Laboratoire de Géographie Physique

Anodization of titanium and its alloys is an important surface treatment, especially for adhesion applications, but is not as well studied as for aluminium alloys. This paper deals with the morphological, structural and physicochemical characterization of anodic oxide films grown on titanium and Ti–6Al–4V (TA6V) in chromic acid solution without (CA) or with (CA/HF) hydrofluoric acid addition. Several investigations methods are used: high-resolution scanning electron microscopy (HR-SEM), reflection high-energy electron diffraction (RHEED), x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), nuclear reaction analysis (NRA) and wetting angle measurements. The occurrence and morphology of the nanoporous structure for CA/HF anodization are described. The compact films grown in CA solution are amorphous and the porous films grown in the CA/HF solution are partially crystalline. The thickness and morphology of the films are described and discussed as a function of the anodizing conditions and of the composition of the underlying substrate. The composition of the film appears to be TiO2+Al2O3 (with Ti/Al atomic ratio ∽5), with incorporation of fluorine from the solution in the porous films and of small quantities of vanadium in the films that are grown. The specific role played by the Cr(VI) and F species on the film growth-and-dissolution formation process is discussed and a growth mechanism is proposed. Copyright © 1999 John Wiley & Sons, Ltd.

Abstract. The aim of this paper is to provide the community with a comprehensive overview of the studies of glaciers in the tropical Andes conducted in recent decades leading to the current status of the glaciers in the context of climate change. In terms of changes in surface area and length, we show that the glacier retreat in the tropical Andes over the last three decades is unprecedented since the maximum extension of the Little Ice Age (LIA, mid-17th–early 18th century). In terms of changes in mass balance, although there have been some sporadic gains on several glaciers, we show that the trend has been quite negative over the past 50 yr, with a mean mass balance deficit for glaciers in the tropical Andes that is slightly more negative than the one computed on a global scale. A break point in the trend appeared in the late 1970s with mean annual mass balance per year decreasing from −0.2 m w.e. in the period 1964–1975 to −0.76 m w.e. in the period 1976–2010. In addition, even if glaciers are currently retreating everywhere in the tropical Andes, it should be noted that this is much more pronounced on small glaciers at low altitudes that do not have a permanent accumulation zone, and which could disappear in the coming years/decades. Monthly mass balance measurements performed in Bolivia, Ecuador and Colombia show that variability of the surface temperature of the Pacific Ocean is the main factor governing variability of the mass balance at the decadal timescale. Precipitation did not display a significant trend in the tropical Andes in the 20th century, and consequently cannot explain the glacier recession. On the other hand, temperature increased at a significant rate of 0.10 °C decade−1 in the last 70 yr. The higher frequency of El Niño events and changes in its spatial and temporal occurrence since the late 1970s together with a warming troposphere over the tropical Andes may thus explain much of the recent dramatic shrinkage of glaciers in this part of the world.

A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20 ka, 15 ka, 10 ka and 5 ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse 1a. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorities for future work. The synthesis is intended to be a resource for the modelling and glacial geological community.

Lowland Maya civilization flourished in the tropical region of the Yucatan peninsula and environs for more than 2500 years (~1000 BCE to 1500 CE). Known for its sophistication in writing, art, architecture, astronomy, and mathematics, Maya civilization still poses questions about the nature of its cities and surrounding populations because of its location in an inaccessible forest. In 2016, an aerial lidar survey across 2144 square kilometers of northern Guatemala mapped natural terrain and archaeological features over several distinct areas. We present results from these data, revealing interconnected urban settlement and landscapes with extensive infrastructural development. Studied through a joint international effort of interdisciplinary teams sharing protocols, this lidar survey compels a reevaluation of Maya demography, agriculture, and political economy and suggests future avenues of field research.

Dravet syndrome (DS) is a genetically determined epileptic encephalopathy mainly caused by de novo mutations in the SCN1A gene. Since 2003, we have performed molecular analyses in a large series of patients with DS, 27% of whom were negative for mutations or rearrangements in SCN1A. In order to identify new genes responsible for the disorder in the SCN1A-negative patients, 41 probands were screened for micro-rearrangements with Illumina high-density SNP microarrays. A hemizygous deletion on chromosome Xq22.1, encompassing the PCDH19 gene, was found in one male patient. To confirm that PCDH19 is responsible for a Dravet-like syndrome, we sequenced its coding region in 73 additional SCN1A-negative patients. Nine different point mutations (four missense and five truncating mutations) were identified in 11 unrelated female patients. In addition, we demonstrated that the fibroblasts of our male patient were mosaic for the PCDH19 deletion. Patients with PCDH19 and SCN1A mutations had very similar clinical features including the association of early febrile and afebrile seizures, seizures occurring in clusters, developmental and language delays, behavioural disturbances, and cognitive regression. There were, however, slight but constant differences in the evolution of the patients, including fewer polymorphic seizures (in particular rare myoclonic jerks and atypical absences) in those with PCDH19 mutations. These results suggest that PCDH19 plays a major role in epileptic encephalopathies, with a clinical spectrum overlapping that of DS. This disorder mainly affects females. The identification of an affected mosaic male strongly supports the hypothesis that cellular interference is the pathogenic mechanism.

Restrictive dermopathy (RD), also called tight skin contracture syndrome (OMIM 275210), is a rare disorder mainly characterized by intrauterine growth retardation, tight and rigid skin with erosions, prominent superficial vasculature and epidermal hyperkeratosis, facial features (small mouth, small pinched nose and micrognathia), sparse/absent eyelashes and eyebrows, mineralization defects of the skull, thin dysplastic clavicles, pulmonary hypoplasia, multiple joint contractures and an early neonatal lethal course. Liveborn children usually die within the first week of life. The overall prevalence of consanguineous cases suggested an autosomal recessive inheritance. We explored nine fetuses/newborns children with RD. Two were found to have an heterozygous splicing mutation in the LMNA gene, leading to the complete or partial loss of exon 11 in mRNAs encoding Lamin A and resulting in a truncated Prelamin A protein. Lamins are major constituents of the nuclear lamina, a filamentous meshwork underlying the inner nuclear envelope. In the other seven patients, a unique heterozygous insertion leading to the creation of a premature termination codon was identified in the gene ZMPSTE24, also known as FACE-1 in human. This gene encodes a metalloproteinase specifically involved in the post-translational processing of Lamin A precursor. In all patients carrying a ZMPSTE24 mutation, loss of expression of Lamin A as well as abnormal patterns of nuclear sizes and shapes and mislocalization of Lamin-associated proteins was evidenced. Our results indicate that a common pathogenetic pathway, involving defects of the nuclear lamina and matrix, is involved in all RD cases. RD is thus one of the most deleterious laminopathies identified so far in humans caused by (primary or secondary) A-type Lamin defects and nuclear structural and functional alterations.

Polar ice core records attest to a colossal volcanic eruption that took place ca. A.D. 1257 or 1258, most probably in the tropics. Estimates based on sulfate deposition in these records suggest that it yielded the largest volcanic sulfur release to the stratosphere of the past 7,000 y. Tree rings, medieval chronicles, and computational models corroborate the expected worldwide atmospheric and climatic effects of this eruption. However, until now there has been no convincing candidate for the mid-13th century "mystery eruption." Drawing upon compelling evidence from stratigraphic and geomorphic data, physical volcanology, radiocarbon dating, tephra geochemistry, and chronicles, we argue the source of this long-sought eruption is the Samalas volcano, adjacent to Mount Rinjani on Lombok Island, Indonesia. At least 40 km(3) (dense-rock equivalent) of tephra were deposited and the eruption column reached an altitude of up to 43 km. Three principal pumice fallout deposits mantle the region and thick pyroclastic flow deposits are found at the coast, 25 km from source. With an estimated magnitude of 7, this event ranks among the largest Holocene explosive eruptions. Radiocarbon dates on charcoal are consistent with a mid-13th century eruption. In addition, glass geochemistry of the associated pumice deposits matches that of shards found in both Arctic and Antarctic ice cores, providing compelling evidence to link the prominent A.D. 1258/1259 ice core sulfate spike to Samalas. We further constrain the timing of the mystery eruption based on tephra dispersal and historical records, suggesting it occurred between May and October A.D. 1257.

Abstract A major episode of continental crust formation, associated with granulite facies metamorphism, occurred at 2.55–2.51 Ga and was related to accretional processes of juvenile crust. Dating of tonalitic–trondhjemitic, granitic gneisses and charnockites from the Krishnagiri area of South India indicates that magmatic protoliths are 2550–2530 ± 5 Ma, as shown by both U–Pb and 207 Pb/ 206 Pb single zircon methods. Monazite ages indicate high temperatures of cooling corresponding to conditions close to granulite facies metamorphism at 2510 ± 10 Ma. These data provide precise time constraints and Sr–Nd isotopes confirm the existence of late tonalitic–granodioritic juvenile gneisses at 2550 Ma. Pb single zircon ages from the older Peninsular gneisses (Gorur–Hassan area) are in agreement with some previous Sr ages and range between 3200 ± 20 and 3328 ± 10 Ma. These gneisses were derived from a 3.3–3.5‐Ga mantle source as indicated from Nd isotopes. They did not participate significantly in the genesis of the 2.55‐Ga juvenile magmas. All these data, together with previous work, suggest that the 2.51‐Ga granulite facies metamorphism occurred near the contact of the ancient Peninsular gneisses and the 2.55–2.52‐Ga ‘juvenile’tonalitic–trondhjemitic terranes during synaccretional processes (subduction, mantle plume?). Rb–Sr biotite ages between 2060 and 2340 Ma indicate late cooling probably related to the dextral major east–west shearing which displaced the 2.5‐Ga juvenile terranes toward the west.

We examine the problem of partitioning between shortening and extrusion in the India‐Asia collision since 45 Ma. We compute the amount of shortening expected from the kinematics of India's motion with respect to Eurasia, using the reconstruction at collision time to put bounds on the possible amounts of surface loss within Greater India and within Eurasia. We then compute the amounts of surface loss corresponding to the thickened crust of Tibet and of the Himalayas, assuming conservation of continental crust. The spatial distribution of the topography reveals a large systematic deficit of crustal thickening distributed rather uniformly west of the eastern syntaxis but an excess of shortening east of it. This distribution indicates an important eastward crustal mass transfer. However, the excess mass east of the eastern syntaxis does not account for more than one third to one half of the deficit west of the eastern syntaxis. The deficit may be accounted either by loss of lower crust into the mantle, for example through massive eclogitization, or by lateral extrusion of nonthickened crust. A mass budget of the crust of the Himalayas indicates that lower crust has not been conserved there, but the deficit is so large that local loss in the mantle is unlikely to be the unique cause of the deficit. Alternatively, following Zhao and Morgan [1985], lower crust may have been transferred below the Tibetan crust. We conclude that a combination of possible transfer of lower crust to the mantle by eclogitization and lateral extrusion has to account for a minimum of one third and a maximum of one half of the total amount of shortening between India and Asia since 45 Ma. This conclusion leaves open the possibility that the partitioning between extrusion and loss of lower crust into the mantle on the one hand and shortening on the other hand has significantly changed during the 45 m.y. history of the collision.

We have investigated the Coulomb stress interactions of 29 earthquakes (M s ≥6.0) that have occurred in the region of northwest Turkey and north Aegean Sea since 1912. Of these events, 23 may be related to earlier events, and 16 are clearly related to earlier events. All events after 1967 are related to previous events. Events in the early part of our time interval that show no correlation could be related to historical events as yet unidentified. In some cases, faults that have received a stress reduction from earlier events are prepared for an event by an earthquake occurring a few years before that creates a local Coulomb stress rise. Thus regions of Coulomb stress shadow can become regions where a damaging earthquake may occur. The relation between smaller events and the Coulomb stress distribution is less clear, but may be related to poor data quality and practical limitations of our modeling technique. Nonetheless, there are 4 times as many events per unit area in regions of enhanced stress than where stress is reduced. We discuss the contemporary distribution of Coulomb stress and argue that it is possible to identify the likely locations of future damaging earthquakes including identifying the most likely candidate faults.

Paleoenvironmental reconstructions on a (supra-)regional scale have gained attention in Quaternary sciences during the last decades. In terrestrial realms, loess deposits and especially intercalations of loess and buried soils, so called loess-paleosol sequences (LPS) are important archives to unravel the terrestrial response to e.g. climatic fluctuations and reconstruct paleoenvironments during the Pleistocene. The analysis of LPS requires the knowledge of several key factors, such as the distribution of the aeolian sediments, their location relative to (potential) source areas, the climate conditions that led to their emplacement and the topography of the sink area. These factors strongly influence the sedimentological and paleoenvironmental characteristics of LPS and show broad variations throughout Europe, leading to a distinct distribution pattern throughout the continent. We present a new map of the distribution of aeolian sediments (mainly loess) and major potential source areas for Europe. The map was compiled combining geodata of different mapping approaches. Most of the used geodata stems from accurate national maps of 27 different countries. Problematic aspects such as different nomenclatures across administrative borders were carefully investigated and revised. The result is a seamless map, which comprises pedological, geological, and geomorphological data and can be used for paleoenvironmental and archeological studies and other applications. We use the resulting map and data from key geomorphological cross-sections to discuss the various influences of geomorphology and paleoenvironment on the deposition and preservation of Late Pleistocene loess throughout Europe. We divided the loess areas into 6 main loess domains and 17 subdomains to understand and explain the factors controlling their distribution and characteristics. For the subdivision we used the following criteria: (1) influence of silt production areas, (2) affiliation to subcatchments, as rivers are very important regional silt transport agents, (3) occurrence of past periglacial activity with characteristic overprinting of the deposits. Additionally, the sediment distribution is combined with elevation data, to investigate the loess distribution statistically as well as visually. Throughout Europe, the variations, and differences of the loess domains are the results of a complex interplay of changing paleoenvironmental conditions and related geomorphologic processes, controlling dust sources, transport, accumulation, preservation, pedogenesis, alongside erosional and reworking events. Climatic, paleoclimatic, and pedoclimatic gradients are on the continental scale an additional important factor, since there are e.g. latitudinal differences of permafrost and periglacial processes, an increase in continentality from west to east and in aridity from northwest to southeast and south, strongly affecting regional sedimentary and geomorphic dynamics. We propose three main depositional regimes for loess formation in Europe: (1.) periglacial and tundra loess formation with periglacial processes and permafrost in the high latitude and mountainous regions; (2.) steppe and desert margin loess formation in the (semi-)arid regions; and (3.) loess and soil formation in temperate and subtropical regions. Loess deposits of (1.) and (2.) show coarser, sandier particle distributions towards the glacial and desert regions. In the humid areas (3.) forest vegetation limited dust production and accumulation, therefore, there is an increase in finer grain sizes due to an increase in weathering.

We investigate the control of the morphological variables on the 2000–2016 glacier‐wide mass balances of 6,470 individual glaciers of High Mountain Asia. We separate the data set into 12 regions assumed to be climatically homogeneous. We find that the slope of the glacier tongue, mean glacier elevation, percentage of supraglacial debris cover, and avalanche contributing area all together explain a maximum of 48% and a minimum of 8% of the glacier‐wide mass balance variability, within a given region. The best predictors of the glacier‐wide mass balance are the slope of the glacier tongue and the mean glacier elevation for most regions, with the notable exception of the inner Tibetan Plateau. Glacier‐wide mass balances do not differ significantly between debris‐free and debris‐covered glaciers in 7 of the 12 regions analyzed. Lake‐terminating glaciers have more negative mass balances than the regional averages, the influence of lakes being stronger on small glaciers than on large glaciers.

This paper reports isotopic, major and minor element geochemistry of igneous and metamorphic rocks from the Kokoxili and Yushu regions of central and eastern Tibet. The first region lies along the Kunlun suture, which separates the Bayan Har‐Songpan Ganze (Songpan) terrane from the Tarim and Qaidam blocks. Two Kokoxili granitoids yield U‐Pb zircon dates of 217 ± 10 and 207 ± 3 Ma (Late Triassic), which represent the time of emplacement, and Rb‐Sr isochron dates of 195 ± 3 and 190 ± 3 Ma (Early Jurassic), which are interpreted as cooling ages. The geochemical signatures of these granitoids suggest that they are related to subduction continuing into the Late Triassic. In the Yushu area, three samples help constrain the age of the Jinsha suture, which separates the Songpan terranes from the Qiangtang blocks. A leucocratic granite and an orthogneiss in the suture zone yield U‐Pb zircon dates of 206 ± 7 and 204 ± 1 Ma, respectively, and a paragneiss south of it, a U‐Pb monazite date of 244 ± 4 Ma. The existence of coeval magmatism in both the Jinsha and Kunlun sutures suggests that the two subduction zones were simultaneously active. Combining isotopic dating with structural evidence on subduction polarity and paleomagnetic reconstructions, we propose that the Kunlun and Qinling block boundaries, which were distinct in the Permian, subsequently formed a continuous, Late Triassic, northward subducting plate margin. Our data suggest that the Jinsha suture correlates with the Benzilan and Nan‐Uttaradit sutures, which together belong to a major Late Triassic subduction zone.

Abstract Stratigraphic analyses of outcrops, shorelines, and diatoms from the southern Bolivian Altiplano (Uyuni-Coipasa basin) reveal two major lacustrine phases during the late-glacial period and the early Holocene, based on a chronology established by radiocarbon and U/Th control. A comparison of 14 C and 230 Th/ 234 U ages shows that during times of high lake level, radiocarbon ages are valid. However, during low-water periods, 14 C ages must be corrected for a reservoir effect. The lacustrine Tauca phase started a little before 16,000 14 C yr B.P., and the lake level reached its maximum between 13,000 and 12,000 14 C yr B.P. A dry event (Ticaña) occurred after ca. 12,000 and before 9500 14 C yr B.P. A moderate lacustrine oscillation (Coipasa event) occurred between ca. 9500 and 8500 14 C yr B.P., using a reservoir-corrected conventional 14 C chronology. Comparisons between the lake-level chronology in the Uyuni-Coipasa basin and data from other southern tropical areas of South America suggest that the lacustrine evolution may reflect large-scale climatic changes.

The historical trend of aggradation in stream beds of Europe';s mountain and piedmont areas has been reversed since the beginning of the twentieth century to a general tendency towards narrowing and incision. After an overview of some causes and geomorphological effects of river bed incision, and a description of some case studies in alpine rivers, this paper aims to assess how the phenomenon affects the ecosystems of alluvial plains. The questions addressed are, in particular, the effect of river bed incision on sediment redistribution during floods, habitat diversity and the water table; and the consequences of these changes for the distribution and diversity of biological communities. The effect of incision on floodplain vegetation, instream invertebrate communities, groundwater and former channel ecosystems and fish communities are considered. It has been found that incision rarely affects the biocoenoses directly, but indirect changes in habitat conditions are significant. At the scale of the whole hydrosystem, the predicted impact of incision is a decrease in habitat heterogeneity, and, thereby, in biodiversity. At the ecosystem scale, the negative effect on biodiversity is higher in habitats that are less connected to the running water of the river. ©1997 by John Wiley & Sons, Ltd.

Abstract A model for the isotopic composition in δ D and δ 18 O of ice formed by refreezing at the glacier sole is developed. This model predicts relatively well the distribution of points representing samples from basal layers of an Arctic and an Alpine glacier on a δ D– δ 18 O diagram. The frozen fraction which is the part of the liquid that refreezes can be determined for each basal ice layer. This may have implications on the study of the ice–water system at the ice–rock interface.

Macquarie Island has been estimated at 15 million tonnes yr -1 Marine resources are distributed heterogeneously in space and time and are generally related to spatial heterogeneity in physical, chemical and bathymetric features of the marine environment. Studies of the ecology of top predators at sea indicate that their distribution, abundance, and behaviour are related to oceanographic features and primary productivity, as found in seabirds (Pakhomov & Mc-

As climate change and extreme weather events increasingly threaten traditional landscapes and livelihoods of entire communities the need to study its impact on human migration and population displacement has never been greater. The Atlas of Environmental Migration is the first illustrated publication mapping this complex phenomenon. It clarifies terminology and concepts, draws a typology of migration related to environment and climate change, describes the multiple factors at play, explains the challenges, and highlights the opportunities related to this phenomenon. Through elaborate maps, diagrams, illustrations, case studies from all over the world based on the most updated international research findings, the Atlas guides the reader from the roots of environmental migration through to governance. In addition to the primary audience of students and scholars of environment studies, climate change, geography and migration it will also be of interest to researchers and students in politics, economics and international relations departments.

Abstract The Schistes Lustrés (SL) suture zone occupies a key position in the Alpine chain between the high‐pressure (HP) Brianconnais domain and the ultrahigh‐pressure (UHP) Dora Maira massif, and reached subduction depths ranging from c. 40–65 km (Cottian Alps). In order to constrain the timing of HP metamorphism and subsequent exhumation, several phengite generations were differentiated, on the basis of habit, texture, paragenesis and chemistry, as belonging to the first or second exhumation episode, respectively, D2 or D3, or to earlier stages of the tectono‐metamorphic evolution. Ten carefully selected samples showing D2, D3 (D2 + D3), or earlier (mostly peak temperature) phengite population(s) were subjected to laser probe 40 Ar/ 39 Ar analysis. The data support the results of the petrostructural study with two distinct age groups (crystallization ages) for D2 and D3 phengite, at 51–45 and 38–35 Ma, respectively. The data also reveal a coherent age cluster, at 62–55 Ma, for peak temperature phengite associated with chloritoid which were preserved in low strain domains. The age of the D3 event in the SL complex appears very similar to ages recently obtained for greenschist facies deformation on the border of most internal crystalline massifs. Exhumation rates of the order of 1–2 mm yr −1 are obtained for the SL complex, which are compatible with velocities documented for accretionary wedge settings. Similarly, cooling velocities are only moderate ( c .5 °C Myr −1 ), which is at variance with recent estimates in the nearby UHP massifs.

The extraction of a clear and simple footprint of the structure of large, weighted and directed networks is a general problem that has relevance for many applications. An important example is seen in origin-destination matrices, which contain the complete information on commuting flows, but are difficult to analyze and compare. We propose here a versatile method, which extracts a coarse-grained signature of mobility networks, under the form of a 2 × 2 matrix that separates the flows into four categories. We apply this method to origin-destination matrices extracted from mobile phone data recorded in 31 Spanish cities. We show that these cities essentially differ by their proportion of two types of flows: integrated (between residential and employment hotspots) and random flows, whose importance increases with city size. Finally, the method allows the determination of categories of networks, and in the mobility case, the classification of cities according to their commuting structure. The availability of pervasive data has opened up possibilities for quantitative approaches to many phenomena, but extracting useful information from huge datasets is difficult. Here, Louail et al. propose a method to extract a coarse-grained signature of large weighted networks and apply it to mobility networks.