Two Supervised Neural Networks for Classification ofSedimentary Organic Matter Images fromPalynological Preparations

An improvement in the supervised artificial neural network classification of sedimentary organic matter images from palynological preparations is presented. Sedimentary organic matter encompasses the entire acid-resistant organic micro-particles (typically with a diameter of 5-500μm) recovered from a sediment or sedimentary rock. Supervised neural networks are trained to recognize patterns within databases for which the correct classifications are already known. Once trained, they are verified on pre-classified samples not seen by the network, and then used for classification of samples whose class is not known. Such networks have an input, hidden and output layer. Typically, these networks determine what the output class is by adjusting weights associated with the layer interconnects, and by modifying the signals that propagate through the hidden layer by a non-linear transfer function. In this example, the inputs in each network are the salient features selected from an available set of 194, while the outputs are the sedimentary organic matter classifications which were formerly developed with the rationalization of descriptive terms from previous classification schemes. The author's past work tested the supervised back propagation neural network for the classification of sedimentary organic matter images. This gave an overall correct classification rate of 87%. However, because the back propagation network underperformed on two of the four classes, the radial basis function neural network was tested on the same databases initially used in an attempt to improve the recognition rate of these two classes. The difference between the back propagation and radial basis function networks lies in the non-linear transfer function applied in the hidden layer, which was modified by a Gaussian function in the latter. In the best-case scenario, this improved the recognition rate by 4% to just over 91%. This has also determined that a series of different supervised neural networks may be better for classification of sedimentary organic matter images. These results are encouraging enough to prompt further research that may result in a commercially viable syste

Macroscopic Sedimentary Charcoal as a Proxy for Past Fire in Northwestern Costa Rica

Proxy records of fire history offer valuable information on the role fire plays in an ecosystem. Such information can be used to understand the inter-relationships among fire, humans, and the environment. In the past, the forests of Costa Rica were thought to have been spared from significant pre-Columbian forest disturbance; however, paleoecological studies have shown that this notion is false. While the long-term human influence is now recognized in Costa Rica, the nature and extent of human effects in different regions remain poorly documented. Knowledge of pre-Columbian land uses in Costa Rica increases our understanding of the possible impacts of past human disturbances on natural ecological patterns and functioning. I studied evidence of prehistoric fire provided by fossil charcoal in a sediment core recovered from a lake in northwestern Costa Rica. I developed a new method for the preparation of samples for macroscopic charcoal analysis, and produced an 8000-year-long high-resolution fire record from macroscopic charcoal. My new method of preparing macroscopic charcoal samples involves treatment of sediment samples with 3% U.S.P. cosmetic grade H2O2 for 24 hours to deflocculate the sediment and bleach some of the non-charcoal organic matter. My high-resolution macroscopic charcoal record revealed that fire has been a part of the seasonally dry tropical lowland forest ecosystem in northwestern Costa Rica for the past 8000 years. I found that charcoal influx and fire frequency were greater during the early to middle Holocene and were lower during the late Holocene. After approximately 3600 cal yr BP, macroscopic charcoal influx dramatically decreased. The timing of this decrease corresponds to archaeological and palynological evidence of human occupation near my study site. Charcoal influx remained low until the arrival of European settlers. I suggest that the increase in charcoal influx at this time is associated with converting forested areas into pasture and the introduction of exotic grass

Late Quaternary fire histories in the eastern Mediterranean region from lake sedimentary micro-charcoals

The Eastern Mediterranean has a long history of human occupation, which spans the transition from hunter-gatherers to the establishment of early agro-pastoralist communities, coinciding with the Last Glacial: Interglacial transition. Over the same timeframe a delay in postglacial woodland recolonisation in the region has been identified. Fire has long been used by people to manage and manipulate the landscape, and has been hypothesised to have played a role in this delay. This thesis employed lacustrine micro charcoal (particles less than 180 !lm) remains to reconstruct Late Quaternary fire histories for Central Turkey and the Levant, and examine the possible role that fire may have played in retarding woodland development in the region. Microcharcoals were analysed in cores taken from four sites in Central Turkey (AkgOl, Eski AClgol, <;atalhOyiik and Nar Golii) and one site in Israel (Lake Hula) that cover varying time intervals from the Last Glacial through to the Late Holocene. In order to develop a standardised analytical procedure for microcharcoals, a series of published extraction and quantification techniques along with a new approach using heavy liquid separation were rigorously tested on "control" samples that contained a known volume of microscopic charcoal. As a result of this investigation a novel, two step extraction procedure based on the use of heavy liquid separation was developed and applied alongside a contiguous high resolution sampling strategy. Using this approach, fire activity was reconstructed based on cores from each of the sites and these data were compared with existing multi-proxy data (stable oxygen isotopes, pollen and archaeological data). Results show clear links between climate, biomass, people and fire, although these relationships changed over time. Regional fire activity during the Last Glacial: Holocene transition was apparently controlled by climate through the influence it exerted on biomass availability, whereas links between people and fire activity are most evident during the Late Holocene. Humans do not seem to have retarded the Early Holocene spread of woodland through the use of fires, although it is possible that natural fire activity served to maintain the open parkland vegetation communities may have played a role. During the Mid Holocene a mixture of climatic and anthropogenic controls apparently influenced regional fire activity. Evidence was also identified of a ca.l ,500 year periodicity in fire history from Central Turkey which may reflect teleconnections to climatic changes in the North Atlantic. This research also highlighted the potential of using microscopic charcoal to infer the spatial resolution of fire history reconstructions from lake basins of different sizes and types through comparisons of influx values

LATE QUATERNARY FIRE HISTORIES IN THE EASTERN MEDITERRNEAN REGION FROM LAKE SEDIMENTARY MICRO-CHARCOALS

The Eastern Mediterranean has a long history of human occupation, which spans the transition from hunter-gatherers to the establishment of early agro-pastoralist communities, coinciding with the Last Glacial: Interglacial transition. Over the same timeframe a delay in post glacial woodland recolonisation in the region has been identified. Fire has long been used by people to manage and manipulate the landscape, and has been hypothesised to have played a role in this delay. This thesis employed lacustrine microcharcoal (particles less than 180 µm) remains to reconstruct Late Quaternary fire histories for Central Turkey and the Levant, and examine the possible role that fire may have played in retarding woodland development in the region. Microcharcoals were analysed in cores taken from four sites in Central Turkey (Akgol, Eski Acigol, Catalhoyuk and Nar Golu) and one site in Israel (Lake Hula) that cover varying time intervals from the Last Glacial through to the Late Holocene. In order to develop a standardised analytical procedure for microcharcoals, a series of published extraction and quantification techniques along with a new approach using heavy liquid separation were rigorously tested on "control" samples that contained a known volume of microscopic charcoal. As a result of this investigation a novel, two step extraction procedure based on the use of heavy liquid separation was developed and applied alongside a contiguous high resolution sampling strategy. Using this approach, fire activity was reconstructed based on cores from each of the sites and these data were compared with existing multi-proxy data (stable oxygen isotopes, pollen and archaeological data). Results show clear links between climate, biomass, people and fire, although these relationships changed over time. Regional fire activity during the Last Glacial: Holocene transition was apparently controlled by climate through the influence it exerted on biomass availability, whereas links between people and fire activity are most evident during the Late Holocene. Humans do not seem to have retarded the Early Holocene spread of woodland through the use of fires, although it is possible that natural fire activity served to maintain the open parkland vegetation communities may have played a role. During the Mid Holocene a mixture of climatic and anthropogenic controls apparently influenced regional fire activity. Evidence was also identified of a ca.l,500 year periodicity in fire history from Central Turkey which may reflect teleconnections to climatic changes in the North Atlantic. This research also highlighted the potential of using microscopic charcoal to infer the spatial resolution of fire history reconstructions from lake basins of different sizes and types through comparisons of influx values

Geochemical and palynological signals for palaeoenvironmental change in south west England

Merged with duplicate record 10026.1/850 on 10.04.2017 by CS (TIS)This thesis evaluates the utility of a geochemical technique for the investigation of palaeoenvironmental change in south west England. The method, EDMA (Energy Dispersive X-ray Micro Analysis), is a rapid, non-destructive analysis tool, capable of detecting a large range of geochemical elements. This research examines the most appropriate method of sample preparation for organic soils and peats, and investigates the reliability of results gained from EDMA with respect to conventional bulk geochemical techniques. A detailed study focused on a range of different sedimentary sites in south west England where a variety of palaeoenvironmental changes were thought to occur. Pollen analysis was undertaken on the same sedimentary material, and provided complementary information on the nature and scale of vegetation change through time. Sediments from a coastal valley mire near North Sands, Salcombe, revealed information relating to the processes of sea-level change in this part of south Devon and the subsequent autogenic processes as the sediment accumulated through time. A range of sites were located on the granitic upland of Dartmoor. A raised bog, Tor Royal, provided data relating to the changing nature of the central upland landscape from late Mesolithic times to the present day. Two soligenous sites. Upper Merrivale and Piles Copse, sought to investigate the activities of postulated anthropogenic activity at a much smaller spatial scale, with particular interest placed upon the evidence for deforestation activity and the utilisation of the local mineral resources. The last site, Crift Down, a lowland spring fed valley mire utilised geochemical and palynological fluxes within the peat to investigate processes and activities associated with archaeological evidence for Medieval tinworking in this area of Cornwall. The results from the EDMA investigations, and comparable studies using other geochemical methods including EMMA, AAS and flame photometry, suggest the technique to have greatest applicability as a first stage tool in the analysis of general activities of past environmental change. The technique was found to yield reliable results for the major elements (Si, Al, S, Fe, Ca, K, Na and Mg), but is generally incapable of providing useful data on heavy metal elements. The data from south west England suggest the method to reflect activity at a range of different scales, and as part of a structured programme of analysis may contribute information to allow a more holistic environmental reconstruction to be made

Paleoecology of the Moreno Hill Formation (Turonian-Coniacian, Cretaceous) of New Mexico

The Cretaceous Terrestrial Revolution was a period of diversification of all major terrestrial groups that coincides with the rapid evolution and establishment of angiosperms (flowering plants) that began ~125 million years ago. The Moreno Hill Formation (MHF) was deposited over a two-million-year span of time during the late Early Cretaceous (90.9 Ma-88.6 Ma) and is a near-shore terrestrial deposit, except for a marine incursion near the base of the formation. The Moreno Hill Formation coincides with the first peak of angiosperm diversity in the Cretaceous. A moderately diverse vertebrate fauna has been recovered from the MHF including several members of Dinosauria. To better understand the ecology and climate of the formation, I analyzed four fossil wood specimens—three from the lower member and one from the upper member—to determine the taxonomic relationships of those woods, and the climate during deposition of the Moreno Hill Formation. On the basis of character analysis, all four specimens are assigned to Cupressinoxylon sp. aff. C. manuelli. The growth habits of the woods from the lower member and the wood from the upper member were found to be different suggesting a change in climate from the lower member to the upper member. I also developed a new method for the analysis of palynodebris (acid-resistant organic remains) using samples that were collected from the upper member of the Moreno Hill Formation. I utilized the Malvern Morphologi G3 morphometric microscope and its associated software. My new protocol to automate collection of palynodebris data was compared to data collected by conventional analysis in order to evaluate the method’s efficacy. I then used both data sets to interpret changes in taphonomic signatures that could affect interpretation of paleoecological data from the Moreno Hill Formation

Late quaternary palaeoenvironments of the Sandveld, Western Cape Province, South Africa

Summary in English.Bibliography: leaves 263-292.This thesis presents new palaeoenvironmental evidence from the semi-arid lowlands of the West Coast Sandveld, which prompts a fresh synthesis as to the nature of late Quaternary environmental changes in the southwestern Cape's fynbos biome. The study is centred on Verlorenvlei, a remote coastal lake and swamp system which is ideally situated to investigate the complex interactions between late Holocene climate change, vegetation change, sea-level fluctuation, lacustrine/estuarine/fluvial sedimentology and human activity in the Sandveld region. In addition, this region of the West Coast has provided Quaternary scientists with a rich archaeological record against which independent lines of palaeoecological evidence can be evaluated. In support of the study, a wide range of palaeoenvironmental techniques has been applied to sediments sampled from the Verlorenvlei area. Organogenic deposits have been radiocarbondated and subjected to pollen analysis and assorted sedimentological and geoarchaeological assessments. Preliminary fossil pollen data from Elands Bay Cave, assembled for the period following the Last Glacial Maximum until approximately the terminal Pleistocene, are suggestive of moister and possibly cooler conditions in the Sandveld at this time. This is in contrast to prevailing evidence from the summer rainfall region of the subcontinent. Particle size analysis and an assessment of the in situ fossil Mollusca from vibracores, derived from the estuarine reaches of Verlorenvlei, reveal substantive evidence for rapid sea-level fluctuations along the West Coast during the mid-Holocene. Further inland, several mid-Holocene higher sea-levels are reflected in the palynology of lacustrine cores derived from Grootdrift and Klaarfontein. Detailed pollen diagrams, presented from Grootdrift, Klaarfontein, Muisbosskerm and Spring Cave, reflect the regional vegetation history during several periods over the last 7 000 years. There is convincing evidence from these data that the first half of the Holocene - commensurate with the Holocene hypsithermal - was associated with reduced moisture availability, and hence arid conditions along the West Coast. By contrast, there is evidence from the latter half of the Holocene that conditions ameliorated in the Sandveld around 3 000 BP and that moisture was, at this time more freely available. Following a hiatus in sedimentation some time after 4 000 BP, marine conditions are no longer visible in Verlorenvlei, having been replaced by fresh water as the dominant hydrological regime. A high resolution palynological investigation of the Grootdrift wetland sediments has contributed to a detailed palaeolimnological reconstruction of the upper Verlorenvlei system since the time of colonial expansion into the area, some 300 years ago. The picture reveals a sequence of rapid ecological changes in the face of progressive human disturbance. Arising from these insights, a number of recommendations for the management of dryland aquatic ecosystems such as Verlorenvlei, are presented. The significance of these late Quaternary palaeoenvironmental changes, in terms of the biogeography of plants and animals and also in terms of human occupation of the region, is examined

Tracing hydrological millennial-scale cycles in the late Quaternary of the Cariaco Basin and the southern Gulf of Cádiz using coccoliths and dinoflagellate cysts

Climate fluctuations in tropical to subtropical regions are coupled to hydrological changes. The reconstruction of these hydrological changes during rapid late Quaternary climate oscillations is crucial for climate change study. The present study demonstrates that coccoliths and dinoflagellate cysts are very useful as paleoclimatological indicators for the elucidation or a better understanding of the late Quaternary regional and global palaeoclimate. This study also reveals new insights in coccolithophore and dinoflagellate palaeoecology. At the outset, two fundamental studies were undertaken to strengthen dinoflagellate cysts as a proxy for paleoecological studies. Since so-called ‘standard’ palynological processing methods are still very variable and inflict damage on organic-walled microfossils to a certain extent, the effect on the determination of dinoflagellate cyst concentrations needed to be sorted out. Furthermore, since there were indications that process length variation of Lingulodinium machaerophorum is related to salinity, there was a need to assess its use for quantitative palaeosalinity reconstruction, which is of critical importance for better understanding of global climate change. Two locations were chosen for a high-resolution micropalaeontological study of hydrological millennial-scale cycles during Late Quaternary times: the Cariaco Basin, an anoxic basin offshore Venezuela and the Southern Gulf of Cádiz, offshore Morocco. Because of the high sedimentation rates, both sites contain a relatively undisturbed Late Quaternary climate record. Both record rapid, large climatic oscillations related to major hydrological changes caused by respectively the intertropical convergence zone (ITCZ) and the North Atlantic Oscillation (NAO). Results of the micropalaeontological analysis indicate that the changes in the dominance of river influx or upwelling cause important variations in plankton productivity in both locations. These variations are reflected in both assemblage changes and absolute abundance variation. Apart from the productivity reconstruction, changes in assemblage or morphology reflect changes in temperature and salinity. The seasonal and multi-year changes between upwelling and river dominated ecosystems, related in both regions to climatological shifts of respectively the ITCZ and NAO, can be extended to millennial-scale cycles and results in specific productivities, temperatures and salinities. Since millennial-scale shifts of both phenomena occur during the same periods (e.g. Younger Dryas), future work should elucidate the precise timing of both phenomena by comparing detailed multi-proxy records from north-south transects