Náttúrufræðingurinn

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Náttúrufræðingurinn - 2010, Qupperneq 49

Náttúrufræðingurinn - 2010, Qupperneq 49
129 Tímarit Hins íslenska náttúrufræðifélags Þakkir Að kortlagningu landgrunnsins, sem hér er fjallað um, komu Páll Reynisson, Héðinn Valdimarsson og Jóhannes Briem á Hafrannsóknastofnuninni, auk Haraldar Sigurðssonar eldfjallafræðings sem tók þátt í fyrstu mælingum undan Miðsuðurlandi. Gunnar Örvarsson hjá Hafrannsóknastofnuninni/ Fiskistofu hafði yfirumsjón með tölvumálum fjölgeislamælis. Þá á áhöfn rs Árna Friðrikssonar drjúgan þátt í verkinu. Þeim er öllum þakkað fyrir gott samstarf. Heim ild ir Open University Team 1989. Ocean Chemistry and Deep-Sea Sediments. 1. Pergamon Press/The Open University. 134 bls. Simpson, J.E. 1997. Gravity Currents in the Environment and the Labora-2. tory. Cambridge University Press, 2. útg. 244 bls. Davies, T.A. & Laughton, A.S. 1972. Sedimentary processes in the North 3. Atlantic. Í: Initial Reports of the Deep-Sea Drilling Project, vol. 12 (ritstj. Laughton, A.S., Berggren, W.A. o.fl.). U.S. Goverment Printing Office, Washington. Bls. 905–934. Lonsdale, P. & Hollister, C.D. 1979. Cut-offs at an abyssal meander south 4. of Iceland. Geology 7. 597–601. Johnson, G.L. & Guðmundur Pálmason 1980. Observations of the mor-5. phology and structure of the sea floor south and west of Iceland. Journal of Geophysics 47. 23–30. Lacasse, C., Carey, S. & Haraldur Sigurðsson 1998. Volcanogenic sedimen-6. tation in the Iceland Basin: influence of subaerial and subglacial eruptions. Journal of Volcanology and Geothermal Research 83 (1–2). 47–73. Svend-Aage Malmberg 1974. A note on the deep water south of Iceland. 7. International Council for the Exploration of the Sea “Overflow ’73”. ICES. CM. C:32. Egloff, J. & Johnson, G.L. 1979. Erosional and depositional structures of 8. the southwest Iceland insular margin: Thirteen geophysical profiles. Í: Geological and geophysical investigations of continental margins (ritstj. Watkins, J.S., Montadert, L. & Dickerson, P.W.). American Association of Petroleum Geologists Memoir 29. 43–63. Kjartan Thors & Boulton, G.S. 1991. Deltas, spits and littoral terraces 9. associated with rising sea level: Late Quaternary examples from north- ern Iceland. Marine Geology 98. 99–112. Kjartan Thors & Guðrún Helgadóttir 1991. Evidence from south west 10. Iceland of low sea level in early Flandrian times. Í: Envorinmental Change in Iceland: Past and Present (ritstj. Maizels, J.K. & Caseldine, C.). Bls. 93–104. Um höfundana Guðrún Helgadóttir (f. 1953) lauk B.Sc.-prófi í jarðfræði frá Háskóla Íslands 1979 og cand.scient.-prófi í jarð- fræði frá Háskólanum í Ósló 1985. Hún hefur starfað á Hafrannsóknastofnuninni frá 1985, lengst af sem sér- fræðingur. Kjartan Thors (f. 1945) lauk B.Sc.(Hons.)-prófi í jarð- fræði frá Háskólanum í Manchester 1969 og Ph.D.-prófi 1974. Hann starfaði sem sérfræðingur á Hafrannsókna- stofnuninni 1974–1995, var stundakennari við Háskóla Íslands 1975–1998 og ritstjóri Náttúrufræðingsins 1976– 1980. Frá 1995 hefur Kjartan rekið eigin jarðfræðistofu. Póst- og netföng höfunda/Authors’ addresses Guðrún Helgadóttir Hafrannsóknastofnuninni Skúlagötu 4 IS-101 Reykjavík gudrun@hafro.is Kjartan Thors Jarðfræðistofu Kjartans Thors Suðurlandsbraut 16 IS-108 Reykjavík kthors@centrum.is Lokaorð Hér hefur verið lýst farvegum gruggstrauma djúpt suður af Íslandi með fjölgeisladýptarkortum. Til að glöggva sig enn frekar á umfangi og rennslisleiðum jökulhlaupa/ gruggstrauma er þörf á viðameiri kortlagningu suður af landinu, sér- staklega á grunnsævi, þ.e. frá helstu árósum að landgrunnsbrún, en einnig í landgrunnshlíðunum þar sem vitað er um fleiri farvegi. Á þann hátt væri unnt að meta þau áhrif sem jökulhlaup framtíðarinnar kunna að hafa og bera saman við fyrri tíma atburði. Summary Turbidity currents and sub- marine channels off southern Iceland Turbidity currents are among the most important means of transferring sedi- ments to the deep ocean floor. Recent multibeam surveys off southern Iceland bring out the details of channels and canyons produced by such currents. These have served as pathways for sed- iment flow from southern Iceland. The major canyons, Reynisdjúp canyon and Mýrdalsjökull canyon, seem to have collected sediments from a wide area of the insular slope off southern Iceland. We agree with previous authors that turbidity currents in these canyons were most likely triggered by jökul- hlaups on land, events that brought great amounts of volcanic sediments to the sea. In view of the relatively smooth surface of the upper insular slope, and the lack of canyons incised in the shelf edge, we argue that turbidity currents were most active during the Ice age and that reduced activity has allowed the buildup of an insular shelf and shelf edge in postglacial times. This shelf edge is now seen to bury the upper part of the submarine canyons observed lower down on the slope. 80 3-4#Loka_061210.indd 129 12/6/10 7:22:24 AM
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