Reworked mesozoic spores in tertiary leaf-beds on Mull, Scotland

Review of Palaeobotany and Palynology, 17(1974): 221--232 ©Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

R E W O R K E D M E S O Z O I C S P O R E S IN T E R T I A R Y L E A F - B E D S O N MULL, SCOTLAND

LINDAPHILLIPS* Department of Geology, Imperial College of Science and Technology, London (Great Britain) (Accepted for publication May 17, 1974)

ABSTRACT Phillips, L., 1974. Reworked Mesozoic spores in Tertiary leaf-beds on Mull, Scotland. Rev. Palaeobot. Palynol., 17 : 221--232. Samples from the Lower Tertiary leaf-beds at Ardtun on the Isle of Mull, Scotland, yield an entirely reworked Jurassic spore assemblage. While the Rhaetian and Lower Jurassic are quite well-represented on Mull, Middle and Upper Jurassic rocks are rare. The presence of spores of this age indicates that the outcrop of these rocks was of greater extent in the Early Tertiary. Other instances of geological information being obtained from studies of reworking are given. Contemporaneous Early Tertiary spores are absent from the Ardtun deposits, which may be due to formation of the deposits in flood conditions or to differential destruction of the reworked and unreworked spores. Methods of detecting reworked pollen and spores are reviewed, and the potential problems inherent in a sample where only reworked spores occur are pointed out.

INTRODUCTION -- THE ARDTUN LEAF-BEDS In t h e course o f an investigation into the p a l y n o l o g y o f L o w e r T e r t i a r y r o c k s in N o r t h w e s t S c o t l a n d , samples t a k e n f r o m t h r e e specimens in the J. Starkie G a r d n e r c o l l e c t i o n o f S c o t t i s h Tertiary leaf impressions were m a c e r a t e d for pollen and spores. This collection, w h i c h is n o w h o u s e d in the British Museum, consists m a i n l y o f material f r o m the A r d t u n leaf-beds o n Mull ( F i g . I A , B ) , w h i c h were first described b y the D u k e o f Argyll (1851). T h i n layers o f limestone, s a n d s t o n e a n d clay bearing well-preserved leaf impressions o c c u r in a series o f c o n g l o m e r a t e s within the lava succession. The leaf assemblage includes ferns, conifers and a variety o f angiosperms, and t h e leaves have been described b y F o r b e s (in Argyll, 1 8 5 1 ) , G a r d n e r and E t t i n g s h a u s e n ,(1882), G a r d n e r ( 1 8 8 5 , 1 8 8 6 , 1 8 8 7 ) and Seward and H o l t t u m (1924). T h e three specimens used in this s t u d y (Plate I) were pieces o f m u d s t o n e and s a n d s t o n e bearing a n g i o s p e r m leaf impressions and s o m e o t h e r impressions. In t h e following descriptions, the s p e c i m e n and slide n u m b e r s .

*Present address: Robertson Research Ltd., 23 Nassim Road, Singapore 10.

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are British Museum (Natural History) reference numbers, and the plant identifications are those given with the specimens. V. 25101 Brownish-white calcareous m u d s t o n e with impressions of a Corylus leaf and a not he r d i c o t y l e d o n o u s leaf. Slide nos. V. 25101 A and B. V. 2 5 0 5 6 Brownish-white calcareous m u d s t o n e with an impression of a Platanus inflorescence. This specimen also has an impression of a Cercidiphyllum leaf. Slide nos. V. 25056 A and B. V. 25065 Dark grey calcareous ash sandstone with an impression of a Platanus leaf. Slide nos. V. 25065 A and B. The samples were br oke n dow n in 10% HC1 and 40% HF, then oxidised for 5 min in c o n c e n t r a t e d HNO3. The residues were m o u n t e d in glycerine jelly. THE SPORE ASSEMBLAGE AND AGE OF THE LEAF-BEDS The three samples yielded essentially similar spore assemblages, and the total assemblage is given below. Pteridophytes:

Gymnosperms:

Deltoidospora Miner 1935 Conttgnisporites D e t t m a n n 1963 Osmundacidites wellmanii

Cycadopites (Wodehouse) Wilson

Couper 1953

Heliosporites altmarkensis Schulz 1962

Marattisporites scabratus Couper 1958 Kluktsporites Couper 1958 Leptolepidites major Couper 1958

and Webster 1946

Classopollis Pflug 1953 Alisporites Daugherty 1941 A. grandis (Cookson) D e t t m a n n 1963

Tsugaepollenites mesozoicus Couper 1958

Vitreisporites pallidus (Reissinger) Nilsson 1958

The most striking feature of the assemblage is that it consists entirely of p t e r i d o p h y t e spores and gym nos per m pollen. No angiosperm pollen was fo u n d although the rocks bear impressions of angiosperm leaves. Most of the pollen and spores have a range extending all through the Jurassic, although some are more restricted. Heliosporites is characteristic of Rhaetic and Lower Liassic assemblages, Klukisporites and Leptolepidites major are Middle and Upper Jurassic types, though each has been recorded once from older rocks, and Contignisporites, though k n o w n in the Lias, does n o t becom e c o m m o n until the Upper Jurassic. While it is conceivable that all these spores could have been derived from the Lias, it seems unlikely that in a small assemblage several types should occur t oget her at the limits of their stratigraphic range. It is mo r e probable t ha t the assemblage is a mixed one, covering the Lower and Middle Jurassic and possibly the Upper Jurassic, although the absence of Cicatricosisporites suggests that the later part of the Upper Jurassic is not represented.

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225 Other evidence points to a m uc h younger age for these beds. On stratigraphic evidence, the lavas c a n n o t have been ext ruded before the end of the Cretaceous, as t h e y overlie Upper Cretaceous sandstone and limestone on Mull and on th e adjacent mainland and islands (Richey, 1961). F r o m studies of the macroflora of Ardtun, Argyll (1851) and Heer (1859) assigned the interbasaltic beds t o the Miocene, although Gardner (1887) and Seward and H o l t t u m (1924) regarded the leaf flora of Mull and similar leaf floras in Greenland and the Arctic as indicating an Early Eocene age for the deposits. On the basis o f the pollen flora of the interbasaltic beds at Bremanoir, a mile east of Ardtun, and at Shiaba also in western Mull (Fig.lB), Simpson {1961) concluded that the beds were Miocene in age, although the flora was given an unduly recent aspect by his identifications of all the pollen types as living genera. The pollen t y p e A q u i l a p o l l e n i t e s occurs at Shiaba and Bremanoir, suggesting an age between Maastrichtian and Early Eocene, and N u d o p o l l i s thiergartii, an indicator of the Palaeocene in Germany, occurs at Bremanoir (Martin, 1968). These types were also identified by Watts {1970) who came to similar conclusions a bout the age of these floras. A Palaeocene age for the leaf-beds is confirmed by the most recent radiometric datings of the lavas in the area. These indicate t ha t the oldest plateau lavas of Mull, in which the Ar d tu n leaf-beds occur, were erupted in the Early Palaeocene (Evans et al., 1973). It is clear f r om this evidence that the spore assemblage from the Ar d tu n leaf-beds must be entirely reworked from Jurassic rocks, and that no c o n t e m p o r a n e o u s pollen is present. SOURCE OF THE REWORKED SPORES The spores must have been derived f r om most stages of the Jurassic except for the very latest. Rhaetic sandstone is exposed at Gribun on the west coast o f Mull (Fig.lB), and the Lower Liassic is quite well~leveloped south of Gribun (Lee and Bailey, 1925; Richey, 1961). E xcept for a small faulted o u t c r o p of Middle Liassic sandstone in nort hern Mull, the rest of the Liassic and the Middle Jurassic are represented only in southeastern Mull, and only the Inferior Oolite is more than fragmentary. Upper Jurassic rocks have n o t been f ound on Mull, except for a small d o w n f a u l t e d patch of shale o f Kimmeridge Clay age, again in the southeast. So remains of possible source rocks for the Lower Jurassic spores are to be found on the island, but Middle Jurassic rocks are of very limited e x t e n t and Upper Jurassic rocks are PLATE I 1. 2. 3. 4. 5. 6. 7.

Platanus leaf. V. 25065. x 2/3. Corylus leaf. V. 25101. x 2/3. Platanus inflorescence (arrowed) and Cercidiphyllum leaf. V. 25056. X 2/3. Heliosporites altmarkensis Schulz. Slide no. V. 25101 B. x 750. Klukisporites Couper. Slide no. V. 25101 A. X 750. Contignisporites Dettmann. Slide no. V. 25056 A. x 750. Leptolepidites major Couper. Slide no. V. 25101 B. x 750.

226 virtually absent. There are two possibilities for the source of the Middle and Upper Jurassic spores. First, the Jurassic rocks may have been eroded into the Cenomanian sea, and the spores then redeposited for the second time when Upper Cretaceous rocks were being eroded in Early Tertiary time. The Greensand overlies Rhaetic sandstone at Gribun and it is possible that such an arrangement could have furnished all the spores in the assemblage. Samples of Cenomanian sandstone and clay from Ben Iadain in Morvern were macerated for spores but no Jurassic material was found, so polycyclic reworking appears unlikely. Second, patches of Middle and Upper Jurassic rocks may have been protected from erosion by faulting and only finally removed in the Early Tertiary. This seems more probable, especially in view of the pocket of Kimmeridge Clay preserved by faulting near Duart Bay. It is apparent from the evidence of the reworked spores that Jurassic rocks were more extensive on Mull in the Early Tertiary than they are now and that their reduction or final removal was accomplished at that time, and not solely within the Jurassic and Cretaceous. This illustrates one way in which reworking, which is always a result of erosion, can be turned to advantage, indicating the former extent or existence of rocks now almost or wholly absent. The literature contains some other examples of the use of reworking. Reworked Palaeozoic and Mesozoic spores, including Jurassic and Lower Cretaceous types, occur in quantity in Palaeocene sediments in Alabama, which suggests that Jurassic and Lower Cretaceous rocks were exposed in the Palaeocene, although no outcrops of this age are known in the area now (McLean, 1968). Kedves et al. (1966) describe Upper Tertiary basins in Hungary containing reworked Permian, Mesozoic and Danian--Lower Palaeocene spores, the latter being significant as no rocks of Danian--Early Palaeocene age are known in Hungary. Muir (1967) discusses several cases of reworked Carboniferous material at localities in Poland, two of which, when taken with geological evidence, indicate the changing extent of the Upper Silesian Coal Basin through the Namurian and Westphalian (Turnau, 1962; Dembowski and Jachowicz, 1964). Stanley (1965) found that higher proportions of reworked pollen and spores occurred in Pleistocene marine deposits in glacial periods because of the high rate of erosion, and he proposed that relative lowerings of base-level could be detected by increased percentages of reworked pollen. In studies of ocean-bottom sediments from the western Atlantic (Stanley, 1966a, 1967), he attempted correlations of cores using the changing percentages of reworked pollen and spores. He also describes instances in which the reworked spore content of Pleistocene marine sediments could be used to trace the source areas of these deposits (Stanley, 1966b). Reworking of other microfossils has also been put to use, and Jones (1958) quotes a case in which the occurrence of reworked Foraminifera in the Wanship Formation in the Upper Cretaceous of Utah was used to determine the a m o u n t of erosion between the Wanship and the underlying formation (Lankford, 1953).

227 ABSENCE OF CONTEMPORANEOUSPOLLEN

A possible explanation for the absence of contemporaneous pollen from the Ardtun deposits is the formation of the leaf-beds in flood conditions in autumn. Muller (1959) found that the overall pollen content in the levees of the Orinoco delta was lower than in the rest of the delta, and of this pollen a relatively high proportion was reworked. This was explained by Muir (1967) as resulting from erosion upstream and flooding of the delta when the rivers were in spate. Fluviatile sediments are anyway relatively poor in pollen compared with autochthonous deposits and at Ardtun this might have been accentuated by increased discharge at a time of year when little pollen would be in the air. At the same time, erosion of sedimentary rocks upstream would result in an influx of older spores into the rapidly accumulating leaf-bed. It might be expected that some pollen would be brought into the deposits through erosion of the channel banks, although pollen in river clay soils is highly susceptible to microbial attack (Havinga, 1967) and river banks tend to be subject to an alternation of oxidising and reducing conditions with changes in water level. Another objection to the formation of the leaf-beds in flood conditions is the nature of the sediment, which in two of the samples is a fine-grained mudstone which would have been deposited in a low-energy environment. The leaf-beds were originally thought to have been laid down in the backwaters of a river system (Gardner, 1887) or in a shallow lake (Argyll, 1851; Seward and Holttum, 1924). The thin sequence of sandstones, limestones, mudstones and clays comprising the Ardtun leafbeds occurs within a series of conglomerates and sandstones and shows considerable horizontal variation in thickness and in the beds represented (Gardner, 1887). The beds appear to have been deposited in the channels of a meandering or braided river and there is little to suggest flood conditions or seasonal storms causing very rapid sedimentation, although the fine sediments may have settled out on the floodplain after a flood, in the manner that Geikie (1896) envisaged for the interbasaltic beds on Canna. Another possibility is the differential destruction of pollen and spores after their incorporation into the sediment. It has been observed that fossil pollen is more resistant to destruction than fresh pollen, and that reworked pollen is more resistant than primary fossil pollen. Reworked pollen may have become degraded, possibly through pressure and abrasion (Cushing, 1964), or it may have become coalified in its original deposit through heating. Both these changes seem to make reworked pollen more resistant at least to chemical attack than is primary fossil pollen. Chemical attack may involve oxidation, which is probably the commonest cause of pollen destruction, although Brush (1966) included reducing conditions and high pH among the factors that may be responsible for the absence of pollen from apparently favourable sediments.

228 DETECTION OF REWORKING The detection of reworked spores is straightforward when spores or sporebearing rock fragments have been reworked from much older rocks, and the spores are of quite different types from the contemporaneous assemblage. Dijkstra (1950) found Carboniferous megaspores in Dutch Cretaceous sediments and also identified megaspores found by M. E. J. Chandler in Tertiary and Quaternary deposits in southeast England as Carboniferous types. Cookson (1955) describes occurrences of Permian microspores in Australian Upper Cretaceous sediments. Muir (1967) quotes cases from Poland in which Mesozoic deposits contain Carboniferous spores or coal fragments, and Van Gijzel (1967) mentions Middle Tertiary marine deposits in The Netherlands and northwest Germany which are contaminated with Mesozoic or older spores. Other clear-cut instances are c o m m o n in Pleistocene deposits where spores or rock fragments from older rocks are often incorporated into till sheets and the spores undergo a further cycle of reworking at times of high erosion, particularly in early and late glacial phases under solifluction conditions. In pollen diagrams from late Lowestoftian deposits in East Anglia, West (1956) and Turner (1970) indicate a pre-Quaternary component, reworked from the underlying boulder clay. Birks (1970) found Jurassic spores in late Weichselian silts on Skye, probably derived from the till which is locally rich in Jurassic rock fragments. A similar case was reported by Cushing {1964) from a site in Minnesota where late Wisconsin sediments contain Cretaceous spores reworked from the till which contains fragments of Cretaceous rocks. Reworking of older pollen and spores in Quaternary deposits may take place directly from erosion of older rocks, and Davis (1961) describes late Wisconsin sediments at Taunton, Mass., which were contaminated with Tertiary pollen by meltwater streams eroding Tertiary deposits. Reworking is harder to detect where morphological differences are not obvious, as is the case where long-ranging types are involved or where the age difference is small. Reworked Tertiary pollen is c o m m o n l y found in European Pleistocene deposits because of severe erosion in the Pleistocene of the extensive Tertiary browncoals, and examples are known from The Netherlands, Germany and Poland (Van Gijzel, 1967). The Tertiary and Quaternary pollen may be very hard to separate. Stanley (1965) found that acceptance of the stain Safranin O differed in reworked and unreworked pollen, and used this to detect reworked Upper Tertiary and Pleistocene pollen in Pleistocene and Recent marine sediments off the east coast of the United States. Degradation of pollen and spores may indicate reworking, although reworked pollen in till may be perfectly preserved (Cushing, 1964) and fresh pollen may become broken and degraded during stream transport (R. M. Peck, quoted in Birks, 1970). The fluorescence of pollen and spore exines changes with age, and this has been used to determine reworked pollen (Van Gijzel, 1967; Phillips, 1972).

229 These methods are concerned with the state of the spores themselves, and rely on changes in the exine brought about by reworking and age. Another approach to the problem is described by Muir (1967) who identified a reworked c o m p o n e n t in a Middle Jurassic assemblage by studying the lithologies in which suspected reworked spores occurred and the palynology of deposits containing remains of possible parent plants. The most frequently described cases of reworking on a small time scale are those within the Pleistocene, which differs from most earlier periods in that repeated rapid migrations are involved but little evolutionary change has taken place, so that reworking on a very small scale can greatly alter assemblages and the apparent migrational history of individual taxa. A further difference is that assemblages are composed of living genera and can be interpreted in terms of the ecology of living plants. Supposed ecological incompatibility of plants in an assemblage is not without dangers as a criterion for detecting reworked pollen (Davis, 1961) but this m e t h o d has often been used, especially for late glacial and early glacial assemblages (Andersen, 1954; Turner, 1970). More commonly, botanical criteria have been used in conjunction with evidence provided by the sediment type. Iversen (1936) pointed out that reworked pollen occurs in late glacial depo,~its with a high mineral content, while autochthonous organic deposits are often quite free from contamination. On this basis, Zagwijn (1961) distinguished between reworked tree pollen in early glacial deposits of sandy gyttja, and contemporaneous tree pollen in overlying peats at Amersfoort in The Netherlands. Reworking may take place on an even smaller time scale, when recently deposited pollen is washed from the soil into the sediment (Cushing, 1964). Penecontemporaneous reworking may be indicated by corrosion of the pollen due to oxidation and microbial attack in the soil and also by the occurrence of fungal remains washed in from the litter horizons. This type of reworking does not cause serious problems, although the regional pollen record will be distorted at the levels where it occurs, as the inwashed pollen will be principally local in origin (Birks, 1970). In all the cases discussed so far, reworked spores occur together with contemporaneous spores in the deposit, which is then dated according to the youngest spores present. Spores of different ages are present, however small the age difference may be. The situation at Ardtun is unusual in that the rocks contain contemporaneous macroscopic plant fossils but an entirely reworked spore assemblage. The reworking was detected because other evidence showed the age of the rocks to be much less than that indicated by the spores. The sediments at Ardtun are allochthonous river deposits, and the problem of reworking is greatly reduced in autochthonous lignites. At Bremanoir and Shiaba (Simpson, 1961) the lignites are rich in pollen, only a small proportion of which, including some of the bisaccate and monocolpate pollen, is likely to be reworked.

230 CONCLUSIONS Serious p r o b l e m s o f r e w o r k i n g are u n l i k e l y to o c c u r in a u t o c h t h o n o u s d e p o s i t s , b u t such s e d i m e n t s m a y n o t always be available. In a l l o c h t h o n o u s d e p o s i t s c o n t a i n i n g r e w o r k e d m a t e r i a l , t h e r e w o r k e d c o m p o n e n t is s e p a r a t e d as well as possible and t h e d e p o s i t is d a t e d a c c o r d i n g to pollen and spores t h a t are d e f i n i t e l y c o n t e m p o r a n e o u s . A t A r d t u n t h e a s s e m b l a g e is e n t i r e l y r e w o r k e d , a n d a l t h o u g h it is n o t clear w h y t h e r e is no c o n t e m p o r a n e o u s pollen, it s e e m s t h a t this m a y h a p p e n f r e q u e n t l y (Brush, 1 9 6 6 ) so t h e A r d t u n s i t u a t i o n m a y n o t be so u n c o m m o n . A d a n g e r o u s s i t u a t i o n c o u l d t h e r e f o r e arise w h e n p a l y n o l o g i c a l d a t i n g o f a d e p o s i t is u n d e r t a k e n in t h e a b s e n c e o f o t h e r evidence, p a r t i c u l a r l y in the case o f cores. T h e possibility of e x t e n s i v e r e w o r k i n g s h o u l d be t a k e n into a c c o u n t w h e n a n y m a t e r i a l o t h e r t h a n p e a t , lignite or coal is e x a m i n e d . R e w o r k i n g , h o w e v e r , d o e s have a positive a p p l i c a t i o n in t h a t it can p r o v i d e useful geological i n f o r m a t i o n . T h e p r e s e n c e o f r e w o r k e d spores d e m o n s t r a t e s t h e f o r m e r e x i s t e n c e o f r o c k s o f t h a t age, and can i n d i c a t e at w h a t t i m e a n d to w h a t e x t e n t erosion has t a k e n place. ACKNOWLEDGEMENTS I a m very g r a t e f u l to P r o f e s s o r W. G. C h a l o n e r and Dr. M. D. Muir for t h e i r h e l p a n d advice. T h e m a t e r i a l f r o m t h e J. Starkie G a r d n e r c o l l e c t i o n was used b y kind p e r m i s s i o n o f t h e British M u s e u m ( N a t u r a l H i s t o r y ) , and t h e C r e t a c e o u s m a t e r i a l was p r o v i d e d b y Mr. W. Diver. This w o r k was carried o u t d u r i n g t h e t e n u r e o f a N.E.R.C. R e s e a r c h Fellowship. REFERENCES Andersen, S. T., 1954. A late-glacial pollen diagram from southern Michigan, U.S.A. Danm. geol. Unders., IV Rke, 2(80): 140--155. Argyll, Duke of, 1851. On Tertiary Leaf-beds in the Isle of Mull. With a note on the Vegetable Remains from Ardtun Head by E. Forbes. Q. dl. geol. Soc. Lond., 7: 89--103. Birks, H. J. B., 1970. Inwashed pollen spectra at Loch Fada, Isle of Skye. New Phytol., 69: 807--820. Brush, G. S., 1966. The absence of pollen and spores in some Triassic sediments. J. Paleontol., 40(5): 1241--1243. Cookson, I. C., 1955. The occurrence of Palaeozoic microspores in Australian Upper Cretaceous and Lower Tertiary sediments. Aust. J. Sci., 18: 56--58. Cushing, E. J., 1964. Redeposited pollen in late-Wisconsin pollen spectra from Eastcentral Minnesota. Am. J. Sci., 262: 1075--1088. Davis, M. B., 1961. The problem of rebedded pollen in late-glacial sediments at Taunton, Massachusetts. Am. J. Sci., 259: 211--222. Dembowski, Z. and Jachowiez, A., 1964. Redeposited coal fragments and pebbles in the sandstones of the Orzesze and {~aziska Beds in the Mi~dzyrzecze IG. borehole. Biul. Inst. Geol., 7(184): 125--176. Dijkstra, S. J., 1950. Carboniferous megaspores in Tertiary and Quaternary deposits of S.E. England. Ann. Mag. nat. Hist., Ser. 12, 3: 865--877.

231 Evans, A. L., Fitch, F. J. and Miller, J. A., 1973. Potassium--argon age determinations on some British Tertiary igneous rocks. J1. geol. Soc. Lond., 129: 419--443. Gardner, J. S., 1885. Eocene ferns from the basalts of Ireland and Scotland. J. Linn. Soc. Bot., 21: 655--664. Gardner, J. S., 1886. Monograph of the British Eocene Flora. Vol.2. Palaeontol. Soc. London, 159 pp. Gardner, J. S., 1887. On the leaf-beds and gravels of Ardtun, Carsaig, etc. in Mull, with notes by G. A. J. Cole. Q. J1. geol. Soc. Lond., 43: 270--300. Gardner, J. S. and Ettingshausen, C., 1882. Monograph of the British Eocene Flora. VoL1. Palaeontol. Soc. London, 86 pp. Geikie, A., 1896. The Tertiary basalt-plateaux of North-western Europe. Q. J1. geol. Soc. Lond., 52: 331--406. Havinga, A. J., 1967. Palynology and pollen preservation. Rev. Palaeobot. Palynol., 2: 81--98. Heer, O., 1859. Flora Tertiaria Helvetiae. Vol.3. Winterthur, 340 pp. Iversen, J., 1936. Sekund~ires Pollen als Fehlerquelle. Danm. geol. Unders., IV Rke., 2(15): 1--24. Jones, D. J., 1958. Displacement of microfossils. J. Sediment. Petrol., 28(4): 453--467. Kedves, M., Endr~di, L. and Szeley, Z., 1966. Probl~mes palynologiques concernant le remaniement des s6diments pal~o- et m~sozoiques dans les bassins du Pannonien sup~rieur de Hongrie. Pollen Spores, 8(2): 315--336. Lankford, R. R., 1953. Microfossils of the Wanship. In: Microfossils of the Upper Cretaceous of northeastern Utah and southwestern Wyoming. Utah Geol. Mineral. Surv. Bull., 47: 21--22. Lee, G. W. and Bailey, E. B., 1925. The Pre-Tertiary Geology of Mull, Loch Aline, and Oban. Mem. Geol. Surv. Scotl., 140 pp. Martin, A. R. H., 1968. Aquilapollenites in the British Isles. Palaeontology, 11: 54!)- 553. McLean, D. M., 1968. Reworked palynomorphs in the Paleoeene Naheola Formation of southwest Alabama. J. Paleontol., 42(6): 1478--1485. Muir, M. D., 1967. Reworking in Jurassic and Cretaceous spore assemblages. Rev. Palaeobot. Palynol., 5: 145--154. Muller, J., 1959. Palynology of the recent Orinoco delta and shelf sediments. Micropaleontology, 5: 1--32. Phillips, L., 1972. An application of fluorescence microscopy to the problem of derived pollen in British Pleistocene deposits. New Phytol., 71: 755--762. Richey, J. E., 1961. Scotland: The Tertiary Volcanic Districts. British Regional Geology, London, 3rd ed., 120 pp. Seward, A. C. and Holttum, R. E., 1924. Tertiary plants from Mull. In: E. B. Bailey, C. T. Clough, W. B. Wright, J. E. Richey and G. V. Wilson, The Tertiary and PostTertiary Geology of Mull, Loch Aline and Oban. Mere. Geol. Surv. Scotl., pp. 67--90. Simpson, J. B., 1961. The Tertiary Pollen-Flora of Mull and Ardnamurchan. Trans. R. Soe. Edinb., 64: 421--476. Stanley, E. A., 1965. Use of reworked pollen and spores for determining the Pleistocene-Recent and the Intra-Pleistocene boundaries. Nature, Lond., 206(4981): 289--291. Stanley, E. A., 1966a. The application of palynology to oceanology with reference to the northwestern Atlantic. Deep-Sea Res., 13: 921--939. Stanley, E. A., 1966b. The problem of reworked pollen and spores in marine sediments. Mar. Geol., 4(6): 397--408. Stanley, E. A., 1967. Palynology of six ocean-bottom cores from the southwestern Atlantic Ocean. Rev. Palaeohot. Palynol., 2: 195--203. Turnau, E., 1962. The age of coal fragments from the Cretaceous deposits in the Outer Carpathians, determined on microspores. Bull. Acad. Pol. Sci., S6r. Sci. G6ol. G6ogr., 10(2): 85--90.

232 Turner, C., 1970. The Middle Pleistocene deposits at Marks Tey, Essex. Philos. Trans. R. Soc. Lond., B257: 373--437. Van Gijzel, P., 1967. Autofluorescence of fossil pollen with special reference to age determination and coalification. Leidse geol. Meded., 40: 215--317. Watts, W. A., 1970. Tertiary and interglacial floras in Ireland. In: N. Stephens and R. E. Glasscock ('Editors), Irish Geographical Studies. In Honour of E. Estyn Evans. Queen's University, Belfast, pp. 17--33. West, R. G., 1956. The Quaternary deposits at Hoxne, Suffolk. Philos. Trans. R. Soc. Lond., B239: 265--356. Zagwijn, W. H., 1961. Vegetation, climate and radiocarbon datings in The Netherlands. Part I: Eemian and Early Weichselian. Meded. geol. Sticht. (N.S.), 14: 15--45.