Extensional geometries as a result of regional scale thrusting: tectonic slides of the Dunlewy-NW Donegal area, Ireland

Hutton, D.M.; Alsop, G. Ian

doi:10.1016/0191-8141(95)00031-8

Cited by 18 publications

(10 citation statements)

References 19 publications

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“…No major F 1 folds or D 1 structures analogous to those described from central Donegal are identified (see Alsop, 1992;Hutton & Alsop, 1995. Minor F 1 folds noted by Howarth, Kilburn & Leake (1966) to the south of Skelpoonagh Bay are now considered to be F 2 in age.…”

Section: A Early D 1 Structuresmentioning

confidence: 93%

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Ductile transpression and localization of deformation along tectonic boundaries in the Caledonides of northwestern Ireland

1998

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Orogenesis is increasingly interpreted in terms of strain focusing, localization and partitioning processes. Such heterogeneous deformation is considered a consequence of the tectonic framework, with pre-existing structural and stratigraphic variability providing inherent zones of crustal weakness. Detailed structural investigation of Neoproterozoic Dalradian metasediments in the Glencolumbkille region, northwest Ireland, enables patterns of reworking and strain localization to be assessed in terms of four overprinting ductile deformation episodes. A well-defined and intricate Dalradian stratigraphy provides readily distinguishable markers which not only focus deformation along marked rheological boundaries, but also aid in the definition and identification of resultant geometries. Overall structural and stratigraphic relationships show that whilst D1 was not associated with major structures, D2 is related to north–northeast directed folding and ductile thrusting resulting in a major phase of crustal thickening and almandine-amphibolite facies metamorphism. Structures generated during D2 deformation subsequently became the locus of intense D3 strain and were reactivated in an oblique sense associated with south or southwest directed translations. Local overprinting relationships clearly demonstrate S2 fabrics being transposed by S3 resulting in a composite foliation over large areas. Similarly, the L2 mineral lineation is abruptly transposed by L3 over relatively small distances indicating high D3 strain gradients and the susceptibility of lineations to reworking. The final stage of ductile deformation (D4) which was increasingly localized and focused into earlier (D2−D3) high strain zones, is marked by a pronounced phase of sinistral transpression associated with clockwise cleavage and minor fold transection of northwest verging upright folds. Sinistral shear is strongly partitioned in to the steep limbs of mesoscopic F4 folds. The detailed investigation of structures generated within such multiply deformed and reworked zones provides evidence of both the kinematic and tectonic evolution of regional deformation systems.

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Section: A Early D 1 Structuresmentioning

confidence: 93%

“…1), D 2 is associated with top-to-thenorthwest ductile thrusting (Hutton & Alsop, 1995Jolley, 1996) whilst in the Gweebarra Bay area of west Donegal (Fig. 1) D 2 vergence and facing is upwards to the north or northeast (Meneilly, 1982).…”

Section: Regional Tectonics and Implicationsmentioning

confidence: 97%

Ductile transpression and localization of deformation along tectonic boundaries in the Caledonides of northwestern Ireland

1998

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“…The mineralogy of the Ards and Falcarragh pelites throughout the Horn Head/Creeslough area has been determined by workers such as Hutton (1977), Hutton & Alsop (1995), Long & McConnell (1997), McCall (1954, Pitcher & Berger (1972) and Rickard (1962), who suggest that the lithologies are very similar. XRD and XRF techniques were applied to a small number of representative samples for quantitative mineralogical determination and comparison to gamma-ray data.…”

Section: Laboratory Mineralogy and Geochemistrymentioning

confidence: 99%

“…Differentiating the two possible, yet similar, supra-slide pelite units would provide an invaluable test of each reconstruction as well as a possibly useful method in similar terranes. Recently Long & McConnell (1997) used the evidence of Hutton (1977) and Hutton & Alsop (1995) to refine the identification of the supra-slide unit as the Transition Member of the Ards Pelite Formation. Long & McConnell (1997, p. 28) concede (for Horn Head) that "difficulty remains in correlating slides along strike where they pass into the sea or were engulfed by later granites".…”

Section: Introduction and Issues To Be Examinedmentioning

confidence: 98%

Gamma-ray spectroscopy in structural correlations: an example from the Neoproterozoic Dalradian succession of Donegal (NW Ireland)

2000

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The Caledonian Horn Head Slide is a spectacular ductile shear zone transecting Neoproterozoic Appin Group Dalradian metasediments in Donegal (NW Ireland). Two conflicting stratigraphic interpretations exist for the inverted succession exposed in the hanging wall of the structure. These are based on correlation with two quite separate exposed pelite formations elsewhere. The two formations are lithologically indistinct and unfossiliferous. Here we document the novel use of assayed and logged spectral gamma-ray measurements in comparing the contentious pelite in the hanging wall of the Horn Head Slide to the two possible correlative pelite formations from a wide area of their unequivocal outcrop. The data from the contentious pelite show a clear statistical and stratigraphical affinity with one candidate unit only, thus providing the stratigraphical definition necessary for refining previous cross-sections. A new model, based on our spectral gamma-ray correlation, is proposed to account for the northwestwards directed emplacement of the Lower Falcarragh Pelite Formation along the slide. This model requires pre-Caledonian normal faulting as a precursor to the ensuing compressional event in which stratigraphically younger rocks were thrust over older, a common instance in fold and thrust belt geometry. Our work suggests that spectral gamma-ray measurements may provide a rapid, field-based method for differentiating unfossiliferous pelite or mudstone units at outcrop and in geophysical well-logs, even in structurally complex areas.

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“…7B). Within each nappe, recumbent F2 folds face northwest (Hutton and Alsop, 1995). Further south, to the southeast of the Leennan Fault, isoclinal, recumbent F2 folds, such as the Sperrin Nappe, were transported towards the southeast (Alsop, 1996).…”

Section: A Laurentian Cover Sequence In the Grampian Terrane -The Dalmentioning

confidence: 99%

The Laurentian Caledonides of Scotland and Ireland

Chew

Strachan

2013

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The Caledonides of Britain and Ireland are one of the most intensively studied orogenic belts in the world. This review considers all the tectonic events associated with the development and closure of the Iapetus Ocean. It first summarizes the tectonic evolution of each segment involved in the Scottish-Irish sector of the Caledonides and then reviews the temporal evolution of the Caledonian orogeny. Three main tectonic phases are recognized in the Scottish-Irish Caledonides: an Early to Middle Ordovician (475-465 Ma) phase termed the Grampian Orogeny, a phase of Silurian (435-425 Ma) tectonism restricted to the Northern Highland Terrane of Scotland termed the Scandian Orogeny, and an Early Devonian (395 Ma) phase, termed the Acadian Orogeny. The Grampian Orogeny was caused by the collision of the Laurentian continental margin with an oceanic arc terrane and associated supra-subduction zone ophiolites during the latest Cambrian to Early Ordovician. Following the Grampian arc-continent collision event there was a subduction polarity reversal. This facilitated continued subduction of Iapetan oceanic lithosphere and an Andean-type continental margin developed on and adjacent to the Laurentian margin in the Middle Ordovician along with a substantial thickness of accretionary prism sediments (the Southern Uplands-Longford-Down terrane). The Iapetus Ocean is believed to have disappeared by the Late Silurian based on the faunal record and a continent-continent collision ensued. The absence of significant regional deformation and metamorphism associated with the Late Silurian collision between Avalonia and the Scottish-Irish margin of Laurentia suggests that the continental collision in this sector of the Caledonian-Appalachian orogen was 'soft' or highly oblique. The exception is the Northern Highlands Terrane of Scotland that was believed to have been situated 500-700 km to the north along orogenic strike. This terrane records evidence for significant Silurian regional deformation and metamorphism attributed to the collision of the Laurentian margin of East Greenland with Baltica (the Scandian Orogeny). Current controversies in the Laurentian Caledonides of Scotland and Ireland are discussed at the end of this review.

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Extensional geometries as a result of regional scale thrusting: tectonic slides of the Dunlewy-NW Donegal area, Ireland

Cited by 18 publications

References 19 publications

Ductile transpression and localization of deformation along tectonic boundaries in the Caledonides of northwestern Ireland

Ductile transpression and localization of deformation along tectonic boundaries in the Caledonides of northwestern Ireland

Gamma-ray spectroscopy in structural correlations: an example from the Neoproterozoic Dalradian succession of Donegal (NW Ireland)

The Laurentian Caledonides of Scotland and Ireland

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