Jökull


Jökull - 01.12.1987, Side 79

Jökull - 01.12.1987, Side 79
Fig. 18. A thrust fault in the Asbakkar diamicton at 4975 m. The arrow points at a body of sand which has been overturned by fault drag. The man pointing at the fault is 1.85 m high. 18. mynd. Þrýsti-misgengi við 4975 m. glacigenic subaquatic debris flows, to form proglacial shoals or banks. The relative sea level was probably 80-90 m above the present level. Beyond the ice-mar- ginal zone, glaciomarine sedimentation continued with strong influxes of meltwater underflows and subaquatic debris flows. Continued advance of the glacier (stage C) caused large-scale glaciotectonic deformations. The gla- cier successively overran the whole basin (stage D). Around 11.700 BP the glacier retreated to a position somewhere north of the Melabakkar-Asbakkar section (stage E), in the course of retreat depositing the esker fan facies of the Látrar beds. The sea level was high, and the rhythmic glaciomarine facies of the Látrar beds, supporting a limited mollusc population, accumulated from suspended fines, underflows and ice rafting. Some time after 11.400 BP the basin was re-invaded by a glacier advancing out of the Borgarfjördur main valley (stage F). In connection with this readvance, lodgement till (the Melar diamicton) and ice-proximal delta sedi- ments (the Landhólmi sands) were deposited. The rela- tive sea level was above 30 m above the present during the delta deposition. There is evidence in the cliffs of the glacier advancing about halfway across the section to- wards south, but it may have advanced further. A trans- verse ridge of subaquatic outwash (the Asgil gravels) marks the position of the ice margin during some stage in its retreat (stage G). During stage H, some time prior to 10.000 BP, the glacier retreated from the coastal areas and the sea transgressed the isostatically depressed lowlands. Re- Fig. 19. Stages in the development of the Melabakkar- Ásbakkarcoastalcliffs. Legend: (UF) underflows, (TC) tidal currents, (MS) meltwater streams, (DF) subaquat- icglacigenicdebris flows, (1) bedrock, (2) Ásbakkar dia- micton, (3) Ás beds, (4) Látrareskerfanfacies, (5) Látr- ar glaciomarine silts and sands, (6) Melar diamicton, (7) Landhólmi sands, (8) Ásgil gravels, (9) Melabakkar silts and sands, (10) Melagil gravels and sands. See text for further discussion. 19. mynd. Skeið í þróun Mela- og Ásbakka. Nánari útskýringar í ágripi. 77
Side 1
Side 2
Side 3
Side 4
Side 5
Side 6
Side 7
Side 8
Side 9
Side 10
Side 11
Side 12
Side 13
Side 14
Side 15
Side 16
Side 17
Side 18
Side 19
Side 20
Side 21
Side 22
Side 23
Side 24
Side 25
Side 26
Side 27
Side 28
Side 29
Side 30
Side 31
Side 32
Side 33
Side 34
Side 35
Side 36
Side 37
Side 38
Side 39
Side 40
Side 41
Side 42
Side 43
Side 44
Side 45
Side 46
Side 47
Side 48
Side 49
Side 50
Side 51
Side 52
Side 53
Side 54
Side 55
Side 56
Side 57
Side 58
Side 59
Side 60
Side 61
Side 62
Side 63
Side 64
Side 65
Side 66
Side 67
Side 68
Side 69
Side 70
Side 71
Side 72
Side 73
Side 74
Side 75
Side 76
Side 77
Side 78
Side 79
Side 80
Side 81
Side 82
Side 83
Side 84
Side 85
Side 86
Side 87
Side 88
Side 89
Side 90
Side 91
Side 92
Side 93
Side 94
Side 95
Side 96
Side 97
Side 98
Side 99
Side 100
Side 101
Side 102
Side 103
Side 104
Side 105
Side 106
Side 107
Side 108
Side 109
Side 110
Side 111
Side 112
Side 113
Side 114
Side 115
Side 116

x

Jökull

Direkte link

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.