I was much struck by an episode of the hit BBC TV series Walking with Dinosaurs which I watched on its release in 1999. As it opened, a huge dinosaur was shown standing in bright sunlight at the edge of a Jurassic lake, or shallow sea, its head scanning the waters. A voice-over (Kenneth Branagh) told us that this was in the neighbourhood of what’s now Oxford, and that the hunter was looking for its prey. But in relation to the last, we were being misdirected. All of a sudden, an even bigger dinosaur reared out of the water and snatched the one we had thought to be the ‘hunter’, dragging it down (so the sea was presumably not that shallow).
This was the context in which the geological raw material of the Oxford region was laid down. Oxford clay (from sea silt); limestone coral reefs (‘Corallian limestone’).
Later — after the globe had moved on its axis, continents had moved around a bit, and after water had been first locked in ice, and then (repeatedly) melted out of it — water drained through the region, riving through the land cover, incising valleys and layering them with broken stone: gravel. Successive discharges (over extremely long periods) carved diverse channels through landforms, creating a series of gravel terraces. Rivers might also carry silt, and in periods of lower discharge, this settled to form surface soil.
This kind of story about landscape formation was developed in broad outline, in Britain and Europe, between the late seventeenth and early nineteenth centuries, out of a combination of practical observation of soil and rocks by people who wanted to make use of them, and speculative interest in understanding formative processes on the part of scholars and others scientifically inclined. Robert Plot, in his 1677 Natural History of Oxfordshire, catalogued different soil and rock types discretely, but interest in the patterns in which they occurred was developing, to the point where Martin Lister could in 1684 already conceive of (though not yet execute) a geological map. (Plot, who was by then first keeper of the Ashmolean – in its early form, a science museum — edited the Royal Society’s Philosophical Transactions, in which Lister’s proposal appeared).
During the eighteenth century, ‘geology’ gained its name, and the respective contributions of volcanic and water action to the formation of landscape were debated. In the early nineteenth century, these theories were synthesised with the fruits of an increasingly broad range of empirical observation (aided by a good deal of cutting into the earth in the making of roads and canals).
Insofar as the Oxford region attracted close attention this was not so much because of its mineral resources as because it was a hive of scholarship. William Conybeare, who had studied there, author of a pioneering 1822 textbook on the geology of England and Wales, and mentor to William Buckland, Oxford’s first reader in geology, delivered a paper to the (London) Geological Society in 1829 ‘On the hydrographical basin of the Thames’. (Of course such a major river basin was bound to attract interest). Conybeare was especially interested in a debate as to whether valleys could have been formed by rivers such as those then visible, or whether it was necessary to posit more ‘violent’ flows in the past. On several grounds, he favoured the latter hypothesis. Had it not been for such violent action, he said, the Corallian limestone which narrows the floodplain south of Oxford – in the form of what he called ‘Oxford chain’ – might never have been breached, in which case the site of Oxford would have lain beneath a lake that would probably have drained into the Ouse.
John Phillips, nephew and protégé of renowned geological mapmaker William Smith, himself one of Buckland’s successors, and the first Oxford geologist to hold the title of professor, half a century later published a book-length Geology of Oxford and the Valley of the Thames, which drew on material he had given in lectures. Phillips profited from the extension and refinement of knowledge that had resulted from the launching of a government-sponsored Geological Survey of England and Wales, from 1833. He was especially preoccupied with using the geological record to illuminate the fossil record, and the reverse, using the collections in the Oxford Museum (the current Natural History Museum, which he helped to found). He had previously used its feeder collections, such as the comparative anatomy collection of Henry Acland (last encountered mapping the physical and social context of Oxford’s mid-century cholera epidemic).
Nineteenth-century geologists were commonly interested in base rocks and their interrelations with the fossil record (though also in gravels, inasmuch as they illuminated formative processes). In the twentieth century, more attention came to be directed towards more superficial deposits, and to their interaction with the archaeological record (archaeology gained scholarly definition later than geology: the name came in the 1840s, cf. geology 1750s; the first Oxford professors were appointed in the 1940s, cf. geology 1860).
Of course methods, and conclusions, have changed over time. In the 1920s Kenneth Sandford tried to date Oxford gravel terraces, in part from archaeological evidence, and in the process bestowed on them the names they still officially bear, including ‘Wolvercote’ and ‘Summertown-Radley’ (though his ‘Peartree Hill gravel’ seems to have gone the way of all rock). In the 1980s, Lambrick and Robinson argued (on the basis of Oxford-region studies) that more attention needed to be given to the effects of human action on the environment during the Holocene (post-glacial period). Conversion of woodland to pasture increased run-off, they suggested, initiating occasional flooding; meanwhile conversion to arable, when and where it happened, determined that rivers and floods, carried silt, producing ‘alluviation’. In 2010, Macklin, Jones and Lewin riposted, on the basis of accumulating Carbon 14, drift-ice and peat-bog data that this story needed rebalancing to give more weight to climate change. Changes in flooding, in their account, had less to do with ground-cover changes than with background temperature shifts. They argued also that it was not until the early middle ages (more precisely, from the tenth century) that farming – using ploughs, hay and manure — promoted significant alluviation.
Meanwhile, practical concern with flooding has stimulated modelling work on the exact distribution and depth of local gravel beds.
If the gross picture that arises from recent accounts – setting aside differences over mechanisms and timing — is one of increasingly significant human impacts on the formation of the rock and mud environment, evidence of historic small-scale interaction is all around us. The earth has been quarried for building stone – on display across colleges and other Oxford buildings; later increasingly for brick. Less obvious but often underfoot is evidence of removal of river pebbles (for cobble paving, as in Merton Street). Then there has been much quarrying for gravel, manifest in the various gravel-pit lakes to be found especially alongside the railway line which the gravel now supports: thus Wolvercote Lakes; Hinksey boating lake; Kennington ponds. Seepage from the gravel can now be seen as a nuisance, threatening some householders’ basements, but, in former times, scattered springs and subterranean watercourses running through water-friendly gravel supplied wells and pumps.
Read into the history, and it becomes ever clearer that the most basic and taken-for-granted features of the local physical setting embody, in direct ways, the effects of human actions over the course of centuries, as people have reshaped for their own multifarious purposes the mud, gravel and water constituents of the floodplain: channelling the waters; deepening the waters; cutting new routes for the waters; digging into earth and gravel to extract building material or to lay foundations, and then relocating that earth and gravel, as opportunity has presented itself, or to make other terrain more usable; levelling the land here and raising it up there.
Mark Davies’ and Catherine Robinson’s A Towpath Walk in Oxford provides lots of pointers, if it’s read with this theme in mind. For example, p. 21 ‘It was over Aristotle Bridge between 1849 and 1852 that thousands of tons of gravel were taken by tramway from Cabbage Hill (later to become Kingston Road) and Lark Hill (later to become Chalfont Road). The gravel was used for the construction of the Great Western Railway…The removal of the gravel bank [the destruction of these ‘hills’] cleared the way for the eventual development of this part of north Oxford’.
Run the history backwards in your mind’s eye and substantial chunks of land crumble away, resolving themselves back into chaotic assemblages of mud and gravel. The railway embankment is disassembled; the western edges of Jericho sink and becomes watery and flood-prone. The braided strands of the Thames sometimes gain, sometimes lose water, but what’s now its deepest course becomes shallower, and prone to dry up in summer. Christ Church meadow walks disappear back into the foundations of Christ Church, exposing the soggy Frideswide flood meadow. The fields of Medley, the urban-fringe parishes of St Thomas’ and St Ebbes are seamed with petty streams. Humanity clusters on larger and smaller gravel ‘islands’: scattered across north, central and parts of east Oxford, in Osney, Grandpont, and north eastern parts of Port Meadow. As time is put into reverse, the landscape becomes ever less made, ever more given; ever less analytically understood, ever more intimately known.
Still a long long long way back to the dinosaurs.
For photographs of Oxford’s layers, see The British Geological Society’s Geoindex map, and click on the camera icons at Wolvercote, Littlemore and Headington.
Modern articles cited are:
Kenneth Stuart Sandford,’ The River Gravels of the Oxford District’, Quarterly Journal of the Geological Society, 1924
M.A. Robinson and G.H. Lambrick, ‘Holocene Alluviation and Hydrology
in the Upper Thames Basin’, Nature, 1984
Mark G. Macklin, Anna F. Jones and John Lewin, ‘River Response to Rapid Holocene Environmental Change: Evidence and Explanation in British Catchments’, Quarternary Science Reviews 2010
See also a vivid and well illustrated talk by Bruce Levell on the geology of the region with special reference to Iffley.
Life in the Floodplain 
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