API src

Found 10 results.

Other language confidence: 0.9878922591927216

Geophysical, Sedimentological and Geochemical Data from the Lower Havel Inner Delta (Gülpe Island), Brandenburg (Germany)

To investigate subsurface features in the Lower Havel River floodplain, we conducted Electrical Resistivity Tomography (ERT) transects and Electromagnetic Induction (EMI) surveys at three different depths in 2023 and 2024. These near surface geophysical methods were complemented by 24 driving core drillings to relate the electrical properties with sedimentological characteristics. Additionally, five selected sediment cores were used for subsequent geochemical lab analyses (grain size, CNS, TOC, TIC). Electromagnetic induction (EMI) was measured with a CMD-Mini Explorer (GF Instruments s.r.o., Brno, Czech Republic) in June 2023 and June 2024. We used the vertical dipole (VDP) at coil spacings of 0.32 m (VDP1), 0.71 m (VDP2) and 1.18 m (VDP3), archieving effective penetration depths of 0.5 m (VDP1), 1.0 m (VDP2) and 1.8 m (VDP3). According to the manufacturer, 70% of the signal originate from above these depths. The EMI sensors measure the apparent electrical conductivity (ECa, in mS/m). Measurements were taken by carrying the instrument about 0.2 m above ground while being directly connected to D-GPS (Leica GPS1200) for positioning. The acquisition rate was five measurements per second. Data quality was checked by measuring a reference line before and after each measurement. The area investigated by EMI in June 2023 is located to the north and northeast of the Gülpe research station. It has a total area of 12.3 ha. The reference line was located in the southern part of the study area. No drift correction had to be applied due to good data quality. Reference lines and single outliers were removed. The area investigated by EMI in June 2024 is located southeast of the research station. The survey area there is 8.1 ha in size. The reference line for the measurements there was located in the north-westernmost area of the site. No drift correction had to be applied due to good data quality. Reference lines and single outliers were removed. The Electrical Resistivity Tomography (ERT) data were acquired by using a PC controlled DC resistivity meter system (RESECS, Geoserve, Kiel, Germany). In total, we measured four ERT transects. Two transects in June 2023, where transect 1 had a total length of 259 m with an electrode spacing of 0.5 m and transect 2 had a total length of 223 m with an electrode spacing of 1 m. The measurements in 2023 were carried out under extreme dry conditions. Two further transects were measured in June 2024 with an electrode spacing of 1m, transect 3 with a total length of 207 m and transect 4 with a total length of 239 m. We applied wenner alpha and dipol-dipol configuration. The coordinates and the height of the electrodes were measured with a D-GPS (2023: TOPCON HiPer II / 2024: Leica GPS1200). Sediment cores were recovered using a hand-held Cobra Pro (Atlas Copco) core drilling system with a 60 mm diameter open corer. One-meter segments were retrieved and assessed in the field for sedimentological features, including estimations of grain size, carbonate content, humus content, and redox features (AG Boden 2005, 2024). Colour descriptions were carried out using the Munsell Soil Color Chart. The exact positions of the drilling points were recorded using a differential GPS device (TOPCON HiPer II). The cores were photographed, documented and sampled at 5–10 cm intervals for subsequent laboratory analyses. Bulk samples from five selected cores (RK1, RK3, RK13, RK15, RK17) were freeze-dried, sieved (2 mm), and weighed. Total carbon (TC), total nitrogen (TN), and total sulfur (TS) contents were measured using a CNS analyzer (Vario EL cube, Elementar). Inorganic carbon (TIC) was determined using calcimeter measurements (Scheibler method, Eijkelkamp). Organic carbon (TOC) was calculated as TOC = TC − TIC. For the grain size analyses, sediment samples were first sieved to <2 mm and subsamples of 10 g were treated with 50 ml of 35% hydrogen peroxide (H₂O₂) and gently heated to remove organic matter. Following this, 10 ml of 0.4 N sodium pyrophosphate solution (Na₄P₂O₇) was added to disperse the particles, and the suspension was subjected to ultrasonic treatment for 45 minutes. The sand fraction was analysed by dry sieving and classified into four size classes: coarse sand (2000–630 µm), medium sand (630–200 µm), fine sand (200–125 µm), and very fine sand (125–63 µm). Finer fractions were determined using X-ray granulometry (XRG) with a SediGraph III 5120 (Micromeritics). These included coarse silt (63–20 µm), medium silt (20–6.3 µm), fine silt (6.3–2.0 µm), coarse clay (2.0–0.6 µm), medium clay (0.6–0.2 µm), and fine clay (<0.2 µm).

2D-ERT data measured in June 2023 and June 2024 in the Lower Havel Inner Delta near Lake Gülpe, Brandenburg (Germany)

The Electrical Resistivity Tomography (ERT) data were acquired by using a PC controlled DC resistivity meter system (RESECS, Geoserve, Kiel, Germany). In total, we measured four ERT transects. Two transects in June 2023, where transect 1 had a total length of 259 m with an electrode spacing of 0.5 m and transect 2 had a total length of 223 m with an electrode spacing of 1 m. The measurements in 2023 were carried out under extreme dry conditions. Two further transects were measured in June 2024 with an electrode spacing of 1m, transect 3 with a total length of 207 m and transect 4 with a total length of 239 m. We applied wenner alpha and dipol-dipol configuration. The coordinates and the height of the electrodes were measured with a D-GPS (2023: TOPCON HiPer II / 2024: Leica GPS1200).

2D-ERT data for localizing a Black Death mass grave in Erfurt, Thuringia (Germany)

Near-surface geophysical prospection combined with sediment coring was used to determine the exact location of a Black Death mass grave in Erfurt, Thuringia, Germany. The focus was on exploring the natural stratigraphic and pedogenic environment using sediment coring and geophysical surveys to gain a broader contextual understanding of the site and to determine the most appropriate geophysical methods for locating a mass grave and characterising the natural background. Electrical Resistivity Tomography (ERT) proved to be the most suitable geophysical method. The ERT data were collected by using a PC controlled DC resistivity meter system (RESECS, GeoServe, Kiel, Germany). A total of seven ERT transects were measured, three transects in September 2022, two transects in January 2023 and two transects in June 2023. The electrode spacing was 0.5 m and the transect length varied from 31.5 to 87.5 meter. For the measurements in autumn 2022 we used a Wenner alpha configuration. For the subsequent measurements in 2023, we used Wenner alpha and Dipole-Dipole configuration. The coordinates and the heights of the electrodes in the central wooded area (ERT02, ERT03, ERT04, ERT06 and ERT07) were measured using a total station (Leica TPS1200+). The electrode positions and heights of ERT11 and ERT12 were measured with a differential GPS (Leica GPS1200). Further information on the measurement setup and data structure can be found in the explanation of the specific ERT transects.

2D-ERT data measured in October 2022 in the Ahr floodplain at Mayschoß, Rhineland-Palatinate (Germany)

The Electrical Resistivity Tomography (ERT) data were acquired by using a PC controlled DC resistivity meter system (RESECS, GeoServe, Kiel, Germany) in October 2022. We measured a total of four transects with an electrode spacing 1 m. Transect 1 has a total length of 255 m, transect 2 a total length of 207 m, transect 3 a total length of 136 m and transect 4 a total length of 158 m. For all transects we applied a Wenner alpha and Dipole-Dipole configuration. The coordinates and the height of the electrodes were measured with a Differential-GPS (Leica GPS1200). Further information on the measurement setup and data structure can be found in the explanation of the specific ERT transects.

Near surface geophysical data (Electromagnetic Induction and Electrical Resistivity Tomography) from the Ahr floodplain at Mayschoß, Germany

The dataset was used to explore the spatial distribution of fluvial deposits in the area of the Ahr valley floor southwest of Mayschoß. The objective of this investigation was to extrapolate the findings of a chronological classification of an embedded floodplain cross-section, thereby underscoring the significance of fluvial geomorphological records in reconstructing past high-magnitude flood events. In detail, we used geophysical prospection methods (Electromagnetic Induction and Electrical Resistivity Tomography) to map the distribution and thickness of floodplain sediments as both methods provide proxy information on grain size distribution. Electromagnetic induction (EMI) was measured with a CMD-Mini Explorer and a CMD Explorer (both GF Instruments s.r.o., Brno, Czech Republic) in June 2022. We used the vertical dipole (VDP) at coil spacings of 0.32 m (VDP1, CMD Mini Explorer), 0.71 m (VDP2, CMD Mini Explorer), 1.18 m (VDP3, CMD Mini Explorer), 1.48 m (VDP4, CMD Explorer), 2.82 m (VDP5, CMD Explorer) and 4.49 m (VDP6, CMD Explorer). With the existing coil spacings, effective penetration depths of 0.5 m (VDP1), 1.0 m (VDP2) and 1.8 m (VDP3) for the CMD Mini Explorer and 2.2 m (VDP4), 4.2 m (VDP5) and 6.7 m (VDP6) for the CMD Explorer could be achieved. According to the manufacturer, 70 % of the signal originate from above these depths. The EMI sensors measured the apparent electrical conductivity (ECa, in mS/m). Measurements were taken by carrying the instrument about 0.2 m (CMD Mini Explorer) respectively 0.9 m (CMD Explorer) above the ground while being directly connected to Differential -GPS (Leica GPS1200) for positioning. The acquisition rate was five measurements per second. Data quality was checked by measuring a reference line before and after each measurement. The maximum offset of the EMI values between the two time points was 1.2 mS/m. A correction of the data was not necessary. We removed the reference lines and single outliers. In addition, two interference areas were removed from all EMI data sets. (1) a L-shapped area, running from north to the center and then to east, in which an underground power cable runs. (2) an area on the north-eastern part of the measurement area. Information on the location and extent of the removed interference areas can be found in the enclosed explanation of the EMI measurements. The Electrical Resistivity Tomography (ERT) data were acquired by using a PC controlled DC resistivity meter system (RESECS, GeoServe, Kiel, Germany) in October 2022. We measured a total of four transects with an electrode spacing 1 m. Transect 1 has a total length of 255 m, transect 2 a total length of 207 m, transect 3 a total length of 136 m and transect 4 a total length of 158 m. For all transects we applied a Wenner alpha and Dipole-Dipole configuration. The coordinates and the height of the electrodes were measured with a Differential-GPS (Leica GPS1200). Further information on the measurement setup and data structure can be found in the explanation of the specific ERT transects.

2D-ERT data measured in 2019 in the Loosbach valley near Pestenacker, Bavaria (Germany)

The Electrical Resistivity Tomography (ERT) data were acquired by using a PC controlled DC resistivity meter system (RESECS, GeoServe, Kiel, Germany) in June 2019. We measured two transects with an electrode spacing 0.5 m. For both transects (transect A with a total length of 158 m, transect C with a total length of 103 m) we applied a Wenner alpha configuration. The coordinates and the height of the electrodes were measured with a D-GPS (Leica GPS1200).

Near surface geophysical data (Electromagnetic Induction and Electrical Resistivity Tomography) from the Loosbach valley at Pestenacker, a Late Neolithic wetland site, northern Alpine forelands, Germany

The dataset was used to map the spatial information of the subsurface to build an accurate representative stratigraphy for calculating the carbon storage of the initially degraded peats in a small valley system of the Alpine Foreland in Bavaria; the Loosbach valley at Pestenacker, an UNESCO world heritage site of Late Neolithic wetland occupation. In detail, we used geophysical prospection methods (Electromagnetic Induction and Electrical Resistivity Tomography) to map the distribution and thickness of peat deposits, and conducted direct push sensing and driving core drilling to ground-truth the geophysical data and to sample bulk material for subsequent carbon analysis in the laboratory. Electromagnetic induction (EMI) was measured with a CMD-Mini Explorer (GF Instruments s.r.o., Brno, Czech Republic) in May 2018 and June 2019. We used the vertical dipole (VDP) at coil spacings of 0.32 m (VDP1), 0.71 m (VDP2) and 1.18 m (VDP3). With the existing coil spacings, effective penetration depths of 0.5 m (VDP1), 1.0 m (VDP2) and 1.8 m (VDP3) could be achieved. According to the manufacturer, 70 % of the signal originate from above these depths. The EMI sensors measured the apparent electrical conductivity (ECa, in mS/m). Measurements were taken by carrying the instrument about 0.2 m above the ground while being directly connected to D-GPS (Leica GPS1200) for positioning. The acquisition rate was five measurements per second. Data quality was checked by measuring a reference line before and after each measurement. The maximum offset of the EMI values between the two time points was 1.5 mS/m. We corrected the data and removed the reference lines and single outliers. The data set contains the EMI data with an intercoil spacing of 0.71 m (VDP2) and 1.18 m (VDP3). The measured values of the VDP1 (coils spacing of 0.32 m) could not be used due to a high signal-to-noise ratio. The Electrical Resistivity Tomography (ERT) data were acquired by using a PC controlled DC resistivity meter system (RESECS, GeoServe, Kiel, Germany) in June 2019. We measured two transects with an electrode spacing 0.5 m. For both transects (transect A with a total length of 158 m, transect C with a total length of 103 m) we applied a Wenner alpha configuration. The coordinates and the height of the electrodes were measured with a D-GPS (Leica GPS1200).

gravityInf - inverse hydrological modeling based on gravity observations to evaluate dominant infiltration and subsurface re-distribution processes

gravityInf is a small R-package which aims at supporting the anaylsis of a sprinkling (infiltration) experiment in combination with simultaneous and continious gravity measurements, presented in the above mentioned paper. With this package you can easily walk through the necessary steps in order to set up an infiltration scenario, maybe based on your own sprinkling / irrigation experiment and carry out simple hydrological modelling of water distribution in 3D in the subsurface. An observed gravity time series is needed for the model in order to fit and thus identify the dominant infiltration process for your research area. A model functionality and limitations can be found in Reich et al. (2021), the associtated data was published by Reich et al. (2021, https://doi.org/10.5880/GFZ.4.4.2021.001).

Gravity and ancillary monitoring data of a sprinkling experiment - complemented by model setups and model output

A sprinkling experiment was conducted at the geodetic observatory Wettzell (Bavaria, Germany) with the intention to combine classical hydrological field observations of soil moisture with gravity data and electrical resistivity tomography (ERT). The setup consisted of 8 sprinkling units installed around a gravimeter in field enclosure. Artificial rainfall was applied for 6 hours. The sprinkling area of 15 x 15 m was equipped with 3 vertical soil moisture sensor profiles, 1 horizontal soil moisture transect, near-surface soil moisture sensors and 3 ERT profiles. The non-invasive gravity data and the ancillary monitoring data were used to infer water transport processes in the subsurface during the sprinkling experiment. To this end, the gravity data were used to identify the structure and the parameters of a subsurface flow model in an inverse modelling approach by optimizing the simulated gravity response with respect to the observations. The ancillary soil moisture and ERT data were used to evaluate the model outputs in terms of adequacy and dominant subsurface flow processes. Model data cover the following subtopics: • virtual experiments to show the theoretical relationships between subsurface water re-distribution processes and their corresponding gravity responses • an uncertainty analysis of the sprinkling experiment, e.g., with respect to water volumes and their spatial distribution, and the impact on the expected gravity response • inverse modelling to identify dominant subsurface water re-distribution processes • a synthetical model setup based on the ancillary datasets of soil moisture and ERT Monitoring and model output data used for this investigation is provided within this data repository. A detailed description and discussion can be found in Reich et al. (2021). The inverse modelling was carried out using the R-package gravityInf (Reich, 2021).

Supplement to: 3D Surface-downhole electrical resistivity tomography data sets of the Ketzin CO2 storage pilot from the CO2SINK project phase

Electrical resistivity methods, either in vertical electrical sounding mode or lateral mapping mode, assess the resistivity distribution in the subsurface. Electrical resistivity tomography (ERT) has been successfully applied to image fluid-flow processes at various length scales and depths, mainly with electrodes deployed at the surface.A practical application of the ERT monitoring technique was demonstrated at the geological CO2 storage site in Ketzin (Germany), where time-lapse surface- downhole ERT measurements as well as cross- hole ERT measurements have been carried out during a CO2 injection experiment. In the frame of the multidisciplinary monitoring concept, a combination of surface-downhole(SD) geoelectric measurements was tested (Kiessling et al., 2010) with the objective to enlarge the near-wellbore area, and to address limitations of the individual survey techniques. The geoelectric measurements at the Ketzin site comprise the following survey types: 3D SD-ERT, 2D SD-ERT and Crosshole ERT.The present data publication is focused on the 3D SD- ERT data sets only. Users have the opportunity to assess SD -ERT data in two main steps: The raw field data (voltage and current time -series) and the preprocessed apparent resistivities. The raw field data can be used to apply own preprocessing procedures in order to determine apparent resistivities. Using the pre- processed apparent resistivities, it is possible to start right away into the resistivity inversion.

1