Precambrian and Palaeozoic rocks of the Inner Hebrides

1983 ◽  
Vol 83 ◽  
pp. 31-45
Author(s):  
R. Anderton ◽  
D. R. Bowes
Keyword(s):  
Small Area ◽  
Early Devonian ◽  
Red Sandstone ◽  
North West ◽  
Late Cambrian ◽  
Thrust Zone ◽  
Lower Palaeozoic ◽  
Caledonian Orogeny ◽  
Peripheral Areas ◽  
Mountain Chain

SynopsisThe Lewisian complex, which forms the continental basement to north-west Scotland, crops out on the Inner Hebridean islands of Rona, Raasay, Skye, Coll, Tiree, Iona and Islay. Upon this basement, four major rock successions were deposited before the Caledonian orogeny. The upper Precambrian Moine assemblage forms only a small area of metamorphosed rocks on Mull but the c. 790 m.y. (million year) old Torridonian sediments are found on Raasay, Scalpay. the Sleat of Skye, Soay and Rhum. The upper Precambrian to Cambrian Dal radian Supergroup dominates Islay, Jura, Gigha and the islands of the Firth of Lome whilst also forming a partial rim around the Tertiary Northern granite in Arran. Other Precambrian rocks of uncertain affinity are found on Islay, Oronsay, Colonsay and Iona. Cambro-Ordovician sediments are found on Skye where they have been partially metamorphosed by Tertiary intrusions.South-east of the Moine thrust zone, the Precambrian and lower Palaeozoic rocks were deformed and metamorphosed during the late Cambrian to early Devonian Caledonian orogeny which resulted in the development of the Caledonian mountain chain. Subsequently, Scotland north-west of the Highland Boundary fault has tended to persist as a land area undergoing erosion with sedimentation restricted to peripheral areas now preserved around the present coast. Upper Palaeozoic rocks are therefore only well represented on Arran although Old Red Sandstone (Devonian) sediments are found in the Firth of Lome and a very small area of possible Permian rocks occurs on Islay.

Role of the Midland Valley of Scotland in the Caledonian orogeny

1983 ◽  
Vol 74 (3) ◽  
pp. 119-136 ◽  
Author(s):  
B. J. Bluck
Keyword(s):  
Volcanic Rocks ◽  
Substantial Contribution ◽  
Volcanic Arc ◽  
Early Devonian ◽  
Red Sandstone ◽  
Metamorphic Basement ◽  
Caledonian Orogeny ◽  
Southward Extension ◽  
Trench Slope

ABSTRACTThe Midland Valley of Scotland was an arc–interarc region during most of Ordovician—Devonian time. This arc terrane extends beneath the allochthonous Southern Uplands and probably beneath the southern Highlands. Models of Caledonian plate tectonism which regard the Midland Valley as a fore-arc basin are rejected principally on the grounds that (i) the Ordovician sequence at Girvan, in the very SW of the Midland Valley, was generated in a proximal fore-arc basin to the immediate S of a contemporaneous plutonic–volcanic arc, and (ii) the source for Silurian sediments in the southern part of the Midland Valley could not have been a rising trench-slope-break, but igneous basement and conglomerates with clasts of metamorphic basement, i.e. the southward extension of the Midland Valley.The Midland Valley arc first comprised mainly plutonic rocks, some of which may have been basic but most of which were certainly granitic. Little is known of the ages of volcanic clasts in Silurian conglomerates (this time may have been a period of relative volcanic quiescence), but the Silurian–Devonian sequence is considered to have formed in an interarc basin which, like many other basins of this kind, began as marine (Early Silurian) and ended as fluvial (Devonian). At this final Silurian–Devonian stage, the Midland Valley arc was dominated by effusive rocks which made a substantial contribution to the sediments.In this interpretation, the present Old Red Sandstone volcanic rocks are seen as the final stage of a volcanic arc which occupied the position of the present Midland Valley from at least Llanvirn to Early Devonian time.

Terranes

1992 ◽  
Vol 13 (1) ◽  
pp. 1-4 ◽  
Author(s):  
B. J. Bluck ◽  
W. Gibbons ◽  
J. K. Ingham
Keyword(s):  
Hanging Wall ◽  
Fault System ◽  
Upper Proterozoic ◽  
Lower Proterozoic ◽  
Central Highland ◽  
Thrust Zone ◽  
Lower Palaeozoic ◽  
Moine Thrust Zone ◽  
Shallow Marine Sediments ◽  
Northern Highlands

AbstractThe Precambrian and Lower Palaeozoic foundations of the British Isles may be viewed as a series of suspect terranes whose exposed boundaries are prominent fault systems of various kinds, each with an unproven amount of displacement. There are indications that they accreted to their present configuration between late Precambrian and Carboniferous times. From north to south they are as follows.In northwest Scotland the Hebridean terrane (Laurentian craton in the foreland of the Caledonian Orogen) comprises an Archaean and Lower Proterozoic gneissose basement (Lewisian) overlain by an undeformed cover of Upper Proterozoic red beds and Cambrian to early mid Ordovician shallow marine sediments. The terrane is cut by the Outer Isles Thrust, a rejuvenated Proterozoic structure, and is bounded to the southeast by the Moine Thrust zone, within the hanging wall of which lies a Proterozoic metamorphic complex (Moine Supergroup) which constitutes the Northern Highlands terrane. The Moine Thrust zone represents an essentially orthogonal closure of perhaps 100 km which took place during Ordovician-Silurian times (Elliott & Johnson 1980). The Northern Highlands terrane records both Precambrian and late Ordovician to Silurian tectonometamorphic events (Dewey & Pankhurst 1970) and linkage with the Hebridean terrane is provided by slices of reworked Lewisian basement within the Moine Supergroup (Watson 1983).To the southwest of the Great Glen-Walls Boundary Fault system lies the Central Highlands (Grampian) terrane, an area dominated by the late Proterozoic Dalradian Supergroup which is underlain by a gneissic complex (Central Highland Granulites) that has been variously interpreted as either older

VI.—The Altered Clastic Rocks of the Southern Highlands, their Structure and Succession

1896 ◽  
Vol 3 (4) ◽  
pp. 167-174 ◽  
Author(s):  
Peter Macnair
Keyword(s):  
Red Sandstone ◽  
North West ◽  
Scottish Highlands ◽  
Clastic Rocks ◽  
The North

In the following paper I propose to give an account of some observations upon the structure and succession of the rocks of the Southern Highlands. By the term Southern Highlands I mean that part of the Scottish Highlands lying immediately to the north-west of the great line of fault separating the older rocks of the former area from the younger Old Red Sandstone series of the low grounds.

scholarly journals Precambrian metamorphic complexes in the East Greenland Caledonices (72°–74°N) – their relationship to the Eleonore Bay Group, and Caledonian orogenesis

1981 ◽  
Vol 104 ◽  
pp. 5-46
Author(s):  
A.K Higgins ◽  
J.D Friderichsen ◽  
T Thyrsted
Keyword(s):  
Metamorphic Complex ◽  
East Greenland ◽  
Late Proterozoic ◽  
Isotopic Studies ◽  
Lower Palaeozoic ◽  
Caledonian Orogeny ◽  
Proterozoic Basement ◽  
Basement Gneiss ◽  
Metamorphic Complexes ◽  
Middle Proterozoic

Results are presented of regional geological reconnaissance and local detailed studies. The new fjeld work, together with isotopic studies, has made possibie a provisional reassignment of metamorphic, plutonic and deformational events recorded in the different rock units to Archaean and Proterozoic, as well as Caledonian, orogenic episodes. The infracrustal elements of the 'central metamorphic complex' are considered to be essentiaIly Archaean - early Proterozoic basement gneiss complexes, and are overlain by middle Proterozoic metasedimentary sequences. The late Proterozoic and Lower Palaeozoic sediments have arestricted outcrop at present levels of exposure. During the Caledonian orogeny the late Proterozoic cover sequences appear to have become detatched from their older metamorphic 'basernent' along a decollement surface, but the nature of this contact is usually obscured by Caledonian metamorphic effects. The main characteristics of the different rock units are described. Detailed relationships are illustrated by studies of four areas: Nunatakgletscher-Eremitdal, Knækdalen and adjacent areas, Kap Hediund, and Tærskeldal-Forsblads Fjord-Randenæs.

Thermal Maturity of Lower Palaeozoic Shales in North-West Europe - Calibration of Proxies

2012 ◽  
Author(s):  
N. H. Schovsbo ◽  
J. M. Moron ◽  
A. T. Nielsen ◽  
G. Nicolas ◽  
H. I. Petersen ◽  
...  
Keyword(s):  
Thermal Maturity ◽  
North West ◽  
Lower Palaeozoic

Paleogeographie devonienne et mineralisations ferrugineuses de Dielette (Manche) et plombo-zinciferes de Surtainville (Manche)

1964 ◽  
Vol S7-VI (1) ◽  
pp. 121-126 ◽  
Author(s):  
Marie Jose Pavillon
Keyword(s):  
Shallow Water ◽  
Early Devonian ◽  
Lead Zinc ◽  
Caledonian Orogeny

Abstract Marine clastic formations of Cambrian, Ordovician, and Silurian age in the Flamanville area of northwestern France were folded during the Caledonian orogeny into a series of broad anticlinal and synclinal folds with the tops of the anticlines emergent and undergoing erosion by early Devonian time. The earlier Devonian formations were formed by deposition of the detritus in the adjacent synclinal troughs. Later deposits formed after renewed subsidence show facies differences between the marine shallow-water areas of the anticlinal crests, the deeper water of the flanks, and the deepest water of the synclinal troughs. Ferruginous oolite beds occur in marine sandy shales in the northern part of the area, and veinlets of lead-zinc mineralization occur in the southern part. The minerals probably were deposited in the original sediments, and later metamorphosed by intrusion of the Flamanville granite whose contact-metamorphic effects are prominent. The iron mineralization probably was deposited in marine shallows, and the lead-zinc minerals in adjoining belts.

An Early Devonian lake and its associated biota in the Midland Valley of Scotland

1995 ◽  
Vol 86 (4) ◽  
pp. 233-246 ◽  
Author(s):  
N. H. Trewin ◽  
R. G. Davidson
Keyword(s):  
Volcanic Activity ◽  
Fish Fauna ◽  
Early Devonian ◽  
Red Sandstone ◽  
Drainage Patterns ◽  
Terrestrial Environments ◽  
Climatic Regime ◽  
Lake Floor ◽  
The 19Th Century ◽  
Green Clay

ABSTRACTThe Tillywhandland fish bed of the Lower Old Red Sandstone in the Strathmore area of the Scottish Midland Valley accumulated in a lake, here called Lake Forfar, which was created suddenly following a period of fluvial deposition. Lake creation may have been due to basin faulting or the disruption of drainage patterns by contemporaneous volcanic activity. The fish bed laminites accumulated in a hydrologically open lake under a seasonal climatic regime. When fully developed, laminites comprise repeated quadruplets of clastic silt/carbonate/organic/green clay–shale laminae averaging 0·5 mm in thickness. Following 2000 years of laminite deposition an increasingly silty succession with thin current-rippled sandstones provided the lake-fill.The fish fauna is dominated by Mesacanthus and Ischnacanthus with rare Euthacanthus, Parexus, Climatius, Vernicomacanthus and Cephalaspis. Most fish carcasses were partially decayed before deposition in the laminites on the poorly oxygenated lake floor. Abundant coprolites are the result of predation on Mesacanthus and small Ischnacanthus, probably by larger Ischnacanthus. Arthropods present include eurypterids (Pterygotus), washed in as near complete exuviae and fragments, and millipeds which were washed in from surrounding terrestrial environments along with plants, of which Parka and Zosterophyllum are common. Bioturbation indicates that conditions were not permanently anoxic during deposition of the laminites.Comparison of our collections with the Mitchell Collection accumulated in the 19th century indicates that Tillywhandland Quarry was the main source of specimens in laminite lithologies labelled ‘Turin Hill’.

GEOLOGY AND HYDROCARBON POTENTIAL OF THE SOUTHERN GEORGINA BASIN, AUSTRALIA

2001 ◽  
Vol 41 (1) ◽  
pp. 139 ◽  
Author(s):  
G.J. Ambrose ◽  
P.D. Kruse ◽  
P.E. Putnam
Keyword(s):  
Early Carboniferous ◽  
Source Rocks ◽  
Peak Oil ◽  
Middle Cambrian ◽  
Late Cambrian ◽  
Oil Generation ◽  
World Class ◽  
Lower Palaeozoic ◽  
Southwestern Margin ◽  
Intracratonic Basin

The Georgina Basin is an intracratonic basin on the central-northern Australian craton. Its southern portion includes a highly prospective Middle Cambrian petroleum system which remains largely unexplored. A plethora of stratigraphic names plagued previous exploration but the lithostratigraphy has now been rationalised using previously unpublished electric-log correlations and seismic and core data.Neoproterozoic and Lower Palaeozoic sedimentary rocks of the southern portion of the basin cover an area of 100,000 km2 and thicken into two main depocentres, the Toko and Dulcie Synclines. In and between these depocentres, a Middle Cambrian carbonate succession comprising Thorntonia Limestone and Arthur Creek Formation provides a prospective reservoir-source/seal couplet extending over 80,000 km2. The lower Arthur Creek Formation includes world class microbial source rocks recording total organic carbon (TOC) values of up to 16% and hydrocarbon yields up to 50 kg/tonne. This blanket source/seal unconformably overlies sheetlike, platform dolostone of the Thorntonia Limestone which provides the prime target reservoir. Intra- Arthur Creek high-permeability grainstone shoals are important secondary targets.In the Toko Syncline, Middle Cambrian source rocks entered the oil window during the Ordovician, corresponding to major sediment loading at this time. The gas window was reached prior to structuring associated with the Middle Devonian-Early Carboniferous Alice Springs Orogeny, and source rocks today lie in the dry gas window. In contrast, high-temperature basement granites have resulted in overmaturity of the Arthur Creek Formation in the Dulcie Syncline area. On platform areas adjacent to both these depocentres source rocks reached peak oil generation shortly after the Alice Springs Orogeny; numerous structural leads have been identified in these areas. In addition, an important stratigraphic play occurs in the Late Cambrian Arrinthrunga Formation (Hagen Member) on the southwestern margin of the basin. Key elements of the play are the pinchout of porous oil-stained, vuggy dolostone onto basement where top seal is provided by massive anhydrite while underlying Arthur Creek Formation shale provides a potential source.

The last pteraspids (Vertebrata, Heterostraci): new material from the Middle Devonian of Alberta and Idaho

2020 ◽  
Vol 94 (4) ◽  
pp. 758-772
Author(s):  
David K. Elliott ◽  
Linda S. Lassiter ◽  
Kathryn E. Geyer
Keyword(s):  
Middle Devonian ◽  
New Genus ◽  
New Combination ◽  
Additional Material ◽  
Lower Paleozoic ◽  
Early Devonian ◽  
Red Sandstone ◽  
Large Channel ◽  
New Material ◽  
Paleozoic Rocks

AbstractThis report documents the last pteraspids, (armored, jawless members of the Heterostraci), which are otherwise only known from the Early Devonian of the Old Red Sandstone Continent. Tuberculate pteraspid heterostracans are described from the Middle Devonian beds of two formations in western North America. The late Givetian Yahatinda Formation of Alberta and British Columbia consists of channels cut into lower Paleozoic rocks and represents deposition in marine to littoral environments. Clavulaspis finis (Elliott et al., 2000a) new combination is redescribed from additional material from the Yahatinda Formation and reassigned to the new genus Clavulaspis because the original genus name is invalid. The Eifelian Spring Mountain beds of Idaho consist of a large channel that represents a clastic-dominated estuarine environment. It contains Scutellaspis wilsoni new genus new species, and the previously described species from the Spring Mountain beds is redescribed and reassigned to Ecphymaspis new genus, which was prompted by new material and a review of the validity of the original genus name. Phylogenetic analysis shows that these three new taxa form part of the derived clade Protaspididae.UUID: http://zoobank.org/9cf09b21-cec1-4ce4-bc2b-658d0b515e10

X.—A Gravity Survey in Ayrshire and its Geological Interpretation

1966 ◽  
Vol 66 (10) ◽  
pp. 239-265 ◽  
Author(s):  
Adam C. McLean
Keyword(s):  
Gravity Field ◽  
Bouguer Anomaly ◽  
Gravity Survey ◽  
Normal Faults ◽  
Red Sandstone ◽  
Geological Interpretation ◽  
The North ◽  
Close Relationship ◽  
Lower Palaeozoic ◽  
Western Limb

SynopsisBouguer anomaly maps covering most of Ayrshire at a density of about one station per sq. km., show a close relationship between anomalies and the distribution of the Upper Palæozoic rocks in the area south of the Inch-gotrick Fault, but are less clearly interpreted to the north, where thick dense igneous masses are present.In central and south Ayrshire the gravity field may be largely interpreted in terms of the known density-contrasts at the interfaces separating Upper and Lower Old Red Sandstone, and Lower Old Red Sandstone and Lower Palæozoic rocks. The major structure, the Mauchline Basin, is reflected clearly in the largest anomaly, and there is evidence of a culmination of its south-western limb near Kirkoswald. The important N.E.–S.W. faults also give rise to large anomalies, which may be connected with the known geology. It is inferred that they moved as normal faults in Carboniferous times, and that the adjacent synclines are essentially sags associated with the fault displacements. There is geophysical evidence that both the Southern Upland and Kerse Loch Faults existed in Middle O.R.S. (proto-Armorican) times. It is concluded that a hypothesis of N.–S. Armorican stress is not valid in south Ayrshire.In north Ayrshire, many of the anomalies are best explained by changes of thickness of the Millstone Grit lavas and of the Clyde Plateau lavas, and by the presence of thick dolerite intrusions. Additional evidence is needed, however, before final conclusions may be drawn.

Sign in / Sign up

Export Citation Format

Share Document