An introduction to the Quaternary geology and geomorphology of the area around Fort Augustus, Great Glen
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Abstract:
Fort Augustus lies within the Great Glen at the south-western end of Loch Ness (Merritt et
al., 2013, fig.17). The settlement straddles the Caledonian Canal, which follows the valley of
the River Oich south-westwards towards Loch Oich and, eventually, Fort William. The
landforms and deposits in the vicinity of Fort Augustus include drift limits, kame-and-kettle
topography and raised lake shorelines. They provide important information for interpreting
events that occurred during late-glacial times, in particular, evidence for re-depression of the
Earth's crust by the build-up of ice in the western Highlands during the Loch Lomond Stadial
(LLS) (Firth, 1986, 1989), and for catastrophic drainage of the former ice-dammed lake in
Glen Spean and Glen Roy, some 30 km to the south-west, towards the end of the Stadial
(Sissons, 1979a, 1981). Three sites are described here; Borlum (NH 384 084), the ‘north
shore’ of Loch Ness (NH 386 105) and Auchteraw (NH 364 082) (Fig. 1). A summary of
each site is given below together with some new information obtained from a recent
geological survey of the district (BGS, 2012). All modern BGS mapping around Fort
Augustus is available digitally or as paper maps at the 1:10,000 scale.Keywords:
Stadial
Firth
Solifluction
Landform
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In recognition of its outstanding geology, the coast between Orcombe Rocks
in south-east Devon and Old Harry Rocks in south Dorset was granted World
Heritage status in December 2001. The geology of this coast is described,
together with the recently mapped 1:50 000 geological sheets 328 Dorchester,
341/342 West Fleet and Weymouth and 342/343 Swanage.
The diverse geology ranges from the Late Permian to Quaternary, representing
more than 200 million years of geological time and many different ancient
environments that included arid desert, subtropical seas and cold periglacial
conditions. The stratigraphy is described in detail and incorporates revisions of
the Triassic, Jurassic, Cretaceous and Palaeogene successions. The region is justly
renowned for its rich variety of fossils, found especially in the Lower Jurassic rocks
around Lyme Regis and Charmouth. Many scientifically important specimens
have come from these crumbling mudstone cliffs, including marine reptiles first
made famous by the work of the 19th century Lyme Regis fossil collector Mary
Anning.
During the Quaternary, the district lay beyond the influence of the glaciers
and outwash that covered much of northern Britain. Head and the residual claywith-
flints are the main deposits preserved from that period together with river
alluvium and terrace deposits.
The structural geology is described in the context of basin evolution. This area
was part of the Wessex–Channel Basin that developed throughout the Mesozoic.
Numerous borehole records provide the basis for a detailed assessment of thickness
variation and this is related to structural development. Mesozoic structures
continued to influence later structural development. Periods of earth movement
associated with the uplift of the Alps in southern Europe caused parts of the succession
to be spectacularly folded, as seen for example at Durdle Door (Cover
photograph).
Many past geomorphological studies have emphasised the close relationship
between geology and the development of coastal landscape in the region, and
there are a number of spectacular natural arches and sea stacks. Landslips, both
active and dormant, are described and occur in a variety of forms unrivalled in
the UK. Inland too, the influence of geology on the landscape is very strong,
from the high rolling chalk downland north of Dorchester to the lower lying
sandy heaths formed of Cenozoic (Palaeogene) sediments farther east around
Wareham. In the Isle of Purbeck, picturesque Corfe Castle sits astride the sharply
defined east–west ridge of the Purbeck Hills, formed by steeply dipping beds of
chalk, part of a huge monoclinal fold that extends eastwards to the Isle of Wight.
Geology has also played a part in the development of the region, summarised
in the Economic geology chapter. This region supplied the Portland Stone and
Purbeck Marble that has been used in many great cathedrals and civic buildings.
Palaeogene clays are an important source of raw material for ceramics, and the
Wytch Farm Oilfield, near Bournemouth, is the largest onshore oilfield in the
UK.
The text is fully referenced, and additional information includes a borehole
and a fossil inventory.
The geological succession tabulated opposite summarises the age, stratigraphical
classification, lithology and thickness of the rock types seen in south Dorset
and on the World Heritage Coast.
Anticline
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I. Introduction The present paper is a sequel to my paper on the “Recumbent Folds in the Schists of the Scottish Highlands”, published in this journal in 1910, and expanded with certain corrections and discussions in a Geological Survey Memoir on the “Geology of Ben Nevis and Glen Coe”, 1916. The existence of these two publications allows of concentration on new features of interpretation. The Loch Leven referred to in the title is the salt-water loch of that name, between Argyll and Inverness-shire. The coastal parts of the district are well served by roads, railways, and steamers. There are also inland roads through Glen Etive, Glen Coe, Glen Spean, and Glen Roy. The main villages or small towns are Ballachulish, Kinlochleven, Onich, Fort William, and Spean Bridge. Accommodation is easy to get. The geological facilities include good exposures, high relief, and wonderfully definite lithology. Some of the mountains are carved out of Devonian igneous rocks, as at Ben Nevis and around Glen Coe, but much the greater number consist of the schistose rocks which concern us here. These peaks include a large number rising well above 3000 feet in height, and one, Aonach Beag, surpassing the 4000-foot level. When I described the Ballachulish stratigraphical succession in 1910, and again in 1916,1 was careful not to suggest an original order of superposition . I described recumbent folds, but left it to the future to decide which set of limbs was normal and which inverted. In 1922, however, I attempted a comprehensive treatment
Lithology
Devonian
Shire
Sill
Geological survey
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Citations (73)
This sheet explanation provides a summary
of the geology of the Isle of Wight district
(Special Sheet) arising from the British Geological
Survey’s Isle of Wight Integrated
Project. This project, commenced in September
2007 and completed in 2013, sought
to improve the understanding of the nearsurface
geology, and create representational
models of the 3D structure. This will
provide essential framework information
for use by the geological community operating
in this classic area of British geology.
This sheet explanation and accompanying
1:50 000 scale geological map special sheet
are principally aimed at users in academia,
local authorities and statutory bodies, but
also at the large number of ‘geotourists’ that
are such an important part of the island’s
economy. A Special Issue of the Proceedings
of the Geologists’ Association (Geologists’
Association, 2011) introduced by Hopson
(2011) gives further detailed accounts of the
recent work by BGS on the island.
The Isle of Wight (Figure 1), the largest
island in England at 384 km2, is separated
from the mainland by the Solent. This body
of water is essentially the drowned lower
reaches of an extensive Quaternary river
system draining much of southern central
England. The island’s protective presence
offshore of the south coast within the
English Channel strongly influences the
tidal regime within the Solent system and
led directly to the development of Southampton
and Portsmouth as major ports.
Large parts of the island form Areas of Outstanding
Natural Beauty (ANOBs) and a
considerable length of the coastline in the
south-west and north-west of the island is
designated as Heritage Coast (Figure 2).
Topographically the diamond shape of
the island is the direct result of the presence
of a central, east–west orientated
ridge, of complex tectonic origins, founded
on the steeply dipping, moderately hardened,
Chalk Group (Figure 3). The softer
sediments of the Palaeogene forming
lower-lying, ground within the northern,
mainland-facing, part of the island are protected
from extensive tidal erosion by this
Chalk ridge. To the south-west of the central
ridge, sediments of the Early Cretaceous,
forming low cliffs, suffer extensive
erosion from Atlantic storms funnelling up
the Channel. The south-eastern coast, eastward
of St Catherine’s Point, is protected
by a capping of more durable, essentially
horizontal Upper Greensand and Chalk
strata forming the Southern Downs but here
an extensive, deeply seated, landslide (the
largest in north-west Europe) considerably
modifies the coastal geomorphology.
Wight
Mainland
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I. I ntroduction . The region dealt with in this paper is roughly triangular in shape, extending from its northern apex at Blackstone Edge, east of Littleborough, to beyond Crich in the south-east, and along the southern line of the Pennines to Madeley and Market Drayton in the south-west. It comprises the Carboniferous Limestone plateau of the Derbyshire Dome, the ‘Edges’ of the grits, and the intervening valleys of the shales of the Millstone Grit of the south-western slopes of the Pennines, together with the marginal plains of Triassic rocks which border these in East Lancashire, Cheshire, Staffordshire, and Derbyshire. Some idea of the nature of the relief of the country may be gleaned from the accompanying map (Pl. XIX), and of the solid geology from the quarter-inch maps of the Geological Survey of England & Wales (Sheets 7 & 11). This area forms the southerly continuation of that described by one of us in an earlier communication to this Society. A brief outline of some of the main conclusions set out below was presented at the Manchester Meeting of the British Association in 1915. Numerous notes on the Glacial geology of this area, dealing chiefly with the distribution and character of the drifts and the erratics, are to be found scattered throughout English Glacial literature. Reference will be made to the most important of these, in the course of this paper, as occasion arises. The Glacial deposits, with their smooth and striated boulders which thickly cover the plains, the far-travelled erratics
Dome (geology)
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Official work on the Nantwich district (Sheet 122) showed t h a t the sequence of two boulder-clays with associated fluvioglacial deposits, previously recognized only in the northern part of the Shropshire–Cheshire basin, also extended into its centre. Subsequent private research has shown that this sequence may be distinguished throughout the whole basin and in a critical region beyond its south-eastern margin—in total an area exceeding 3000 square miles. The recognition of glacial lake features cut into the Upper Boulder-clay in the Nantwich district and elsewhere necessitates a revision of current ideas about the origin of Lake Lapworth and the age of the Severn terraces above Ironbridge. Accepted correlations relating to the basin and its adjacent areas, the status of the “Little Welsh Glaciation” and the Newport–Wolverhampton esker chain are discussed. A new interpretation of the Pleistocene and Recent history of the region is presented.
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Citations (27)
De Witt Island, off the south coast of Tasmania, is composed of a folded succession of turbiditic silstone, sandstone and conglomerate, at least 450 m thick.It is probably a correlate of the Mid to Upper Cambrian lronbound Group.Folds are upright, open to tight, and at least two generations are indicated.The broad-scale geomorphology of the island is controlled by the direction of storm waves which have eroded nearly vertical cliffs up to 340 m high on the south shore.Many sea caves are found at the base of the cliffs, particularly on the west and sourh coasts.Cliff retreat has progressively captured the headwaters of the island's two perennial streams.Fluvial processes, controlled by both lithology and structure, bur also showing possible influence from interglacial and glacial stages, have shaped the interior of the island for a long period.Aeolian processes have deposited sand sheets in the island's central basin.Some well-developed pseudokarst systems, including sinkholes, caves, underground drainage and airflows, are related to large rotational slumps on the island's south coast.
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This Sheet Description provides an account of the geology
of the district covered by Geological Sheet 153
Wolverhampton. The district extends from the edge of the
Black Country conurbation in the south-east, to Telford in
the west, and includes a large tract of rural Green Belt on
the Staffordshire–Shropshire borders. The solid rocks at
outcrop range from Precambrian to Triassic in age. The
oldest rocks, pyroclastic tuffs, originated in an island-arc
setting in south polar latitudes; the youngest are
continental red-beds that formed in inland sabkha
environments, when Britain lay just north of the equator.
Although the geological record spans about 560 Ma, the
modern landscape has been shaped largely by geological
processes that operated during the last two million years.
Successive glaciations have modified the landscape, and the
superficial deposits of till and glacial outwash that blanket
much of the district are the product of a Late Devensian
glaciation. The Ironbridge Gorge and other meltwater
channels also date from this period. Since the ice retreated
about 13 000 years ago, the postglacial history has been one
of drainage development, valley incision and terrace
aggradation.
The district has a long industrial heritage dependent, until
recently, on the mineral wealth of the Carboniferous rocks
exposed in the South Staffordshire and Coalbrookdale
coalfields. During the 18th and 19th centuries, settlements
grew and prospered as industries were established, founded
on a plentiful supply of coal, clay, ironstone and limestone.
The relicts of these industries have left parts of the district
with a legacy of difficult ground conditions, aspects of
which are described in the applied section of this report.
Today, mineral extraction is of less importance but
brickclay, fireclay and some opencast coal are still
produced, and the Triassic conglomerates are an important
source of aggregate. The Permo–Triassic rocks of the
Stafford Basin hold important groundwater resources from
which large volumes of water are abstracted for public
supply.
Outwash plain
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Citations (4)
This report describes the surface geology of the 1:10 000 Series sheet
SD 55 NW, part of the 1:50 000 Series sheet 59 (Lancaster). Detailed
descriptions of the geological sequence encountered in the Wyresdale Tunnel,
which crosses beneath the eastern part of this area, can be found in Johnson
(1981) and Wilson et al. (1989).
The area was first mapped at the 1:10 560 scale by J.R. Dakyns and
R.H. Tiddeman in 1875-76 and published at the 1:10 560 scale in 1880 as parts
of the Lancashire County Series sheets 30, 31, 34 and 35. In 1884 the
geological information was published at the 1:63 360 scale as part of the Old
Series sheet number 59 (Lancaster). During the present survey, the area to
the south-east of the Quernrnore to Garstang road (approximately three quarters
of the sheet) was mapped by Dr A.A. Wilson in 1984, as part of the BGS work
commissioned by the North-west Water Authority in response to the Abbeystead
Explosion Public Enquiry. Several, significant and previously unknown marine
band localities were discovered by Dr Wilson during this survey. The remainder
of the sheet was surveyed by Dr R.A. Hughes in 1988. A limited amount of field
work was carried out by Dr A Brandon in 1990 and parts of the geological
mapped revised.
The area is one of hilly pastureland, marginal to the high, heather covered
moorland of the Bowland Fells to the north-east. The rugged escarpment of
Clougha extends into the north-east corner of the sheet, the highest point
[5492 5939] being 421 m above Ordnance Datum. In the west, the north-east
trending valley of the River Conder is the major topographical feature, and
drains to the south. The lowest point is at the western end of the Conder
valley [579 500], where elevation is less than 45 m above Ordnance Datum. To
the east of the Conder valley the main lines of drainage flow from north to
south along a series of glacial meltwater channels. The only centre of
habitation is the ribbon development of Quernrnore [59 51].
The north-eastern part of the area was mapped by Moseley (1954). A detailed
geological log of the Wyresdale Tunnel, constructed to link the drainage
systems of the Rivers Lune and Wyre, was made by E.W. Johnson, N.
Aitkenhead, J.I. Chisholm, R.S. Arthurton, and D.J.C. Mundy of the BGS,
during construction. The results were published in a sedimentological
synthesis by Johnson (1981), who described the succession in terms of a
prograding delta-front sequence. Following the Wyresdale Tunnel explosion in
May 1984, the BGS surveyed the area in an attempt to identify the source and
the trap of the methane which exploded. A description of the geology as found
during this survey is given in Wilson, Brandon, and Johnson (1989). All
fossils recorded in this report were identified by Dr N.J.Riley.
Subsequent to the preparation of the original draft report the stratigraphy
and geological map of the area has been revised, particularly with regards to
the Roeburndale Formation. This report therefore includes parts revised by Dr
A Brandon in consultation with Or A A Wilson.
Escarpment
Geological survey
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Synopsis Excavations in 1958 for the construction of a dam at Loch Droma, Ross and Cromarty, revealed a deep and extensive section in peat and Late-glacial silts. The section was surveyed, its environs studied, and samples of materials analyzed by the Macaulay Institute, Aberdeen, and the Sub-department of Quaternary Research, University of Cambridge. The watershed location of the site, the early radio-carbon date obtained for the basal silts (12,810 ± 155 B.P.), and the nature of their organic contents, make this a critical site for the elucidation of the deglaciation and vegetational history of the Atlantic seaboard of North-west Scotland. In Part I of this report, W. Kirk describes the site and its setting, and indicates some of the problems it raises for existing glacial chronologies of Northern Scotland, and in Part II, H. Godwin summarizes and comments upon the analyses of organic remains.
Deglaciation
Section (typography)
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Citations (66)