Interpretation of the regional gravity and magnetic surveys of Wales, using shaded relief and Euler deconvolution techniques

McDonald, Andrew J.; Fletchert, C. J. N.; Carruthers, R.M.; Wilson, David Gordon; Evans, Russ

doi:10.1017/s0016756800021683

Cited by 12 publications

(8 citation statements)

References 18 publications

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“…Other aspects of data presentation and interpretation are discussed in McDonald et al (1992). Other aspects of data presentation and interpretation are discussed in McDonald et al (1992).…”

Section: Introductionmentioning

confidence: 99%

Some constraints on the form of the Welsh Basin from regional gravity and aeromagnetic data, with particular reference to Central Wales

Carruthers

Fletcher²,

McDonald³

et al. 1992

Geol. Mag.

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Gravity and aeromagnetic data sets provide systematic coverage over the whole of the Welsh Basin. Physical property information shows considerable overlap in densities within the Lower Palaeozoic and Precambrian formations, with relatively few units of the exposed succession being strongly magnetic. While the geophysical anomalies cannot be interpreted unambiguously in terms of these sources, the data can still be used to test different geological models and to indicate the range of possible solutions. The major fault zones are seen to influence the anomaly patterns in a variety of ways, reflecting a combination of differing near-surface contrasts and effects within the underlying basement. The general increase in gravity values towards Cardigan Bay may originate from the lower crust, and the large amplitude aeromagnetic low seen over Cardigan Bay indicates that a distinctive change in the character of the crust occurs here. Two-dimensional modelling in central Wales shows that a westward thickening of the Welsh Basin, to a maximum of about 10 km, may also be significant. It is necessary to postulate a separation of the base of denser, Lower Palaeozoic rocks from the underlying, more magnetic basement in order to account for offsets in anomaly source locations. This implies the presence of less dense Cambrian sediments and/or non-magnetic components of the Precambrian basement.

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“…Other aspects of data presentation and interpretation are discussed in McDonald et al (1992). Other aspects of data presentation and interpretation are discussed in McDonald et al (1992).…”

Section: Introductionmentioning

confidence: 99%

Some constraints on the form of the Welsh Basin from regional gravity and aeromagnetic data, with particular reference to Central Wales

Carruthers

Fletcher²,

McDonald³

et al. 1992

Geol. Mag.

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“…The northern bounding fault of Pretannia (Cope 1987;Cope and Bassett 1987;see also Tunbridge 1986) is presumed to have been the southern margin of the graben. Whether this coincides with a WSW-ENE-trending, major basement fault, postulated on the basis of gravity and magnetic data, south of Pembrokeshire (McDonald et al 1992) is also uncertain.…”

Section: Provenance Synthesismentioning

confidence: 95%

Enigma variations: the stratigraphy, provenance, palaeoseismicity and depositional history of the Lower Old Red Sandstone Cosheston Group, south Pembrokeshire, Wales

Thomas¹,

Williams

Morrissey

et al. 2006

Geol. J.

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“…Gravity and magnetic maps (scale of 1 : 50 000 and 1 : 200 000) were accordingly used to identify tectonic elements of the crystalline basement that occurs at a depth of 800-900 m. Automated interpretation techniques are preferred. The shadow image is a powerful tool for detection of linear tectonic zones (Arvidson et al, 1982;McDonald et al, 1992). Short-wavelength local anomaly transformations were computed to map density distributions at shallow levels in the earth's crust.…”

Section: Methods and Datamentioning

confidence: 99%

Origin of the Great Nemunas Loops, South Lithuania

Baltrūnas¹,

Šliaupa²,

Karmaza³

2006

gpq

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The Nemunas River, one of the largest rivers of the Baltic region, is characterised by a generally straight valley. In the middle part of its course the Great Nemunas Loops are distinct features that occupy an area of 320 km2 near the Birštonas Resort. The Nemunas valley here is 1.5‑5 km wide and 45‑80 m deep. The loops are cut into a glaciolacustrine plain confined between glacial and deltaic relief complexes and formed during the two last phases of glaciation. The origin of the entrenched loops, as large as 6‑10 km, can not be explained in conventional terms of river meandering. The activity of underlying tectonic structures is the major factor, the Great Nemunas Loops being confined to the Birštonas tectonic depression. Despite their small magnitudes the neotectonic structures within the depression significantly influenced the glacial and meltwater sedimentation (hence, the topography) that controlled the geometry of the Nemunas valley. The initial sinuosity of the valley was only a little enhanced by later lateral erosion. Fault activity is indicated by numerous mineral water springs and straight channel segments. Only a few sites of similar mineral water discharge are documented in Lithuania, suggesting the specific structural setting of the Great Nemunas Loops. Inspection of drill cores revealed the inheritance of the Nemunas valley from underlying paleovalleys of Eemian and Holsteinian Interglacials, implying persistence of the controlling factors.Le fleuve Nemunas, un des plus grands fleuves de la région baltique, est caractérisé par une vallée généralement rectiligne. À la mi-course du Nemunas, les Grandes Boucles occupent un territoire de 320 km2 dans la zone de villégiature de Birštonas. Ces méandres, d’une largeur de 6 à 10 km, entaillent une plaine glaciolacustre confinée entre des complexes glaciaires et deltaïques formés au cours des deux dernières phases de déglaciation. À cet endroit, la vallée du Nemunas a une largeur de 1,5 à 5,0 km et une profondeur de 45 à 80 m. L’origine de ces boucles profondes ne peut être imputée aux processus habituels de formation de méandres. L’activité des structures tectoniques sous-jacentes est le principal facteur à l’origine de leur formation. Les Grandes Boucles du Nemunas sont confinées à la dépression tectonique de Birštonas, sur laquelle se sont formées des structures néotectoniques de moindre ampleur. Ces dernières ont néanmoins eu une influence significative sur la sédimentation glaciaire et celle associée aux eaux de fonte (et sur la topographie) qui a influencé la géométrie de la vallée du Nemunas. La sinuosité initiale de la vallée n’a été que peu accentuée par l’érosion latérale ultérieure. L’activité des zones de faille est décelée par la présence de nombreuses sources d’eau minérale et le redressement de certains segments du fleuve. Seuls quelques sites ayant des sources minérales similaires sont connus en Lituanie, ce qui met en relief la singularité structurale des Grandes Boucles du Nemunas. L’examen des carottes de forage révèle la filiation entre ...

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Interpretation of the regional gravity and magnetic surveys of Wales, using shaded relief and Euler deconvolution techniques

Cited by 12 publications

References 18 publications

Some constraints on the form of the Welsh Basin from regional gravity and aeromagnetic data, with particular reference to Central Wales

Some constraints on the form of the Welsh Basin from regional gravity and aeromagnetic data, with particular reference to Central Wales

Enigma variations: the stratigraphy, provenance, palaeoseismicity and depositional history of the Lower Old Red Sandstone Cosheston Group, south Pembrokeshire, Wales

Origin of the Great Nemunas Loops, South Lithuania

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