The Pen Pits; a Lithic Extraction Site, and Greensand Quarry.

by Jonathan Cox

These writings present collaborative research on: ceremonial and residential pits, pitted boundaries, and also the extraction and acquisition through quarrying, of chert for tool production and greensand for quern production respectively; with the intention being to lay down a new level of data on the archaeological heritage of Pen Ridge. Only sparse archaeological work has ever taken place at the Pen Pits, there has been no geomagnetic survey or soil coring, or any targeted test excavations to locate any possible settlement. Retrieve datable materials have been recorded over the years, but any artefact samples for analysis have since been lost. Consequently the quarry site at Pen Pits, where in the past up to 200,000 surface pits and depressions have been documented extending over an area of more than 700 hectares, remain a mystery.

Ceremonial and Residential Pits in the late Mesolithic.

In their earliest Mesolithic phase many of the pits on Pen Ridge may have initially been created to; ‘commemorate a community’s seasonal visit from their winter caves, to a summer camping ground. The tradition of digging and filling pits is enshrined with tribal lore and ideology, it was a process of creating and fixing history, easily achieved by a group of people coming together and digging and filling a pit. Pits were also created as an offering, burying material in pits in meaningful ways was part of a ceremony, and very often these pits were filled with fresh flint, pottery and bone. The pit phenomenon across Britain was widespread and there was also a trend towards more formal arrangements of pits for ceremony in the Neolithic period, and the recurrent use of many pit sites became common, pits were often dug on important sacred ground- and water and wet places played a very important part in religion in Britain.’ Francis Pryor. ‘Britain BC’.

We also know the earliest primitive Mesolithic people resided near rivers in rudimentary pits, usually fashioned from antlers of red deer, and used pits for their refuse. The limited excavation of the Pen Pits over the years has revealed there to be little trace of any wooden buildings on the site, the pits therefore cannot just be the surviving component of a settlement; at some point they must have been the major structural component of it. Furthermore it is hard to ignore some of the C-shaped and L-shaped alignments of circular pits as being purposefully arranged for residential use, however the domestic pits puzzle can only truly be solved by the discovery of hearths, which have never been recorded to date.  Interestingly the pits lie in close proximity not only to each other but also to what looks like an unenclosed platform settlement protected in part by the steep escarpments in the south-western corner of Pen Ridge.

Given the proximity of these hut circles which are terraced into the south-west corner, it is desirable to establish the true date of the quarrying activities, and since it is known that chert was used throughout the Mesolithic, Neolithic and Bronze Ages, a Mesolithic age seemed an attractive assumption given the nature of the broken chert on the ridge visible today in the rabbit and sheep exposures, of being more akin to small blade production. However lithic extraction sites of Bronze Age date and earlier have not often been recorded, despite the extraordinary concentration of visible sites dating from that period to be found across much of the southern Britain.

Finding the Chert.

In attempting to decipher how the regular and circular pits evolved, it is important to understand what is under the ground on Pen Ridge, the chert lay on top of the greensand stratum, and chert was much cherished by Stone-Age communities. On the ridge plateau a number of pits were created, exactly where the modern geological map of the south of Pen Ridge reveals the chert to be located. Indeed the scale and regularity of the pits on the ridge, along with the singular appearance which they present are unequalled in Britain, and to date there has never been any attempt to investigate the possibility of chert procurement on the Pen Ridge plateau. Yet chert formed an important component of early pre-historic lithic tools in Britain. Sources of available chert for pre-historic exploitation and chert procurement can even be traced back to the Late Upper Palaeolithic period around 14,000 years ago.

Clearly the earliest inhabitants of Britain quickly found the chert, probably because in a sparsely vegetated landscape it would have been more visible than in later times, when forests and deep soils covered the landscape. It is likely that the ceremonial and domestic activities that took place on Pen Ridge also helped in exposing the chert veins that lay just under the surface. The Mesolithic people appear to have found chert in Britain relatively soon after their arrival at least ten thousand years ago. Mesolithic chert microliths abound on numerous sites in South-West Britain. Numbers range in the hundreds on particular sites including Pen Ridge, indicating perhaps that loss was not a concern, since there was always an abundance of chert to be had, presumably from these well-known sources. Radiocarbon dating at sites all over Britain shows this kind of activity did take place in the Late Mesolithic period.

Methods of Extraction

The upper greensand collection on Pen Ridge is with Chert Beds, which are yellow/brown sands and sandstones with visible layers and lumps of a hard mineral called; nodules, these fragments are easy to work off by hand. However the chert beds also include layers of tabular Chert, which is the blue/grey variety that needed to be smashed up by stone pounders.  To locate the chert veins or seams, trenches were dug often as deep down as the hard stratum of greensand, then the quarrying of chert would commence along the alignments of these veins, extracting the nodular chert which broke up readily, but the more useful blue/grey tabular chert was quarried using a percussion method with stone hand tools, smashing the chert apart with stone pounders, likely procured from the greensand that lay more predominantly to the east side of the ridge.

Explaining the Regular and Circular Appearance.

It is likely the depressions now only visible on the east side of Pen Ridge today, do not reflect individual prehistoric pits or shafts, but are the product of a complex, multiphase sequence of intersecting pit or trench excavations, with accompanying spoil heaps and fill, representing different patterns or time periods of chert extraction, and from the late Bronze Age onwards greensand extraction. The chert-vein trench galleries of spoil and fill intersected and sunk back in overtime forming the ‘regular and circular’ pits naturally. The disturbed earth would sink along the lines of these trenches, giving the impression that individual pits had been dug proportionately in a neat line, when actually it was just the fill or refuse that had receded back into the ground along trench-lines that had been dug with an even width. Rain would saturate the overlapping trenches causing the soil to sink back into the ground, often creating near perfect circular shapes, and making it look like individual pits had been excavated in perfect symmetry to each other.  The continual procurement of chert on Pen Ridge over thousands of years had pockmarked the surface of the earth and created this pitted landscape which was entirely formed by a web of trenches and spoil heaps over a long period of time.

Chert Manufacturing and Uses.

Chert and Flint materials were in high demand for tools, weapons and building materials throughout the age of stone, chert was particularly good for small blade production. The lithic assemblages on Pen Ridge are dominated by unmodified flakes, blades, cores, and angular debris. Chert made fine hunting tools, like arrow-heads and spears. The use of Chert had been widespread since as early as the Mesolithic period; for making picks and a wide range of finely crafted daggers, scrapers, points, burins, axes and other tools, all based on the people’s skill at crafting fine flakes and blades from the stone. Chert is also similar to flint; in that the spark it emits can be used for starting fire.

Chert fragments have been found at locations where these objects were produced in what was one of the earliest manufacturing activities of people.  The Pen Pits are the largest example of a lithic extraction quarry in the country and likely produced a vast quantity of small stone tools extracted using stone pounders or hammer stones as mentioned. A good example of stone manufacturing that has been accurately accounted for are the ‘Grimes Graves’ near the Norfolk-Suffolk border, these are attributed as being Neolithic flint mines which continued to be used well into the Bronze and Iron ages.

It is said the medium-depth shafts at ‘Grimes Graves’ could yield as much as 60 tons of flint nodules, which could be brought to the surface and roughly worked into shape on site. The blank tools were then traded elsewhere for final polishing. It has been estimated that 60 tons of flint could have produced as many as 10,000 of the polished stone hand-axes, and although it was chert that was procured on Pen Ridge, the Pen Pits would likely have been capable of producing the same quantities as the ‘Grimes Graves’. Chert could also be used as building stone in walls and dwellings as irregular or dressed blocks. Local sources were from small pits and ploughing of fields. Furthermore loose sand has often been used for building sand, from numerous small pits. Cherty materials (gravelly sand) were used for construction of local tracks, and as local aggregates for primitive concrete and track-stone.

Chert Trade

By the Neolithic period the Harroway route associated with early tin trading, had become the most important east west route in southern Britain. It passes through the north side of Pen Ridge just under half a mile away from the pits site and this was an extremely important factor in the development of the Pen Pits, for the Harroway played an important role in generating trade over the centuries. Indeed the ridgeline to which Pen-Ridge belongs is the first greensand with chert ridge located west of the high chalk-lands of Wiltshire; and signifies the beginning of the vales of Somerset, an entirely different type of terrain altogether. That combined with the numerous fresh water springs that abound from the ridge; would have made it a very alluring site to settle and trade at.

The early habitation and ceremonial pits on Pen Ridge had grown to become a set of chert quarries on such a large scale and with such a capacity; for the greenstone base was slowly being exposed by the labour of an immense number of human hands through the centuries, and the chert trenches would certainly be capable of providing the local region with more stone tools than it could possibly have needed. Furthermore by trading to passers-by on the local Harroway route these early Britons exploited a ready-made market and successfully sustained their manufacturing industry. In fact the Harroways’ close proximity to the pits can be seen as vital in explaining how this site got so big, with up to 200,000 pits recorded. It may even have been the chert pits themselves that determined or indeed helped create the Harroway route from the very beginning as most Neolithic tracks were often formed naturally by repeated use.

Interpreting Previous Excavations.

The ploughing of fields for farmland is fast destroying archaeological sites all over the country and has been doing soon for many centuries. With this in mind, it is important to appreciate that the pits were more evident in the past, in fact topographer Sir Richard-Colt Hoare undertook excavations of these circular pits that lay so contiguous to each other (ca.1810), and observed, ‘some many thousand pits of a regular and circular form, and in every single one of them, the bed of greenstone was still found at the bottom of the sand, always at the very point where these ancient excavations terminated’. Back then Colt-Hoare was able to distinguish between the oldest pits with the greensand base intact and the newer ones where the greensand was quarried, he describes the older pits as being further back towards the centre or top of the flat plateau. The modern geological map confirms this to be true and shows that the chert lay predominantly in this area on top of the ridge. Colt-Hoare even wrote about how ploughing was already destroying the site already back then, and expressed his concern at how quickly the pits on top of the ridge were disappearing. These were the chert pits that were of the greatest antiquity and today (ca2015) they are no longer visible. For this reason the pits have been mistakenly interpreted as solely greensand quarry pits from the late Bronze Age onwards, for these are the only surviving pits visible that can still be seen in large clusters on the east side of the ridge today.

These early excavations were useful in that they revealed how initially the depth of each pit did not reach the stratum of greenstone, yet no satisfactory explanation could be found as to why the greensand lay intact. The trenches excavated amongst the many depressions in the 1800’s revealed that the pits in some cases were over two meters deep, with surface features that varied from isolated depressions up to 5 meters in diameter to larger, irregular depressions and debris heaps. Though many pits when excavated contained few artefacts, dense concentrations of debris are common just beneath the modern surface, and it is possible still to see some shallow depressions which are entirely filled with these deposits of flaking debris still today.    

Only recently has the study of archaeological chert begun; the reason for apparent disinterest in it may be that good contextualised assemblages were not available for study. The majority of chert in museum collections were derived from arable field walking projects, and even these were not recorded in any great details as to location, in many cases the name of a farm or even district sufficed for ‘find spot’. The situation has changed dramatically in recent years, as probably the largest assemblages of chert have been recovered, not only by field walking but also by excavation; all are covered by accurate location and in the case of excavations by site context and in many cases C14 dating.

The presence of an abundance of fractured chert lying on rabbit and sheep scrapes all over the ridge today has been exposed, had it not they’re original purpose may never have been revealed. Yet Colt-Hoare and later Pitt-Rivers who both had the same objective in the 1800’s albeit through limited excavations, to establish the purpose of the pits primarily, but also to try to accurately date them and if possible determine the method of extraction, but both failed to appreciate in their writings that the majority of the pits they examined were in fact dug into chert-bearing residual clays to extract chert. The presence of greensand had seemingly distracted them along with a lack of knowledge on lithic assemblages and the importance of chert primarily to Neolithic people whose ability with the material was remarkable.  

Greensand Extraction

The greensand on the plateau lies predominately to the east-side of the ridge. Previous archaeological excavations of the pits have uncovered, antler picks, various animal bones, large circular stones with a perforation in the centre, which were quern-stones and hand-stones for grinding a variety of materials. Fragments of ancient pottery and both bronze and iron objects have also been dug up from the pits. This is because the pits continued to be used throughout the Bronze-Age and beyond when gradually quarrying patterns shifted and ultimately by the Iron-Age the greenstone became the sole object of desire. The arrival of bronze technology had slowly replaced the need for stone as a tool or weapon, and as the chert pits on Pen Ridge became redundant;  a new use slowly evolved and larger open quarry pits for greenstone extraction were created, located more to the the east side of the ridge.

This shift is represented by different extraction techniques needed for hoisting out the bigger, heavier lumps of greenstone from its stratum beneath the chert, including larger and deeper open holes still excavated with hand tools, yet the original regular and circular Neolithic pits of ceremony and chert quarrying would remain etched into the land; shaping all the subsequent greenstone quarrying activities on the south-eastern part of the ridge for evermore. By the late Bronze-age it is likely only the greenstone was being quarried at the site; used for grinding querns and also later as building-stone for the Romans and Normans. However quarrying for the greenstone at Pen Pits was intermittent and on a smaller scale than had been the case during its Neolithic heyday, when the chert was procured continuously from Pen Ridge to supply the stone tool trade.

Bronze-Age Boundaries on Pen Ridge.

We also know Neolithic boundaries of circular pit alignments persisted through the bronze and iron ages, when these so called multiple-ditch systems often bounded areas in a wide range of settlement where, economic, political and religious activities took place. At Pen Ridge a manmade earthen boundary or a cross-ridge dyke can still be seen today towards the northern end; it runs east-west across the entire peninsula ending either side of the escarpment and is now almost entirely ploughed out on the flat part of the ridge. Natural boundaries from the Neolithic period such as watercourses and escarpments were often supplemented by artificial boundaries in the Bronze-Age. Yet it is often difficult to determine whether a particular boundary like this was used for defence, stock-herding or purely as a symbol, it likely served all of these functions to varying degrees at different times in its existence.

It is also likely an extensive field system dating to the early Bronze Age existed on the ridge plateau above a great willow forest, and that this linear earthwork would continue to influence not only the natural landscape but the social and economic landscape too; in an area that is known to be extremely busy during the Bronze-Age; with round barrow burials and beaker pottery burials occurring nearby at Whitesheet hill and Wincanton respectively. This boundary certainly lasted for many centuries as records show the bounds of Pen Parish in ‘Tudor times’ were marked in the north by this cross-ridge ditch. Indeed Pen Ridge grew to become an important boundary site, one where battles were fought by armies, yet it was the altered plateau landscape, scarred and cratered as it was, that made this pitted site so anciently famous and important, both as an imposing boundary junction and gateway into the forested vales.