scholarly journals The stratigraphy, correlation, provenance and palaeogeography of the Skiddaw Group (Ordovician) in the English Lake District

1995 ◽  
Vol 132 (2) ◽  
pp. 185-211 ◽  
Author(s):  
A. H. Cooper ◽  
A. W. A. Rushton ◽  
S. G. Molyneux ◽  
R. A. Hughes ◽  
R. M. Moore ◽  
...  
Keyword(s):  
Lake District ◽  
Volcanic Material ◽  
Early Ordovician ◽  
Isle Of Man ◽  
Lower Ordovician ◽  
Continental Arc ◽  
English Lake District

AbstractA new lithostratigraphy is presented for the Skiddaw Group (lower Ordovician) of the English Lake District. Two stratigraphical belts are described. Five formations are defined in the Northern Fells Belt, ranging in age from Tremadoc to early Llanvirn. They are all mudstone or sandstone dominated, of turbidite origin; in ascending order they are named the Bitter Beck, Watch Hill, Hope Beck, Loweswater and Kirk Stile formations. Two formations are defined in the Central Fells Belt, ranging in age from late Arenig to Llanvirn. These are the Buttermere Formation – a major olistostrome deposit – overlain by the Tarn Moor Formation, consisting of turbidite mudstones with volcaniclastic turbidite sandstone beds. A revised graptolite and new acritarch biostratigraphy for the Skiddaw Group is presented with eight graptolite biozones and thirteen acritarch assemblages and sub-assemblages. The provenance of the group is assessed from detailed petrographical and geochemical work. This suggests derivation, in the early Ordovician, largely from an old inactive continental arc terrane lying to the southeast, with the appearance of juvenile volcanic material in the Llanvirn. Comparisons and correlations of the Skiddaw Group are made with the Isle of Man and eastern Ireland.

A new early Ordovician Didymograptid, and its bearing on the correlation of the Skiddaw Group of England with the Tøyen Shale of Scandinavia

1991 ◽  
Vol 128 (4) ◽  
pp. 335-343 ◽  
Author(s):  
J. Maletz ◽  
A. W. A. Rushton ◽  
K. Lindholm
Keyword(s):  
Short Range ◽  
Lake District ◽  
Early Ordovician ◽  
Lower Ordovician ◽  
English Lake District

AbstractDidymograptus (s.l.) rigoletto sp.nov. is a distinctive species in the balticus group of didymograptids occurring in the Tøyen Shale (Lower Ordovician). In three localities in Sweden it has a short range near the top of the range of Tetragraptus phyllograptoides, and it occurs at about the same level at localities in the Oslo region, Norway; at most of these localities it occurs within the range of Tetragraptus of the approximatus group. Its presence in the Skiddaw Group of the English Lake District indicates the occurrence there of the basal Arenig (sensu lato), equivalent to the T. phyllograptoides Biozone of Scandinavia and the T. approximatus Biozone (= Lancefieldian 3) of the Australasian succession.

The age of the Watch Hill Grits (Ordovician), English Lake District: structural and palaeogeographical implications

1988 ◽  
Vol 79 (1) ◽  
pp. 43-69 ◽  
Author(s):  
S. G. Molyneux ◽  
A. W. A. Rushton
Keyword(s):  
New Combination ◽  
Lake District ◽  
Isle Of Man ◽  
Lower Ordovician ◽  
English Lake District

ABSTRACTThe Watch Hill Grits, in the lower Ordovician Skiddaw Group of the Lake District, are dated as latest Tremadoc or earliest Arenig (older than the Didymograptus deflexus Biozone) by means of acritarchs and graptolites. This places them lower in the Skiddaw sequence than previous authors supposed, and they are thought to have been thrust southwards over younger Arenig rocks. The interval inferred for the Watch Hill Grits brackets the Tetragraptus approximatus Biozone and its equivalents in Australasia, S China, N America and Scandinavia. The dating of the Watch Hill Grits suggests that equivalents of the Tetragraptus approximatus Biozone are present in N England and that sedimentation continued in the Lake District during a period of global eustatic regression. Other beds in the Lake District and on the Isle of Man have yielded similar acritarch assemblages and are probably correlatives. Five new acritarch taxa are described: Caldariola gen. nov., Acanthodiacrodium? dilatum, Stellechinatum sicaforme and Striatotheca prolixa spp. nov., and Tetraniveum arenigum cumbriense subsp. nov.; one new combination, Caldariola glabra (Martin) comb, nov., is proposed.

scholarly journals On Manganese in Sea and Fresh Waters

1949 ◽  
Vol 28 (1) ◽  
pp. 155-164 ◽  
Author(s):  
H. W. Harvey
Keyword(s):  
Particulate Matter ◽  
Agricultural Land ◽  
Sea Water ◽  
Lake District ◽  
Fresh Waters ◽  
Isle Of Man ◽  
English Lake District ◽  
Maximum Quantity

A method of estimating the maximum quantity of manganese available to plants in sea and fresh waters is described.Samples of sea water collected off Plymouth in 1948 contained 0·7–1·0 mg. Mn/m.3 in solution plus any particles soluble at pH 4·6. After storage and sedimentation of particulate matter, the quantity decreased to 0·0–0·25 mg./m.3Samples collected off the Isle of Man, an area with a rich summer population of flagellates, contained 2·0–2·6 mg./m.3The river Yealm, south Devon, on leaving Dartmoor contained 1 mg., and after passing through agricultural land 10 mg.\m.3Lakes and streams in the English Lake District contained 6–40 mg.\m.3 The least fertile waters contained the least soluble manganese.

Acritarch dating of latest Tremadoc – earliest Arenig (early Ordovician) sediments in the Carmarthen district, south Wales

1989 ◽  
Vol 126 (6) ◽  
pp. 707-714 ◽  
Author(s):  
S. G. Molyneux ◽  
K. J. Dorning
Keyword(s):  
Lake District ◽  
Early Ordovician ◽  
South Wales ◽  
English Lake District

AbstractAn acritarch assemblage from beds beneath the Ogof Hên Formation near Carmarthen (the ‘Login beds’) resembles assemblages from the Watch Hill Grits and underlying sediments of latest Tremadoc or earliest Arenig age in the Skiddaw Group of the English Lake District. We conclude that the Login acritarch assemblage is younger than at least some part of the late Tremadoc Angelina sedgwickii Biozone, but older than the early Arenig Didymograptus deflexus Biozone. Its occurrence may therefore coincide with that of the graptolite Tetragraptus approximatus. This is of particular significance in any attempt to define an internationally correlatable base for the Arenig Series in Britain.

New palynological data from the Leinster Lower Palaeozoic massif, southeastern Ireland

2000 ◽  
Vol 91 (3-4) ◽  
pp. 509-514 ◽  
Author(s):  
Peter M. Brück ◽  
Kenneth T. Higgs ◽  
Nadia Maziane-Serraj ◽  
Michel Vanguestaine
Keyword(s):  
Tectonic Evolution ◽  
Structural Breaks ◽  
Early Ordovician ◽  
Palynological Data ◽  
Isle Of Man ◽  
Lower Ordovician ◽  
Major Break ◽  
Lower Palaeozoic ◽  
Upper Silurian

ABSTRACTIn southeastern Ireland, the tectonic evolution of the northwestern Avalonian margin is rather poorly understood and only partially constrained. This is because the stratigraphy comprises in the main unfossiliferous turbidites. Nevertheless, some authors have attempted to define ‘terranes’ and ‘tracts’ in the region, aided by several significant Caledonoid-trending structural breaks that can be determined in the field. Palynological work was carried out in the early 1970s and established a range of ages from approximately mid Cambrian to late Silurian, although much of the succession proved barren. In the current study, the Lower Palaeozoic sequences W of the Leinster Granite and in the Slievenamon Inlier to the S have been palynologically re-investigated. Previous work proposed an unbroken succession from lower Ordovician Ribband Group turbidites and volcanics younging westwards conformably into upper Silurian Kilcullen Group sediments. The new study clearly shows that the Ordovician palynomorphs in the older part of the Kilcullen Group are reworked. In fact, there exists a major stratigraphical break between the Ribband Group dated as early Ordovician, Arenig, and the Kilcullen Group which is entirely Silurian, late Llandovery to early Wenlock in age. This major break has a minimum strike length of 150 km and is most likely much longer, extending some hundreds of kilometres SW to Dingle and possibly equating with a similar discontinuity in the Isle of Man to the NE. This break would thus appear to be a major feature within the succession of the northwestern Avalonian margin.

Strike-slip terranes and a model for the evolution of the British and Irish Caledonides

1987 ◽  
Vol 124 (5) ◽  
pp. 405-425 ◽  
Author(s):  
Donald H. W. Hutton
Keyword(s):  
North America ◽  
Continental Margin ◽  
Strike Slip ◽  
Slip Zone ◽  
Lake District ◽  
Early Ordovician ◽  
Boundary Fault ◽  
Lower Ordovician ◽  
Major Strike ◽  
Back Arc

AbstractEvidence is presented that many of the major strike faults in the British and Irish Caledonides were active as sinistral strike-slip zones in the end-Silurian to pre-mid-Devonian period. Some, such as the Highland Boundary Fault, moved in this way at an earlier stage in the Ordovician. These data allow the Caledonian rocks lying between the Laurentian miogeocline (whose basement is represented by the Lewisian, Moine and possibly the Dalradian) and the Gondwanaland miogeocline (Midland Platform and Welsh Basin) to be re-analysed as a group of disorganized terranes which originated to the southwest in North America and southwest Europe/Africa prior to the Silurian. The Highland Border Terrane and Northern Belt Terrane are interpreted as duplicated pieces of a mid-Ordovician sequence which was a back are to northwest subduction. The Midland Valley Terrane is interpreted as a slice of Laurentian foreland onto which ophiolites were obducted in the lower Ordovician but which became the basement of a continental margin arc to northwest subduction in the mid-Ordovician. The Cockburnland Terrane is inferred to be part of the same arc repeated and then broken up and dispersed by continuing strike slip. The Connemara Terrane is regarded as an allochthonous piece of the Dalradian miogeocline and the South Mayo Terrane as a remnant of an early Ordovician arc and fore arc which in mid-Ordovician times became a back arc/marginal basin to northwest subduction. The Lake District-Wexford Terrane is part of an arc to southeast subduction under Gondwanaland whose activity climaxed in the mid-Ordovician. The Central Terrane is interpreted as a Silurian overstep assemblage which blankets the junction between Laurentian- and Gondwanaland-derived oceanic terranes, and therefore Iapetus is regarded as an Ordovician ocean which closed prior to the Silurian. The model suggests that at the end of the Silurian, a clockwise-rotating Gondwanaland, having carried Laurentia into collision with Baltica, broke free and created a major sinistral strike-slip zone which disrupted the Ordovician palaeogeography in the British Isles/North American sector of Iapetus.

Microscopic and megascopic fabrics in the Skiddaw Group, Black Combe inlier, English Lake District

1969 ◽  
Vol 106 (6) ◽  
pp. 587-594 ◽  
Author(s):  
Douglas G. Helm
Keyword(s):  
Clay Minerals ◽  
Regional Metamorphism ◽  
Axial Plane ◽  
Low Grade ◽  
Lake District ◽  
Tectonic History ◽  
Lower Ordovician ◽  
English Lake District ◽  
History Of

SUMMARYThe rocks of the Skiddaw Group of the Black Combe inlier were subjected to low grade regional metamorphism during the D1 movementphase of an intra-Lower Ordovician orogenic episode. Mimetic recrystallisation of clay minerals parallel to the bedding was ubiquitous. Later, axial-plane cleavages were superimposed on this fabric. The nature of the cleavages and possible mechanism of their formation is discussed.Silica has been mobilised on at least three occasions during the tectonic history of the inlier. In no case was this due to metasomatism but simply to metamorphic differentiation. The D1 veins are of either quartz, or quartz and chlorite whereas veins of later generations are of quartz alone.

The timing of Ordovician magmatism in the English Lake District and Cross Fell inliers

1993 ◽  
Vol 130 (3) ◽  
pp. 369-377 ◽  
Author(s):  
Richard A. Hughes ◽  
Peter Kokelaar
Keyword(s):  
Volcanic Rocks ◽  
Arc Magmatism ◽  
Lake District ◽  
Early Ordovician ◽  
Extensional Tectonic ◽  
English Lake District ◽  
Lower Palaeozoic ◽  
Ordovician Magmatism ◽  
Tectonic Style ◽  
Subduction System

AbstractVolcanic and hypabyssal intrusive rocks of the Lower Palaeozoic English Lake District and Cross Fell inliers are elements of the Ordovician destructive plate margin system of microcontinental Avalonia. Two igneous sheets within the marine sedimentary Skiddaw Group of these inliers, previously described as lavas, are reinterpreted as sills. Sedimentary rocks enclosing these sills are of late Tremadoc-early Arenig (c. 493 Ma) and early Llanvirn (> 476 Ma) age, and breccias along the upper contacts of both were produced by steam explosivity and fluidization ahead of theadvancing tips of the intrusions. Previous interpretation of the breccias on the older sheet, as sediment deposited on the eroded top of a lava flow, implied an early Ordovician onset of arc magmatism. Such early magmatism would have been virtually coincident with the latest Tremadoc initiation of arc magmatism in Wales, but evidence for such a near synchronous response tothe putative onset of subduction is lacking. Respective onsets of magmatismwere probably separated by at least 17 m.y., and possibly by as much as 29 m.y. The apparent contemporaneity of mid and late Ordovician volcanic episodes in England and Wales, and similarities in extensional tectonic style, suggest that the two areas then were part of the same subduction system responding similarly to plate-scale magma-generating and tectonic processes. The early Ordovician situation is uncertain, but the absence of arc volcanic rocks of this age in the English Lake District suggests that this area and Wales are not tectonically juxtaposed elements of a former simple linear arc.

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