Drill Sites Research Articles

3D structural and petrophysical modeling of Qishn sandstone reservoir in Sharyoof field, Say'un-Masilah basin, Yemen

The complex geological structures, of the Sharyoof field in the Say'un-Masilah Basin of Yemen, make obtaining accurate information about the hydrocarbon entrapment style difficult. This situation adversely affects the efficiency of the exploration. Therefore, the present study provides a detailed character analysis of subsurface structural features as well as determines the entrapment style of Early Cretaceous age hydrocarbons (the Qishn Sandstone Reservoir) in the Sharyoof oil field. To identify accurate structural features, calculate petrophysical parameters of the Qishn sandstone member and predict their complex geometry in a 3D model, this investigation is based on the analysis of a multidisciplinary data set. The three-dimensional modeling was based on the interpretation of 2D seismic profiles and well logs data analysis. The obtained results indicate two types of a normal faults, consisting of plane faults and antithetic faults, which are oriented NE-SW and NW-SE with a thickness variation from 76 to 153 m. The intersection of these faults resulted in horst structures, in the northwest and southwestern parts, and graben and half-graben structures, in the southern and southeastern parts of the study area. The dips of these faults are between 20 and 90°. The 3D models of petrophysical parameters and the cross section extracted from the 3D model demonstrated that the Qishn sandstone reservoir has a low clay volume while having high porosity, permeability and hydrocarbon saturation values. Furthermore, the Qishn Sandstone is overlain by layers of the Qishn Carbonate Member, which has very low porosity and permeability and high clay volume, making it an effective seal. Therefore, these novel findings could be used to propose a drilling site for exploration wells within the Qishn Clastics membership.

A Proper Use of the Adjacent Land‐Based Observatory Magnetic Field Data to Account for the Geomagnetic Disturbances During Offshore Directional Drilling

AbstractDirectional drilling in the oil fields relies particularly on the “on‐fly” measurements of the natural magnetic field (measurements while drilling; MWD); the MWD are eventually used to construct the well path. These measurements are the superposition of the signals from the internal, core and crustal, and external, ionospheric and magnetospheric sources and the noise from magnetic elements in the borehole assembly. The internal signals are mostly constant in time and accounted for through the Earth's internal field models. The signals of external origin give rise to diurnal and irregular spatio‐temporal magnetic field variations observable in the MWD. One of the common ways to mitigate the effects of these variations in the MWD is to correct readings for the data from an adjacent land‐based magnetic observatory/site. This method assumes that the land‐based signals are similar to those at the seabed drilling site. In this paper, we show that the sea level and seabed horizontal magnetic fields differ significantly, reaching up to 30% of sea level values in many oceanic regions. We made this inference from the global forward modeling of the magnetic field using realistic models of conducting Earth and time‐varying sources. To perform such modeling, we elaborated a numerical approach to efficiently calculate the spatio‐temporal evolution of the magnetic field. Finally, we propose and validate a formalism allowing researchers to obtain trustworthy seabed signals using measurements at the adjacent land‐based site and exploiting the modeling results, thus without needing additional measurements at the seabed site.

Identification and analysis of Salado Formation amplitude anomalies in the Midland Basin

Careful mapping of shallow drilling hazards is key to operating an oil field safely and economically. In the Midland Basin, historical information indicates that shallow gas in the Salado Formation may result in blowouts. By using recently acquired higher-resolution 3D seismic surveys, we can identify circular high-amplitude anomalies that we interpret to be nitrogen-filled gas pockets. The larger pockets can be mapped and avoided before drilling a well. Detecting gas pockets in the Salado Formation may require modern 3D coverage or higher-resolution seismic drill site surveys if older low-fold seismic data are available at the drilling locations. The smallest pockets may not be detectable by any means. Although some of the larger anomalies are visible on older 3D surveys, most only became visible with the advent of higher-fold denser 3D seismic surveys. The anomalies sometimes follow a linear pattern. However, most are isolated in nature and appear as circular features in plan view and usually lenticular or columnar in section view. The anomalies range in size from a few traces in width (tens of feet or meters) to more than 1000 ft (300 m) in width or length. Seismic modeling suggests that the anomalies are very low P-wave velocity zones (about half of the velocity of the surrounding salt) and exhibit longer seismic traveltimes or push-down effects on reflections underneath the larger anomalies.

Accuracy evaluation of 3D-printed guide-assisted flapless micro-osteoperforations in the anterior mandible.

To evaluate the accuracy of tridimensional (3D)-printed guide-assisted flapless cortical bone micro-osteoperforations (MOPs) in the anterior mandible on a cadaver model. Five human cadaver heads with complete dentition in the anterior mandible were used in the present study. Preplanning CBCT and intraoral surface scans were obtained. After alignment, drilling sites in the interradicular areas were planned from canine to canine, and a surgical guide was printed. The drilling was performed and a postprocedure CBCT scan was obtained to assess the accuracy of the procedure in relation to the virtual planning. The mean ± standard deviation (SD) mesiodistal interradicular space was 2.67 ± 0.84 mm. The mean ± SD error of the actual drilled hole compared with the planned position of the mesial drill site was 0.66 ± 0.33 mm, and to the distal drill site it was 0.56 ± 0.33 mm. There was a statistically significant difference between the number of times the teeth were hit mesially (10 out of 64 holes) and distally (none). The proposed technique, limited to an ex vivo scenario, provides a valid and reliable method for mandibular MOPs using a 3D-generated surgical guide. However, the risk of damaging adjacent radicular surfaces, particularly in areas with limited mesiodistal interradicular bone, needs to be considered. Further studies should focus on using thinner drills and adding other methods to stabilize the guide. Additionally, by selecting individuals and perforation sites with more mesiodistal interradicular bone, less damage is likely. (Int J Comput Dent 2022;25(4):387-0; doi: 10.3290/j.ijcd.b2599841).

Dating seafloor spreading of the southwest sub-basin in the South China Sea

Marine magnetic lineations play important role in interpreting the age and spreading processes of the oceanic crust. However, it is difficult to identify magnetic lineations from sea surface observations in a deep and narrow low-latitude slow-spreading inactive ocean basin for many reasons, such as the highly filtered low-amplitude magnetic anomalies, highly oblique magnetization, contamination from narrow stripes, etc., which may hamper accurate lineation discrimination and identification. The spreading history of the Southwestern Sub-basin of the South China Sea (SW-SCS), which is located in such a low-latitude tectonic setting, has been debated for a long time. Near-seafloor deep-tow magnetic measurements provide high-resolution reversal records, making accurate lineation discrimination feasible. Corrections, including diurnal variation correction, regional field correction, and de-skewing, are explored. The results, calibrated with drill sites from the International Ocean Discovery Program (IODP) Expedition 349, show that the spreading ages of the SW-SCS range from ∼ 21 to 15 Ma (from C6A to C5B) and the full spreading rate ranges from 26 to 46 mm/yr, with an average rate of 37 mm/yr. Spreading was initially symmetric but later became asymmetric, with a rate differential reaching 10%. Combined with two seismic profiles, it is found that the roughness of the oceanic basement to the south of the extinct ridge is mainly influenced by faulted blocks, whereas to the north it is mainly influenced by magmatism. The RMS seafloor roughness is estimated to be 211 m in the south and 191 m in the north respectively. This indicates that SW-SCS seafloor spreading tends to be a transition type between axial high and axial low at the intermediate-slow spreading rate. There is a large valley in the spreading center, but the roughness far away from the center is low. the RMS basement roughness is obviously lower than that of the typical slow spreading oceanic basin. we conjecture that the larger than normal syn-spreading magma may be the reason for the low roughness. A long history of being subducted might be the deep-seated reason for all these behaviors where, and the mantle is rich in water and carbon.

Probabilistic inversion of audio-frequency magnetotelluric data and application to cover thickness estimation for mineral exploration in Australia

We have applied a Bayesian inference algorithm and released open-source code for the 1D inversion of audio-frequency magnetotelluric data. The algorithm uses a trans-dimensional Markov chain Monte Carlo technique to solve for a probabilistic resistivity-depth model. The inversion employs multiple Markov chains to generate an ensemble of millions of resistivity models that adequately fit the data given the assigned noise levels. The trans-dimensional aspect of the inversion means that the number of layers in the resistivity model is solved for rather than being predetermined. The inversion scheme favours a parsimonious solution and the acceptance criterion ratio is theoretically derived such that the Markov chain will eventually converge to an ensemble that is a good approximation of the posterior probability density (PPD). Once the ensemble of models is generated, its statistics are analysed to assess the PPD and to quantify model uncertainties. This approach gives a thorough exploration of model space and a more robust estimation of uncertainty than deterministic methods allow.We demonstrate the application of the method to cover thickness estimation for a number of regional drilling programs. Comparison with borehole results demonstrates that the method is capable of identifying major stratigraphic units with resistivity contrasts. Our results have assisted with drill site targeting and have helped to reduce the uncertainty and risk associated with intersecting targeted stratigraphic units in covered terrains. Interpretation of the audio-frequency magnetotelluric data has improved our understanding of the distribution and geometries of sedimentary basins. From an exploration perspective, mapping sedimentary basins and covered near-surface geological features supports the effective search for mineral deposits in greenfield areas.

New Approach for Developing Correlation of NSPT and Shear-Wave Velocity (Vs): Bantul Case Study

DOI:10.17014/ijog.9.3.395-413Predictions of ground motion levels that, under certain conditions, may cause liquefaction require a sufficient knowledge of the underlying soil characteristics. The utilization of the seismic refraction method applies measurements of the subsurface shear-wave velocities (Vs) as a representation of the properties of stiffness and soil amplification. This study, carried out in Bantul, Yogyakarta Province, Indonesia, is conducted to determine the relationship between Standard Penetration Test N values (NSPT) and Vs by using data from eighty-eight drill sites and twenty-nine seismic reflection investigations with the statistical method, namely the Statistical Gradation Approach. The new equations, developed from a power regression analysis, are applied to all soil and eight soil types: silty sand, sand, gravelly sand, clay, silt, sandy clay, clay sand, and sandy silt. The equations, proposed to predict Vs, show a strong relationship between NSPT and Vs values, which applied to other regions with the shear-wave velocity of <300 m/sec, shallow groundwater depth, and dominant sandy soil.

CAGE21-3 Cruise Report: Ocean bottom seismics and acoustic surveys on the West-Svalbard margin – a study of local seismicity and its effect on methane seepage

Cruise CAGE21-3 with UiT’s research vessel R/V Helmer Hanssen was carried out to address the following objectives within the SEAMSTRESS project (Tectonic stress effects on Arctic methane seepage):1- Recovery of 10 Ocean Bottom Seismometers (OBS) deployed last year north of the Knipovich Ridge-Molloy Transform Fault corner (see report CAGE20-5).2- Conduction of an active source OBS experiment for the study of shear waves propagation in relation to local stress field and focused fluid flow.3- Acquisition of seismic lines for completing a side survey for the FRAME-IODP proposal.In 2020, 10 ocean-bottom seismometers (OBS) were deployed at the northern termination of the Knipovich Ridge to monitor seismic activity. The aim is to detect regional and local earthquakes. If localearthquakes are captured we will investigate the stress field in the region and how faults and fluids react to such stress (Figure 1). From the 10 instruments 8 are from Awi and 2 from UiT. IODP proposal 985 Eastern Fram Strait Palaeo-archive (FRAME) proposed to drill five sites on the western Svalbard margin in order to study chronostratigraphy, palaeoceanography, the palaeoclimatic evolution, and the forcing mechanisms responsible for main climatic transitions and the dynamics of the Svalbard Barents Sea Ice Sheet complex. This cruise acquired additional site survey seismic data for proposed primary and alternate drill sites. The cruise may be known as: CAGE21_3

Drilling Overdeepened Alpine Valleys (ICDP-DOVE): quantifying the age, extent, and environmental impact of Alpine glaciations

Abstract. The sedimentary infill of glacially overdeepened valleys (i.e., structures eroded below the fluvial base level) is an excellent but yet underexplored archive with regard to the age, extent, and nature of past glaciations. The ICDP project DOVE (Drilling Overdeepened Alpine Valleys) Phase 1 investigates a series of drill cores from glacially overdeepened troughs at several locations along the northern front of the Alps. All sites will be investigated with regard to several aspects of environmental dynamics during the Quaternary, with focus on the glaciation, vegetation, and landscape history. Geophysical methods (e.g., seismic surveys), for example, will explore the geometry of overdeepened structures to better understand the process of overdeepening. Sedimentological analyses combined with downhole logging, analysis of biological remains, and state-of-the-art geochronological methods, will enable us to reconstruct the erosion and sedimentation history of the overdeepened troughs. This approach is expected to yield significant novel data quantifying the extent and timing of Middle and Late Pleistocene glaciations of the Alps. In a first phase, two sites were drilled in late 2021 into filled overdeepenings below the paleolobe of the Rhine Glacier, and both recovered a trough filling composed of multiphase glacial sequences. Fully cored Hole 5068_1_C reached a depth of 165 m and recovered 10 m molasse bedrock at the base. This hole will be used together with two flush holes (5068_1_A, 5068_1_B) for further geophysical cross-well experiments. Site 5068_2 reached a depth of 255 m and bottomed out near the soft rock–bedrock contact. These two sites are complemented by three legacy drill sites that previously recovered filled overdeepenings below the more eastern Alpine Isar-Loisach, Salzach, and Traun paleoglacier lobes (5068_3, 5068_4, 5068_5). All analysis and interpretations of this DOVE Phase 1 will eventually lay the ground for an upcoming Phase 2 that will complete the pan-Alpine approach. This follow-up phase will investigate overdeepenings formerly occupied by paleoglacier lobes from the western and southern Alpine margins through drilling sites in France, Italy, and Slovenia. Available geological information and infrastructure make the Alps an ideal area to study overdeepened structures; however, the expected results of this study will not be restricted to the Alps. Such features are also known from other formerly glaciated mountain ranges, which are less studied than the Alps and more problematic with regards to drilling logistics. The results of this study will serve as textbook concepts to understand a full range of geological processes relevant to formerly glaciated areas all over our planet.

Metal Exposures in Residents Living Near an Urban Oil Drilling Site in Los Angeles, California.

Urban environmental justice communities are potentially exposed to multiple toxic metals, through contaminated air, soil, water, and food. However, information on metals and their sources is lacking. This study uses non-negative matrix factorization (NMF) in a community-based participatory research study to identify potential sources and to understand how these metals cluster in a population near an urban oil drilling site. We recruited 203 Latinx, Black, and Asian residents who lived within 1 km of an oil drilling site in south Los Angeles and collected toenail clippings to assess exposure to arsenic (As), cadmium (Cd), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), and antimony (Sb). Using NMF, we identified three clusters based on concentrations in the participants' toenails. As, Cd, Pb, and Sb grouped together, indicative of an industrial source. A second grouping was composed of Ni and Mn, which may be related to oil drilling. We also identified a third source factor predominantly driven by Hg and As, which may arise from dietary sources. Utilizing NMF, a dimension reduction method, we identified a source factor high in Ni and Mn in residents living in a neighborhood near an active oil drilling site.

Heat flux estimation from borehole temperatures acquired during logging while tripping: a case study with the sea floor drill rig MARUM-MeBo

During trip out of the drill string at the end of a drilling operation (logging while tripping) borehole temperatures can be measured without the need for additional operational time. A simple interpretation of the measured borehole temperatures is difficult due to the interfering influences of the drilling operations, mainly due to flushing the borehole during drilling. In this study, we present borehole temperature data from drilling campaigns with the sea floor drill rig MARUM-MeBo200 at the Danube Deep Sea Fan (Black Sea) and west of Taiwan (South China Sea). The temperature measurements were conducted with a PT1000 temperature sensor which is integrated in a memory acoustic borehole logging tool. We developed a modeling approach in order to simulate the drilling perturbations and subsequent evolution of the temperature field within the borehole. By fitting the model data to the measured time dependent temperature depth profiles, we estimated the undisturbed heat flux at the drill sites. This study shows that knowledge of the pattern of drilling operations with alternating phases of drilling/flushing and drill string handling is crucial for comparing temperatures measured during logging while tripping and simulated temperatures.

Early to middle Miocene ice sheet dynamics in the westernmost Ross Sea (Antarctica): Regional correlations

The present-day morpho-stratigraphy of the Ross Sea is the result of Cenozoic tectonic and cryospheric events, and constitutes a key record of Antarctica's cryospheric evolution. An enduring problem in interpreting this record in a broader regional context is that the correlation between eastern and western Ross Sea stratigraphy has remained uncertain due to the limited number of drill sites. We correlate the glacial-related features observed on a dense network of seismic reflection profiles in McMurdo Sound with those identified in the Nordenskjöld and Drygalski Basins, as well as the basins farther east in the central Ross Sea. We present an improved correlation of the regional patterns of early to middle Miocene ice-sheet variance across the Ross Sea constrained by new evaluation of seismic facies and age models from one site recovered by the Antarctic Drilling Project (ANDRILL) in the southwestern most part of McMurdo Sound. We also integrate this correlation with the recently published seismic framework in the central Ross Sea. The formation of U-shaped valleys during the early Miocene in McMurdo Sound, together with prograding sedimentary wedges in the western-most basins, and the central Ross Sea, suggest two major phases of overall advance of a marine-terminating ice sheet between ~18 Ma and ~17.4 Ma. Widespread formation of turbiditic channel-levee systems in McMurdo Sound and rapid sediment deposition in Nordernskjöld Basin point to subsequent ice-sheet retreat between ~17.4 Ma and ~15.8 Ma, coinciding with the onset of the Miocene Climate Optimum (MCO; ~17–14.5 Ma). However, the carving of troughs and formation of irregular morphologic features suggest that an extensive ice sheet still remained along the western Ross margin at ~17.4 Ma and a brief episode of ice-sheet advance occurred at ~16.8 Ma in the earliest interval of the MCO. Subsequent marine-based ice sheet advance during the Middle Miocene Climate Transition (MMCT, ~14.0–13.8 Ma) is indicated by widespread erosional features. Our results reconcile the semi-continouous seismic and drill core stratigraphy of the offshore Ross Sea continental shelf with inferences of ice sheet dynamics from continuous far-field deep sea and sea level records, as well as the highly discontinous (and heavily debated) onshore records of pre-MMCT glaciation and aridification of the Transantarctic Mountains at 14 Ma. • Core-log-seismic correlation allows regional correlation of the Ross Sea record • 2 major advances of marine-terminating ice sheet occurred between 18 and 17.4 Ma • Ice sheet retreated at the onset of the Miocene Climate Optimum • Short-term ice-sheet advance occurred at ~16.8 Ma • Widespread marine-based ice sheet correlates to the Miocene Climate Transition

Correlation of soil microbiome with crude oil contamination drives detection of hydrocarbon degrading genes which are independent to quantity and type of contaminants

The impacts of crude oil contamination on soil microbial populations were explored in seven different polluted areas near oil and gas drilling sites and refineries of Assam, India. Using high-throughput sequencing techniques, the functional genes and metabolic pathways involved in the bioconversion of crude oil contaminants by the indigenous microbial community were explored. Total petroleum hydrocarbon (TPH) concentrations in soil samples ranged from 1109.47 to 75,725.33 mg/kg, while total polyaromatic hydrocarbon (PAH) concentrations ranged from 0.780 to 560.05 mg/kg. Pyrene, benzo[a]anthracene, naphthalene, phenanthrene, and anthracene had greater quantities than the maximum permitted limits, suggesting a greater ecological risk, in comparison to other polyaromatic hydrocarbons. According to the metagenomic data analysis, the bacterial phyla Proteobacteria, Actinobacteria, Acidobacteria, and Bacteroides were the most prevalent among all polluted areas. The most prominent hydrocarbon degraders in the contaminated sites included Burkholderia, Mycobacterium, Polaromonas, and Pseudomonas. However, the kinds of pollutants and their concentrations did not correlate with the abundances of respective degrading genes for all polluted locations, as some of the sites with little to low PAH contamination had significant abundances of corresponding functional genes for degradation. Thus, the findings of this study imply that the microbiome of hydrocarbon-contaminated areas, which are biologically involved in the degradation process, has various genes, operons and catabolic pathways that are independent of the presence of a specific kind of contaminant.

Control of directional long borehole on gas drainage and optimal design: Case study

The Directional Long Borehole (DLB) technique, which has the benefits of low construction costs and high drainage efficiency, will be extensively used in future mining operations for gas drainage and utilization. Choosing the right borehole parameter is critical for improving the drilling stability and drainage efficiency of DLB. This paper begins with research on the gas migration and enrichment law in the mining-induced fissure, and proposes a gas migration channel zoning model. Furthermore, the dynamic process of gas migration in fissure fields is analyzed, as well as the key borehole parameters are identified. The optimal DLB parameters are eventually addressed and presented for the 2205 working face via combined UDEC and COMSOL. Research indicates that: (1) The mining-induced fissure serves as a channel for gas flow, and presents different pore morphology in space, forming a gas migration channel zoning model. The model's permeability increases initially and then decreases from the gob upward, increasing in an O-ring outward diffusion from the gob's center, it can be represented as a rectangular ladder platform with 15 zones. (2) Gas goes through a dynamic process of state change during drainage that involves adsorption/desorption, diffusion, and seepage. The main factors that affect this process are negative pressure, borehole length, borehole diameter, and the location of the borehole in the fissure zone. (3) The optimal parameters of DLB in the 2205 working face, are 2 drill sites, each with 5 sets of 500 m long boreholes, with a diameter of 133 mm, and a pumping negative pressure of 13 kPa, and placed in a layer height of 22 m. DLB provides benefits over the high-level suction highway in terms of construction cost, drainage effectiveness, and timeliness. The findings can be used to guide the design of DLB, enhance gas energy utilization, and prevent gas disasters.

9 Complications of Bone-Anchored Hearing Aids (BAHA) in Patients

Abstract Aim BAHA implants utilise bone conduction to treat hearing loss. The aim of the study was to understand the complication rate of patients receiving the implant compared to other studies and to identify any causative factor. Recommendations would therefore be made to reduce these complications. Methodology A retrospective cohort study was undertaken on 134 patients who received a BAHA implant performed by a single surgeon at Salford Royal NHS Foundation Trust between 01/01/2016 to 31/12/2018. Data collected identified complications of the surgery, whether or not the abutment was still in situ and whether the patient had any comorbidities or history of smoking Results 33.6% of the patients had no complications after surgery with the remaining 66.4% having at least one complication. BAHA connect devices had a 67.2% complication rate, attract devices had a 33% complication rate. 13.6% of BAHAs were extruded. There was no positive correlation between either smoking or diabetes and poorer complication rate. Conclusion Implant extrusion can be prevented with irrigation cooling of the drill site. Immobilisation of the implant, proper wound care with brushing and using an Allevyn Acticoat 7 wound dressing improves outcomes. Attract systems have fewer complications rates so must be maximised where appropriate.

Potassium-isotope variations of marine sediments adjacent to the Izu-Bonin Trench and Nankai Trough

Characterizing the K-isotope compositions of marine sediments is a necessary step to using this novel isotope system to investigate K cycling both in the ocean system and in subduction zones. Here we report data for 70+ samples in order to characterize the K-isotope compositions of deep-sea sediments for two drill sites in the western Pacific: (1) IODP Site C0011 adjacent to the Nankai Trough and Southwest Japan arc and (2) Site 1149 adjacent to the Izu-Bonin trench and arc. Variation in δ41K at both sites is mostly subtle, reflecting a consistently strong contribution of K from sources that have δ41K similar to the upper continental crust (UCC). Yet, in detail, the mean δ41K at both sites is about 0.05–0.10 ‰ lower than a recently proposed best estimate for UCC (δ41K = −0.44 ‰). We infer that the slightly low mean δ41K values relative to UCC are likely caused by secondary processes acting on the volcanogenic component of the sediments, though chemical weathering of (non-volcanogenic) terrigenous materials may also play a role. We measured a very low δ41K value (−1.33 ± 0.04 ‰) for one discrete ash layer at Site C0011, so volcanoclastic materials may lower the δ41K values of the bulk sediments, despite only accounting for a small fraction of the K in the sediments. Correlations between δ41K, Cr/Al, and K/Al in the upper sediments of Site 1149 were used to investigate mixing between volcanic ash and terrigenous materials. This approach indicates that mixing of isotopically light volcanic ash (with δ41K about −0.75 ‰) and terrigenous materials (about −0.46 ‰) can account for the observed variation in δ41K values in these sediments. In addition, we observe that at Site C0011 K isotopes exhibit a shift (by ~0.08 ‰) at ~250 m below the seafloor from UCC-like compositions in the upper sediments to slightly lighter compositions in the lower sediments. This shift in δ41K coincides with an abrupt change in certain physical properties (porosity and cementation) of the sediments that may relate to the extent of weathering/degradation of the dispersed volcaniclastics, with more extensively weathered materials present in the lower sediments. Finally, we find evidence for variable admixture of a high δ41K silicic volcanic ash in the lowermost sediments at Site C0011, supporting the view that heterogeneous volcaniclastics can give rise to significant δ41K variations in marine sediments.

Upper crustal structure at the KTB drilling site from ambient noise tomography

Summary In this study, we show results from ambient noise tomography around the KTB (Kontinentales Tiefbohrprogramm der Bundesrepublik Deutschland), a continental deep drilling site located at the western edge of the Bohemian Massif, within the Variscan belt of Europe. At the KTB site, crustal rocks have been drilled down to 9 km depth. Before the drilling activity started, several active seismic surveys had been performed to explore its surroundings during the 1980s and early 1990s, in the frame of an extensive exploration of the area aimed at unravelling the characteristics of the continental lower crust that is exposed at surface in this location. Despite the exploration campaigns held at and around the KTB drilling site, there are important targets that are worth further investigation; these are related in particular to the obduction of lower crustal units to the surface, and to the mechanism of orogenic processes in general. Here we present a new 3-D shear wave velocity model of the area from cross-correlations of ambient seismic noise. The model is obtained by a unique data set composed of 2 yr of continuous data recorded at nine 3-component temporary stations (installed from July 2012 to July 2014) located on top and around the drilling site, and together with the data from 19 permanent stations throughout the region. This paper is focusing on the upper crustal layers, and we show velocity variations at short scales that correlate well with known geological structures in the region of the KTB site, at the surface and at depth. These are used to discuss features that are less well-resolved at present.

Shallow Regolith Structure and Obstructions Detected by Lunar Regolith Penetrating Radar at Chang’E-5 Drilling Site

This work analyzes the observations from the Lunar Regolith Penetrating Radar (LRPR) onboard Chang’E-5 to reconstruct the subsurface structure of the regolith under the lander at the drilling site. This is the first stationary Ground-Penetrating Radar (GPR) array to operate on the Moon. Imaging results of pre-drilling and post-drilling measurements show that the thickness of local regolith is larger than 2 m. Within the LRPR’s detection range, we do not find any continuous layer. Instead, irregular, high-density zones are identified in the regolith. Two of these zones are on the drilling trajectory at ~30 cm and ~70 cm, consistent with the recorded drilling process. We speculate a rock fragment from the deeper, high-density zone obstructed the drill, which led to an early termination of the drilling. Based on our interpretation of subsurface structure, we modeled the LRPR echoes using a finite-difference time-domain method. The same imaging algorithm was also applied to the simulation data. The modeled data verify our inference of the regolith structure under the lander.

From ice core to ground-penetrating radar: representativeness of SMB at three ice rises along the Princess Ragnhild Coast, East Antarctica

AbstractThe future contributions of the Antarctic Ice Sheet to sea level rise will depend on the evolution of its surface mass balance (SMB), which could amplify/dampen mass losses increasingly observed at the ice sheet's edge. In situ constraints of SMB over annual-to-decadal timescales consist mostly of firn/ice cores that have a surface footprint $\sim$cm$^{2}$. SMB constraints also come from climate models, which have a higher temporal resolution but a larger surface footprint of several km$^{2}$. We use ice-penetrating radar data to obtain an intermediate spatial and temporal resolution SMB record over three ice rises along the Princess Ragnhild Coast. The co-located ice cores allow us to obtain absolute radar-derived SMB rates at a multi-annual-to-decadal temporal resolution. By comparing the ice core SMB measurements and the radar-derived SMB records, we determine that pointwise measurements of SMB are representative of a small surface area, $\sim 200-500$ m radius extending from the ice core drill site for the ice rises studied here, and that the pointwise measurements are systematically 7–15 cm w.e. a$^{-1}$ lower than the mean SMB value calculated for the whole ice rises. However, ice core records are representative of an entire ice rise's temporal variability at the temporal resolution examined.

On the consolidation state of sediments from the accretionary prism offshore Vancouver Island, North Cascadia Margin

Sediment geotechnical properties are an important component of geohazard analyses and studies on submarine slope failures on continental margins. The northern Cascadia margin is a region of repeated subduction earthquakes and related geohazards including devastating tsunamis. Despite several drilling campaigns at this margin mostly for gas hydrate studies, sediment geotechnical properties are lacking to date. We therefore investigated a set of 20 half-round samples from four drill sites of Integrated Ocean Drilling Program (IODP) Expedition 311 along a margin-perpendicular transect. Samples were analysed for Atterberg properties (liquid limit, plasticity limit, plasticity index) and consolidation state (pre-consolidation stress, over-consolidation ratio, initial void ratio and compression index). Results of these parameters are in good agreement with similar studies at the southern Cascadia margin from Ocean Drilling Program (ODP) Leg 204 and are regarded robust, despite the long time-span between sample recovery in 2005 and our analyses. Individual results are interpreted at each of the drill sites and reflect the overall tectonic state of the location within the accretionary prism. An interplay of site-specific tectonic forcing, including thrust faulting, uplift, folding, and erosion appears to govern the depth-dependent consolidation state of the sediments.