Digital Festningen: a dark season journey through 300 million years of geological evolution

Abstract

The renowned Festningen section in the outer part of Isfjorden, western Spitsbergen, offers a c. 7 km long nearly continuous stratigraphic section of Lower Carboniferous to Cenozoic strata. Tectonic deformation associated with the Paleogene West-Spitsbergen-Fold-and-Thrust belt tilted the strata to near-vertical, allowing easy access to the section along the shoreline. The Festningen section is a regionally important stratigraphic reference profile, and thus a key locality for any geologist visiting Svalbard. The lithology variations, dinosaur footprints, as well as the many fossil groups, record more than 300 million years of continental drift, climate change, and sea level variations. As such, the Festningen section is the only protected geotope in Svalbard, covering an area of c. 17 km2. The first detailed geological cross-section of the Festningen profile was published by Hoel & Orvin (1937), while a revised open-access field guide was compiled by Mørk & Grundvåg (2020).
In this contribution, we focus on presenting a digital outcrop model of this stratigraphic key section, acquired using a UAV (Mavic 2 Pro, 20MP Hasselblad camera). The main objective of this field campaign was to digitize the entire Festningen section, using structure-from-motion photogrammetry. During acquisition, the maximum drone speed was set to 1 meter/second (i.e., “tripod mode”), and photographs were taken automatically at set time intervals (e.g. 1 photo every 5 seconds ≈ meters). In total, 3757 photographs were aligned using photogrammetric processing steps, including sparse and dense cloud generation, point confidence calculations and confidence-based trimming (3% confidence), meshing and texturing, that resulted in a 7 km long digital outcrop model. Georeferencing relied on the drone-mounted GPS, and the resulting digital outcrop model is well aligned with the regional terrain model (estimated total camera error: 4.12 m). The digital outcrop model offers a pixel resolution of 7.27 mm/pixel and covers 0.67 km2. The Festningen model will be presented for the first time at the Winter Meeting, and subsequently available online for anyone through the Svalbox.no geoscience data platform.

Full text

Digital Festningen: a dark season journey through 300 million years of
geological evolution

Kim Senger1,6, Peter Betlem1,2, Thomas Birchall1,2,6, Sten-Andreas Grundvåg3,6, Atle Mørk4, Sverre Planke2,5,6,
Aleksandra Smyrak-Sikora1,6, Lilith Kuckero1
1 Department of Arctic Geology, The University Centre in Svalbard; kim.senger@unis.no;
Thomas.birchall@unis.no; aleksandras@unis.no; Peter.Betlem@unis.no
2 Department of Geosciences, The University of Oslo
3 Department of Geosciences, University of Tromsø - The Arctic University of Norway; sten-
andreas.grundvag@uit.no
4 Department of Geoscience and Petroleum, NTNU, Trondheim; atle.mork@ntnu.no
5 Volcanic Basin Petroleum Research (VBPR), Oslo; planke@vbpr.no
6 The Research Centre for Arctic Petroleum Exploration (ARCEx)

The renowned Festningen section in the outer part of Isfjorden, western Spitsbergen, offers a c. 7 km long
nearly continuous stratigraphic section of Lower Carboniferous to Cenozoic strata. Tectonic deformation
associated with the Paleogene West-Spitsbergen-Fold-and-Thrust belt tilted the strata to near-vertical, allowing
easy access to the section along the shoreline. The Festningen section is a regionally important stratigraphic
reference profile, and thus a key locality for any geologist visiting Svalbard. The lithology variations, dinosaur
footprints, as well as the many fossil groups, record more than 300 million years of continental drift, climate
change, and sea level variations. As such, the Festningen section is the only protected geotope in Svalbard,
covering an area of c. 17 km2. The first detailed geological cross-section of the Festningen profile was published
by Hoel & Orvin (1937), while a revised open-access field guide was compiled by Mørk & Grundvåg (2020).
In this contribution, we focus on presenting a digital outcrop model of this stratigraphic key section, acquired
using a UAV (Mavic 2 Pro, 20MP Hasselblad camera). The main objective of this field campaign was to
digitize the entire Festningen section, using structure-from-motion photogrammetry. During acquisition, the
maximum drone speed was set to 1 meter/second (i.e., “tripod mode”), and photographs were taken
automatically at set time intervals (e.g. 1 photo every 5 seconds ≈ meters). In total, 3757 photographs were
aligned using photogrammetric processing steps, including sparse and dense cloud generation, point confidence
calculations and confidence-based trimming (3% confidence), meshing and texturing, that resulted in a 7 km
long digital outcrop model. Georeferencing relied on the drone-mounted GPS, and the resulting digital outcrop
model is well aligned with the regional terrain model (estimated total camera error: 4.12 m). The digital outcrop
model offers a pixel resolution of 7.27 mm/pixel and covers 0.67 km2. The Festningen model will be presented
for the first time at the Winter Meeting, and subsequently available online for anyone through the Svalbox.no
geoscience data platform.
References:
Hoel, A. and Orvin, K. A.. 1937. Das Festungsprofil auf Spitzbergen Karbon-Kreide. I. Vermessungsresultate.
Oslo 1937. - Skr. om Svalbard og Ishavet. Nr. 18. 59 pp
Mørk, A. and Grundvåg, S. A. 2020. Festningen: A 300-million-year journey through shoreline exposures of the
Carboniferous and Mesozoic in 7 kilometers. Geological guides 7-2020, Geological Society of Norway.
Available at: https://www.geologi.no/organsisasjon/om-ngf/nyheter-ngf/item/1080-geoguide7