The early Palaeozoic evolution of northwest England

1993 ◽  
Vol 130 (5) ◽  
pp. 711-724 ◽  
Author(s):  
A. H. Cooper ◽  
D. Millward ◽  
E. W. Johnson ◽  
N. J. Soper
Keyword(s):  
Foreland Basin ◽  
Lake District ◽  
Volcanic Group ◽  
The North ◽  
Iapetus Ocean ◽  
Granitic Intrusions ◽  
Deformation Event ◽  
Lower Palaeozoic ◽  
Early Palaeozoic ◽  
Uplift And Erosion

AbstractThe Lake District and smaller Craven inliers of northwest England contain a Lower Palaeozoic sequence deposited on the Gondwanan side of the Iapetus Ocean, close to the junction with the Tornquist Sea. The Tremadoc to Llanvirn Skiddaw and Ingleton groups are deep water assemblages of turbidite, olistostrome and slump deposits, formed at a continental margin. They experienced uplift and erosion as a precursor to the eruption of two largely subaerial Llandeilo-Caradoc volcanic sequences: the tholeiitic Eycott Volcanic Group in the north and the calc–alkaline Borrowdale Volcanic Group in the central Lake District. The volcanic episodes are the earliest part of a major episode of magmatism, extending through to the early Devonian and responsible for a major batholith underpinning the Lake District. Subsidence in an intra-arc rift zone preserved the subaerial volcanic sequences. A marine transgression marks the base of the Windermere Group, which comprises a mixed carbonate–clastic shelf sequence of Ashgill age, passing upwards through the Silurian into a thick, prograding foreland basin sequence of Ludlow turbidites. Deformation of the Lower Palaeozoic sequences was possibly diachronous from north to south. It is attributed to the late Caledonian (Acadian) Orogeny and resulted in folding, cleavage and thrust development. Granitic intrusions, including those at Shap, Skiddaw and beneath the hydrothermal Crummock Water Aureole, are partly syntectonic and were therefore penecontemporaneous with this deformation event. Some thrust faulting post-dates the intrusive phase. Post-deformation Devonian conglomerates are also present locally.

An Acadian mountain front in the English Lake District: the Westmorland Monocline

1993 ◽  
Vol 130 (2) ◽  
pp. 203-213 ◽  
Author(s):  
B. C. Kneller ◽  
A. M. Bell
Keyword(s):  
Shear Zone ◽  
Foreland Basin ◽  
Lake District ◽  
Volcanic Group ◽  
The North ◽  
English Lake District ◽  
Mountain Front ◽  
Group A ◽  
Lower Palaeozoic ◽  
Wide Zone

AbstractThe structure of the southern and central English Lake District is that of a southeast-facing monocline, named here the Westmorland Monocline. This 10 km wide zone of highly cleaved, southeast-dipping rocks separates gently dipping, poorly cleaved Borrowdale Volcanic Group to the north from extensively folded but regionally subhorizontal Windermere Group (foreland basin) rocks to the south. The monocline formed early in the local Acadian deformation sequence, and accommodates at least 8 km of uplift. It coincides with the steep concealed margin of the Lake District batholith. A major northwest-dipping shear zone is revealed in the deepest levels now exposed within the monocline, in the Skiddaw Group rocks of the Black Combe inlier.The monocline has the characteristics of a mountain front, providing significant tectonic elevation across a foreland-dipping panel of rocks, with no hinterland-dipping thrust visible at the surface. We interpret the uplift as the consequence of a southeast-vergent thrust with a gently northwest-dipping ramp beneath the central Lake District, continuing southeastwards as a flat detachment beneath the Windermere Group. A displacement up the ramp of about 20 km is accommodated by backthrusting within the monocline and by shortening within the Windermere Group of the hangingwall southeast of the monocline. The tip lies beyond the limit of the Lower Palaeozoic inlier, beneath Carboniferous cover.

Foreland basin development and tectonics on the northwest margin of eastern Avalonia

1993 ◽  
Vol 130 (5) ◽  
pp. 691-697 ◽  
Author(s):  
B. C. Kneller ◽  
L. M. King ◽  
A. M. Bell
Keyword(s):  
Foreland Basin ◽  
Suture Zone ◽  
Lake District ◽  
Early Devonian ◽  
Basin Inversion ◽  
The North ◽  
Orogenic Wedge ◽  
Mountain Front ◽  
Thrust System ◽  
Early Palaeozoic

AbstractThe early Palaeozoic convergence of Avalonia and Laurentia created a foreland basin at the suture zone of the former lapetus Ocean. Sedimentological and stratigraphic evidence of shallowing and contemporaneous shortening suggests that the southern part of the basin (the Windermere Group) became detached from its basement in the late Ludlow, and began to invert. The detachment beneath the basin rooted into a northwest-dipping mid-crustal thrust system. Contemporaneous uplift to the north of the late Silurian basin involved shortening of the Avalonian foreland basement by thrusting. Basin inversion occurred ahead of a southeastward-advancing mountain front. We postulate a foreland (southeast) prograding sequence of thrusting through the Ludlow in the Lake District. The basin continued to migrate onto the Avalonian foreland through the early Devonian, ahead of an advancing orogenic wedge, finally coming to a stop in the Emsian.

scholarly journals Palaeozoic tectonic and sedimentary evolution and hyrdrocarbon prospectivity in the Bornholm area

1994 ◽  
Vol 34 ◽  
pp. 1-23
Author(s):  
Ole Valdemar Vejbæk ◽  
Svend Stouge ◽  
Kurt Damtoft Poulsen
Keyword(s):  
Late Cretaceous ◽  
Foreland Basin ◽  
Fault System ◽  
Structural Development ◽  
The South ◽  
Alum Shale ◽  
Present Distribution ◽  
Lower Palaeozoic ◽  
Wrench Fault ◽  
Uplift And Erosion

The present distribution of Palaeozoic sediments in the Bornholm area is a consequence of several different tectonic regimes during the Phanerozoic eon. This development may be divided into three main evolutionary phases: A Caledonian to Variscian phase encompassing the Lower Palaeozoic sediments. The sediments are assumed originally to have showed a gradual thickness increase towards the Caledonian Deformation Front located to the south. This pre-rift development may be further subdivided into three sub-phases: A period of slow sedimentation on a relatively stable platform as recorded by the uniformly low thicknesses of the Cambrian to Lower Silurian sediments. A period of foreland-type rapid sedimentation commencing in the Llandoverian to Wenlockian, continuing in the Ludlovian and possibly into the Devonian. The period is characterized by /olding and uplift of the Caledonides to the south causing tectonic loading of the foreland and resultant rapid sedimentation in the foreland basin. A period of gravitational collapse causing minor erosion during the Devonian. The transition to the second major phase in the Phanerozaic structural development, during which the Sorgenfrei-Tornquist zone came into existence, is recorded by regional deposition of Carboniferous sediments. These sediments are, however, mostly removed by tater erosion. A syn-rift phase characterized by sedimentation in graben areas and expanding basins commencing in the Rotliegendes and continuing through the Triassic, Jurassic and Lower Cretaceous. This phase was probably initiated by a Late Carboniferous- Early Permian tensional dominated right-lateral wrench fault system within the Sorgenfrei-Tornquist zone. A Post-rift development phase dominated by Late Cretaceous carbonate sedimentation. During Late Cretaceous and Early Tertiary times the Bornholm area was strongly affected by inversion tectonism caused by compressional strike-slip movements. This resulted in reverse faulting and uplift and erosion of former basinal areas. Understanding the two latter phases is important for understanding the present distribution of the Palaeozoic. A key to understanding the hydrocarbon potential of the area is the maturation of the organic matter in the main potential source, the Ordovician Upper Alum Shale. Maturity was mainly achieved during the Silurian to Late Palaeozoic time, and little further maturation took place later. The Upper Alum Shale is accordingly expected to be overmature in the main part of the study area and mature in the Hano Bay Basin. This reflects the assumed primary uniform thickness of the Lower Palaeozoic, with a general thinning towards the northeast. A Caledonian to Variscian phase encompassing the Lower Palaeozoic sediments. The sediments are assumed originally to have showed a gradual thickness increase towards the Caledonian Deformation Front located to the south. This pre-rift development may be further subdivided into three sub-phases: A period of slow sedimentation on a relatively stable platform as recorded by the uniformly low thicknesses of the Cambrian to Lower Silurian sediments. A period of foreland-type rapid sedimentation commencing in the Llandoverian to Wenlockian, continuing in the Ludlovian and possibly into the Devonian. The period is characterized by /olding and uplift of the Caledonides to the south causing tectonic loading of the foreland and resultant rapid sedimentation in the foreland basin. A period of gravitational collapse causing minor erosion during the Devonian. The transition to the second major phase in the Phanerozaic structural development, during which the Sorgenfrei - Tornquist zane came into existence, is recorded by regional deposition of Carboniferous sediments. These sediments are, however, mostly removed by tater erosion. A syn-rift phase characterized by sedimentation in graben areas and expanding basins commencing in the Rotliegendes and continuing through the Triassic, Jurassic and Lower Cretaceous. This phase was probably initiated by a Late Carboniferous- Early Permian tensional dominated right-lateral wrench fault system within the Sorgenfrei-Tornquist zone. A Post-rift development phase dominated by Late Cretaceous carbonate sedimentation. During Late Cretaceous and Early Tertiary times the Bornholm area was strongly affected by inversion tectonism caused by compressional strike-slip movements. This resulted in reverse faulting and uplift and erosion of former basinal areas. Understanding the two latter phases is important for understanding the present distribution of the Palaeozoic. A key to understanding the hydrocarbon potential of thearea is the maturation of the organic matter in the main potential source, the Ordovician Upper Alum Shale. Maturity was mainly achieved during the Silurian to Late Palaeozoic time, and little further maturation took place later. The Upper Alum Shale is accordingly expected to be overmature in the main part of the study area and mature in the Hano Bay Basin. This reflects the assumed primary uniform thickness of the Lower Palaeozoic, with a general thinning towards the northeast.

Lower–Middle Ordovician stratigraphy of North-East Greenland

2002 ◽  
pp. 117-125 ◽  
Author(s):  
Svend Stouge ◽  
W. Douglas Boyce ◽  
Jørgen L. Christiansen ◽  
David A.T. Harper ◽  
Ian Knight
Keyword(s):  
Passive Margin ◽  
East Greenland ◽  
Middle Ordovician ◽  
North East ◽  
Upper Proterozoic ◽  
Iapetus Ocean ◽  
Rodinia Supercontinent ◽  
Lower Palaeozoic ◽  
Early Palaeozoic ◽  
Laurentian Margin

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Stouge, S., Boyce, W. D., Christiansen, J. L., Harper, D. A., & Knight, I. (2002). Lower–Middle Ordovician stratigraphy of North-East Greenland. Geology of Greenland Survey Bulletin, 191, 117-125. https://doi.org/10.34194/ggub.v191.5138 _______________ The Upper Proterozoic (Riphean) to Lower Palaeozoic succession in North-East Greenland is exposed in a broad N–S-trending belt in the fjord region between 71°38´ and 74°25´N (Fig. 1). The succession comprises mainly marine sediments accumulated during the later stages of the break-up of the Rodinia supercontinent, the subsequent opening of the Iapetus Ocean and formation of the passive margin along the edge of the Laurentian palaeocontinent. Investigations of the sedimentary succession were initiated on Ella Ø in the summer of 2000 as part of a project to investigate the development of the Laurentian margin facing the Iapetus Ocean in the Early Palaeozoic, when studies of the uppermost formations of the Riphean Eleonore Bay Supergroup to the Lower Ordovician Antiklinalbugt Formation on Ella Ø were undertaken (Stouge et al. 2001). Ella Ø was revisited during the summer of 2001, with the focus on the Ordovician formations. In addition, investigations were undertaken in the Albert Heim Bjerge area where the uppermost part of the Ordovician succession is preserved (Fig. 1).

A revised correlation of Silurian rocks in the Girvan district, SW Scotland

2002 ◽  
Vol 93 (4) ◽  
pp. 383-392 ◽  
Author(s):  
James D. Floyd ◽  
Mark Williams
Keyword(s):  
Depositional Environment ◽  
Late Ordovician ◽  
Important Research ◽  
British Geological Survey ◽  
Marine Fauna ◽  
Comprehensive Review ◽  
Iapetus Ocean ◽  
Northern Side ◽  
Lower Palaeozoic ◽  
Early Palaeozoic

ABSTRACTIn late Ordovician and early Silurian times, the Girvan district lay in a shelf marinesetting on the margin of Laurentia, on the northern side of the Iapetus Ocean. The Lower Palaeozoic rocks of the Girvan district, and their shelly and graptolitic fossil fauna, were systematically described by Lapworth in 1882 and have formed an important research resource ever since. They provide valuable evidence for the depositional environment and geological setting of Girvan during the early Palaeozoic, in both regional and wider contexts, and demonstrate the long-recognised close affinity with contemporaneous Laurentian faunas. However, by late Ordovician and into Silurian times, the earlier Iapetus oceanic barrier to faunal migration had largely gone and there is good correlation between contemporaneous marine fauna throughout the British Isles and Scandinavia. Despite much recent research in the area, including resurvey work by the British Geological Survey, no comprehensive review of Silurian lithostratigraphy at Girvan has been published since the revision by Cocks and Toghill in 1973. The present review of the Silurian rocks addresses this need and complements the recently published (Fortey et al. 2000) revision of the underlying Ordovician rocks, thus bringing the entire Girvan Lower Palaeozoic succession up to modern standards of nomenclature.

scholarly journals Introduction

1992 ◽  
Vol 13 (1) ◽  
pp. xi-xii
Keyword(s):  
Plate Tectonics ◽  
Time Interval ◽  
British Isles ◽  
Late Precambrian ◽  
The Earth ◽  
Iapetus Ocean ◽  
Lower Palaeozoic ◽  
The Subject ◽  
Early Palaeozoic ◽  
Early Maps

AbstractAlmost forty years have elapsed since Leonard Wills published his 'Palaeogeographical Atlas of the British Isles'; those forty years have seen a revolution in the earth sciences which has overturned many earlier ideas in geology. Palaeogeography has been affected just as much as other parts of the subject by this change.The advent of the plate tectonic theory has transformed our ideas of the Lower Palaeozoic palaeogeographical evolution of the British area and has rendered totally obsolete many aspects of Wills' maps. The application of plate tectonics has caused us to produce totally new palaeogeographical models for the late Precambrian and early Palaeozoic, and has emphasised that definitive palaeogeographies for this time interval cannot yet be compiled. Wills was at pains to point out that his Atlas was an 'Aunt Sally' at which to 'hurl one's own and other field observations'-our atlas too must be viewed in that light.The Precambrian and Lower Palaeozoic maps are separated for the northern and southern British Isles areas, because for much of that time the two areas were separated by the Iapetus Ocean. The recognition of important terrane boundaries in Scotland and Ireland has led to our attempt to reconstruct a map from the collage of terranes now in juxtaposition. These early maps owe much to Keith Ingham's experience of the Lower Palaeozoic-Keith would insist here that the maps are very much in the 'Aunt Sally' mould, and that his interpretations may not be able to stand the test of time-but they represent

Structural evolution of the Skiddaw Group (English Lake District) on the northern margin of eastern Avalonia

1993 ◽  
Vol 130 (5) ◽  
pp. 621-629 ◽  
Author(s):  
R. A. Hughes ◽  
A. H. Cooper ◽  
P. Stone
Keyword(s):  
Large Scale ◽  
Volcanic Rocks ◽  
Structural Evolution ◽  
Foreland Basin ◽  
Lake District ◽  
Complex Deformation ◽  
Northern Margin ◽  
Marine Strata ◽  
Deformation Event ◽  
Group Structures

AbstractThe Skiddaw Group comprises a marine sedimentary sequence deposited on the northern margin of eastern Avalonia in Tremadoc to Llanvirn times. It is unconformably overlain by subduction-related volcanic rocks (the Eycott and Borrowdale Volcanic groups) of mid-Ordovician age, and foreland basin marine strata of late Ordovician and Silurian age. The Skiddaw Group has a complex deformation history. Syn-depositional deformation produced soft sediment folds and an olistostrome. Volcanism was preceded (in late Llanvirn to Llandeilo times) by regional uplift and tilting of the Skiddaw Group, probably caused by the generation of melts through subduction-related processes. The Acadian (late Caledonian) deformation event produced a northeast- to east-trending regional cleavage, axial planar to large scale folds, and a later set of southward-directed thrusts with associated minor folds and crenulation cleavages. This event affected the northern Lake District probably in the late Silurian and early Devonian. The Skiddaw Group structures contrast strongly with those formed during the same event in the younger rocks of the Lake District inlier. The contrasts are attributed to differing rheological responses to varying and possibly diachronous stresses, and to possible impedence of thrusting by the combined mass of the Borrowdale Volcanic Group and the Lake District batholith.

Neodymium isotopic composition of Cambrian–Ordovician biogenic apatite in the Baltoscandian Basin: implications for palaeogeographical evolution and patterns of biodiversity

2005 ◽  
Vol 142 (4) ◽  
pp. 419-439 ◽  
Author(s):  
ULF STURESSON ◽  
LEONID E. POPOV ◽  
LARS E. HOLMER ◽  
MICHAEL G. BASSETT ◽  
SERGEI FELITSYN ◽  
...  
Keyword(s):  
Sea Water ◽  
Constant Factor ◽  
Turnover Rates ◽  
Benthic Assemblages ◽  
The North ◽  
Tectonic History ◽  
Iapetus Ocean ◽  
History Of ◽  
Early Palaeozoic ◽  
T Values

Biogenic apatite preserved in 148 samples of conodonts and organophosphatic-shelled brachiopods from Cambrian through Ordovician successions of the Baltoscandian Basin (Baltica Plate) preserves a sensitive record of early Palaeozoic sea-water chemistry interpreted via neodymium isotope ratios. Consistent ${\uvarepsilon}$Nd(t) values of −9.6 to −8.3 for Lower to Middle Cambrian samples suggest no significant lateral or temporal variation across the region. Average Upper Cambrian values are −7.2 to −7.7. Sedimentary analysis suggests that the influence of continental weathering from Baltica as a major source of radiogenic Nd was negligible. Ordovician samples show a rise to −5 to −6 in the early Arenig, early–mid Llanvirn and late Caradoc. Sea-water mixing from the southeast Iapetus Ocean was a constant factor throughout Cambrian–Ordovician times. The rise reflects erosion of obducted volcanic arc complexes along the Caledonian margin, and probably also relates to pollution of the Baltica sector of Iapetus from the approaching Avalonia Plate. Patterns of evolutionary biodiversity and palaeobiogeographical linkages support the geochemical signatures in interpreting the tectonic history of the region. Extinction of lingulate brachiopod faunas in the Tremadoc, followed by subsequent recovery and emergence of benthic assemblages typical of the Ordovician Evolutionary Fauna in the Billingen–early Volkhov regional stages coincide with significant changes in geochemical characteristics of water masses across the Baltoscandian basin. The early and mid Ordovician (Arenig to Llandeilo) brachiopod faunas of the North Estonian Confacies Belt are characterized by high endemism and low turnover rates, whereas increased immigration resulted in the extinction of a number of local lineages in the late Llanvirn. From the mid Caradoc to mid Ashgill, when Baltica was drifting on a course to collide eventually with Avalonia and gradually approach Laurentia, brachiopod assemblages were characterized by higher turnover rates. At the same time they gradually became more cosmopolitan and less influenced by the invasion of new faunas.

The Iapetus suture in the British Isles

1989 ◽  
Vol 126 (1) ◽  
pp. 1-8 ◽  
Author(s):  
W. S. McKerrow ◽  
N. J. Soper
Keyword(s):  
Continental Crust ◽  
North American ◽  
Seismic Reflection ◽  
Plate Boundary ◽  
Surface Expression ◽  
Lake District ◽  
North West ◽  
The North ◽  
Iapetus Ocean ◽  
Seismic Reflection Profiling

AbstractThe position of the Iapetus Ocean suture can be traced between Ordovician fossil localities in the Southern Uplands and the Lake District which contain, respectively, distinct North American and European faunas. The Southern Uplands contains North American Caradoc faunas in the Northern Belt, and is considered to have been accreted onto the Laurentian (North American) margin between the Llandeilo and the end of the Wenlock. Deep seismic reflection profiling shows that a surface, probably parallel to the suture zone, dips down to the northwest from the Solway Line. In eastern Ireland, the surface trace of the suture coincides with the Navan Fault, which separates the Longford-Down massif from Ordovician sediments containing European faunas. The Navan–Silvermines Fault may represent the surface expression of the suture, but it is masked by Wenlock turbidites, which appear to have crossed over the plate boundary. Northward subduction of continental crust below the margin of Laurentia during the late Silurian may explain the influx of turbidite fans from the north or north west onto depressed crust to the south of the suture. Termination of subduction coincides with the widespread Acadian Orogeny in the Emsian (at 395±5 Ma).

scholarly journals Vendian stratigraphy and sedimentology of the East Greenland Caledonides

1985 ◽  
Vol 125 ◽  
pp. 88-94
Author(s):  
M.J Hambrey ◽  
A.C.M Moncrieff
Keyword(s):  
North Atlantic ◽  
Depositional Environment ◽  
Arctic Region ◽  
Harvard University ◽  
University Of Iowa ◽  
East Greenland ◽  
The North ◽  
Iapetus Ocean ◽  
Field Season ◽  
Early Palaeozoic

The present two-year programme 1984-1985 on the Vendian Tillite Group in central East Greenland follows comprehensive investigations on similar sequences in eastern Svalbard. The project aims to establish through Vendian time the disposition of land masses and oceans in relation to the East Greenland depositional environment, and to erect detailed stratigraphic correlations with other parts of the North Atlantic - Arctic region. This is important for understanding the tectonic evolution of the region prior to the opening of the Iapetus Ocean. The work is a collaborative venture involving N. Abrahamsen (University of Aarhus, palaeomagnetism), G. Bylund (University of Lund, palaeomagnetism), A. H. Knoll (Harvard University, biostratigraphy), A. M. Spencer (Statoil, sedimentology), K. Swett (University of Iowa, sedimentology of bounding rock units) and G. Vidal (University of Lund, biostratigraphy). The authors were accompanied in the 1984 field season by Bylund and Vidal who undertook extensive sampling of the Late Proterozoic to Early Palaeozoic sequence.

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