Bere Regis Village Geological History

The furthest that one can go back in tracing the history of a parish, is to the very creation of the earth, because this 8,312 acres of the earth's surface, now known as the parish of Bere Regis, is, of course, as old as the earth itself. This period of time between the formation of the earth and when man first appeared on the scene is the province of the geologist, and the number of years involved is so vast as to be incomprehensible in human terms, being measured in thousands of millions of years. It is perhaps ironic that this tremendous span of time and the far-reaching earth movements which occurred during it, although having had a more profound effect upon the appearance of the parish than anything man has done since, should receive the most cursory treatment in a parish history such as this. After all, men, women, trees, buildings and roads have come and gone over the years, often leaving no trace, but the topographical features such as Black Hill, Bere Down and the river valleys have remained virtually unchanged in outline for thousands of years. If one could somehow or other miraculously go back for a day to, say the year 2000 BC, there would be no man-made features or trees which one could locate from a present day knowledge of the parish, but the familiar outlines of Black Hill & Woodbury Hill would be clearly recognizable.

The Geologist derives his information from a study of the layers of rocks or materials of which the earth's crust is formed and is bale to determine not only how the layers were formed but at what period. Geologically there are three principal categories of materials - Igneous, Sedimentary & Metamorphic - but in the South of England we are concerned only with sedimentary materials, which are found in areas which have at some time been under the sea, and which have solidified from sediments deposited on the sea bed; they include sandstone, limestone, clay, chalk, sand and gravel. A map of the world of 500 million years ago would look very different from a modern map - many present day land areas would be seas and vice versa. This process of the uplift of some areas and the compensatory lowering of others was a continuous process, and many areas were alternately dry land and sea beds many times. Indeed, the process is still continuing, but so gradually as to be imperceptible even over a span of several hundred years.

Such an area was the greater part of England, and each time it became a sea bed a different type of material was deposited upon it. Consequently there are now layers of different materials lying one upon the other, some of them only a few feet thick, whilst others may be 1,000 feet (300 metres) or more. In addition to these large movements of the earth's crust, there were smaller wrinklings, forming alternating hill ranges and lower areas, and the action of the weather coupled with rigorous climatic changes, combined to erode away some of the upper layers particularly when they lay on the tops of the hill ranges, with the result that different materials occur on the surface in different parts of the country.

Some 100 million years ago this part of the world was experiencing a tropical climate, when the land was covered with dense jungle-like forests. In these condition large reptiles flourished and roamed the muddy expanses of land freshly raised from the sea, leaving fossilised skeletons and footprints which have been unearthed in modern times from the limestone beds at Lyme Regis, Swanage and elsewhere. In contrast to these tropical conditions there were a series of Ice Ages, the most recent ending only a few thousand years ago, when the artic ice cap reached as far south as the Thames valley. Although the ice cap itself did not extend as far as this parish, the climate was so cold as to preclude the growth of any vegetation, and the severe temperatures would have played a large part in rounding the contours of the chalk which is particularly susceptible to frost.

The last major uplift of land in the South of England left a large part of Dorset & Hampshire covered with the most recent Teritary deposits of gravel, sand and clay, lying on the second oldest layer, the chalk. Much of this top layer has since become eroded away, leaving the chalk exposed, and the line marking the edge of the remaining Teritary beds and the exposed chalk divides this parish in two, roughly from east to west (See Map below). The chalk layer at this point has a gentle slope downwards towards the south, disappearing beneath the Teritary beds but rising up again further south to re-emerge dramatically above them as the Purbeck Hills.

(Click to enlarge)

The Tertiary beds have therefore been eroded away from the higher levels of the coastal hill range and the central Dorset heights into the basin between. The Drawing below shows a south-north section through the parish at which point the northern limit of the Tertiary beds forms the northern slopes of Black Hill.

There are, of course, older layers underlying the chalk which appear on the surface further inland and at the coast - for instance the limestone beds at Portland & Swanage - but these beds are so far below the surface under this parish that they need not concern us. In the village, a hole would have to be over 1,000 feet (300 metres) deep before any thing other than chalk would be encountered. The same thing would apply on Black Hill, except that about 100 feet (30 metres) of gravel, sand & clay would have to be dug through before starting on the 1,000 feet of chalk. See Map below.

(Click to enlarge)

Although these differing materials have since become blanketed in a covering of soil, they make their presence felt on the surface in the type of vegetation which the overlying soil naturally supports and this is clearly evident in this parish where the northern part consists of the rolling chalk downs with a predominately grassy covering and where the southern part is covered by the characteristic heathland. Until a hundred years or so ago, little, if any, of the heathland was cultivated and the bracken and heather covered landscape extended to the line on the Geological Map (See Map 3 paragraphs above), covering large parts to the east and south of the village which are now well established farm land. In spite of this cultivation which is gradually reducing the heath areas, the presence of the immediately underlying Teritary beds is always apparent in the hedgerows where the indigenous bracken continues to thrive. The extent of the original heath area can therefore often be observed by this means.

There can be no doubt that Bere Regis itself is situated on the chalk, as when even a small trench is excavated, the earth seems to 'bleed' with white blood and the resulting wound remains for many weeks until grass heals the scar. Several Dorset villages occur on or near the junction of the chalk and the heath and this may be attributed to two reasons - firstly, a good supply of spring water frequently occurs in such situations and secondly, there are in close proximity two former vital building materials, chalk & clay, used in building cob walls. Actually, these two materials still form a vital part of the building industry, as they are the basic ingredients of cement.

River valleys occur in almost all types of geological strata and they have over the years been instrumental in carrying away the eroded materials to the sea, there to be deposited on the present-day ocean beds in a continuing cycle. In so doing the river valleys themselves have become gradually filled with deposits of gravel and alluvial soil, leaving now only a comparatively small stream to meander its way to the sea. All these rivers, even the very small ones, were formerly very much wider and deeper and their original width can be clearly seen in the level areas remaining on either side of them, marking the extent of the valley gravel or alluvial depositis.

There are two rivers within the Parish, the Bere Stream coming down through the chalk hills from Milton Abbas and reinforced by the springs at Roke Pond and the River Piddle running through the Piddle Valley from Alton Pancras. Both therefore, originate in the chalk area. After entering the heath belt they converge and join within the parish just above Hyde and continue as one to Poole Harbour via Wareham. These two rivers carve fertile valleys through the heath, causing Black Hill to be in effect an island of heathland and forming a large flat triangular area of alluvial soil in the angle where they join. Doddings, Chamberlaynes & Hyde House can be considered as marking the angles of this triangle.

During 1959 the British Petroleum Exploration Company (now BP) drilled a borehole in Bere Wood over a mile deep and the following is a summary of the borehole log:

Material
Depth
 
Chalk
0 - 1355
Upper Greensand & Gault Clay
1355 - 1544
Oxford Clay
1544 - 2192
Kellaways Beds
2192 - 2248
Cornbrash
2248 - 2269
Forest Marble
2269 - 2439
Fullers Earth
2439 - 2963
Inferior Oolite
2963 - 2993
Upper Lias
2993 - 3557
Middle Lias
3557 - 3900
Lower Lias
3900 - 4730
Rhaetic
4730 - 4816
Keuper
4816 - 5533

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