Clicky Cuckfield

CUCKFIELD

5.1 Introduction

Cuckfield can be found just west of Haywards Heath in West Sussex. It has generated much interest among Wealden workers as an important source of Wealden vertebrate material ever since Dr. Gideon Mantell began investigating its late Valanginian sandstone quarries in the early part of the last century. Unfortunately this interest is currently somewhat frustrated because its quarries have all now been abandoned and reclaimed as farm or recreation land. It is therefore not possible to re-examine the sedimentary context of existing finds or recover more fossil material.
Reference to Mantell’s personal journal (Curwen, 1940) reveals that he first visited Cuckfield as early as 1819 so that he might visit its quarries and inspect a collection of fossil material recovered from them. Impressed by what he saw he subsequently negotiated an agreement with the quarry workers that any new fossil finds they made would be sent to him. Mantell further supplemented his Cuckfield collection by occasional personal visits. One such visit in 1822 resulted in the discovery by his wife (Mantell, 1822 and 1833) of some unique teeth. These teeth were later given the name Iguanodon (Mantell, 1825), which of course was later to become one of the founding members of Professor Sir Richard Owen’s Dinosauria (Owen, 1842).

Figure 5.1. Geological map of Cuckfield (after Gallois and Worssam, 1993).

Figure 5.2. Whiteman’s Green quarry as it looked in 1820 (after Mantell, 1851).

The most likely source of these teeth and perhaps the majority of Mantell’s Cuckfield collection was the main Cuckfield quarry, which was located in the north of the village at Whiteman’s Green (Fig. 5.1). In some of his publications Mantell made use of an illustration of this quarry as it looked in 1820 (Mantell, 1827, 1833 and 1851) (Fig. 5.2). Having observed that in the background of the sketch the spire of the church at Cuckfield (TQ 303 245) is shown aligned with Ditchling Beacon in the far distance, Gallois and Worssam (1993) suggested that the sketch was probably of the southeast corner of the quarry (TQ 301 253). Gallois and Worssam (1993) also presented a composite section for the quarry based on several of Mantell’s descriptions (Mantell, 1822, 1833 and 1851):

                                                            Thickness (m)

SOIL AND SUBSOIL                         Loam up to 2.1

CUCKFIELD PEBBLE BED               Variously described as ‘diluvial aggregate’ or
                                                             ‘coarse pebble bed’ with bones up to 1.8 

CUCKFIELD STONE                         Softer sandstone, thin beds of Tilgate Stone,
                                                             freshwater molluscs, channel lag locally at base up to 2.4
                                                             Harder sandstone, Tilgate Stone more heavily
                                                             developed, channel lag locally at base up to 2.8

LOWER GRINSTEAD CLAY             Clay or marl with a few bones and freshwater
                                                             molluscs up to 5.2 seen

Having noted the nature of the attached matrix, Gallois and Worssam (1993) suggested that most of the fossils in Mantell’s Cuckfield collection came from the channel-fill sediments making up the bulk of the Cuckfield Stone and the rest came form either the Cuckfield Pebble Bed or the channel lags in the Cuckfield Stone.

However it should be noted that the source of Mantell’s Cuckfield collection is not quite as clear cut as described above. There were in fact many small quarries in and around Cuckfield and some of these were in the Ardingly Sandstone (Gallois and Worssam, 1993) (Fig. 5.1). It is therefore entirely possible that some of Mantell’s Cuckfield collection came from this stratigraphically lower unit. However this should not have much of a bearing on the taphonomic analysis presented in this chapter because bones from both units will have been subject to the same taphonomic processes. This is because both units are composed of fluvial deposits, representing times when the Weald outwash plain was more extensive, the Ardingly Sandstone forming the upper part of the Lower Tunbridge Wells Sand and the Cuckfield Stone representing a somewhat temporary return of the outwash plain in the Grinstead Clay lagoon.

It is also of note here that there is a great deal of material collected by Mantell recorded in museum catalogues simply as having come from Tilgate Forest. It is highly likely that all of this came from Cuckfield (S.D. Chapman, pers. comm.). The fact that this has not been specifically recorded may reflect the fact that in his publications Mantell was habitually no more specific, perhaps because he did not consider it necessary. By saying that his fossils had come from Tilgate Forest Mantell was actually being quite specific about the stratigraphic unit and area they had come from. The strata exposed in the quarry at Whiteman’s Green were collectively referred to by Mantell as ‘Strata of Tilgate Forest’. The then known extent of these strata stretched north from Cuckfield only as far as East Grinstead to the east and Horsham to the west, corresponding roughly to the area of St. Leonard’s and Tilgate Forests (Mantell, 1827 and 1833) (Fig. 5.3). However, despite all this, it was decided that the taphonomic analysis presented in this chapter should be based only on material actually recorded as having come from Cuckfield (588 specimens in total, although only 249 of these were actually examined taphonomically (Appendix A)).

Figure 5.3. Geological map of southeast England showing the locations of Cuckfield and St. Leonard’s and Tilgate Forests (after Mantell, 1833).

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5.2 The Cuckfield taphonomic analysis and its interpretation

 Before proceeding there are a few points that should be made. Firstly, the Cuckfield sample and indeed all the other samples analysed in the course of this research, except notably the Hypsilophodon Bed sample, represent attritional assemblages. This means that they accumulated over some period of time rather than their accumulation having been the result of a single event. If the latter had been responsible then a more uniform degree of taphonomic modification might have been expected in each case. Since they are attritional assemblages the reality, as will be seen, is a certain amount of variation, although with a tendency towards to an ‘average’ that is indicative of the physical environment represented. Identifying that ‘average’ will be the basis of any interpretations made of each of the analyses presented. However, and this is the second point, those interpretations will be made on a comparative basis. The interpretations of the analysis presented here for Cuckfield will therefore be somewhat limited because there is nothing as yet with which to make comparisons. Only when the analyses carried out for other sites have been presented will it be possible to put the Cuckfield analysis into context and properly interpret it. Thirdly, it should be noted that some specimens could not be used for some of the analyses presented in this chapter. Possible reasons for this, among others, included attached matrix preventing the taking of dimensional measurements and obscuring bone surfaces. Finally, all the raw data on which the analyses in this chapter are based is in Appendix A.

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5.2.1 Faunal composition

Ignoring specimens that could not be allocated to one of the chosen taxonomic groups, the total sample consisted of 575 specimens. The relative representation of each of the taxonomic groups in this sample is illustrated below in a bar chart, which has the aquatic and semi-aquatic groups (ichthyosaurs, plesiosaurs, turtles and crocodiles) towards the left-hand end and the terrestrial groups (large ornithopods (Iguanodon), small ornithopods, pachycephalosaurs, nodosaurids, stegosaurs, sauropods, large theropods and small theropods) towards the right, with pterosaurs at the far end (Fig. 5.4).

Most of the taxonomic groups are represented in the sample. Large ornithopods dominate (29.2%), reflecting the importance generally of Iguanodon in Wealden faunas, closely followed by crocodiles (23.3%), turtles (15.7%) and large theropods (14.4%). Terrestrial groups are well represented and in fact account for 52.2% of the sample, thus making the fauna distinctly terrestrial in character since aquatic and semi-aquatic groups account for only 44.7% of the sample.

The faunal composition indicated by this analysis should be no surprise given that the fossils were recovered from channel deposits. As well as the remains of the crocodiles and turtles that lived in and around the channels there would have been an input of the bones of the terrestrial groups that inhabited the neighbouring floodplain.

Figure 5.4. Faunal composition of the Cuckfield sample (n = 575).

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5.2.2 Attached matrix

Of the specimens examined only 188 were found to have matrix attached to them. Of those, 4 had two types of matrix attached to them and were therefore ignored in this analysis because they would have complicated the bar chart presented below (Fig. 5.5).

Figure 5.5. Grain sizes of attached matrix in the Cuckfield sample (n = 184).

All classes of grain size are represented in the sample but the majority of specimens (82.6%) have silt attached to them. This confirms the observation made by Gallois and Worssam (1993). Of the bones recovered from the channel deposits quarried at Cuckfield it would seem that a small proportion, those with grit attached to them, ended up in the channel lags deposited in the deepest, fastest flowing parts of the channels. However the majority of the bones recovered, those with silt attached to them, ended up in channel-fill sediments.

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5.2.3 Fragmentation

The pre-fossilisation fragmentation of all but one of the specimens examined could be properly assessed. The relative representation in the sample of each of the four stages of fragmentation is illustrated in the first of the three bar charts presented below (Fig. 5.6). It shows that although 43.5% of the sample shows no fragmentation at all the remainder, in successively smaller proportions, can be allocated to stages 1 through to 3.

Figure 5.6. Pre-fossilisation fragmentation in the Cuckfield sample (n = 248).

A
Figure 5.7. A, trampling fragmentation in the Cuckfield sample (n =244). B, transport fragmentation in the Cuckfield sample (n = 244).

The other two bar charts break the pre-fossilisation fragmentation of 244 of the specimens examined, the total for which it was actually possible, down into trampling (Fig. 5.7A) and transport (Fig. 5.7B) fragmentation. The pattern of trampling fragmentation displayed would appear to be much the same as that seen for pre-fossilisation fragmentation as a whole and consequently the bar chart for transport fragmentation indicates that only 3.7% of the sample shows signs of having been broken during transport. Ignoring the possibility, as discussed in the previous chapter, that the transport fragmentation has been underestimated, it would seem that transport fragmentation was insignificant, with most fragmentation being attributable to trampling. The current velocities in the channels at Cuckfield can not have been high enough for much transport fragmentation to have occurred.

The next question to ask is whether the same pattern of trampling fragmentation is seen for all bone volumes. To answer this question the sample must first be broken down by original volume, the volume of interest in this case. The ranges of original volume chosen for this purpose were logarithmic in nature since the bones examined ranged in volume from less than 1cc to greater than 10000cc. The bar chart below shows the relative proportions in each of the ranges of original volume of those specimens for which an original volume could actually be calculated, a total of 232 specimens (Fig. 5.8). It shows a reasonable spread across the volume ranges, which is a reflection of the fact that larger dinosaurs were well represented in the fauna at Cuckfield.

Figure 5.8. Original volumes in the Cuckfield sample (n = 232).

A B 
C

Figure 5.9. Trampling fragmentation in each of the ranges of original volume in the Cuckfield sample. A, <10cc (n = 73). B, <100cc (n = 47). C, <1000cc (n = 39). D, <10000cc (n = 59). E, >9999cc (n = 10).

To answer the original question, the bar charts above show the pattern of trampling fragmentation displayed in each of the ranges of original volume (Fig. 5.9). The total sample represented numbered only 228 specimens because trampling fragmentation could not be assessed for all the specimens for which it was also possible to calculate an original volume. What these bar charts show is that the pattern of trampling fragmentation is not the same for all bone volumes. For bones with volumes less than 10cc the dominant fragmentation stage is stage 1 (49.3%) (Fig. 5.9A). In the case of bones with volumes equal to or greater than 10cc but less than 100cc the largest proportion, but only just with 36.2 % of the sample, show no fragmentation at all (Fig. 5.9B). In the next volume range stage 0 clearly dominates (66.7%) (Fig. 5.9C). Much the same pattern of trampling fragmentation is seen in the next volume range (Fig. 5.9D). A trend of decreasing trampling fragmentation with increasing volume is therefore indicated, although in the final volume range, bones equal to or greater than 10000cc, this trend is reversed, perhaps only because the sample in this case numbered only 10 (Fig. 5.9E). This trend, as an answer to the discussion in the previous chapter on this subject, would suggest that smaller bones are more susceptible to trampling fragmentation because they are less robust than larger bones.

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5.2.4 Weathering

The weathering of all 249 of the Cuckfield specimens examined could be properly assessed and is presented in a bar chart below (Fig. 5.10). It shows that the majority of specimens (77.5%) show no signs of weathering at all. The remainder show varying degrees of weathering but none could be classified as greater than stage 2.

Again the question is whether this same pattern of weathering is seen for all bone volumes. A set of bar charts presented below show the pattern of weathering displayed by bones in each of the previously specified ranges of original volume, this again being the volume of interest (Fig. 5.11). In this case the total sample was 232 bones, in other words all the bones for which an original volume could be calculated since the weathering, in contrast to the trampling fragmentation, of every single one could be properly assessed. The bar charts reveal that the same pattern of weathering is not seen for all bone volumes. The pattern displayed by bones with volumes less than 10cc is similar to that seen in the bar chart for the entire sample. However in this case only 55.3% of the sample shows no weathering and there is therefore a greater proportion showing higher stages of weathering (Fig. 5.11A). In the next volume range less weathering is suggested and the pattern of weathering displayed is the closest to that seen for the entire sample (Fig. 5.11B). The trend of decreasing weathering with increasing volume is continued in the next volume range so that the weathering seen is significantly less than the weathering seen for the entire sample. In this case 92.3% of the sample shows no weathering and no bone could be classified as greater than stage 1 (Fig. 5.11C). The next two volume ranges also continue the trend so that in the case of bones with volumes equal to or greater than 10000cc all the bones show no weathering (Figs. 5.11D and E). Therefore, as suggested by Behrensmeyer (1978), it would appear that smaller bones are more susceptible to weathering, this being a reflection of their larger surface area to volume ratio.

Figure 5.10. Weathering in the Cuckfield sample (n = 249).

A
C

Figure 5.11. Weathering in each of the ranges of original volume in the Cuckfield sample. A, <10cc (n = 76). B, <100cc (n = 47). C, <1000cc (n = 39). D, <10000cc (n = 60). E, >9999cc (n = 10).

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5.2.5 Abrasion

The abrasion of all 249 of the Cuckfield specimens examined could be properly assessed and the resulting data is presented in the bar chart below (Fig. 5.12). The data is skewed towards minimal abrasion but the majority of the specimens (53%) are slightly abraded and can be classified as stage 0-1. No specimen could be classified as greater than stage 1-2.

Figure 5.12. Abrasion in the Cuckfield sample (n = 249).

Again the question is whether the same pattern of abrasion is seen for all volumes. In this case the volume of interest is the volume immediately prior to transport, found by correcting, as described in the previous chapter, for all fragmentation that occurred after transport began. The bar chart below illustrates the range of these pre-transport volumes in a sample of 227 specimens for which it was actually possible to calculate this volume (Fig. 5.13). It should be noted that the pattern of distribution is not terribly different to that seen in the bar chart for original volumes (Fig. 5.8), probably reflecting the fact that in the earlier analysis of pre-fossilisation fragmentation it was shown that 43.5% of the sample shows no evidence of fragmentation (fig 5.6).

Figure 5.13. Pre-transport volumes in the Cuckfield sample (n = 227).

The bar charts below illustrate the pattern of abrasion seen in each of the different volume ranges (Fig. 5.14). In this case the total sample was again 227 bones, in other words all the bones for which a pre-transport volume could be calculated since the abrasion of every single one could be properly assessed. The bar charts indicate that the pattern of abrasion seen is not the same for all bone volumes. Bones with volumes less than 10cc show greater abrasion than was seen in the bar chart for the entire sample. Although, as was seen for the entire sample, the majority (55.8%) of specimens show slight abrasion and no specimen can be classified as greater than stage 1-2, the data is not skewed towards minimal abrasion but instead is skewed towards higher stages of abrasion (Fig. 5.14A). With the step up to the next volume range the trend is towards less abrasion. In this volume range no specimen can be classified as greater than stage 1, an even greater proportion (66%) of specimens show slight abrasion, and the data is slightly skewed towards minimal abrasion (Fig. 5.14B). The trend continues in the next two volume ranges, in which the greatest proportion of specimens, 50 and 50.9% of the samples respectively, show no abrasion at all (Figs. 5.14C and D). In the largest volume range the trend is taken to an extreme, with 66.7% of the sample showing no abrasion at all and no specimen being classified as greater than stage 0-1 (Fig. 5.14E). As expected from previous discussions on the subject, the trend seen here suggests that with increasing volume there is less abrasion.

A B 
C D 

Figure 5.14. Abrasion in each of the ranges of pre-transport volume in the Cuckfield sample. A, <10cc (n = 77). B, <100cc (n = 47). C, <1000cc (n = 40). D, <10000cc (n = 57). E, >9999cc (n = 6).

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5.3 Summary

The taphonomic analysis presented in this chapter has defined the degree of taphonomic modification that might be expected for bones from Cuckfield. However until similar analyses have been presented for other sites it is not possible to say anything about the relative degree of modification seen. Only then will it be possible to make meaningful interpretations about the physical environment represented at Cuckfield. What has been confirmed are the trends that should be expected with an increase in bone volume. With increasing bone volume less fragmentation, weathering and abrasion should be expected because larger bones are respectively more robust, have a smaller surface area to volume ratio, and are less easily transported than smaller ones.

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