GEUS Bulletin (Geological Survey of Denmark and Greenland)
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Validation of airborne and satellite altimetry data by Arctic Truck citizen science
No full textThe elevation of ice sheets changes due to climate change, and satellite altimetry is the preferred tool for measuring ice sheet-wide height changes. In situ validation is needed to ensure the quality of the observed elevation changes, but the cost often limits the amount of in situ data which can be collected. As more tourists are accessing the ice sheets, citizen science might provide in situ data in an environmentally friendly and cost-efficient way. Here, we investigate the opportunistic kinematic global positioning system (GPS) profiles across the Greenland ice sheet, collected by the American-Icelandic expedition on the Greenlandic icecap 2018. The collected GPS data are in good agreement with the widely used NASA’s Operation IceBridge Airborne LiDAR data measured within ± 10 days, with an average difference of 10.7 cm ± 11.7 cm. The main difference is attributed to changes in the compaction of the snow while driving and changes in the tires’ pressure. The kinematic GPS data are then compared with data from the European Space Agency’s CryoSat-2 mission. Here, an average bias of 92.3 cm ± 65.7 cm in the two records is observed between the spring CryoSat-2 and the truck GPS data obtained largely in the dry-snow zone. This suggests that the surface penetration of Ku-band radar on the Greenland ice sheet and the observed magnitude are consistent with the literature. Finally, we compared the 2018 GPS data to a profile obtained in 2005 near Kangerlussuaq, West Greenland. Here, the records show an average ice-elevation decrease of 9 m, with peaks at 26 m. These results show that the citizen science kinematic GPS data can provide high-resolution data necessary for the validation of satellite altimetry, with the added benefit of potential direct sampling properties of the surface and firn. Linking up with citizen-science expeditions is a beneficial way of providing cost-effective satellite validations and may also have a societal impact by involving more people in the climate monitoring of ice sheets
Monitoring for seismological and geochemical groundwater effects of high-volume pumping of natural gas at the Stenlille underground gas storage facility, Denmark
No full textThe large natural gas storage facility at Stenlille, Denmark, has been monitored to investigate the effect of pumping large amounts of gas into the subsurface. Here, we present a new dataset of microseismicity at Stenlille since 2018. We compare these data with methane in groundwater, which has been monitored since gas storage was established in 1989. Further, we conducted a controlled 172 day microcosm experiment of methane oxidation on an isolated microbial community under both aerobic and anaerobic conditions. For this experiment, water was filtered from a well at Stenlille with elevated levels of thermogenic methane and ethane. No microseismic activity was detected in the gas storage area above an estimated detection level of ML 0.0 for the established network. The long-term monitoring for methane in groundwater has still only detected one leak, in 1995, related to a technical problem during injection. The microcosm experiment revealed that oxidation of methane occurred only under aerobic conditions during the experiment, as compared to anaerobic conditions, even though the filtered water was anoxi
Peneplains and tectonics in North-East Greenland after opening of the North-East Atlantic
No full textElevated plateaus with deeply incised valleys characterise elevated, passive continental margins (EPCMs) in all climate zones. These features are, however, a topic of debate regarding when and how the large-scale landscapes formed. We have investigated and mapped the partly glaciated landscape of North-East Greenland (70–78°N). The area consists of crystalline basement and Palaeozoic–Mesozoic rift basins, capped by Palaeogene basalts that erupted during the northeast Atlantic break-up. Our stratigraphic landscape analysis reveals a typical EPCM dominated by two elevated erosion surfaces, extending 200 km east–west and 900 km north–south. The low-relief Upper Planation Surface (UPS; c. 2 km above sea level) cuts across basement and Palaeogene basalts, indicating that it was graded to base level defined by the Atlantic Ocean in post-basalt times and subsequently uplifted. The UPS formed prior to the deposition of mid-Miocene lavas that rest on it, south of the study area. In the interior basement terrains, the Lower Planation Surface (LPS) forms fluvial valley benches at c. 1 km above sea level, incised below the UPS. The LPS is thus younger than the UPS, which implies that it formed post mid-Miocene. Towards the coast, the valley benches merge to form a coherent surface that defines flat-topped mountains. This shows that the LPS was graded to near sea level and was subsequently uplifted. Hence, both the UPS and the LPS formed as peneplains – erosion surfaces graded to base level. The fluvial valley benches associated with the LPS further indicates that full glacial conditions were only established after the uplift of the LPS in the early Pliocene (c. 5 Ma). The uplift of the LPS led to re-exposure of a Mesozoic etch surface. We conclude that episodes of late Neogene tectonic uplift shaped the stepped landscape and elevated topography in North-East Greenland
The Permian to Cretaceous succession at Permpasset, Wollaston Forland: the northernmost Permian and Triassic in North–East Greenland
No full textPermian to Triassic outcrops in East Greenland diminish significantly northwards. Understanding the northward extent, and nature, of the Permian and Triassic successions has implications for regional palaeogeographic reconstructions and exploration in adjacent offshore basins. Examining the structural relationships between the basement, Permian, Triassic, Jurassic and Cretaceous successions can further our understanding of the tectonic evolution of the region. Here, we describe a hitherto overlooked section through the Permian to Cretaceous from central Wollaston Forland and consider its structural context. The western side of Permpasset forms the upthrown eroded crest of a horst block, which provides exposure of the earliest stratigraphic intervals in the region. The fractured Caledonian basement is overlain by evaporitic marine limestone facies of the Karstryggen Formation, which are succeeded by shallow marine sandstones assigned to the Schuchert Dal Formation, both Upper Permian. The overlying unit records a period of fluvial deposition and is not possible to date. However, an Early to Middle Triassic age (Pingo Dal Group) seems most likely, given regional eustatic considerations. This is, therefore, the most northerly record of Triassic strata in North–East Greenland. West of the horst structure, fine-grained sandstones and bioturbated siltstones of the Jurassic (Oxfordian) Jakobsstigen Formation are recorded. These were downfaulted prior to a prolonged hiatus after which both the Triassic and Jurassic strata were draped by Cretaceous shales of the Fosdalen Formation. The Cretaceous succession is overlain by a thick basalt pile of Eocene age, heralding the opening of the North-East Atlantic. Glendonites overlie Oxfordian siltstones at the base of the middle Albian Fosdalen Formation. These were likely winnowed from slightly older Cretaceous strata and overlie the hiatus surface between the Jurassic and Cretaceous. This is the first record of glendonites from the Cretaceous of East Greenland and they are interpreted to record the Circum–Arctic late Aptian – early Albian cooling event
Kortbladsbeskrivelse, Geologisk kort over Danmark, 1:50 000, Møn Dele af 1511 I, 1511 IV og 1512 II: With a summary in English
No full textDet geologiske kortblad Møn omfatter Møn med de tilgrænsende øer Langø, Lindholm og Nyord samt mindre dele af Sjælland og Falster. Kortet består af dele af de topografiske kortblade 1511 I og 1512 II samt 1511 IV med randområder af tilgrænsende kortblade mod vest og nord.
Møn opdeles i tre geomorfologiske områder: det stærkt kuperede Høje Møn mod øst, det småbakkede landskab omkring Stege Nor mod vest, og det flade marine forland omkring Nyord og Ulfshale. Høje Møn opbygges af opskudte skiver af skrivekridt og kvartære aflejringer, som det ses i Møns Klint. Skiverne er op til 80 m tykke, hvoraf skrivekridtet udgør ca. 50 m. Under hele Møn består prækvartæroverfladen af Maastrichtien skrivekridt i en dybde omkring kote –25 til –40 m. Mindre skiver af glacialtektonisk forstyrret skrivekridt optræder også omkring Stege Nor og langs sydkysten af det vestlige Møn ved Hvideklint.
De ældste kvartære aflejringer er moræneler fra Saale-istiden og sand og ler fra Eem-mellemistiden. Derefter følger fluviale aflejringer og nedskylslag fra Tidlig Weichsel. Disse lag efterfølges af moræneler fra Ristinge Klint Till Formationen med over- og underliggende smeltevandsaflejringer fra Mellem Weichsel dannet under Ristinge Isfremstødet for ca. 55 000–50 000 år siden. Den næste enhed er Kraneled Formationen (ny formation), som efterfølges af moræneler tilhørende Klintholm Till Formationen (justeret formation) fra Klintholm Isfremstødet for 35 000–32 000 år siden. Formationen overlejres af mere end 10 m tykke enheder af gråt til olivengråt issøler med dropsten, smeltevandssand og lamineret fint sand samt diamikte aflejringer i Kobbelgård Formationen (ny formation). Denne formation blev aflejret i en issø, som dækkede store dele af Østersøen i en mildningsperiode for 32 000– 28 000 år siden. Denne enhed overlejres af eller er øverst sammenflettet med sand og grus tilhørende Stubberup Have Formationen (ny formation). Moræneler tilhørende den Midtdanske Till Formation blev aflejret under NØ-Isfremstødet for 23 000–20 000 år siden. Efter at NØ-Isen var smeltet tilbage fra østersøområdet, rykkede den Ungbaltiske Is frem fra den østlige del af Østersøen, hvorunder bl.a. Møns Klint og Hvideklint blev deformeret. En tilhørende strukturel enhed, Møns Klint Glacialdynamiske Kompleks, er defineret med fire sekvenser. Hele Hjelm Bugt dannede en glacial lobe, og nord herfor dannedes et randmorænestrøg. Radialt ud fra loben dannede smeltevandet store afløbskanaler fra gletsjerporte i den Ungbaltiske Is. Aflejring af sand og grus tilhørende Ny Borre Formationen (ny formation) skete i dette tidsrum. Under det Ungbaltiske Isfremstød blev Lolland Till Formationen aflejret som et relativt tyndt lag af moræneler.
Ved slutningen af Weichsel-istiden for ca. 17 000 år siden smeltede den Ungbaltiske Is tilbage. Et residualt isdække i området nordøst for Møn sendte et genfremstød til det østlige Møn, som medførte en reorientering af skrivekridtskiverne i Møns Klint. I Sen Weichsel (17 000–11 700 år før nu) fandtes søbassiner på det sydlige Møn ved Hjelm og Tøvelde samt på Høje Møn, hvor en række ferskvandslag blev dannet, og aflejringen fortsatte et stykke ind i Holocæn.
I Holocæn blev de tidligere afløbskanaler transgrederet under den atlantiske havstigning, hvorved fjorde skar sig ind fra nord og nordvest til midt på Møn. Herefter begyndte udbygningen af marine forlande, især mod nord i området Ulvshale og Nyord. De tidligere fjorde voksede til med planter, som omdannedes til tørveaflejringer. Den sidste sedimentationsfase skete langs kysterne, hvor strandvolde blev akkumuleret, og kystklitter af flyvesand blev dannet
Late Glacial and Holocene shore-level changes in the Aarhus Bugt area, Denmark
No full textWe propose a new relative shore-level curve for the Aarhus Bugt area, an embayment in eastern Jylland, Denmark, based on a compilation of published and new radiocarbon ages of organic material. Lakes existed in the area during the Late Glacial and Early Holocene. Lake level rose gradually until the region was inundated by the sea at c. 9000 cal. years BP. The relative sea level reached a high stand at about 6000 cal. years BP, when the local relative sea level was c. 3 m above present-day mean sea level. The Aarhus Bugt area was inundated by the sea later than the Limfjord area in northern Jylland, but earlier than the Lillebælt region in southern Denmark. The shore-level curves for these areas differ partly because the glacio-isostatic uplift was more pronounced in the Limfjord area than farther south and partly because the northern regions were inundated by the sea earlier than the southern areas
The geological framework for Hvideklint, south-east Denmark, using glaciodynamic sequence stratigraphy
No full textGlaciodynamic sequence stratigraphy provides a practical model for grouping and classifying complex geological data to aid interpretation of past climatic and environmental development in Quaternary successions. The principles of glaciodynamic sequence stratigraphy are applied here to summarise the complex glacial geological framework of Hvideklint on the island of Møn, south-east Denmark. The framework of the superimposed deformed Hvideklint is presented in a reconstructed geological cross-section of Hvideklint. For the construction of the architecture of the glaciotectonic complex, the interpretation of structures below sea level was based on a detailed new survey of the cliff section combined with construction of successive approximation balanced cross-sections. The new description is supported by drill hole data from the Jupiter database. Where chalk is not glaciotectonically deformed, the constructed depth to the top-chalk-surface is generally located about 30 m below sea level. In Hvideklint, thrust sheets with chalk are exposed 20 m above sea level, and the balanced cross-section constructions indicate that the décollement surface for a Hvideklint glaciotectonic complex is located about 80 m below sea level. Between the décollement level and the top of the complex, two or more thrust-fault flat-levels and connecting ramps add to the complex architecture of Hvideklint
New insights from field observations of the Younger giant dyke complex and mafic lamprophyres of the Gardar Province on Tuttutooq island, South Greenland
No full textThe Gardar Province of south Greenland is defined by the products of alkaline igneous magmatism during the Mesoproterozoic. The most laterally extensive Gardar intrusions are a series of giant dyke complexes best exposed on the Tuttutooq archipelago. We present new field observations and a geological map of north-east Tuttutooq island that provide fresh insights into the temporal evolution of the Younger giant dyke complex and two associated ultramafic lamprophyres. Our data demonstrate that distinctive crystallisation regimes occurred in different sectors of the dyke complex, leading to the formation of marginal gabbros and ovoid pod-like domains displaying lamination, modal layering and/or more evolved differentiates. We infer that at least two pulses of magma contributed to the formation of the Younger giant dyke complex. In addition, the relative ages of two ultramafic lamprophyre diatremes are constrained and attributed to two distinct phases of rifting in the Gardar Province
Estimating pesticides in public drinking water at the household level in Denmark
No full textPesticide pollution has raised public concern in Denmark due to potential negative health impacts and frequent findings of new substances after a recent expansion of the groundwater monitoring programme. Danish drinking water comes entirely from groundwater. Both the raw groundwater and the treated drinking water are regularly monitored, and the chemical analyses are reported to a publicly available national database (Jupiter). Based on these data, in this study we (1) provide a status of pesticide content in drinking water supplied by public waterworks in Denmark and (2) assess the proportion of Danish households exposed to pesticides from drinking water. ‘Pesticides’ here refers also to their metabolites, degradation and reaction products. The cleaned dataset represents 3004 public waterworks distributed throughout the country and includes 39 798 samples of treated drinking water analysed for 449 pesticides (971 723 analyses total) for the period 2002–2019. Of all these chemical analyses, 0.5% (n = 4925) contained a quantified pesticide (>0.03 μg/l). Pesticides were found at least once in the treated drinking water at 29% of all sampled public waterworks for the period 2002–2019 and at 21% of the waterworks for the recent period 2015–2019. We estimate that 56% of all Danish households were potentially exposed at least once to pesticides in drinking water at concentrations of 0.03–4.00 μg/l between 2002 and 2019. However, in 2015–2019, the proportion of the Danish households exposed to pesticides (0.03–4.00 μg/l) was 41%. The proportion of Danish households potentially exposed at least once to pesticides above the maximum allowed concentration (0.1 μg/l) according to the EU Drinking Water Directive (and the Danish drinking water standard) was 19% for 2002–2019 and 11% for 2015–2019. However, the maximum concentrations were lower than the World Health Organization’s compound-specific guidelines. Lastly, we explore data complexity and discuss the limitations imposed by data heterogeneity to facilitate future epidemiological studies
Greenland bare-ice albedo from PROMICE automatic weather station measurements and Sentinel-3 satellite observations
No full textThe Programme for Monitoring of the Greenland Ice Sheet (PROMICE) provides surface meteorological and glaciological measurements from widespread on-ice automatic weather stations since mid-2007. In this study, we use 105 PROMICE ice-ablation time series to identify the timing of seasonal bare-ice onset preceded by snow cover conditions. From this collection, we find a bare-ice albedo at ice-ablation onset (here called bare-ice-onset albedo) of 0.565 ± 0.109 that has no apparent spatial dependence among 20 sites across Greenland. We then apply this snow-to-ice albedo transition value to measure the variations in daily Greenland bare-ice area in Sentinel-3 optical satellite imagery covering the extremely low and high respective melt years of 2018 and 2019. Daily Greenland bare-ice area peaked at 153 489 km² in 2019, 1.9 times larger than in 2018 (80 220 km²), equating to 9.0% (in 2019) and 4.7% (in 2018) of the ice sheet area