West, Ian M. 2014. Geology of Torquay, Devon; Part of Geology of the Wessex Coast Website, Ian West and Southampton University. With photographic contribution by Nikolett Csorvasi. Internet site: www.southampton.ac.uk/~imw/Torquay.htm. Version: 23rd February 2014.



INTRODUCTION: Maps, Topographic

Go to the:

ORDNANCE SURVEY MAP SHOP for details of Ordnance Survey maps of the Torquay area. Although examples of modern Ordnance Survey maps are not shown for copyright reasons, these maps are recommended and can obtained in digital form or as traditional folded paper maps.

The above map is old and out-of-date, but mainly with regard to buildings and new roads. The coast has changed very little becaause it is mostly a hard rock coast. This particular map results from a 1929 survey and has been produced in 1946, shortly after the Second World War with some corrections. Since then development seems to have been heading in the Hope's Nose direction, but at least at the time of the survey much of the Kilmorie area seems to have remained relatively natural. Property development has fortunately stopped short of Hope's Nose, which is now preserved as a Site of Special Scientific Interest.

INTRODUCTION; Geological Maps

Shown above is a very old and generalised geological map of Devon. It provides some introductory information and is of historic interest. Real geological detail is provided by the British Geological Survey Sheet referred to below.

The simplified geological map above shows that the southeastern part of Torquay is a promontory of relatively resistant Devonian strata. It includes small hilly outcrops of Devonian limestone within or adjacent to areas of Devonian shales and slates. Northeast and southwest of this Devonian area there are outcrops of softer Permian red beds.

Part of the 1913 edition of the geological map of the Torquay area is shown above. This is the Drift Edition, at one inch to one statute mile, surveyed on the six inch scale by W.A.E. Ussher. It was published with Drift in June 1898 and additions were made in 1912. The underlying topographic, Ordnance Survey Map was surveyed in 1861 to 1889 and revised in 1908-1909. It was reprinted without alteration in 1953. The modern replacement, shown below, has differences with regard to faults, and has more detail and modern nomenclature. The new map is essential for specialist and research work and for specific details with regard to building and property; it should be purchased from the BGS. The old map is still usable for introductory and elementary educational purposes. In general, the new map is more likely to be correct. Some faults and fine details will always be a matter of opinion, though. In the built-up area some exposures in old quarries etc may have been visible in the past but are not now exposed. Thus it is always good to consult both new and old editions when studying an area.

When considered in more detail, the geology of the Torquay area is quite complicated and not as simple as at Teignmouth and Dawlish to the northeast. The British Geological Survey map shows much faulting and some folding. The complications are to be expected because much of the area consists of strata below the Permian and has thus been involved in the Hercynian Orogeny. The current BGS sheet, as shown above, is Torquay, 350, Solid and Drift, 1:50:000 Series, published 2004, and is available with an explanatory booklet by Leveridge et al. (2003). Purchase of the map and explanatory booklet is recommended and they are necessary items for anyone studying the area.

INTRODUCTION: Aerial Photograph - Introductory

(Go down for more aerial photographs)

INTRODUCTION: Safety and Risk Assessment

There is an obvious hazard of falling from the various steep cliffs around the Torquay area. Great care needs to be taken when descending into old quarries or scrambling over rocks near the shore. In places there is some risk of rock fall. There has been a major rock fall at Oddicombe Bay, Babbacombe recently. Further rock falls may occur here and the area should not be considered safe. There is a warning notice. At any cliff locality watch out for evidence of recently fallen rock debris and avoid such places. Take care with regard to tide and check the tide times to avoid risk of being cut off by a rising tide. The shore rocks are often covered or partially covered in seaweed and can be very slippery. Take care with such rocks.

LOCATION: Thatcher Rock

Thatcher Rock is a small island of Middle Devonian Limestone. It is shown here with Berry Head, also of Devonian limestone in the distance across the bay. The same raised beach that is present at nearby Hope's Nose also occurs on Thather Rock.





MEADFOOT BEACH AND TRIANGLE POINT





You can see that you can easily drive straight to Meadfoot Beach. Car parking is easy in the off-season. Sometimes you can park on the left hand side of the road shown here, but if not there is a pay-and-display car park further on, as shown. The cliffs are wooded and rugged but some modern urban development here seems a little strange and out-of-place when observed from beach level. In fact though the area above the cliffs is all much built up, but mostly with older buildings or conventional housing. Some of the natural beauty of the area has long gone, but the general coastline is still very interesting and picturesque; it is very good that it has been preserved in a such a busy town. In addition, as mentioned by Perkins (1971) geologists have actually benefitted from the development of the region because it resulted in extensive quarrying in the coastal areas of Torquay. Dyer's Quarry, Knoll Quarry, Long Quarry Point etc. are good exposures resulting from human activity.

The road and sea wall at Meadfoot Beach has probably covered many natural exposures. At low tide, though, there are good exposures on the beach. There are also fairly low cliffs at the foot of the rugged slopes beneath Kilmorie, further east.

Meadfoot Bay, shown above, is the type locality for the Lower Devonian Meadfoot Group. The exposure in Torquay is not confined to this bay but continues further east along the coast at the foot of Kilmorie, and beyond Thatcher Rock and on towards Hope's Nose. Meadfoot Bay is a place of easy access with convenient car parking. However there is no cliff section within the main part of the bay because of a road and a sea wall. There exposure on the beach where there are many ledges and projecting rocks, particularly of sandstone. However, this beach section is only visible at low tide. It is variable to some extent with regard to beach sand and pebbles. The lower, more seaward parts are partially obscured by barnacles, seaweed (less in 2010 thin in previous years) and other marine life. It is also somewhat tectonised. Nevertheless, it shows some some good features if thorough and careful examination is made.

The Meadfoot Group ('Meadfoot Beds') is mostly Emsian at Meadfoot according to Leveridge et al. (2003). The stages of the Lower Devonian are from bottom to top - Lochkovian, Pragian, and Emsian. The Emsian, the top of the Lower Devonian, ranged from about 407 million years ago to about 397.5 million years ago. The Emsian strata here are succeeded mainly by the Daddyhole Limestone Member of the Middle Devonian, seen at Triangle Point.

Shown above is an exposure of Meadfoot Group mudstones seen at low tide within the main part of Meadfoot Beach. They do not resemble typical shale. They are quite hard and seem to have a cleavage that is almost parallel to bedding. Thus they appear slatey and, although not very hard, may just come into the category of slates. Generally they are fairly unfossiliferous and relatively featureless. There is often though a transition into sandstone. At the top of the small sequence shown thin lenticular sandstone bodies appear. In places on this beach there is somewhat gradual change to thick sandstone beds, which form prominant ridges or ledges.

The photograph above shows lenses and laminae of sandstone developed within mudstone. Because there are slumped sandstone deposits and because there has also been much tectonism, it is not immediately clear whether the lensing has originated from slumping, channelling or boundinage.

More sandstone laminae, alternating with cleaved mudstone, are shown above. Notice that upper and lower surfaces of the thin sandstone beds usually have wavy surfaces. It is common, of course, for sandstone to show ripple marks. These, however, do not seem to be normal ripple marks. The upward bulge usually seems to coincide with the downward bulge, and this is not usually the case with sand ripple marks.

At places along the beach there are rather irregular, large blocky exposures of thick sandstone beds. This may be cross-bedded and of channel origin.

In general terms, then, the lithology of the Meadfoot Group at Meadfoot Beach can be summarised as consisting of grey, slatey, silty mudstone with beds of sandstone. The sandstone occurs both as thick beds and as thin laminae. Thin beds of bioclastic limestone have also been reported. The mudstone is bioturbated with Chondrites and Spirophyton common. The sandstone is cross-bedded and shows scour and slump structures and lenticular channel units of up to 8 metres thick ( Leveridge et al., 2003). The depositional setting was a shallow marine shelf with a southerly palaeoslope. This is indicated by the slumping and direction of main channels. Subordinate east-west channels have suggested a tidal influence ( Leveridge et al., 2003).

The Meadfoot Group is exposed in the relatively low, but rocky cliffs between Meadfoot Beach and Thatcher Point. The Ilsham Marine Drive is along the upper slopes above the active cliff. There are traffic lights at the western end of it, and there is of single vehicle width for a short stretch. This is apparently because of some limited cliff instability downslope. The cliffs of this stretch show many sedimentary structures in the Lower Devonian, Emsian, Meadfoot Group. There are slates, slaty mudstones, siltstone and sandstones present.

The Meadfoot Slates outcrop continues to the east. It includes Thatcher Point and south of Thatcher House. There is a cliff-top coastal footpath here. The slates form a rocky coast that is difficult to traverse, and at high tide the sea is up to the very irregular cliffs.

LOCATION: Triangle Point and East Shag Rock - Introduction

Triangle Point is a location at the southwest end of Meadfoot Beach (go for Meadfoot Sea Road, Torquay, on Google Earth or a satnav etc.). It is reached by walking along the promenade and then scrambling over some rocks at the promontory. Care needs to be taken because there is some risk of slipping on the rocks. Blocks can fall from the cliff above but this is not of common occurrence. The exposure at Triangle Point is very good but not large. It reveals a good display of corals and other fauna of a Devonian reef, some details of which are shown further down.

.

LOCATION: Triangle Point - Structures

The structures around Triangle Point and Daddyhole Cove are very interesting. The most notable aspect is the recumbent anticline which is shown in the maps and section of Scrutton (1978). The sequence at Triangle Point is inverted because of this structure. Note that there are many faults at the Point. The one shown in the photograph above is oblique. There are some conspicuous strike-slip faults in the eastern part of the small promontory.

An important fault here is the obvious one with oblique slip that is shown in the photograph. This is the southern marginal fault to the contorted stratal unit that passes westward into a gold-bearing breccia (see below with regard to Knoll Quarry). It warrants closer examination.

LOCATION: Triangle Point - the Middle Devonian, Torbay Reef

At Triangle Point the steep bedding planes show abundant stromatoporoids and corals. Goniatites and gastropods are also present. Note that this is a protected SSSI and no collecting is permitted; in any case the fossils do not separate from their very hard, solid limestone matrix. The stromatoporoids are linked and bound by chain-like growths of the tabulate corals. Some of these networks are preserved in place, as shown above. The dominant and most obvious corals are of the genus Thamnopora.

Goniatites in the Middle Devonian limestones at Triangle Point contain partial sediment fills. These can be geopetal structures which, in favourable circumstances can reveal the way-up. Paired brachiopod shells also show variation in the extent of sediment-fill. Studies of the geopetal structures here have shown that the strata are inverted. They are within part of an overturned anticlinal fold.

West of Triangle Point where the next quarry begins, there is a cleft on the shore where gold has been found. More detail is known about the gold at Hope's Nose. See: Scrivener et al. (1982).

LOCATION: Daddyhole (Daddy Hole) Cove and Knoll Quarry

The photograph above shows a natural rocky coast of inverted Devonian limestone that has been much modified by quarrying. The small embayment to the west of Triangle Rock is Daddyhole Cove. The cliffs have been quarried out here quite extensively in the Knoll Quarry. There is an easy path down to this quarry from the cliff top; it is not easily accessed directly from Triangle Rock. Notice in the photograph above the small arete with yellow lichen on the west side of Triangle Point. The next photograph shows more detail from the top of this little ridge.

LOCATION: Knoll Quarry - the Breccia with Gold

Note that the quantities of gold found here are small and of scientific value and not of commercial value. The gold deposit has been worked out. There is a substantial fine which can be 20,000 pounds, or no upper limit, for removing or damaging valuable specimens at SSIs in this area; see notice at Hope's Nose. Thus look for the location of the gold and examine the faults and structures to try to understand the geology of its occurrence. Do not remove anything of value or significance but enjoy the search for gold and the academic study of its origin! Perhaps then look for new gold occurrences elsewhere in the region.

"At the point E (Fig. 8) the two faults almost meet, and the beds in the narrow belt between them are pinched and highly contorted [as shown above]. The northerly fault can be traced along the seaward margin of The Knoll quarry, by a fault breccia 1 - 2 feet wide and filled with earthy matter, broken limestone and calcite: traces of gold have been found in this breccia but an attempt many years ago to exploit the discovery proved unsuccessful."

(Ussher, 1933, page 55).









LOCATION: London Bridge - Natural Arch in Devonian Limestone (and Dyers Quarry)

Middle Devonian, Eifelian limestone is present within and adjacent to the impressive natural arch of London Bridge, Torquay. The stata here strike SE-NW and dip very steeply, at about 80 degrees in a SW direction, within the arch structure. Thinner bedded and less resistant limestones have been eroded away into a cave, with some collapse, and this has formed the natural arch.





HOPE'S NOSE

If you park your car in Ilsham Marine Drive above the Hope Cove area, it is easy to walk down to Hope's Nose.

On entering the natural area, choose either to go right down to the raised beach and the southeastern side of Hope's Nose peninsula, or proceed straight on down to the end of the promontory (as the anglers seems to do).

This notice seen in 2010, was not seen to be still present in 2012.

HOPE'S NOSE: Introduction, Topographic and Geological Maps

HOPE'S NOSE, Aerial Photographs

The above is a general aerial photograph of the Hope's Nose area for location purposes. Some much more detailed aerial photographs, courtesy of The Channel Coastal Observatory follow.

Note: The aerial photograph above is of particular interest in that it shows a large plume of pollution being swept southward from the sewage outfall. This outfall has now been stopped. Until recently it was probably responsible for the flourishing of seaweed on Meadfoot Beach. This is much reduced in 2010, as noted by Dr. John Jones, when studying with Southampton University students the marine life of the beach.

HOPE'S NOSE Shennell Cove (SX 946633) (West, between the Southwestern Promontory and Thatcher Point)

Descending to Hope's Nose by the southern footpath, the embayment, Shennell Cove, just west of the southwestern promontory is passed on the cliff top. The strata here are quite different from those at the Hope's Nose cliffs and promontory. They not of Middle Devonian limestone but are probably largely of the Lower Devonian, Meadfoot Group, slatey mudstones and sandstones.

[However, a note of caution must be added. On the 1898, Geological Survey Torquay Sheet 350, a significant, fault-bounded outcrop of Middle Devonian Slates and Shales are shown. In modern terminology these would be Nordon Formation, (Eifelian). If you examine the current 350 map you will notice that Nordon Formation does indeed occupy the upper part of the landward neck of Hope's Nose (i.e. where you would park your car). However, the map seems to show that the cliffs of Shennel Bay are mainly occupied by Meadfoot Group. I have not made adequate study of this and it would be good if you were able to re-examine the strata of Shennell Cove, with this problem in mind. For the present, here the strata are treated as Meadfoot Group (Emsian).]

The Meadfoot Group strata are predominantly dark grey clastics including brownish sandstones. Notice that the beach consists of fallen blocks of sandstone and some areas of pebbles. There is no large quantity of sand and this in contrast to the sandy deposits of the Hope's Nose Raised Beach which is nearby.

HOPE'S NOSE: Southwestern Extremity

The southwestern extremity of Hope's Nose is higher and steeper than the northeastern promontory. It forms the eastern headland of a small bay of Lower Devonian, Meadfoot Group mudstones and sandstones. There is no large shore platform of limestone here. The main reason is that the coast has been recently cut back in this area to the old cliff of the raised beach and beyond (landward). The beach itself is not present just here and therefore does not form a coastal fringe of low ground.

HOPE'S NOSE: Gold Occurrence

Introduction and General Location

(the exact location is not given)

Hope's Nose is a limestone promontory to the east of Torquay. It is composed of the Daddyhole Limestone Member of the Middle Devonian limestone. Of particular interest is the occurrence of dendritic gold in carbonate veins cutting this limestone in the vicinity of the sewage outfall at the eastern extremity of Hope's Nose. The photographs above show the general area of the gold occurrence, but not the exact locality or the specific veins.

While of considerable interest this gold occurrence is not a spectacular discovery and it is not something that you are likely to even find any trace of in the cliffs. These are merely microscopic traces of academic interest. They not likely to be of interest to collectors and note that there is a very substantial fine (of thousands of pounds) for attempting to remove them. The importance is that they might indicate that more gold occurs elsewhrere in this region. Indeed, other places in the vicinity might be more promising!

The traces of gold were first reported by Gordon (1922). Professor W.T. Gordon of Kings College, London was leading a field trip with students and was studying the faults at Hope's Nose when he discoved the gold. He presented specimens to the Torquay Museum . (The museum is 529 Babbacombe Road, Torquay, Devon.)

Gold occurrence is a relatively unusual occurrence in England, so this is a well-known site. The gold veins occur as a swarm in which individual veins are separated by up to 20 metres of host limestone ( Leveridge et al. (2003). The mineralisation is only in the massive stromatoporoid reef facies of the Daddyhole Member of the Torquay Limestone Formation. The veins trend roughly east-west as pods and lenses within steeply inclined fracture zones. The gold is associated with saccharoidal buff to cream-coloured calcite and dolomite. Cavities in these carbonate veins may contain iron oxides, such as goethite and hematite. High levels of palladium are associated with the veins ( Leveridge et al., 2003). The gold is present only in small quantities and has been best revealed by dilute acid digestion of carbonate from the veins. It is not something that is conspicuous or easy to find and not of great commercial value. See illustration in Leveridge et al. (2003). Its significance is that there may be more gold in the Devonian limestones elsewhere in the region. As mentioned above some has been found in Daddyhole Cove.

The Fracture Zone

This fracture zone is a useful marker for finding the area where traces of gold were once discovered. The fractures seem to have a similar trend, of about ENE.

This photograph is from near the gold locality, but is north, rather than south of the Fracture Zone. It shows a rather open, small fault with some fault breccia, including iron oxides such as goethite and another mineral. It is not known whether the fault has a strike-slip component.

HOPE'S NOSE (AND DADDYHOLE COVE) Gold Mineralisation - Further Notes Gold

As noted above, veins containing small quantities of gold occur in Devonian Limestone at Daddyhole Cove and at Hope's Nose. For detailed information on these interestng occurrences see particularly: Scrivener (1982) and Leveridge et al. (2003).). Some brief notes on the gold discoveres are given here.

The gold is present in calcite veins associated with the major Variscan tectonic activity, and in Middle Devonian limestone. In World terms the Devonian occurrence is not very unusual. There are important gold reserves in Devonian limestones in the USA, Serbia and elsewhere. Nevertheless, some special circumstances are required for this mineral to be hosted in such limestone. See for example the occurrence of gold in Devonian limestone at the Red Hill Project in Eureka County, Nevada. The occurrences at Torquay are regarded as curiousities of scientific interest, not as of real commercial value. To find important gold deposits in the area, it would not be worth-while undertaking a major search around the well-known localities of Hope's Nose and Daddy Hole. However, if the occurrences there are thoroughly understood, then the pointers might become known so as to guide searchers in the direction of gold-bearing veins in the Devonian limestones somewhere else (under the sea? in the large limestone outcrop of Wall's Hill? or where?).

Regarding the Devonian System, gold also occurs in association with Devonian hot spring mineralisation at Rhynie in Scotland (re the famous Rhynie Chert). See Baron et al. (2003) for details.

Torquay Gold - Further Notes Emplacing brines

Torquay Gold Further Notes to be added -

[notes to be added]

HOPE'S NOSE: Hope's Nose - Raised Beach - Introduction

(and Thatcher Rock Raised Beach)

Hope's Nose and the nearby Thatcher Rock is notable for the preservation of an interglacial raised beach deposit at 9 metres above sea-level, according to Leveridge et al. 2003b (in the literature various height are give, usually at about 8m above sea-level). This is said to be second raised shore platform of the district (Leveridge et al. 2003b). This pebble, shell and sand accumulation is approximately "Ipswichian" in age, i.e. a deposit of the last interglacial. It is similar to and probably a continuation of the low level raised beach or beaches of Portland Bill also about 8 metres above sea-level. The Portland raised beach has given dates, not necessarily very accurate, of 125,000 and 210,000 years. In very round figures the raised beach is of about 150 thousand years back.

The raised beach at Hope's Nose, Torquay (map ref. SX949637) has been described by Austen (1835; 1842), Pidgeon (1890), Prestwich (1892), Hunt (1888; 1903) and other authors. The exposure is 37 metres long at the southeastern end of the Hope's Nose promontory. It lies at about 7 or 8 metres above the high water mark of spring tides.

HOPE'S NOSE: Hope's Nose - Raised Beach - Shell Fauna

(and Thatcher Rock Raised Beach)

Mr. Arthur Roope Hunt (1888) started studying the raised beach on Thatcher Rock in 1881. When he had collected an assemblage of shell remains on the rock he sent them to a mollusc specialist:

In the spring of 1881, I forwarded a small parcel of shell-fragments, collected on the Raised Beach on the Thatcher Rock in Torbay, to the late Mr. J. Gwyn Jeffreys for identification. In return I received the following letter, dated 1st May, 1881.

"My Dear Sir, - I have examined and will return tomorrow your shell-fragments.

They are in one box,

Cardium echinatum and C. edule;

in the smaller box,

(1) Mytilus modiolus,

(2) Cyprina islandica,

(3) Venus gallina,

(4) Venus faciata,

(5) Tellina balthica,

(6) Solen vagina,

(7) Littorina littorea,

(8) Natica alderi,

(9) Buccinum undatum,

(10) Pleuromya turriculata,

(11) fragment of the bone of a dog or rabbit. Hunt continued with his report on his studies of the Thatcher Rock and Hope's Nose raised beach and included the list of molluscs, shown above. The most notable aspect is the abundance of Cardium edule, not apparently found in Torbay except in the neighbourhood of artificial harbours. The most common cockle of the bay now is Cardium aculeatum. This, remarkably was absent, and so too was the secondmost common cockle - Cardium tuberculatum. The gastropod Turritella terebra, which tends to be an offshore species (3 - 100 fathoms depth, roughly 6 metres to 200 metres) is particularly abundant and Hunt collected 76 fragments from a relatively small exposure of raised beach. In addition the estuarine Mya arenaria occurs. Telina balthica is very abundant but does not occur in Torbay, except in the mud of Paignton Harbour. It also occurs at present in sandy mud at the mouth of the Exe. The brackish water species were not derived from a landlocked estuary, but rather from some river's mouth in the open sea, according to Hunt. The notable solidarity of the shells of Cardium edule support this, because they are too thick for river cockles. He considered that the presence of the brackish-water shells would be account for by an extension of the mouths of the Teign and the Exe, either separately or combined, to the neighbourhood of Torquay, or to an open coastline, along which shells from the vicinity of such rivers or coasts could be drifted to Torbay. One or other of these conditions must almost certainly have existed in times past. Arthur Hunt commented, very sensibly, that the only reason that we find raised beaches at Hope's Nose and Portland, and nowhere in between these places, is because the softer intermediate coast-line has been gradually worn back, whilst the headlands have withstood the waves by reason of their hardness. Thus there must have been a time when the coast between Hope's Nose and Portland was much less embayed than it is at present. Somewhere on this ancient coast-line the waters of the Teign and the Exe flowed into the sea many miles to the south of their present exist. Now, 122 years beyond the date of publication of Hunt's paper there is no reason to disagree with his theory. He seems to have correctly set the scene for a broad embayment at the time of the interglacial raised beach. The next author, a much more famous one, seems to accepted this palaeogeography and expanded on the topic. The distinguished Professor Joseph Prestwich wrote more about this raised beach, including the molluscan fauna, in 1892. His paper is well-known and very easily accessible, being in the Quarterly Journal of the Geological Society. "The well-known Beach at Hope's Nose, originally described by Godwin-Austen, caps the headland, a short distance east of Torquay, where in consequence of of its being concreted by a cement of carbonate of lime, it forms a projecting cornice about 31 feet above high water mark. It is overlain by 3 feet of sand and then by a few feet of angular local rubble (Head), in which I found a tooth of a Horse. Many of the shells are entire but they are mixed with a large proportion of comminuted shells. They comprise: Patella vulgata,

Littorina littorea,

Littorina rudis,

Murex erinaceus,

Purpura lapillus,

Turritella terebra,

Cardium edule,

Cyprina islandica,

Mytilus edulis,

Ostrea edulis,

Pecten varius,

Burrows of Saxicava

Burrows of annelids

The palaeoclimatic conditions implied by the interglacial fauna do not indicate a drastic change from those at present, even though a whole glacial phase has separated the time of deposition from the present-day. A somewhat colder climate is implied by Trophon truncatus and by Pleurotoma turricula, judging from their present range ( (Orme, 1960). However Pinna rubis, Adeorbis subcarinatus and Fusus jeffreysianus which today occur from Aberdeen to the Mediterranean show that there was no intense cold.

HOPE'S NOSE Raised Beach - Sediments

The Hope's Nose raised beach has a basement bed 0.3 to 0.4 metres thick. This is composed of locally derived limestone and slate debris, varying from fairly fine gravel to boulders and angular blocks up to about half a metre long ( Orme, 1960). Above is cross-bedded coarse sand, becoming progressively finer upwards. The sand has a complex composition, including limestone clasts, slate, quartz sand grains, and also skeletal carbonate grains (shell debris). Orme (1960) also mentioned the presence of clasts of flint. The flint could have come from the Eocene gravels of the Haldon Hills and adjacent area, or from the Chalk which lies some distance offshore to the south, as shown on a map above. Another possibility, mentioned by Orme (1960), is that in Pleistocene times when the raised beach was formed there were other flint deposits in the area which have since been destroyed. Dolerite clasts have also been found in the raised beach deposits. Such grains are unlikely to survive long travel amd much weathering, but, of course, there is a dolerite intrusion nearby, at Black Head. This is the most likely source of the dolerite grains.

Lithologically similar, the Thatcher Rock raised beach contains more material derived from the sandstone assemblage around Torbay. Shannon (1927) suggested that from the assemblage of heavy minerals, the Thatcher Rock raised beach might be of later date than the Hope's Nose Raised Beach. The greater amount of epidote and sphene in the Thatcher Rock deposit could indicate a later stage in coastal erosion, when the Black Head dolerite or microgabbro was more exposed. Furthermore while kyanite is largely confined to Hope's Nose, the Thatcher Rock minerals are more like those of the modern beaches ( Orme, 1960). However, dolerite has been recognised in the Hope's Nose deposit.

The raised beach is calcite-cemented and quite well-lithified for the most part. Such cementation of raised beaches is fairly common in carbonate environments in Britain, as at the Gower Peninsula (on Carboniferous Limestone) (West, 1970). The calcareous waters may have come directly from the Devonian Limestone beneath, or from shell or limestone fragments within the raised beach deposits, or from calcareous Head or hillwash deposits.

HOPE'S NOSE: Tuffs of the Daddyhole Limestone Member

At Hope's Nose in the Daddyhole Limestone Member of the Torquay Limestone Formation, there are two bands of calcareous tuffs. These rocks consist of dark lapilli, converted into magnetite, in a recrystallised calcite matrix. There is some yellow decomposed glass resembling palagonite (Lloyd, 1933).

HOPE'S NOSE: Local Variscan Deformation near the Raised Beach

These structures are in Givetian limestone near the north end of the raised beach. They have figured in various publications, including:

Ussher (1903, Fig. 7, p. 52); - Shannon (1928, Plate 5, opp. p. 136); and - Lloyd (1933, Plate 7, opp. p. 121).

Shannon considered that the limestones above the thrust plane are Middle Devonian, Givetian, S2, and those beneath Givetian, S1. The interesting aspect is that two phases of tectonics are shown with folding taking place first and then the well-lithified limestones are thrust. A significant interval of time might have passed between the folding and thrusting to allow for resistant lithification of the limestone. However, this is not necessarily certain because limestone are capable of early cementation, especially in that tropical climate, with the Equator heading rapidly southward towards Torquay (it passed over Torquay in the Carboniferous and the place has become colder ever since).

HOPE'S NOSE: Local Variscan Deformation - More

The photographs above shows the effects of intense compression on goniatite-bearing, Devonian limestone at Hope's Nose. This is a point of detail in strata which are well-known to have been subjected to the Variscan (Hercynian) Orogeny in Carboniferous to Permian times.

The detail visible in the field is quite informative, even without any thin-section or laboratory data. It is interesting that there is evidence of both ductile and brittle deformation. Thus it is likely that we observe an early process here, covering the change from a relatively soft black limestone (like Blue Lias or softer) to a very hard, brittle black limestone (as it is now). The general early history of the strata here needs some brief explanation and this is given below. The processes observed in the photograph probably range from late Devonian to early Carboniferous.

During the early, depositional phase of the Middle Devonian here, about 380 million years ago, there was crustal extension in this area, leading to the development of grabens and half-grabens. The Torquay High was on the north, upthrow side of a major fault, which bounded the South Devon Basin (a half-graben) to the south. The Middle Devonian limestone of Torquay, like that at Hope's Nose owe their carbonate reef characteristics to the Torquay High (Leveridge et al., 2003). This was a relatively positive or high area of Devonian sea floor about 400 million years ago. Tropical shallow water favoured the precipitation of carbonates, and in particular, the coral-stromatoporoid reefs.

Remarkably, within only about 50 million years there was a drastic change and the early stages of the Hercynian or Variscan Orogeny commenced. There was major compressive deformation during the early Carboniferous (Dinantian). This produced northward verging folds, cleavage, thrust and also some northwest-trending, dextral strike-slip faulting (Leveridge et al., 2003).

Now the photograph above shows Devonian limestone, with goniatites, which had developed on or near the original structural high (the goniatite beds are vertically quite close to the coral-stromatoporoid beds in the area). It is obvious that there has been compressive brittle fracture, and it seems to have been preceded by earlier ductile compression. There can be little doubt that this is result of the Carboniferous (Dinantian) compressive deformation of round about 350 million years ago.

The photograph above shows a location only about 10 or 20 metres away from the goniatite area where the deformation has become more extreme. Here the black limestone is almost completely brecciated. The process has not taken place in a single phase because there is angular brecciated calcite of vein origin incorporated in the breccia. Small-scale conjugate shears and tension gashes show the brecciation is related to the goniatite deformation structures shown higher above.

HOPE'S NOSE: Hope's Nose - Hydrocarbon History - Speculative

As a follow-up from the simple field observations, above, combined with the general known geological history of the area, here is some speculative discussion of the hydrocarbon history. Reefs on highs associated with thick marine sediments are often sites of oil and gas accumulation, provided there was sufficient depth of burial (and there probably was here). The hydrocarbons would be expected to have migrated to the highs and become stored in the originally porous reefs. Now the Torquay reef facies is associated with black limestones which would be expected to have a high organic content (although I have no TOC figures). The unusual aspect for reefs is that the porosity seems to be almost negligible now (but note that the low quantity of pore-filling calcite suggests that it was never very high). Under the high stresses to which the rock has been subjected little porosity could survive. Thus the reefs do not seem to to have porosity or be reservoir rocks now. Yet, their burial and tectonic history suggests that they have been through the oil (and gas?) window at least once and probably twice. In other words oil and/or gas has probably been generated and has been lost in some way. It probably went in the Dinantian. It probably escaped to the surface but some could have been held if suitable Carboniferous reservoir rocks exist or existed in the area. There may be nothing suitable in the area now, but there is at least a remote possibility of a limited sandstone reservoir that has not lost its porosity, or even, perhaps, some indirect transfer of gas into Permian sandstones.

Because there has been a thick Permo-Trias sequence (shown by palaeotemperature data - see discussion of gold veins) the Devonian limestones have probably entered a second phase of deep burial. This was after the Variscan Orogeny. Because of the earlier deformation, though it probably had little effect. See the limestone clasts in the Ness breccias of Permian age (at Shaldon near Teignmouth) to gain some idea of the state of the limestone in Permian times.

HOPE'S NOSE: The End of the Promontory (NE)

HOPE'S NOSE The Old Limestone Quarry

At the northern end of the Hope's Nose promontory is an old quarry. On the south side of the headland there is an apparently normal sequence of Eifelian limestone over shales. These limestones at most places largely consist of crinoidal debris (Lloyd, 1933). The exposure at the quarry on the northern side has been a subject of more discussion in the past. The highest beds, consisting of thin-bedded limestone, seemed to be of Eifelian type and they overlying more massively bedded limestone of Givetian type. Ussher (1903) thus, considered that the sucession was inverted. Shannon (1928) believed that the upper, thin-bedded shaly limestones had been thrust over the lower beds, quite possible in view of the thrusting of Devonian limestone that has occurred in the region. Lloyd (1933) pointed out that the irregular junction when viewed closely seemed to be an unconformity. There are small hollows or pockets in the underlying dark, bedded limestone containing unsorted sandy and shaly material. He therefore considered the seqence right-way up but did not rule out the possibility of inversion.

Note that has been a divergence of opinion regarding the identity and age of the limestone of the Hope's Nose Peninsula. This requires brief explanation. The 2004 edition of the 1:50,000 Geology Series, Map, Sheet 350 of the British Geological Survey interprets all the limestone of this promontory as of the Daddyhole Member of the Torquay Limestone Formation, and regards it as Eifelian. The Daddyhole Member is relatively thin-bedded, and contrasts with the Walls Hill Member of the Torquay Limestone Formation which is massively bedded (and seen in the upper part of Walls Hill). The Walls Hill Member is Givetian.

HOPE'S NOSE: The Ore Stone

The Ore Stone is a small rock or island that can be viewed from Hope's Nose, eastern side, or more closely from a boat. It consist of Devonian limestone which has been conspicuously thrust from the south. It shows an interesting Variscan structure, a mesoscopic asymmetrical anticline, broken by a reverse fault. A close view shows that there is some well-developed axial plane cleavage. Much larger Variscan fold and fault structures occur in the Devonian limestones of the Torquay area. Note that at Triangle Point the Devonian limestone is inverted within part of a larger fold structure.



BLACK HEAD: Black Head Dolerite Intrusion

(north of Hope's Nose)

This is the Black Head microgabbro or dolerite (diabase in very old literature). It is an albite-dolerite carrying small amounts of olivine and with characteristic albite-segregation veins (Shannon, 1924) . It is intruded into the Upper Devonian Saltern Cove Formation Leveridge et al. (2003a) and was dated as post-Culm and pre-Permian by Shannon (1924).

More detail on the Black Head main intrusion has been given by Shannon (1924). It is a rather fine-grained dolerite, partly ophitic in fabric [ophitic implies laths of plagioclase within a pyroxene, i.e. augite]. In the field it weathers to a dark greyish-brown surface, but is dark green when chipped with a hammer. The albite segregation veins, mentioned above, cannot be seen in the field. There are wide areas or veins of red dolerite. The colour results from the alteration of the augite to limonite (goethite). The feldspars are not altered in these red areas, apart from albitization and choritization which affects the whole intrusion. The feldspar in the Black Head dolerite (or microgabbro) is andesine with a tendency to oligoclase. Albite is in the segregations (see Shannon (1924), p. 198, for details of these).

Leveridge et al. (2003a) succinctly explained the setting of intrusive igneous rocks of the area:

"The extrusive and intrusive basic igneous rocks of the district compare with those elsewhere in the passive margin sequences of south Devon and central Cornwall Leveridge et al. (2003b). They are predominantly within-plate alkaline basalts, with subordinate sub-alkaline basalt with geochemistry indicative of a mantle source. The magma is an Ocean Island Basalt type, which in a continental plate setting implies strong extension Merriman et al., 2000."

KENTS CAVERN

The cave system is now thought to have been initiated about 2 million years ago, according to Leveridge et al. (2003a; 2003b). It is a complex of caverns, rifts along faults and phreatic tubes, multiphase roof breakdown and stalagmite formation and flowstone floors. The Basal Breccia is of special importance with animal remains dating back to more than 340 thousand years (Proctor et al., 2005). It contains remains of the cave bear Ursus deningeri, the lion Felix leo and the voles Arvicola cantiana and Microtus oeconomus indicating a late Cromerian age for the deposit. Neanderthals and Homo sapiens occupied the caves in the Ipswichian Interglacial and the early Devensian Stages (Leveridge et al., 2003a, 2003b).

There is useful online information on Kents Cavern at: English Riviera Geopark - Early Man.

ANSTEY'S COVE, TORQUAY

Anstey's Cove car park, Torquay, is reached by a minor road, an inconspicuous one-way street from Babbacombe. It joins a larger road system again, a short distance south of Kent's Cavern. It is only short walk across a recreation ground, if one decides to walk from the Kent's Cavern area. At least in the off-season, car parking above Anstey's Cove is easy. The adjacent Redgate Beach is officially closed off, because of risk of rock fall. The walk down to Anstey's Cove is easy.

Anstey's Cove is a very small embayment, with a short promenade extending northward (Devil's Point). It is easily reached by a path and steps from a car park on the cliff top. The cove is close to the junction between dolerite or micrograbbo to the south (of the Black Head intrusion) and very faulted and fractured Devonian limestone to the north. It gives, from Devil's Point, a good view of Redgate Beach and the major promontory of Long Quarry Point. Access to Redgate Beach is closed at present because of risk of falling rocks. The small beach at Anstey's Cove consists of pebbles and cobbles of Devonian limestone with a smaller proportion of much darker and very rounded dolerite clasts.

REDGATE BEACH (near Babbacombe, and north of Anstey's Cove)

Redgate Beach, Torquay is small embayment north of Anstey's Cove and near Babbacombe. It consists mainly of Devonian Limestone and is crossed by the Ilsham Fault. Above Redgate Beach there are crevasses in the cliff top. Some large blocks tilt seaward. At the base of the cliff there is a short promenade and there are some very large rectangular blocks of limestone which have fallen from the cliff.

The following description of Redgate Beach has been given by Lloyd (1933).

"Couvinian [Eifelian] limestones form the lower part of the cliff on the north side of the beach; their relation to the massive Givetian limestone forming the plateau above is shown [in his Figures 10 and 11 and in a sketch shown here].

The lowest beds are very dark grey shaly limestone in thin irregular beds. Several feet of pale coralline limestone, apparently massive, really somewhat shaly, intervene between these and the higher grey and red (stained) shaly limestones, and there are no means of determining whether the shaly limestones are folded round the massive bed or in normal intercalation with it. From a distance this series of beds appears to dip into the cliff under the Wallis Hill limestone, and only a close examination at the exposure itself reveals the fact that they are cut out by a fault parallel to the cliff face.

The lower dark grey limestones have yielded Atrypa reticularis (Linnaeus), 'Cyathophyllum' cf. roemeri Edwards and Haime and Pachypora ? cervicornis (Blainville).

At the top of the winding cliff path leading to Walls Hill, west of the above exposure, thin-bedded red shaly limestone is exposed in the narrow gap separating two clearly defined faults which traverse the massive limestone. The red shaly limestones are in apparent normal succession with the Couvinian [Eifelian] shales below, already described, although the actual junction in obscured by scree; they are described as Upper Devonian by R.G. Shannon [1928]. [See also the website:

TFF Forum Photo Gallery: The Downs and Redgate Beach, 2012. A brief comment from this follows: "Moving on around to the right of Walls Hill you look down on Redgate Beach, it was closed around 1998 I believe (that is what it says on the sign) due to rock falls and sadly it has now been left for nature to take its coarse. There once was a footbridge from this beach that went around the cliff to Anstey's Cove, but than was taken down as it was claimed it was dangerous, but I feel it was removed to stop people getting onto Redgate beach. The locals defy orders not to use the beach and even today there was couple down on the beach and during the summer you will find plenty on the beach as it is one not known to our visitors."] LONG QUARRY POINT Grey and pink Middle Devonian limestone is exposed at Long Quarry and adjacent cliffs, where it dips steeply in a northward direction. The quarry was used during Victorian times, to provide stone for the grandest houses and civic buildings in Torquay. The Victorians not only started the spread of large buildings over beautiful open hills above the sea, but also removed parts of the cliffs. Nowadays the old quarries of Torquay seem relatively natural and seem to have less impact than the housing development. The limestone at Long Quarry is full of white stromatoporoid masses (Actinostroma),some reaching 0.6m. in diameter (Lloyd, 1933). The following fossils have been identified by Jukes-Browne (in (Lloyd, 1933)) from Long Quarry (listed here in old terminology which has not been updated). 'Cyathophyllum' sp.

Actinostroma clathratum Nicholson

A. stellulatum Nicholson

Stomatopora? concentrica Goldfuss

Alveolites? suborbicularis Lamarck

Pachypora cristata (Blumenbach)

Metriophyllum?

Favosites fibrosus (Goldfuss) (coral)

Stachyodes verticillata (M'Coy) The quarry includes the type section of the Middle Devonian, Walls Hill Limestone Member of the Torquay Limestone Formation (Givetian according to the BGS map, Sheet 350). See also: Page, K.N. A Review of the Geological Heritage of Torbay. 71p (for full reference go to: Page (200?)). Apart from geology and from conservation, another use of Long Quarry is rock climbing. See UK Climbing - Long Quarry Point. There are also videos online of yet another activity here: "Clips of us guys jumpin at long quarry". BABBACOMBE The Plateau of Babbacombe As shown in the diagram above, there is a plateau in the Babbacombe and adjacent areas that is round about 100 metres above sea-level. More specifically, the northern part of this plateau is 330 feet or 100 metres above sea-level but it slopes gradually southward, as discussed by Jukes-Browne (1907). He allowed the possibility of a Cretaceous date but favoured an Eocene age for the planation. A connection with the basal plane of the Eocene in the nearby Haldon Hills was suggested. He thought that there might be a north-west Tertiary flexure on the line of the Bovey Syncline. The possibility of a Pliocene age for the plateau has been considered and rejected by Shannon (1927) following a study of associated heavy mineral residues. See Lloyd (1933), p. 115 et seq. ("The Limestone Plateau") for further discussion of this topic. Babbacombe - Oddicombe Beach Introduction BABBACOMBE: Oddicombe Beach - Introduction At the northern part of Babbacombe (St Marychurch), within a larger embayment is Oddicombe Beach. This is the main and largest beach here. It should not be confused with the smaller Babbacombe Beach to the southeast of this and separated by Half Tide Rock (igneous exposure). From the cliff top there is steeply sloping road down which you can walk to Oddicombe North Beach. Alternatively you can use the interesting Babbacombe Cliff Railway, constructed in 1926. This almost exactly marks the position of a major fault between Devonian strata, limestone and shales, to the south and the conspicuous red Permian strata to the north. LOCATION - ODDICOMBE BEACH: Oddicombe North Beach:

Oddicombe Breccia, Permian

(Red, desert alluvial fan deposit) The partial rounding of the limestone clasts in the Permian Oddicombe Breccia is interesting. This might be the result of exfoliation rather than of dissolution in the arid Permian environment. There seem to be some curved white flakes of limestone in the general matrix, and these might be the result of exfoliation. Notice the numerous small flakes of slate which have been intensely reddened. These are so abundant that the rock is technically clast-supported, even though, at first sight, it seems matrix-supported. Red breccia or conglomerate (breccio-conglomerate of Ussher (1903) is conspicuous in the large amount of fallen debris and on the shore at the northern end of Oddicombe North Beach, Babbacombe. LOCATION - BABBACOMBE: Oddicombe North Beach - the Oddicombe Breccia Member

- The Ancient Permian Desert The Permian breccias of Torquay can be compared to modern regs and alluvial fans, as in Libya, Qatar and other Middle Eastern countries, but they are not identical in detail. However, they provide a good impression of the ancient environment. In the reconstruction above, it is assumed that the surface was initially brown and the sediments became redder after burial (comparison with modern California) but there is some uncertainty about this. LOCATION - ODDICOMBE BEACH - 2010 and onwards Oddicombe Beach - Cliff Fall of 2010 (with major collapse on the 3rd April 2013) (Warning: the beach in the area of the cliff fall is not safe at all; further major rock falls have occurred and any sites of potential rock fall should be avoided) The Permian Oddicombe Breccia, or at least collovium and loess associated with it, is notorious for subsidence problems. See Catell (2000). The likelyhood of problems on the Oddicombe Breccia is about twenty times the likelyhood on other rock types. Collovium or loess associated with the Oddicombe Breccia is particularly prone to loss of strenth on wetting. [See also the Daily Mail newspaper report of 2010: "No wonder they got it cheap: Clifftop home loses its garden just six days after new owner paid bargain price of �150,000"] This cliff fall of the red, Permian, Oddicombe Breccia took place in February 2010. It apparently occurred only six days after someone purchased the house and garden on the cliff top from which this fell. See: Dail Mail Reporter (2010) for more details. The property is Ridgemont House which lost a substantial piece of its land and is now situated only 50ft or 15 metres from the edge of the 300ft or 91 metre cliff. At night, a large boulder the size of a van first fell off and then the main mass fell. A Torbay Council spokesman said that the 5,000-tonne rock fall was from the unstable sandstone cliffs to the rear of north beach, Oddicombe. The strata involved is the Oddicombe Breccia of Permian age. See the current British Geological Survey Map, 1:50,000 for Torquay. A similar loss of part of a cliff top garden on Permian strata has taken place at Dawlish . Although some steep red sandstone and breccia cliffs seem to survive for a fairly long time, in some cases hundreds of years, now and again they fall, of course. As shown above, there was further movement in the upper part of the cliff in early 2013. There had already been concern in December 2012 about new landsliding at Babbacombe (above Oddicombe North Beach). There was a press report in the Herald Express of Saturday December 15th 2012. A short extract is given below. See the full article. "New council fears of landslide above Babbacombe beach." A geologist has warned a 'major fall is imminent' on the cliffs at Oddicombe. The area was hit by a landslide last week following weeks of rain. A spokesman for Torbay Council has revealed: "Following recent rockfalls in other coastal areas the council has appointed an engineering geologist to carry out a survey of several locations around Torbay's coastline. The location giving him most concern is the high cliffs behind the closed section of Oddicombe Beach, Torquay, and it is his opinion a major rock fall is imminent in this area. As a result we would once again strongly urge members of the public to adhere to the Beach Closed warning signs which are in place for their safety. The Herald Express coverage of a major fall in 2010 hit international headlines after it emerged the house at the top of Oddicombe Cliffs had been bought shortly before a major fall. In February 2010, 5,000 tonnes of boulders crashed down on to Oddicombe Beach just below nearby Ridgemont House. The week before the property had been sold at auction for �155,000." ODDICOMBE BEACH - MAJOR ROCK FALL - APRIL 2013 (1) Introduction

(high resolution photographs after the event - by Nikolett Csorvasi) Ridgemont House seems to be marked on the old maps 1899-1902. The adjacent buildings in the approach road do not seem to have been built at that date. . A very similar rock fall to that at Oddicombe Beach took place at Dungy Head St. Oswald's Bay, Dorset on the night of the 29-30th April 2013, in other words, within a month of the Oddicombe rock fall. However, the St. Oswald's Bay rock fall was in Chalk and therefore relatively white, in comparison to the red rock fall at Oddicombe Beach. The Dorset fall was from a cliff of similar height (about 120m).

ODDICOMBE BEACH - MAJOR ROCK FALL - APRIL 2013 (2) The Destructive Run-Out Lobe (sturzstrom-like?)

A feature of the April 2013 rockfall at Oddicombe Beach was a long run-out, or horizontal stretch of debris in a seaward direction. This was not very large but sufficiently powerful to destroy a prominant small red stack adjacent to Gentlemens Bathing Place at the northern end of the beach. Normally rock falls result in debris cones at about 38 degrees slope, and this is the case for the main rock fall at Oddicombe Beach. However, as in the case of some Chalk Cliffs of southern England ( Williams et al. (2004) there is also a "run-out". This is a nearly horizontal, subaerial debris flow. These can occur where there is high cliff, a large volume of rock fall, and the attainment of a high velocity at beach level. This was probably not large enough to have been a true sturzstrom but it may have had some similarities to such an occurrence, at least within a limited area. Certainly a substantial, horizontal, run-out seems to have occurred and to have completely destroyed the red stack. A run-out into the sea is probably the reason for the extensive red-colouring of the seawater shortly after the event.

It is obvious that this rock fall was a very dangerous one and had anyone been on the beach in front at the time the consequences would have been fatal. At Burton Bradstock in West Dorset a sandstone cliff fell with a low-angle debris cone in 2012. It was not a long run-out but it killed a person on the beach and partially entrapped others. The Oddicombe rock fall was much larger and much more powerful and with a longer run-out. The Oddicombe Breccia is actually in large part a sandstone with clasts, and thus has some similarity to the material of the Bridport Sands of the Burton Bradstock cliffs. As in the case of the sandstone at Burton Bradstock, the Oddicombe Breccia has some large open joints, from which rock falls could take place.

ODDICOMBE BEACH - MAJOR ROCK FALL - APRIL 2013 (3) More Details (and comparison with older rock falls)

There follows an extract of a report from the Western Morning News of the 20th February 2013:

Ridgemont House, at the top of Oddicombe Cliffs in Torquay, is now very close to the cliff edge and is expected to collapse at any moment. Council officials have warned the public to steer clear of the dangerous site and beach at Little Oddicombe, which has been closed for years. A spokesman for Torbay council said the house was "in a dangerous condition". "Parts of the boundary wall are now very close to the cliff edge at Little Oddicombe," the spokesman said. �As further rock falls occur, we anticipate that the building will suffer further collapse." The now practically worthless property hit headlines in 2010 when a landslide hit it just a week after it was sold at auction to retired police officer Sue Diamond for �155,000. Legal disputes are still thought to be ongoing and the house is fenced off. Miss Diamond who is disabled, made a telephone bid of �154,500 for the house in February 2010, without viewing it or having a survey done. But just eight days after the auction, a landslide left the 1930s house just 50 yards from a drop into the sea, and signalled the started of a lengthy legal battle. At the time Miss Diamond said the house was uninhabitable and worth only �3,500. Now it is on the verge of total obliteration after the most recent landslide caused a large portion of it to collapse. Since the sale Miss Diamond has been engaged in a legal war. Explaining her decision to buy the house in Torquay at the time, she said her Chiswick home in London had been flooded by burst pipes and she thought the ground floor of the seaside property would be ideal for a disabled person. The large six-bedroom property was sold for the bargain price because of its precarious position. But just days later neighbours heard a "rumbling" noise before the unstable sandstone cliffs crumbled, sending more than 5,000 tonnes of rock at the bottom of the garden down to the beach below. Minor landslips over the Christmas period weakened the structure further but a bigger slide on Sunday left it in a precarious position. A eological survey has been undertaken, indicating that fresh landslides were imminent. The council said the threat of further landslides remains high. "We once again reiterate for members of the public to heed the various warning signs for their own safety," the spokesman added. On the 3rd March 2013 a rock fall took place, dropping the sandstone cliff into a debris slope of boulders and sand and destroying the house. In particular go to: Why you should never buy a house in a blind auction: Sea of red as landslide claims more of Torquay cliff face, taking with it �154,000 home. By John Stevens and Richard Hartley-Parkinson. Sue Diamond bought Ridgemont House in a telephone auction without carrying out structural survey Three years later and the house has finally fallen into the sea after the land disappeared from under it. Devon Cliff fall is the latest around the coastline after strong winds, high tides and months of heavy rain Mail Online, 3rd April 2013. This article has superb colour photographs by Apex. It also has some very good videos. The Permian sandstone can be seen to dip seaward. It also seems, that as would be expected, there have been older landslides of similar type in the area. The houses seem to have been built on undisturbed ground. In some cases, and this is worst, there are fairly close to old backscarps of former landslides of this type. Nothing unusual has happened here. It is unfortunate that houses, particularly this one, have been constructed close to former landslides backscarps. The very ridge from which presumably the house takes its name is a relic previously left from older landslides where were adjacent. This does not at all necessarily mean than any other properties are at risk. They are all in different positions and different distances from the present active area. Some may be very well clear of any hazard. In any case the present phase of worst landslide activity may well be finished now. There has been unusually wet weather and now the cliffs are drying out. Some sort of stability may return. Of course, on a geological time scale landslides will happen again, after there has been renewed cliff erosion at foot of the cliff and the normal landward retreat. However, that is a very long term matter. After a while interest in the topic here will fade away. This was not a unique event but something normal but occasional on the red Devon Permo-Triassic cliffs. More landslides will take place on these sooner later at other localities. One has occurred in 2007 near Dawlish, another locality with some high red cliffs. [Morris, S. 2007. Millionaire left with even better sea view after cliff landslide. The Guardian Newspaper, Tuesday, 6th February 2007. By Steven Morris. [Short article with a photograph].

A luxurious clifftop home being built for a wealthy businessman now boasts an even better view after a large chunk of land crumbled into the sea. The landslide, in which 25m (82ft) of land and several large pine trees vanished, left the house, which has:a glass spiral staircase and indoor pool, perched close to the clifftop. The landslide was witnessed by carpenter Daniel Julyan and his father, Philip, as they put the finishing touches to the house in Dawlish, south Devon. Daniel, 19, said: "Quite often we'll hear a rumbling when a train goes by on the local railway line. But this just kept going and got four or five times louder. It was like thunder. We looked over the edge and there was a mile of red dirt and branches and stuff floating in the ocean. I suppose the only good thing is it's opened up an even better view." ......Though the landslide brings both Mr Skilton's home and the new house closer to the clifftop he insisted he was not concerned: "I am not a bit worried about my home." Michael Hogg, owner of Character Homes, said: "There is just a sheer drop there now. I went to see it and I am trying to find reasons why this happened. "We really have no reason to be concerned. We have just lost a few trees and snowdrops. But it has put the new house very close to the cliff face indeed."]

NORTHERN ODDICOMBE BEACH - MAJOR ROCK FALL - APRIL 2013 (Some details are in a BBC webpage, April 2013)

For a summary of the events of the major rock fall at northern Oddicombe Beach go to the BBC Devon webpage at: Further Rock Falls at Oddicombe 'Expected' "Cliff faces at a Torbay beach are still unstable and more rock falls are expected, a council says. Thousands of tonnes of earth and stone fell at Oddicombe last week, resulting in a section of beach being closed off. Torbay Council said visitors should observe marked exclusion zones put up after the last landslip. But it added a geologist had advised that existing zones were sufficient and there was no risk to beach huts and a beach cafe, which were still open. The area is famous for its red earth and sandstone. Nearby seawater was turned red as a result of the recent landslip. The entire beach was closed for several days in 2010 after a landslide which brought down about 5,000 tonnes of sandstone. Oddicombe is a "Blue Flag" beach and it has also received a Quality Coast award." See also: Landslip at Oddicombe Beach turns Sea Red This includes a good video, of which the following is an example part: BBC News Devon, Article online, 4th April 2013. "Landslip at Oddicombe beach turns sea red 'Red Sea' in Torquay after cliff collapse.

A landslip at a beach in south Devon has turned the sea in the area red and caused an already partially collapsed empty house to be further damaged. Thousands of tonnes of earth and stone were estimated to have fallen at Oddicombe beach on Tuesday night, Torbay Council said. A section of the beach has been closed as a result. The collapse follows a seawall between Torquay and Paignton being breached earlier in the week.

The area is famous for its red earth and sandstone. The collapsed house, in one of the most expensive areas of Torquay, has been uninhabitable for some time. It used to have a large cliff-facing garden, which has eroded away over several years, and part of the house itself went down a neighbouring cliff in December.

Staff at Oddicombe's beach cafe said the business was to remain open. ........ Last December, Torbay Council said a major landslip was "imminent" at Oddicombe, after it got the results of a geological survey. The entire beach was closed for several days in 2010 after a landslide which brought down about 5,000 tonnes of sandstone..." Note that a comment is made by a local person during the video that an offshore rock has been destroyed by this rock fall. Was this the prominant stack at Gentlemens Bathing Place?

NORTHERN ODDICOMBE BEACH - ROCK FALL - APRIL 2013 Video of the Oddicombe Rock Fall in 2013

An interesting video of the Oddicombe Rock Fall has been made by Kim Aldis. Go to his website for this and more Torquay matters at:

Kim Aldis - The Weekly Picture

Kim Aldis is a photographer based in the Torbay area of England's S. Devon. Retired from a highly successful career in CGI, animation and VFX for TV and film, he now spends his time photographing the people, landscapes and the seascapes of Devon, Torquay and the Torbay coastline.

VIDEO OF ODDICOMBE ROCK FALL BY KIM ALDIS ON YOUTUBE Note, particularly that this seems to show some forward, seaward bulk movement before the final rock fall. If this is the case, it might suggest that this is not a simple rock fall but that it might also have a slip-plane or shear plane of the usual curved landslide type. Such a slip-plane would explain the initial subsidence of the garden area of Ridgemont House. .

BABBACOMBE: PETIT TOR

(Devonian limestone headland north of North Oddicombe Beach, Babbacombe, Torquay, and south of Petit Tor Cove)

The Torquay Limestone Formation of Petit Tor is easily accessible at the Gentlemen's Bathing Place, northern end of Oddicombe North Beach.

The Torquay Limestone Formation of the Gentlemen's Bathing Place is very fissured. Shown above are cross-fissures which seem to have formerly been open joints. These have since received a partial filling of red sediment, followed by closure by white calcite. The red filling is broadly geopetal and an initial view suggests that the dip has not changed greatly since the introduction of this red material. The photograph above shows this, but in an east-west direction, without indication the orientation in a north-south direction.

In hot, dry desert environments, carbonate bedrock is often shattered by severe daily temperature changes and by very rare water erosion. Exposed dolomite bedrock, shown above in a desert environment at Wadi Faras, at the margin of the Hun Graben, Libya is openly fractured. This is probably quite a good model for the harsh Permian desert environment. In that case the Devonian Torquay Limestone was the bedrock and the northern part of Oddicome Bay, was a location adjacent to desert bedrock slopes similar to those shown here.

Shown above is Petit Tor Quarry at the end of the small peninsula. Here the the limestone was quarried for ornamental "marble". Large number of the straight nautiloid Orthoceras were once found in this quarry. However the marble vendors of the past removed rock containing these because it was very ornamental when polished. Ussher (1903) suggested that it was no longer worth-while to search for these.

BABBACOMBE Petit Tor Beach

I am very grateful to Philip Wills who kindly provided the above images. The last of these shows a pointed pillar in about 1840. He has photographed this pillar on the beach and this can be seen in a photograph above. Forty years ago he visited this beach by rowing from Watcombe. He discovered an hexagonal column on the beach which he assumed came from one of the buildings that once existed here.

SHAG CLIFF (North of Petit Tor Beach)

LOCATION - BABBACOMBE: Babbacombe Beach

(South of Oddicombe Beach, in the same bay)

Babbacombe Cliffs back a broad a scenic bay. The northern part is Oddicombe Beach (not Babbacombe Beach), discussed above and accessed by the Babbacombe Cliff Railway. Babbacombe Beach is much smaller and to the southeast of this and southeast of Half Tide Rock. It can be accessed on foot or by car by Beach Road, Babbacombe.

LOCATION - Babbacombe Red Rock at the Pier - Igneous Intrusion

Withy Point, at the southeastern end of Babbacombe Beach has good exposures of Devonian limestone. Walls Hill above the promontory is composed of the Walls Hill Limestone Member, part of the Torquay Limestone Formation (Devonian). A notable feature is the Red Rocks, which is an igneous intrusion into Devonian strata. This has been described by Shannon (1924). It is a dolerite or microgabbro, and is marked as such on the BGS geological map of Torquay (Sheet 350, Solid and Drift). The dolerite has a basalt selvage [margin] with lateritic alteration. Shannon's detailed description of the intrusion of the Red Rocks of Babbacombe are reproduced below:

"3. The Red Rocks, Babbacombe. The dark green rock below tide level attracts attention from its being rather like a picrite. The upper red rock is very fine grained but no junction can be traced. The dark green rock contains a large amount of augite, some subophitic but mostly euhedral, with some small grains of olivine. The latter is present in small quantity only and the appearance in hand specimen is deceptive. The original felspar is oligoclase with a tendency to andesine but most is chloritized albite; a certain amount of fresh twinned albite also occurs. Chlorite and calcite are decomposition products. Immediately above this the rock is much calcitized with chlorite and a few olivine pseudomorphs. Apatite in all the sections is large and rather abundant. The iron ore is ilmenite. Immediately below the red rock the dolerite becomes finer grained but is much calcitized, the felspars being oligoclase-andesine and albite. Rounded calcite grains in augite plates are considered to be olivine pseudomorphs. The red rock is entirely unlike the rest, consisting of some very small felspar laths in a nearly opaque ground of iron oxides and limonite. It forms the selvage to the intrusion and is entirely comparable to similar selvages described from Anglesey by E. Greenly (9). An isolated section would most probably be diagnosed as a basalt selvage, with lateritic alteration. These rocks are correlated with the Black Head dolerite on the evidence of olivine, albitization, fresh albite and some quartz haematite veins cutting it, but like the Ilsham Manor rock, it is more basic. It is possible that mineral stratification has occurred in the production of the darker rock at the base, but this is uncertain since the large development of calcite in the lighter rock may explain the differences noted in the field."

LOCATION - Babbacombe Half Tide Rock - Igneous Sill

Half Tide Rock between Babbacombe and Oddicombe beaches is an exposure of an irregular intrusion of soda-porphyrite. According to Lloyd (1933) pillow structure is developed. There are numerous inclusions of slate, and thin veins of igneous rock penetrate the slate but contact alteration is confined to slight hardening ( Lloyd, 1933). Note that an augite-lamprophyre sill occurs in Devonian limestone high in the cliff.

Merriman et al. (2000) have investigated geochemically the origin of the Devonian igneous rocks of Torquay and neighbouring regions. They concluded that the altered mafic volcanic rocks have filled in passive margin basins of SW England, and are not related to subduction. They were generated by Devonian (and Dinantian) intracontinental rifting.

Corbyn's Head Torquay ("Corbons Head") Aerial Photographs





Corbyn's Head ("Corbons Head"), Torquay Location and General Views (including Tor Sands)



Corbyn's Head (map ref. SX 908632) is at Torbay, south of the main part of the town of Torquay, not far from Torquay Railway Station (it is shown as "Corbons Head" on old geological and topographic maps and in Plate 6 of the the old memoir - Lloyd, 1933). It is the southern end of the Torquay Esplanade and sea wall. The headland is a small, flat-topped, promontory near the coast road; it has a cliff of medium height which is and accessible at low tide. Occasional rock falls have been recorded here (SCOPAC - Hope's Nose, Torquay to Holcombe).

Corbyn's Head Old Photographs

The photograph above has been modified after Lloyd (1933).

Corbyn's Head Cliff and Ledge Exposures of the Corbyn's Head Member (Permian, Torbay Breccia Formation)



The cliff is of multi-coloured breccia and sandstone, nearly horizontal and just with a very low dip. It is regarded as of Permian age, although a late Carboniferous age has also been considered. For an introduction to Permian geology in this region see the classic work of (Durrance and Laming, 1982).

The cliff section at Corbyn's Head is about 15m thick. The lower part consist of sandstone and the upper part of conglomerate ( Leveridge et al. 2003). The sandstone varies from purplish and reddish brown to buff, pale grey and greenish grey, as can be seen in photographs above. Particle size is medium to coarse. Individual sandstone beds are locally pebbly and show remarkably poor sorting. Pebbles and cobbles form thin breccia or conglomerate beds in places. Clast include sandstone, vein quartz, limestone chert and porphyritic rhyolite [or quartz porphyry] ( Leveridge et al. 2003). As shown in the photographs above there are some desiccation-cracked sheets of red mudstone. Some mudstone layers seem to have been eroded and reworked. Some red clasts are present in dipping foresets of sandstone. Red mud in modern deserts is sometimes referred to as being as hard as adobe, and this may have been true for these rip-up clasts. The thin mud-sheets do not seem thick or extensive and may have been very local rather than deposits of a major lake. Perhaps the mud settled from the final stages of flash floods in local depressions.

The oxidation state here at Corbyn's Head is interesting. It is peculiar that in some cases there are green (i.e. reduced) surrounding halos. Why should there have been reduction around clasts of oxidised material? Although unusual, it is, of course, possible that the Fe oxidation within the mud was actually late. The red colour, rather than brown colour, is probably the result of dehydration of Fe-minerals with burial, temperature and time. Hematite, here is probably post-depositional and the result of early burial diagenesis, as shown occurring in Quaternary times in the Sonoran Desert of Baja California, Mexico (Walker, 1967). Brown goethite-rich sediments can change to a red hematite-rich condition, with burial, a fairly high temperature and with time.

At Corbyn's Head the Corbyn's Head Member, the basal part of the Torbay Breccia Formation, has some other interesting features. This is an area where limestone clasts are often coated with the orbicular coating of chalcedony known as beekite, discussed in more detail elsewhere in this webpage. With regard to beekite see Ussher (1903, p. 110)

Imbrication directions shown by clasts here and at Livermead Head show transport from a westerly direction between a quartzite ridge and a limestone ridge, present at the time. An interesting feature of the cliff section is the presence of some dish structures.

[See also:

Elaine Burt, Richard Scrivener and Sarita McVicar Wright. 2012. Volcaniclastic red beds from the Corbyn's Head Member, Torquay, South Devon. Talk at the Meeting of the Ussher Society, Wednesday 4th January 2012. Probably a paper will be available later.]

Corbyn's Head, Torquay Desiccated Mudstone - Comparison with Similar at Holcombe Head, near Dawlish



Similar mud layers, but less well-developed are present in the Teignmouth to Dawlish, Devon. Permian Teignouth Breccia at Hole Head, Holcombe, near Dawlish, Devon. This is near the locality named after the adjacent Smuggler's Lane, but the exposure is on seaward rocks and only accessible by boat. See Brookfield (2000) for discussion of similar mud layers in Permian breccias of Scotland as a result of the temporary development of small ponds on pediment breccia and sand deposits. Such an origin in a small and temporary ponds is very likely for the thin mud deposits in the Permian breccias and sands both at Torquay and at Hole Head.

Corbyn's Head, Torquay Ledge Exposures of Desiccated Mudstone



Corbyn's Head Red Mudstone Fractured and Distorted



In vertical section near the foot of the cliff at Corbyn's Head, red mudstone can be seen to be distorted and to occur as concave-upward, irregular fragments. These blocks have probably separated by desiccation cracking. Is the displacement the result of slumping or of water injection?

Corbyn's Head Early Oxidation of Red Mudstone to Green Mudstone



.

LOCATION: Paignton - Roundham Head, Paignton [SX 896598] Tor Bay Breccia (with some sandstone beds)



Roundham Head, Paignton is briefly described briefly by Laming and Roche (20?? undated). "The easily-accessible south side of the headland shows Tor Bay Breccia of early Permian age, consisting of fragments of limestone, quartzite and some igneous rocks in a sandy matrix, with a layer of wind-blown sand seen best at the eastern end (difficult access) which indicates a northeasterly wind."

At this locality the dip is low and there some local displacement by faulting. Cross bedded sandstone beds occur in the breccia sequence. See: Ussher (1903, p. 110), who included a diagram (his Fig. 16).

In the nearby railway cutting above Roundham Head red sand with buff and grey patches and a clayey band rests on conglomerate with numerous limestone fragments. These clasts contain many examples of the beekite according to Ussher (1903, p. 110). This is a type of chalcedony, reported in old papers on this area. It occurs in the the form of concentric rings, on carbonate material such as fossils or limestone. It was in south Devon that the so-called "orbicular silica" received the name "beekite", after Dr Henry Beek, Dean of Bristol, who first drew attention to the deposits. Later optical has shown that they are aggregates of various fibrous forms of silica with differing optical characters. Separate minerals that may be present include calcedonite, pseudocalcedonite, quartzine, lutecite (the oblique-extinguishing chalcedony associated with evaporites) and lussatite. For some more old information regarding beekite in South Devon see: Hughes (1889).

Ussher (1903, p. 110) further mentioned that a quarry which once existed near Paignton Quay, near Roundham Head, showed purplish grey-mottled loam on thin even-bedded red, grey-mottled sandstones on a breccia or "breccio-conglomerate". He noted that on the south side of Roundham Head there is an occurrence of sandstone in the breccia and "breccio-conglomerate". Sandstone of this type is shown in photographs above taken from the sea. It is shown in the photographs above the breccia beds.

LOCATION: Berry Head, Brixham



(Photography by Nikolett Csorvasi)

ACKNOWLEDGEMENTS

The Head of the School of Ocean and Earth Science, Southampton University, and the staff of the School are particularly thanked for continuing to run this website on the Southampton University system. Although the website is written privately in Romsey and regularly uploaded from there, the computer organisation of Southampton University, iSolutions, have been very helpful in keeping the system running smoothly online from their server.

I am particularly grateful to the Staff of the Centre for Environmental Science, School of Civil Engineering and the Environment at Southampton University, for help and advice and information on many field trips to the Torquay area. I particularly thank Dr. Malmcolm Hudson, Dr. Paul Kemp, Dr. Simon Kemp and Dr. John Jones for help on the various sessions of field work. I am very much obliged to the many students over the years who have attended field trips to the Torquay area. Some of them appear in the photographs. I thank Oleksandra Pedchenko for a photograph of the Thamnopora. My wife Cathy helped me undertake examination of proven and possible raised beach remains at Hope's Nose and Berry Head in the early 1970s and this is very much appreciated. The Torquay Museum has kindly provided helpful information with regard to past student project work in the area. I thank Philip Wills for kindly sending me photographs of Petit Tor beach and allowing me to use them on this website. In particular, I am very much obliged to Nikolett Csorvasi, geologist of Torquay Museum for an excellent series of photographs of the Torquay cliffs taken from a boat and from the shores and cliffs. This is a valuable contribution and a significant part of this webpage. I particularly thank Kim Aldis for video and photographs regarding the Oddicombe landslide and in particular for his observations on the rising of the beach at the northern part of Oddicombe Bay.

REFERENCES AND BIBLIOGRAPHY OF THE GEOLOGY OF THE TORQUAY AREA

Anniss , L.G. 1927. The geology of the Saltern Cove area, Torquay. Quarterly Journal of the Geological Society, London, vol. 83, part 3, pp. 492-450.

Austen , R.C.A. 1835. An account of the raised beach, near Hope's Nose in Devonshire and other recent disturbances in the neighbourhood. Proceedings of the Geological Society [note - not Proceedings of the Geologists' Association] vol. 2., pp. 102-103.

Austen, R.C.A. 1842. On the geology of the south-east of Devonshire. Transactions of the Geological Society, London, vol. 6, pp. 433-489.



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Baron, M., Hilier, S., Rice, C.M., Czapnik, K., and Parnell, J. 2003. Fluids and hydrothermal alteration assemblages in a Devonian gold-bearing hot-spring system, Rhynie, Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences. vol. 94, pp. 309-324. Published online: 26 July 2007.

ABSTRACT:

Hydrothermal alteration at Rhynie, Aberdeenshire, Scotland, is concentrated along a fault zone, which juxtaposes surface deposits and the mineralised feeder zone to the Rhynie hotspring system. Mineralisation consists of breccias and veins filled with quartz, chert, calcite, K-feldspar and pyrite. Associated pervasive alteration comprises a high-temperature K-feldspar quartz-illite facies (formed at 250–350°C), a medium-temperature mixed layered illite/smectite quartz-K-feldspar-chlorite-calcite facies (formed at 150–200°C) and a low-temperature mixed layered illite/smectite-chlorite-calcite facies (formed at 100 to +150°C). The fluids responsible for mineralisation were mainly moderate- to high-temperature (Th = 91–360°C), low-salinity (less than 0·2 to 2·9 wt.% NaCl eq.) H2O-NaCl - heated meteoric fluids comparable to modern and ancient hot-spring systems. The migration of these fluids was mainly restricted to a major fault zone bounding the Devonian basin. Fluids responsible for mineralisation, alteration and cementation elsewhere in the basin were low-temperature (Th 57 to 161°C), low- to high-salinity (less than 0·2 to 18 wt.% NaCl eq.) H2O-NaCl fluids, which resemble basinal brines.

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Benton, M.J., Cook, E. and Turner, P. 2000. Permian and Triassic Red Beds and the Penarth Group of Great Britain. GCR (Geological Conservation Review), Series No. 24, Joint Nature Conservation Committee, Peterborough, 337 pp.

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British Geological Survey (BGS) . 2004. Geological Map - Torquay, England and Wales, Sheet 340, 1:50,000 Series, Solid and Drift. British Geological Survey, Keyworth, Nottingham. Available from the BGS Bookshop online for £12 and recommended. Sheet explanation booklet is is available for £9. Sheet Description (report) for map E350 is £35. Old Geological Survey memoirs relating to this sheet are those of Ussher (1903) and of Lloyd (1933)(see references below).

British Geological Survey (BGS) -

Leveridge , B.E., Scrivener, R.C, Goode, A.J.J. and Merriman, R.J. 2003a. Geology of the Torquay District: a brief explanation of the geological map, Sheet 350, Torquay. British Geological Survey, Keyworth, Nottingham, 34 pp. Abridged by A.A. Jackson from the Sheet Description of the British Geological Survey, 1:50,000 Sheet 350, Torquay, England and Wales. Price in 2010 - 9 pounds sterling [This is the short, inexpensive, summary version.]



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British Geological Survey (1933). By Lloyd, W. 1933. The Geology of the Country around Torquay. Second Edition, revised of: Ussher, W.A.E. The Geology of the Country around Torquay. With Palaeontology by C.P. Chatwin, M.Sc. and a Chapter on the Petrography of the Igneous Rocks by W.G. Shannon, D.Sc., F.G.S. London, His Majesty's Stationery Office, 169pp. Original price 4 shillings.

British Geological Survey. - Ussher, W.A.E. 1903. The Geology of the Country around Torquay (explanation of [BGS Geological Survey Map] Sheet 350). Memoirs of the Geological Survey of England and Wales [predecessor of the British Geological Survey], 142pp. Published by Order of the Lords Commissioners of His Majesty's Treasury. London, original price Two Shillings. By William Augustus Edmond Ussher. Reprinted as a facsimile by the Book Depository and available for £19. 38p. and can now be purchased through Amazon.

British Geological Survey. - Ussher, W.A.E. 1913. The Geology of the Country around Newton Abbot. By W.A.E. Ussher, F.G.S., with contributions by Clement Reid, F.R.S.; J.S. Flett, M.A., D.Sc.; and D.A. MacAlister, A.R.S.M. Memoirs of the Geological Survey of England and Wales, Explanation of Sheet 339, Newton Abbot. Published by order of the Lords Commissioner of His Majesty's Treasury, H.M. Stationery Office. 149pp. with two plates of photomicrographs and with an Appendix - List of Principal Works on the Geology of the District.



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Braithwaite, C.J.R. 1964. Middle Devonian Sedimentation in South Devon. Unpublished Ph.D. Thesis, University of London, 375pp, 243 illustrations.

Braithwaite, C.J.R. The petrology of Middle Devonian Limestones in South Devon, England. Journal of Sedimentary Petrology, vol. 36, part 1, pp 176-192.

Braithwaite, C.J.R. 1967. Carbonate environments in the middle Devonian of South Devon, England. Sedimentary Geology, vol. 1, pp. 283-320. By C.J.R. Braithwaite of the Department of Geology, The University of Dundee, Dundee Great Britain.

Abstract:

Evidence of depositional processes in the sedimentation of Middle Devonian carbonate rocks in south Devon is presented. It can be resolved into two groups.

1. (1) Palaeontological evidence suggests that (a) there were a number of restricted environments, and (b) rates of sedimentation were slow, to allow both for the normal growth of corals and stromatoporoids and to allow the growth of other organisms, corals, stromatoporoids, algae, or debris derived from these.

2. (2) Much of the physical evidence suggests a rapid mode of deposition, thick muddy beds packed with large disoriented fossils, and other coarse, poorly sorted, clastic beds with current influenced structures. One way of reconciling these opposing views is to suggest that during the bulk of time depositional rates were low, allowing the growth of organisms, but that periodically disturbances occurred which detached organisms from growth sites, sometimes transporting them and depositing debris elsewhere. These produced sudden influxes of mud in some areas, killing off corals, whereas adjacent sites could have been subject to emergence and/or erosion. The carbonates occupied a linear belt of shallow water, perhaps to the north of a low-lying land mass. Sedimentary structures within the limestones, and the apparent relationship of these rocks to enclosing sediments, indicate that the organisms concerned did not at any time form a continuous wave resistant structure comparable with a modern reef.



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Brookfield, M.E. 2000. Temporary Desert Lake Deposits, Lower Permian (Rotliegendes) Southern Scotland, U.K. Chapter 4, pp. 67-73 in: Gierlowski-Kordesch, E.H. and Kelts, F.R. 2000. Lake Basins Through Space and Time. AAPG Studies in Geology. No. 46. The American Association of Petroleum Geologists. Edited by: Elizabeth H. Gierlowski-Kordesch and Kerry R. Kelts. Paper by M.E. Brookfield, Land Resource Science, Guelph University, Guelph, Ontario, Canada.

[The descriptions of the alluvial fan and pediment ponds relates well to the examples of such pond deposits in the Permian breccias at Corbyn's Head, Torquay (this Torquay webpage) and one present at Hole Head, near the Parson and Clerk rocks, Holcombe, near Dawlish ( Teignmouth to Dawlish - webpage)]

Relevant extracts from the Introduction etc:

During the Late Carboniferous to Early Permian, a large lowland desert developed over the whole of southern Scotland.

Several desert basins were eroded into softer Carboniferous sediments preserved in postdepositional grabens within the lower Palaeozoic Southerh Uplands massif (Figure 1) (Brookfield, 1978, 1980; Glennie, 1982)......

Northwesterly directed faulting then formed the isolated graben of the Moffat, Lochmaben, and Dumfries basins to the south and east. In these grabens marginal alluvial fan sequences are dominated by immature streamflood and sheetflood breccias and sandstones with interbedded aeolian sandstones that pass basinward into into massive dune sandstones. Depositional facies are those of very arid intermontane basins summarised in Figure 2 (Brookfield, 1980; Nielsen, 1982). The fan deposits have anguular, poorly sorted clasts and often contain abundant well-rounded, reworked, coarse aeolian sand and reworked ventifacts derived from the fan surfaces. Silt and clay are rare and probably were mostly removed by the wind; nevertheless rare silt and clay beds are occasionally interbedded with the pediment, alluvial fan, and aeolian deposits.

These fine-grained sediments were deposits in ephemeral ponds and lakes and provide additional data on palaeoenvironments. Such deposits are rarely described from sections of ancient and desert deposits because the most impressive units are the alluvial and eolian deposits (cf. Brookfield, 1984).

The purpose of this paper is to record the facies and paleoenvironments of the rare lake and pond deposits of an ancient arid intermontane desert, compare them with modern examples, and note their significance for paleoenvironmental interpretation. Detailed descriptions of the associated facies and justification of the assigned processes and environments are in Brookfield (1978, 1979, 1980, 1989).

Section - Alluvial Fan and Pediment Ponds

After floods, silts and clays can be seen settling out of suspension in small ponds on pediments and alluvial fans. Due to the slope of pediments and the slope and porosity of fans in very arid environments, such pond deposits are exceedingly small, short-lived and likely to be removed during later flash floods; nevertheless such pond deposits can occasionally be preserved beneath overlyin deposits.

In the Thornhill basin, thin pond deposits occur between basalt eruptions on the incised pediments. Figure 3A shows fine-grained sediments deposited in a depression between two successive lava flows. the seidments consist of of two fining-upward cycles, each of which starts with an erosion surface on which rests cross-bedded, graded pebbly sandstone. This is overlain by alternating thin beds of graded sandstones passing up into planar laminated micaceous siltstones overlain by mud-cracked silty mudstone. Each fining-upward sandstone-siltstone bed is between 20 and 50cm thick and probably marks the waning stages of successive sheetfloods across the pediment due to overflows from incised pediment channels. Successive mudcracked surfaces within the overlying mudstone unit indicates sporadic rainfall and redistribution of fine sediment before the next major flood. The end of this particular pond is marked by a thin eolian lag, covered by the next basalt eruption.

.... continues





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Busz, K. 1893. Note on igneous rocks, Babbacombe Bay. Sitz. d. Niederrheinische Gesellsch. Bonn., Germany. p. 95. By Dr. K. Busz.

Camm, G.S. 1995. Gold in the Counties of Cornwall and Devon. First published 1995 by Cornish Hillside Publications, St. Austell. By G. Simon Camm. Printed and bound by the Short Run Press Ltd., Exeter, Devon. ISBN 0 9519419 7 6. Price �35 plus shipping (in 2012).

[type of book: this is both geological and historical and very interesting in type. It gives the names of obscure and rare minerals and explains their chemical composition. It has useful diagrams showing concentrations and fluid migration directions. It is basically easy and informative reading for anyone with a basic geological background and does not require specialist knowledge of ore mineralogy or orefield fluids. It is very well and clearly illustrated with colour pictures of gold. It contains a section on gold panning. It has a good reference list. I think that the reader will be sorry to finish it, but it remains a source of reference. It would be even better if it was twice as long. The book is recommended for purchase.]

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Carozzi, A.V. 1961. Reef petrography in the Beaverhill Lake Formation, Upper Devonian, Swan Hills area, Alberta, Canada. Journal? Vol,31, pp. 497-513.



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Cattell, A.C. 1997 The development of loess-bearing soil profiles on Permian breccias in Torbay. Proceedings of the Ussher Society, vol. 9, pp. 168-172

Cattell, A. C. 2000. Shallow foundation problems and ground conditions in Torbay. Geoscience in South-West England, [Proceedings of the Ussher Society], vol. 10, pp.068-071

Abstract:

Problems with shallow foundations are unusually common in Torbay. Subsidence cases run at perhaps twice the rate (per head of population) of other urban areas in South West England. The distribution of cases in Torbay is controlled by the underlying geology. Dramatic problems are associated with solution features in the Devonian limestones, but although these can be severe, they are not common, and the firm silty clays developed on the limestones do not normally give rise to problems. Ground conditions on the Devonian slates, sandstones and igneous rocks are generally good, although movement due to shrink-swell of residual highly plastic silty clay soils is known locally. Problems associated with soils developed on Permian breccias are both very common and often severe: these are sometimes associated with loess horizons within the soil profile. Amongst the breccias, problems are much more common on the Oddicombe Breccia than on the Watcombe Breccia. The worst ground conditions occur where thick colluvial deposits are developed on lower hillslopes on the Oddicombe Breccia; the colluvial soils are unconsolidated sandy silts which are very susceptible to loss of strength on wetting. [end of abstract]

[brief extract regarding the Oddicombe Breccia, the strata involved in the major rock fall at northern Oddicombe Beach.

"Conclusions:

The frequency of subsidence problems in shallowly founded buildings correlates strongly with bedrock in Torbay, the likelihood of problems on Oddicombe Breccia being roughly twenty times the likelihood on other rock types. On Devonian slates and tuffs, the most common problem is seasonal movements caused by shrink-swell of silty clay residual soils, but such cases are uncommon. On limestones, problems are caused by karstic features: the problems can be severe, but are rare.

On the Oddicombe Breccia, problems are caused by leaking services wetting the soils. Colluvial soils developed on the Oddicombe Breccia are extremely prone to loss of strength on wetting. Problems are most common and most severe at the base of slopes, where the colluvial soils are thickest."]



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Clayden, A.W. 1906. The History of Devonshire Scenery; an Essay in Geographical Evolution. Book by Arthur William Clayden. 202 pp. Available in paperback from Amazon, 14 pounds, 31p. Digitised by Google and available online. Includes: Introduction; The Devonian Rocks of North Devon ; The South Devon Rocks; The Culm of Devon; etc.

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Cowper-Reed, F.R. 1920. Notes on the Lower Devonian Beds of Torquay. Geological Magazine, pp. 129, 341.

Cowper-Reed, F.R. 1921. Fauna of the Lower Devonian Beds of Torquay, Geological Magazine, p. 313.

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Daily Mail Reporter. 2010. No wonder they got it cheap: Clifftop home loses its garden just six days after new owner paid bargain price of 150,000 pounds. 24th February 2010. [re Oddicombe Beach, Torquay]. ........

Brief extracts: Ridgemont House now sits just 50ft from the edge of the 300ft cliff. The home was deserted by its last owners who feared it was too unsafe

........ A homeowner who splashed out 150,000 pounds on a clifftop house suffered a property crash just days later - when the bottom of the garden collapsed in a massive rock fall. The large six-bedroom property was sold for the bargain price because of its precarious position overlooking Oddicombe Beach in Torquay, Devon. It was bought for 150,000 pounds last week, but just six days later more than 5,000 tonnes of rock at the bottom of the garden collapsed into the beach below.

......... Luckily no-one was hurt but Ridgemont House lost a 'substantial' chunk of its land and now sits just 50ft from the edge of the 300ft cliff. One neighbour said: 'Apparently the cliff collapse was sparked when a large boulder the size of a Transit Van fell off and the whole lot went. 'It happened in the middle of the night so no-one saw how bad it was until daylight. It was a huge cliff fall. 'Ridgemont House lost a large chunk of its land - it was only sold last week. Whoever bought it took a big risk - the timing was pretty terrible.' ........ A Torbay Council spokesman said the beach below has now been closed for fear of further rock falls. He said: 'The 5,000-tonne rock fall was from the unstable sandstone cliffs to the rear of north beach. Secondary rock falls are still occurring and the whole of Oddicombe Beach will now be closed for several days.' ..... [continues]

[see full report, which includes an aerial photograph]



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Devon County Council. 20??. undated. Devon's Rocks - A Geological Guide.

"Welcome to our guide to the rocks of Devon. This webpage contains guides to 13 different rock types found in Devon. We hope yo