Interglacial Deposits at Trafalgar Square, London

Interglacial Deposits at Trafalgar Square, LondonAuthor(s): J. W. FranksSource: New Phytologist, Vol. 59, No. 2 (Jul., 1960), pp. 145-152Published by: Wiley on behalf of the New Phytologist TrustStable URL: http://www.jstor.org/stable/2429192 .

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INTERGLACIAL DEPOSITS AT TRAFALGAR SQUARE, LONDON

BY J. W. FRANKS

The Herbarium, Manchester Museum, University of Manchester

(Received 9 September 1959)

(With Plate 6 and 3 figures in the text)

SUMMARY

Fossiliferous gravels were discovered during recent building operations on the south side of Trafalgar Square. At a later date organic deposits were exposed and an investigation of their plant remains was undertaken by the writer.

A similar organic deposit had previously been described from the site of the Admiralty Offices (Abbott, I892). In that work the following plants were recorded: Amblystegium riparium Schimp., Hypnum stramineum Dicks., H. fluitans Hedw., Potamogeton sp., Lemna cf. polyrhiza, Ceratophyllum demersum L., Polygonum sp., Rumex sp., Carex sp., Scirpus sp., and Betula nana L. With the exception of B. nana all the vascular plants recorded above have been also recognized in the present study. It seems probable that the record of B. nana was due to mis-identification, since the general aspect of the flora is not one of cold or open conditions.

The mammalian and molluscan remains from the present site have been studied by Dr. A. J. Sutcliffe and Mr. M. P. Kerney and will be published in detail later. The list of mammals forms an interesting counterpart to the plant determinations and is as follows: Panthera spelaea (Goldfuss), cave lion; Rhinoceros sp. indet., rhinoceros; Palaeoloxodon antiquas (Falconer), straight-tusked elephant; Bos primigenius Bojanus, wild ox; Hippo- potamus amphibius Linn., hippopotamus; Cervus elephas Linn., red deer; Dama cf. dama (Linn.), fallow deer. In addition a coprolite suggests that hyaenas may have been present and remains of bears not represented at this site have been found on two previous occasions during nearby excavations in other parts of the same terrace.

STRATIGRAPHY OF THE ORGANIC DEPOSITS

The organic deposits with which this study is concerned vary in thickness from 2 to 5 ft (o.6 to 1in m). The greater part of them lies below present sea level. Their position in relation to the fossiliferous gravels of the terrace will be discussed in greater detail in a forthcoming paper.

Fig. i shows the stratigraphy of the organic deposits as seen in the three monoliths used for plant analyses. The basal deposit of the series is an orange gravel which is overlain by a layer of grey clay. This is in turn overlain by brown sand. Above this is a brown clay, sandy in parts, which forms the greater part of the organic deposit. At its upper limit is a layer of coarse sand.

In the basal part of this sequence isolated lenses of compacted plant remains occur. B N.P. I45



I46 J. W. FRANKS

These are the deposits referred to by Abbott (I892) as peaty strata. They contain frag- ments of wood, stems, large quantities of hazel nuts and other fruits and seeds, much broken and indeterminable plant debris, sand and small stones. It seems likely that they represent flood or storm debris.

The greater part of the sequence appears to represent sedimentation in relatively still water in which a rich aquatic flora was growing.

MONOLITH L

L

0. D. '

L. L~~~~~~~~~~~~

L

L ~~~~~~L

L~~~~~~~~~~~~~

, ] ~SAND CLAY PLANr LENSES

Fig.. The stratigraphy of the organic deposit as shown in the three monoliths from which plant remains were recovered.

POLLEN DIAGRAMS AND PLANT REMAINS

Introduction The samples used in this investigation were collected as exposed during the course of the excavation. Three monoliths were taken from the organic deposits in different areas and all isolated lenses of plant remains were collected. The pollen diagrams Figs. 2 and 3 were prepared from samples taken fro'm monolith I.

The monoliths were divided into samples of equal bulk and examined for macroscopic plant remains.

At various times during the course of the excavation samples of sediment from levels other than that of the organic deposit were examined but none of these samples yielded any plant remains.



Interglacial deposits in London I47

T :> 0 20 0 10 0 40 0 30 0 100 0 :tk0

4~~ ~~ s~~~~~ ' '0 TREES -SHRUBS HERBS

2

3 L 4

L

L

*L

4 4+ + 182

L. 2 24

I ~~~~~~~~~~~~~~~175 12

+~~+ I '

IS

o 20 010 0 40 0 30 0 00o 0 100

Fig. 2 The tree pollen diagram showing the relative proportions of tree pollen. The pollen of Corylus is excluded from the tree pollen total.

Pollen diagrams It is at once clear from the pollen diagrams Figs. z and 3 that the whole of the organic deposit formed under uniform vegetational conditions, and that the diagram cannot therefore be zoned.

~~~~~~~~~'~ ~~~~~~'

3 1 _ . * _ If f + t + +

% G ' 4L 4 ~ '

S2 i +1+ + + + + + - + 1

+2- U++ +++ + 1- ++

+ - -I A++ +

plants~ ~ ~ ~ ~~~~~ ' exrese 4s Or pecntg of th repllnttl

2~~~~~~~~~~~6+++ + + + + + +

+ +

7 + + ~~~~~~~4+ +++ + I - +

6

12 ~~~~~~~~~+ + + + 4

r3+ + +4 + f+ ++ 4-- + +

lOG 6 "0_0 _.' less than 14

Fig. 3. The non-tree pollen diagram showing the relative proportions of the herbaceous plants expressed as a percentage of the tree pollen total.



I48 J. W. FRANKS

In the vegetation represented by the pollen diagram the dominant woodland tree is Quercus, the pollen of which forms 30-40% of the tree pollen total. Pinus and Betula together make up 20 %, whilst the pollen of Fraxinus and Ilex occurs in small but consistent amounts; Acer (probably A. monspessulanum) provides 30-40 o of the tree pollen total, but it is doubtful if this species can be regarded as a true woodland tree. The percentage of Corylus pollen is high throughout the diagram.

The non-tree pollen diagram shows a rich flora of both aquatic and terrestrial types. The Gramineae and Cyperaceae are dominant, with other herbaceous types present in much smaller amounts. The total of non-tree pollen excluding Corylus never falls below 70?% of the total tree pollen.

Macroscopic plant remains The samples from which macroscopic plant remains were obtained were of two types, the sandy clays of the organic deposit and the isolated lenses of plant debris. The com- plete list of plants recorded from this site is shown in Table i.

In the samples from the monoliths, apart from where they cut through a plant lens, the yield was small. None the less they allowed the recognition of a large aquatic flora. Analysis revealed no quantitative differences in their frequencies through the deposit.

The lenses of plant material yielded great numbers of fruits and seeds, many of which represent the terrestrial flora of the time. Several species, notably C. avellana, Acer monspessulanum, Ceratophyllum demersum, Cornus sanguinea and Najas marina were represented by several hundreds of fruits in each lens. Twigs of Crataegus sp. bearing thorns were also particularly abundant. A collection of the macroscopic remains has been deposited in the Department of Palaeontology, British Museumn (Natural History).

Species of special interest Trapa natans L. (Plate 6). This plant is characteristic of interglacial deposits found on the European continent and is a component of their rich thermophilous aquatic floras, which typically include Brasenia purpurea and Aldrovanda vesiculosa. The very characteristic fruits of Trapa natans were found at two horizons.

Xanthium sp. (Plate 6). Several fruits of this genus were seen at two horizons. The fruits found most closely resemble those of X. strumarium L. The centre of distribution of this genus is given as America though the reality is somewhat obscured by the genus having been spread by man in historic times.

Acer monspessulanum L. (Plate 6). Pollen and winged fruits of Acer were found at all horizons and leaves from one sample only. The fruits and leaves can certainly be ascribed to A. monspessulanum L. The winged fruits were amongst the most abundant macroscopic remains found. The high percentage of the pollen of Acer is noteworthy as being high for an insect-pollinated tree and indicative of great abundance of the tree in the contemporary landscape.

Correlation with other interglacial deposits The evidence of the pollen diagrams and the assemblage of macroscopic plant remains indicate that this interglacial flora belongs to zone f of Jessen and Milthers for the Eemian, or Last Interglacial of Denmark (Jessen and Milthers, 1928). However, although the samples analysed cover a considerable depth of deposit it is evident that only a part of the time covered by zonef is represented in the pollen diagram.



Interglacial deposits in London '49 Table i. The plant list

Monoliths Isolated plant lenses

A. monspessulanum~~ L. 0 Alnus cf. glutinosa (L.)rGaertn. 4 p

Acerul sp. p Ca.e mosp.suau .6 ???? AjCarpcf. reptasL 5 p ACsaryphlanaolnela taa L.p

Alnus cf glutinsa (L.) aertn. pi

Certua sp. p

Ceratophyllum demersum L. 4 Chenopodiaceae p Chenopodium album L. 2

C. botryodes Sm. 5 C. hybridum L. 3 C. rubrum L. 3 Cladium mariscus (L.) Pohl 5 p Compositae Compositae liguliflorae p C. tubuliflorae p Cornus sanguinea L 5 Corylus avellana L 2 p Crataegus sp. 5 Cruciferae p Cyperaceae p Filipendula ulmaria (L.) Maxim. 2 p Fraxinus sp. p Galium sp. p Geranium sp. p Hedera helix L. 5 p Hippuris vulgaris L. 2

Hydrocotyle sp. p Ilex sp. 5 P - Labiatae p Lemna sp. 3 p - Lycopus europaeus L. 4 Myrica sp. p Mentha aquatica L. 5 Myriophyllum sp. M. alterniflorum DC. 2 p M. spicatum L. 2

Najas flexilis (Willd.) Rostk. & Schmidt 5 N. marina L. 4 N. minor 6 Nuphar cf. luteum (L.) Sm. 2 Nymphaeaceae p Nymphaea cf. alba L. 3 Osmunda sp. 5 p Pinus sp. p Plantago lanceolata L. 3 p P. media L. 2 p Polypodium vulgare L. 2 p Polygonum sp. Populus sp. p



I50 J. W. FRANKS

iMionoliths Isolated plant lenses

O~ O-O O O cn

-4 0*

(4 40 D-4e 0 00. a a a a

Potamogeton sp. Potentilla sp. P Primulaceae p Prunus spinosa L. 6 Pteridium aquilinum (L.) Kuhn 3 p Pterocarya sp. P Quercus sp. p Ranunculus sp. p R. acris L. 2 R. aquatilis agg. 2

R. parviflorus L. 6 R. repens L. 2

Rosaceae p Rubus sp. R. fruticosus L. Rumex sp. R. acetosa L. 2 p Salix sp. p t Ruppia sp. Sambucus nigra L. 5 p Schoenoplectus lacustris (L.) Palla 2 Scrophulariaceae p Sparganium sp. Stellaria sp. S. aquatica (L.) Scop. 4 S. holostea L. 4 S. media (L.) Vill. 2

Taxus baccata L. 5 Tilia sp. p Trapa natans L. 6 Typha angustifolia L. 4 p Ulmus sp. Umbelliferae p Urtica sp. p Urtica cf. dioica L. 2

Verbena officinalis L. 5 Viola sp. Xanthium cf. strumarium 6 Zannichellia sp. 3

* In this sample Acer monspessulanum is represented by leaves. t In these samples Salix is represented by leaves. p indicates identification by pollen only.

A comparison with other British Last Interglacial sites reveals similarities between the pollen diagrams from Trafalgar Square, the upper part of the Bobbitshole sequence (West, I957), and the lower part of the Histon Road, Cambridge, sequence (Walker, I953).

The- main features of the pollen diagram are the pronounced dominance of Quercus and Acer over the other trees, the high percentage of Corylus, the occurrence of Carpinus pollen and the low AP/NAP ratio; all of which suggest that it is the upper part of zonef which is represented.

Ninety-three species are recorded from this site, aquatic plants being well represented



Interglacial deposits in London I5'

among them. The land plants include many characteristic of open scrub rather than woodland conditions, for example the genera Acer, Cornus, Prunus, Crataegus and Sambucus.

An analysis has been made of the distribution of the plants represented in Table i, using the same categories as those adopted by West (I957).

Table z Distribution categories I 2 3 4 5 6 No. of species/group o I7 7 7 I4 5 Per cent of flora/group ? 34 I4 I4 z8 IO

i, Arctic alpine; z, General distribution in Scandinavia; 3, Northern limit Scandinavia near Arctic Circle; 4, Northern limit between z and 3; 5, Northern limit southern Scandinavia; 6, Northern limit south of Scandinavia.

The largest number of plants belong to group 2, which includes many aquatic plants and plants which owe their present distribution to human activity.

In groups 5 and 6, the more southern species, the relatively high percentage of species and the great numerical abundance of remains of some of them suggest that the climate during this part of zonef was warmer than at present.

COMPARISONS AND CONCLUSIONS

It appears from comparison with previously published diagrams that the Trafalgar Square organic deposit belongs to zone f of Jessen and Milthers's scheme for the Last Interglacial, and that it resembles the upper part of the Bobbitshole sequence, the lower part of the Histon Road sequence and-also the single sample, I938, mentioned in Holling- worth, Allison and Godwin (I950).

Recent work in Denmark has shown that the second temperature maximum of the Jessen and Milthers Eemian sequence (zone 1), was actually much cooler than was origin- ally thought (Andersen, I957). This greatly strengthens the case for referring those parts of the Last Interglacial sequence showing evidence of a temperate climate with mixed oak forest, Acer and abundant Corylus to zonef rather than zone 1.

A marked difference between the Trafalgar Square diagram and the corresponding parts of the continental diagrams is the low frequency of Alnus in the former. This feature has, however, also been noted by West (I957) in the East Anglian diagrams. Since the Trafalgar Square diagram appears to cover a part of the gap between the- top of the Bobbitshole diagram and the base of the Histon Road diagram the continued low frequency of Alnus pollen appears to be established as an interesting and consistent feature of British Last Interglacial pollen diagrams.

Though the flora here recorded is not so rich as those from the Continental Last Interglacial (i.e. in Jessen and Milthers (I928) and Van der Vlerk and Florschutz (I953) ) it is, nevertheless, a richer one than any previously recorded for this country. The aquatic flora includes Ceratophyllum demersum, three species of Najas and the characteristic water plant Trapa nratans.

The terrestrial flora was also rich in temperate species, many being present in great numbers, with Acer monspessulanum, Prunus spinosa, Cornus sanguinea, Taxus baccata and Crataegus particularly abundant.



152 J. W. FRANKS

ACKNOWLEDGMENTS

My thanks are due to the Crown Agents on behalf of the Uganda Government; Ford & Walton Ltd., contractors; H. W. Lane, Esq., clerk of works; G. A. Sansom, Esq., general foreman; and to the trustees of the British Museum (Natural History).

REFERENCES

ABBOTT, L. (I892). The section exposed in the foundations of the new Admiralty Offices. Proc. Geol. Ass., 12, 346

ANDERSEN, Sv. TH. (I957). New investigations of Interglacial freshwater deposits in Jutland. Eis. & Gegen., 8, i 8 i

HOLLINGWORTH, S. E., ALLISON, J. & GODWIN, H. (I950). Interglacial deposits from Histon Road, Cam- bridge. Quart. J7. Geol. Sci, 105, 495.

JESSEN, K. & MILTHERS, V. (I928). Stratigraphical and palaeontological studies of the Interglacial freshwater deposits in Jutland and N. Germany. Danm. Geol. Unders. (II Raekke), 48, 9.

VAN DER VLERK, I. M. & FLORSCH1TZ, F. (953). The palaeontological base of the subdivision of the Pleistocene of the Netherlands. Verhandl. d. Kon. Ned. Akad. Naturk. E. Rk., 20 (2), 2.

WALKER, D. (I953). The Interglacial deposits at Histon Road, Cambridge. Quart. J. Geol. Sci., Io8, 273. WEST, R. G. (I957). Interglacial deposits at Bobbitshole, Ipswich. Phil. Trans. Roy. Soc., B, 241, I.

EXPLANATION OF PLATE 6

Fruits from the Interglacial deposits at Trafalgar Square. Fig. i. Winged fruit of Acer monspessulanum L. Fig. 2. Fruit of Xanthium sp. showing spines and characteristic double beak. Fig. 3. Fruit of Trapa natans L. (All reproduced x z)



THE NEW PHYTOLOGIST, 59, 2 PLATE 6

............. . . . ..... . . ..... . .... . . ...... ...

2

FRANK(S-INTERGLACIAL DEPOSITS IN LONDON (Faci'ng Pi. 15Z.)



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Interglacial Deposits at Trafalgar Square, London