Regional Pollen Assemblage Zones Research Articles

Palaeobotanical record of the Eemian Interglacial succession at the Jagodne site (Garwolin Plain, central Poland)

Our high-resolution data of pollen and macrofossils from 2 cores taken from the Jagodne site (Garwolin Plain) reveals a pollen succession covering the final part of the Late Saalian (Marine Isotope Stage MIS 6) and embracing the Eemian (MIS 5e). The results correspond to Regional Pollen Assemblage Zones (RPAZ). The hornbeam phase (E5 RPAZ) has been subdivided into subzones and compared to the corresponding division of the key profile of the Garwolin Plain, Kozłów K2-19. The comparison revealed a considerable sedimentary hiatus in the E5 RPAZ at Jagodne. This is attributed to significant palaeohydrological changes occurring widely in this zone, and also seen at other Eemian sites in Poland. Another specific feature of the Jagodne site is the early, rapid terrestrialisation of the palaeolake and its transformation into a raised bog, which occurred already at the end of the hornbeam phase. The Sphagnum dominated peatbog developed for a long time as evidenced by a thick peat layer covering also the Early Vistulian. Both pollen and plant macrofossil data correspond well to observed lithological boundaries, providing a consistent record of palaeoenvironmental and palaeoclimate changes. The results obtained contribute to knowledge of palaeoenvironmental changes and palaeoclimate interpretation of that area.

A Last Interglacial speleothem record from the Sieben Hengste cave system (Switzerland): Implications for alpine paleovegetation

A precisely dated speleothem isotope record from the Sieben Hengste cave system, Switzerland, reveals a Last Interglacial (LIG) climate optimum centred at 128.1 ± 1.2 ka. The oxygen isotope signal is consistent with a temperature-dominated record and shows a strong correlation with the modelled Greenland δ18O signal. The comparison with speleothems formed during the Last Glacial Maximum (LGM) in the same cave indicates a 4–5‰ difference in δ18O between peak LIG and peak LGM conditions, suggesting peak LIG temperatures being up to 3 °C higher than the Holocene average. Pollen extracted from the stalagmite indicates a vegetation response delayed by up to 3 ka with maximum pollen concentrations recorded at 125 ± 2.2 ka. Our results support a regional vegetation dominated by thermophile tree species including Corylus (hazel), Quercus robur-type (oak), Ulmus (elm), Tilia (lime tree) and Hedera (ivy), consistent with slightly warmer conditions than today. Despite the relatively low pollen concentration, the speleothem-based pollen spectra are consistent with regional pollen assemblage zones from paleolake sediments and provide the first direct paleovegetation evidence of thermophilization during the LIG at high altitudes in the Alps.

Last Interglacial (Eemian) hydrographic conditions in the southeastern Baltic Sea, NE Europe, based on dinoflagellate cysts

A rich organic-walled dinoflagellate cyst and pollen record from the Licze borehole in northern Poland has been used to reconstruct the hydrographic history of the southeastern Baltic Sea during the Last Interglacial (Eemian Stage, Late Pleistocene). Warm, saline waters (ca. 10–15 psu) entered the site from the North Sea within the first few hundred years of the Eemian, corresponding to the Pinus–Betula (E1) or Pinus–Betula–Ulmus (E2) regional pollen assemblage zones (RPAZ). By about 300 years (beginning of RPAZ E3), dinoflagellate cyst assemblages were already indicating summer sea-surface salinities in excess of about 15 psu and temperatures that perhaps exceeded 27°C. Warm and saline conditions of 15–20 psu or more, at least twice present levels, persisted throughout the early Eemian. A rise in sea level at Licze appears to correlate with a similar event in eastern Denmark, as both coincide with the increase in Corylus (ca. 750 years into the interglacial). This sea-level rise might therefore have a basinwide extent, and appears to correspond to an opening of the Danish Belts. There is little if any evidence of arctic waters throughout the sequence. Whereas dinoflagellate cysts reflect sustained high salinites within the upper water column, a concomitant increase in abundance of the chlorococcalean alga Pediastrum within the Carpinus–Corylus–Alnus (E5) RPAZ indicates an escalating freshwater input, presumably from the proto-Vistula whose mouth was nearby. This suggests the development of a thin, seasonal, low-salinity surface layer below which dinoflagellates lived in more saline waters. Increasing fluvial influence suggests shallowing through RPAZ E5. This study is the first to document dinoflagellate cysts from the Eemian of the southeastern Baltic Sea, and reveals a flora with distinctive Lusitanian/Mediterranean affinities.

Correlation of stadial and interstadial events in the south Swedish glacial varves with the GRIP oxygen isotope record

A number of correlated varve sequences from the local varve chronology in southeastern Sweden have been selected to make a 1040 varve years long mean varve thickness curve. Pollen analyses were carried out over an interval of 373 varve years in the northern part of the study area. The pollen stratigraphical data have been divided into local pollen assemblage zones which have been correlated with the radiocarbon‐dated regional pollen assemblage zones. Based on variations in herb and tree pollen content of the analysed varve sequences, it has been possible to identify well‐documented lateglacial pollen zones for southern Sweden, i.e. the Bölling interstadial (GI‐1e), the Older Dryas cold event (GI‐1d) and the early part of the Alleröd interstadial (GI‐1c). The event stratigraphy in this study, based on varying varve thicknesses and the composition of the pollen flora in the varves, has been correlated with the oxygen isotope stratigraphy of the GRIP ice‐core on Greenland between 13600 and 14400 GRIP ice‐core years BP. It is concluded that five decadal warm events and one centennial warm event (15–60 and 100 varve years long, respectively) occur in the clay varve record along with one centennial cold event (150 varve years long), the Older Dryas (GI‐1d).

Lateglacial and Early Holocene vegetation history of the northern Wetterau and the Amöneburger Basin (Hessen), central-west Germany

The Lateglacial and Early Holocene vegetation history of the northern Wetterau and Amöneburger Basin, two intra-montane basins in Hessen, central-west Germany, is reconstructed by means of pollen and macrofossil analyses. Regional pollen assemblage zones are defined for the Lateglacial and Early Holocene. After calibration of the radiocarbon dates and establishment of age/depth relationships, the ages of the pollen zone boundaries are calculated. The regional vegetation changes correlate closely with the major fluctuations in the δ 18O curve of the Greenland ice cores spanning the same time period. During the early Lateglacial, the open herbaceous vegetation with dwarf shrubs in the northern Wetterau was replaced by woodlands. Initially these woodlands consisted of birch, but after the immigration of pine, mixed forests of pine and birch developed. Soon after its immigration pine became dominant and pine woodlands largely replaced the birch forests. Only on the locally wetter substrates of the river floodplain did Betula stands persist. Gradually the importance of herbaceous communities declined and the pine woodlands lost their open character. During the Lateglacial two regressive phases in the vegetation succession are reflected in the data which are equated with the Older- and Younger Dryas biozones. At the beginning of the Younger Dryas, the forest-limit was lowered and the importance of herbaceous communities increased. Later, pine woodlands thinned and Ericales became part of the vegetation, indicating the development of more acid, nutrient-poor soils. A subdivision of the Younger Dryas biozone into a wetter, colder first part and a drier, warmer second part is suggested. At the beginning of the Early Holocene, pine woodlands became more closed and soils more stabilised. The transition between the Younger Dryas and Preboreal biozones is indicated by a lithological change to organic (-rich) deposits. Betula stands persisted on the locally wetter substrates of the fluvial plains. At the end of the early Preboreal, there was an extension of Betula stands on the river floodplains. This is interpreted as a phase in which climate was temporarily wetter, perhaps a reflection of a short-term climatic oscillation, the so-called Preboreal oscillation. During the Preboreal biozone, ferns became more important in the local vegetation of the mires, and later during the Boreal they formed the undergrowth of swamp forests. During the Boreal biozone, a major expansion of hazel took place in both areas. On the hills and slopes of the northern Wetterau and the Amöneburger Basin, open pine forests and hazel scrub developed with grasses and Pteridium in the field layer. In the river valleys, pine forests were replaced by deciduous mixed forests with oak, elm and later also with lime.

Late-glacial and Holocene vegetation history and dynamics as shown by pollen and plant macrofossil analyses in annually laminated sediments from Soppensee, central Switzerland

The palynostratigraphy of two sediment cores from Soppensee, Central Switzerland (596 m asl) was correlated with nine regional pollen assemblage zones defined for the Swiss Plateau. This biostratigraphy shows that the sedimentary record of Soppensee includes the last 15 000 years, i.e. the entire Late-glacial and Holocene environmental history. The vegetation history of the Soppensee catchment was inferred by pollen and plant-macrofossil analyses on three different cores taken in the deepest part of the lake basin (27 m). On the basis of a high-resolution varve and calibrated radiocarbonchronology it was possible to estimate pollen accumulation rates, which together with the pollen percentage data, formed the basis for the interpretation of the past vegetation dynamics. The basal sediment dates back to the last glacial. After reforestation with juniper and birch at ca. 12 700 B.P., the vegetation changed at around 12 000 B.P. to a pine-birch woodland and at the onset of the Holocene to a mixed deciduous forest. At ca. 7000 B.P., fir expanded and dominated the vegetation with beech becoming predominant at ca. 50014C-years later until sometime during the Iron Age. Large-scale deforestation, especially during the Middle Ages, altered the vegetation cover drastically. During the Late-glacial period two distinct regressive phases in vegetation development are demonstrated, namely, the Aegelsee oscillation (equivalent to the Older Dryas biozone) and the Younger Dryas biozone. No unambiguous evidence for Holocene climatic change was detected at Soppensee. Human presence is indicated by early cereal pollen and distinct pulses of forest clearance as a result of human activity can be observed from the Neolithic period onwards.

Lateglacial and early Holocene pollen stratigraphy of the northern Apennines, Italy: A contribution to the ‘North Atlantic seaboard programme’ of IGCP-253, ‘Termination of the Pleistocene’

Pollen diagrams, supported by 25 radiocarbon dates, are presented for four sites in the Ligurian-Emilian Apennines, Northern Italy, which collectively span the Late Weichselian Lateglacial and Holocene. Coleopteran evidence is available for the Lateglacial and early Holocene sediments from one of the sites. Collectively the data provide: (a) an internally consistent series of local pollen assemblages zones, such that regional pollen assemblage zones are defined; (b) a detailed chronology of vegetation changes in the region; (c) an impression of environmental changes during the Lateglacial-Holocene transition. Of particular note is the clear evidence for a marked Younger Dryas event, which, together with evidence from other parts of southern Europe, indicates that the climatic severity of this event did not diminish southwards on the European continent. Also of significance is the pollen and coleopteran evidence for mixed woodland in the region during the Lateglacial Interstadial, which is not in keeping with previous reconstructions.

Pollen Diagrams from Holderness, North Humberside

Two pollen diagrams from Holderness, North Humberside, covering the Late Devensian substage and the Flandrian stage, are presented. Radiocarbon dating of the Late Devensian sediments at one site allowed the tentative estimation of pollen influx figures. The inferred vegetational history of the Late Devensian in Holderness appears to fit into place along a gradient of increasing oceanicity from east to west across northern Europe and a northsouth temperature gradient through eastern England. For the Flandrian stage regional pollen assemblage zones were constructed for Holderness. The vegetational history of the region was established through a comparison of the pollen profiles of the two distinctly different sites, one a valley mere and the other a kettle hole.

Late Holocene Pollen Assemblages in the Lowlands of Akita Region, Northern Japan

The late Holocene deposits in the lowlands are subdivided into three regional pollen assemblage zones, i. e. Quercus-Fagus zone, Cryptomeria-Fagus-Quercus zone, and Pinus zone in ascending order, based on the occurrences of the regional temperate trees. The ages for the base of each zone are older than ca 6, 000y. B. P. for the lower, 2, 700-2, 000 radiocarbon y. B. P. for the middle, and ca 1, 000y. B. P. for the upper. From a comparison with the previous studies on the mountainlands, it suggests that Cryptomeria and Pinus have spread mainly in the lowlands, and these have not made an striking invarsion upon the Fagus forests in the mountainlands.

Late Quaternary Vegetational History of Southeastern Labrador

Pollen percentage and influx diagrams for three lake-sediment cores from southeastern Labrador are subdivided into three regional pollen assemblage zones: (I) Betula-SalixCyperaceae zone, 10,500 to 9000 14C yr BP; (II) Alnus-Abies-Picea zone, 9000 to 5000 BP; (III) Picea zone, 5000 BP to present. Pollen influx was low in zone I, rose in zone II, and then abruptly increased in the upper part of zone II when tree pollen was first deposited in significant amounts. Influx reached a maximum about 4000 yr ago and declined substantially after 2500 BP. An early phase of tundra was succeeded 9000 yr ago by Betula-Alnus shrub-tundra as the climate warmed. Trees then colonized the shrub-tund a at 6000 BP arriving late relative to sites farther south and west. The initial forest community is interpreted as a park-tundra of Picea glauca with abundant Abies balsamea and probably with some Betula papyrifera. After a period of about 700 yr, Abies declined in favor of Picea mariana as soil conditions began to deteriorate. The formation of peat was probably accelerated at this time. The pollen record from a site on the south coast shows that the coastal region was never forested. The pollen influx record shows distinct similarities to that of the inland sites, suggesting that climate was most temperate bout 4000 yr ago and that a deterioration took place about 2500 BP.

Postglacial Environmental History of Rannoch Moor, Scotland. II. Pollen Diagrams and Radiocarbon Dates from the Rannoch Station and Corrour Areas

This paper presents the results of further investigations into the early Postglacial environmental history of Rannoch Moor, Scotland. Detailed pollen analyses were carried out at four sites in the eastern and northern parts of the Moor, and radiocarbon dates were obtained from three of the profiles. The pollen stratigraphic and radiocarbon data lend considerable support to conclusions reached from previous research in the Rannoch Moor area. The evidence suggests that glacier ice of the Loch Lomond Advance had dis- appeared completely well before 10 000 BP by which time a dwarf shrub heath vegetation had become firmly established locally. Birch woodlands were wide- spread in the Rannoch Moor area by c. 9800 BP, and were succeeded by a forest cover of birch, hazel, pine and alder. The close similarities between the pollen records from all the sites on Rannoch Moor suggest that apart from minor local variations there was very little regional differentiation in vegetation composition throughout this area of the Grampians during the Postglacial period. This in turn suggests that the regional pollen assemblage zones (R-zones) defined here can be used for the correlation of ecological changes within the Rannoch Moor area.

Holocene pollen stratigraphy of southern Sweden: a reappraisal using numerical methods

Holocene pollen data from two sites in Blekinge and one site in Scania were zoned independently by four different numerical methods. Local or site pollen assemblage zones were established for each sequence. Numerical comparisons of the two sites in Blekinge reveal similarities which allow the definition of a series of regional pollen assemblage zones for Blekinge. Numerical comparisons between Blekinge and Scania indicate no such similarities, and emphasise the necessity to establish regional zones for each area. Correlations between areas can then be attempted using radiocarbon dates. The advantages and disadvantages of applying numerical methods for these purposes are discussed, and their broader applications to a Nordic pollen correlation project are outlined.

Pollen Percentage and Influx Analyses in South-East Ireland: A Contribution to the Ecological History of the Late-Glacial Period

SUMMARY (1) Pollen analyses of thick Late-glacial sediments at Coolteen, Co. Wexford, and Late-glacial and early postglacial sediments at Belle Lake, Co. Waterford, are described. (2) The pollen diagrams are divided into local pollen assemblage zones, which were distinguished before being related to conventional zonations. Four regional pollen assemblage zones are recognized, spanning the period from 12 500 B.P. or earlier to shortly before 10 000 B.P., and are named the Rumex, Juniperus-Filipendula, Gramineae and Cyperaceae-Caryophyllaceae-Artemisia pollen assemblage zones, respectively. (3) Three regional pollen peak zones spanning the Late-glacial-postglacial transition are also recognized, and named the Gramineae, Juniperus and Betula pollen peak zones respectively. (4) Comparisons are made with features of pollen diagrams from other Irish and British sites, and the chronology of the zones is considered. (5) Radiocarbon dating and the addition of polystyrene microspheres to the samples permitted calculation of pollen influx per cm2 per year. (6) Total pollen concentration and influx, which are very low only in the basal Rumex assemblage zone, are compared with corresponding figures elsewhere. Empirical evidence suggests that concentration is, in some circumstances, more significant than influx. (7) The regional ecological history of south-east Ireland is discussed. The importance of grassland at and prior to 11 000 B.P., the presence of Koenigia and other arctic-alpines towards the end of the Late-glacial period, and the predominance of Quercus rather than Pinus in the early postglacial period are among significant features noted. (8) The evidence presented does not conflict with, and in some respects supports, evidence from fossil Coleoptera elsewhere about Late-glacial climates.

Late-devensian and flandrian vegetational history of Bodmin Moor, Cornwall

A largely palynological study of new exposures of lake and mire sediments from Bodmin Moor, Cornwall, together with radiocarbon dating of the polliniferous deposits has allowed, for the first time in southwest England, description of dated local and regional pollen assemblage zones which can be correlated with the pollen zones of Godwin and the chronozones of West. Reconstruction of the vegetational history of the Late-Devensian, early and later Flandrian periods is attempted by using, wherever possible, values for the pollen content of sediments to illuminate real pollen taxon percentage fluctuations. Deposition of limnic sediments in the Late-Devensian started shortly before 13000 b.p. when the dominant vegetation, open grass heaths, snow-beds and flushes, reflects the cold climate. Soils at this time were subject to erosion by snow melt-water. Ensuing climatic amelioration permitted invasion by juniper scrub and about 12000 b.p. expansion of tree birches took pace. Climatic recession occurring under strongly oceanic conditions (marked by considerable amorphous solifluction of the upland soils and the development of grass/sedge mires) was initiated about 11000 b.p., but its duration here cannot be accurately estimated. Within this threefold pattern of Late-Devensian deposition 12 distinct pollen assemblages are described from four profiles. Pollen of Artemisia norvegica, Astragalus alpinus and Saxifraga stellaris is confined to the earlier and later colder periods. In the intervening warmer period, but not the colder periods, there is slight pollen and macroscopic fossil evidence of Betula nana. An unexplained unconformity exists at the base of the Flandrian deposits. Early Flandrian vegetation is characterized by the spread of tree birches and Salix in the valleys, with Empetrum and juniper on the hillsides. The two latter genera are replaced before 9000 b.p. by Corylus followed almost immediately by the spread of Quercus. Throughout the Flandrian Quercus , Betula and Corylus , although the dominant woodland genera, probably colonized only the more sheltered sites on the upland. Archaeological and palynological records have been correlated as far as possible, the only substantial pollen record of human activity being that of Plantago , which spread encouraged by Bronze Age pastoralism. There is also pollen evidence of scanty cereal cultivation. Areas on the Atlantic fringes of Europe show a marked similarity in their early Flandrian forest history, particularly with regard to the slight role played by Pirns in relation to Quercus compared with stations further east. This similarity must derive from the proximity of the tempering influences of the North Atlantic Drift.

Late quaternary history of vegetation and climate of the Rajasthan desert, India

The results from stratigraphy, radiocarbon dating and pollen analysis of three salt-lake deposits at Sambhar, Lunkaransar and Didwana in western Raj'asthan, and one freshwater lake deposit at Pushkar in the Aravalli Hills, are described in conjunction with pollen analysis of some archaeological soil samples from the Indus Valley site at Kalibangan in northern Rajasthan. The salt-lake deposits studied are stratigraphically divisible into (a) pre-lacustrine, (b) lacustrine and (c) post-lacustrine sections. The pre-lacustrine section is characterized by a thick bed of aeolian sand underlying lacustrine sediments, while the lacustrine and post-lacustrine sections are broadly circumscribed by laminated clay and nonlaminated silt respectively. The pollen record from the four lake profiles studied is divided into local pollen zones. Four regional pollen assemblage zones are delineated for the area west of the Aravalli Range in Rajasthan. The environmental history deduced from the pollen record is divisible into phases I-V, of which phases II-V follow the regional pollen assemblage zones. Phase I is stratigraphically determined, and is representative of severe arid environments under which the sand dunes, now stabilized, are suggested to have been active. The plant microfossils first appear in phase II with the deposition of lacustrine sediments dated to around 10000 b . p . The vegetation comprises an openland steppe which is rich in grasses, Artemisia and sedges and poor in halophytes. Artemisa, Typha angustata, Mimosa rubicaulis and Oldenlandia , which now grow under areas of comparatively higher average annual rainfall (above 50 cm), appear to have flourished in the semi-arid belt, while the first two plant taxa had encroached even as far as the arid belt, both suggesting that a general westward shift of the rainfall belts had taken place. Vegetation destruction through burning by man is suggested to have started together with the first occurrence of Cerealia-type pollen at about 7500 b . c . and continued thereafter throughout phases III and IV. The increase in swamp vegetation and the intensification of vegetation cover inland together with the maxima of all mesophytic elements in phase IV ( ca. 3000 b .c . to ca. 1000 b .c .) indicate an increase in the rainfall, apart from a short relatively drier time about 1800-1500 b . c . at Sambhar which correlates with the decline of the Indus culture in northwest India. Phase IV is immediately followed by aridity for which there is stratigraphic evidence that the salt lakes started drying. At Pushkar, there is evidence that the vegetation showed a marked change in the Aravallis. The onset of this aridity is suggested to have been widespread. The climate did not ameliorate until about phase V (? early centuries a .d . to present) at which time the Rangmahal culture perhaps flourished in Rajasthan, the remains of which imply good water supply. In conclusion it is suggested that the Rajasthan desert is primarily natural, its history punctuated by at least one more vegetated, humid period during the Holocene, the climatic control of which as indicated by the vegetation history is consistent with climatic events elsewhere in the world.

NUMERIGAL METHODS IN QUATERNARY PALAEOECOLOGY

SummaryComparison of pollen diagrams is an important stage in pollen analytical Investigations as it is the basis for the recognition of regional pollen assemblage zones. Three numerical approaches to the problem of comparing stratigraphical sequences are presented. Their use is illustrated by two contrasting sets of data, one from two sites of Late‐Wisconsin age in central Minnesota, the other from a transect of sites in north‐west Minnesota extending from Late‐Wisconsin to present times. The first approach compares pollen zones at the different sites on two numerical criteria, information radius and concordance. The other two approaches compare sequences on a level by‐level basis; the second method by means of non‐metric multidimensional scaling and the third by a slotting procedure by which levels at one site are slotted between levels at another site on the basis of similarities in pollen composition. The advantages and disadvantages of the three approaches are discussed.