The River Otter: A Field Guide to the. Palaeolithic Landscape Picture of Otter Valley taken by Laura Basell (PRoSWeB)

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Palaeolithic Rivers of South-West Britain Project and the National Ice

1 The River Otter: A Field Guide to the Palaeolithic Landscape Picture of Otter Valley taken by Laura Basell (PRoSWeB) Produced by The Palaeolithic Rivers of South-West Britain Project and the National Ice Age Network Funded by the Aggregates Levy Sustainability Fund through English Heritage

2 A Field Guide to the Palaeolithic Landscape: The River Otter Written and prepared by The Palaeolithic Rivers of South-West Britain Project Introduction The Lower and Middle Palaeolithic is generally considered to have lasted from c. 700,000 years ago to c. 40,000 years ago, ending during the Devensian glaciation. At various times during this period Britain was still linked to mainland Europe with a landbridge stretching from Hull round to Eastbourne. During the Lower and Middle Palaeolithic Britain was sparsely, and probably only intermittently, inhabited by different forms of hominins (a type of pre-modern human): Homo heidelbergensis during the Lower Palaeolithic and then Homo Neanderthalensis during the Middle Palaeolithic. Most Lower and Middle Palaeolithic archaeology is found in river sediments and caves. Whilst cave archaeology is often easier for archaeologists to understand (artefacts are often found close to where they were originally discarded and sometimes clearly stratified), 80-90% of known Lower and Middle Palaeolithic archaeology (mainly stone tools) has been found within river sands and gravels. The archaeology of the river sediments, while sometimes difficult to interpret, is therefore important to our understanding of the Palaeolithic period. Like other areas of Britain the south-west region has many examples of this sort of archaeology, most notably the rich assemblage of Lower Palaeolithic artefacts from the gravels of the Axe River at Broom, on the Devon/Dorset border. One of the major aims of the Palaeolithic Rivers of South-West Britain (PRoSWeB) project is to record and date the terraces of the rivers Axe, Exe and Otter and evaluate their archaeological content and potential. Many sand and gravel quarries operate within river terrace sediments rich in Palaeolithic artefacts and the National Ice Age Network (NIAN) is working with the aggregates Finally: there is another Otter terrace gravel exposure to the west of the Budleigh Salterton Cricket Ground. A great place to go and look at both the bedrock geology and some of the higher level terraces in clear staircase form is between Ladram Bay and Beer Head on the coastal path.

3 12. Here it is possible to see across the River Tale (a small tributary of the Otter) to Taleford which is also built on terrace deposits. If you imagine the two patches of terrace to be joined up (but still respecting any higher contours and areas of land) it will give you an idea of the extent of the floodplain and the difference in the types of river valley landscapes in the past (remember that you can only do this with terraces that lie at an equal height above the floodplain). 13. This is a better location to join terraces across the valley (see point 12 above) to understand the changes that have occurred in the river valley landscape. 14. An opportunity to ask any further questions. Please note that the flint knapping demonstration will take place shortly after the walk finishes. There are additional displays about Palaeolithic archaeology, together with information about the more recent history of Ottery St Mary in the Heritage Display. Entrance is 2 per person, 1.50 per person for groups. Reference Whittow, J The Penguin Dictionary of Physical Geography (2 nd Edition). Penguin Books: London. Note The information in this guide is derived from a number of different sources including BGS map sheets and accompanying memoirs. PRoSWeB and NIAN would like to thank BGS for their assistance on this project. industry to establish a protocol for reporting nad identifying Palaeolithic finds uncovered during quarrying. This walk will follow some of the river terraces and the floodplain of the River Otter. We will discuss the formation of river terraces (see the Key Concepts section), processes of landscape change, and some of the techniques that are used to study rivers and their deposits. We will also discuss the archaeology of the Palaeolithic in the south-west region both during and after the walk. We hope that by the end of the walk you will have a better understanding of the Lower and Middle Palaeolithic period in the south-west, the River Otter landscape, and some of the techniques and methods used in the study of Palaeolithic geoarchaeology. Key terms This section includes some of the key terms and concepts used in this field guide (after Whittow 2000). Alluvium: The sediments deposited in river channels and floodplains by the flowing water of streams and rivers, including gravels, sands, clays and silts. The gravels and sand of floodplains (see below) and terraces (see below) have been commercially quarried for many years and this quarrying has often led to the discovery of Palaeolithic stone tools within the sediments. Anglian: The most extensive glaciation of the British Middle Pleistocene (the period between c. 780, ,000 BP), during which glacier ice came as far south as the Bristol Channel and what is now north London. Colluvium: Sediments deposited at the bottom of slopes, after being transported by gravitational forces. Devensian: The last glacial (see below) of the British Pleistocene, lasting between c. 70,000 10,000 years ago. Floodplain: The part of a river, next to the channel, over which the river flows during periods of flooding. The floodplain consists of alluvium (see above) and often includes palaeochannels (see above).

4 Glacial: Often more commonly referred to as an ice age, a glacial is a geological period of time during which the climate cooled significantly (a glacial is a cold phase) and Britain was at least partially covered in glacier ice. Glacial maximum: The largest extents achieved by glaciers (ice sheets) during a glacial period. Head: A mass of sand, gravel and clay produced by solifluction (see above) under periglacial conditions (see below) during the Pleistocene (see below). It is often found filling valley bottoms. Holocene: The current geological period, which started about 10,000 years ago, and which is characterised by generally warm (temperate) conditions. Interglacial: A geological period of time between two glacial periods when the climate warmed significantly (an interglacial is a temperate phase), and temperatures were similar to those of the present day. Ma/mya: million years/million years ago Palaeochannels: Abandoned river or stream channels that no longer carry water and which indicate older routes of the river. Periglacial: The area around the fringes of a glacier or ice-sheet. The ground surface is subjected to repeated freezing and thawing, and to distinctive processes such as solifluction (see below), while the underlying ground is permanently frozen. Pleistocene: A geological period which started about 1.6 million years ago and ended after the Devensian (see above) at 10,000 years ago (the start of the Holocene). It consists of a series of glacials and interglacials (see above). Solifluction: Literally soil flow or the slow movement of soils downslope. Periglacial processes (freeze and thaw) make the soil particles unstable and produce enough water to aid their movement downslope. Terrace: See Key Concepts. gravels in the drive. This indicates how some of the altitudinal differences between the terraces are very subtle. 8. Please note: this is private land and permission has been obtained for access on the day of the walk. Look at the sides of the path as you walk up the lane and note any changes in the level of the bedrock geology and the appearance of the superficial geology (the terrace gravels). What do you think is happening here? 9. Here head deposits are exposed in the sections and on the path. Compare these with the terrace deposits that can be seen elsewhere on the walk: it can be very difficult to distinguish them and often requires a detailed study of their structures to do so. 10. There is an old quarry (hence Sand pit copse ) to the south of the path. This quarry demonstrates the relatively small scale of many historic quarrying operations when compared to some of the industrial-scale quarrying we see today. To the north of the path the Otter sandstone is clearly visible in the section, with river terrace deposits overlying it. 11. Although not a very deep section of gravel this is one of the few exposed sections of terrace deposits associated with the Otter. As with all terraces, these landforms in the Otter valley have been eroded, and material from the terraces has been incorporated into the head deposits and the lower terraces. The junction between the Otter Sandstone and terrace gravels is clear here, but some of the gravel appears to have become incorporated into the top of the sandstone. This is due to cryoturbation (freeze-thaw) processes. The orientation of the pebbles also suggests freeze-thaw processes have been at work, although we must be careful of our interpretation here as there are other possible causes of this orientation, including tree roots. The clasts (pebbles) in the section are angular chert and flint derived from the Upper Greensand and Chalk, and rounded pebbles and cobbles which are mainly quartzite derived from the Budleigh Salterton Pebble Beds. Looking at the types of clasts helps us to understand where the river flowed during the Pleistocene.

5 floodplain. Across the river (on the eastern side of the valley), a further terrace fragment rises on which a large portion of Ottery St Mary is built. It is quite common for houses and settlements to be built on river terrace deposits (as they are elevated above the modern floodplain and therefore less susceptible to flooding). 3. Dropping down to the bridge over the River Otter, it is possible to see the present day river. It is not very big in comparison to the floodplain of the Otter, which is up to 500m wide in places! It is in fact known as a misfit stream, because it is disproportionate to the size of the valley it occupies. The Rivers Axe and Sid are similarly considered to be misfit streams. Their large valleys were probably formed in the Pleistocene by large quantities of glacial meltwater. The modern floodplain consists of clays, silts and sands (c. 1.3m), lying on top of chert and flint gravels. Examples of the gravels can be seen from the bridge in the gravel bar, which includes distinctive rounded cobbles derived from the Budleigh Salterton Pebble Beds. 4. Looking eastwards you can see Otter Sandstone (bedrock geology) exposed in a rather weathered section behind a house. Note there are no superficial deposits here, just made ground, on top of the solid rock. The Otter Sandstone is up to 210m thick and outcrops along the western side of the Sidmouth district. Fossil vertebrates including terrestrial reptile and amphibian remains have been found in these deposits, which are c. 230 mya. 5. Looking westwards at this point there is a good view of the different terrace fragments, which vary in height above the modern floodplain and are likely to be of different ages. 6. Standing on the bridge here, it is possible to see the modern (Holocene) alluvium and various palaeochannels (which can be seen as slight depressions in the floodplain surface). The dismantled railway should also be clear. Note that the large rise of land to the east is not a terrace but rather bedrock geology the Otter Sandstone. 7. Note the slight rise in the land onto a low terrace at this point, and as you walk up the Cadhay House path, the Key concepts River terrace development: river terraces are remnants of the former floodplain (see above) of a river that have been abandoned and left at a higher level as the river downcuts. The term terrace refers to both the landform (which has the appearance of a bench in profile) and to the alluvial deposits of the former floodplain (e.g. sands and gravels) which are laid down on the floodplain during periods of flooding. River downcutting (leading to the formation of terraces) appears to occur as a result of the glacial/interglacial climatic cycles of the Pleistocene: in simple terms: 1. Sea level fall (which occurs during glacial periods as large quantities of global seawater are locked up in ice sheets on the land) results in rivers re-adjusting their profile, as their ultimate destination point (the sea) is now lower and further away. This is achieved by downcutting and creating both a new, lower floodplain and a new terrace (abandoned at a higher level). 2. Sea level rise (which occurs at the start of an interglacial as the ice sheets melt and the water returns to the seas) results in sedimentation of the lowest reaches (i.e. near the coast) of the rivers new floodplain. 3. Uplift of the land (in response to the removal of sediment through erosion and the removal of the weight of ice) occurs gradually throughout each glacial interglacial cycle and the rising of the land means that there is a need for the river to cut down again during the next glacial: return to point 1 above). The many glacial/interglacial cycles of the Pleistocene often result in a series of altitudinally-separated terraces in river valleys: usually referred to as a terrace staircase. Where there are terraces at different heights above the floodplain (as in the Otter valley), the higher terraces are usually (but not always) older. Reworking of Palaeolithic artefacts: Palaeolithic artefacts such as stone tools are often found in terrace deposits which were formed in the Pleistocene. It is assumed that the artefacts were left by hominins on river banks, gravel bars, and other areas of the floodplain, and were then washed into the rivers during flooding episodes. The artefacts were later deposited along with the gravels and sands, and are

The majority of the walk is concerned with superficial geology (i.e. alluvium and colluvium, which are unconsolidated sediments) as opposed to bedrock geology (i.e. hard rocks such as granite).

6 The majority of the walk is concerned with superficial geology (i.e. alluvium and colluvium, which are unconsolidated sediments) as opposed to bedrock geology (i.e. hard rocks such as granite). General Points of interest Route map produced by L.S. Basell (PRoSWeB) using background geological data reproduced by permission of the British Geological Survey, Licence 2005/089 NERC and Digimap data licensed to Exeter University. All rights reserved. This map is copyright and not to be reproduced. Map of the walk therefore very rarely found in the place where they were discarded by the hominins. The purple areas on the map represent head deposits (see Key Terms). You can see that the small valleys which contain head run roughly perpendicular to the Otter valley, emphasizing that these small valleys were formed by streams draining the higher land (including the older terraces) into the Otter. The orange areas are river terraces (both the landform and the terrace deposits). On this map they are largely undifferentiated (i.e. not divided into separate terrace units), although there are terraces at a number of different heights in the Otter valley. During the walk look out for terraces at similar heights on either side of the river valley (i.e. on both sides of the river) paired terraces of similar heights (and therefore age) can give us valuable information about river valley evolution and change over time. The yellow areas are modern (Holocene) alluvial deposits. Former river channels (palaeochannels) can be seen in these deposits, and organic remains found in the palaeochannel deposits can be radiocarbon dated to provide detailed information about river channel movements across the current floodplain during the Holocene A head-choked valley with a tiny stream, which is a tributary of the River Otter. To the south of this point it is possible to see the break of slope of the terrace exposure on which the Salston Hotel is built. The land surface then drops down into the head choked valley where you are standing, and then rises to the north where there lies another terrace fragment. These head-choked valleys do not always have streams in them in the present day. Standing on another fragment of undifferentiated terrace in this field, and looking eastwards, it is possible to see a clear break of slope and a second, lower undifferentiated terrace, which then drops down onto modern (Holocene) alluvium and the River Otter. The terraces of the River Otter range in height from c. 10m to c. 100m above the present day Specific Observation Points (see numbers of the Walk Map)

Name. 4. The diagram below shows a soil profile formed in an area of granite bedrock. Four different soil horizons, A, B, C, and D, are shown.

Name. 4. The diagram below shows a soil profile formed in an area of granite bedrock. Four different soil horizons, A, B, C, and D, are shown. Name 1. In the cross section of the hill shown below, which rock units are probably most resistant to weathering? 4. The diagram below shows a soil profile formed in an area of granite bedrock. Four different