The identification of an active fault by a multidisciplinary study at the archaeological site of Sagalassos (SW Turkey)

The archaeological site of Sagalassos (SW Turkey) is located in a region characterized by the absence of any significant recent seismic activity, contrary to adjacent regions. However, the assessment of earthquake-related damage at the site suggests that the earthquakes that have been demonstrated to have struck this Pisidian city in ca. AD 500 and in the middle or second half of the 7th century AD are characterized by an MSK intensity of at least VIII and occurred on a fault very close to the city. Different investigation techniques (archaeoseismology, remote sensing and geomorphology, surface geology and structural data, 2D resistivity imaging and palaeoseismological trenching) have been applied at the archaeological site and its direct surroundings in search for the causative fault of these earthquakes. This multidisciplinary approach shows that each of the different approaches independently provides only partial, non-conclusive information with respect to the fault identification. Integration is imperative to give a conclusive answer in the search for the causative fault. This study has, indeed, revealed the existence of a to date unknown active normal fault system passing underneath ancient Sagalassos, i.e. the Sagalassos fault. A historical coseismic surface rupture event on this fault could be identified. This event possibly corresponds to the devastating Sagalassos earthquakes of ca. AD 500 and the middle or second half of the 7th century AD. Finally, this study demonstrates that in the particular geodynamic setting of SW Turkey archaeological sites with extensive earthquake-related damage form an important tool in any attempt to asses the seismic hazard.     

Seismicity wedge beneath the Upper Rhine Graben due to backwards Alpine push?

The distribution of hypocentres in the Upper Rhine Graben area is re-examined, and discussed with respect to the present day tectonic framework. Most earthquakes occur within a N60° striking wedge, located on top of a Moho dome. This wedge is limited by the surface and at depth, by a plane which, in the south of the dome, coincides with the SE dipping Conrad discontinuity. In depth, the seismicity shows a normal distribution the maximums of which are located on a surface dipping 6° towards SE, parallel to the south-eastward dipping Conrad and Moho. This surface outcrops along the north-western edge of the uplifted crystalline Vosges and Black-Forest. The main shocks in earthquake swarms in the region often occur in the vicinity of this surface and along pre-existing N–S to NE–SW Variscan or Tertiary faults and show focal mechanisms of strike-slip. In contrast, part of the aftershocks show focal mechanisms of reverse faulting associated with SE–NW striking compression. The seismic wedge and the north-westward rising seismic surface suggest initiation of crustal ramp, which starts at the south-eastern rim of the Conrad dome and which may become a thrust plane if SE–NW compression continues. In the south-eastern edge of the graben and above the south-eastern ridge of the Moho dome, where evidences for extension have been found, we identify clustering of hypocentres along a surface that strikes N150°, parallel to the main compression and dipping towards NE. Dominant normal faulting mechanisms along this surface suggests initiation of a normal, probably listric fault. At depth, the onset of the future fault plane is located on top of the NW–SE striking ridge of the lower crust and Moho, which act as a an indenter. In addition to thrusting of the whole wedge towards NW, increasing of NW–SE compression would lead to the formation of a half graben at the place of the present Sierentz depression.     

Volume contents

Volume Contents

Volume contents     

Intrinsic bioremediation of a petroleum-impacted wetland

Following the 1994 San Jacinto River flood and oil spill in southeast Texas, a petroleum-contaminated wetland was reserved for a long-term research program to evaluate bioremediation as a viable spill response tool. The first phase of this program, presented in this paper, evaluated the intrinsic biodegradation of petroleum in the contaminated wetland. Sediment samples from six test plots were collected 11 times over an 11-month period to assess the temporal and spatial petroleum concentrations. Petroleum concentrations were evaluated using gas chromatography-mass spectrometer analyses of specific target compounds normalized to the conservative biological marker, C(30)17alpha,21beta(H)-hopane. The analyses of specific target compounds were able to characterize that significant petroleum biodegradation had occurred at the site over the one-year period. Total resolved saturate and total resolved aromatic hydrocarbon data indicated the petroleum was degraded more than 95%. In addition, first-order biodegradation rate constants were calculated for the hopane-normalized target compounds and supported expected biodegradation patterns. The rapid degradation rates of the petroleum hydrocarbons are attributed to conditions favorable to biodegradation. Elevated nutrient levels from the flood deposition and the unconsolidated nature of the freshly deposited sediment possibly provided a nutrient rich, oxic environment. Additionally, it is suggested that an active and capable microbial community was present due to prior exposure to petroleum. These factors provided an environment conducive for the rapid bioremediation of the petroleum in the contaminated wetland.     

A noble gas and cosmogenic radionuclide analysis of two ordinary chondrites from Almahata Sitta

Abstract– We present the results of a noble gas (He, Ne, Ar) and cosmogenic radionuclide (¹⁰Be, ²⁶Al, ³⁶Cl) analysis of two chondritic fragments (#A100, L4 and #25, H5) found in the Almahata Sitta strewn field in Sudan. We confirm their earlier attribution to the same fall as the ureilites dominating the strewn field, based on the following findings: (1) both chondrite samples indicate a preatmospheric radius of approximately 300 g cm^?2, consistent with the preatmospheric size of asteroid 2008 TC₃ that produced the Almahata Sitta strewn field; (2) both have, within error, a ²¹Ne/²⁶Al‐based cosmic ray exposure age of approximately 20 Ma, identical to the reported ages of Almahata Sitta ureilites; (3) both exhibit hints of ureilitic Ar in the trapped component. We discuss a possible earlier irradiation phase for the two fragments of approximately 10–20 Ma, visible only in cosmogenic ³⁸Ar. We also discuss the approximately 3.8 Ga (⁴He) and approximately 4.6 Ga (⁴⁰Ar) gas retention ages, measured in both chondritic fragments. These imply that the two chondrite fragments were incorporated into the ureilite host early in solar system evolution, and that the parent asteroid from which 2008 TC₃ is derived has not experienced a large break‐up event in the last 3.8 Ga.     

Global significance of oxygen and carbon isotope compositions of pedogenic carbonates since the Cretaceous

Few global syntheses of oxygen and carbon isotope composition of pedogenic carbonates have been attempted,unlike marine carbonates.Pedogenic carbonates represent in-situ indicators of the climate conditions prevailing on land.The δ~(18)O and δ~(13)C values of pedogenic carbonates are controlled by local and global factors,many of them not affecting the marine carbonates largely used to probe global climate changes.We compile pedogenic oxygen and carbon isotopic data(N= 12,167) from Cretaceous to Quaternary-aged paleosols to identify potential trends through time and tie them to possible controlling factors.While discrete events such as the PaleoceneEocene Thermal Maximum are clearly evidenced,our analysis reveals an increasing complexity in the distribution of the δ~(18)O vs δ~(13)C values through the Cenozoic.As could be expected,the rise of C_4 plants induces a shift towards higher δ~(13)C values during the Neogene and Quaternary.We also show that the increase in global hypsometry during the Neogene plays a major role in controlling the δ~(18)O and δ~(13)C values of pedogenic carbonates by increasing aridity downwind of orographic barriers.Finally,during the Quaternary,an increase of 3‰ inδ~(18)O values is recorded both by the pedogenic carbonates and the marine foraminifera suggesting that both indicators may be used to track global climate signal.     

Topical Collection: Climate-change research by early-career hydrogeologists

Scientific outreach, international networking, collaboration and adequate courses are needed in both developed and developing countries to enable early-career hydrogeologists to promote long-term multidisciplinary approaches to cope with climate-change issues and emphasize the importance of groundwater in a global strategy for adaptation. One such collaboration has involved the Early Career Hydrogeologists’ Network of the International Association of Hydrogeologists (ECHN-IAH) and the UNESCO International Hydrological Programme’s (IHP) Groundwater Resources Assessment under the Pressures of Humanity and Climate Changes (GRAPHIC) project. This collaboration seeks to foster the education and involvement of the future generation of water leaders in the debate over groundwater and climate change.     

Can vein-filling speleothems constrain the timing of deep-seated gravitational slope deformation? A case study from the Vinschgau (Italian Alps)

The steep, south facing slopes of the central Vinschgau (Val Venosta, South Tyrol, northern Italy) are characterized by deep-seated compound rockslides affecting 51 km² and reaching beneath the Quaternary valley fill. Morphological features include double ridges, trenches, scarps, and counterscarps, whereby the extent of displacement rises from W to E. Near the toe of these slopes, abundant fractures are present whose orientation and spatial strongly suggest that they are related to the gravitational slope deformations. These fractures host carbonate speleothems which are associated with local tufa occurrences at the surface. Given that the metamorphic host rock is essentially carbonate-free, these carbonate deposits require extensive water-rock interactions to form. Modern springs along the toe of the slope are also mostly supersaturated with respect to calcite and locally also aragonite. The invariant chemical composition, very low tritium levels, and in particular the low oxygen isotope values indicate that this groundwater infiltrates at high elevation and is characterized by a long residence time. On the other hand, local infiltration in the lower reaches of the slope is very limited due to the semiarid climate and is incompatible with the measured groundwater stable isotope composition and the high degree of mineralization. We therefore propose a conceptual model which reconciles the deep-seated gravitational slope deformation with the occurrence of mineralized groundwater and associated carbonate precipitates in fractures near the toe of the slope. These deposits provide a means to place constraints on the timing of rock fracturing and hence the slope movements. U/Th dating of 34 samples from eight sites shows that speleothem deposition started 14.2 ka BP and occurred semi-continuously throughout the Holocene. Thus, gravitational displacements likely commenced with a lag of ~3–4 ka after the deglaciation of the valley, which is also consistent with the few available dates on the onset of other deep-seated slope deformations in the Alps.     

Assessing soil water content spatio-temporal variability at the hillslope scale in a headwater catchment using a multi variable interpolation model based on EMI surveys (Draix,South Alps,France)

To improve flood prediction in headwater catchments, hydrologists need to know initial soil moisture conditions that precede rain events. In torrential hydrology, soil moisture mapping provides a valuable tool for investigating surface runoff generation processes. In these mountainous environments, soil moisture prediction is challenging because of highly heterogeneous land cover and soil properties. This survey propose a methodology to study spatial soil moisture variations in the mountainous and torrential environment of the Draix Bléone experimental site—Laval 0.86 km². This approach associates water content measurements at the plot scale with spatialized soil bulk electrical conductivity (EC_a) measurements combined in a multivariate statistical analysis based on topographical parameters. Between the summer of 2015 and winter of 2016, four geophysical surveys were conducted under various moisture conditions and along the same pathway, using the Slingram electromagnetic induction (EMI) technique (EM31 device) in horizontal dipole to identify changes in soil properties to a depth of 3 m. These results were analyzed to determine water dynamics in this mountainous catchment. Temporal variations of EC_a vary among land cover types (forest, grassland, and black marl). A significant relationship was observed between EC_a and soil water content (SWC) measured with capacitive sensors in forest and grassland. A multiple linear regression produced using the spatial interpolation code LISDQS shows a significant correlation between EC_a and landform units depicted on a high-resolution DEM. EC_a variations decrease with distance to talwegs. Riparian zones appear as potential hydrological contributing areas with patterns varying according to moisture status. This study shows that multiple linear regression analysis and EMI make it possible to fill gaps between SWC plot measurements, over wide areas that are steep and that present numerous obstacles due to vegetation cover.     

Soil quality indicator of oxisols grown with sugarcane and native forest in northeastern São Paulo state,Brazil

The evaluation of soil quality is an important tool for degradation monitoring and sustainable management implementation. The objective of this study was to measure physical and chemical soil properties to set soil quality and validate a model of soil quality indicator in latosols (oxisols) under sugarcane cropping and native forest. The study was carried out in the cities of Araras, Santa Ernestina, and Guariba in São Paulo State, Brazil. We collected 24 samples of disturbed and undisturbed soil at 0.0–0.10 m layer from three areas grown with sugarcane and neighboring locations under native woodland. We assessed the following soil properties: (a) chemical—pH in CaCl₂, organic matter (OM), phosphorus (P), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), potential acidity (H?+?Al), aluminum (Al³⁺), and sulfur (S); (b) physical—macro- and microporosity, soil bulk density (Ds), aggregate stability, mean weight diameter (MWD), rill (K_r) and interrill (K_i) global erodibility, shear stress (τc), and magnetic susceptibility (MS). Data underwent multivariate statistics to identify the properties that denote soil quality and to set their weights within the functions of soil quality indicator (SQI). This study showed that the multivariate analysis was efficient in determining which physical and chemical properties were most sensitive, of which we can mention total sand, MS, clay, microporosity, Mg, Ca, pH, and OM. We can therefore conclude that the quality indicators of soils grown with sugarcane were lower than those under forest were, showing the need for adoption of conservation management practices.