Preprints
https://doi.org/10.5194/essd-2022-143
https://doi.org/10.5194/essd-2022-143
 
26 Aug 2022
26 Aug 2022
Status: this preprint is currently under review for the journal ESSD.

High resolution digital outcrop model of faults and fractures in caprock shales, Konusdalen West, central Spitsbergen

Peter Betlem1,2, Thomas Birchall1, Gareth Lord1, Simon Oldfield3, Lise Nakken1,2,4, Kei Ogata5, and Kim Senger1 Peter Betlem et al.
  • 1Department of Arctic Geology, The University Centre in Svalbard, P.O. Box 156, N-9171 Longyearbyen, Svalbard, Norway
  • 2Department of Geosciences, University of Oslo, Sem Sælands vei 1, 0371 Oslo, Norway
  • 3Danish Offshore Technology Centre, Technical University of Denmark, Elektrovej, Building 375, 2800 Kgs. Lyngby, Denmark
  • 4Department of Earth Sciences, Royal Holloway, University of London, Egham Hill, Egham TW20 0EX, United Kingdom
  • 5Department of Earth, Environmental and Resource Sciences, Università degli Studi di Napoli Federico II, Via vicinale cupa Cintia 21, Complesso Universitario di Monte S. Angelo, Edificio L, 80126 Napoli, Italy

Abstract. Structure-from-motion (SfM) photogrammetry has become an important tool for quantitative characterisation of outcrops. Digital outcrop models (DOMs) allow for the mapping of stratigraphy and discontinuous structures like folds, faults and fractures from cm to km scale and provide solutions that are difficult to constrain through subsurface data alone. With pristine, treeless exposures, the outcropping strata in Svalbard, Arctic Norway, hold exceptional potential for analogue studies and are ideally suited for the acquisition of high-resolution DOMs. We here present the acquisition, processing and integration of the Konusdalen West digital model data set, comprising both DOM and derived digital terrain model (DTM) data. Dronebased image acquisition took place over two weeks in July and August 2020. Fifteen differential GNSS control points were used to georeference and quality assure the model, five of which functioning as reference checkpoints. SfM processing of 5512 acquired images resulted in high-confidence, cm-scale resolution point clouds, textured mesh (DOM), tiled model, orthomosaics, and a DTM. The confidence-filtered dense cloud features a median inter-point distance of 1.57 cm and has an average point density of 3824.9 points m-2. For the five checkpoints, the dense cloud features root mean square errors of 2.0 cm in X, 1.3 cm in Y, 5.2 cm in Z, and 5.7 cm in XYZ. Drops in point confidence and point density are mainly found in areas with reduced image densities, and on the backside of boulders. Increased confidences and densities are present along the western flank of the Konusdalen West outcrop, where a fault-fracture network in mudstone-dominated stata is best exposed and photographed most extensively.

The Konusdalen West DOM and DTM cover a 0.12 km2 area and span a 170 m elevation difference. The mean of the altitude of the checkpoints versus elevation of the dense cloud-derived DTM differed by less than a cm. The dense cloud-derived DTM closely matches an existing lower-resolution reference DTM of the area. The DOM covers the upper two-third of the mudstonedominated Late Jurassic-Early Cretaceous Agardhfjellet Formation. The Agardhfjellet Formation and its time-equivalents are regional cap rocks for CO2 sequestration and petroleum accumulations both on the offshore Barents Shelf and onshore Svalbard. Faults, formation members and established marker beds can be traced in the high-resolution model and have been used for the stratigraphic integration. Additional structural measurements and observations were taken in June 2021 to place the data in the geological context. Top and side-view orthomosaics feature maximum resolutions of 8 mm per pixel, enabling the mapping of fractures and other sub-cm features. The Konusdalen West digital model data set, together with the extensive drill cores through the same section near Longyearbyen, forms an ideal starting point for the generation of high-resolution, outcrop-truthed geomodels that are suitable for numerical modelling of fluid flow and appraisal of the regionally important caprock. Data described in this manuscript can be accessed at Norstore under https://doi.org/10.11582/2022.00027 (Betlem, 2022b).

Peter Betlem et al.

Status: open (until 21 Oct 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on essd-2022-143', David Tanner, 08 Sep 2022 reply
    • AC1: 'Reply on RC1', Peter Betlem, 23 Sep 2022 reply

Peter Betlem et al.

Data sets

Svalbox-DOM_2020-0039 Betlem, Peter https://doi.org/10.11582/2022.00027

Peter Betlem et al.

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Short summary
We present the digitization (i.e., textured outcrop and terrain models) of the Agardhfjellet Formation cliffs exposed in Konusdalen West, Svalbard. The formation forms the seal of a carbon capture site in Longyearbyen, where several boreholes cover the exposed interval. The outcrop data feature cm-scale accuracies, a maximum resolutions of 8 mm, and have been correlated with the boreholes through structural-stratigraphic annotations that form the basis for various numerical modelling scenarios.