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The Geology of White Colne

 

This page gives a Detailed History of the Geology of White Colne.

 

To see a Brief History please click here.

 

 

Introduction

Taking a bird’s-eye view of White Colne at the beginning of the twenty first century, you would see a landscape that is primarily agricultural with a few small pockets of commercial development and the majority of the housing bordering the main road running east-west across the parish.  Other visible features would be the River Colne which forms the southern boundary, the smaller roads joining the village to Bures in the North and Colne Engaine to the West, parts of the disused railway line and St Andrew’s church, which stands about three quarters of a mile to the North East of the village.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

To understand how the landscape of this small part of Essex has evolved we need to go back many thousands of years when the environment was very different.

 

 

 

 

A quick geology lesson

 

The “hard” rocks underlying Essex date from over 350 million years ago and are now over 300 metres below ground level.   They are shales, mudstones and sandstones – relatively soft rocks in fact – laid down in the Silurian and Devonian periods.  Moving upwards, and forward in time about 250 million years into the Cretaceous period, the next layer is Gault, or marly clay, followed by sand deposits known as Upper Greensand.  There is no evidence in Essex of deposits made between the Devonian and middle Cretaceous periods.  

 

Rising sea levels in the later Cretaceous period created the chalk deposits which form the next layer.  This chalk layer is the oldest rock visible in Essex and forms a basin underlying the Thames Valley, counties to North and South of the river and the southern North Sea.  In our area of North Essex this chalk layer is still well below the surface. Eighty million years ago, moving through the Palaeocene period and into the Eocene, sea levels were falling again and a number of sedimentary layers (sand, clays and shell) were created.  The temperature rise during the Eocene period caused this area to be covered by sub-tropical seas, resulting about 50 million years ago in the deposition of a material many Essex gardeners are familiar with, London Clay.  It is this layer, exposed on the Essex coast, which yields many fossils.  Above the London Clay, the layers become more sandy - the Claygate Beds and Bagshot sand layers - although the latter has been mostly eroded. There is another gap here in the time line as rocks laid down in the following periods have also been eroded.

 

Jumping forward to the Pliocene, a mere two million years ago, a rock called Red Crag – in fact a red, iron-stained sand – appears.  This is visible in bands at Walton on the Naze and is another rich source of fossils.  The next time period, the Pleistocene, is also known as The Ice Age and is responsible for a number of commonly seen rocks, sands and gravels in Essex overall and in our part of the county. The ice sheet which covered this area and the actions of the River Thames, whose original route ran through Essex, were responsible for much of the exposed geology we see today.

 

During the early Ice Age, the Essex coastline did not exist as Britain was joined to the Continent, and at that stage the ice sheet did not extend as far south as Essex.  The River Thames flowed through Hertfordshire and Essex, merging with the River Medway to join the Rhine in what is now the North Sea. About 450,000 years ago during the most severe of the glacial periods, known as the Anglian Glaciation, the ice sheet extended further south into Essex and Hertfordshire and the course of the Thames changed to run more closely to its present position, before merging with the Medway near present day Southend.  

 

Superimposing these events onto a modern map, the key features for our area are the original route of the river flowing just to the South of Colchester and the ice sheet covering Essex as far South as Hornchurch.  The Thames, which was a much larger river than its current size, deposited large amounts of river gravels along its original course, some of the deposits originating from rocks in the Welsh mountains.  This is the source of much of the visible gravels covering Mid and North Essex which have been extensively worked over the years.  Also occurring in the gravel beds are puddingstones and sarcens, large boulders, sometimes seen as ancient waymarkers – one such stone was found in Earls Colne at the junction of Upper and Lower Holt Streets.

 

The ice sheet, expanding southwards over Essex during the Anglian Glaciation, brought with it extensive deposits of boulder clay containing rocks and fossils originating from the Midlands and Northern counties, gravels and flints.

 

It is these most recent layers which are commonly visible near the surface today.

 

 

Ice Age Essex and the River Thames

 

 

The following Essex County Council map shows the current geology of Essex.  Clearly visible are the large tracts of glacial tills (pale blue), sands and gravels (pink) and London clay (brown) with smaller accumulations of other types referred to in the text earlier.

 

The present day geology of Essex

Also clearly visible are the courses of the present day river systems which have eroded through the upper layer – the tills – to reveal the sands, gravels and clay beds beneath.  The course of the River Colne and its tributaries to the west of Colchester, can easily be identified for this reason.  

 

 

 

Taking a closer look at North Essex, the following map shows these three geological deposits present within the red circle which roughly locates White Colne.

 

Close-up on North Essex

 

 

So, taking a vertical cross section through White Colne would show a series of “rock” layers with the topmost eroded by the river to reveal older rocks beneath.  The following diagram is not to scale and is intended only as a summary of the above geological history.

 

Cross section through North Essex

 

 

 

At this time in our history we see the first evidence of man’s presence in the landscape.  To continue the story of the evolution of this part of Essex use the navigation buttons at the top of this page to go to the “People & Places” section.

 

We are fortunate to be part of the beautiful Colne Valley, formed by a small river which rises about 26 miles to the North West near the Essex/Suffolk border at Birdbrook and passes through the Hedinghams, Halstead, Earls Colne and Colchester to reach the sea between Brightlingsea and Mersea Island.  The northern limit of the parish lies just south of the county boundary formed by another river, the Stour.  The gently undulating landscape, typical of this part of Essex and Suffolk, is peaceful rather than dramatic.

 

In short, there is little to distinguish White Colne from numerous other small English rural communities.  But that does not mean it is without interest.  

 

The purpose of  this section is to give an understanding of the evolution of our natural landscape. In the People & Places section we develop this further, looking at the impact that we and our predecessors have had upon the landscape.  To begin, we need to fix White Colne on today’s map.

 

White Colne, Essex: Location

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

To understand how the landscape of this small part of Essex has evolved we need to go back many thousands of years when the environment was very different.

 

A quick geology lesson

The ‘hard’ rocks underlying Essex date from over 350 million years ago and are now over 300 metres below ground level.   They are shales, mudstones and sandstones – relatively soft rocks in fact – laid down in the Silurian and Devonian periods.  Moving upwards, and forward in time about 250 million years into the Cretaceous period, the next layer is Gault, or Marly Clay, followed by sand deposits known as Upper Greensand.  There is no evidence in Essex of deposits made between the Devonian and middle Cretaceous periods.  

 

Rising sea levels in the later Cretaceous period created the chalk deposits which form the next layer.  This chalk layer is the oldest rock visible in Essex and forms a basin underlying the Thames Valley, counties to North and South of the river, and the southern North Sea.  In our area of North Essex this chalk layer is still well below the surface. Eighty million years ago, moving through the Palaeocene period and into the Eocene, sea levels were falling again and a number of sedimentary layers (sand, clays and shell) were created.  The temperature rise during the Eocene period caused this area to be covered by sub-tropical seas, resulting about 50 million years ago in the deposition of a material many Essex gardeners are familiar with, London Clay.  It is this layer, exposed on the Essex coast, which yields many fossils.  Above the London Clay, the layers become more sandy - the Claygate Beds and Bagshot sand layers - although the latter has been mostly eroded. There is another gap here in the time line as rocks laid down in the following periods have also been eroded.

 

Jumping forward to the Pliocene, a mere two million years ago, a rock called Red Crag – in fact a red, iron-stained sand – appears.  This is visible in bands at Walton on the Naze and is another rich source of fossils.  The next time period, the Pleistocene, is also known as the Ice Age and is responsible for a number of commonly seen rocks, sands and gravels in Essex overall and in our part of the county. The ice sheet which covered this area and the actions of the River Thames, whose original route ran through Essex, were responsible for much of the exposed geology we see today.

 

During the early Ice Age, the Essex coastline did not exist as Britain was joined to the Continent, and at that stage the ice sheet did not extend as far south as Essex.  The River Thames flowed through Hertfordshire and Essex, merging with the River Medway to join the Rhine in what is now the North Sea. About 450,000 years ago during the most severe of the glacial periods, known as the Anglian Glaciation, the ice sheet extended further south into Essex and Hertfordshire and the course of the Thames changed to run more closely to its present position, before merging with the Medway near present day Southend.  

 

Superimposing these events onto a modern map, the key features for our area are the original route of the river flowing just to the South of Colchester and the ice sheet covering Essex as far South as Hornchurch.  The Thames, which was a much larger river than its current size, deposited large amounts of river gravels along its original course, some of the deposits originating from rocks in the Welsh mountains.  This is the source of much of the visible gravels covering Mid and North Essex which have been extensively worked over the years.  Also occurring in the gravel beds are puddingstones and sarsens, large boulders, sometimes seen as ancient waymarkers – one such stone was found in Earls Colne at the junction of Upper and Lower Holt Streets.

 

The ice sheet, expanding southwards over Essex during the Anglian Glaciation, brought with it extensive deposits of boulder clay containing rocks and fossils originating from the Midlands and Northern counties, gravels and flints.

 

It is these most recent layers which are commonly visible near the surface today.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ice Age Essex and the River Thames

The following Essex County Council map shows the current geology of Essex.  Clearly visible are the large tracts of glacial tills (pale blue), sands and gravels (pink) and London clay (brown) with smaller accumulations of other types referred to in the text earlier.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The present day geology of Essex

Also clearly visible are the courses of the present day river systems which have eroded through the upper layer – the tills – to reveal the sands, gravels and clay beds beneath.  The course of the River Colne and its tributaries to the west of Colchester, can easily be identified for this reason.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Taking a closer look at North Essex, the following map shows these three geological deposits present within the red circle which roughly locates White Colne.

 

Close-up on North Essex

So, taking a vertical cross section through White Colne would show a series of “rock” layers with the topmost eroded by the river to reveal older rocks beneath.  The following diagram is not to scale and is intended only as a summary of the above geological history.

 

Cross section through North Essex

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

At this point in our history we see the first evidence of man’s presence in the landscape.

 

To continue the story of the evolution of this part of Essex, click here to go to the ‘People and Places’ section.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

At this time in our history we see the first evidence of man’s presence in the landscape.  

 

To continue the story of the evolution of this part of Essex use the navigation buttons at the top left of this page to go to the

“People & Places” section.

 

 

 

Pleistocene

 

 

 

 

 

Eocene

 

 

Palaeocene

 

 

 

 

 

Cretaceous

 

 

 

Silurian/Devonian

Anglian  Glaciation

 

Ice Age

 450,000

 

 2 million

 

 

 

 

 

 80 million

 

 

 

 

 

 

 100 million

 

 

 

 

 350 million

 

 

 

Boulder clay/Glacial tills

Sand & Gravels

London Clay

Sedimentary becs/sands

Chalk

Upper Greensand

Gault

Shales & Mudstones

 

Alluvial Deposits

Sand & Gravels

Brickearths & Loams

Glacial Tills

Claygate & Bagshot Beds

London Clay

Lambeth Group

Upper Chalk

Solid & Drift Geology

of Essex

 

Extent of Ice

Sheet

 

Course of River

Thames

 

Pre Ice Age

 

Post Ice Age

Glacial Tills

Sand & Gravels

London Clay

Relevant Geology in White Colne

    Years Ago              Period