Megafossil plants from Suffolk: a review of the Pre-Pleistocene records

MEGAFOSSIL PLANTS FROM SUFFOLK: A REVIEW OF THE PRE-PLEISTOCENE RECORDS H U G H LANCE PEARSON*

The current literature on the palaeoflora of Suffolk is concerned mostly with sub-fossil remains of extant species from Pleistocene strata. Although superficial deposits of that age predominate in the county, older sedimentary rocks also outcrop here (see Table 1). Some of these pre-Pleistocene horizons have yielded megascopic fossils of extinct species of plants. This article summarises the existing accounts describing the Suffolk megafossil flora, and the intention is to present new records for this flora subsequently.

The bias towards the Pleistocene Period and the microflora (e.g. pollen, microscopic algae and spores) rather than the megafossil plants in the current literature is due to the predominance of superficial deposits of that age in the county and the greater abundance of microfossils. Although pollen and spores of land plants probably occur in the Palaeogene (Lower Cainozoic Era) of Suffolk, a study of the fossil microflora has only been carried out for the Neogene (Upper Cainozoic Era) at Orford (Andrew & West, 1977). A clay-containing deposit of the Coralline Crag near Raydon Hall Farm, Orford, yielded pollen assigned to conifers and angiosperms, including several genera now restricted to thermophilous ('warmth-loving') floras in North America and eastern Asia.

Megafossil plants of pre-Pleistocene age in Suffolk have mostly been obtained from the London Clay of the Eocene Epoch. The London Clay was deposited in a sea covering the southern North Sea basin and extending West to a shoreline running approximately from the Wash to the Isle of Portland (Davis & Elliott, 1958). Thus, fossils of land plants now found in the London Clay of Suffolk originally grew no nearer to the county than Cambridgeshire, or perhaps west Norfolk. Exposures of London Clay in England occur near to their northern limit in Suffolk, an inlier largely obscured by drift near Reedham, Norfolk, being the northernmost recorded (Chatwin, 1961). The number of London Clay exposures in the county is limited due to considerable erosion during mid-Cainozoic times (Carr, 1967) and by its burial beneath the Crags and other Pleistocene deposits. Davis and Elliott (1951), and George and Vincent (1976 a & b) list the main coastal and fluvial exposures of London Clay in Suffolk.

The most abundant megafossil plants from the London Clay are pieces of pyritised wood (Daniels, 1971), but these have not been examined as much as similar wood from the London Clay of Kent (Wilkinson, 1984). Permineralised wood is also found in Suffolk in calcified form, obtained either directly from the London Clay (Brett, 1956,1960) or apparently reworked from that horizon and redeposited in the Red Crag (Brett, 1972). Lower Eocene seeds and fruits have been recorded from the London Clay 'Basement Bed' in * The author will be a member of Emmanuel College, Emmanuel Street, Cambridge, CB2 3AP, for one year from September 1987.

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southern West Suffolk following their discovery in the early 19th Century by John Brown of Stanway, Essex, in calcareous nodules at Assington, near Sudbury (Bowerbank, 1840; Reid & Chandler, 1933).

Fossil plants have rarely been recorded in Suffolk from Cainozoic deposits other than the London Clay. Clarke (1838, p. 373) made a brief reference to 'vegetable impressions' in 'plastic clay' at one of the Brick-Kiln pits near the junction of the Rivers Brett and Stour at Higham, near East Bergholt. These megafossil plants were found beneath the London Clay and apparently come from the Reading Beds of Upper Palaeocene age (Crane, 1981). Reid (1890) mentioned fossil wood from the Pliocene Coralline Crag near Sudbourne, but this may have been reworked from an older Stratum. In neither of these instances were identifications, descriptions or illustrations of these Cainozoic plants supplied, and they remain of little value. The following tables offer a summary of the Palaeogene megafossil flora of Suffolk.

Comments on Tables 2 & 3 The specific epithets of Mimosites brownianus and Iodes davisii are here amended to agree with the International Code of Botanical Nomenclature.

The new combination Cercidiphylloxylon spenceri (Brett) Pearson is made for the taxonomic reasons given below, and some of the published details for certain of the entries in Table 3 are corrected. C. spenceri was first collected from the London Clay exposed on the north bank of the River Orwell at Bridge Wood, near Alnesbourne Priory, Nacton (Spencer, 1966) and not from Bawdsey (Brett, 1956). Some microscope slides of Platanus and Plataninium described by Brett (1972) are registered at the British Museum

Table 1.

Outline stratigraphy of pre-Pleistocene rocks exposed in Suffolk. (see Anderton et al. 1979; Chatwin, 1961; Ranson in Simpson 1982 for further details)

Era

Period/System

Epoch/Stage

Member/Formation

Neogene

Pliocene Miocene

Red Crag Coralline Crag Boxstones

Cainozoic Palaeogene

Mesozoic

Cretaceous (Upper)

Oligocene Eocene Palaeocene

Absent London Clay Reading Beds Thanet Beds

Senonian Turonian Cenomanian

Upper Chalk Middle Chalk Lower Chalk

Note: The terms Palaeogene and Neogene are equivalent to the Lower and Upper Tertiary respectively. There is much debate over the precise Neogene/Pleistocene boundary in relation to the Red Crag (West, 1977), and similarly over the Palaeocene/Eocene age for the Reading Beds (Collinson, 1983).

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(Natural History) as having come from the Red Crag at Waldringfield rather than from the same Stratum at nearby Woodbridge. Some of these slides also bear older labelling stating the specimens' provenance as 'Waldringfield, Woodbridge', while certain others of the same have 'Woodbridge' only.

Since all of these are so similar, I assume here that they all were obtained from Waldringfield rather than Woodbridge.

All of the families mentioned in these tables include some living species, but only the genera Iodes, Oncoba, Platanus (plane) and Vitis (grapevine) as listed are extant. All of the named species are extinct. It should be borne in mind, however, that some of the extinct genera listed here are form-genera, e.g. Carpolithes, Cercidiphylloxylon, 'Myrtospermum'.

As such they are generally lacking in sufficient preserved characters for them to be assigned to better defined and more completely described genera, living or fossil. Thus, for example, Quercinium compares in its wood anatomy not only with extant oaks (Quercus) but also with certain other genera of Fagaceae (Brett, 1960).

Since living genera and species of plants can be characterised using observations of their complete bodies of intact Organs, it is often necessary with the fragmentary fossils of larger plants to use form-generic nomenclature to reflect this uncertainty in affinity, especially when making comparisons with extant genera and species. Consequently, some or all of the apparently extinct form-genera listed in Tables 2 and 3 may have belonged to living genera, (particularly the woods listed in Table 3).

The wood from Nacton, originally identified and named by Brett (1956) as Cercidiphyllum spenceri, is here transferred to the form-genus Cercidiphylloxylon Prakash, Brezinova & Buzek (1971). This reflects the closer agreement of the structure of this Eocene wood with the diagnosis of the form-genus Cercidiphylloxylon than with that of the extant genus Cercidiphyllum (Katsura trees).

Although Brett made a thorough comparison between the Nacton wood and many others of similar anatomy, both living and fossil, knowledge of other Cercidiphyllum-like woods has since been augmented (Prakash et al., 1971; Scott & Wheeler, 1982). Moreover, although the Cercidiphyllaceae is today a monotypic family, (a small Katusura tree, Cercidiphyllum japonicum, grows beside the Museum in High Street, Ipswich), recent investigations have shown that it was more diverse, abundant and widespread in the northern hemisphere in Palaeogene times (Crane, 1981, 1984; Crane & Stockey, 1985). Thus, although amongst living plants the Nacton wood most closely resembles Cercidiphyllum, it is here referred to the less committal form-genus Cercidiphylloxylon in view of its age, our ignorance of the other Organs of its parent plant, and its close agreement with the generic diagnosis of the latter.

The Fabaceae (pea-family or legumes), Cornaceae (dogwood family) and Fagaceae (beech family) are the only families included in Tables 2 and 3 which have representative species in the native British flora today. Each of these families of dicotyledonous angiosperms also has a modern distribution including tropical latitudes. At present the Cercidiphyllaceae is restricted to China and Japan, whilst the similarly warm-temperate ränge of the Platanaceae (plane family) also enters tropical Indo-China. The Theaceae (tea

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family) shows a largely tropical distribution, but occurs also in the south of the USA and in sub-tropical south-east Asia. Most living species of Flacourtiaceae (West Indian Boxwood family), Icacinaceae and Vitaceae (grapevine family) exist in tropical or nearly-tropical latitudes (Good, 1974; Collinson, 1983).

This mixture of apparently tropical and sub-tropical taxa in the London Clay flora has raised much discussion concerning the climate and Vegetation surrounding the London Clay Sea in Eocene times (Collinson et al., 1981; Hubbard & Boulter, 1983).

Palaeogeographical reconstructions for the Palaeogene commonly place the British Isles 5° to 10° south of their present latitude (e.g. Anderton et al., 1979), so that Suffolk would then have been as far south as Istanbul or New York. However, caution must be exercised in the use of this fossil flora and of palaeogeographical reconstruction in the climatology of Eocene England.

The unknown ecological tolerances of extinct Palaeogene species, and differences in the distribution of oceanic waters around the British Isles between the Eocene and Pleistocene are two major considerations which limit attempts to determine the Eocene climate of southern England.

It is noteworthy that none of the families represented in Table 2 occur in Table 3, although fossils of uncertain affinity are included in both. This may be due to differential selection by sedimentary processes so that, for example, stems deposited in a given area may have come to lie near reproductive organs derived from quite distinct taxa and/or habitats. At this point, however, it should be made clear that some of the species listed in this table are known from very few specimens. Thus, for instance, only two pieces of Cercidiphylloxylon spenceri are known to science, part of one being at present on display in Ipswich Museum. Only Single specimens, the holotypes, of Carpolithes ranunculoides, Indes davisii, Mimosites brownianus, Quercinium pasanioides and Vitis minuta have been found, and so none of these species, nor Cercidiphylloxylon spenceri, is known outside of Suffolk.

In the wider context of the other Palaeogene floras of southern England (Chandler, 1964), one finds by comparison that most of the families represented in Tables 2 and 3 occur more widely in their geography, stratigraphy, and also by their variety of different representative organs. Nevertheless, to quote Collinson (1983 p. 12) . . Assington, Suffolk, has yielded the only well-documented legume fruit, Mimosites, from the London Clay.' In addition to the rather artificial floral differences between stem and fructification records which may be due to small sample sizes, such differences may have arisen from greater differences in age than assumed hitherto. The Cercidiphylloxylon and Quercinium specimens were obtained directly from the London Clay, so that neither is less than Lower Eocene in age. However, the woods from Waldringfield are all from the Red Crag and might, therefore, be as young as the basal Pleistocene. Brett (1972) considered the plane-like woods from the Red Crag to have been derived from the underlying London Clay. If these angiospermous wood genera are older than the beds in which they are found, then they may date back to the Cretaceous Period. However, given the rarity of fossils of Lower Cretaceous flowering plants, and their absence from England during the existence of the Upper

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Cretaceous Chalk Sea, it seems likely that the Quercinium and Cercidiphylloxylon have not been reworked but are Eocene in age. For the Red Crag woods, however, a more general designation as being of Cainozoic age seems more appropriate. Since possibly conspecific woods are known from the Oligocene of Czechoslovakia (Prakash et al., 1971) and study of pollen from the Pliocene Epoch from Suffolk (Andrew & West, 1977) has demonstrated the presence of thermophilous trees in the region, the Red Crag woods may have existed well after the London Clay Sea disappeared. The age of these woods might be stated more precisely as Pliocene, but the position of the Pliocene/Pleistocene boundary in relation to the Red Crag is a matter of debate at present (West, 1977).

Although some of the fossil woods in Table 3 are of limited value in complementing the London Clay plants listed in Table 2 from the taxonomic viewpoint, they supply useful information regarding the climate under which trees or shrubs grew during the earlier Cainozoic Era. In general, increasing distinction of growth rings in woods from temperate latitudes passing up through the Cainozoic is taken to indicate an overall reduction in width of the warmer climatic belts which had extended virtually to the poles in Cretaceous times (Creber & Chaloner, 1985). Thus, if these fossil woods from Suffolk are originally of Eocene age, from the approximate palaeolatitude of 42°N, one would expect an absence of clearly-defined growth rings in agreement with a seasonally more constant climate. Although no detailed, quantitative examination of these woods is presented here, their growth rings were observed to be either very variable in width, or, in some cases, lacking (Brett 1956,1960,1972).

This review has been concerned with previously described fossil plants from Suffolk. However, examination of the Palaeontological collections at the British Museum (Natural History) has revealed several undescribed additions to the Suffolk palaeoflora, including additional specimens of already described taxa and of others not previously reported from this county. Descriptions of these further specimens will be given in a later article.

Most of the fossil plants from the Cainozoic of Suffolk described above are part of the collection of the Plants Section of the Department of Palaeontology of the British Museum (Natural History). A catalogue giving the 'V' number and other details of the specimens mentioned in this article has been deposited at the Biological Records Centre at Ipswich Museum.

References Anderton, R . , Bridges, P. H . , Leeder, M. R. & Sellwood, B. W. (1979). A Dynamic Stratigraphy of the British Isles. Allen & Unwin, London.

Andrew, R. & West, R. G. (1977). Pollen spectra from the Pliocene Crag at Orford, Suffolk. N. Phytol., 78, 709.

Bowerbank, J. S. (1840). A history of the fossil fruits andseeds ofthe London Clay. John van Voorst, London.

Brett, D. W. (1956). Fossil wood of Cercidiphyllum Sieb. & Zucc. from the London Clay. Ann. Mag. nat. Hist., 12th ser.,9, 657.

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Brett, D . W . (1960). Fossil oak wood f r o m the British E o c e n e . Palaeontology, 3, 86.

Brett, D . W. (1972). Fossil wood of Platanus f r o m the British E o c e n e . ibid., 15, 496.

Carr, A . P. (1967). T h e L o n d o n Clay surface in part of Suffolk. Geol. Mag., 104, 574.

Chandler, M . E . J. (1961). The Lower Tertiary Floras of Southern England.

1. Palaeocene Floras. London Clay Flora (Supplement). (Text & Atlas).

Chandler, M. E . J. (1964). IV. A Summary and Survey of Findings in the Light of Recent Botanical Observations. British M u s e u m (Natural History) London.

Chandler, M. E . J. (1978). Lower Tertiary Floras of Southern England. V. Tert. Res. Spec. Pap., No. 4., L o n d o n .

Chatwin, C. P. (1961). East Anglia and adjoining areas. (4th E d . ) Br. Reg. Geol., L o n d o n , H M S O .

Clarke, W . B. (1838). Extracts f r o m a Memoir on the Geological Structure and P h a e n o m e n a of the County of Suffolk, and its Physical Relations with Norfolk and Essex. Trans, geol. Soc. London, 2nd. Ser., 5, 359.

Collinson, M. E . (1983). Fossil Plauts of the London Clay. Field Guide to Fossils, No. 1, Palaeontological Association, L o n d o n .

Collinson, M. E . , Fowler, K. & Boulter, M. C. (1981). Floristic changes indicate a cooling climate in the Eocene of southern England. Nature, Lond., 291, 315.

C r a n e , P. R . (1981). Studies on the Flora of the Reading Beds ( U p p e r Palaeocene). Ph.D. thesis, Univ. Reading.

C r a n e , P. R. (1984). A re-evaluation of Cercidiphyllum-like plant fossils f r o m the British early Tertiary. Bot. J. Linn. Soc., 89, 199.

C r a n e , P. R . & Stockey, R . A . (1985). Growth and reproductive biology of Joffrea speirsii gen. et sp. nov., a Cercidiphyllum-like plant f r o m the Late Paleocene of A l b e r t a , C a n a d a . Can. J. Bot., Ottawa, 63, 340.

C r e b e r , G . T. & C h a l o n e r , W. G . (1985). Tree growth in the Mesozoic and Early Tertiary and the reconstruction of palaeoclimates.

Palaeogeogr., Palaeoclimatol, Palaeoecoi, Amsterdam, 52, 35.

Daniels, M . C. (1971). Additional R e p o r t : a f o r e s h o r e sectionof the London Clay at Ramsholt. Tertiary Times, Bromley, 1, 110.

Davis, A . G . & Elliott, G . F. (1951). T h e L o n d o n Clay of Coastal Suffolk and Essex. Geol. Mag., 88, 329.

Davis, A . G . & Elliott, G . F. (1958). T h e Palaeogeography of the London Clay Sea. Proc. Geol. Assoc. London, 68, 255.

G e o r g e , W . & Vincent, S. (1976a). Some river exposures of L o n d o n Clay in Suffolk and Essex. Tert. Res., Leiden, 1, 25.

G e o r g e , W . & Vincent, S. (1976b). Further exposures of L o n d o n Clay in Suffolk and Essex, ibid., 1, 51.

G o o d , R . (1974). The Geography of the Flowering Plants. (4th E d . ) Longman, London.

H u b b a r d , R. N. L. B. & Boulter, M. C. (1983). Reconstruction of Palaeogene climate f r o m palynological evidence. Nature, Lond., 301,147.

Prakash, U . , Brezinova, D. & Buzek, C. (1971). Fossil woods f r o m the

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63 Doupovske hory and Ceske stredohon Mountains of Northern Bohemia.

Palaeontographica, Stuttgart, B 133, 103.

Reid, C. (1890). The Pliocene deposits of Britain. Mem. Geol. Surv. UK London.

Reid, E. M. & Chandler, M. E. J. (1933). The London Clay Flora. British Museum (Natural History), London.

Scott, R. A. & Wheeler, E. A. (1982). Fossil woods from the Eocene Clarno Formation of Oregon. Int. Assoc. WoodAnat. Bull., Newhaven Conn 135. ' ' Simpson, F. W. (1982). Simpson's Flora of Suffolk. Ipswich. Suffolk Naturalists' Society.

Spencer, H. E. P. (1966). A Contribution to the Geological History of Suffolk. Pt. 1. - Summary of the geological sequence. Trans. Suffolk Nat. Soc., 13, 197.

West, R. G. (1977). Pleistocene Geology and Biology. (2nd. Ed.) Longm London.

Wilkinson, H. P. (1984). Pyritised twigsfrom Sheppey. Tert. Res., Leiden, 5, Acknowledgements I thank Drs. G. T. Creber and M. E. Collinson (both of the University of London) for kindly reading initial manuscripts of this paper and for their helpful criticisms.

H. L. Pearson, Palaeontology Department, British Museum (Natural History), Cromwell Road, London SW7 5BD

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