The European Plate Observing System (EPOS, www.epos-eu.org) is a multidisciplinary pan-European research infrastructure for solid Earth science. It integrates a series of domain-specific service hubs (Thematic Core Service, TCS) such as the Geological Information and Modelling, which provides access to data, data products and services on European boreholes, geological maps, mineral occurrences, mines and 3D models. TCS GIM services are hosted by a group of European Geological Surveys and a couple of national research organizations. This paper presents novel data discovery and integration, facilitated using borehole logging information with on-demand web services to produce 3D geological structures. This domain interoperability across EPOS was created for the purpose of research, but it is also highly relevant for the response to societal grand challenges such as natural hazards and climate change. European and international interoperability implementation frameworks are well described and used (e.g., INSPIRE, ISO, OGC, and IUGS/CGI). It can be difficult for data providers to deploy web services that support the full semantic data definition (e.g., OGC Complex Feature) to expose several millions of geological entities through web-enabled data portals as required by pan-European projects. The TCS GIM group implemented and innovatively extended two standardized descriptions, i.e. GeoSciML-Lite and EarthResourceML-Lite, with an important reuse of content from Linked Data Registries. This approach was applied to design and implement the European Borehole Index and associated web services (View-WMS and Discovery-WFS), extended to 3D models, geological maps as well as mineral occurrences and mines. Results presented here apply the Linked Data approach ensuring optimal semantic description and enriching the data graphs, with complex descriptions and contents. In this way, it is now possible to traverse from one Borehole Index instance to linked richer information such as the borehole geological log, groundwater levels, rock sample description, analyses, etc. All this detailed information is served following international interoperability standards (Observations & Measurements, GroundWaterML 2.0, GeoSciML4, amongst others).
ABSTRACT Detrital zircon provenance studies of Precambrian metasedimentary rocks in Wedel Jarlsberg Land and Sørkapp Land, Svalbard’s Southwestern Caledonian Basement Province, were conducted to evaluate local stratigraphic correlations and the role of long-distance strike-slip displacements in assembling the basement of the Arctic Caledonides. The detrital zircon U-Pb age spectra of the late Mesoproterozoic to Neoproterozoic metasediments revealed mainly Mesoproterozoic to Paleoproterozoic age signatures characteristic for a Grenville–Sveconorwegian orogen provenance. These results confirmed a stratigraphic correlation between basement units of southern Sørkapp Land and the Isbjørnhamna Group of Wedel Jarlsberg Land and suggest relocation of the tectonic boundary between the Eimfjellet Complex and the Isbjørnhamna Group above the Eimfjellbreane Formation. Moreover, the results support the Vimsodden Kosibapasset Shear Zone (VKZ) as a major tectonic boundary and highlight the inhomogeneity in the Southwestern Caledonian Basement Province. The detrital zircon age signatures south of the VKZ bear similarities with coeval metasediments of the Northwestern Caledonian Basement Province of Svalbard and other localities in the Greenland and Scandinavian Caledonides. In contrast, the detrital zircon age spectra north of the VKZ are comparable with the high Arctic Neoproterozoic sediments of Baltican affinity. In conjunction with previous studies, the results suggest that the basement units may continue across the traditional boundaries of the Svalbard’s Caledonian basement provinces.
The Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project studies mountain building processes in a major mid-Paleozoic orogen in western Scandinavia and its comparison with modern analogues (i.e. Alpine-Himalaya mountain belt) by two boreholes (COSC-1 and COSC-2) in Jämtland, central Sweden. The COSC-2 borehole was drilled from mid-April to early August 2020 with nearly 100% core recovery and reached a total depth of 2276m. COSC-2 drilling encountered, from top to bottom, 780m of turbiditic greywackes, about 50m of a sheared black shale unit followed by sandstones and conglomerates in a turbiditic background sedimentation to about 1250m. Ignimbrites and volcanic porphyries with sporadic intervals of doleritic intrusions dominate the deeper stratigraphic sequence (from 1250 m to the bottom depth). To acquire the petrophysical properties of the rocks, three downhole logging campaigns were carried out by Lund University and the ICDP Operational Support Group from 2020 to 2022. In this study, high-resolution acoustic images of the open borehole below 100m were analysed to identify and interpret past and present tectonic features. Two main categories were detected on the image log: geological structures (i.e. foliation, fractures) and stress-induced alteration of the borehole (i.e. breakout). The latter allows the orientation of the present-day stress field to be constrained. For breakout identification, both manual and automatic peak-detection was deployed. In the manual interpretation, the breakout azimuth is assumed to be the center of each breakout, whereas in the automatic selection, the breakout azimuth is set to the average location of the peak when the minimum location in the filtered amplitude and the maximum location in the filtered radius image logs are close (difference less than 25°), based on the assumption that the breakout shape is symmetric. In the COSC-2 borehole, the breakouts were mainly concentrated between 1600m and 1897m. Only a few and poorly-developed breakouts were manually identified outside of dolerite intrusions and gabbroid rocks. Based on the manual approach, about 104 borehole breakouts were identified for a total length of 93m with an average orientation of the maximum horizontal principal stress (SH) of 160°. Automatic peaking detected 216 breakouts for a total length of 43m with an average SH-orientation of 161°. A high correlation was found between these two methods, and the SH-orientation remains fairly constant among the borehole. We also compared the results of COSC-2 with those of the 2496m deep COSC-1 borehole, located about 20 km to the northwest of COSC-2: 1. the orientation in the two boreholes diverges by about 33° (SH orientation of COSC-1 is 127°), 2. in COSC-2 the breakouts are well developed in width and length, and 3. they show a much greater cumulative length (93m compared to 22m in COSC-1). The paucity of breakouts in the COSC-1 well has been attributed to the type of rocks (metamorphic and crystalline) that are generally elastically stiff and have high mechanical strength, which inhibits the formation of breakouts. In contrast, in COSC-2, the dolerite and gabbroid rocks seem more prone to stress-induced enlargements.
In connection with the Collisional Orogeny in the Scandinavian Caledonides (COSC) project, broad-band magnetotelluric (MT) data were acquired at 78 stations along a recent ca. 55-km-long NW–SE directed reflection seismic profile (referred to as the COSC Seismic Profile; CSP), with the eastern end located ∼30 km to the west of the orogenic Caledonian front. The MT component of the project aims at (i) delineating the highly conductive (∼0.1 Ω ⋅ m) alum shales that are associated with an underlying main décollement and (ii) calibrating the MT model to borehole logs. Strike and distortion analyses of the MT data show a 3-D structure in the western 10 km of the profile around the 2.5 km deep COSC-1 borehole (IGSN: ICDP5054EHW1001) and a preferred strike angle of N34°E in the central and eastern parts of the profile. 2-D modelling of MT impedances was tested using different inversion schemes and parameters. To adjust the resistivity structure locally around the borehole, resistivity logging data from COSC-1 were successfully employed as prior constraints in the 2-D MT inversions. Compared with the CSP, the model inverted from the determinant impedances shows the highest level of structural similarity. A shallow resistor (>1000 Ω ⋅ m) in the top 2–3 km depth underneath the western most 10 km of the profile around COSC-1 corresponds to a zone of high seismic reflectivity, and a boundary at less than 1 km depth where the resistivity decreases rapidly from >100 to <1 Ω ⋅ m in the central and eastern parts of the profile coincides with the first seismic reflections. The depth to this boundary is well constrained as shown by 1-D inversions of the MT data from five selected sites and it decreases towards the Caledonian front in the east. Underneath the easternmost part of the profile, the MT data show evidence of a second deeper conductor (resistivity <1 Ω ⋅ m) at >3 km depth. Based upon the COSC-1 borehole logs, the CSP reflection seismic image, and the surface geologic map, the MT resistivity models were interpreted geologically. In the vicinity of COSC-1, the resistor down to 2–3 km depth pertains to the metamorphic Middle Allochthon. The up to 1000-m-thick shallow resistor in the central and eastern parts of the profile is interpreted to overly an imbricated unit at the bottom of the Lower Allochthon that includes the alum shales. In the MT resistivity model, the 300–500 m thick imbricated unit masks the main Caledonian décollement at its bottom. A second possible interpretation, though not favoured here, is that the décollement occurs along a much deeper seismic reflection shallowing from 4.5 km depth in the west to ∼600 m depth in the east. An additional borehole (COSC-2) is planned to penetrate the Lower Allochthon and the main décollement surface in the central part of the profile and can provide information to overcome this interpretational ambiguity. Using a synthetic study, we evaluate how resistivity logs from COSC-2 can improve the 2-D inversion model.
Abstract. The Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project focuses on mountain building processes in a major mid-Palaeozoic orogen in western Scandinavia and its comparison with modern analogues. The project investigates the subduction-generated Seve Nape Complex. These in part under ultra-high-pressure conditions metamorphosed outer continental margin and continent–ocean transition zone assemblages were emplaced onto the Baltoscandian platform and there influenced the underlying allochthons and the basement. COSC-1 is the first of two ca. 2.5 km deep, fully cored drill holes located in the vicinity of the abandoned Fröå mine, close to the town of Åre in Jämtland, central Sweden. It sampled a thick section of the lower part of the Seve Complex and was planned to penetrate its basal thrust zone into the underlying lower-grade metamorphosed allochthon. The drill hole reached a depth of 2495.8 m and nearly 100 % core recovery was achieved. Although planning was based on existing geological mapping and new high-resolution seismic surveys, the drilling resulted in some surprises: the Lower Seve Nappe proved to be composed of rather homogenous gneisses, with only subordinate mafic bodies, and its basal thrust zone was unexpectedly thick (> 800 m). The drill hole did not penetrate the bottom of the thrust zone. However, lower-grade metasedimentary rocks were encountered in the lowermost part of the drill hole together with garnetiferous mylonites tens of metres thick. The tectonostratigraphic position is still unclear, and geological and geophysical interpretations are under revision. The compact gneisses host only eight fluid conducting zones of limited transmissivity between 300 m and total depth. Downhole measurements suggest an uncorrected average geothermal gradient of ~ 20 °C km−1. This paper summarizes the operations and preliminary results from COSC-1 (ICDP 5054-1-A), drilled from early May to late August 2014, and is complemented by a detailed operational report and the data repository.
