Helmut Echtler

We investigate permafrost surface features revealed from satellite radar data in the Siberian arctic at the Yamal peninsula. Surface dynamics analysis based on SRTM and TanDEM-X DEMs shows up to 2 m net loss of surface relief between 2000 and 2014 indicating a highly dynamic landscape. Surface features for the past 14 years reflect an increase in small stream channels and a number of new lakes that developed, likely caused by permafrost thaw. We used Sentinel-1 SAR imagery to measure permafrost surface changes. Owing to limited observation data we analyzed only 2 years. The InSAR time-series has detected surface displacements in three distinct spatial locations during 2017 and 2018. At these three locations, 60–120 mm/yr rates of seasonal surface permafrost changes are observed. Spatial location of seasonal ground displacements aligns well with lithology. One of them is located on marine sediments and is linked to anthropogenic impact on permafrost stability. Two other areas are loc...

Kyrgyzstan is landlocked mountainous nation of around five million people, which borders China, Kazakhstan, Tajikistan and Uzbekistan. The total area of high mountainous terrain, alpine meadows and pastures exceeds 70% of the Republic's territory, whereas the greater part of the Kyrgyz Republic is occupied by the Tien-Shan mountains. Kyrgyzstan is a highly active seismic region and has been shaken by numerous significant earthquakes as a consequence of the ongoing collision between the Indian and Eurasian tectonic plates. In the result, the mountainous country is faced with a large variety of natural hazards (mainly earthquakes, large landslides and floods) which frequently lead to the occurrence of natural disaster (e.g., 1994: about 1,000 landslides failed and 115 human fatalities; 2008: Nura earthquake M=6.6, 74 human fatalities and 150 injured, 90 glacial lakes endangered for regularly occurring outburst floods). Under these conditions, there is high demand for efficient and...

Bounding flanks of orogenic plateaus are among the most sensitive features for recording the tectonic drivers for and geomorphic responses to surface uplift. Here, processes from the base of the lithosphere to the surface of the crust are integrated in the geologic record, providing key constraints for deciphering the geodynamic processes that drive orogen growth. The southern margin of the

Crustal-scale reverse faults - seismic reflection profiles The ENAP offshore seismic reflection lines co ver the continental shelf of the Arauco region. Our interpretation of these lines reveals high-angle blind reverse faults, associated fault-propagation folds, and related syntectonic sequences. The seismic stratigraphy correlated with ENAP boreholes (Mordojovich, 1981) and the geometry of growth strata documents ~8% of late Pliocene to Recent shortening and landward migration of the deformation. Our mapping of the se structures coincides with the coastaJ geomorphology and shows that the Arauco Peninsula is bounded by NW-striking structures to the south, and NE-striking faults to the north. This convergence focuses shortening and surface uplift, ultimately resulting in the emergence of the Arauco Peninsula during the Quaternary.

Forearc basins along the south-central Chile margin between 34-45°S record a common Neogene tectonic evolution. Subsidence and extension between 10.9 and 3.6 Ma followed by ongoing uplift and contraction since about 2.5 Ma. The first stage has been related to tectonic erosion caused by low trench fill and high convergence rate. The second stage, in turn, follows the onset of glacial denudation in the uplifted Patagonian Andes. Paleoelevation and structural data as well as ages of syncontractional deposits indicate surface uplift in the Patagonian Andes starting at ~14 Ma. Fission-track ages show increasing exhumation rates in the uplifted Main Cordillera since ~7-6 Ma, which is consistent with the oldest morains bracketed between 7-4.6 Ma. In addition, precipitation was presumingly high as the westerlies Pacific winds impinged on the uplifted orogen; thus since ~6-5 Ma material flux to the trench increased. ODP drilling in the trench at 45 and 40°S estimated Plio-Quaternary sedimentation rates of 0.3-1 mm/yr. High trench fill thicknesses resulted in frontal accretion and subduction of terrigenous material. Convergence velocity has continuously slowed during this period, leading to reduced frictional heating, the main contributor to heat flow in cold forearcs, and thus wider seismogenic coupling. Frontal accretion and subduction of trench sediments has decreased the taper angle of the wedge, reducing the margin-normal tensional force as well. We propose that inversion of forearc basins at about 2.5 Ma and onset of the present compressional regime reflects the increase in shear force along the plate interface and decrease in the tensional force and slope of the margin. This process also has caused surface uplift of the Coastal Cordillera and exhumation in the Nahuelbuta ranges. The stationary position of the J.Fernandez Ridge since 10 Ma has limited increased trench fill and consequently forearc basin inversion.

ABSTRACT The ESF-LSF 1997 flight campaign conducted by the German Aerospace Center (DLR) recorded several transects across the island of Naxos using the airborne hyperspectral scanner DAIS. The geological targets cover all major litho-tectonic units of a metamorphic dome with the transition of metamorphic zonations from the outer meta-sedimentary greenschist envelope to the gneissic amphibolite facies and migmatitic core. Mineral identification of alternating marble-dolomite sequences and interlayered schists bearing muscovite and biotite has been accomplished using the airborne hyperspectral DAIS 7915 sensor. Data have been noise filtered based on maximum noise fraction (MNF) and fast Fourier transform (FFT) and converted from radiance to reflectance. For mineral identification, constrained linear spectral unmixing and spectral angle mapper (SAM) algorithms were tested. Due to their unsatisfying results a new approach was developed which consists of a linear mixture modeling and spectral feature fitting. This approach provides more detailed and accurate information. Results are discussed in comparison with detailed geological mapping and additional information. Calcites are clearly separated from dolomites as well as the mica-schist sequences by a good resolution of the mineral muscovite. Thereon an outstanding result represents the very good resolution of the chlorite/mica (muscovite, biotite)-transition defining a metamorphic isograde.

Seismicity, faulting and uplift point to active deformational processes along the South-Central Chilean continental margin and make this area a natural laboratory for investigations of long-term mass transfer patterns at convergent margins. Understanding the factors controlling the tectonic behaviour of the continental margin has some general implications for continental growth and the mass transfer processes in "subduction factories". In order to identify and quantify mass transfer processes we applied apatite and zircon fission track thermochronology along two N-S oriented, trench-parallel sections. The western profile is located within the Permo-Triassic accretionary complex of the Coastal Cordillera and provides information about the timing and magnitude of forearc uplift and/or subsidence. The eastern profile runs through the Main Cordillera and aims towards quantifying the denudation history and understanding the mechanisms of exhumation within the magmatic arc. Early Cretaceous to Early Tertiary fission track ages of the metamorphic and granitoid rocks of the Coastal Cordillera indicate that exhumation of less than 4 km occurred since about the Early Cretaceous. The exhumation rates were variable with time: while geomorphology and sedimentary cover on the basement rocks indicate uplift of several 100m during Pliocene and Quaternary, sedimentary basins suggest subsidence during Miocene times. Therefore, most of the recorded exhumation must be Early Cretaceous to Paleogene in age. The slow and discontinuous exhumation suggests that processes leading to vertical displacements, like basal underplating or tectonic erosion, were not active to any major extent here. In the Main Cordillera, apatite fission track ages at the southern end of the profile (40°S) range from Late Miocene to Late Pliocene, revealing that exhumation there is recent and rapid, with rates of nearly 1 km/Ma during the last 4 Ma. Fission track ages tend to get older along the profile until Eocene fission track ages at the northern end of the profile (38°S) indicate that exhumation there was more than an order of magnitude less efficient. Although variations of the geothermal gradient and tectonics may have influenced the age distribution pattern, climate seems to be an important factor. Younger ages towards the south correlate with drastic increases of precipitation rates and intensity of Pleistocene glaciation.

L'etude structurale detaillee de la nappe de pardailhan et une analyse microtectonique plus regionale demontrent la superposition de differents mecanismes de deformations dans l'evolution varisque polyphasee de la montagne noire. Les nappes plis-couches de son versant sud ne sont developpes dans une phase majeure de tectonique tangentielle a vergence sud-sud ouest. Dans un stade successif de reccourcissement les structures sont replissees dans un systeme progressivement transgressif et decrochant dextre (e-w). La montee contemporaine et subsequente de substratum metamorphique (zone axale) pendant des stades de decompression relative est accompagnee progressivement d'une tectonique en extension caracteristique de l'evolution tardi-orogenique du massif. Des failles normales ductiles et/ou decrochantes extensives marquent ce stade tardif. Elles controlent la mise en place finale des nappes et la formation d'un bassin sedimentaire stephanien au contact avec le complexe cristallin. L'analyse cinematique de la deformation synmetamorphique indique des crisaillements soustractifs dans un relais extensif entre des zones decrochantes dextres. L'amincissement et l'extension tardi-orogenique est attribue au soulevement et au collapse d'un segment crustal epaissie anterieurement. L'ensemble des structures compressives et distensives et des datations radiometriques (#3#9ar-#4#0ar) s'integre dans un modele propose de l'evolution tectonique varisque de la montagne noire