Field guide GLANAM 3 rd workshop and field excursion in Isfjorden, Svalbard 15 th June 2015

Transcription

1 Field guide GLANAM 3 rd workshop and field excursion in Isfjorden, Svalbard 15 th June 2015 by Lis Allaart, Lena Håkansson & Riko Noormets Excursion route: Longyearbyen Ymerbukta/Esmarkbreen Barentsburg Longyearbyen

2 Bedrock Geology Geological map and legend of outer Isfjorden area. At the mouth of Isfjorden, sections through various structural geological elements are displayed: the western basement uplift of Precambrian rocks, the Tertiary fold and thrust belt with Carboniferous through Tertiary rocks and the western limb of the foreland basin of the Central Tertiary basin (Dallmann et al 1992). These elements are found at both sides of the fjord mouth. The Precambrian basement is exposed at the bird cliff, Alkhornet, at the northern side of Isfjorden, immediately west of Trygghamna.

3 Alkhornet It consists of metamorphosed Proterozoic carbonates. The surrounding basement west and northwest of Trygghamna constitutes phyllites interbedded with carbonates and remnants of sills. All of these rocks have been subjected to intense folding and eastward thrusting and their juxtaposition is assumed to have happened during the Caledonian period ( m.y., Dallmann et al 1999). The old basement complex is called Hecla Hoek (Nordenskiöld 1863). East of Trygghamna are exposed Lower Carboniferous to Tertiary rocks. Early Carboniferous sandstones and Mid Carboniferous clastics were deposited in restricted graben environments (Dallmann et al 1992). Late Carboniferous to Permian carbonate rocks with some evaporites and Mesozoic shale/sandstone sequences were mainly deposited while Svalbard was submerged (Dallmann et al 1992). Almost undeformed, flat lying strata of Cretaceous to Tertiary age are seen on the strandflat called Erdmannflya, representing the northern limit of the Central Tertiary Basin. The upper Cretaceous deposits contain sandstones with abundant plant fossils. The transition to Tertiary deposits is marked by an erosional unconformity and the first deposit of Tertiary age is a thin conglomerate. Two coal seams in the lower Tertiary deposits are being exploited by the Russian coal company Trust Arktikugol. Strata of Late Triassic to Creatceous age are exposed on a large strandflat, Bohemanflya, Northeast of Erdmanflya. The whole package is dipping towards south. The Late Triassic deposits constitute mainly sandstones, the Jurrassic are mainly shales and the Cretaceous constitute thick sandstones with coal seams.

4 The Holocene glacial history of Svalbard short version Deglaciation Isfjorden is the largest fjord system on Svalbard, cutting into the central part of Spitsbergen Island and opening towards the Greenland Sea in the west. The Isfjorden basin was deglaciated between cal ka BP (Svendsen and Mangerud 1997). The ice front was retreating from the outer part of Isfjorden to Billefjorden between 11.3 and 11.2 ka BP. The annual retreat rate was up to 170 m/y based on the distribution of recessional moraines on the fjord floor in Billefjorden (Baeten et al 2010). The last phase of the deglaciation of the fjord around 11.2 ka BP was dominated by intense iceberg rafting (Forwick and Vorren 2009). In early Holocene, the glacier margins retreated to their modern limits or even further inland, although the Svalbard archipelago most likely did not deglaciate completely (Ingólfsson 2011, Hormes et al 2013). Extensive seepage of hydrocarbons from the seafloor through faults and lithological boundaries took place during this time resulting in the formation of numerous pockmarks on the fjord floor (Roy et al 2015). A B Bedock geology and bathymetry (A) and pockmark concentration (B) in Isfjorden (Roy et al 2015) Holocene Thermal maximum The Holocene Thermal Maximum (HTM) is represented in the geological of record Svalbard with change from glacier proximal to marine deposition, abundance of thermophile molluscs, low number of IRD, raised beaches and absence of permafrost (Salvigsen et al 1992; Humlum 2005; Jessen et al 2010; Ingólfsson 2011). Although the timing of the HTM varied throughout the archipelago, core data suggest HTM around 10.8 ka BP in Isfjorden area (Svendsen and Mangerud 1997). Neoglaciation The activity of calving glaciers in Billefjorden and Tempelfjorden increased around 5.5 ka BP (Baeten et al 2010). Linnébreen glacier, situated near the mouth of Isfjorden, started forming around ka BP (Svendsen and Mangerud 1997). At the same time, thermophile molluscs appeared in the waters around Svalbard (Salvigsen et al 1992). Permafrost started forming arguably at 3.0 ka BP (Humlum 2005). Little Ice Age In Svalbard, the term the Little Ice Age (LIA) usually refers to the period of years BP (Salvigsen and Høgvard 2005). Areas between the maximum extent of glaciers during

5 Neoglacial and their modern extent are marked by series of ice recessional moraines for many Svalbard glaciers (Svendsen and Mangerud 1997; Sletten et al 2001). However, it should be noted that the chronological control on the majority of these moraines is poor, except for a few fjords where they have been studied in detail (Ottesen and Dowdwswell 2006; Flink et al 2015). For terrestrially terminating glaciers the assumed LIA moraines are found 1 2 km in front of the present day glacier fronts (Werner 1993; Christoffersen et al 2005; Friis 2015). They are ice cored and stand out as significant features in the landscape (Sletten et al 2001). Ymerbukta Ymerbukta is a 9 km long fjord at the northern side of the entrance to Isfjorden. The head of the fjord is occupied by the calving glacier margin of Esmarkbreen. Ymerbukta and the front of Esmarkbreen The glacial history of Ymerbukta has not been studied in detail. Salvigsen et al (1990) suggest that after initial deglaciation, Esmarkbreen readvanced shortly after 9,500 BP, which was probably a local and short lasting event. The marine limit in the area is found at around 60 m above the present sea level, and date back to about 10,000 BP (Salvigsen et al 1990). Extent of Esmarkbreen glacier

6 Raised beached at Erdmannodden Beach ridges are found all the way from the marine limit to the present shore and radiocarbon ages indicate a rapid relative uplift during early Holocene (Salvigsen et al 1990). Historical records show that Esmarkbreen was at its Neoglacial maximum in 1910 (De Geer, 1910), an ice marginal position marked by prominent lateral moraines on both sides of the fjord. Multibeam bathymetric data from the Ymerbukta reveal a set of landforms consisting of large transverse moraines, locally superimposed by glacial lineations and a series of small recessional moraines. These landforms are confined in the Ymerbukta basin that is separated from the Isfjorden by a shallow sill featuring probably a large terminal moraine. Although this landform assemblage has not been studied in detail, striking similarities with the submarine landform assemblage documented from the adjacent Borebukta (Ottesen & Dowdeswell 2006) suggests that the glacial evolution of these two fjords has been relatively alike. As recently as in August September 2014, the Esmarkbreen underwent a mini surge. This was captured on glacier velocity maps. This surge, however, seems to have stopped by now.

7 References Baeten, N. J., Forwick, M., Vogt, C., & Vorren, T. O. (2010). Late Weichselian and Holocene sedimentary environments and glacial activity in Billefjorden, Svalbard. Geological Society, London, Special Publications, 344(1), Christoffersen, P., J.A. Piotrowski and N.K. Larsen, 2005, Basal processes beneath an Arctic glacier and their geomorphic imprint after a surge, Elisebreen, Svalbard, Quaternary Research, 64, Dallmann, W.K., Hjelle, A., Andresen, A., Ohta, Y., & Salvigsen, O Geological map, Svalbard, 1:100,000, B9G Isfjorden. Norsk Polarinstitutt. Dallmann, W.K Lithostratigraphic Lexicon of Svalbard, Upper Palaeozoic to Quaternary Bedrock. Norsk Polarinstitutt. D Andrea, W. J., Vaillencourt, D. A., Balascio, N. L., Werner, A., Roof, S. R., Retelle, M., & Bradley, R. S. (2012). Mild Little Ice Age and unprecedented recent warmth in an 1800 year lake sediment record from Svalbard. Geology, 40(11), De Geer, G., A geological excursion to central Spitzbergen. Congrès Géologique Flink, A.E., Noormets, R., Kirchner, N., Benn, D.I., Luckman, A. & Lovell, H., The evolution of a submarine landform record following recent and multiple surges of Tunabreen glacier, Svalbard. Quaternary Science Reviews 108, Friis, N. (2015). Stratigraphy and sedimentary properties of drumlinoid landforms in the forefield of Nordenskiöldbreen, Svalbard. Master thesis, Faculty of Science, University of Copenhagen. Forwick, M., Vorren, T.O., Late Weichselian and Holocene sedimentary environments and ice rafting in Isfjorden, Spitsbergen. Palaeogeography, Palaeoclimatology, Palaeoecology 280, Hjelle, A Svalbards Geologi. Norsk Polarinstitutt. Holm, T.M., Koinig, K.A., Andersen, T., Donali, E., Hormes, A., Klaveness, D. and Psenner, R., Rapid physicochemical changes in the high Arctic Lake Kongressvatn caused by recent climate change. Aquatic Sciences. Holmgren, S.U., Bigler, C., Ingólfsson, Ó. and Wolfe, A.P., The Holocene Anthropocene transition in lakes of western Spitsbergen, Svalbard (Norwegian High Arctic): climate change and nitrogen deposition. Journal of Paleolomnology, 43, Hormes, A., Gjermundsen, E. F., & Rasmussen, T. L. (2013). From mountain top to the deep sea deglaciation in 4D of the northwestern Barents Sea ice sheet. Quaternary Science Reviews, 75, Humlum, O. (2005). Holocene permafrost aggradation in Svalbard. Geological Society, London, Special Publications, 242(1), Ingólfsson, Ó. (2011). Fingerprints of Quaternary glaciations on Svalbard. Geological Society, London, Special Publications, 354(1), Lauritzen, Ø., Andersen, A., Salvigsen, O. and Winsnes, T.S Geological map of Svalbard 1:100,000. Sheet C8G Billefjorden. Luoto, T.P., Nevalainen, L., Kubischta, F., Kultti, S., Knudsen, K.L., Salonen, V. P., Late Quaternary ecological turnover in High Arctic Lake Einstaken, Nordaustlandet, Svalbard (80 N). Geografiska Annaler: Series A,

8 Physical Geography 93, Maher, H. D., & Braathen, A. (2011). Løvehovden fault and Billefjorden rift basin segmentation and development, Spitsbergen, Norway. Geological Magazine, 148(01), Ottesen, D. & Dowdeswell, J.A., Assemblages of submarine landforms produced by tidewater glaciers in Svalbard. Journal of Geophysical Research, Earth Surface 111, Roy, S., Hovland, M., Noormets, R. & Olaussen, S., Seepage in Isfjorden and its tributary fjords, West Spitsbergen. Marine Geology 363, Salvigsen, O., Elgersma, A., Hjort, C., Langerlund, E., Liestøl, O., & Svansson, N O., Glacial history and shoreline displacement on Erdmannflya and Bohemanflya, Spitsbergen, Svalbard. Polar Research 8, Salvigsen, 0., Forman, S. L. & Miller, G. H Thermophilous molluscs on Svalbard during the Holocene and their paleoclimatic implications. Polar Research 11(1), Salvigsen, O. and Høgvard, K., Glacial history, Holocene shoreline displacement and palaeoclimate based on radiocarbon ages in the area of Bockfjorden, northwestern Spitsbergen, Svalbard. Polar Research, 125(1), Sleten, K., Lyså, A. & Lønne, I Formation and disintegratio n of a high arcti c ice cored moraine complex, Scott Turnerbreen, Svalbard. Boreas, Vol. 30, Svendsen, J.I. & Mangerud, J Holocene glacial and climatic variations on Spitsbergen, Svalbard. The Holocene, Werner, A., Holocene moraine chronology, Spitsbergen, Svalbard: lichenometric evidence for multiple neoglacial advances in the Arctic. The Holocene, 3(2), Bathymetric data from Norwegian Mapping Authority reproduced with permission No. 13/G706.