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Geologisk reiseblog fra Øst Grønland

Reiseblogg fra den arktiske sommeren: geologisk feltarbeid på Østgrønland

Denne sommeren reiste et team med strukturgeologer og sedimentologer fra UiB og UiT - Norges Arktiske Universitet over Nord-Atlanteren for å besøke Wollaston Forland på Nordøst-Grønland. Grunnen? For å studere den strukturelle, avsetningsmessige og diagenetiske historien til et rift-basseng med dypvannsavsetninger fra juratiden.

Neste
Grønnland landskap
Constable Point (CNP), not the place to spend a long weekend unless you are on the run from the law. Don’t let the picturesque look of the place fool you. The next picture tells the truth.
Foto:
Sten-Andreas Grundvåg
1/19
Greenland road
M&M’s (mud and mosquitos), old storage buildings, fuel tanks and abandoned rusty machines pretty much sums up CNP.
Foto:
Sten-Andreas Grundvåg
2/19
Greenland CNP
At least we got to practice drone flying while we waited for better weather up north. CNP in the background. The drone turned out to be a great asset to the entire project when we finally got to Lindeman Fiord almost a week later.
Foto:
Sten-Andreas Grundvåg
3/19
Airplane over Greenland
No professor, this is not a school bus, can you please sit down and let the pilots do their job?’. Finally on our way from CNP towards Lindeman Fiord. Little did we know that two hours later we would end up in the Danish research outpost Zackenberg.
Foto:
Sten-Andreas Grundvåg
4/19
Snow view from airplane over Greenland
The promissed land. Well, somewhere under the snow. With the fiords still covered by sea ice, we started to wildy speculate amongst ourselves. Would it be possible to land in Lindeman Fiord? How many polar bears can fit on just one of those pieces of ice? Would the polar bears let us alone and simply look upon us as way too skinny seals? How much butter did we bring? The questions and worries were many, but it would later turn out that most of these were irrational.
Foto:
Sten-Andreas Grundvåg
5/19
Greenland desert
Welcome to Mars. If you ever have wondered how a Danish Polar station looks like, here is the answer. Zackenberg have their own Twitter account, so if you want to see what they are doing have a look at https://twitter.com/zero74n.
Foto:
Sten-Andreas Grundvåg
6/19
Snow at Greenland
Maybe not a very impressive piece of outcrop, but at least it was enough to increase our moral and satify our urge of getting out to do something useful as a team. View northward up the Lindeman Valley just some 20 km south of our planned camp site in Lindeman Fiord.
Foto:
Sten-Andreas Grundvåg
7/19
Sledge at Greenland
Lindeman Fiord plane spotting club. After nearly a week of travelling and waiting, we eventually managed to get to Lindeman Fiord. Here we have unloaded the Twin Otter and are just about to wave farewell to the pilots.
Foto:
Sten-Andreas Grundvåg
8/19
Boot camp at Greenland
Base camp (BC) in the making. The lavvo served as our common kitchen and living room.
Foto:
Sten-Andreas Grundvåg
9/19
Boot camp at Greenland
Lindeman Fiord BC in all its glory. The island of Kuhn Ø in the background.
Foto:
Atle Rotevatn
10/19
River at Greenland
Arctic filedwork is far from a walk in the park. Here Prof. Atle Rotevatn (aka Prof. Longlegs) is crossing a river on his way to the Dombjerg Fault.
Foto:
Sten-Andreas Grundvåg
11/19
Rest at mountain in Greenland
Lunch in the field. Syn-rift conglomerates serving as a shelter from the the cold glacier winds down the valley.
Foto:
Sten-Andreas Grundvåg
12/19
muskox at Greenland
A small family of muskox lived closed by our camp, and many times we crossed each others paths in the mountains.
Foto:
Sten-Andreas Grundvåg
13/19
Fieldwork in mountains at Greenalnd
Gijs Henstra looking back towards one of the main outcrops that we digitized (see video link above).
Foto:
Sten-Andreas Grundvåg
14/19
Sampling in a turbidite sandstone at Greenland
Eric Salomon (left) and Thomas Berg Kristensen (right) samples a vein in a turbidite sandstone.
Foto:
Sten-Andreas Grundvåg
15/19
Wathering of the turbidite sandstones creates a mesmerising landscape out of this world
Weathering of the turbidite sandstones creates a mesmerising landscape out of this World.
Foto:
Sten-Andreas Grundvåg
16/19
Atle Rotevatn (left) and Gijs Henstra (right) carefully maneuvering the drone along the outcrop.
Atle Rotevatn (left) and Gijs Henstra (right) carefully maneuvering the drone along the outcrop.
Foto:
Eric Salomon
17/19
The whole team tramping through a snow packed valley towards a promising outcrop.
The whole team tramping through a snow packed valley towards a promising outcrop.
Foto:
Eric Salomon
18/19
Gijs Henstra (center), Thomas Berg Kristensen (left) and Sten-Andreas Grundvåg (right) inspecting coal material.
Gijs Henstra (center), Thomas Berg Kristensen (left) and Sten-Andreas Grundvåg (right) inspecting coal material.
Foto:
Eric Salomon
19/19
Tilbake

In the heat of the Arctic summer – geological travel blog from East Greenland
Text and photos: Sten-Andreas Grundvåg (UiT), with contributions from Dr. Eric Salomon, Dr. Gijs Henstra, Dr. Thomas Berg Kristensen, and Prof. Atle Rotevatn (all UiB)

Greenland. Close your eyes and think of it for a moment. Anticipation. Breathe in the cold Arctic air and listen to the howling wind as it whispers into your ears. The call of the wild. To most people Greenland is associated with glaciers and icebergs, deep fiords, muskox and polar bears. For a good reason. The majority of Greenland is covered all-year-round by a vast ice shield, up to several thousand meters thick, and the island hosts the World’s largest national park. However, most of the coastlines are practically devoid of ice and snow during the two-three months of Arctic summer. To geologists, the short and intense Arctic summer is a blessing. That is at least how it should be in theory.

Looking out the window from our Twin Otter propeller plane revealed a different story. Despite being early August, the past weeks of heat in Europe had translated to a cold summer in East Greenland: sea ice still covered the fiords, and many mountains and valleys were peacefully hiding under a white coat. ‘Will we be able to land in Lindeman Fiord?’ Just one of the many questions I asked to myself while looking out the window in despair. Since we had left Reykjavik in Iceland some days earlier, we had been stuck at the airstrip at Constable Point (CNP) waiting on better flight conditions up north. Ironically, the sun was shining at CNP, transforming the runway in to a dusty desert-like habitat full of thriving mosquitos. What a great feeling to finally be on our way. Northbound. To our surprise and great luck, the amount of snow and the extent of the sea ice cover far below us, slowly diminished as the small aircraft proceeded northward. Of less fortune was the increasing amount of fog protruding from the ocean into the narrow fiords. Thus, instead of Lindeman Fiord, the pilots chose a much safer alternative and left us at the Danish research station in Zackenberg, 20–30 km south of our planned final destination. More waiting and waste of valuable field days ahead. Despite the Danes treating us friendly and feeding us superb supper every night, we struggled to settle in. One day we found some pieces of outcrop some 10 swampy kilometers north of the station. The effect of the discovery was just as our commander (read. Prof. Rotevatn) had hoped. After nearly a week on hold, the team was on the edge, but eventually doing something intellectually satisfying together increased the moral. Not only did the crumbly rocks strengthen our desire to get to Lindeman Fiord, but it also extinguished a rising mutiny (with four team members planning an escape from Zackenberg with a pulkka mounted on a sea-ice raft). The next day we got what we hoped for: sun, no fog, and a Twin Otter with the finest Icelandic pilots there is. After one quick flyby and some hardcore action movie-style landing maneuvers, we were safely on the ground on the “runway” in Lindeman Fiord, Wollaston Forland. To call this 100 m long and 40 m wide gravel terrace a runway is an exaggeration at best (all honor to the skilled and brave pilots). Nonetheless, this terrace would serve as our home the next week or so. Establishing a basecamp for five persons always takes some time. First tents, then a lavvo, all secured with rocks, and finally a trip wire fence armed with pyro to alert us in case of visitors in the shape of white fury beasts. For some reasons unknown, the fence tended to attract more professors than polar bears. 

What is great about doing fieldwork in the high Arctic, with Wollaston Forland being no exception, is the unevenly distributed and sparse vegetation cover. Thus, when the snow melts, a fascinating landscape reveals itself. Alpine mountain peaks and nunataks, glacial valleys, and coastal cliffs, all full of excellently exposed rocks. In our study area in Lindeman Fiord, both Caledonian metamorphic basement rocks, as well as younger sedimentary rocks of predominantly Mesozoic age are present. What is unique with the study area is the Dombjerg Fault, a border fault that juxtaposes syn-rift deep-water hanging-wall clastics against a footwall of crystalline basement (Henstra et al., 2016; Kristensen et al., 2016; see ARCEx archive to download these papers). The fault belongs to a series of east-stepping faults that together define the western boundary of the East Greenland Fault system (Rotevatn et al., 2018). The exposed basin fill succession is also unique in that sense that it represent exhumed deep-marine gravity flow deposits, which accumulated during rifting and possibly rift climax (Henstra et al., 2016). Similar deposits form important reservoirs in several basins along the western margin of the Norwegian Continental Shelf. The aim of the trip was therefore two-fold: one group were to focus on the structural geology and structural diagenesis associated with the Dombjerg Fault, and the second to focus on the sedimentology and diagenesis of the syn-rift strata of the so-called Wollaston Forland Group. Because we also visited the same area back in 2014 during a more regional-scale study, we had pre-designed a detailed plan for which outcrops to visit and what specific sections to focus on. In regards to our late arrival as narrated above, this plan increased the effectiveness of the days we actually spent in the field. 

For example, the structural group managed to sample several tens of veins along the Dombjerg Fault itself, and documented the structural fabric within the basin clastics at selected outcrops in a proximal to distal transect normal to the fault. We hope that these samples may reveal the diagenetic history of the fault and basin and tell us what type of fluids that once used the fault and its associated fracture systems as their fairways. For the sedimentology part, the focus this time was to detail the architecture of the syn-rift gravity flow deposits at sub-seismic-scale resolution. In addition to sedimentary logs and rock samples for petrographic analyses, we also collected numerous photos, drone footage and videos so that we can make digital 3D models of our main outcrops. This means that we will be able to enjoy the outcrops in Wollaston Forland from our comfortable office chairs in the years to come. For a small teaser of one of our preliminary models (low resolution), have a look at this video made by Gijs Henstra: https://drive.google.com/file/d/1bh1vHOv9D40mRIF7I4awi5mW3U7AEGxY/view

PS! Just to let you know: we got safely back to Norway after ten fantastic days in the field. So look out for upcoming publications at www.arcex.no and other forums.

References:
Henstra, G., Grundvåg, S.-A., Johannessen, E.P., Kristensen, T., Midtkandal, I., Nystuen, J.-P., Rotevatn, A., Surlyk, F., Sæther, T. & Windelstad, J. (2016): Depositional processes and stratigraphic architecture within a coarse-grained rift-margin turbidite system: the Wollaston Forland Group, East Greenland. Marine and Petroleum Geology, Volume 76, September 2016, Pages 187–209. [http://dx.doi.org/10.1016/j.marpetgeo.2016.05.018] [intranet]

Kristensen, T.B., Rotevatn, A., Peacock, D.C.P., Henstra, G.A., Midtkandal, I. and Grundvåg, S.-A. (2016): Structure and flow properties of syn-rift border faults: the interplay between fault damage and fault-related chemical alteration (Dombjerg Fault, Wollaston Forland, NE Greenland). Journal of Structural Geology, Volume 92, November 2016, Pages 99-115. DOI: 10.1016/j.jsg.2016.09.012[intranet]

Rotevatn, A., Kristensen, T.B., Ksienzyk, A., Wemmer, K., Henstra, G.A., Midtkandal, I., Grundvåg, S.-A. & Andresen, A. (2018) Structural inheritance and rapid rift-length establishment in a multiphase rift: the East Greenland rift system and its Caledonian orogenic ancestry. Tectonics, 2018, Vol.37(6), p.1858-1875. DOI: 10.1029/2018TC005018 [intranet]