarily by the ~ northeast-vergent extension of the western chain axis
Soil contamination compositional index: A new approach to quantify contamination demonstrated by assessing compositional source patterns of potentially toxic elements in the Campania Region (Italy)
No full textPotentially toxic elements (PTEs) are a major worldwide threat to the environment due to the constant global
increase in industrial activity and urbanisation. Several studies have provided detailed maps and a better understanding of the spatial distribution patterns of PTEs in different matrices, but the majority of these studies
have simply neglected the compositional nature of geochemical data. The aims of this study are to reveal the
compositional behaviour and relative structure of 15 PTEs (subcomposition) in Campania, one of the most
contaminated regions in Italy, and to quantify the spatial abundance and identify the possible origins of these
PTEs. Robust compositional biplots were used to understand the natural grouping and origin of the PTEs. Ratios
of specific subcompositions (balances) of PTEs were calculated to map the spatial patterns and identify the
spatial variability of the PTEs. This study presents the preliminary steps needed to quantify and analyse the
relative difference in the spatial abundance of PTEs by applying a compositional abundance index. In addition, a
new soil contamination compositional index (SCCI) was elaborated to quantify topsoil contamination by the 15
PTEs and related subgroups following the compositional structure of the geochemical data.
The elevated spatial abundance of the 15 PTEs is related to highly urbanised (Naples and Salerno), highly
industrialised (Solofra) and intensely cultivated areas (Sarno River Basin), where the high dominance of elements from the anthropogenic subgroup (Pb, Sb, Sn and Zn) and high SCCI values suggest that contamination is
from anthropogenic sources. The high spatial dominance of elements from the volcanic rock subgroup (As, Be,
Se, Tl and V) in these same areas is likely related to geogenic sources, including alkalic pyroclastic rocks.
Although the high spatial abundance of Group B elements (Cd, Cr, Co and Ni) is related to Terra Rossa soils and
shaley facies of siliciclastic rocks of the southern Apennines, these same elements can also reach high abundances and reflect contamination (i.e. high SCCI values) from urbanised and industrialised areas due to e.g.,
tanneries and alloy production.
Other high spatial abundances of the 15 PTEs with little or no contamination (i.e. very low SCCI values) can
be related to nearby carbonate massifs, where a mixture of geogenic factors including weathering, advanced
pedogenic processes, adsorption and co-precipitation with Fe-/Mn-oxyhydroxides and the presence of pyroclastic material might all be responsible for an increase in abundance.
The lowest spatial dominance of the 15 PTEs occurs in the northeastern and southwestern siliciclastic zones of
the Campania Region, where there is a low level of urbanisation and industrialisation and therefore contamination from any source can be excluded
Supplementary data for "Evolution of magmas during late-stage rhyolitic magmatism in the Altiplano-Puna Volcanic Complex as inferred by melt inclusion geochemistry at Cerro La Torta lava dome"
No full textThis repository contains the supplementary data for the publication submitted to the Journal of Volcanology and Geothermal Research entitled "Evolution of magmas during late-stage rhyolitic magmatism in the Altiplano-Puna Volcanic Complex as inferred by melt inclusion geochemistry at Cerro La Torta lava dome".
The excel file contains the complete dataset with major, minor and trace elements composition from melt inclusions, their host minerals (plagioclase and amphibole), accessory minerals (Fe-Ti oxides, apatites, pyroxene and zircon) and groundmass glass from Cerro La Torta lava dome.
Instructions about how to read the dataset are included in the first sheet of the Excel file
Near‐field response to transpression along the southern San Andreas fault, based on exhumation of the northern San Gabriel Mountains, southern California
No full textExhumation in the Chugach-Kenai Mountain Belt Above the Aleutian Subduction Zone, Southern Alaska
No full textMeasurement of the production cross section in the + jets final state in collisions at TeV using the ATLAS detector
No full textSee paper for full list of authors - 37 pages in total, author list starts at page 21, 2 figures, 6 tables, submitted to Phys. Rev. D, all figures and tables including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2015-18/International audienceA measurement of the inclusive production cross section in the final state using only the hadronic decays of the lepton is presented. The measurement is performed using 20.2 fb of proton-proton collision data recorded at a center-of-mass energy of TeV with the ATLAS detector at the Large Hadron Collider. The cross section is measured via a counting experiment by imposing a set of selection criteria on the identification and kinematic variables of the reconstructed particles and jets, and on event kinematic variables and characteristics. The production cross section is measured to be pb, which is in agreement with the measurements in other final states and the theoretical predictions at this center-of-mass energy
Antigenic diversity is generated by distinct evolutionary mechanisms in African trypanosome species
No full textAntigenic variation enables pathogens to avoid the host immune response by continual switching of surface proteins. The protozoan blood parasite Trypanosoma brucei causes human African trypanosomiasis ("sleeping sickness") across sub-Saharan Africa and is a model system for antigenic variation, surviving by periodically replacing a monolayer of variant surface glycoproteins (VSG) that covers its cell surface. We compared the genome of Trypanosoma brucei with two closely related parasites Trypanosoma congolense and Trypanosoma vivax, to reveal how the variant antigen repertoire has evolved and how it might affect contemporary antigenic diversity. We reconstruct VSG diversification showing that Trypanosoma congolense uses variant antigens derived from multiple ancestral VSG lineages, whereas in Trypanosoma brucei VSG have recent origins, and ancestral gene lineages have been repeatedly co-opted to novel functions. These historical differences are reflected in fundamental differences between species in the scale and mechanism of recombination. Using phylogenetic incompatibility as a metric for genetic exchange, we show that the frequency of recombination is comparable between Trypanosoma congolense and Trypanosoma brucei but is much lower in Trypanosoma vivax. Furthermore, in showing that the C-terminal domain of Trypanosoma brucei VSG plays a crucial role in facilitating exchange, we reveal substantial species differences in the mechanism of VSG diversification. Our results demonstrate how past VSG evolution indirectly determines the ability of contemporary parasites to generate novel variant antigens through recombination and suggest that the current model for antigenic variation in Trypanosoma brucei is only one means by which these parasites maintain chronic infections
Insights from low‐temperature thermochronometry into transpressional deformation and crustal exhumation along the San Andreas fault in the western Transverse Ranges, California
No full textThe San Emigdio Mountains are an example of an archetypical, transpressional structural system, bounded to the south by the San Andreas strike‐slip fault, and to the north by the active Wheeler Ridge thrust. Apatite (U‐Th)/He and apatite and zircon fission track ages were obtained along transects across the range and from wells in and to the north of the range. Apatite (U‐Th)/He ages are 4–6 Ma adjacent to the San Andreas fault, and both (U‐Th)/He and fission track ages grow older with distance to the north from the San Andreas. The young ages north of the San Andreas fault contrast with early Miocene (U‐Th)/He ages from Mount Pinos on the south side of the fault. Restoration of sample paleodepths in the San Emigdio Mountains using a regional unconformity at the base of the Eocene Tejon Formation indicates that the San Emigdio Mountains represent a crustal fragment that has been exhumed more than 5 km along the San Andreas fault since late Miocene time. Marked differences in the timing and rate of exhumation between the northern and southern sides of the San Andreas fault are difficult to reconcile with existing structural models of the western Transverse Ranges as a thin‐skinned thrust system. Instead, these results suggest that rheologic heterogeneities may play a role in localizing deformation along the Big Bend of the San Andreas fault as the San Emigdio Mountains are compressed between the crystalline basement of Mount Pinos and oceanic crust that underlies the southern San Joaquin Valley. Key Points There is Pliocene exhumation of the western Transverse Ranges Localization of deformation may be controlled by lithospheric strength Strain is partitioned between the San Andreas and regional thrustsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102707/1/tect20096.pd
Probing the vertex structure in -channel single-top-quark production and decay in collisions at TeV with the ATLAS detector
No full textSee paper for full list of authors - 48 pages in total, author list starting page 32, 10 figures, 5 tables. Submitted to JHEP. All figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2014-17/International audienceTo probe the vertex structure, top-quark and -boson polarisation observables are measured from -channel single-top-quark events produced in proton--proton collisions at a centre-of-mass energy of 8 TeV. The dataset corresponds to an integrated luminosity of 20.2 fb, recorded with the ATLAS detector at the LHC. Selected events contain one isolated electron or muon, large missing transverse momentum and exactly two jets, with one of them identified as likely to contain a -hadron. Stringent selection requirements are applied to discriminate -channel single-top-quark events from background. The polarisation observables are extracted from asymmetries in angular distributions measured with respect to spin quantisation axes appropriately chosen for the top quark and the boson. The asymmetry measurements are performed at parton level by correcting the observed angular distributions for detector effects and hadronisation after subtracting the background contributions. The measured top-quark and -boson polarisation values are in agreement with the Standard Model predictions. Limits on the imaginary part of the anomalous coupling are also set from model-independent measurements
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