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Environmental Change in Iceland: Past and Present
Physics of the Earth and Planetary Interiors, 73 (1992) 291—295 Elsevier Science Publishers B.V., Amsterdam
291
Book Reviews Environmental Change in Iceland: Past and Present (Glaciology and Quaternary Geology, Vol. 7). Judith K. Maizels and Chris Caseldine (Editors), Kluwer, Dordrecht, 1991, 332 pp., hardback, Dfl. 175/US$118/~61.ISBN 0 7923 1209 0. Iceland, situated in the middle of the North Atlantic, has experienced great climatic fluctuations which in turn have caused major environmental changes. The climate is highly sensitive to oscillations in the polar front and the Gulf Stream. This book explores climatic and environmental changes in Iceland since the end of the last glaciation and processes modifying the presentday landscape. New data are presented, many traditional ideas are challenged, areas of controversies are clarified and new hypotheses are advanced. The book contains 18 papers, originally presented at a meeting held at the University of Aberdeen in 1989 where some of the scientists working on environmental change in Iceland were brought together. The first six papers deal with late glacial and early Holocene environmental changes and the associated changes in climate and isostatic uplift. The papers demonstrate a far more extensive late Weichselian ice sheet and a later deglaciation date than was previously assumed. The glacial maximum occurred ca. 18000 BP rather than in the early Weichselian. During the deglaciation the oldest morain (of the Aiftanes stadial) date from Younger Dryas (ca. 11000—10000 BP), not Older Dryas (ca. 12000 BP) as previously considered, and the Büöi readvance (stadial) dates from ca. 9700 BP, i.e. from the Preboreal period and are not late glacial (ca. 11000—10000 BP). It seems that the final deglaciation was completed later than previously acknowledged; e.g. not before 9650 BP in EyjafjOrour in north Iceland. Furthermore, the papers describe the sea level reaching its highest point during the late Younger Dryas—early Preboreal. Shoreline evidence is
given for isostatic readjustment and sea-level fluctuations during the deglaciation. The rapid rate of postglacial isostatic rebound demonstrates the low viscosity of subcrustal rocks in Iceland. These results are based on recently acquired radiocarbon dates on marine shells found in raised shorelines and till deposits, tephrochronology, analyses of pollen and microfaunal assemblages, precise levelling of raised shorelines, re-interpretation of off-shore seismic profiling and detailed stratigraphic analysis. The second part of the book deals with environmental changes during the postglacial period. The first four papers of this section discuss changes in the biological record, climatic changes and the relation to human settlement. The work is based on pollen analysis and on collections of beetle and insect fauna from both natural and human habitats. The ‘overwintering’ hypothesis, proposing the survival of present-day flora and fauna in ice free areas in Iceland during the Quaternary glaciation, is challenged. It is suggested that plants and animals arrived on ice-rafts associated with a short period of melting of the continental ice sheet around the eastern North Atlantic, probably around 10000 BP. Faunal changes after the Norse settlement, as a result of human activity, are discussed; the loss of birch woodland by deforestation and sheep grazing and the drainage of pasture land as well as the role of climatic change. Widespread, catastrophic soil erosion, turning shrub- and woodland into desert, was initiated after the Norse settlement in the late 9th century A.D. The final paper in this section deals with the effect of soil erosion and climatic deterioration, disease and economic and social isolation on the abandonment of farms in many districts. Four papers deal with postglacial glacier fluctuations as a tool for the identification of climatic variability, long-term climatic fluctuations and penods of maximum and minimum postglacial ternperatures (during the Holocene climatic optimum
292
and including Neoglacial and historic fluctuations, the ‘Little Ice Age’). This work has been carried out on the alpine type glaciers in the Tröllaskagi area in northern Iceland where there are good oppertunities for such studies. The glacier fluctuations are dated through tephrochronology, radiocarbon dating and interpretation of marine sequences combined with revised lichen growth curves for Rhizocarpon geographicum in northern Iceland for the last 200 years (with lower growth rate for lichens than previously adopted, i.e. 0.44 mm year—’). Here the traditional view, based on pollen analysis, that the entire period from 9000 BP to 2500 BP was a warm climatic optimum, followed by glacier expansion in the ‘Subatlantic Time’ around 2500 BP, is questioned. It is suggested that two glacial advances can be traced and dated to the periods 6000—4800 BP and 3400—2800 BP. In the same area in northern Iceland, a pre-’Little Ice Age’ glacier advance between ca. 1800 BP and 2240 BP and around 1555 BP is reported. This casts doubts on the accepted chronology for the climatic variability during the postglacial period in Iceland. During the last two centuries, six phases of glacier advance and moraine deposition are reported and correlated with periods of low air temperature and the presence of sea ice. A lot of work remains to complete the record of the Holocene glacier variations in the alpine Tröllaskagi area, The third part of the book surveys in four papers processes affecting recent landscape change. This include slope movements, landscape instability in areas subject to high erosion rates and their impact on fluvial systems, and the deposition and removal of sediments in proglacial areas. The existence of rock glaciers, relict glaciers fossilized by a cover of debris, is reported. The rock glaciers have responded slowly to climatic warming in the last 40 years in contrast to the neighbouring glaciers which have retreated over 300 m since 1946. In my opinion, one of the most interesting papers in the book describes the role of jökulhlaups (glacier bursts) in the formation of the main sandur deltas of southern Iceland (by one of the Editors, Dr. Judith Maizels). The author
demonstrates how the sedimentological sequence depends on the nature of the flood hydrograph and the concentration of sediments transported by the floods. The last paper in the book gives a very detailed report on sediment transport in a glacier river draining from the ice cap M~rdalsjökullin southern Iceland. The annual transport is among the highest recorded anywhere in the world (mean annual sediment yield of 14500 t km2 year’; equivalent to a catchment erosion rate of ca. 5.4 mm year~). However, sediment concentrations are shown to be highly variable through the year. Most of the papers are of good scientific quality, containing reliable data and new results. However, some of the papers would have benefitted from the closer acquaintance of their authors with research in Iceland. In this way they could have avoided errors and secured adequate reference to previous work. The book is not an unequivocal source of research history in Iceland. A few examples will be given. Hansom and Briggs, writing about sea-level changes in Vestfiroir, northwest Iceland, state on p. 84 that pine (Pinus spp) spread over bogs in Postglacial Time. This is based on the analysis of a single pollen sample which yielded 10% pine. Usually, Icelandic pollen samples give 1—2% pine; this is attributed to long-distance transport. Other authors on this subject therefore do not assume that pine grew in Iceland at that time or later. Furthermore, Hansom and Briggs should have referred to the work of Báröarson (1910) and Thorarinsson (1955), when discussing Nucella transgression in Iceland. Moreover, they seem to misinterpret Einarsson’s model of the glaciation of Vestfiroir. Buckland and Dugmore write a paper with the title ‘If this is a refugium, why are my feet so bloody cold?’. This paper is inaccurate in places, and while it abounds with bold hypotheses, the support for these is less in evidence. On p. 112, they write “the earliest tillites, probably of glacial origin” in Tjörnes, whereas the word diamictit should be used until glacial origin is confirmed. Here, they should also have referred to EirIksson (1985) and EirIksson et al. (1990) rather than his bibliographic review in Jökull in 1980. On p. 116
293
these authors refer to An Fróöi (the ‘Wise’) in the late 12th century whereas it should be in the early 12th century. Dugmore and Buckland, writing about tephrochronology and late Holocene soil erosion in southern Iceland (p. 157), should have referred to a doctoral thesis on Markarfljót-sandur area by Haraldsson (1981) which considers the same time period. Gerrard should have referred to Hallsdóttir’s (1987) fundamental studies of the effects of the settlement (landnam) on vegetation. In general, the German authors pay careful attention to and cite previous work. However, the aggressive tone of Stötter towards Einarsson’s work is unnecessary. The data speak for themselves. The proofreading of this book might have been better. On p. 102 several of the standard deviations for the carbon 14 datings are wrong, probably by a thousand years which seem to have been added to all of them! In many of the papers the reference list is not carefully compiled (e.g. the reference to Hallsdóttir (1987) on pp. 91, 122, 144 and 159, to Haraldsson (1981) on p. 252, and DavIOsson (1967) on p. 144; Einarsson et a!. (1980) on p. 149 seems to be from 1980, and Ward et a!. (1976) did not publish Jökull 46 as stated on p. 302). References referred to in the text are missing (e.g. Brundsen and Thornes (1979) on p. 246). Furthermore, the layout of the list is very confusing, with neither line spacing nor indention to separate entries. Icelandic names are frequently misspelt. Many of the figures are difficult to read, e.g. on pp. 86—87, 207, 275 (Fig. 5) and 276 (Fig. 6A). This book is a useful compilation of contributions of Icelandic, British, and German scientists to studies of environmental changes in Iceland. On the whole the book will be a worthwhile addition to libraries of institutions concerned with glacial and environmental studies. References Bárdarson, G.G., 1910. Traces of changes of climate and level at Hiinaflói, northern Iceland. Postglaziale Kimaveränderungen (Proc. Geology Congress in Stockholm, 1910), pp. 347-352. DavIOsson, I., 1967. The immigration and naturalization of
flowering plants in Iceland since 1900. Greinar, 4 (3): 1—35. EirIksson, J., 1980. Tjörnes, North Iceland: a bibliographic review of the geological research history. Jökull, 30: 1—20. EirIksson, J., 1985. Facies analysis of the Breidavik group sediments on Tjörnes, North Iceland. Acta Naturalia Islandica, Vol. 31, 56 pp. EirIksson, J., Gudmundsson, A.1., Kristjánsson, L. and GuOmundsson, K., 1990. Paleomagnetism of pliocene—pleistocene sediments and lava flows on Tjörnes and Flatey, North Iceland. Boreas, 19: 39—55. Hallsdóttir, M., 1987. Pollen analytical studies of human influence on vegetation in relation to the Landnán Tephra Layer in southwest Iceland, Lundqua Thesis, Vol. 18. Lund Universit~i,45 pp. Haraldsson, H., 1981. The Markarfljót-sandur area, South Iceland: sedimentological, petrographical and stratigraphic studies. Striae, 15: 1—65. Thorarinason, S., 1955. Nákueungslögin viö Hünaflóa I ljósi n~rra aldursákvarl~ana. The Nucella Shore Line at Hünaflói in the light of tephrochronological and radiocarbon datings. Náttürufr~oingurinn,25: 172—186.
HELGI BJORNSSON (Reykjavik, Iceland) _____________________________________________
China: Stratigraphy, Palaeogeography and Tectonics. Arthur A. Meyerhoff, Maurice KaymenKaye, Chin Chen and Irfan Taner, Kluwer, Dordrecht, 1991, 188 pp., hardback, £74 (Dfl.220, US$124), ISBN 0 7923 09723. The study of Chinese geology is rooted in the great age of scientific expansion and exploration and is associated with legendary figures such as Von Richtofen and Sven Hedin. However, the formal organisation of geological surveying and education in China dates back barely 80 years, a period which has seen emerge those classics of Chinese geological literature Stratigraphy of China (1923—1928) Geology of China (1939). Since 1959 there has been a steady increase in published data on Chinese geology. Work in the English language has shared in this growth, although this has been substantial only since the early 1980s. Readily accessible information published in English, on Chinese geology remains relatively hard to find. Given this situation, this book is to be welcomed as a valuable cornpendium of recent information and views on the
291
Book Reviews Environmental Change in Iceland: Past and Present (Glaciology and Quaternary Geology, Vol. 7). Judith K. Maizels and Chris Caseldine (Editors), Kluwer, Dordrecht, 1991, 332 pp., hardback, Dfl. 175/US$118/~61.ISBN 0 7923 1209 0. Iceland, situated in the middle of the North Atlantic, has experienced great climatic fluctuations which in turn have caused major environmental changes. The climate is highly sensitive to oscillations in the polar front and the Gulf Stream. This book explores climatic and environmental changes in Iceland since the end of the last glaciation and processes modifying the presentday landscape. New data are presented, many traditional ideas are challenged, areas of controversies are clarified and new hypotheses are advanced. The book contains 18 papers, originally presented at a meeting held at the University of Aberdeen in 1989 where some of the scientists working on environmental change in Iceland were brought together. The first six papers deal with late glacial and early Holocene environmental changes and the associated changes in climate and isostatic uplift. The papers demonstrate a far more extensive late Weichselian ice sheet and a later deglaciation date than was previously assumed. The glacial maximum occurred ca. 18000 BP rather than in the early Weichselian. During the deglaciation the oldest morain (of the Aiftanes stadial) date from Younger Dryas (ca. 11000—10000 BP), not Older Dryas (ca. 12000 BP) as previously considered, and the Büöi readvance (stadial) dates from ca. 9700 BP, i.e. from the Preboreal period and are not late glacial (ca. 11000—10000 BP). It seems that the final deglaciation was completed later than previously acknowledged; e.g. not before 9650 BP in EyjafjOrour in north Iceland. Furthermore, the papers describe the sea level reaching its highest point during the late Younger Dryas—early Preboreal. Shoreline evidence is
given for isostatic readjustment and sea-level fluctuations during the deglaciation. The rapid rate of postglacial isostatic rebound demonstrates the low viscosity of subcrustal rocks in Iceland. These results are based on recently acquired radiocarbon dates on marine shells found in raised shorelines and till deposits, tephrochronology, analyses of pollen and microfaunal assemblages, precise levelling of raised shorelines, re-interpretation of off-shore seismic profiling and detailed stratigraphic analysis. The second part of the book deals with environmental changes during the postglacial period. The first four papers of this section discuss changes in the biological record, climatic changes and the relation to human settlement. The work is based on pollen analysis and on collections of beetle and insect fauna from both natural and human habitats. The ‘overwintering’ hypothesis, proposing the survival of present-day flora and fauna in ice free areas in Iceland during the Quaternary glaciation, is challenged. It is suggested that plants and animals arrived on ice-rafts associated with a short period of melting of the continental ice sheet around the eastern North Atlantic, probably around 10000 BP. Faunal changes after the Norse settlement, as a result of human activity, are discussed; the loss of birch woodland by deforestation and sheep grazing and the drainage of pasture land as well as the role of climatic change. Widespread, catastrophic soil erosion, turning shrub- and woodland into desert, was initiated after the Norse settlement in the late 9th century A.D. The final paper in this section deals with the effect of soil erosion and climatic deterioration, disease and economic and social isolation on the abandonment of farms in many districts. Four papers deal with postglacial glacier fluctuations as a tool for the identification of climatic variability, long-term climatic fluctuations and penods of maximum and minimum postglacial ternperatures (during the Holocene climatic optimum
292
and including Neoglacial and historic fluctuations, the ‘Little Ice Age’). This work has been carried out on the alpine type glaciers in the Tröllaskagi area in northern Iceland where there are good oppertunities for such studies. The glacier fluctuations are dated through tephrochronology, radiocarbon dating and interpretation of marine sequences combined with revised lichen growth curves for Rhizocarpon geographicum in northern Iceland for the last 200 years (with lower growth rate for lichens than previously adopted, i.e. 0.44 mm year—’). Here the traditional view, based on pollen analysis, that the entire period from 9000 BP to 2500 BP was a warm climatic optimum, followed by glacier expansion in the ‘Subatlantic Time’ around 2500 BP, is questioned. It is suggested that two glacial advances can be traced and dated to the periods 6000—4800 BP and 3400—2800 BP. In the same area in northern Iceland, a pre-’Little Ice Age’ glacier advance between ca. 1800 BP and 2240 BP and around 1555 BP is reported. This casts doubts on the accepted chronology for the climatic variability during the postglacial period in Iceland. During the last two centuries, six phases of glacier advance and moraine deposition are reported and correlated with periods of low air temperature and the presence of sea ice. A lot of work remains to complete the record of the Holocene glacier variations in the alpine Tröllaskagi area, The third part of the book surveys in four papers processes affecting recent landscape change. This include slope movements, landscape instability in areas subject to high erosion rates and their impact on fluvial systems, and the deposition and removal of sediments in proglacial areas. The existence of rock glaciers, relict glaciers fossilized by a cover of debris, is reported. The rock glaciers have responded slowly to climatic warming in the last 40 years in contrast to the neighbouring glaciers which have retreated over 300 m since 1946. In my opinion, one of the most interesting papers in the book describes the role of jökulhlaups (glacier bursts) in the formation of the main sandur deltas of southern Iceland (by one of the Editors, Dr. Judith Maizels). The author
demonstrates how the sedimentological sequence depends on the nature of the flood hydrograph and the concentration of sediments transported by the floods. The last paper in the book gives a very detailed report on sediment transport in a glacier river draining from the ice cap M~rdalsjökullin southern Iceland. The annual transport is among the highest recorded anywhere in the world (mean annual sediment yield of 14500 t km2 year’; equivalent to a catchment erosion rate of ca. 5.4 mm year~). However, sediment concentrations are shown to be highly variable through the year. Most of the papers are of good scientific quality, containing reliable data and new results. However, some of the papers would have benefitted from the closer acquaintance of their authors with research in Iceland. In this way they could have avoided errors and secured adequate reference to previous work. The book is not an unequivocal source of research history in Iceland. A few examples will be given. Hansom and Briggs, writing about sea-level changes in Vestfiroir, northwest Iceland, state on p. 84 that pine (Pinus spp) spread over bogs in Postglacial Time. This is based on the analysis of a single pollen sample which yielded 10% pine. Usually, Icelandic pollen samples give 1—2% pine; this is attributed to long-distance transport. Other authors on this subject therefore do not assume that pine grew in Iceland at that time or later. Furthermore, Hansom and Briggs should have referred to the work of Báröarson (1910) and Thorarinsson (1955), when discussing Nucella transgression in Iceland. Moreover, they seem to misinterpret Einarsson’s model of the glaciation of Vestfiroir. Buckland and Dugmore write a paper with the title ‘If this is a refugium, why are my feet so bloody cold?’. This paper is inaccurate in places, and while it abounds with bold hypotheses, the support for these is less in evidence. On p. 112, they write “the earliest tillites, probably of glacial origin” in Tjörnes, whereas the word diamictit should be used until glacial origin is confirmed. Here, they should also have referred to EirIksson (1985) and EirIksson et al. (1990) rather than his bibliographic review in Jökull in 1980. On p. 116
293
these authors refer to An Fróöi (the ‘Wise’) in the late 12th century whereas it should be in the early 12th century. Dugmore and Buckland, writing about tephrochronology and late Holocene soil erosion in southern Iceland (p. 157), should have referred to a doctoral thesis on Markarfljót-sandur area by Haraldsson (1981) which considers the same time period. Gerrard should have referred to Hallsdóttir’s (1987) fundamental studies of the effects of the settlement (landnam) on vegetation. In general, the German authors pay careful attention to and cite previous work. However, the aggressive tone of Stötter towards Einarsson’s work is unnecessary. The data speak for themselves. The proofreading of this book might have been better. On p. 102 several of the standard deviations for the carbon 14 datings are wrong, probably by a thousand years which seem to have been added to all of them! In many of the papers the reference list is not carefully compiled (e.g. the reference to Hallsdóttir (1987) on pp. 91, 122, 144 and 159, to Haraldsson (1981) on p. 252, and DavIOsson (1967) on p. 144; Einarsson et a!. (1980) on p. 149 seems to be from 1980, and Ward et a!. (1976) did not publish Jökull 46 as stated on p. 302). References referred to in the text are missing (e.g. Brundsen and Thornes (1979) on p. 246). Furthermore, the layout of the list is very confusing, with neither line spacing nor indention to separate entries. Icelandic names are frequently misspelt. Many of the figures are difficult to read, e.g. on pp. 86—87, 207, 275 (Fig. 5) and 276 (Fig. 6A). This book is a useful compilation of contributions of Icelandic, British, and German scientists to studies of environmental changes in Iceland. On the whole the book will be a worthwhile addition to libraries of institutions concerned with glacial and environmental studies. References Bárdarson, G.G., 1910. Traces of changes of climate and level at Hiinaflói, northern Iceland. Postglaziale Kimaveränderungen (Proc. Geology Congress in Stockholm, 1910), pp. 347-352. DavIOsson, I., 1967. The immigration and naturalization of
flowering plants in Iceland since 1900. Greinar, 4 (3): 1—35. EirIksson, J., 1980. Tjörnes, North Iceland: a bibliographic review of the geological research history. Jökull, 30: 1—20. EirIksson, J., 1985. Facies analysis of the Breidavik group sediments on Tjörnes, North Iceland. Acta Naturalia Islandica, Vol. 31, 56 pp. EirIksson, J., Gudmundsson, A.1., Kristjánsson, L. and GuOmundsson, K., 1990. Paleomagnetism of pliocene—pleistocene sediments and lava flows on Tjörnes and Flatey, North Iceland. Boreas, 19: 39—55. Hallsdóttir, M., 1987. Pollen analytical studies of human influence on vegetation in relation to the Landnán Tephra Layer in southwest Iceland, Lundqua Thesis, Vol. 18. Lund Universit~i,45 pp. Haraldsson, H., 1981. The Markarfljót-sandur area, South Iceland: sedimentological, petrographical and stratigraphic studies. Striae, 15: 1—65. Thorarinason, S., 1955. Nákueungslögin viö Hünaflóa I ljósi n~rra aldursákvarl~ana. The Nucella Shore Line at Hünaflói in the light of tephrochronological and radiocarbon datings. Náttürufr~oingurinn,25: 172—186.
HELGI BJORNSSON (Reykjavik, Iceland) _____________________________________________
China: Stratigraphy, Palaeogeography and Tectonics. Arthur A. Meyerhoff, Maurice KaymenKaye, Chin Chen and Irfan Taner, Kluwer, Dordrecht, 1991, 188 pp., hardback, £74 (Dfl.220, US$124), ISBN 0 7923 09723. The study of Chinese geology is rooted in the great age of scientific expansion and exploration and is associated with legendary figures such as Von Richtofen and Sven Hedin. However, the formal organisation of geological surveying and education in China dates back barely 80 years, a period which has seen emerge those classics of Chinese geological literature Stratigraphy of China (1923—1928) Geology of China (1939). Since 1959 there has been a steady increase in published data on Chinese geology. Work in the English language has shared in this growth, although this has been substantial only since the early 1980s. Readily accessible information published in English, on Chinese geology remains relatively hard to find. Given this situation, this book is to be welcomed as a valuable cornpendium of recent information and views on the