Geological history

Sediments from deltaic and lacustrine deposits of Mid-Ordovician to Early Silurian age yield cryptospore monads, dyads, triads and tetrads. Nodospora has thickenings of sporoderm along the contacts between members of the tetrad. Some dyads and tetrads have

Box 13.1 Higher taxonomic categories and diagrams of representative genera found within the Turma Triletes, Suprasubturma Acavatitriletes

Subturma

Infraturma

Infraturma

Infraturma

Infraturma

AZONOTRILETES Wall of more or less uniform thickness

LAEVIGATI Wall more or less laevigate

Cyathidites

RETUSOTRILETI Proximo-equatorial surface curvaturate Retusotiletes

APICULATI

Wall sculptured with elongate to more or less isodiametric, non-murornate, positive elements

Subintra. GRANU LATI: wall ranulate

Granulatisporites

MURORNATI Wall more or less reticulated rugulate Appendicispo rites

Subintra. VERRUCATI: wallverrucate Verrucosisporites

Subintra. NODATI: wall echinate (spinose, conate) Dibolisporites

Subintra. BACULATI: wall baculate or pilate Raistrickia

Subturma

ZONOTRILETES Wall structurally differentiated equatorially and/or distally (e.g. cingulum, zona or patina present)

AURICULATI

TRICRASSATI

CINGULATI

With radial, equatorial With interradial equatorial With continuous equatorial modifications of wall (valvae, auriculae or radial appendages)

Tripartites extensions (coronae) or thickenings (interradial crassitudes)

Diatomozonotriletes thickening (cingulum), more or less membranous extension (zona), or combination of these (cingulizona)

Contignisporites

APPENDICIFERI Spores with appendages

Elaterites

Elaterites

LAGEOTRILETES Wall with proximal beak- or cone-like apical prominence (gula) or extension associated with laesurae Lagenicula

Box 13.2 Higher taxonomic categories and diagrams of representative genera found within the Turma Triletes, Suprasubturma Laminatitriletes (I), Suprasubturma Pseu dosaccititriletes and Suprasubturma Perinotriletes

Suprasubturma

Subturma

Infraturma

LAMINATITRILETES Wall cavate, but intexine in fairly close proximity to

AZONOLAMINATITRILETES Wall layers not differentially thickened or extended

TUBERCULORNATI Exoexine sculptured with such elements as grana, verrucae, coni, spinae, bacula, etc.

Hystricosporites

Hystricosporites

ZONOLAMINATITRILETES Wall layers not widely separated; sporoderm equatorially thickened and/or extended

CRASSITI

Wall equatorially crassitudinous, but not distinctly cingulate; e.g. Crassispora

CINGULICAVATI Exoexine equatorially thickened (cingulate) or extended (zonate); e.g. Densosporites

PATINATI

Distal hemisphere distinctly thicker than proximal: equatorial sporoderm may also be thickened; e.g. Tholisporites

Suprasubturma

Infraturma

Suprasubturma

PSEU DOSACCITITRILETES

Conspicuously cavate (pseudosaccate) spores, with intexine constituting more or less distinct inner body ('mesospore') within

MONOPSEUDOSACCITI Exoexine appears as a single comprehensive bladder-like inflation about intexinal body and separated from latter equatorially; cavum may extend over most or part of proximal and distal hemispheres; e.g.

Endosporites

POLYPSEUDOSACCITI Separation and inflation of exoexine from intexine variable equatorially to produce three or more pseudosacci; e.g.

Dulhuntyspora

PERINOTRILITES

Exospore enveloped by a perimous or episporous layer; e.g. Crybelosporites

Box 13.3 Higher taxonomic categories and diagrams of representative genera found within the Turma Monoletes, Subturmas Azonomonoletes, Zonomonoletes and Cavatomonoletes, and the Turmas Hilates, Aletes and Cystites

Turma: MONOLETES

Subturma

Infraturma

Subturma

AZONOMONOLETES Wall of more or less uniform thickness

LAEVIGATOMONOLETI Wall laevigate

Laevigatisporites

SCULPTATOMONOLETI Wall sculptured

Polypodiidite

ZONOMONOLETES Wall with equatorial thickening or extension. These are very uncommon. Speciosporites is the spore of Pecopteris

Subturma

Turma: HILATES

Turma: ALETES

Turma: CYSTITES

CAVATOMONOLETES Wall cavate

Spores hilate; i.e. with proximal or distal hilum

Subturma: AZONOALETES

Fabosporites

Includes large megaspores produced by arborescent lycopods

Aratrisporites

Aequitriradites

Cystosporites

a membrane that encloses the whole unit. Rocks of Llandovery age yield the first spores with conspicuous trilete marks, typified by Ambitisporites spp. (Fig. 13.12b). Palynological preparations of this age can also contain tubes and sheets of cuticle that may represent debris from the first subaerial plants. The first macroplant remains of Cooksonia are found in deposits of Late Silurian age. From this time onwards the number of macroplant fossils and spore types found increases dramatically, reflecting a major diversification in primitive plants. By the Ludlow approximately 10 spore genera are present. The parent plants of these early spores appear to have had cosmopolitan distributions.

The Devonian probably marks the acme of pterido-phytic plants with the appearance of primitive members of the lycophytes (e.g. Zosterophyllum and Baragwathania), the trimerophytes (e.g. Psilophyton) and possible sphenopsids (e.g. Protohyenia). These were joined in the Emsian by the progymnosperms which produced true seeds and pollen grains by the Late Famenian. Initially these primitive pollen grains were indistinguishable from trilete miospores and as a result have been called pre-pollen. Increasing provinciality during the Devonian led to distinct equatorial-low latitude (North American-Eurasian), Australian and southern Gondwana floras. This increase in provincialism may have been a response to the greater latitudinal spread of the Devonian continents or global cooling associated with the onset of glacial conditions. By the Siegenian microspores had increased in size to 100 |im (e.g. Ancyrospora, Fig. 13.12c) and by the Emsian to 200 |im. Cysto-sporites (Fig. 13.12d) can be over 1 cm in maximum dimension. It comprises one large and three aborted spores and may have functioned as a 'seed megaspore'. The importance of true megaspores seems to have declined after the Carboniferous, until the Jurassic and especially the Cretaceous when they may be common again in non-marine deposits.

Box 13.4 Higher taxonomic categories (mainly subturma level) and diagrams of representative genera of saccate spores and pollen

1

Subturma

Infraturma

MONOSACCITES

TRILETESACCITI: includes ALETESACCITI: pollen pollen of cycads, seed ferns primitive conifers and cordaitean pre-pollen .

■ " Florinites Schulzosporas

f VESICULOMONORADITI: cycadofilicalean pollen

Potonieisporites

DISSACITES

DISACCITRILETI: coniferalean DISACCIATRILETI: medullosan pollen pollen

Illinites Pityosporites

Subturma

Subturma Subturma

Subturma

STRIATITES: glossopterid and early conifer pollen

Luekisporites

PRAECOLPATES: medullosan POLYPLICITES: seed-fern pollen gnetalean pollen

Vittatina

MONOCOLPITES: pollen of various members of the ginkgos and cycads

Moncolpopollenites

Carboniferous floras are extremely well known due largely to extensive coal deposits. They included a wealth of arborescent, heterosporous lycopsids, no doubt liberating clouds of Lycospora (Fig. 13.13b), Lagenicula and other spined spore species into the air. The horsetails (with Calamospora Fig. 13.12e, Laevigatosporites Fig. 13.12f, Reticulatisporites Fig. 13.13e), seed ferns (with spores and bisaccate pollen) and cordaitaleans (with Florinites pollen, Fig. 13.12g) were also important elements. Carboniferous coal swamps were characterized by lycopsids including the well-known Lepidodendron and Sigillaria, seed-fern trees and shrubs including Medullosa, sphenopsid trees and shrubs including Calamites, and shrub cordaitaleans such as cordaites which comprised primitive conifers. Tropical deltas have been used to provide analogues for Carboniferous coal swamps (Scheihning & Pfefferkorn 1984). Many sporeplant associations are known for the Carboniferous. Some plants produced more than one spore type in the same microsporangium. For example, Densosporites (Figs 13.12h, 13.13a), commonly found in coal seams, is associated with several Carboniferous lycopsids such as Porostrobus and Sporangiostrobus and the Devonian lycopsid (?) Barrandeina.

By the Permian the seed and pollen habit of the gymnosperms had become the dominant life cycles and pollen grains increasingly replace spores in Meso-zoic palynological assemblages, particularly from mid-Cretaceous onwards, following the early evolution of the angiosperms.

How Are Spores Released Diagram

Fig. 13.12 Diagrammatic representation of spores and pollen grains mentioned in the text. (a) Tetrahedrales, a cryptospore, x500. (b) Ambitisporites, x1000. (c) Ancyrospora, x50. (d) Cystosporites, x30. (e) Calamospora, x1000. (f) Laevigatosporites, x350. (g) Florinites, x350. (h) Densosporites, x380. (i) Potonieisporites, x220. (j) Schulzospora, x475. (k) Wilsonites, x670. (l) Pityosporites, x915. (m) Illinites, x420. (n) Protohaploxypinus, x500. (o) Lueckisporites, x560. (p) Vittatina, x320. (q) Ephedra, x1150. (r) Corollina, x1600. (s) Clavatipollenites, x1000. (t) Eucommiidites, x1200. (u) Tricolpites, x500. ((a), (b) After Richardson in Jansonius & McGregor 1996, pp. 555-575); (f)-(j) after Clayton in Jansonius & McGregor 1996, vol. 2, pp. 589-597; (k), (u) after Tschudy & Scott 1969; (l)-(s) after Traverse 1988.)

Fig. 13.12 Diagrammatic representation of spores and pollen grains mentioned in the text. (a) Tetrahedrales, a cryptospore, x500. (b) Ambitisporites, x1000. (c) Ancyrospora, x50. (d) Cystosporites, x30. (e) Calamospora, x1000. (f) Laevigatosporites, x350. (g) Florinites, x350. (h) Densosporites, x380. (i) Potonieisporites, x220. (j) Schulzospora, x475. (k) Wilsonites, x670. (l) Pityosporites, x915. (m) Illinites, x420. (n) Protohaploxypinus, x500. (o) Lueckisporites, x560. (p) Vittatina, x320. (q) Ephedra, x1150. (r) Corollina, x1600. (s) Clavatipollenites, x1000. (t) Eucommiidites, x1200. (u) Tricolpites, x500. ((a), (b) After Richardson in Jansonius & McGregor 1996, pp. 555-575); (f)-(j) after Clayton in Jansonius & McGregor 1996, vol. 2, pp. 589-597; (k), (u) after Tschudy & Scott 1969; (l)-(s) after Traverse 1988.)

Striatopodocarpites

Fig. 13.13 Photomicrographs of selected spores and pollen. (a) Densosporites annulatus, a Lepidodendron spore found within Sporangiostrobus and Porostrobus cones, Westphalian B, distal view, x500. (b) Lycosporapusilla, a Lepidodendron spore found within the Lepidostrobus cone, Westphalian A, proximal view, x530. (c) SEM photomicrograph of Tuberculatisporites triangulates, Westphalian B, proximal view, x16. (d) Striatopodocarpites sp., Permian, x415. (e) Reticulatisporites cancellatus, Visean, x247. (f) Nothofagidites brassi-type, pollen of the Southern Beech, Santonian, x600. (g) Appendicisporites cfA. potomacensis, Cenomanian, x287. (h) Clavatipollenites hughesii, Cretaceous, x695. ((c)-(f) From Traverse 1988 (with the permission of the AASP Foundation); (g) from Playford & Dettmann in Jansonius & McGregor 1996, plate 1, figure 12 (with the permission of Kluwer Academic Publishers).)

Fig. 13.13 Photomicrographs of selected spores and pollen. (a) Densosporites annulatus, a Lepidodendron spore found within Sporangiostrobus and Porostrobus cones, Westphalian B, distal view, x500. (b) Lycosporapusilla, a Lepidodendron spore found within the Lepidostrobus cone, Westphalian A, proximal view, x530. (c) SEM photomicrograph of Tuberculatisporites triangulates, Westphalian B, proximal view, x16. (d) Striatopodocarpites sp., Permian, x415. (e) Reticulatisporites cancellatus, Visean, x247. (f) Nothofagidites brassi-type, pollen of the Southern Beech, Santonian, x600. (g) Appendicisporites cfA. potomacensis, Cenomanian, x287. (h) Clavatipollenites hughesii, Cretaceous, x695. ((c)-(f) From Traverse 1988 (with the permission of the AASP Foundation); (g) from Playford & Dettmann in Jansonius & McGregor 1996, plate 1, figure 12 (with the permission of Kluwer Academic Publishers).)

The pteridosperms or seed ferns were the first plants to produce pollen. They evolved from the pterido-phytes, although the exact nature of this event is unclear; the heterosporous pteridophytes were probably an intermediate stage in their emergence. The oldest known pollen, termed pre-pollen, dates from the Late Devonian (Famenian). Chaloner (1970) provided a summary of the morphological differences between spores, pre-pollen and pollen. Gymnosperm pollen with distal germination is first found in Upper Carboniferous deposits. A large number of gymno-sperm pollen types evolved in the later Palaeozoic. Saccate pollen grains are the most easily recognized of these and are common among many groups, including the extinct pteridosperms and conifers and cordaitaleans. Monosaccate grains were more common than bisaccates during the Carboniferous, Early Permian and Late Triassic. Carboniferous and Permian genera include Florinites, Potonieisporites (coniferalean pollen, Fig. 13.12i), Schulzospora (pteridosperm pre-pollen, Fig. 13.12j) and Wilsonites (cycad pollen, Fig. 13.12k). Upper Palaeozoic bisaccate conifer pollen grains include Pityosporites (Fig. 13.12l) and Illinites (Fig. 13.12m).

A number of Carboniferous to Triassic gym-nosperms produced striate bisaccate pollen grains. Permo-Triassic examples include Protohaploxypinus (Fig. 13.12n), Lueckisporites (Fig. 13.12o) and Vittatina (Fig. 13.12p). Most modern gnetalean gymnosperms produced striate, but non-saccate (polyplicate) grains. A modern example is Ephedra (Fig. 13.12q). The fossil record of Ephedra-like pollen extends from the Mesozoic to the present day.

Circumpolles pollen is unique to certain extinct gymnosperms. These grains have a circumpolar subequatorial groove that divides the grain into two unequal halves, which bear a distal pseudopore and a proximal triangular area. Corollina (=Classopollis, Fig. 13.12r) is the most well known example. It was produced by a now extinct coniferalean group, the Cheirolepidiaceae. Pollen of this type is common from the mid-Triassic to the mid-Cretaceous. Monosulcate grains are found in cycads and related groups, and are most common in Jurassic samples. Simple monosulcate pollen grains (e.g. some species of Eucommiidites, Fig. 13.12t), though resembling primitive angiosperm, pollen were not produced by this group of plants.

Angiosperms evolved from a group of advanced gymnosperms, though the precise relationships are controversial. Angiosperm pollen characteristics include a non-laminate endoexine and a fully differentiated ektexine and many angiosperm pollen grains are triaperturate. The palynological record suggests the angiosperms arose during the Early Cretaceous (Hughes 1976; Hughes & McDougall 1987). Several Late Triassic genera (Crinopolles group) have exines of similar structure, but there is no megafossil evidence to support a pre-Cretaceous age for the angio-sperms. Clavatipollenites hughesii (Barremian, Lower Cretaceous, Figs 13.12s, 13.13h) is one of the earliest angioperm pollen grains; it is monosulcate and has a columellate, tectate exine. Tricolpites first appeared in the Albian (Fig. 13.12u) and probably evolved from a Clavatipollenites-type ancestor (Chaloner 1970); other tricolpate pollen arose in equatorial latitudes in the Aptian and spread to mid-latitudes by the Albian and polar regions by the Cenomanian (Hickey & Doyle 1977). Either changes in palaeoclimate and palaeogeography may have controlled this geographical spread, or plants evolved rapidly and migrated into cooler latitudes.

The appearance of tricolpate pollen was a major evolutionary innovation and this, plus a seed protected by carpels, was among the reasons for the success of the earliest angiosperms. All the structural features found in modern pollen grains had evolved by the end of the Cenomanian. As angiosperms diversified during the Late Cretaceous they became more provincial in their distribution (Batten 1984).

The modern flora emerged gradually from the Neogene onwards mainly by extinction of relict Cretaceous and Palaeogene species. Two new modern groups that became widespread in the mid-Tertiary are the Asteraceae (the composites) and the Poaceae (the grasses). They arose as a consequence of climate deterioration and have become the most successful of the modern groups, with a vast number of living species. The morphology of their pollen is very different because the grasses are anemophilous and the composites entomophilous. The pollen of the grasses is simple spheroidal and monoporate and is the major cause of hayfever.

The structure of modern plant communities has developed since the last ice age and due to the influence of man some communities have only became established in the last 200 years.

Applications of fossil spores and pollen

Spores and pollen provide a continuous record of the evolutionary history of the vascular plants. Spores were first utilized economically in coal-seam correlation and biostratigraphy (Smith & Butterworth 1967, and references therein) and now have wide-ranging uses in source rock provenance and palaeoenviron-mental, palaeoecological and phytogeographical studies.

Silurian to Carboniferous palynozonations are based on spores; pollen grains are more important for dating and correlating younger rocks. Palynozonations can be found for the Silurian in Richardson (in Jansonius & McGregor 1996, vol. 2, pp. 555-575), the Devonian in Streel & Loboziak (in Jansonius & McGregor 1996, vol. 2, pp. 575-589), the Lower Carboniferous in Clayton (in Jansonius & McGregor 1996, vol. 2, pp. 589-597), the Upper Carboniferous in Owens (in Jansonius & McGregor 1996, vol. 2, pp. 597-607), the Permian in Warrington (in Jansonius & McGregor 1996, vol. 2, pp. 607-621) and the Mesozoic and Cenozoic in Batten & Koppelhus (in Jansonius & McGregor 1996, vol. 2, pp. 795-807), Batten (in Jansonius & McGregor 1996, vol. 2, pp. 807-831, 1011-1065) and Friederiksen (in Jansonius & McGregor 1996, vol. 2, pp. 831-843).

Spores and pollen grains are widely utilized in hydrocarbon exploration through thermal maturity studies (Thermal Alteration Index (TAI) and equivalents) and palynofacies analysis (Batten 1996 in Jansonius & McGregor 1996, vol. 3, pp. 1011-1085).

Quantitative spore studies in the 1950s and 1960s demonstrated a clear relationship between spore content and rock type in Carboniferous cyclothems, reflecting changes in vegetation and palaeoenviron-ments (Smith, 1962, 1968; Chaloner 1968; Eble in Jansonius & McGregor 1996, vol. 3, pp. 1143-1156). Spores and pollen in association with other paly-nomorphs have an application in delimiting palaeo-shorelines (e.g. Frakes et al. 1987) and provenance through recycling (Collinson et al. 1985).

Pollen analysis

Pollen analysis involves the quantitative examination of spores and pollen at successive horizons through a core, particularly in bog, marsh, lake or delta sediments. This method yields remarkable information on regional changes in vegetation through time, especially in Quaternary sediments where the parent plants are well known, though similar techniques have been used with success in older deposits such as Carboniferous coals. More complete reviews of Quaternary palyno-logy can be found in MacDonald (in Jansonius & McGregor 1996, vol. 2, pp. 879-910). Specific methods

Radial Diagrams Glacial Deposits
Fig. 13.14 Generalized pollen diagram from the Ipswichian (or Eemian) interglacial deposits. Pollen types are illustrated in Fig. 13.15. AP, arboreal pollen; NAP, non-arboreal pollen. (After West & Pearson, in Tschundy & Scott 1969, modified from figures 17-19.)

and areas of research can be found in Birks & Birks (1980), Faegri & Iversen (1989) and Moore et al. (1991).

The relative frequencies of different spore and pollen types are calculated for each of a number of closely spaced sample horizons through the core. Tree pollen (e.g. pine, oak, elm, beech, Fig. 13.11h-m) is often summed together, whilst the non-tree or non-arboreal pollen (NAP, e.g. herbs, grasses) may be documented separately, although expressed as a percentage in relation to the tree pollen. Spores and pollen (e.g. those of sedges, grasses and heather) from bog, heath and lake-vegetation may also be expressed independently, but again in relation to tree pollen. The pollen spectra of each species are then arranged alongside to give a pollen diagram of palynological changes through the core (Fig. 13.14).

Such diagrams invariably give a biased impression of the flora. Apart from the adverse effects of dispersal, the frequency of flowering or dehiscence, the number of sporangia, cones or flowers, their position relative to the dispersal agencies and the preservation potential of various spores and pollen all have some influence on pollen counts. A large number of statistical techniques are available for analysing pollen data in order to quantify changes in vegetation, rates of migration and vegetation reconstruction through time.

Pollen has been most widely applied in the correlation and palaeoecology of Quaternary deposits. For example, the familiar divisions of the British Recent from Pre-Boreal with birch woodland (about 10,000 years BP) to Sub-Atlantic alder-oak woodland (modern) were based on changing pollen spectra (see West

1968, pp. 279-283, 292-325). Most Quaternary interglacial deposits in temperate latitudes record a change from glacial to cool birch forest with abundant small herbs and shrubs in the late glacial, through pine forest, to a climatic optimum with elm, oak, lime, alder and hazel, followed by a climatic deterioration with pine, birch and then renewed glacial conditions. In England the Flandrian pollen diagram is rather atypical of the Atlantic region because it shows a birch decline at 8500 years BP. At more remote periods the causes of microfloral changes are less certain but ecological successions and biofacies can be recognized (Traverse 1988). A typical Devensian pollen assemblage is shown in Fig. 13.15 with the arboreal component dominated by pine and beech pollen. In North America the continent is too large and the vegetation too variable to produce the same sort of pollen diagrams as for European sections. Classic examples of the influence of Quaternary and Recent climate change on North American vegetation can be found in Davis etal. (1980) and Watts (1979), and the effect these changes had on animal populations in Whitehead et al. (1982). Comparison of climate models and pollen-derived estimates of climate can be found in Webb et al. (1998).

Pollen analysis is also of great assistance to archaeologists, not only because it provides a stratigraphical framework for the Late Quaternary but because of the view it gives of man's early environment and his effect upon it. There was, for example, a curious sudden decline in the tree pollen at the horizon of the late-middle Acheulian (Palaeolithic) hand axe culture in the Hoxnian interglacial (West, in Tschudy & Scott

1969, p. 421) that might have been due to forest clearance. The appearance of human-introduced weeds

Fig. 13.15 A typical pollen assemblage of the Wurmian cold stage (equivalent to the Devensian in Britain and the Wisconsian in central North America) deposits, St Front, France. The arboreal component includes (a) Pinus, (b) Picea, (c) Betula and (d) Cedrus. The non-arboreal component includes (e) Helianthemum (long axis 45 |m), (f) Plantago, (g) Ephedra, (h) Calluna and pollen from the families (i) Caryophyllaceae, (j) Chenopodiaceae, (k) Poaceae/Gramineae and (l) Liliaceae. (Photomontage from Lowe & Walker 1997, figure 4.1, originally composed by M. Reille and V. Andrieu, reproduced with the permission of Longman, London.)

Fig. 13.15 A typical pollen assemblage of the Wurmian cold stage (equivalent to the Devensian in Britain and the Wisconsian in central North America) deposits, St Front, France. The arboreal component includes (a) Pinus, (b) Picea, (c) Betula and (d) Cedrus. The non-arboreal component includes (e) Helianthemum (long axis 45 |m), (f) Plantago, (g) Ephedra, (h) Calluna and pollen from the families (i) Caryophyllaceae, (j) Chenopodiaceae, (k) Poaceae/Gramineae and (l) Liliaceae. (Photomontage from Lowe & Walker 1997, figure 4.1, originally composed by M. Reille and V. Andrieu, reproduced with the permission of Longman, London.)

marks the onset of agriculture, and the spread of heath in Scotland indicates the clearing of forest for grazing (Traverse 1988). Godwin (1967) even outlined the remarkable evidence for cultivation of Cannabis in England by Saxons, Normans and Tudors. Leroi-Gourham (1975) showed that 50,000 years BP Neanderthals buried their dead on a blanket of flowers. Palynologists have also studied gut contents and coprolites of various animals to reveal diets and changing climatic conditions at the time. An excellent review of archaeological palynology can be found in Dimbleby (1985).

Pollen and spores can also help sedimentologists to discover the provenance of fine-grained sediments.

Sediment samples from the Mississippi delta contain both local and reworked pollen and spores from Devonian upwards. Carboniferous spores are abundant in Recent sediments of the northeast coast of England. Collinson et al. (1985) reported reworking of Palaeozoic and Mesozoic megaspores into the Paleocene deposits of southern England. Needham et al. (1969) used reworked Carboniferous paly-nomorphs as tracers of sedimentation patterns in the northwest Atlantic. As with other fossils, pollen and spores can be used to estimate the rate of sedimentation (see Davis 1968).

Although reworking may be a natural hazard for palynologists, Stanley (1967) showed how horizons rich in reworked miospores can be used as correlation markers in deep sea sediments, in this case corresponding with glacial maxima and periods of greatly lowered sea level. Traverse (1974) also noted that reworked spores and pollen were most abundant in Black Sea surface sediments that were deposited during the last glacial maximum. He suggested this was due to rejuvenation and increased erosion as sea levels fell.

Further reading

Invaluable introductions are available in Traverse (1988) and Jansonius & McGregor (1996, 3 volumes). A review of megaspores can be found in Scott & Hemsley (in Jansonius & McGregor 1996, vol. 2, pp. 629-641). Quaternary palynology is reviewed in Lowe & Walker (1997) and (Bradley 1999) and pollen analysis by Moore et al. (1991). Further information on palynology can be found at the International Federation of Palynological Studies website http:// geo.arizona.edu/palynology/ifps.html and by following the links to other learned societies.

Hints for collection and study

To understand the morphology of fossil spores and pollen, it is particularly worthwhile looking at living material. A collection of common spore and pollen types from trees, shrubs and ferns can readily be made by removing the flowers, cones or sporangia when just on the point of opening. If not examined directly they should be stored in alcoRec. Strew slides can be made by removing the anthers, pollen sacs or sporangia with a scalpel and placing these on a glass slide with a drop of distilled water. While looking down a microscope, bruise the anthers, etc. with a seeker or the blunt edge of a scalpel and spread the released grains over part of the slide. To make the structures more distinct, allow the strew to dry and then add a drop of Gray's spore stain (0.5% malachite green and 0.05% basic fuschin in distilled water; the slide should then be warmed for 1 minute), or basic fuschin stain (0.5% basic fuschin in distilled water) or safranin stain (1 g of safranin 'O' in

50 ml of 95% alcohol plus 50 ml of distilled water). After 10 minutes rinse the slide with a little distilled water and dry at a low temperature. Mount the cover slip with water or glycerine (30% aqueous solution) for temporary preparations, or in Canada Balsam for permanent ones. View with well-condensed transmitted light at 400X magnification or higher. Berglund (1986) contains useful sections on field and laboratory techniques.

Fossil miospores are most readily prepared from plant-bearing muds or shales and from peats, lignites and coals. They can also be very abundant in dark marine shales and mudstones. Palynological laboratories invariably remove the siliceous material with hydrofluoric acid, the calcareous material with hydrochloric acid and the vegetative plant tissues with a variety of strong acids, alkalis and oxidants. Spores and pollen grains can be prepared for study without these sophisticated techniques but the results are inevitably diluted with mineral and vegetable matter. Disaggregation should follow methods A to F (see Appendix), wash as in method G and concentrate as in method H or K. If the organic material is dark and opaque, treat with method E. Temporary mounts in water or glycerine and permanent mounts in glycerine jelly or Canada Balsam can be prepared on glass slides.

Examine the strewn slide with well-condensed transmitted light, using oil immersion objectives for the higher magnifications if possible. Microspores can usually be distinguished from other vegetable matter by their shape, their sharper outlines and often by their amber colour. Much information on palynological techniques can be found in Gray (in Kummel & Raup 1965, pp. 470-706) and in Jones & Rowe (1999).

REFERENCES

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Chaloner, W.G. 1968. The palaeoecology of fossil spores. In: Drake, E.T. (ed.) Evolution and Environment. Yale University Press, New Haven, Conneticut, pp. 125-138.

Chaloner, W.G. 1970. The rise of the first land plants. Biological Reviews 45, 353-377.

Collinson, M.E., Batten, D.J., Scott, A.C. & Ayonghe, S.N. 1985. Palaeozoic, Mesozoic and contemporaneous mega-spores from the Tertiary of southern England: indicators of sedimentary provenance and ancient vegetation. Journal of the Geological Society, London 142, 375-395.

Davis, M.B. 1968. Pollen grains in lake sediments: redeposition caused by seasonal water circulation. Science 162, 796-799.

Davis, M.B., Spear, R.W. & Shane, L.C.K. 1980. Holocene climate of New England. Quaternary Research 14, 240250.

Dimbleby, G. 1985. The Palynology of Archaeological Sites. Academic Press, London.

Erdtman, G. 1986. Pollen Morphology and Plant Taxonomy: angiosperms - an introduction to palynology. E.J. Brill, Leiden.

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Frakes, L.A. with 21 other authors 1987. Australian Cretaceous shorelines, stage by stage. Palaeogeography, Palaeoclimatology, Palaeoecology 59, 31-48.

Godwin, H. 1967. Pollen analytic evidence for the cultivation of Cannabis in England. Review of Palaeobotany and Palynology 4, 71-80.

Gray, J. 1985. The microfossil record of early land plants: advances in understanding of early terrestrialization, 1970-1984. Philosophical Transactions of the Royal Society of London B309, 167-195.

Greuter, W. & Hawksworth, D.L. (eds) 2001. International Code of Botanical Nomenclature (Tokyo Code). Also online at http://www.bgbm.fu-berlin.de/iapt/nomenclature/code/ SaintLouis/0001ICSLContents.htm).

Hickey, L.J. & Doyle, J.A. 1977. Early Cretaceous fossil evidence for angiosperm evolution. Botanical Review 43, 3 -104.

Hughes, N.F. 1976. The challenge of abundance in paly-nomorphs. Geoscience and Man 11, 141-144.

Hughes, N.F. 1989. Fossils as Information: new recording and stratal correlation techniques. Cambridge University Press, Cambridge.

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Jansonius, J. & Hills, L.V. 1976 et seq. Genera File of Fossil Spores. Department of Geology and Geophysics, University of Calgary; Alberta. special publication, with 11 supplements.

Jansonius, J. & McGregor, D.C. (eds) 1996. Palynology: principles and applications, vols 1-3. American Association of Stratigraphic Palynologists, Dallas.

Jones, T.P. & Rowe, N.P. (eds) 1999. Fossil Plants and Spores: modern techniques. Geological Society, London.

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Schraudolf, H. 1984. Ultrastructural events during sporogen-esis of Anemia phyllitidis (L.) Sw. Beiträge zur Biologie der Pflanzen 59, 237-260.

Smith, A.V.H. 1962. The palaeoecology of Carboniferous peats based on the miospores and petrography of bitu-menous coals. Proceedings. Yorkshire Geological Society 33, 423-474.

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Traverse, A. 1988. Paleopalynology. Unwin Hyman, Boston. Tschudy, R.H. & Scott, R.A. (eds) 1969. Aspects of Palynology.

Wiley-Interscience, New York. Uehara, K., Kurita, S., Sahashi, N. & Ohmoto, T. 1991. Ultrastructural study on microspore wall morphogenesis in Isoetes japonica (Isoetaceae). American Journal of Botany 78, 1182-1190.

Watts, W.A. 1979. Late Quaternary vegetation of central Appalachia and the New Jersey coastal plain. Ecological Monographs 49, 427-469.

Webb, T., Anderson, K.H., Bartlein, P.J. & Webb, R.S. 1998. Late Quaternary climate change in eastern North America: a comparison of pollen-derived estimates with climate model results. Quaternary Science Reviews 17, 587-606.

West, R.G. 1968. Pleistocene Geology and Biology, with Special Reference to the British Isles. Longman, London.

Whitehead, D.R., Jackson, S.T., Sheehan, M.C. & Leyden, B.W. 1982. Late-glacial vegetation associated with caribou and mastodon in central Indiana. Quaternary Research 17, 241-257.

PART 4

Inorganic-walled microfossils

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Responses

  • leon bosch
    How are spores released diagram?
    8 years ago
  • WEGAHTA
    What is geolagic histroy of each group about micropalaeontology?
    3 years ago

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