A correlation of Lewisian structures and their displacement across the lower thrusts of the Moine thrust zone, NW Scotland

Coward, M. P.; Kim, J.H.; Parke, J. R.

doi:10.1016/s0016-7878(80)80027-7

Cited by 31 publications

(14 citation statements)

References 24 publications

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“…Because of the NW to SE transport direction of these structures and the accompanying NW-plunging lineations all the thrust tectonics of the southern margin of the Damaran belt are correlated with the F~ structures elsewhere. The localised development of polyphase deformation within the thrust sheets is consistent with recent models of strain development during differential movement of the thrusts (QuINQUIS et al 1978, COWARD & KIM 1980. Thus the five deformation phases reported by HA~TNADY (1978 C) for the Naukluft nappes and the numerous phases of folding and thrusting SE of the Hakos Mountains (Fig.…”

supporting

confidence: 87%

The Okahandja Lineament and its significance for Damaran tectonics in Namibia

Downing

Coward

1981

Geol Rundsch

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The Okahandja Lineament is considered to represent the southern margin of a magmatie arc produced by the northerly subduction of the Damran Ocean between 750 and 520 Ma ago. Sediments of the Orogen and granitoid intrusives produced by subduetion and crustal melting, underwent shear deformation between 675 and 575 Ma in a low angle zone of sinistral sense shear.The Okahandja Lineament represents a zone of differential movement between the Central and Southern Zones of the Orogen during this simple shear deformation. Both overriding and overriden plates were deformed at about 550 and 520 Ma. Production of open S.E. verging structures on the northern plate was accompanied by more intense thrust and fold nappe production on the southern margin of the Damaran Orogen. During this last deformation event, the Central magmatic Zone was downfolded under the southern zone. This fold is the present expression of the Okahandja Lineament. Two tectonic models are proposed for the structures identified within the Central and Southern Zones of the Orogen, combined with evidence from the northern coastal arm of the Orogen. R~sum6Le lin6ament de Okahandja est consider6 comme la marge bordant au sud un << arc magmatique >> r~sultant de la subduction vers le nord de l'Oc6an damaranique durant l'intervalle 750--520 M.a. Le lineament de Okahandja repr~sente, pour tes .d6formations cisaillantes simples une zone de d~placements partiels entre la zone centrale et la zone m~ridionale de l'orog~ne. Les deux plaques, celle du toit et celle du tour, de ce chevauchement furent d~fonn~es entre approximativement 550 et 520 M. a. Ces structures ouvertes, d6vers6es vers le nord, se forrn~rent dans la plaque septentrionale, pendant que des nappes en plis naissaient simultan6ment, sous l'influence d'une forte so sollicitation, dans la marge m~ridionale de l'orog~ne damaranique, ce qui entratna Ie ploiement de la zone magmatique centrale sous la zone m6ridionale, Ce pli est la forme seus laquelle appara~t aujourd'hui le lin6arnent de Okahandja. --Deux mod~les tectoniques sent propos6s pour expliqeur les structures ainsi reconnues dans les zones centrale et m6ridionale de l'orog~ne, sur la base du fair d'un bras le long de la cbte septentrionale de l'orog6ne. JI~nea~eaT Okahandja npeigcwaBxaeT co6ofi son~i y~epeHHoro Z~Bm~eu~, np~-ae~ ~e>~y ~eHTpaJn, nof~ H tOJts 3ona/dH oporeHa ameba MeCTO ~edpopraanina c~o~>~e~aa, l'~m5a ~pos~a, ~a~ r~Sa no~ozaBSX ~peTepnezn neqbop~a~ro r~eac~y 550 r~ 520 r~OHO~ ne~ ~orey ~aza~. Ha ce~eprro_~ r~:6e o6pasosa~ac~ oTKpl~ITaa cTpy~ypa onpo~rmyraa Ha ~0POBOCTOK, B TO spe~a, rca~ n pesyJmTaTe ~anpa~eana BOOnIZ~a cI~Jm/]i~I~ noKpoBa. IIpH 3T0~ ~4eHTpa~bHa~ MaI'MaTH-9 ~eei~a~ 3oHa no~ to.Holt aacTr~m or:asaJ~ac~ CMaTO~. PacnoJIo~eHr~e OTI~X cI~a~oI~ oTpa~aeT cero~H~mr~ee pacno~o~eHHe ~Hr~eaMeHTa.~IH 05%~CHeHH~I BO3HHHHOBeHHH DTHX eTpyETypH~X 3J~e~IeHTOB B ~eHTpa~-no~ H ro~Ho~ s0Hax oporeHa npe~aramw j~Be TaKTOHHqecKHe Mo~eJIH. B KOT0p~x ygTeH~ H Crpy~Typn~e 3JIeMeHT~I ceBepHoro 5eperosoro ~pa~ oporeHa.

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supporting

confidence: 87%

The Okahandja Lineament and its significance for Damaran tectonics in Namibia

Downing

Coward

1981

Geol Rundsch

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“…The offset of Lewisian structures between this sheet and the foreland enabled Coward et al (1980) to estimate a total displacement of 25-33 km on the Glencoul and lower thrusts, values which are broadly substantiated by the independent constructions of Elliott and Johnson (1980). At Glendhu the Lewisian within the Glencoul sheet attains its maximum thickness of 600 m but just 3 km along strike, immediately south of Loch na Creige Duibhe (Fig.…”

mentioning

confidence: 74%

“…The restored length is 15-8 km (see Fig. 11) which can be added to the displacement of the Glencoul and lower thrusts (25-33 km, Coward et al 1980) to give a total restoration of 41-49 km. Note that this restoration is compatible with Elliott and Johnson's (1980) estimation of c. 44 km on the adjacent Loch More sheet.…”

Section: Discussionmentioning

confidence: 99%

Structural evolution of the Moine thrust belt between Loch More and Glendhu, Sutherland

Butler

1984

SJG

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SYNOPSISReinvestigation and new mapping confirm that the area contains a number of large thrust sheets and imbricate slices of Cambrian cover and Lewisian basement but emphasise that they are bounded by an interconnecting network of WNW-directed faults. The network demonstrably propagated, piggy-back fashion, into the foreland since higher structures are cut or bulged up by lower imbricates. These new interpretations require a revision of structural units in the Glendhu area.The margins of culminations, which resulted from the continual stacking of imbricate slices, are the sites of extensional faulting which locally post-date thrust structures. However, some of the major thrusts in the area have primary extensional geometries in their footwalls and hanging walls since they cut down stratigraphic section towards the foreland. The proposed explanation is that bedding in the foreland Cambrian shelf was dipping gently to the SE, possibly in response to isostatic loading by the emplacement of the c. 10 km thick Moine thrust sheet. Datum-parallel thrust flats would then cut down stratigraphic section with an extensional sense. Early extensional strains which locally predate imbricate thrusts in those Cambrian quartzites in the immediate footwall to the Moine thrust may reflect a major gravity spreading component in the initial phases of the emplacement of the Moine sheet.The geometry of thrusts in the Glendhu culmination is illustrated on a balanced cross-section. The hanging wall of the Glencoul thrust, which includes a stack of interthrust Cambrian cover and Lewisian basement termed the Aisinnin imbricates, restores to a width of over 15 km. This can be added to the displacement on the Glencoul and lower thrusts as estimated from the offset of foreland structures, of 25-33 km, to give a total restoration for the footwall of the Moine thrust of at least 40 km.

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“…Several authors (Peach et al 1907;Elliott & Johnson 1980;Coward et al 1980) have estimated the displacement of different thrusts based upon the offset between correlated features in the Foreland and within the Assynt Culmination. For instance, Elliott & Johnson (1980) estimated a maximum thrust displacement of 25 km based upon the offset of the northern limit of undeformed Scourie Dykes, which occurs in the Foreland and north of Glencoul.…”

mentioning

confidence: 99%

“…This thrust displacement estimate is not affected by the reinterpretation, except that it now applies to the Ben More Thrust. More problematical are the estimates of similar magnitude based upon correlations made by Coward et al (1980) of Lewisian structures across the Glencoul Thrust. Coward et al (1980) correlated an 'F 4 Scourian' antiform near Ben Auskaird in the Foreland with an F 4 Scourian antiform in Lewisian Gneiss near Glen Beag.…”

mentioning

confidence: 99%

Lateral ramps and thrust terminations: an example from the Moine Thrust Zone, NW Scotland

Krabbendam

Leslie

2004

JGS

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Detailed remapping within the Assynt Culmination in NW Scotland shows that the Ben More Thrust joins the Glencoul Thrust along a lateral branch line positioned in Loch Glencoul. This branch line marks the northern lateral termination of the Glencoul Thrust. The thrust on the northern shore of Loch Glencoul (‘the famous view’) is thus the Ben More Thrust. The Ben More Thrust Sheet is therefore much larger than previously thought. The lateral terminations of the Ben More Thrust to the north and the south are of two distinct types. This reinterpretation negates the existence of ‘surge’ zones in Assynt.

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A correlation of Lewisian structures and their displacement across the lower thrusts of the Moine thrust zone, NW Scotland

Cited by 31 publications

References 24 publications

The Okahandja Lineament and its significance for Damaran tectonics in Namibia

The Okahandja Lineament and its significance for Damaran tectonics in Namibia

Structural evolution of the Moine thrust belt between Loch More and Glendhu, Sutherland

Lateral ramps and thrust terminations: an example from the Moine Thrust Zone, NW Scotland

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