Jökull

Ataaseq assigiiaat ilaat

Jökull - 01.12.1984, Qupperneq 97

Jökull - 01.12.1984, Qupperneq 97
In northwestern Iceland, normal faults are more common and tend to have larger throws than in eastern Iceland. The number of dykes with a significant associated vertical displacement is, however, similar. While the total length of profiles in northwestern and eastern Iceland is roughly similar, only 19 normal faults were observed in eastern Iceland, compared with 68 normal faults observed in northwestern Iceland. Also, the throw of faults in eastern Iceland is 0.5—8.0 m with an average of 2.7 m, whereas the throw of the faults in northwestern Iceland is 0.5—25.0 m with an average of 5.3 m. Neither the average thickness nor the thickness distribution of the dykes in northwestern Iceland can be related to the altitude of the profiles (Table 1, Fig. 9), nor to the location of the profiles in the research areas (Fig. 2). I suggest that the variation in average thickness and thick- ness distribution may be explained by the diffe- rent lithology of the country rock. Difference in lithology may be reflected in difference in various mechanical factors, the most important of which is Youngs’s modulus, E. Dykes dissecting layers of high E tend to be thin, but tend to be thick when dissecting layers of low E. Thus the average thickness of dykes dissecting layers of high E can be much less than the average thickness of these same dykes where they dissect layers of low E (Gudmundsson 1984). Layers of high or low E may be expected to be randomly distributed throughout the lava pile, thereby explaining the lack of correlation between thickness of dykes and the altitude or location of the corresponding dyke profiles. In general, the dyke orientation obtained by field measurements in the present study is similar to the orientation that Sigurdsson (1967) obtained from air photographs of the same part of northwestern Iceland. The small difference between the results can be explained by the diffe- rent method used and by the different areas used to make the rose diagrams. Both these factors result in somewhat different “samples“ being used in Sigurdsson’s study as compared with the present study. ACKNOWLEDGEMENTS I thank NevilleJ. Price and Kristján Saemunds- son for critical comments on an earlier version of the manuscript. Financial support was provided by the National Energy Authority and by the Ice- landic Science Foundation. REFERENCES Björnsson, A., G. Johnsen, S. Sigurdsson, G. Thorbergsson and E. Tryggvason 1979: Rifting of the plate boundary in north Iceland 1975— 1978. J. Geophys. Res. 84: 3029-3038. Bullen, K. E. 1963: An Introduction to the Theory of Seismology. C. U. P., Cambridge, 381 pp. Friedrich, W. 1966: Zur Geologie von Brjáns- laekur (NW-Island) unter besonderer Beriick- sichtigung der fossilen Flora. Geol. Inst. d. Univ. Koln, Sonderveröffentlichungen 10: 108 pp. Gudmundsson, A. 1983a: Form and dimensions of dykes in eastern Iceland. Tectonophysics 95: 295-307. Gudmundsson A. 1983b: Stress estimates from the length/width ratios of fractures. J. Struct. Geol. 5: 623-626. Gudmundsson, A. 1984: A Study of Dykes, Fis- sures and Faults in Selected Areas of Iceland. Unpubl. Ph. D. thesis, Univ. of London. Haimson, B. C. and Rummel, F. 1982: Hydrofrac- turing stress measurements in the Iceland re- search drilling project drill hole at Reydar- fjördur, Iceland. J. Geophys. Res. 87: 6631-6649. Jaeger, J. C. 1961: The cooling of irregularly shaped igneous bodies. Am. J. Sci. 259: 721 — 734. Jaeger, J. C. 1968: Cooling and solidification of igneous rocks. In: H. H. Hess (Ed.). Basalts. Vol. 2, Interscience (Wiley), New York, pp. 503-536. Jeffreys, H. 1976: The Earth. C. U. P., Cam- bridge, 574 pp. Kristjánsson, L., R. Patzold and J. Preston 1975: The paleomagnetism and geology of the Pat- reksfjördur-Arnarfjördur region of northwest Iceland. Tectonophysics 25: 201—216. McDougall, /., L. Kristjánsson and K. Saemundsson 1984: Magnetostratigraphy and geochronology of northwest Iceland. J. Geo- phys. Res. (in press). Price, N. J. 1966: Fault and Joint Development in Brittle and Semibrittle Rock. Pergamon, Oxford, 176 pp. JÖKULL 34. ÁR 95
Qupperneq 1
Qupperneq 2
Qupperneq 3
Qupperneq 4
Qupperneq 5
Qupperneq 6
Qupperneq 7
Qupperneq 8
Qupperneq 9
Qupperneq 10
Qupperneq 11
Qupperneq 12
Qupperneq 13
Qupperneq 14
Qupperneq 15
Qupperneq 16
Qupperneq 17
Qupperneq 18
Qupperneq 19
Qupperneq 20
Qupperneq 21
Qupperneq 22
Qupperneq 23
Qupperneq 24
Qupperneq 25
Qupperneq 26
Qupperneq 27
Qupperneq 28
Qupperneq 29
Qupperneq 30
Qupperneq 31
Qupperneq 32
Qupperneq 33
Qupperneq 34
Qupperneq 35
Qupperneq 36
Qupperneq 37
Qupperneq 38
Qupperneq 39
Qupperneq 40
Qupperneq 41
Qupperneq 42
Qupperneq 43
Qupperneq 44
Qupperneq 45
Qupperneq 46
Qupperneq 47
Qupperneq 48
Qupperneq 49
Qupperneq 50
Qupperneq 51
Qupperneq 52
Qupperneq 53
Qupperneq 54
Qupperneq 55
Qupperneq 56
Qupperneq 57
Qupperneq 58
Qupperneq 59
Qupperneq 60
Qupperneq 61
Qupperneq 62
Qupperneq 63
Qupperneq 64
Qupperneq 65
Qupperneq 66
Qupperneq 67
Qupperneq 68
Qupperneq 69
Qupperneq 70
Qupperneq 71
Qupperneq 72
Qupperneq 73
Qupperneq 74
Qupperneq 75
Qupperneq 76
Qupperneq 77
Qupperneq 78
Qupperneq 79
Qupperneq 80
Qupperneq 81
Qupperneq 82
Qupperneq 83
Qupperneq 84
Qupperneq 85
Qupperneq 86
Qupperneq 87
Qupperneq 88
Qupperneq 89
Qupperneq 90
Qupperneq 91
Qupperneq 92
Qupperneq 93
Qupperneq 94
Qupperneq 95
Qupperneq 96
Qupperneq 97
Qupperneq 98
Qupperneq 99
Qupperneq 100
Qupperneq 101
Qupperneq 102
Qupperneq 103
Qupperneq 104
Qupperneq 105
Qupperneq 106
Qupperneq 107
Qupperneq 108
Qupperneq 109
Qupperneq 110
Qupperneq 111
Qupperneq 112
Qupperneq 113
Qupperneq 114
Qupperneq 115
Qupperneq 116
Qupperneq 117
Qupperneq 118
Qupperneq 119
Qupperneq 120
Qupperneq 121
Qupperneq 122
Qupperneq 123
Qupperneq 124
Qupperneq 125
Qupperneq 126
Qupperneq 127
Qupperneq 128
Qupperneq 129
Qupperneq 130
Qupperneq 131
Qupperneq 132
Qupperneq 133
Qupperneq 134
Qupperneq 135
Qupperneq 136
Qupperneq 137
Qupperneq 138
Qupperneq 139
Qupperneq 140
Qupperneq 141
Qupperneq 142
Qupperneq 143
Qupperneq 144
Qupperneq 145
Qupperneq 146
Qupperneq 147
Qupperneq 148
Qupperneq 149
Qupperneq 150
Qupperneq 151
Qupperneq 152
Qupperneq 153
Qupperneq 154
Qupperneq 155
Qupperneq 156
Qupperneq 157
Qupperneq 158
Qupperneq 159
Qupperneq 160
Qupperneq 161
Qupperneq 162
Qupperneq 163
Qupperneq 164
Qupperneq 165
Qupperneq 166
Qupperneq 167
Qupperneq 168
Qupperneq 169
Qupperneq 170
Qupperneq 171
Qupperneq 172
Qupperneq 173
Qupperneq 174
Qupperneq 175
Qupperneq 176
Qupperneq 177
Qupperneq 178
Qupperneq 179
Qupperneq 180
Qupperneq 181
Qupperneq 182
Qupperneq 183
Qupperneq 184
Qupperneq 185
Qupperneq 186
Qupperneq 187
Qupperneq 188
Qupperneq 189
Qupperneq 190
Qupperneq 191
Qupperneq 192
Qupperneq 193
Qupperneq 194
Qupperneq 195
Qupperneq 196

x

Jökull

Direct Links

Hvis du vil linke til denne avis/magasin, skal du bruge disse links:

Link til denne avis/magasin: Jökull
https://timarit.is/publication/1155

Link til dette eksemplar:

Link til denne side:

Link til denne artikel:

Venligst ikke link direkte til billeder eller PDfs på Timarit.is, da sådanne webadresser kan ændres uden advarsel. Brug venligst de angivne webadresser for at linke til sitet.