Seismic refraction measurements of the basalt lavas of the Faeroe Islands

Pálmason, Guðmundur

doi:10.1016/0040-1951(65)90002-8

Cited by 51 publications

(45 citation statements)

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“…Depth scale is schematic. Proportion of succession exposed on the Faeroes is indicated; remainder of Lower Series of basalts is inferred from refraction surveys (Prllmason 1965). Black band separating Lower and Middle Series represents 10m of coal-bearing sediments, overlain by lOOm of tuffs and agglomerate.…”

Section: (A)mentioning

confidence: 99%

Early opening history of the North Atlantic ? I. Structure and origin of the Faeroe?Shetland Escarpment

et al. 1983

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Marine geophysical surveys show that the Escarpment is the buried feather-edge of a thick pile of flood basalts of early Eocene age, overlying a thinner, more widespread layer of basalts of late Palaeocene age. The Escarpment does not, therefore, define the continent-ocean boundary in the southern Norwegian Sea, but instead marks the contemporary shoreline separating terrestrially erupted basalt flows in the north from a restricted shallow-water shelf to the south. The basalts overlie 5-6 km of Mesozoic sediments, which have completely buried a large conical flat-topped seamount of similar dimensions to Anton Dohrn and Rosemary Bank. We call this newly postulated body the Brendan seamount. The Mesozoic sediments are at least as old as early Cretaceous in age, therefore precluding the possibility that the mid-Cretaceous seafloor spreading episode (supposed by some to have created the Rockall Trough) could have also created the thin crust inferred to underlie the Faeroe-Shetland Trough and Mbre Basin.

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Section: (A)mentioning

confidence: 99%

Early opening history of the North Atlantic ? I. Structure and origin of the Faeroe?Shetland Escarpment

et al. 1983

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“…The upper part of the crust in Iceland has been studied extensively by refraction measurements [Palmason, 1963[Palmason, , 1967a. A characteristic layering has been found.…”

Section: Icelandmentioning

confidence: 99%

Microearthquake survey and the Mid-Atlantic Ridge in Iceland

Ward¹,

Pálmason²,

Drake³

1969

J. Geophys. Res.

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During the summer of 1967, three high-frequency, high-gain, and highly portable seismographs were operated at seventy-eight sites throughout Iceland. Over 990/0 of the more than 1000 events recorded were found to lie in nine regions with radii of less than about 5 km. Although most of the events were not greater than 4 km deep, six were of the order of 5 to 15 km deep, and one may have been as much as 40 km deep. One large earthquake swarm was recorded from Myrdalsjiikull in south-central Iceland, where four events less than magnitude 5 were reported by the U. S. Coast and Geodetic Survey (U.S.C.G.S.) in early 1967. No earthquake greater than magnitude 4.5 has been reported since 1958 from the other regions of high microseismicity, suggesting that these microearthquakes were not simply aftershocks. Three events of magnitude 4 to 5 did occur, however, in each of two seismic regions after the initial recording period. Thus, some of the microearthquakes may have been foreshocks. A close correspondence was found between areas of major hydrothermal activity and high microearthquake activity. The highest activity recorded was in the Krafla volcanic region in northeastern Iceland, which has not been active since 1746. This activity had a b value of 0.83 ± 0.16 over 1% units of magnitude. The focal mechanisms were consistently similar and gave a solution with one nearly vertical nodal plane striking north-south. Eight of the nine zones of microseismirity lie on an east-west line near 64·N. When considered in relation to adjoining active seismic zones, reported historic seismicity of Iceland, and the location of the mid-Atlantic ridge and areas of active rifting and volcanism, the existence of a transform fauIt is suggested, following the methods used by Sykes (1967) to outline such faults on the sea floor with larger earthquakes. Magnetic data and some geologic features support this hypothesis. Seismic refraction data are not in disagreement with it. Many of the tectonic features of Iceland do not, however, readily fit into this framework. If sea-floor spreading is active in Iceland, it is more complicated in detail than previously suggested.

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“…However, seismic refraction data provide some indications of the nature and character of the sub-volcanic succession, and information has also been compiled from various studies (e.g. Pálmason 1965;Richardson et al 1998;Smallwood & White 2002;White et al 2003;Bohnhoff & Makris 2004;Raum et al 2005) that intersect the chosen transect of this study (Figs 1-3) where important information such as e.g. the top of the crust has been plotted.…”

Section: Methodsmentioning

confidence: 99%

“…The refraction seismic lines of White et al (2003) and Raum et al (2005) cross the crustal transect in the Faroe Platform area in the central part of transect section 7 and in the northern part of transect section 8, and a pre-volcanic sedimentary layer, up to 2 km thick, has been inferred. In contrast, in the southern part of transect section 6, Richardson et al (1998) and Pálmason (1965) -who shot onshore refraction lines -did not interpret a pre-volcanic sedimentary layer, though their studies were more focused on defining the top of the basement.…”

Section: Stratigraphymentioning

confidence: 95%

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The stratigraphy and structure of the Faroese continental margin

Ólavsdóttir

Eidesgaard

Stoker

2016

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This paper presents a summary of the stratigraphy and structure of the Faroese region. As the Faroese area is mostly covered by volcanic material, the nature of the pre-volcanic geology remains largely unproven. Seismic refraction data provide some indications of the distribution of crystalline basement, which probably comprises Archaean rocks, with the overlying cover composed predominantly of Upper Mesozoic (Cretaceous?) and Cenozoic strata. The Cenozoic succession is dominated by the syn-break-up Faroe Islands Basalt Group, which crops out on the Faroe Islands (where it is up to 6.6 km thick) and shelf areas; post-break-up sediments are preserved in the adjacent deep-water basins, including the Faroe-Shetland Basin. Seismic interpretation of the post-volcanic strata shows that almost every sub-basin in the Faroe-Shetland Basin has been affected by structural inversion, particularly during the Miocene. These effects are also observed on the Faroe Platform, the Munkagrunnur Ridge and the Fugloy Ridge, where interpretation of lowgravity anomalies suggests a large-scale fold pattern. The structure of the Iceland-Faroe Ridge, which borders the NW part of the Faroe area, remains ambiguous. The generally thick crust, together with the absence of well-defined seawards-dipping reflectors, may indicate that much of it is underlain by continental material.

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Seismic refraction measurements of the basalt lavas of the Faeroe Islands

Cited by 51 publications

References 5 publications

Early opening history of the North Atlantic ? I. Structure and origin of the Faeroe?Shetland Escarpment

Early opening history of the North Atlantic ? I. Structure and origin of the Faeroe?Shetland Escarpment

Microearthquake survey and the Mid-Atlantic Ridge in Iceland

The stratigraphy and structure of the Faroese continental margin

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