Pollen In Sediments Research Articles

A sedimentary record of human disturbance from Lake Miragoane, Haiti

Lake Miragoane, Haiti is one of the largest, natural freshwater lakes in the Caribbean (A=7.06 km2, zmax=41.0 m, conductivity = 350 μS cm−1). Lake waters are dominated by calcium and bicarbonate ions. The lake was thermally stratified, and oxygen profiles were clinograde during summer visits in 1983 and 1985. A 72-cm mud-water interface core was taken near the center of the lake and dated with 210Pb. The local 210Pb fallout rate is low (0.09 pCi cm−2 yr−1), about 20% of the global average. Bulk sedimentation rates ranged from 0.008 to 0.030 g cm−2 yr−1 during the past 130 years (0–8 cm depth). Sediment geochemistry and pollen have been analyzed in the topmost 58 cm of the section. Tentative ages were assigned to the core by extrapolation of 210Pb dates. According to this preliminary chronology, the bottom part of the core (58–30 cm) records pre-Columbian sedimentation (1000–500 B.P.) and contains pollen evidence of intact, dry and mesic forest. Pre-Columbian deposits are rich in organic matter (x = 30%) and relatively poor in carbonates (x = 15% as CO2). The top 30 cm of the core preserve the record since European contact (500 B.P. to present). Pollen data reveal two episodes of deforestation following European arrival. Consequent soil erosion is documented by a decrease in organic matter content (x = 15%) and an increase in carbonates (x = 27% as CO2). Surficial sediments reflect the widespread deforestation and soil loss that characterize the watershed today.

A Fine-Resolution Palaeoecology and Palaeoclimatology from South-Eastern Australia

(1) This study attempts to bridge the gap in time-scale that has separated sedimentary pollen records from modern ecological and meteorological data. (2) Two pollen records were obtained, both at yearly intervals: a pollen-rain history (1975-84) and a record of past (1950-75) pollen accumulation, based on detailed 14C analyses of bomb carbon from finely-sectioned peat deposits. By matching these data with instrumental rainfall records at yearly intervals, recent pollen production and accumulation changes are related to short-term fluctuations in precipitation and fire occurrence. (3) The modern pollen-rain study demonstrates a close relationship between rainfall and the pollen production and accumulation of several taxa. (4) Comparisons between sedimentary pollen records and meteorological data show that the vegetation response, through pollen production and accumulation, was sufficiently sensitive to register short-term, low-amplitude changes in precipitation in the swamp sedimentary record. (5) Related studies include charcoal particle analyses, fire scar surveys, and process modelling. (6) The combined results provide a basis for recognizing short-term, low-amplitude changes in vegetation and precipitation, not only from contemporary sediments, but also from finely datable sediments of Holocene and late Pleistocene origin.

The establishment of vegetation after late pleistocene deglaciation in the Paramo de Miranda, Venezuelan Andes

Palynological analyses of samples from a fluvioglacial terrace at 3920 m elevation, in the periglacial belt of the Paramo de Miranda, has shown that, before 11,500 to about 11,120 yr B.P., the very few plants growing in the region belonged to the Gramineae, the Compositae (mainly to Coespeletia) and Montia. The climate was colder than at present. During the early Holocene the concentration of pollen and spores in sediments increased and new pollen types from paramo plants were incorporated. Pollen of the Caryophyllaceae (mainly Arenaria), of Gentiana, Valeriana, Geranium and a few genera of Compositae reached the site. Long-distance pollen, derived from the cloud forest increased and Podocarpus pollen was more abundant than at present. These results suggest that temperatures increased at the beginning of the Holocene, the vegetation attaining a density similar to that of the present, although with fewer species. From 5470 to 2500 yr B.P. pollen and spore concentrations fluctuated and other types, including Rhizocephalum and Isoetes, followed by Draba, Plantago and certain other genera of the Composite were now present in the sediments. From ca 3000 yr B.P. onwards the composition of the pollen assemblages was the same as at present. Two cold phases were detected, one from earlier than 11,500 to 11,120 yr B.P. and another from 6000 to 5250 yr B.P. A warm phase from ca 2690 to 2500 yr B.P. probably represented a rise of about 1.2°C above the modern average temperature. In general terms, the climatic oscillations detected at Miranda are in accordance with those in other parts of South America.

Fossil pigments in paleoecology and paleolimnology

For the past several decades scientists have been examining the nature of sedimentary chlorophylls and carotenoids from freshwater lakes for their value in paleoecology and paleolimnology. Unaltered chlorophyll molecules are rarely preserved for long periods, but the pheo-derivatives and chlorophyllides are common throughout lake sedimentary columns. Carotenoids tend to preserve largely unaltered from their conditions in living plant membranes, but degrade quickly to colorless derivatives when oxidized. Measurements of sedimentary pigment concentrations, ratios of chlorophyll derivatives to carotenoids and diversity, especially as regards prokaryote carotenoids, are most commonly published. This paper assesses the value of using sedimentary pigment data to provide paleoecological information on lake evolution and changing patterns of aquatic primary productivity. Factors that promote pigment preservation are contrasted to those that alter and cause destruction of organic molecules. The value of fossil pigments is considered in ascertaining the sources of organic matter to sediments and for providing clues to the changing diversity of aquatic flora, both rooted and planktonic. Consideration is given to recent investigations that have sought information from sedimentary pigments on the onset and intensity of cultural eutrophication, both in individual lakes and on a regional basis, and in the monitoring of progress toward lake restoration. A special case is made for the value of sampling meromictic lakes. In addition, this review provides information on the limitations of the sampling procedures, laboratory techniques, and interpretation of results, Discussion is made of the most valuable and easily obtainable data that can provide reliable, comparable and reproducible results. Special consideration is given to the value of the pigment data in supplementing additional paleoecological indicators such as sedimentary pollen grains, zooplankton, and various other sedimentary bio- and geochemical products.

An evaluation of statistical techniques for discriminating Picea glauca from Picea mariana pollen in northern Alaska

Two statistical procedures, linear discrimination and maximum likelihood discrimination, were evaluated for use in estimating percentages of Picea glauca and P. mariana pollen in lake sediments of northern Alaska. Each procedure is based on a comparison of the dimensions of unclassified Picea pollen grains with those of reference pollen of each species. The reference pollen collection in this study consisted of 675 P. glauca and 600 P. mariana grains, representing 51 trees at 24 sites in Alaska. The reference collection was divided into two approximately equal parts; one was used to derive the discriminant functions of each technique and the other was used to test the accuracy of each function on populations of known composition. The maximum likelihood procedure produced unbiased estimates across the entire range of test populations (P. glauca: P. mariana ratios ranging from 5:95 to 95:5). The linear discrimination estimates were strongly biased in favor of the less frequent species in populations having less than 25% of either species. We applied both techniques to measurements of Picea pollen in surface sediments of 62 lakes in the boreal forest of northern Alaska. Picea pollen percentages estimated by maximum likelihood discrimination more closely revealed the distribution of Picea trees in the landscape.

Recent pollen sedimentation in Lake Natron, Tanzania : a model for the interpretation of fossil spectra in arid region. Sédimentation pollinique actuelle dans le lac Natron, Tanzanie : un modèle pour l'interprétation de spectres fossiles en région aride

This paper presents the palynological results obtained from 12 samples of surface sediments from Lake Natron, Tanzania. The spectra are a mixture of autochtonous and allochtonous pollen which represent all the main vegetation types occurring in the basin. The abundance of herbaceous taxa, low representation of local arboreal taxa with Acacia, Commiphora dominant provide a good picture of the pollen sedimentation in an arid region. Only small variations occur within the distribution of various pollen, related to the influence of transport agents like rivers but also to variations in local edaphic conditions. A comparison with palynological data from other east african lakes Turkana and Bogoria in Kenya shows clearly that modern spectra from Lake Natron can be considered as a good model of pollen sedimentation in a lake without flat-land around it and situated in a region with a mean annual rainfall less than 500 mm.

Pollen sedimentation in the Northwest Atlantic: Effects of the Western Boundary Undercurrent

Sedimentation on the continental rise off eastern North America is strongly affected by the southerly flowing Western Boundary Undercurrent (WBUC). Recent studies of physical characteristics (position and velocity field) of this contour current show that the high-velocity core is characterized by decreased carbonate dissolution, coarse particle size, and improved magnetic alignment of sedimentary grains. In this report, we suggest that the high-velocity core of the WBUC also effects palynomorph sedimentation; pollen concentration is lower and the percentage of redeposited pollen grains is higher under this bottom current.

Pollen and radiolarian records from deep-sea core RC14-103: Climatic reconstructions of northeast Japan and Northwest Pacific for the last 90,000 years

Using modern pollen and radiolarian distributions in sediments from the northwest Pacific and seas adjacent to Japan to interpret floral and faunal changes in core RC14-103 (44°02′N, 152°56′E), we recognize two major responses of the biota of eastern Hokkaido and the northwest Pacific to climatic changes since the last interglaciation. Relatively stable glacial environments (∼80,000–20,000 yr B.P.) were basically cold and wet (<4°C and ∼1000 mm mean annual temperature and precipitation, respectively) with boreal conijers and tundra/park-tundra on Hokkaido, and cool (<16°C) summer and cold (<1.0°C) winter surface temperatures offshore. Contrasting nonglacial environments (∼10,000–4000 yr B.P.) were warm and humid (>8°C and >1200 mm mean annual temperature and precipitation, respectively), supporting climax broadleaf deciduous forest with Quercus and Ulmus/Zelkova, with surface waters in the northwest Pacific characterized by warm (>1.5°C) winter and cold (10.4°–14.3°C) summer temperatures. Climatic evidence from RC14-103 shows a high degree of local and regional variation within the context of global climatic change. Correlative ocean and land records provide the detailed input necessary to assess local/regional responses to variations in other key elements (i.e., solar radiation, monsoonal variations) of the northeast Asian climate system.

Differences in pollen and macrophytic remains in sediments from various depths in a small kettle‐hole lake in southern Finland

Stratigraphical analyses from four locations within the same lake revealed differential dispersal of pollen in sediment, and horizontal movement and focusing of sediment, but revealed only slight differences in pollen and macrofossil assemblages. Between 9,000 and 8,000 B.P., organic sediments focused into the central depth of the basin and no sediment accumulated in the littoral sites in water &lt; 7.5 m deep. From around 5,000 to 4,500 B.P., deposition took place more or less continuously at all four sites. After 1,600 B.P., the marked change in lithology is due to a heavy rise in organic and minerogenic input from the unforested watershed. The littoral cores show that not only does the water depth cause rcdeposition and focusing of sediment, but also the morphometry of the basin. The comparison between macrofossils and pollen, both produced primarily by the same vegetation around the lake, confirmed the reconstruction of local environmental short‐term changes which occurred after the clearance of forest vegetation by man.

Geolipid, pollen and diaton stratigraphy in postglacial lacustrine sediments

As part of our continuing investigation of specific compounds as organic matter indicators in lake bottoms, we have examined geolipids, pollen and diatoms in sediments from different periods in the postglacial history of Heart Lake, New York. Sediment core sections representing the major watershed vegetation periods were extracted for unbound and bound fatty acids, hydrocarbons and alcohols. Fatty acids constitute most of the extracted material. Minor decreases in unsaturated acids with depth indicate little degradation of organic matter in these sediments. The dominant unbound n-alkanoic acid in the core sections is either C 22 or C 24, but bound fractions contain few long chain acids and are dominated by n-C 16. Nearly all the hydrocarbons are found in the unbound fraction. The ratio of C 29/C 17 n-alkanes increases from the bottom of the core to near the top as watershed forests have matured and lake productivity has diminished, but drops since European settlement of the region. Organic degradation in this lake bottom is mild, and input indicators appear to be well preserved.

Palynological evidence for lake-level changes during the Flandrian in Scotland

Summary Stratigraphic, relative pollen analytical data and pollen concentration data are presented from two cores collected from a lowland infilled lake basin in the eastern Scottish Borderlands. The stratigraphic sequence between 1·30 m and 2·16 m shows an oscillation of open water and deep water sediments indicating lake-level changes. This is supported by the pollen analytical data which show a markedly changing pollen sedimentation rate and a hiatus in Flandrian II due to changing lake-levels and an overall reduction in water-level. Supporting evidence is also drawn from Din Moss, a nearby radiocarbon dated profile.

Interpretation of Floodplain Pollen in Alluvial Sediments from an Arid Region

AbstractPollen was collected from modern alluvium and from the atmosphere to document the nature and amount of paleoenvironmental information reflected by alluvial pollen chronologies. Results indicate that pollen in alluvium is a homogeneous mixture derived almost entirely from the floodplain itself. The few pollen grains derived from nonfloodplain plant communities and preserved in alluvial sediments are so well mixed that their frequencies no longer reflect the geographic distribution of the specific plant communities in which they originated. In contrast, the abundance of alluvial pollen grains, derived from the major floodplain taxa (Chenopodiineae, Ambrosia type), varies with summer and winter climate. This annual variation is preserved in alluvial pollen assemblages through a combination of processes within sedimentation basins involving discontinuous deposition events and mechanical pollen degradation. The high-frequency, wide-amplitude pollen variance in alluvial pollen assemblages contrasts with the low-frequency, narrow-amplitude pollen variance in sediments of lakes and ponds. The slight geographic variance in alluvial pollen assemblages, in contrast to the large variance in soil pollen, allows use of alluvial pollen to infer climate throughout the watershed in which pollen is sampled.

Pollen distribution in recent marine sediments, eastern Canada

Analysis of 90 samples from coastal and continental shelf areas off eastern Canada between 42 and 69°N shows that Quaternary pollen and spores are present in recent marine muds throughout this region. Pollen and spore concentrations range from 50 000 to 100 grains per cm3 and they decrease both offshore as a function of distance from vegetation sources and northwards as a function of lower vegetation density north of the summer Arctic Frontal Zone. Isopercentage contours show that maximum relative abundances of most palynomorphs occur in marine sediments adjacent to their regions of highest vegetation representation onshore. However, Pinus and Picea pollen tend to increase in percentage abundance with distance offshore. Presence of these tree pollen in marine sediments off Baffin Island implies that wind transport is an important pathway by which bisaccate pollen types enter the ocean, in addition to fluvial transport.Q-mode factor analysis shows that four major factors account for 89% of the variance among the marine palynomorph samples, while two other factors (6% of the variance) apparently reflect selective transport of Pinus pollen or local over-representation of Gramineae. The major factor assemblages are: (1) Boreal Forest Assemblage, with high weightings of Picea and maximum loadings adjacent to the boreal forest, 48–54°N; (2) Arctic Assemblage, weighted by Rosaceae, Gramineae, and Cyperaceae, with maximum loadings off Baffin Island, 60–69°N; (3) Mixed Forest Assemblage, weighted by Betula tree pollen, Picea glauca, Pinus strobus, Tsuga, and temperate trees (e.g., Quercus, Acer), with maximum loadings in the southeast, 42–48°N; (4) Subarctic Assemblage, with high weightings of Sphagnum, Alnus, and Lycopodium, and maximum loadings adjacent to forest–tundra and low arctic tundra, 54–60°N. These regional marine pollen assemblages are empirically related to contemporary climatic parameters, thus indicating the potential value of pollen analysis for direct correlation between Quaternary paleoclimatic records onshore and in marine areas bordering eastern Canada.

Recent sediment flux and erosional processes in a Welsh upland lake-catchment based on magnetic susceptibility measurements

Single sample magnetic susceptibility measurements are used to correlate synchronous levels in 16 cores of dated ( 210Pb, 137Cs) recent sediment taken from the deep and oligotrophic Llyn Peris, N. Wales, in order to provide a basis for calculating total sediment and chemical influx through time. Results show that sediment influx has steadily increased since c. 1750 A.D. to reach peak levels in the period 1966–1976 A.D., equivalent to a rise in erosion in the catchment from c. 5 t km −2 yr −1 to c. 42 t km −2 yr −1. Comparison of down-core susceptibility fluctuations with sediment pollen and organic pigment data indicates that maximum susceptibility values relate to periods of channel erosion and minimum susceptibility values relate to periods of slate debris inwash from spoil tips in the catchment. A study of historical records reveals that pre-twentieth-century peak levels of erosion were due to the effects of extractive industries, while twentieth-century erosion has been caused by overgrazing, increased trampling pressure, and heavy construction works in the catchment.

Spatial distributions of pollen in surface sediments of the Potomac estuary1

Pollen of trees extracted from surface sediments of the Potomac estuary represent all components of the arboreal vegetation, with the exception of Liriodendron tulipifera (tulip poplar), and reflect the major forest gradients in a broad band adjacent to the estuary. Pollen of common trees restricted to the upper watershed, 60 km upstream of the limit of tidal influence, are not present in downstream estuarine deposits.A comparison of the statistical variability in pollen data from estuarine sediments with tree data in the area adjacent to the estuary suggests that atmospheric or estuarine transport processes erase the local patchiness of the trees from the pollen distributions in the sediment. Although dispersion is selective for different pollen types, none of the pollen is transported far enough to mask regional forest gradients.Pollen distributions in Potomac estuary sediments suggest that once particles of approximate hydraulic equivalence become part of the suspended sediment load, they are not widely dispersed within the estuary before initial deposition.

Pollen preservation and quaternary environmental history in the Southeastern United States

Abstract Reconstructions of Quaternary environmental history based upon modern pollen/vegetation/climate calibrations are more tenable if the factors responsible for variation in pollen assemblages are evaluated. Examination of the state of preservation of Quaternary palynomorphs provides quantitative data concerning the degree of information loss due to alteration of pollen assemblages by syndepositional and post‐depositional deterioration. The percentage, concentration, and influx values for total indeterminable pollen are useful criteria in providing an objective and quantitative basis for evaluating the comparability of pollen spectra within and between sites. Supporting data concerning sediment particle‐size distribution, organic matter content, and concentration, influx, and taxonomic composition of both determinable pollen and plant macrofossils aid in reconstructing past depositional environments. The potential is high for deterioration of pollen in sediments from the southeastern United States, although considerable variation is found in both kind and degree of deterioration between lacustrine and alluvial sites of different ages and in different latitudes. Modern analogs are a basis for late Quaternary environmental reconstructions when pollen deterioration has not significantly biased the information content of fossil pollen assemblages.

Spatial variability of foraminifera and pollen in two nearshore sediment sites, St. Georges Bay, Nova Scotia

Spatial variability of sediment texture, foraminiferal, and pollen assemblages were studied at two core sites in St. Georges Bay, using data from replicate cores spaced about 1 m apart. Despite the similarity of water depth (22 m) and location (3.6 km offshore) of the two sites, correlatable sediment textural units could not be clearly distinguished except for the ubiquitous presence of a surface layer of fine-grained sediment. Textural parameters strongly indicate distinctive Holocene depositional histories at each site, which appear to be related to local submarine morphological features.Despite the between-site textural heterogeneity, the depositional histories of all the cores can be correlated spatially and temporally by means of selected paleontologic parameters. In all cores the top 20–30 cm of sediment was found to coincide with the historical weed pollen assemblage zone; hence, the uppermost fine sediment layer most probably reflects an increased influx of fine-grained sediment associated with deforestation and other local land use practices. At both sites, the ratio of common modern calcareous to arenaceous foraminifera species can be used to reveal comparable relative sea level records in each of the cores. However, critical evaluation of combined lithological and faunal data is necessary to distinguish an apparent decrease in water depth that can arise from an increased influx of nearshore sediment and species rather than a real change in relative sea level.Detailed statistical analysis of the variation in foraminiferal abundance parameters shows that absolute abundance data cannot be used for determining relative sedimentation rates in nearshore environments and suggests that biofacies correlations in these environments should be based on assemblages of comparatively abundant species. Within-site similarity in both foraminiferal and palynological assemblages is generally lower for the texturally more heterogeneous site at Linwood than at the more uniformly muddy site near Pomquet. However, relatively high within and between-site correlations of pollen taxa are evident throughout all sediment intervals that comprise more than 50% mud, regardless of differences in sediment sorting parameters and changes in paleodepths at the depositional sites.It appears that studies of the depositional histories of nearshore Holocene sediments in the Atlantic coastal region are most likely to yield results when analysis of combined textural, microfaunal, and palynological parameters is carried out on cores obtained from relatively low-energy depositional sites. It is predicted that for upper Holocene marine sediments, the coarser the texture of a core the less representative it will be of the overall paleoecological history of a region.

IncreasedCannabis/Humuluspollen, an indicator of European agriculture in Iowa

Abstract The percentages of Ambrosia‐type pollen increase in the upper few centimeters of many North American cores of lake sediments or bog peats, For much of eastern North America south of 50 °N, this increase is easily recognizable in pollen diagrams and indicates the time when persons of European origin settled in an area. The actual biostratigraphic proof that this rise”; occurs with settlement requires correlating the Ambrosia rise with the first appearance or the rise in abundance of pollen types from both cultivated and non‐native plants. This requirement is particularly important in the Midwest where Ambrosia is a native weed. Our results illustrate the potential of Cannabis/Humulus pollen as an indicator of settlement and cultivation in Iowa. Pollen of Cannabis/Humulus increases in abundance at or just after the initial rise in Ambrosia‐type pollen in sediments from two Iowa lakes. It first occurs in the sediments of Lake West Okoboji at ca. 1910 AD, which is after the initial Ambrosia...

Modern and ancient pollen sedimentation around tree islands in the Okefenokee Swamp

Abstract Peat cores taken from Okefenokee Swamp tree‐islands (houses) and analyzed by peat petrography and pollen stratigraphy permit us to reconstruct the plant successions which led to the “house”; formation. The peats are believed to be autochthonous and their petrology has been shown to provide an accurate record of plant successions in cores. Because of differences among pollen grain transportation and sedimentation, the reliability of pollen profiles from the islands was initially questioned. The profiles may not represent an accurate record of “house”; vegetational history. Analysis of pollen assemblages collected in the marsh area around an island indicates two distinct assemblages: one derived from shrubs found on the island (Ilex, Cyrilla, Ericaceae); another derived from the surrounding marsh, consisting of aquatic herbs and arboreal genera (Nymphaea, Pinus, Myrica). Palynological analysis of island peats show that shrub pollen is deposited primarily on the island with little contamination fr...

Palynological and temporal inference in the context of prehistory, with special reference to the evidence from lake and peat deposits

There is an increasing use of palynological data to infer prehistoric agricultural activity. The uncritical acceptance of the technique of pollen analysis by archaeologists and palynologists is questioned. Attention is focussed upon the nature of clearance activity and problems of its inference from pollen spectra; the spatial distribution of palaeoenvironmental sites; and the proximity of such sites to those of prehistoric activity. The resolution apparent in peat and lake sediment pollen profiles together with problems of dating and temporal inference, are examined. In response to a perceived lack of formalization in palynological research, some simple models of clearance activity are presented. The complexity involved in environmental reconstruction is emphasized by reference to the use of supplementary data to augment the orthodox pollen record.