Arctic-alpine blockfields in the northern Swedish Scandes: Late Quaternary - Not Neogene

Earth Surface Dynamics

Volumn 2, Issue 2, 2014, Pages 383-401

  Goodfellow, B W ^a,b   Stroeven, A P ^a   Fabel, D ^c   Fredin, O ^d,e   Derron, M H ^e,f   Bintanja, R ^g   Caffee, M W ^h  

^a STOCKHOLM UNIVERSITY   (Sweden)

^b LUND UNIVERSITY   (Sweden)

^c UNIVERSITY OF GLASGOW   (United Kingdom)

^d NORWEGIAN UNIVERSITY OF SCIENCE AND TECHNOLOGY   (Norway)

^e GEOLOGICAL SURVEY OF NORWAY   (Norway)

^f UNIVERSITY OF LAUSANNE   (Switzerland)

^g ROYAL NETHERLANDS METEOROLOGICAL INSTITUTE KNMI   (Netherlands)

^h PURDUE UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ALUMINUM; AUTOCHTHON; BERYLLIUM ISOTOPE; CHEMICAL WEATHERING; CONCENTRATION (COMPOSITION); EROSION RATE; GLACIOISOSTASY; MOUNTAIN REGION; REGOLITH; SECONDARY MINERAL; SPATIAL VARIATION; TEMPORAL VARIATION;

SCANDES MOUNTAINS; SWEDEN;

EID: 84941338385     PISSN: 21966311     EISSN: 2196632X     Source Type: Journal    
DOI: 10.5194/esurf-2-383-2014     Document Type: Article

References (108)

1. Anderson, R. S.: Near-surface thermal profiles in alpine bedrock: implications for the frost-weathering of rock, Arct. Alpine Res., 30, 362-372, 1998.
2. Anderson, R. S.: Modeling the tor-dotted crests, bedrock edges, and parabolic profiles of high alpine surfaces of the Wind River Range, Wyoming, Geomorphol., 46, 35-58, 2002.
3. André, M. F.: Rates of postglacial rock weathering on glacially scoured outcrops (Abisko-Riksgränsen area, 68 N), Geograf. Annal., 84A, 139-150, 2002.
4. André, M. F.: Do periglacial landscapes evolve under periglacial conditions?, Geomorphology, 52, 149-1164, 2003.
5. André, M. F., Hall, K., Bertran, P., and Arocena, J.: Stone runs in the Falkland Islands: Periglacial or tropical?, Geomorphol., 95, 524-543, 2008.
6. Bain, D. C., Mellor, A.,Wilson, M. J., and Duthie, D. M. L.: Chemical and mineralogical weathering rates and processes in an upland granitic till catchment in Scotland. Water, Air Soil Pollut., 73, 11-27, 1994.
7. Balco, G., Stone, J. O., Lifton, N. A., and Dunai, T. J.: A complete and easily accessible means of calculating surface exposure ages or erosion rates from 10Be and 26Al measurements, Quaternary Geochronol., 3, 174-195, 2008.
8. Ballantyne, C. K.: Age and significance of mountain-top detritus, Permafrost Perigl. Process., 9, 327-345, 1998.
9. Ballantyne, C. K.: A general model of autochthonous blockfield evolution, Permafrost Perigl. Process. 21, 289-300, 2010.
10. Ballantyne, C. K. and Harris, C.: The Periglaciation of Great Britain, Cambridge University Press, Cambridge, 1994.
11. Ballantyne, C. K., McCarroll, D., Nesje, A., Dahl, S. O., and Stone, J. O.: The last ice sheet in north-west Scotland: Reconstruction and implications, Quaternary Sci. Rev. 17, 1149-1184, 1998.
12. Berthling, I. and Etzelmüller, B.: The concept of cryo-conditioning in landscape evolution, Quaternary Res., 75, 378-384, 2011.
13. Bierman, P. R., Marsella, K. A., Patterson, C., Davis, P. T., and Caffee, M.: Mid-Pleistocene cosmogenic minimum-age limits for pre-Wisconsinan glacial surfaces in southwestern Minnesota and southern Baffin Island: a multiple nuclide approach, Geomorphology, 27, 25-39, 1999.
14. Bintanja, R., van de Wal, R. S. W., and Oerlemans, J.: Global ice volume variations through the last glacial cycle simulated by a 3-D ice-dynamical model, Quaternary Int., 95-96, 11-23, 2002.
15. Bintanja, R., van de Wal, R. S. W., and Oerlemans, J.: Modelled atmospheric temperatures and global sea levels over the past million years, Nature, 437, 125-128, 2005.
16. Boelhouwers, J. C.: New perspectives on autochthonous blockfield development, Polar Geogr., 28, 133-146, 2004.
17. Boelhouwers, J., Holness, S., Meiklejohn, I., and Sumner, P.: Observations on a blockstream in the vicinity of Sani Pass, Lesotho Highlands, southern Africa, Permafrost Perigl. Process., 13, 251-257, 2002.
18. Brindley, G. W. and Brown, G.: Crystal Structures of Clay Minerals and their X-ray Identification, Mineralogical Society, London, 495 pp., 1980.
19. Briner, J. P., Miller, G. H., Davis, P. T., Bierman, P. R., and Caffee, M.: Last Glacial Maximum ice sheet dynamics in Arctic Canada inferred from young erratics perched on ancient tors, Quaternary Sci. Rev., 22, 437-444, 2003.
20. Burkins, D. L., Blum, J. D., Brown, K., Reynolds, R. C., and Erel, Y.: Chemistry and mineralogy of a granitic, glacial soil chronosequence, Sierra Nevada Mountains, California, Chem. Geol., 162, 1-14, 1999.
21. Caine, N.: The Blockfields of Northeastern Tasmania. Publication G/6, Department of Geography, Research School of Pacific Studies, The Australian National University, Canberra, 127 pp., 1968.
22. Charbit, S., Ritz, C., Philippon, G., Peyaud, V., and Kageyama, M.: Numerical reconstructions of the Northern Hemisphere ice sheets through the last glacial-interglacial cycle, Clim. Past, 3, 15-37, doi:10.5194/cp-3-15-2007, 2007.
23. Child, D., Elliott, G., Mifsud, C., Smith, A. M., and Fink, D.: Sample processing for earth science studies at ANTARES. Nuclear Instruments and Methods in Physics Research Section B, Beam Interactions with Materials and Atoms, 172, 856-860, 2000.
24. Clapperton, C. M.: Further observations on the stone runs of the Falkland Islands, Biuletyn Peryglacjalny, 24, 211-217, 1975.
25. Cockburn, H. A. P. and Summerfield, M. A.: Geomorphological applications of cosmogenic isotope analysis, Progr. Phys. Geogr., 28, 1-42, 2004.
26. Dahl, R.: Block fields, weathering pits and tor-like forms in the Narvik mountains, Nordland, Norway, Geograf. Annal., 48A, 55-85, 1966.
27. Dahlgren, R. A., Boettinger, J. L., Huntington, G. L., and Amundson, R. G.: Soil development along an elevational transect in the western Sierra Nevada, California, Geoderma, 78, 207-236, 1997.
28. Dixon, J. C. and Thorn, C. E.: Chemical weathering and landscape development in mid-latitude alpine environments, Geomorphology, 67, 127-145, 2005.
29. Dredge, L.: Breakup of limestone bedrock by frost shattering and chemical weathering, Eastern Canadian Arctic, Arctic Alpine Res., 24, 314-323, 1992.
30. Dredge, L. A.: Age and origin of upland block fields on Melville Peninsula, eastern Canadian Arctic, Geograf. Annal., 82A, 443-454, 2000.
31. Ericson, K.: Geomorphological surfaces of different age and origin in granite landscapes: An evaluation of the Schmidt hammer test, Earth Surf. Process. Landform., 29, 495-509, 2004.
32. Eriksson, B.: Data rörandeSveriges temperaturklimat (Data concerning the air temperature of Sweden). SMHI Reports, Meteorology and Climatology, RMK 39, 1982.
33. Fabel, D., Stroeven, A. P., Harbor, J., Kleman, J., Elmore, D., and Fink, D.: Landscape preservation under Fennoscandian ice sheets determined from in situ produced 10Be and 26Al, Earth Planet. Sci. Lett., 201, 397-406, 2002.
34. Fjeldskaar, W., Lindholm, C., Dehls, J. F., and Fjeldskaar, I.: Postglacial uplift, neotectonics and seismicity in Fennoscandia, Quaternary Sci. Rev., 19, 1413-1422, 2000.
35. Fjellanger, J., Sørbel, L., Linge, H., Brook, E. J., Raisbeck, G. M., and Yiou, F.: Glacial survival of blockfields on the Varanger Peninsula, northern Norway, Geomorphology, 82, 255-272, 2006.
36. Fredén, C. (Ed): National Atlas of Sweden: Land and soils, Sveriges Nationalatlas, Vällingby, 208 pp., 2002.
37. Gardner, L. R.: Long-term isovolumetric leaching of aluminum from rocks during weathering: implications for the genesis of saprolite, Catena, 19, 521-537, 1992.
38. Glasser, N. and Hall, A.: Calculating Quaternary glacial erosion rates in northeast Scotland, Geomorphology, 20, 29-48, 1997.
39. Goldstein, J., Newbury, D. E., Joy, D. C., Lyman, C. E., Echlin, P., Lifshin, E., Sawyer, L. C., and Michael, J. R.: Scanning Electron Microscopy and X-ray Microanalysis, 3rd Edn., Kluwer Academic/Plenum Publishers, New York, 689 pp., 2003.
40. Goodfellow, B.W.: Relict non-glacial surfaces in formerly glaciated landscapes, Earth-Sci. Rev., 80, 47-73, 2007.
41. Goodfellow, B. W.: A granulometry and secondary mineral fingerprint of chemical weathering in periglacial landscapes and its application to blockfield origins, Quaternary Sci. Rev., 57, 121-135, 2012.
42. Goodfellow, B. W., Stroeven, A. P., Hättestrand, C., Kleman, J., and Jansson, K. N.: Deciphering a non-glacial/glacial landscape mosaic in the northern Swedish mountains, Geomorphology, 93, 213-232, 2008.
43. Goodfellow, B. W., Fredin, O., Derron, M.-H., and Stroeven, A. P.: Weathering processes and Quaternary origin of an alpine blockfield in Arctic Sweden, Boreas, 38, 379-398, 2009.
44. Granger, D. E., Riebe, C. S., Kirchner, J. W., and Finkel, R. C.: Modulation of erosion on steep granitic slopes by boulder armoring, as revealed by cosmogenic 26Al and 10Be, Earth Planet. Sci. Lett., 86, 269-281, 2001.
45. Green, C. P. and Eden, M. J.: Gibbsite in the weathered Dartmoor granite, Geoderma, 6, 315-317, 1971.
46. Grudd, H. and Schneider, T.: Air temperature at Tarfala Research Station 1946-1995, Geograf. Annal., 78A, 115-119, 1996.
47. Hales, T. C. and Roering, J. J.: Climatic controls on frost cracking and implications for the evolution of bedrock landscapes, J. Geophys. Res., 112, F02033, doi:10.1029/2006JF000616, 2007.
48. Hall, A. M. and Phillips, W. M.: Weathering pits as indicators of the relative age of granite surfaces in the Cairngorm Mountains, Scotland, Geograf. Annal., 88A, 135-150, 2006.
49. Hättestrand, C. and Stroeven, A. P.: A relict landscape in the centre of Fennoscandian glaciation; geomorphological evidence of minimal Quaternary glacial erosion, Geomorphology, 44, 127-143, 2002.
50. Hopkinson, C. and Ballantyne, C. K.: Age and Origin of Blockfields on Scottish Mountains, Scottish Geogr. J., 130, 116-141, 2014.
51. Isaksen, K., Holmlund, P., Sollid, J. L., and Harris, C.: Three deep alpine-permafrost boreholes in Svalbard and Scandinavia, Permafrost Perigl. Process., 12, 13-25, 2001.
52. Isaksen, K., Sollid, J. L., Holmlund, P., and Harris, C.: Recent warming of mountain permafrost in Svalbard and Scandinavia, J. Geophys. Res., 112, F02S04, doi:10.1029/2006JF000522, 2007.
53. Ives, J. D.: Block fields, associated weathering forms on mountain tops and the Nunatak hypothesis, Geograf. Annal., 4, 220-223, 1966.
54. Ives, J. D.: Biological refugia and the nunatak hypothesis, in: Arctic and Alpine Environments, edited by: Ives, J. D. and Barry, R. G., Methuen, London, 605-636, 1974.
55. Jansson, K. N., Stroeven, A. P., Alm, G., Dahlgren, K. I. T., Glasser, N. F., and Goodfellow, B. W.: Using a GIS filtering approach to replicate patterns of glacial erosion, Earth Surf. Process Landf., 36, 408-418, 2011.
56. Kauffman, G., Wu, P., and Li, G.: Glacial isostatic adjustment in Fennoscandia for a laterally heterogenous earth, Geophys. J. Int., 143, 262-273, 2000.
57. Kleman, J. and Stroeven, A. P.: Preglacial surface remnants and Quaternary glacial regimes in northwestern Sweden, Geomorphology, 19, 35-54, 1997.
58. Kleman, J., Stroeven, A. P., and Lundqvist, J.: Patterns of Quaternary ice sheet erosion and deposition in Fennoscandia and a theoretical framework for explanation, Geomorphology, 97, 73-90, 2008.
59. Kohl, C. P. and Nishiizumi, K.: Chemical isolation of quartz for measurement of in situ-produced cosmogenic nuclides, Geochim. Cosmochim. Acta, 56, 3586-3587, 1992.
60. Lal, D.: Cosmic ray labeling of erosion surfaces: in situ nuclide production rates and erosion models, Earth Planet. Sci. Lett., 104, 424-439, 1991.
61. Lambeck, K., Purcell, A., Funder, S., Kjoer, K. H., Larsen, E., and Möller, P.: Constraints on the Late Saalian to early Middle Weichselian ice sheet of Eurasia from field data and rebound modeling, Boreas, 35, 539-575, 2006.
62. Le Meur, E. and Huybrechts, P.: A comparison of different ways of dealing with isostasy: examples from modelling the Antarctic ice sheet during the last glacial cycle, Ann. Glaciol., 23, 309-317, 1996.
63. Li, Y., Fabel, D., Stroeven, A. P., and Harbor, J.: Unraveling complex exposure-burial histories of bedrock surfaces under ice sheets by integrating cosmogenic nuclide concentrations with climate proxy records, Geomorphology, 99, 139-149, 2008.
64. Lidmar-Bergström, K.: A long-term perspective on glacial erosion, Earth Surf. Process. Landf., 22, 297-306, 1997.
65. Lisiecki, L. E. and Raymo, M. E.: A Pliocene-Pleistocene stack of 57 globally distributed benthic 18O records, Paleooceanography, 20, PA1003, doi:10.1029/2004PA001071, 2005.
66. Marquette, G. C., Gray, J. T., Gosse, J. C., Courchesne, F., Stockli, L., MacPherson, G., and Finkel, R.: Felsenmeer persistence under non-erosive ice in the Torngat and Kaumajet mountains, Quebec and Labrador, as determined by soil weathering and cosmogenic nuclide exposure dating, Can. J. Earth Sci., 41, 19-38, 2004.
67. May, H. M., Helmke, P. A., and Jackson, M. L.: Gibbsite solubility and thermodynamic properties of hydroxy-aluminum ions in aqueous solution at 25 °C, Geochim. Cosmochim. Acta, 43, 861-868, 1979.
68. McKeague, J. A., Grant, D. R., Kodama, H., Beke, G. J., andWang, C.: Properties and genesis of a soil and the underlying gibbsitebearing saprolite, Cape Breton Island, Canada, Can. J. Earth Sci., 20, 37-48, 1983.
69. Meunier, A., Sardini, P., Robinet, J. C., and Prêt, D.: The petrography of weathering processes: facts and outlooks, Clay Min., 42, 415-435, 2007.
70. Milne, G. A., Mitrovica, J. X., Scherneck, H.-G., Davis, J. L., Johansson, J. M., Koivula, H., and Vermeer, M.:. Continuous GPS measurements of postglacial adjustment in Fennoscandia: 2. Modelling results, J. Geophys. Res., 109, 1-18, 2004.
71. Moore, D. M. and Reynolds, R. C.: X-ray Diffraction and the Identification and Analysis of Clay Minerals, 2nd Edn., University Press, Oxford, 378 pp., 1997.
72. Nesbitt, H. W. and Young, G. M.: Prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations, Geochimi. Cosmochim. Acta, 48, 1523-1534, 1984.
73. Nesje, A. and Whillans, I. M.: Erosion of Sognefjord, Norway, Geomorphology, 9, 33-45, 1994.
74. Nesje, A., Dahl, S. O., Anda, E., and Rye, N.: Block fields in southern Norway: Significance for the Late Weichselian ice sheet, Norsk Geologisk Tidsskrift, 68, 149-169, 1988.
75. Nielsen, S. B., Gallagher, K., Leighton, C., Balling, N., Svenningsen, L., Jacobsen, B. H., Thomsen, E., Nielsen, O. B., Heilmann-Clausen, C., Egholm, D. L., Summerfield, M. A., Clausen, O. R., Piotrowski, J. A., Thorsen, M. R., Huuse, M., Abrahamsen, N., King, C., and Holger Lykke-Andersen, H.: The evolution of western Scandinavian topography: a review of Neogene uplift versus the ICE (isostasy-climate-erosion) hypothesis, J. Geodynam., 47, 72-95, 2009.
76. Nishiizumi, K.: Preparation of 26Al AMS standards, Nuclear Instrume. Methods Phys. Res. B, 223-224, 388-392, 2004.
77. Nishiizumi, K., Imamura, M., Caffee, M. W., Southern, J. R., Finkel, R. C., and McAninch, J.: Absolute calibration of 10Be AMS standards, Nuclear Instrum. Methods Phys. Res. B, 258, 403-413, 2007.
78. Paasche, Ø., Strømsøe, J. R., Dahl, S. O., and Linge, H.: Weathering characteristics of arctic islands in northern Norway, Geomorphology, 82, 430-452, 2006.
79. Pedersen, V. K. and Egholm, D. L.: Glaciations in response to climate variations preconditioned by evolving topography, Nature, 493, 206-2010, 2013.
80. Peltier, W. R.: Ice age paleotopography, Science, 265, 195-201, 1994.
81. Peltier, W. R.: Global glacial isostasy and the surface of the ice-age Earth: the ICE-5G (VM2) Model and GRACE, Ann. Rev. Earth Planet. Sci., 32, 111-149, 2004.
82. Phillips, W. M., Hall, A. M., Mottram, R., Fifield, L. K., and Sugden, D.: Cosmogenic 10Be and 26Al exposure ages of tors and erratics, Cairngorm Mountains, Scotland: Timescales for the development of a classic landscape of selective linear glacial erosion, Geomorphology, 73, 224-245, 2006.
83. Potter, N. and Moss, J. H.: Origin of the Blue Rocks block field and adjacent deposits, Berks County, Pennsylvania, Geol. Soc. Am. Bull., 79, 255-262, 1968.
84. Rea, B. R.: Blockfields (Felsenmeer), in: The Encyclopedia of Quaternary Science, edited by: Elias, S. A., Vol. 3, Elsevier, Amsterdam, 523-534, 2013.
85. Rea, B. R., Whalley, B., Rainey, M. M., and Gordon, J. E.: Blockfields, old or new? Evidence and implications from some plateaus in northern Norway, Geomorphology, 15, 109-121, 1996.
86. Refsnider, K. A. and Miller, G. H.: Ice-sheet erosion and the stripping of Tertiary regolith from Baffin Island, eastern Canadian Arctic, Quaternary Sci. Rev., 67, 176-189, 2013.
87. Reynolds, R. C.: Clay mineral formation in an alpine environment, Clays Clay Mineral., 19, 361-374, 1971.
88. Small, E. E., Anderson, R. S., Repka, J. L., and Finkel, R.: Erosion rates of alpine bedrock summit surfaces deduced from in situ 10Be and 26Al, Earth Planet. Sci. Lett., 150, 413-425, 1997.
89. Small, E. E., Anderson, R. S., and Hancock, G. S.: Estimates of the rate of regolith production using 10Be and 26Al from an alpine hillslope, Geomorphology, 27, 131-150, 1999.
90. Staiger, J. K.W., Gosse, J. C., Johnson, J. V., Fastook, J., Gray, J. T., Stockli, D. F., Stockli, L., and Finkel, R.: Quaternary relief generation by polythermal glacier ice, Earth Surf. Process. Landform., 30, 1145-1159, 2005.
91. Steer, P., Huismans, R. S., Valla, P. G., Gac, S., and Herman, F.: Bimodal Plio-Quaternary glacial erosion of fjords and low-relief surfaces in Scandinavia, Nat. Geosci., 5, 635-639, 2012.
92. Steffen, H. and Kauffman, G.: Glacial isostatic adjustment of Scandinavia and northwestern Europe and the radial viscosity structure of the Earth's mantle, Geophys. J. In., 163, 801-812, 2005.
93. Steffen, H., Kauffman, G., and Wu, P.: Three-dimensional finite-element modeling of the glacial isostatic adjustment in Fennoscandia, Earth Planet. Sci. Lett., 250, 358-375, 2006.
94. Stone, J. O.: Air pressure and cosmogenic isotope production, J. Geophys. Res., 105, 23753-23759, 2000.
95. Stroeven, A. P., Fabel, D., Hattestrand, C., and Harbor, J.: A relict landscape in the centre of Fennoscandian glaciation; cosmogenic radionuclide evidence of tors preserved through multiple glacial cycles, Geomorphology, 44, 145-154, 2002.
96. Stroeven, A. P., Harbor, J., Fabel, D., Kleman, J., Hättestrand, C. Elmore, D., Fink, D., and Fredin, O.: Slow, patchy landscape evolution in northern Sweden despite repeated ice-sheet glaciation, Geol. Soc. Am. Special Paper, 398, 387-396, 2006.
97. Strømsøe, J. R. and Paasche, Ø.: Weathering patterns in high-latitude regolith, J. Geophys. Res., 116, F03021, doi:10.1029/2010JF001954, 2011.
98. Stumm, W. and Morgan, J. J.: Aquatic Chemistry, 2nd Edn., John Wiley and Sons, New York, 1981.
99. Sugden, D. E.: The selectivity of glacial erosion in the Cairngorm Mountains, Scotland, Trans. Institute of British Geographers, 45, 79-92, 1968.
100. Sugden, D. E.: Landscapes of glacial erosion in Greenland and their relationship to ice, topographic and bedrock conditions, in: Progress in Geomorphology: Papers in honour of D.L. Linton, edited by: Brown, E. H. and Waters, R. S., Institute of British Geographers Special Publication, Vol. 7, 177-195, 1974.
101. Sugden, D. E. and Watts, S. H.: Tors, felsenmeer, and glaciation in northern Cumberland Peninsula, Baffin Island, Can. J. Earth Sci., 14, 2817-2823, 1977.
102. Sumner, P. D. and Meiklejohn, K. I.: On the development of autochthonous blockfields in the grey basalts of sub-Antarctic Marion Island, Polar Geogr., 28, 120-132, 2004.
103. US Department of Agriculture: Soil Survey Manual, Agricultural Handbook No. 18. Government Printing Office, Washington D.C., 532 pp., 1993.
104. Walder, J. S. and Hallet, B.: A theoretical model of the fracture of rock during freezing, Geol. Soc. Am. Bull., 96, 336-346, 1985.
105. Watanabe, T., Funakawa, S., and Kosaki, T.: Distribution and formation conditions of gibbsite in the upland soils of humid Asia: Japan, Thailand and Indonesia, 19thWorld Congress of Soil Science, Soil Solutions for a Changing World, 1-6 August 2010, Brisbane, Australia, 17-20, 2010.
106. Wesolowski, D. J. and Palmer, D. A.: Aluminum speciation and equilibria in aqueous solution: V. Gibbsite solubility at 50 °C and pH 3-9 in 0.1 molal NaCl solutions (a general model for aluminum speciation; analytical methods), Geochim. Cosmochim. Acta, 58, 2947-2969, 1994.
107. Whalley, W. B., Rea, B. R., and Rainey, M.: Weathering, blockfields, and fracture systems and the implications for long-term landscape formation: some evidence from Lyngen and Øksfordjøkelen areas in north Norway, Polar Geogr., 28, 93-119, 2004.
108. White, A. F., Blum, A. E., Schulz, M. S., Vivit, D. V., Stonestrom, D. A., Larsen, M., Murphy, S. F., and Eberl, D.: Chemical weathering in a tropical watershed, Luquillo Mountains, Puerto Rico: I. Long-term versus short-term weathering fluxes, Geochim. Cosmochim. Acta, 62, 209-226, 1998.