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Sedimentology of fjords
III
PREFACE Sedimentology of Fjords Fjords are deep, glacially excavated estuaries that have several unique characteristics compared to shallower embayments. They are common to high-latitude western coastlines and much of the Arctic coastline. Fjord research has attracted a large international following of oceanographers since the eighteenth century for both practical and scientific considerations. Like other estuary types, many fjords have become the marine toilet of man's activities on these coasts and are sinks for authropogenic disposal. However, the slower flushing times that are unique to fjords, compared to other estuarine types, allow build-up of pollutants in water, biota and sediments. High organic input to fjords already approaching eutrophication may have a critical effect. Anoxic waters can devastate the pelagic and benthic biota. The most essential problem with respect to pollution and sediments is how to assess the ecological impact of polluted sediments (i.e. under what conditions do the pollutants have a high bioavailability factor). The need here is for an understanding of nature's resilience and natural processes operating in fjords. Fjords also command attention for their intrinsic scientific identity. Recent attention may well be a rediscovery, for much of the classical theories in oceanographic processes have eminated from research carried out in fjords. Then, like now, scientists have been aware of the advantages of working in enclosed mini-oceans where the process rates are fast and environmental gradients large. For instance, particle and flow dynamics in large prodelta environments are best studied in appropriate fjord settings, since the sheer size of the former do not lend themselves to accurate monitoring. Also, fjords with permanent anoxic conditions are ideal for the investigation of geochemical processes (such as kinetic reactions) that were operative over major anoxic periods of the Earth's history. Additionally, the lack of bioturbation of anoxic sediments allows for the formation of varves whose cyclicity may model the history of climate, discharge, water temperature or some combination thereof. Steep fjord walls and sills provide boundary conditions ideal for the modelling of bottom friction effects on circulation as well as for studies of the generation of large-scale turbulence from bottom roughness. The modelling of such fluid dynamic parameters provides insights into the laws governing sediment gravity flows, thus relating physical oceanography models to sediment transport problems. Modelling, then, appears to be the common denominator that makes fjords an extension of the scientists' laboratory flumes. Fjords also provide a detailed sedimentary record that mirrors the local terrestrial
tv and marine processes and dynamics. Stratigraphic interpretation can therefore provide insight into the impact of past and future climatic conditions. From a geophysical point of view fjords are ideal sites to measure parameters indicative of postglacial isostatic rebound and subsequent seismic effects. In view of the importance of fjords in sedimentological work and the widespread interests in fjord-related topics, a symposium on the "Sedimentology of Fjords" was held during the Eleventh Congress of the International Association of Sedimentologists, Hamilton, Canada (August 22-27, 1982). With two exceptions, papers enclosed in this special issue are from that Symposia. The papers cover a wide range of topics, such as: (1) the interaction between sedimentological and biological processes (fecal pellet production); (2) the importance of man-made sources of organic matter to fjord sediments in areas of low primary production; (3) the usefulness of Pb-210 datings of tjord sediments to evaluate historical events in the drainage area and to establish deposition rates; (4) the influence of mine tailing disposal on morphology, sediment texture and geochemistry of fjord sediments through the generation of turbidity currents; (5) the significant processes that are operative in the formation of bayhead deltas and the resultant facies models; (6) the measurement of flux rates in anoxic basins and the ensuing kinetic reactions; and (7) the prominent processes in the transport and deposition of sediment in Arctic fjord environments. The papers describe the state-of-the-art with respect to present knowledge, unresolved problems and potential research in fjord environments. We wish to thank the contributors for their dedicated efforts at the meeting in Hamilton and their timely submission of papers for this special volume. Acknowledged are the conscientious reviewers of the individual papers: G.S. Boulton, A.J. Bowen, M. Church, R. Cranston, D. Eisma, A. Elverhoi, D.L. Forbes, R. Gilbert, A.E. Hay, F. Hein, P. Hill, L.A. Hobson, A.G. Lewis, P. Mudie, W.R. Normark, T.F. Pederson, D.J.W. Piper, R.D. Powell, C.T. Schafer, M. Stoffyn, P. Stoffyn, and G. Vilks. Finally, the guest editors thank the Geological Survey of Canada, Bedford Institute of Oceanography, Dartmouth (Canada) and the Norwegian Institute for Water Research, Oslo (Norway) for their support during the editorial work. J.P.M. SYVITSKIand J.M. SKEI (Editors)
PREFACE Sedimentology of Fjords Fjords are deep, glacially excavated estuaries that have several unique characteristics compared to shallower embayments. They are common to high-latitude western coastlines and much of the Arctic coastline. Fjord research has attracted a large international following of oceanographers since the eighteenth century for both practical and scientific considerations. Like other estuary types, many fjords have become the marine toilet of man's activities on these coasts and are sinks for authropogenic disposal. However, the slower flushing times that are unique to fjords, compared to other estuarine types, allow build-up of pollutants in water, biota and sediments. High organic input to fjords already approaching eutrophication may have a critical effect. Anoxic waters can devastate the pelagic and benthic biota. The most essential problem with respect to pollution and sediments is how to assess the ecological impact of polluted sediments (i.e. under what conditions do the pollutants have a high bioavailability factor). The need here is for an understanding of nature's resilience and natural processes operating in fjords. Fjords also command attention for their intrinsic scientific identity. Recent attention may well be a rediscovery, for much of the classical theories in oceanographic processes have eminated from research carried out in fjords. Then, like now, scientists have been aware of the advantages of working in enclosed mini-oceans where the process rates are fast and environmental gradients large. For instance, particle and flow dynamics in large prodelta environments are best studied in appropriate fjord settings, since the sheer size of the former do not lend themselves to accurate monitoring. Also, fjords with permanent anoxic conditions are ideal for the investigation of geochemical processes (such as kinetic reactions) that were operative over major anoxic periods of the Earth's history. Additionally, the lack of bioturbation of anoxic sediments allows for the formation of varves whose cyclicity may model the history of climate, discharge, water temperature or some combination thereof. Steep fjord walls and sills provide boundary conditions ideal for the modelling of bottom friction effects on circulation as well as for studies of the generation of large-scale turbulence from bottom roughness. The modelling of such fluid dynamic parameters provides insights into the laws governing sediment gravity flows, thus relating physical oceanography models to sediment transport problems. Modelling, then, appears to be the common denominator that makes fjords an extension of the scientists' laboratory flumes. Fjords also provide a detailed sedimentary record that mirrors the local terrestrial
tv and marine processes and dynamics. Stratigraphic interpretation can therefore provide insight into the impact of past and future climatic conditions. From a geophysical point of view fjords are ideal sites to measure parameters indicative of postglacial isostatic rebound and subsequent seismic effects. In view of the importance of fjords in sedimentological work and the widespread interests in fjord-related topics, a symposium on the "Sedimentology of Fjords" was held during the Eleventh Congress of the International Association of Sedimentologists, Hamilton, Canada (August 22-27, 1982). With two exceptions, papers enclosed in this special issue are from that Symposia. The papers cover a wide range of topics, such as: (1) the interaction between sedimentological and biological processes (fecal pellet production); (2) the importance of man-made sources of organic matter to fjord sediments in areas of low primary production; (3) the usefulness of Pb-210 datings of tjord sediments to evaluate historical events in the drainage area and to establish deposition rates; (4) the influence of mine tailing disposal on morphology, sediment texture and geochemistry of fjord sediments through the generation of turbidity currents; (5) the significant processes that are operative in the formation of bayhead deltas and the resultant facies models; (6) the measurement of flux rates in anoxic basins and the ensuing kinetic reactions; and (7) the prominent processes in the transport and deposition of sediment in Arctic fjord environments. The papers describe the state-of-the-art with respect to present knowledge, unresolved problems and potential research in fjord environments. We wish to thank the contributors for their dedicated efforts at the meeting in Hamilton and their timely submission of papers for this special volume. Acknowledged are the conscientious reviewers of the individual papers: G.S. Boulton, A.J. Bowen, M. Church, R. Cranston, D. Eisma, A. Elverhoi, D.L. Forbes, R. Gilbert, A.E. Hay, F. Hein, P. Hill, L.A. Hobson, A.G. Lewis, P. Mudie, W.R. Normark, T.F. Pederson, D.J.W. Piper, R.D. Powell, C.T. Schafer, M. Stoffyn, P. Stoffyn, and G. Vilks. Finally, the guest editors thank the Geological Survey of Canada, Bedford Institute of Oceanography, Dartmouth (Canada) and the Norwegian Institute for Water Research, Oslo (Norway) for their support during the editorial work. J.P.M. SYVITSKIand J.M. SKEI (Editors)