County Geologies: A-Z

COUNTY GEOLOGIES

BEDFORDSHIRE

Bedfordshire is in the South Central Midlands of England and is dominated by the Great Ouse which flows through the county from west to east. Prior to the Anglian Ice Age (480,000- 425,000 years ago) a large river- the Bytham, ran along a similar course which included some of the valley of the Upper Avon, to join the ancestral Thames somewhere off the Norfolk Coast. They then ran north to the Scheldte-Rhine system and that drained north to the Arctic Sea- but the hydrography of the region was utterly transformed by the ice sheet and the Thames found a new course east from Reading. The Ancestral Thames ran beneath the Chiltern Escarpment in the south of the county. The historic counties about Bedfordshire are Huntingdonshire, Peterborough (Soke), Cambridgeshire and the Ile of Ely, Hertfordshire, Buckinghamshire and Northamptonshire. The Ouse leaves Bedfordshire near St Neots and flows via the modern Vermuyden drains and artificial rivers into the Wash. The Lea also rises in this county and flows south to the Thames forming the border river of Essex and Herfordshire. Luton is named after the Lea River. Some of the northern streams of Bedfordshire feed the Nene. Both the Ouse and Nene rivers must formerly have been navigable for Viking place names follow their courses into the heart of the Midlands.

The Northern Uplands are a Boulder clay ridge carved into by the valley of the Ouse. This was laid down by the Anglian Ice Age. The next ice event- the Wolstonian, ran as far south as Coventry and so probably covered none of this county- though melt-waters from it would have done. The last Ice Age, the Devensian, certainly stopped well north and could not have contributed drift glacial material to the county.

North Bedfordshire is mainly Oxford Clays with some Oolithic limestone exposed. This stone has a grain which is “egg like” under a glass- hence the name “Ooltite”. It is essentially the same rock as that which forms the Cotswold Hills. It is a Jurassic rock, formed 180-130 MYA – initally from the remains of marine animals- although limestone can be recycled from older strata. Above the Oolithic rock is “Cornbrash Limestone” and above that Kellaway beds of sandy clay which in patches is hardened into a accreted sandstone. To the south there are greensands which are Lower Cretaceous (old Cretaceous), then gault clays and then the chalks of the Upper Cretaceous Chilterns. This pattern of Jurassic, Greensand, Gault, Chalk is common as a sequence and suggests an anticline not unlike that of the Weald- if so then there is a clear pattern: – anticline in Bedfordshire, syncline in the London Basin and anticline again is Surrey, Sussex and Kent- the three this describing a very large wave like structure in the bedrocks and where as the older Jurassic rocks are buried deep beneath the London Basin, they are exposed in North Bedfordshire and the Central Weald as the “doming” of these two waves has been eroded down. An eroded anticline shows the oldest material at its centre. Woburn and Ampthill are on the greensand. The Chalk has eroded and washed down the Chilterns to mix with the gault clay forming a “marl”. Nearby is a clunch (hard chalk sometimes used in building) and locally this is called Totternhoe Clunch. In Hertfordshire the Ice sheet covered the chalk hills and eroded them down to about 400-500ft but in parts of Bedfordshire it did not and the Chilterns can rise to 800ft at Dunstable. Flints occur in the upper (latest) chalk which cap the hills..

Oxford Clays in Bedfordshire are dark, sticky and do not drain well. Boulder clays are lighter and have chalk and stone pebbles and gravel in them and so they drain better.

The transition from Limestones to Greensands to chalks is reflected in the flora, with oaks more common on the sandhills and beeches, holly, and yew more suited to the chalk and calcareous soils. The various bands also see different land uses with the arable farms on the clay soils and the grazing on the gault and chalk.

The event which pushed the chalk and Jurassic strata into hills and bowls was the Alpine Orogeny (mountain building period) of 50 million years ago. It is difficult to see the Chilterns and Oolithic limestone ridges as the last foothills of the Alps.

Flitwick is unique for here in the Ouse Valley an undrained bog land on alluvia with peat has survived.

The fossils in the limestone, greensand and chalk would have to be marine. But in the alluvial valleys mammalian fossils from the Pleistocene are found including rhino and mammoth. These are reckoned to be Pre-Ice Age, but after the Anglian ice sheet had retreated there was a warm stage called the Hoxnian in which African type animals roamed here. Acheulian culture dwelling places (people) have been found near Cardington. This is the same Hoxnian stage culture as that found in Suffolk where the village of Hoxne gives the episode its name. The other two places associated with Hoxnian hominids are Clacton in Essex and Swanscombe in Kent. The ancient people who walked on the river muds at Happisburgh in Norfolk were older for they lived on the banks of the ancestral Thames and must therefore have been there before the Anglian Ice Age.

BERKSHIRE

Berkshire west of London Basin and the Berkshire Downs are Upper Cretaceous chalk and the edge of the London basin. The chalk outcrop slopes gently away to the south and sands and clays of Tertiary age form the floor of the basin. With, no doubt, chalk deep beneath them. Bagshott Beds and other closely sedimented strata witness a time when ther Basin was a shallow inlet or estuary- sometimes brackish, sometimes fresh water.

The oldest strata in Berkshire are further north- Oxford clay, laid down in the Jurassic period. It is fossil rich with marine dinosaurs, crocodiles and turtles as well as plants preserved within. It was laid down abouyt 160 MYA in sediment rich seas- presumably ones near a coast line. seas. It tends towards a mudstone and hard in places and is greyish and is seen at Lechlade and north towards Oxford close to the Thames which must have eaten away the upper strata to expose it. Chalk is categorised in three strata Lower, Middle and Upper. The flints appear in the Upper which suggests a source of silicone absent before. Few Lower Chalk strata are exposed

just a little near Lambourn and Streatley. The Middle chalk forms an escarpment running to Streatley and is almost pure chalk suggesting it was laid down far from coastal influence or estuaries. The Upper Chalk is seen at Hungerford, Lambourn and Basildon. It is covered with drift material- clays, gravels and flints which must formerly have been in it but have now eroded out.The Upper Chalk is exposed at Maidenhead, Henley and Cookham, presumably by the break through of the River Thames in the Anglian Ice Age.

The Chalk sinks to the south beneath Tertiary deposits and escarps to the north forming the south face of the Vale of the White Horse. The valleys running in from the escarpment are from the Pleisocene but were probably not ice- unless seasonal because it is unlikely that any of the Pleistocene ice ages- the Anglian, Wolstonian or Devensian, covered this landscape. In the east knolls of chalk stand out, one being Windsor- here the land descends into the London Basin and the county meets Surrey- the border running through parts of Windsor Great Park.

The clays and sands of the South are Lambeth Group Tertaries . These are shallow sea deposits. Above them are Reading clays laid down by rivers.

On the Chalk hill tops Sarsen stone is found. This is a silcrete of sandstone and is late- Post Cretaceous. It is the material often used by ancient monument builders. Why it broke up so rapidly is difficult to see, for it is harder than the chalk, but in so doing it must have released silicates which could have permeated the Upper Cretaceous chalk and added to the flint nodule layers there. However the silicates must have had an animal source- probably the hard parts of silica-sponges. The cementing of the Sarsen is between 10 million years ago and the much later ice ages- so it is a very young rock from the Cenozoic era.

The London Clay on the southern borders of Berkshire is a marine sediment- attested by its fossils. The Bagshot Beds which vary considerably from sands to gravels to pipe clays overlay the London clay.

It has been suggested that although Berkshire was not scoured by an ice sheet, it was frosts in this marginal tundra landscape which broke up the sarsen.

Interim bands where the chalk meets the Jurassic Oxford Clays include greensands and gault clays- these are Lower Cretaceous 130-90 MYA

BUCKINGHAMSHIRE

Buckinghamshire connects the southern Cotswolds with the Chilterns. It has two river basins of note: the Great Ouse in the north and the Thames in the south.

The Cotswold Stone in the north is oolithic limestone from the Jurassic period. This is stone with an egg shaped grain, which is what oolithic means, it was laid down in a sea in the period roughly 200-130 MYA. The Chilterns which begin just south of the Thames run unbroken through Buckingham, parts of Hertfordshire and into Bedfordshire and fade into the chalk of North Essex and Suffolk. The range continues north under the Teriary and Quaternary deposits of East Anglia to re appear in the Lincolnshire Wolds and East Yorkshire. The chalk is Cretaceous from 130-66 MYA, generally it dates from the 2nd half of that period. It is a marine zoic deposit which seems to have come to an abrupt end with the K Pg mass extinction event- allegedly caused by a meteorite impact off Yucatan. Probably the Jurassic rocks run under the chalk, for in the anticlines of North Buckingham and the Weald they reappear as the domed strata have been eroded. The Thames Basin displays a syncline of chalk overlaid by London Clay and other deposits- so if the geology of the home counties is seen in the large, a great wave formation is observed from anticline to syncline to anticline. These strata were laid down on flat ocean beds and their raising was a peripheral phenomenon of the Alpine orogeny (mountain building period) of 50 MYA in the Pleistocene. The Oolithic limestone of North Buckinghamshire runs west to fade away in the vicinity of Bristol and South Gloucestershire. Companion strata with the chalk are gault clay and greensand- both are deposits from the Lower Cretaceous and were laid down a little earlier than the chalk. The lower land of Buckinghamshire shows Oxford clays and Kimmeridge clays. In the south-east of the county are London clays and Reading beds from the Eocene. The Eocene is an epoch of the Tertiary period and follows the Cretaceous to about 45 MYA. Generally the chalk hills of the county are capped with later material from the Tertiary period. The endemic tree of the region is the beech and Burnham Beeches is a remnant of an ancient and extensive forest. The beech was much used by the chair industry of Buckinghamshire- particularly about High Wycombe- but, interestingly, early “Windsor Chairs” were fruit wood and yew not beech so it might be that there were formerly extensive orchards and yew woods which, when exhausted by that industry, were substituted with the faster growing and less expensive hardwood. All such articles had elm seats and so another now largely vanished tree is represented in them and must have been widespread in this environment.

The Thames which forms Buckinghamshire’s southern border, formerly struck north-east following the north and west facing escarpment of the Chilterns. It then crossed East Anglia in the vicinity of the modern Waverney River and thence north towards the Rhine and Scheldt. It was joined by another ancient river- the Bytham, which formerly ran through valleys now occupied by the Avon and Ouse; thus two courses of two pre-historic rivers are important in the south, east and north of the county. It is difficult to know how much of the county could have had glacial drift material on it. The Anglian Ice sheet of some 250,000 years ago extended south to the Crouch in Essex, eroded the Hertfordshire Chilterns but did not erode the chalk at Dunstable. This was the event which diverted the Thames and it would appear that the southern boundary of the ice was roughly on a south-east north-west line from the Thames Valley in Essex to the High Chilterns of Bedfordshire- but then where?

The second great ice event, the Wolstonian, stopped in the latitude of Coventry and so that would not have deposited drift material here. The last ice age- the Devensian- had a limit much further north (Glamorgan to Flamborough). Of course melt water rivers and lakes from each of these events may well have crossed the county. As the Anglian ice sheet blocked the ancient Thames no doubt a lake backed up across Buckinghamshire until there was sufficient depth and power to force through the Southern Chilterns in the vicinity of Reading, Cavisham and Cookham. Buckinghamshire has interesting isolates of rock strata: Portland Stone, Purbeck stone, Lower Greensand and gault knolls at Muswell and Brill Hills. The evidence of ancient people in Buckinghamshire is curiously scant- except for Paleolithic groups moving up the Thames. Even later, the Saxons did not populate the High Chalk in anything like the numbers seen on the Downs of the Weald and it has been speculated that residual British populations made up the majority of the peoples here. Another curious aspect of the geography is that the most ancient pre Roman routes- such as the Icknield Way, tend to avoid high ground. Elsewhere “High Ways” are the general rule- not “Low Ways”. In summary, from the Paleolithic to the Anglo Saxon settlement, there was something undefined which seems to have dissuaded people from settling certain tracts of Buckinghamshire- particularly the high lands of the Chiltern Hills.

CORNWALL

Although Cornwall is dominated by the Cornubian batholith- a mass of granite of unknown depth which stretches all the way from Dartmoor to the Scilly Isles, these are not the oldest rocks. The Oldest are the Devonian sequences which surround the granite from Penzance to Truro and right across the Peninsula just east of Bodmin. The metamorphic granite has punched through the Devonian limestone at a later date. In that triangle of North Cornwall north of Launceston, there are carboniferous rocks and these too are older than the granite but younger than the Devonian. Right in the south of the county, in the southern half of the Lizard peninsula are schists and serpentines.

This southern phenomenon, on the Lizard, is an Ophiolite (which means “snake stone”) and this is oceanic earth’s crust which has been lifted up to the surface. Ophiolites are not old geologically- generally about 50 million years- and so one has to look to quite a recent orogeny to explain them. They are ususally pushed up by nearby magma plumbs and the orogeny which is the right date in this part of the world is the Alpine Orogeny (mountain building period.) They tend to be green hence the name “Ophiolite”, and “Serpentine” seems another Latin or French based way of saying the same thing.

The granite batholith was also pushed up by an orogeny but in this case the Variscan event of East France and Germany which took place in the Permian period 260-255 MYA. This does not prove that the rocks are of that age- but that is when they were pushed up from below the surface through the older Devonian rocks. It will be noted that, in Cornwall, the north and west coasts have the tin mines or wheals and the south coast has many rias or sunken river valleys and few if any tin mines.  Veins of tin emerge in the north west which do not emerge in the south; valleys flood in the south which do not flood in the north. If one imagined that the entire structure of the batholith tended to rise up on the north side and sink on the south- that might explain those two phenomena. The batholith seems to move and perhaps rotate down to the south. It is known that it has migrated west from a position formerly further east. Batholith means “Bathos”: depth; “Lithos”: stone.

The northern carboniferous rocks of Cornwall are called the Culm Measures and they are folded in an extreme manner. The best example being the Whaleback Pericline near Bude. Culm is a Devon word for a form of sooty coal found in these carboniferous measures but the derivation may be Cwlwm meaning “knot” in Welsh rather than the Anglo Saxon word “Col” which is “coal”. This period was when Britain was at the equator 340-205 MYA.

The Devonian Rocks are of the typical “Old Red Sandstone” varient and they are 405-340 MYA in the period before the Carboniferous. So logically Britain was then south of the equator- about 12 degrees south. Sandstone must be a marine stratum and so the county was covered by a sea in the Devonian- if it contains fossils, they also would be marine. Sandstone is recycled eroded mountains and the most likely source would then have been the Caledonian Mountains which had formed earlier when Laurentia ( including North Scotland) had collided with Avalonia and Baltica (Britain).

Thus simply: The Caledonian Orogeny erodes and seas lay down the debris as Old Red Sandstone in the Devonian. Late Carboniferous rain forests lay down the Culm but only in the north of the county. Then the Variscan Orogeny pushes the sandstone up and pushes the granite batholith through it, particularly on the high moors of Cornwall. This batholith wanders and possibly rotates as it settles. Much later the Alpine Orogeny which crumples all Southern Britain from the chalk in the south east to Cornwall- causes igneous events which push old ocean floor up and this is seen in the Serpentine and Schist Ophiolites of the Lizard.

The Rias of the south coast (fjords) and tin veins in the granite of the north coast support the notion that the peninsula subsides to the south and rises to the north.

DEVON

For a county that one might suppose is dominated by Devonian Old Red Sandstones, it is interesting how much of the county is quite different. All the north western part crossing into north eastern Cornwall has carboniferous Culm rocks which bear sooty coal like deposits and are greatly folded on the north west coast. These are slightly later than the Devonian sequences and date from when Britain was on the equator. Cwlwm is a Welsh word for a knot and that is the probable source of the work “Culm”.

Dartmoor is Granite and the most eastern end of the great Granite batholith which underpins the region from here to the Scilly Isles. This batholith was uplifted by the Variscan Orogeny (mountain building event) in the Permian period, and so that is both later than the Devonian and the Carboniferous. Batholith means “depth-rocks” (Bathos-lithos) and the mass is of unknown depth. They are metamorphic and have punched through the Devonian Sandstones right down the peninsula (or eroded through them). These rocks have veins of copper and tin in them but that is more mined to the west than here.

Right in the south of the county are Schists and Serpentines: Ophiolite rocks which were in the crust of the ocean floor but were pushed up to the surface in relatively recent times- 50 million years ago. Serpentine and Ophiolite both mean the same thing “snake rocks” and that refers to their greenishness. In the east of the county are greensands and gault clays and Triassic sandstones. The greensands and gaults are Cretaceous formations- laid down under water up to about 66 million years ago when the Cretaceous ended with the K PG mass extinction event. This is (perhaps) the furthest west that such formations are seen and these rocks are most common in Surrey, Sussex and Kent where they lie in close proximity to the chalk.

The Devonian sandstones and volcanic rocks lie in the south of the county- just north of the Serpentines and Schists and in the north of the county. Devonian is the 4th period of the Paleozoic era 315-255 MYA. These are the older rocks of the county. If the sandstones have fossils in them, they would be marine for they were laid down under water. The Carbonifereous rocks formed after the Devonian. Between the two periods Britain has drifted from 12 degrees south to the Equator.

There is an interesting fault line through Devon called The Sticklepath Fault. It begins in the north west in Bideford Bay and the Torridge follows it in its lower reaches, The Fault crosses Dartmoor heading south east to the coast. This fault dates back to the Permian Period and was active well into the more recent Tertiary period so it is younger than the Devonian and Carboniferous rocks and dates from the Variscan mountain orogeny which pushed the sandstone, culm and granite batholith up.

SUMMARY

Devonian volcanics and sandstones were followed by rain forests which laid down the Culm in the Carboniferous period. Mountains off to the east pushed the sandstone and culm up and pushed the great granite batholith to the surface in the Permian period. They also caused the fault lines of the region. Right in the east, greensands and gaults show that a Cretaceous sea laid down strata 130-66 million years ago, and these were raised up by the Alpine Orogeny a comparatively recent 50 million years ago.

ESSEX

Essex is geologically dissimilar to East Anglia in that it is dominated by the late deposits of the London Basin. The solid geology here is a Chalk Syncline which rises to the surface in the north west of the county, about Saffron Walden- and to the south in North Kent with a small section of chalk about Purfleet and Thurrock where it has been long quarried for lime and cement making.

Within this basin are clays and gravels: which are alluvia from the Thames, Crouch, Blackwater, or glacial drift material further north. There is a a line of moraines near the Crouch which marks the southern extent of the Anglian Ice Age. This event was 480-425,000 years ago; it diverted the Thames which previously had run north-east across East Anglia and then north to join the Rhine. The later Wolstonian and Devensian ice sheets did not cover the county.

Drift material can be very deep : nn the Cam valley near Newport, it is 340 feet deep, so here is a considerable glacial gorge infilled with dift. The stones within the gravel- being glacial, may have origins far to the north: perhaps in Yorkshire or Durham

The hills are seldom above 400ft: Laindon may be a moraine, Danbury Hill is said to be the highest point between London and Moscow. It is the larges significant height before the North Sea and North German Plain.

Rivers flow generally south and east and the main estuaries are the Stour, Colne, Blackwater Crouch and Thames. Two rivers define the historic county: The Lea to the west and the Stour to the north: So, strangely the county has water frontiers on all four sides. Essex has more islands than any other English county:,probably more islands than all other English counties; the largest being Canvey, Mersea, Potton and Foulness. Several rivers are remarkable in having changed their names through history: Chelmer: Badona; Pant-Panta- Blackwater; Granta-Cam. The rivers are shallow and broad, muddy and slow. The traditional craft of the region are therefore flat bottomed & have lee-boards, not keels- which are lowered from the sides to prevent drift to leeward on the tack.

The soils of the north are boulder clay and gravel over the chalk. Thus here is a solid geography which is Cretaceous and up to 66 million years old and a drift geology which is Pleistocene and much more recent. Under the chalk are probably Jurassic strata but they do not reach the surface hare. The undulation of the chalk- with anticlines in the Weald and synclines here- are due to the Alpine orogeny (mountain building event) of comparative recent times (60-50 MYA)

An unusual outcrop on the coast at Walton is Red Crag.

The Drift material cliffs of Frinton and Walton erode quickly. Elsewhere the county has sea walls which were breached in the disastrous floods of 1953. Now some sea walls have been dismantled to encourage salt marshes, help ecology and relieve pressure on flood waters which funnel into the estuaries. The south of the county was formery covered with forest-Waltham Forest, but is is largely reduced to Epping and a few other remnants.

The county has England’s oldest recorded town at Colchester and a possible site for the illusive Mons Badonis Battle of Arthurian (post Roman) times (mentioned in Nennius, Gildas, Bede): Danbury Hill, where Little Baddow, nearby Great Baddow and the Chelmer (Badona)- provide the most likely cognates for this unfound battle site. Here also was a substantial defence line constructed the IInd World War when an invasion from the eastern coast was anticipated. It runs through the Boreham, Sandon, Hanningfield region.

HAMPSHIRE

This is a diverse county and has regions which touch on the Thames Basin, the Weald, and the heathlands of Dorset. It is touches by Dorset, Wiltshire, Berkshire, Surrey and West Sussex. Historically the Isle of Wight was periodically part of the county or independent. The county name is an abbreviation of Southamptonshire. There are four distinct areas in the geology of Hampshire: a belt of chalk land crosses the centre on the latitude of Winchester. This gets to 800ft in places- as high as any parts of the North of South Downs. North of this chalk are Tertiary clays and gravels, which were laid down later than the chalk, water deposited and diverse. In the east of Hampshire is the Western Weald, with the same geology as that seen in parts of Surrey, Sussex and Kent.

The oldest rocks are the Folkestone Beds, which are sandstone and run through the middle of the Wealden anticline. These are 300-130 million years old. The next oldest are lower greensands, upper greedsands and gault clays which are from the Lower Cretaceous (early cretaceous) . After them chronologically comes the chalk- Upper Cretaceous- and formed on the bottom of a shallow seas. Interestingly this chalk is divided into three groups: Upper, Middle and Lower and it is the latest, the upper chalk strata which bear the most flints.

The other deposits of the county come after the Cretaceous, which is also after the K Pg mass extinction which brought this period to a close. So as Hampshire geology is laid down the county, with Britain, drifted from 30 degrees north to its modern position at about 51 degrees north. Note that all these strata are comparatively recent geologically, there are no volcanics and no metamorphic rocks. It is interesting that the Cretaceous and Jurassic sea beds were pushed up into hills by the Alpine orogeny (mountain building period) of the Paleogene (50 MYA). It is odd to see these gentle hills as foothills or “ripples” of the Alps. The sandstone of the Hastings Beds was material deposited as the Varscian orogeny (a French mountain building eposode) eroded down. Mineral sands and sandstones are recycled mountains.

In the north the Bagshot Beds and other Tertiary and Quaternary strata were laid down under seas and inlets which waxed and waned and alternated between salt, brackish and fresh water. Thus they display thin strata which differ between sands, gravels and clays- one of which “Pipe Clay” was exploited in the 18th and 19th century. The fossil record of Hampshire (before the Pleistocene) must be of marine creatures and plants.

No recent ice age, neither the Anglian, Wolstonian or Devensian, had an ice sheet which came as far south as Hampshire- so ther4e can be no glacial drift or boulder clay in the county.

The south of the county sinks. This is the corollary of Isostatic Rebound in the north of the island where land reacts to being relieved of the weight of the ice sheet. Anciently there was a river- The Frome or Solent which had tributaries such as the Boldre (Lymington River) Exe (Beaulieu River). Hamble, Meon, Test and Itchen. This “Frome” or Solent was flooded and became an inlet of the sea as were some of its tributaries such as the Exe or Beaulieu River. Originally it flowed east to the sea through Spithead. The Western Solent broke through later and the Needles are the remnants of a chalk ridge which linked what is now the Isle of Wight to the Dorset coast and the Purbeck Hills. Not all rivers flow south to the Channel: the Wey, Loddon and Blackwater run north to the Thames. The Chalk rivers of Hampshire, particularly the Avon, demonstrate a curious feature: ice can build up on the river bed over which running water flows. This is called Anchor Ice and perhaps is due to Hampshire chalk rivers seldom having tributary steams but are fed by ground water running directly into them from the chalk. The Itchen is a good example of a river which “appears” without many visible tributaries. One of its few feeder streams the Candover- seems to have a very ancient British name meaning “Luminous Waters”.

The poor heathland and woodland of the county has contributed much to its preservation: being scarcely viable as farm land it became a great hunting forest in the South West (The New Forest) and extensive army land in the north and north east- near Aldershot and Woolmer Forest.

The county has lost land to Dorset in the west. Bournemouth was a Hampshire town and has geological similarities with the Isle of Wight- both having “chines” or wooded valleys or gorges running down to the coast. Bede called the county “Juteland” and linked its settlement with that of Kent and the Isle of Wight which he also claimed was settled by these people. Its major city- Winchester was capital of the Belgic Regni and the West Saxons. It would appear that the norther border of Hampshire was formed by the border of the Belgic tribes with the none Belgic people to the north. The root word found in Southampton, Hampshire and Hants is “Hamps” and means “ Summer Dry” suggesting streams that flowed seasonally. Like Essex and Somerset, Hampshire has the curiosity of a country town which is not the most historically important of its cities.

It is the sinking coastline of Hampshire which has made it of primary importance to shipping, for here is one of the major merchant marine ports: Southampton and Royal Navy Ports: Portsmouth: both on flooded natural harbours.

HERTFORDSHIRE

This is a geographically interesting county linking the Chilterns chalk hills with the London Basin, and having within it much of the history of the Ancestral Thames. It is a county touched by the Anglian Ice Age, but not by the ice sheets of the later Wolstonian or Devensian episodes.

The County is on a syncline of chalk falling away to the south and disappearing under London. To the north it escarps. These Chiltern Hills are scarsely over 500ft in Hertfordshiore, for they are ice eroded. In Bedfordshire, at Dunstable, they are not touched by the Anglian Ice sheet and so retain the standard 800ft seen on the North Downs, South Downs and Hampshire chalk hills. The chalk was created on the floor of a sea in the Cretaceous period 130-66 MYA. It was raised in to hills by the rippling effects of the Alpine Orogeny (mountain building episoide) 50 MYA in the Pleistocene. The Escarped northern edge of the Chilterns was the right bank of the Ancestral Thames, which flowed north east and then roughly across the the Waveney Valley to the present coast where it ran north to join another acient river the Bytham (Avon-Ouse

region). The combined river then flowed in to the Scheldt-Rhine system. It was the Anglian Ice Age of about 480,000- 425,000 years ago, which pushed the Thames south and the geology shows that it did so in Hertfordshire in three stages. First a spur of the ice sheet forced the river south east between Rickmansworth and Watford. The river looped past Harrow and rejoined its old north easterly valley at Ware. Then another ice spur pushed the Thames south towards St Albans and Finchley and finally the old course was blocked completely and the Thames backed up until it broke through the south- west Chilterns near Reading and formed its modern easterly course.

The ice covered the eroded chalk hills and valleys with boulder clay. The gravel in the glacial clay could have come from well to the north- in Derbyshire, Yorkshire or Durham. The Lea forms the eastern border with Essex. The Lea and Colne were originally formed by melt-waters from the Anglian ice sheet. Logically. rivers rising where these do might have flowed towards the Ancestral Thames. In the south of the county (the old county) most of the soils are water deposited and later from the Tertiary and Quaternary These were laid down since 66 MYA, which is since the mass extinction K Pg event, probably caused by a meteorite, which brought the Cretaceous period to an end. In the Tertiary and Quaternary periods land fossils may appear in the London Clays. Any fossil record in the chalk would have to be marine.

Much of Hertfordshire is now swallowed up by Greater London Some of the south flowing streams of the county- such as the Mimmshall Brook disappear underground down swallow holes into the chalk sub strata, and it is still not fully established where their waters emerge- the Lea? The Colne? or into the great London Aquifer which lies under the city. Anciently detached “islands” of Hertfordshire were seen to the west: such as that which contained Amersham and Coleshill in the Western Chilterns of modern Buckinghamshire.

KENT

Perhaps the most important aspect of Kent is that it well illustrates how all periods , eras, epochs of geology are, with a few exceptions , represented in the structure of a given region. Here is a county largely Cretaceous with Tertiary and Quaternary later drift, but the Kent Coalfield shows that the Carboniferous period is represented at a deep level and between the coals below and the chalk above- presumably all intermediary periods are to be found. Superficially, however, a county is described in terms of surface geology.

Kent, geologically, is the broken eastern section of the Weald-Artois Anticline in England. Here, 12-10,000 years ago, the Straits of Dover broke through as the Devensian Ice Age ended. The northern buttress of the anticline is the North Downs which channels the Modern Thames eastwards to the sea. The south buttress is out of county– for the South Downs run out to sea at Beachy Head in Sussex. Between South Foreland at Folkestone and Beachy Head is an exposed cross section of the Weald. From Hastings west to Horsham in Sussex is the ridge of the High Weald. Here, in the centre of the anticline, Jurassic rocks- hard sandstones from circa 300-130 MYA rise to the surface. These more ancient rocks are the “Hastings Beds”. In the lowland of the Weald are sediments from shallow Post-Cretaceous seas which ebbed and flowed in the Quaternary period. Between the North Downs and the Greensand hills are gault clays and they, like the greensands, are Lower Cretaceous and a little older than the chalk; for as the Weald is an eroded dome, strata run back in time as one approaches the Jurassic centre. The chalk and greensand hills are both at their highest in the west- near Surrey- at Biggin Hill and Toys Hill repectively.

In the north and south-west of the county are aluvia from the Thames & from the Rother-Limona system, the estuary of which has largely retreated to form Romney & Walland Marshes. The Thames was diverted to the northern border of the county in recent times, by the Anglian Ice Age- previously it had followed the Chilterns and crossed East Anglia- thence running north to join the Rhine.

The Wantsum Channel formerly divided Thanet from the mainland of Kent. In this channel Sandwich and Richborough were islands and Reculver was a headland on its north western end. This channel silted, and with it went the port of Canterbury: Fordwich. This silting was probably inevitable and a post glacial adjustment – perhaps the Wantsum channel had been carved out at its northern end by the deluge which formed the Straits of Dover, and ever since that one-off event it was silting and dying. A similar silting of the Rother, along with evidence of five ancient terraces of the Stour found at higher levels in Blean- suggest that there may be some tectonic change in Kent- and this seems contrary to the general geology of the South of England– where the land sinks as a corollary of isostatic rebound in the north (itself caused by the lifting of the weight of the ice sheet). The Medway divides the county geographically and culturally. In the west are Cob plantations, Filberts and a Surrey-like landscape with wooded dales. In the east are hop gardens, extensive orchards and sheep grazing on the littoral lands., which are treeless. Rochester, Maidstone, Teston and Yalding are the main places where, throughout time, the river has been forded or bridged. The other rivers which pierce the North Downs are the Darent and Stour.

On the Greensand hills (Lower Cretaceous) of West Kent, rag stone was quarried. This lies in bands with hassock or rotten stone strata between them. The escarped hills inland from Romney Marsh are the eastern end of the Greensand, and the former coastline. North of the Downs, the London clays and muds have long been used for brick making and pottery, and the whole region from Faversham to Grain is rich in brick pits and kiln sites going back to Roman times. These diggings are so extensive that they have changed the shape of the North Kent coast and estuaries. It is a man made landscaping only rivalled by the Norfolk Broads- where peat was dug. Ptolemy mapped Kent in Roman times. The two most extraordinary features of the county’s coast are the Street at Whitsable (man made or natural?) and Dungeness- technically containing the only desert on the island of Great Britain.

NORTHAMPTONSHIRE

This county is of great importance as a water-shed and many of the great rivers of the Midlands and Southern England find their sources here. The County is almost entirely Jurassic in its solid geology and so another particular marker of this region is that it is the unlike all counties to the south, south-east and east in not having any chalk and being without that crescent of Cretaceous strata which either show on the surface or underlie the Tertiary and Quaternary deposits of those neighbouring counties.

The watershed is that from which run the Warwickshire Avon, the Nene, Welland and tributaries of the Ouse and certain south flowing rivers such as the Cherwell ( a tributary of the Thames).

All the rocks of Northamptonshire are sedimentary, and were thus laid down under water- by sea, estuary or river. The rocks are Jurassic, being between 200 and 130 million years old. During this period the land was periodically submerged and uplifted- sea levels rose and fell and so there are multiple strata.

The Northamptonshire Heights are part of the greater limestone system which stretches from the North Yorkshire Moors to the Jurassic coast of Dorset. The Northamptonshire Heights are essentially “Cotswold” in manner and are of oolithic limestone: which signifies that the grain of the rock has an “egg-like” form. Metamorphic and igneous rocks are to be found in the county as pebbles and rocks within the drift material of the glacial ages. The Devensian (last ice age) almost certainly missed the county as its ice front was to the north: on a rough line from Glamorgan to Flamborough. The middle ice event- the Wolstonian- is more ambiguous because the southern limit of the ice, as indicated by the village-name of the event, was in the Warwickshire village of Wolston near Coventry. Thus Northampton must have been either under, on or extremely close to the ice front. The Anglian Great Ice Age would have covered the county although that ice front also erratic and can be found from South Essex across the Hertfordshire hills but excluding the Dunstable Chilterns. Thus the general movement of travel, of this ice stream, seems to have been north-east to south west, as evidenced from the alignment of the boulder clay band through Suffolk. Much of the county is covered with rock debris deposited during the Great Ice Age. The River Nene has a very broad valley running east of Northampton which was probably caused by melt-water, whether at the limit of the ice or as the sheet retreated. Gravel pits indicate glacial drift deposits and infill in the undulating landscape by ice debris. Some of these run quite deep – in certain parts of the South Midlands and East of England, glacial drift has been found to be 300 ft thick.

Geologists tend to divide Northamptonshire into three parts:

Firstly, a hilly area in the south-west, which joins a ridge of hills from Daventry ending near Stamford. Here is the highest land. Arbury Hill is about 740ft, Borough Hill 100 ft lower at about 640ft; Honey Hill is 700ft. The hills slope away gently to the south and east and escarp to the north and west.

The second region is that of the hills which divide the River Nene from the Ouse. Both rivers flow east. This region is of modest height- no doubt eroded by the ice sheets of the Pleistocene.

The third area is the valley of the River Nene. The Nene rises at Hartwell Spring, on the north side of Arbury Hill. the rivers Ise, Harper’s Brook and Willow Brook are tributaries of the Nene.

The Ouse and Nene system roughly follows the course of an ancient river called the Bytham which included some of the Warwickshire Avon Valley. It ran across the Midlands and East Anglia to join the Ancestral Thames which had flowed north east along the Chilterns, along the region of the Waveney Valley, to the modern coast and turned north to join the Scheld-Rhine system which drained to the Arctic Ocean. The Severn in its southern flowing form was a consequence of the breaking of the Lapworth melt-water lake. That event not only reversed the flow of the Bytham- Avon system but also cut the Thames from its ancient tributaries which had been in Wales. The lack of Cretaceous material in Northamptonshire means that it was either scrapped away by the ice sheets or that those seas which laid down those Cretaceous strata came to an end to the south of Northamptonshire.

SUFFOLK

This is a classic county of glacial drift material overlaying the solid geology. In the south west the chalk of the Chilterns extends into the county and continues up through it to re-emerge as significant hills in the Lincolnshire Wolds. Here in the south west, on the Essex border land rises to about 400 ft. As this chalk land runs north it is covered with sands and forms the Brecklands which are heathy and subject to wind erosion. The sands are Quaternary, over the Cretaceous bed rock; that is: the chalk dates until 66 MYA in the Upper Cretaceous and the sands are after that 66 MYA date- which is also that of the K Pg Mass extinction- said to have been caused by a large meteorite strike in Yucatan. Bradon, on the chalk lands was the centre of a flint industry- not just in Paleolithic-Neolithic times, but recently where the silicone rock was napped for building.

The northern border of the county is the River Waveney and this runs roughly along the old course of the Thames, which formerly followed the Chilterns and this river then turned north, was joined by another ancient river the Bytham (roughly running along modern reaches of the Avon and Ouse. Together the Ancestral Thames-Bytham system joined the Scheld-Rhine. The Thames was diverted south by the Anglian Ice Sheet which also covered this county some 480,000- 425,000 years ago and reached its southern limit roughly along the line of the Crouch in Essex. The other two ice ages: The Wolstonian and Devensian did not cover Suffolk and so the Boulder Clay- of which the county is famous must have been deposited by the Anglian ice sheet.

The Boulder Clay runs in a belt across the county from north-east to south-west with sand an gravels to its east and so one sees belts across Suffolk which are consecutively Cretaceous, Pleistocene and Marine Post-Glacial.

Areas of alluvial London Clay are found and also Red Crag” of the Pliocene- which also appears at Walton in Essex, this is a recent sandstones, 12-1 million years old, laid down towards the end of the Tertiary period and earlier than the Ice Ages. They are fossil rich and laid down under water from debris washed from eroding Jurassic rocks. The fossils would be marine. It would be interesting to know if the London Clays of Suffolk were a remnant of the Ancestral Thames.

Suffolk provides the name to the warm interglacial Hoxnian stage, for the village of Hoxne is where evidence of these hominids of the Acheulean culture was found.

The Suffolk coast is dynamic. It erodes in places such as at Dunwich where a major mediaeval port has been lost- but it grows at Orford Ness where a spit of long-shore drift material stretched 10 miles south forcing rivers such as the Auld south towards the Orwell. This bank is entirley of the last 1000 years and thus would have been unknown in Roman or Saxon times.

The Southern border of Suffolk is the River Stour and this migrates rapidly for the county boundary with Essex follows an old course, often at variance with the modern river meanders.

The coast is, in the north east, characterised with heathland and conifers which cannot be endemic. This is the Sandlings region and here are decoys which may be dug specially for wild fowling or may be remnants of southern Broads formerly dug for peat or aggregate. A few waters south of the Norfolk border carry the name “Broad”. The large estuaries of the region: Stour, Deben, Orwell, Auld are not solely river formed but the consequence of land subsidence in the Pleisocene and Holocene allowing tidal waters to migrate inland. Oddly, in recent years, nuclear Power stations have been built on this eroding coast- as they were at Dungenesss in Kent. Near those at Sizewell is a region of marsh, lagoons and heath famous for wildlife- Minsmere.

SUSSEX

Sussex, like Kent, is within the Weald-Artois anticline but occupies the southern half of it with its northern border being the Wealden Ridge composed of Jurassic “Hastings Beds” of sandstone which lie across the centre of the anticline. This is an eroded dome with Chalk buttresses forming its edges: thus the age of strata from chalk, to gault, to upper greensand, lower greensand and Hastings beds go back in time as the centre is approached. The chalk and greensand is Cretaceous- the more ancient High Weald is Jurassic. Surrey occupied the northern half of this anticline. From Worthing West the Downs march inland west-north-west. On the flat littoral , which expands in width to the west and the Hampshire Border, there are shingles and other marine deposits. This region- centred about the Manhood Peninsula at Selsea, has been broken through and natural harbours formed at Chichester, Hayling, Bosham, Appledram and Pagham. Some of these silt up periodically– Pagham particularly- and the dynamics of the Sussex coast are complex and difficult to fathom: estuaries and inlets are blocked off by long-shire drift. Perhaps, counter-intuitively, rising sea levels allow silts and shingle to be deposited at higher levels and so sea-level rise and land increase can exist together (Barnstaple Bay in Devon is the text book example of this ). Pagham was drained, perhaps in Roman times, lost again in 1300, drained in 1876 and innundated again in 1911. The Pevensey Levels are another district where land consolidation seems to run counter to the general trends or erosion, land sinkage and sea level rise.

Longshire Drift runs east along the Sussex coast- forcing river mouths eastwards; but some of these rivers have been artificially channelled (the Adur at Shoreham and the Cuckmere). The Ouse at Seaford was blocked off by shingle in one night’s storm forcing the closure of the port and the establishment of a new one to the west at Newhaven.

West of the Adur the South Downs are wooded, east of that river they are bare and sheep grazed. Between the hill ridges the land is rich and clay filled but this cannot be glacial for neither the Anglian, Wolstonian nor the Devensian ice sheets covered this county. On the Wealden Ridge stone was quarried for roofing- known as Horsham slate. The Wealden Ridge has retained wooded remnants of the great Anderita Forest at Worth Forest, and St Leonard’s Forest. Ashdown Forest is, on the other hand, dominated by open scrub land. Generally Sussex is less wooded than Surrey to the north because the land is richer and more suitable for farming. The Downs rise to the west with their highest point at Butser Hill on the Sussex Hants border. They meet the sea at Beachy Head, which erodes quickly and reappear in France at Cap D’Alpreche where they then continue inland as the Haut Pays of Artois. Both the Cretaceous Downs and the Jurassic Ridge of Sussex were laid down under a sea. They were pushed up in relatively recent geological times- by the Alpine orogeny (mountain building event) about 50 MYA in the early Paleogene period of the Cenozoic era. It is strange to think of the Downs and Wealden Hills as distant edge ripples of the Alps.

In the east, no part of Romney or Walland are in Sussex but a smaller marsh called Gildeford Levels is in county. Here the estuary of the Rother has silted and a navigable waterway which used to run at least inland to Bodiam and north to Tenterden (Kent) is lost. Winchelsea and Rye at the river’s mouth were formerly islands, as was Pevensey to the west. There is a second Rother, also running west east in Sussex which meets the Arun: perhaps, in former times, the two rivers were confused by a geographer. It is interesting to speculate what route the Rother took before the destruction of the land bridge: did it run south to join the estuaries of the Test, Hampshire Avon, Canche and Somme, or north to merge with the Scheldte, Thames, Blackwater and Rhine. Whichever way it ran it must have had some effect with either melt-water from the north or sea level rise from the south in weakening that land bridge.

WILTSHIRE

This county which is generally seen as a typical Cretaceous chalk landscape , in fact is almost 50% Jurassic for north and west of the Vale of Pewsey the chalk and associated Cretaceous strata- Greensand and gault, has been eroded away leaving the Jurassic limestones on the surface. Here runs the Wiltshire Avon- that is the west flowing Avon, for the county has another Avon which flows south through Salisbury Plain, Amesbury Salisbury and on to Christchurch on the Hampshire Coast. The question must be: what removed the Cretaceous strata from the north west third of the county? Was it ice in the Anglian, Wolstonian or Devensian ice ages, or water from the Avon header streams? It may be instructive that this Cretaceous material is also missing in the Vale of Wardour to the south west so water seems most likely. But it is also interesting that both “borders” between Cretaceous and Jurassic are paralleled by faults- The Mere Fault in the south west and the Heywood Fault in the north. At the north western edge of the county the Jurassic rock is Oolite- like the Cotswolds- fine grained limestone with an egg like grain structure. Moving east from the oolite one finds Oxford and Kellaway Clays, the Corallian Sandstone, then Kimmeridge Clay. This meets the Gault which seems almost always to lie at the foot of a Cretaceous escarpment with thin bands of greensand about it and then the chalk which is the higher ground of south Wiltshire, Salisbury Plain. The land escarps to the north west- like an old coast line. Perhaps here SW-NE across Wiltshire one is seeing a chalk-cliff coast being eaten back by sea must as happens today in Sussex and Kent. The Chalk was raised up, as were other strata, by the Alpine orogeny of 50 MYA and so if there was a sea basin in North West Wiltshire, it dates from after that time. All the strata of Wiltshire are marine and if trhey are fossil bearing- that too must be marine. In the east of the county is a small region of London Clay and Reading beds and in the south east there are Bracklesham and Bagshott beds- these are late Tertiary or Quaternary deposits from a time when these regions were periodically washed by salt water, brackish water and fresh water estuaries and inlets.

In cross section and if flat, Wiltshire would show chalk on the top, then upper greensand, gault, Lower Greensand, then the Jurassic Clays, then the Oolithioc limestone, then Lias under the Oolite. If this strata tipped up to the north west and down to the south east one has a fairly good model for the solid geology of the county. To this model one needs to add the Tertiary deposits of the London Basin and Hampshire Basin to the eastern end. The Cretaceous rocks and strata are 130-66 MYA and the Jurassic perhaps 250-130 MYA. The highest point in the county is at the Tan and Milk Hill Ridge – Vale of Pewsey, which is just under 1000 ft

Above the Chalk are Sarcen Stones, these large slaps of field stone were used extensively by the builders of stone monuments such as Stonehenge and Avebury and a particularly fine field of them lies on the Marlborough Downs just north of the Avebury-Marlborough Road. Sarsen means “Saracen” but the implication is generally “Pagan”, with the buildings of the Chalk Down monuments seeming “Un Christian” to the people who coined the term. Sarsen stones are sandstone rocks found as field stone in quantity on the Marlborough Downs, Salisbury Plain and in Kent, Berkshire, Surrey, Essex, Oxfordshire, Dorset and Hampshire. They are the post-glacial remains of a cap of silcrete (snadstone glued together by silicone) that once covered South East England- but seems to break up and erode quickly- even more so than the Chalk. Perhaps the erosion of the Sarsen released silicone to form the layers of silicate flint in the Upper Cretaceous chalk. 

In the Marlborough region the escarpments step and so a lower one at Bremhill is followed to the south east by a higher one at Cliff Pypard and then to the south east an even higher on at Hackpen Hill. One might imagine a set of shorelines when waster flowed at three or more different levels in the north west of the county.