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1
Sawada, Michael Charles. "Late quaternary paleoclimates and biogeography of North America." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9031.
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Pollen, spores, and dinoflagellate cysts are used with the modern analog technique (MAT) to provide paleoclimate reconstructions for terrestrial and marine environments in northeastern North America. Multivariate analysis of marine and nearby terrestrial pollen sequences from Hudson Bay, Labrador and the St. Lawrence, differentiate tundra, boreal and deciduous forest assemblages in time and space. These three regions had differing climate histories with respect to deglaciation and air mass boundaries. Prior to 6000 14C yr BP, cooler temperatures reconstructed along the Labrador margins agree with climate simulations indicating a persistent anticyclone over the Quebec-Labrador ice sheet. A late Holocene cooling at forest-tundra sites suggests a recent southern movement in the mean position of the polar front. The degree to which those critical thresholds of dissimilarity, that are used to identify non-analog pollen assemblages, are due to limitations of the modern pollen database or critical decisions within the MAT are explored by means of stochastic simulation, spatial statistics and graphical techniques. Critical thresholds of SQD, as derived by the expected value under randomization, become greater as the number of taxa in the pollen set increases. Larger pollen sets, with continentally infrequent but regionally abundant taxa, better distinguish between continental vegetation zones. Global and local spatial autocorrelation within climate anomalies indicate where the modern sample network induces biases in the climate reconstruction using the MAT. The spatial scale of terrestrial climate or vegetation reconstructions from pollen in lake-sediments is investigated through the study of pollen source area in southern Quebec. Despite the different regional vegetation, estimated pollen source areas and relevant pollen productivity for Pinus, Picea, Abies, Fagus, Quercus and Tsuga are consistent with studies from Michigan, Wisconsin and Sweden. These estimates are robust with respect to various plant abundance distance-weighting schemes and imply that the same inferences can be made regarding plant abundance from pollen throughout a lake-derived fossil pollen sequence. Stochastic simulations illustrate that the definition of relevant pollen source area requires consistent within-site vegetation heterogeneity within a network of pollen sites. Underutilized proxy-climate data from wetland taxa are demonstrated to contain climate signals at the continental scale and have the potential to further our climatic and biogeographic picture of North America over the past 21,000 years. Pollen and spores from modern wetland taxa conform to their geographic ranges and allow interpretations of their past range changes. The climatic tolerances that govern their geographic distributions are used to interpret past range changes in climatic terns. Sphagnum spore distributions suggest major peatland developments after 9 ka and 5 ka. Sphagnum, Potamogeton, Isoetes, Myriophyllum Typha/Sparganium, and Menyanthes trifoliata were in Alaska during the last glacial maximum (LGM) and moved into the ice-free corridor by 13 ka. Since the LGM, four migration routes for aquatic taxa are identified in response to the climate changes of the late Quaternary.
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Lacourse, Terri. "Late Quaternary vegetation history of Sulphur Lake, southwest Yukon Territory, Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0005/MQ36711.pdf.
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Simpson, Emily. "Paleoecology and Land-Use of Quaternary Megafauna from Saltville, Virginia." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etd/3590.
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Land-use, feeding habits, and response to seasonality by Quaternary megaherbivores in Saltville, Virginia, is poorly understood. Stable isotope analyses of serially sampled Bootherium and Equus enamel from Saltville were used to explore seasonally calibrated (δ18O) patterns in megaherbivore diet (δ13C) and land-use (87Sr/86Sr). Overall, this dataset suggests an open forest with relatively constant temperatures year round that were similar to modern conditions. Neither Bootherium or Equus individuals spent a significant amount of time at higher elevations in the nearby Blue Ridge geologic province. These analyses provide a unique perspective on long-term response of large mammals to climatic shifts and their impact on local ecosystems. Results are also relevant to modern conservation decisions, especially those surrounding highland grassy balds in the Appalachians, and their maintenance by grazing pressure.
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Herring, Erin Mauryeen. "Late Quaternary and Holocene paleoecology of interior mesic forests of northern Idaho." Thesis, University of Oregon, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3644438.
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The mesic forests distributed within the Rocky Mountains of northern Idaho are unique because many species contained within the forest are separated from their main distribution along the Pacific Northwest coast. It remains unclear whether most species within the inland disjunction survived the glacial periods of the Pleistocene, or whether they were more recently dispersed from coastal populations. To see if the dominant tree taxa of the mesic forests today could have persisted in a refugium south of the large ice sheets, four sediment cores were used to reconstruct the vegetation and climate history of the region. A nearly continuous record of pollen and sediment composition (biogenic silica and inorganic and organic matter) over the last ca. 120,000 years provides evidence of a dynamic ecosystem. Over a long timescale, the slow shifts in vegetation are attributed to the changes in climate. During the last interglacial period, the region was warmer and drier with a Pinus dominated mixed conifer forest. Approximately 71,000 years ago, a Pseudotsuga/Larix forest became established in the area as a response to the increased available moisture. As climate cooled and glaciers expanded the Pinus and Picea forest was the dominant vegetation type until ca. 40,000 years ago. The environment during the Last Glacial Maximum (LGM) was so harsh that no vegetation record was recorded. After the LGM, climate warmed, enabling a Pinus and Picea forest to establish and persist until the Holocene.
The mesic taxa that dominate the modern forests did not arrive in northern Idaho until the mid- to late-Holocene. The recent arrival of the dominant tree species, Thuja plicata and Tsuga mertensiana, suggests that they likely did not persist in a refugium during the last glaciation. Instead, these species recently dispersed from coastal populations, but expansion into their interior distributions was likely limited by both climate and species competition in already established forests. During the late-Quaternary, the deposition of thick tephra layers (>20 cm) from the eruptions of Glacier Peak (ca. 13,400 years ago) and Mt. Mazama (ca. 7,600 years ago) also facilitated an abrupt and persistent change in vegetation in northern Idaho.
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Bergolc, Melanie L. "A Paleoenvironmental Analysis Using Fossil Insects in Late Quaternary Deposits in Indiana and Ohio." Bowling Green State University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1092940677.
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Hu, Feng Sheng. "An ecosystem approach to the study of late-Quaternary environmental change in southwestern Alaska /." Thesis, Connect to this title online; UW restricted, 1994. http://hdl.handle.net/1773/5577.
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Herring, Erin. "Late Quaternary and Holocene Paleoecology of Interior Mesic Forests of Northern Idaho." Thesis, University of Oregon, 2014. http://hdl.handle.net/1794/18509.
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The mesic forests distributed within the Rocky Mountains of northern Idaho are unique because many species contained within the forest are separated from their main distribution along the Pacific Northwest coast. It remains unclear whether most species within the inland disjunction survived the glacial periods of the Pleistocene, or whether they were more recently dispersed from coastal populations. To see if the dominant tree taxa of the mesic forests today could have persisted in a refugium south of the large ice sheets, four sediment cores were used to reconstruct the vegetation and climate history of the region. A nearly continuous record of pollen and sediment composition (biogenic silica and inorganic and organic matter) over the last ca. 120,000 years provides evidence of a dynamic ecosystem. Over a long timescale, the slow shifts in vegetation are attributed to the changes in climate. During the last interglacial period, the region was warmer and drier with a Pinus dominated mixed conifer forest. Approximately 71,000 years ago, a Pseudotsuga/Larix forest became established in the area as a response to the increased available moisture. As climate cooled and glaciers expanded the Pinus and Picea forest was the dominant vegetation type until ca. 40,000 years ago. The environment during the Last Glacial Maximum (LGM) was so harsh that no vegetation record was recorded. After the LGM, climate warmed, enabling a Pinus and Picea forest to establish and persist until the Holocene.
The mesic taxa that dominate the modern forests did not arrive in northern Idaho until the mid- to late-Holocene. The recent arrival of the dominant tree species, Thuja plicata and Tsuga mertensiana, suggests that they likely did not persist in a refugium during the last glaciation. Instead, these species recently dispersed from coastal populations, but expansion into their interior distributions was likely limited by both climate and species competition in already established forests. During the late-Quaternary, the deposition of thick tephra layers (>20 cm) from the eruptions of Glacier Peak (ca. 13,400 years ago) and Mt. Mazama (ca. 7,600 years ago) also facilitated an abrupt and persistent change in vegetation in northern Idaho.
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Woolfenden, Wallace Bird 1941. "Late Quaternary vegetation history of the southern Owens Valley region, Inyo County, California." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282184.
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This study analyzes the pollen, spores, and algae in the upper 90 m section of a mostly continuous, well dated, 323 m core (OL-92) from Owens Lake, southeastern California. The entire core has produced a paleoclimatic record for the past ∼800 ka. The 90 m interval dates from ∼9 ka to ∼151 ka beginning with the penultimate glaciation and ending during the termination of the last glaciation. The record shows high amplitude fluctuations in the abundances of pine, juniper, saltbush, sagebrush, chenopods/amaranths, and Ambrosia-type pollen. High percentages of juniper pollen with low percentages of desertscrub pollen during the intervals ∼150 ka to ∼120 ka and 73 ka to ∼20 ka alternate with low juniper pollen and relatively high percentages of desertscrub and oak pollen during the intervals ∼118 ka to ∼103 ka and ∼18 ka ∼10 ka and into the Holocene. Sagebrush pollen varies with juniper pollen but has a tendency to lead it in time. Pine and fir pollen tends to vary inversely with juniper over the long term. These trends are interpreted as vegetation change in response to glacial-interglacial cycles: During cold-wet glacial climates there was a downslope expansion of juniper woodland and sagebrush scrub, contraction of Sierra Nevada mixed conifer forest, and displacement of warm desertscrub, suggesting average temperature and precipitation departures from modern values ranging from -2°C to -6°C and from +100 mm to +350 mm. Conversely under warmer and drier interglacials warm desert shrubs expanded their range in the lowlands, juniper and sagebrush retreated upslope, and the Sierran forests expanded. Estimated average temperature and precipitation departures from modern values ranged from -0.5°C to +3.7°C and +13 to -26 mm. Comparison of the pollen spectra spanning the penultimate and ultimate glacial maxima shows the former to have been longer and more intense, in accord with the Sierra Nevada glacial record. Similarly, the higher abundances of Ambrosia pollen during the last interglaciation, compared to the Holocene, indicate warmer temperatures in the former. The presence of high oak percentages also during the last interglaciation suggest an expansion of the summer monsoon. Finally, the match of the juniper curve with the marine oxygen isotope chronostratigraphy suggests a link between vegetation change in the southern Owens Valley and global climate.
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Anshari, Gusti Zakaria. "Late quaternary vegetation and environments in the Lake Sentarum Wildlife Reserve, West Kalimantan, Indonesia." Monash University, School of Geography and Environmental Science, 2000. http://arrow.monash.edu.au/hdl/1959.1/9252.
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Sugden, Jean Mary. "Late quaternary palaeoecology of the central and marginal uplands of the Karoo, South Africa." Doctoral thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/18278.
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Pollen analysis of organic sediments from vleis in upland areas of the Central and marginal Karoo has provided a vegetation history spanning the late Quaternary in the Winterberg, Sneeuberg, Nuweveldberg and Cederberg Mountains. Fossil pollen studies indicate moist conditions at the beginning of the Holocene, followed by a drier period. The second half of the Holocene (4 600 BP) is characterised by moister conditions, becoming drier towards the present and resulting in a decline in grasslands and an increase in Karoo-bushes. In the western Cape, the late Pleistocene (15 000 to 10 000 BP) was characterised by conditions moister than the present. This was followed by a drier period which ameliorated in the late Holocene. Although climatic fluctuations occurred, fynbos has been maintained in situ throughout the sedimentation period (14 600 BP), highlighting the dominant role of the substrate and secondary importance of climate. Climatic changes caused a shuffling of plant communities within the Fynbos Biome - this long uninterrupted history may be one reason for the high species diversity of fynbos. San hunter-gatherers, who occupied southern Africa prior to 4 000 BP, had a negligible impact on the vegetation. Khoi herders, who were first documented in the fossil record about 1 800 BP, had a slight impact on the vegetation, particularly by altering the fire regime. However, the arrival of European Trekboers some four hundred years ago had a significant effect on the environment. Although the general climatic trend in the Karoo is one of a drier phase, the decline in grasses and eastward movement of xeric Karroid elements has been accelerated due to mismanagement and sedentary farming techniques. An extensive contemporary pollen rain study has been undertaken to examine the representivity of these fossil pollen data. The investigation shows that contemporary pollen rain is a good reflection of the vegetation communities in the Karoo and Cederberg. Multiple discriminant analysis compares fossil pollen assemblages with contemporary pollen spectra and proved useful for determining whether modern analogues exist for the fossil pollen assemblages. TWISA confirmed the zones derived from discriminant analysis. Environmental changes have occurred in the Karoo during the late Quaternary, resulting in fluctuations and changes in vegetation patterns which have been accelerated in the recent past by human activity.
Bibliography: pages 293-318.
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Quillen, Amanda Kay. "Diatom-Based Paleolimnological Reconstruction of Quaternary Environments in a Florida Sinkhole Lake." FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/211.
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Despite lake sensitivity to climate change, few Florida paleolimnological studies have focused on changes in hydrology. Evidence from Florida vegetation histories raise questions about long-term hydrologic history of Florida lakes, and a 25-year limnological dataset revealed recent climate-driven effects on Lake Annie. The objectives of this research are (1) to use modern diatom assemblages to develop methods for reconstruction of climatic and anthropogenic change (2) to reconstruct both long-term and recent histories of Lake Annie using diatom microfossils. Paleoenvironmental reconstruction models were developed from diatom assemblages of various habitat types from modern lakes. Plankton and sediment assemblages were similar, but epiphytes were distinct, suggesting differences in sediment delivery from different parts of the lakes. Relationships between a variety of physical and chemical data and the diatoms from each habitat type were explored. Total phosphorus (TP), pH, and color were found to be the most relevant variables for reconstruction, with sediment and epiphyte assemblages having the strongest relationships to those variables, six calibration models were constructed from the combination of these habitat types and environmental variables. Reconstructions utilizing the weighted averaging models in this study may be used to directly reveal TP, color, and pH changes from a sediment record, which might be suggestive of hydrologic change as well. These variables were reconstructed from the diatom record from both a long-term (11,000 year) and short-term (100 year) record and showed an interaction between climate-driven and local land-use impacts on Lake Annie. The long-term record begins with Lake Annie as a wetland, then the lake filled to a high stand around 4000 years ago. A period of relative stability after that point was interrupted near the turn of the last century by subtle changes in diatom communities that indicate acidification. Abrupt changes in the diatom communities around 1970 AD suggest recovery from acidification, but concurrent hydrologic change intensified anthropogenic effects on the lake. Diatom evidence for alkalization and phosphorus loading correspond to changes seen in the limnological record.
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Holmes, Jonathan Anthony. "Pliocene and Quaternary environmental change in Kashmir, north-west Himalaya." Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:e9bb6cf8-93a8-4471-9c55-7ed84044dc3c.
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Late Cainozoic environmental changes in Kashmir (33°30' to 34°30' N: 74°10' to 75°30' E) have been reconstructed using a range of techniques. The sedimentary record in Kashmir consists of a thick (>1000m) basin-fill sequence known as the Karewa group, together with glacial and related sediments in the surrounding mountain flanks. The Karewa sediments are fluviolacustrine in origin and comprise alternations of conglomerates, sands and clayey silts. Work on the lower Karewa formation, which has previously been dated palaeomagnetically to between 4 and 0.4 MaBP, involved the semi- quantitative analysis of clay-mineral assemblages by X-ray diffraction.The clay minerals in the lower Karewa mudstones are interpreted as detrital clays which reflect weathering within Kashmir basin. The analyses showed a change in clay mineralogy between about 2.5 and 2.3MaBP, from abundant kaolinite to abundant smectite. Work on the upper Karewa formation involved field description and mapping of facies, sedimentological analysis, dating using thermoluminescence (TL) and amino-acid racemization, and analysis of ostracod assemblages from lacustrine sediments. Areal restriction of the lake in Kashmir occurred about 0.4MaBP with the rapid uplift of the Pir Panjal Range. Sedimentological data show that aeolian dust formed a major input into the lake. Ostracod assemblages show that the lake itself was cool, shallow, alkaline and had abundant plant macrophytes, The lake drained between 120 and SOkaBP. Stratigraphical, sedimentological and faunal evidence suggests that this was a result of tectonically-induced drainage rather than climatically-induced desiccation. The glacial history of the surrounding mountain flanks was reconstructed by field mapping of glacial sediments and dated using TL and radiocarbon methods. Present and past patterns of glaciation wore assessed by the determination of equilibrium-line altitudes (ELAs), glaciation thresholds (GTs) and cirque aJtitudes. Glaciers extended to 2150 m a.s.l in the Great Himalayan flank and 2600 m a.s.l. in the Pir Panjal. There is evidence for only 2 pre-Holucene advances in Kashmir, the older of which predates 35kaBP. Present patterns of glacierization indicate a SW to NE rise in the height of ELAs and GTs suggesting topographic and precipitation control. An apparent reversal of trends during the past is explained by Quaternary uplift of the Pir Panjal Range.
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Dilley, Thomas Edward 1959. "Late Quaternary loess stratigraphy, soils, and environments of the Shaw Creek Flats Paleoindian sites, Tanana Valley, Alaska." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282635.
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The late Quaternary stratigraphy of three Paleoindian archaeological sites, located on the edge of Shaw Creek Flats in the middle Tanana Valley, Alaska, consist of up to 2 meters of calcareous eolian sand, loess, and buried paleosols. Two Paleoindian occupations at the Broken Mammoth, Swan Point, and Mead sites date from 11,800 to 11,000 yr B.P. and from 10,800 to 9500 yr B.P. Well-preserved faunal remains, worked mammoth ivory, stone and organic tools, and at Swan Point, the early occurrence of microblades dating to 11,700 yr B.P., are associated with buried paleosols at the base of the loess. Stratigraphic and radiocarbon-chronological correlations between the sites, and at similar geological sections, suggest the presence of a regionally-correlative, eolian stratigraphy consisting of three main units: (1) a basal gray eolian sand, overlying a deflated, ventifacted, bedrock surface, was deposited as bluff-top sand sheets probably during the Birch Period transition from periglacial steppe-tundra environments to shrub tundra about 12,000 to 14,000 yr B.P. (2) An overlying lower loess unit contains three paleosol complexes, classified as Typic Cryorthents, which consist of a series of cumulative Abk horizons overlying Ck loess parent material. The lower paleosol complex dates to 11,800 to 11,000 yr B.P. as is associated with the initial occupation of the sites. The middle paleosol complex dates from 10,800 to about 9500 yr B.P. and is associated with the second Paleoindian occupation. The upper paleosol complex is weakly developed, contains no cultural material, and reflects an increase in loess deposition rates. Abundant pedogenic carbonate features indicate dry, warm, alkaline soil conditions. Faunal remains, soil characteristics, and regional palynological studies indicate a warm, dry, open parkland of poplar-willow scrub forest during the deposition of the lower loess, paleosol formation, and Paleoindian occupations. (3) An upper loess unit, up to a meter thick, lacks paleosols, has been leached of carbonate, and has a late Holocene Alfic Cryochrept soil developed on its upper surface. Rapid, coarse-grained loess deposition occurred from about 9000 to 6000 yr B.P. By 4500 yr B.P., slow, fine-grained loess deposition began under boreal forest conditions and continues today.
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Bergolc, Melanie. "A paleoenvironmental analysis using fossil insects in late Quaternary deposits in Indiana and Ohio." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=bgsu1092940677.
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Muiruri, Veronica Mwihaki. "Late Quaternary diatom and palynomorph stratigraphies and palaeoenvironments of the Koora Graben and Lake Magadi Basin, Kenya Rift Valley." HKBU Institutional Repository, 2017. https://repository.hkbu.edu.hk/etd_oa/461.
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Two sets of cores were recovered from the southern Kenya Rift (Koora and Magadi basins) through the Hominid Sites and Paleolakes Drilling Project and the Olorgesailie Drilling Project. These contain a detailed environmental Quaternary history with records of up to ~1 million years. This period correlates with much of the Olorgesailie Formation record of 1.2 Ma in the Olorgesailie Basin. The Magadi cores reached trachyte at ~ 194 and 133 m with this project focussed on the longer core, MAG14-2A, which includes limestone, zeolitic, laminated and massive clay and silt, massive mud, chert, trona, gravel and sand. The Koora Core (OLO12-1A) extended to depths of 166.14 m and contains laminated and massive diatomites, fine to coarse sands; lime and siliciclastic muds with pumice-rich gravels. The two cores are particularly important because they provide environmental records that help to fill erosional gaps in the history of the Olorgesailie Basin, which includes important evidence for changing hominin cultures and evolution. The high-resolution lacustrine-terrestrial stratigraphies of the two basins have shown how landscapes were transformed because of complex interactions between tectonic and climatic processes. Volcanism also had a significant impact, partially damming lakes at Olorgesailie. Diatoms are present in much of the Koora Basin sequence and large parts of the Magadi sediments. These are dominated by a variety of planktonic Aulacoseira, Cyclotella and Thalassiosira taxa in both basins. Species comprising these genera and other planktonic, benthonic and epiphytic taxa preserve a detailed record of lakes that fluctuated in depth, extent and chemistry. The data document the presence of freshwater and saline lakes as well as wetlands. Diatom transfer functions from the Koora and Magadi basins indicate that these water bodies fluctuated widely in conductivity between ~200 to >20,000 µs cm−1, with pH changing between about 7.5 and 11.5. The palaeolakes also periodically exceeded diatom tolerance limits and intermittently dried out. Pollen are generally lacking in the Koora basin sediments, but deposits in the Magadi core contain common pollen that document a wide range of habitats, including forests, woodlands and grasslands that could have supported the presence of hominins and their activities in the region. Fungal spore data support pollen inferences and indicate periods when large mammals might have been common. The microfossil record shows that there was a broad trend towards more arid conditions in the southern Kenya Rift after about 510 Ka, interrupted by periodic wetter conditions. A major episode of desiccation developed between about 450 Ka to 400 Ka that partially correlates with a period of mammal extinctions and a change from Acheulean to Middle Stone Age toolkits in the Olorgesailie Basin, suggesting that these changes might have been related to environmental conditions at that time.
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Cañellas, Boltà Núria. "Dinàmica de la vegetació en relació amb els canvis climàtics, els processos geològics i l'impacte humà a l'illa de Pasqua des del Glacial tardà. Estudi paleoecològic dels sediments del llac Rano Raraku." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/145926.
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Aquesta tesi doctoral es centra en la paleoecologia de l’Illa de Pasqua (Rapa Nui) (27ºS 109ºW). El present treball ha caracteritzat la vegetació a la conca del llac i la seva dinàmica com a resposta als canvis ambientals durant els darrers 34000 anys a partir d’indicadors ambientals (macrorestes vegetals, diatomees, registre palinològic, geoquímic i fàcies sedimentari) analitzats en sediments de testimonis de sondeig del llac Raraku. Els resultats han evidenciat variacions significatives en la composició de la vegetació en relació a canvis climàtics a llarg termini, modificacions de la morfologia de la conca per rebliment sedimentari i, en els últims tres mil•lennis, les activitats humanes. El llac Raraku i els seus entorns han experimentat grans canvis transformant-se d’un llac profund amb forts pendents envoltat per un palmerar obert a un llac somer amb vegetació dominada per palmeres, desprès a una torbera amb una successió de plantes dominants, el retorn a condicions de llac, i finalment el reemplaçament dels palmerars de l’entorn per vegetació herbàcia. A més a més, s’han observat fluctuacions menors en la vegetació durant el període glacial i la desglaciació, que podrien ser conseqüència de canvis climàtics ràpids com el Younger Dryas i esdeveniments Heinrich (H1-H3), donant suport a la hipòtesi de l’ocurrència d’aquests fenòmens a la regió del Pacífic Sud. En el treball s’ha dut a terme l’anàlisi de la successió sedimentaria més contínua fins el moment pels darrers 3,7 cal ka BP. L’estudi ha caracteritzat el reemplaçament de la vegetació dominada per palmeres per prats, iniciat el c. 2,4 cal ka BP, com un procés llarg i gradual-esglaonat en contrast amb el patró sobtat d’estudis anteriors. La presència i expansió de la planta ruderal d’origen americà Verbena litoralis, juntament amb la correlació significativa del seu augment amb increments en el registre de carbó, suggereixen la implicació de les activitats humanes en aquest procés de reemplaçament. L’identificació de hiatus sedimentaris suggereixen la contribució del clima als canvis de vegetació. Aquests resultats indiquen el probable establiment de l’home a l’illa 1500 anys abans de la data actualment acceptada, i el possible paper de poblacions provinents d’Amèrica. La magnitud i rapidesa dels canvis de vegetació a causa de les variacions climàtiques i del rebliment del llac des del final de l’últim glacial són similars als ocorreguts durant la presència humana. D’altra banda s’han identificat restes macrofòssils com a possibles indicadors de condicions ambientals i s’ha reconegut per primera vegada la presència d’una nova planta nativa a l’illa actualment extirpada: Dianella cf. intermedia/adenanthera.This dissertation focuses on the paleoecology of Easter Island (Rapa Nui) (27°S 109°W). The study has characterised vegetation of the lake’s basin and its dynamics in response to environmental changes during the past 34000 years from several environmental indicators (macroremains plants, diatoms, palynological, geochemical and sedimentary facies records) analized in lacustrine sediment cores of lake Raraku. The results show significant changes in the composition of the vegetation in relation to long-term climatic changes, variations on the lake basin morphology due to sedimentary infilling and human activities in the last three millennia. Lake Raraku and its surroundings have undergone significant changes, such as the transformation of the deep lake surrounded by open palm grove into a shallow lake with palm-dominant vegetation around, the hydrosere succession into a mire with a plant succession, the return to lake conditions, and finally the replacement of palm vegetation by herbs. Moreover, small fluctuations in vegetation during the glacial period and deglatiation have been observed and could be the result of rapid climate changes such as the Younger Dryas and Heinrich events H1-H3. This supports a wide occurrence of these events, including the Pacific South region. The multiproxy analysis of the most continuous sequence to date for the last 3.7 ka BP has characterised the replacement of palm-dominated vegetation by grasslands as a long and gradual process, starting at c.2.4 ka BP, in contrast with the abrupt pattern from previous studies. The presence of the weed of American origin Verbena litoralis, together with significant correlation with charcoal increases, suggest the involvement of human activities in the replacement process. Sedimentary gaps observed in the sequence suggest the contribution of climatic effects as well. These results indicate that human settlement occurred likely 1500 years before the date currently accepted, and a possible role of people coming from America. The study shows that vegetation changes due to climate and lake basin morphological variations are similar in rate and magnitude to those occurred during human presence. On the other hand, several macrofossil remains have been identified as potential indicators of environmental conditions and the presence of a new plant native to the island, now extirpated, Dianella cf. Intermediate/adenanthera, has been recognized for the first time.
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Gause, Austin. "Paleoenvironmental Reconstruction of Quaternary Saltville, Virginia, using Ostracode Autecology." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/etd/3783.
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The Saltville valley in southwestern Virginia is home to Quaternary localities containing paleontological and archaeological remains. Historically the valley has been mined for salt and the small lakes, ponds and springs along the valley floor have a brackish signature. A preliminary report on the site’s ostracode fauna suggested that the site’s water was not always saline. This study analyzed modern and Quaternary ostracodes to understand the valley’s hydrologic and chemical evolution. Sediments contained primarily freshwater species, including the environmentally sensitive Candona crogmaniana. The presence of Pelocypris tuberculatum and a new Fabaeformiscandona species throughout a vertical section spanning the latest Pleistocene and Holocene suggests that ephemeral pools were being fed by freshwater springs throughout the latest Quaternary. Climate ranges, estimated through species autecology and MOTR, reveal that the site’s mean annual temperature was between 0 - 19.1℃. Ostracode salinity tolerances suggest that the site was fresh during the sampled record.
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Yu, Zicheng. "Late Quaternary paleoecology of the southern Niagara Escarpment, Ontario, Canada, a multiple proxy investigation of vegetation and climate history." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq28098.pdf.
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Paixão, Jesus da Silva. "Contribuição à paleoecologia da Amazônia Meridional na planície de inundação do Rio Teles Pires, do norte do Estado do Mato Grosso." Universidade Federal de São Carlos, 2010. https://repositorio.ufscar.br/handle/ufscar/1673.
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Previous issue date: 2010-04-24Records of isotopic and elemental carbon and nitrogen and pollen in lake sediments and soils have been used for studies of Quaternary paleoecology worldwide, including in the Amazon at specific sites, such as the region of Carajas, Lake Pata and Region Porto Velho in Rondonia state making it necessary to register in the central southern region. We collected two cores in the Lagoa Jabuti site and a core on the Site Três Coqueiros in the floodplain of the Teles Pires river in northern Mato Grosso state. The cores were analyzed for elemental and isotopic nitrogen and carbon (% C, % N, 13C, 15N and C/N), and palynology and radiometric dating by 14C via AMS. Was also used samples of Quaternary megafauna and elements of material culture. From the analysis carried out it appears that southern Amazon in the Mato Grosso there were no significant ecological changes during the study period, which is around 5,500 years B.P., except for the registration of a relatively sharp change in carbon isotope values for about 2,700 years BP. The pollen analysis of the sediment of Jabuti showed the predominance of elements on forest herb/fern coinciding with data from botanical surveys conducted in the area in which stand families Fabaceae, Arecaceae, Euphorbiaceae, Malvaceae, Combretaceae, Melastomataceae, Annonaceae, among the trees; Cyperaceae , Asteraceae, Chenopodiaceae, Poaceae, Achantaceae and Amaranthaceae between herbs and Polygonaceae, Cyatheaceae and Asplenium among the ferns. The megafauna considered in the paper presented by ESR beyond the age covered by the project and analyzed the material culture (ceramics) revealed that from the earliest moments of occupation (about 1,300 years BP) the ecological conditions of the region have not changed, although they have been registered large gaps in regional occupation that can be interpreted as a crisis in the supply of natural resources necessary for survival in the region.
Registros de dados isotópicos e elementares de carbono e nitrogênio e palinológicos em sedimentos lacustres e solos têm sido utilizados para estudos da paleoecologia do Quaternário em todo mundo, inclusive na Amazônia em sítios específicos, a exemplo da região de Carajás, Lagoa da Pata e região de Porto Velho no estado de Rondônia fazendo-se necessário o registro na região centro meridional da região. Foram coletados dois testemunhos de sondagem na Lagoa Jabuti e um testemunho no Sítio Três Coqueiros na planície de inundação do rio Teles Pires no norte de Mato Grosso. Os testemunhos foram analisados elementar e isotopicamente para nitrogênio e carbono (%C, %N, 13C, 15N e C/N), além de palinologia e datação radiométrica pelo 14C via AMS. Foram ainda utilizadas amostras da megafauna quaternária e elementos da cultura material. A partir das análises executadas, especialmente δ13C (-222 a - ) verifica-se que na Amazônia Meridional matogrossense não ocorreram significativas mudanças ecológicas no período estudado, que está em torno dos 5.500 anos, exceto pelo registro de uma alteração relativamente acentuada nos valores isotópicos de carbono há cerca de 2.700 anos A.P. A análise palinológica dos sedimentos da Lagoa Jabuti evidenciaram a predominância de elementos florestais sobre ervas/pteridófita coincidindo com os dados de levantamentos botânicos efetuados na região em que sobressaem famílias Fabaceae, Arecaceae, Euphorbiaceae, Malvaceae, Combretaceae, Melastomataceae, Annonaceae, entre as arbóreas; Cyperaceae, Asteraceae, Chenopodiaceae, Poaceae, Achantaceae e Amaranthaceae entre as ervas e Polygonaceae, Asplenium e Cyatheaceae entre as pteridófitas. A megafauna considerada no trabalho apresentou pelo ESR idade além da abrangida pelo projeto e a cultura material analisada (cerâmica) revelou que desde os primeiros momentos de ocupação (cerca de 1.300 anos A.P.) as condições ecológicas da região não se alteraram, ainda que tenham sido registrados grandes hiatos na ocupação regional que podem ser interpretados como crises no fornecimento de recursos naturais fundamentais para a sobrevivência na região.
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Anderson, Rodney Scott. "LATE-QUATERNARY ENVIRONMENTS OF THE SIERRA NEVADA, CALIFORNIA." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184205.
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The pollen, plant macrofossil and aquatic fossil stratigraphies from a transect of sites in the Sierra Nevada, California, were examined to deduce paleoenvironmental change since the late-Wisconsinan. Fossil pollen samples were compared to modern pollen samples from both sides of the Sierra Nevada crest. Modern samples corresponded largely to modern vegetation units, validating the use of pollen for this purpose in mountainous environments. Vegetation change during the Holocene was largely contemporaneous on both sides of the crest at elevations where lake cores and meadow sections were analysed. Deglaciation occurred by ca. 12,500 yr BP at a site on the east side, and by ca. 11,000 yr BP at a west side site. Prior to ca. 10,000 yr BP, few trees were found around the higher elevation sites. An open forest with trees characteristic of the modern Sierra Montane and Upper Montane forest grew around the mid- to high elevation sites by the early Holocene. Montane chaparral species, such as bush chinquapin, mountain mahogany and probably huckleberry oak, with sagebrush, were most abundant then. Along with lowered lake levels or absence of perennially standing water, and greater affinities to modern pollen samples from the more arid east side, these observations suggest drier conditions than today. However, by ca. 6500-5500 yr BP, effective precipitation increased, as shown by increases in subalpine conifers (mountain hemlock and red fir) and higher lake levels, and less affinities to modern samples from the east side. Modern vegetation developed at most sites within the last 2-3 millenia. Specific changes in the vegetation at this time included a reduction in upper elevational limits of mountain hemlock and red fir, with possible downslope retreat of whitebark pine, indicating greater cooling and/or wetter conditions. This is consistent with the record of wet meadow genesis as well as tree-ring and Neoglacial chronologies.
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Westaway, Kira E. "Reconstructing the Quaternary landscape evolution and climate history of western Flores an environmental and chronological context for an archaeological site /." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20070117.170105/index.html.
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Gossen, Candace Lynn. "Deforestation, Drought and Humans: New Discoveries of the Late Quaternary Paleoenvironment of Rapa Nui (Easter Island)." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/782.
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The mystery of the trees of Rapa Nui (Easter Island) is a complex problem within a dynamic ecosystem. With new physical cores from the volcanic crater lake Rano Kao, this dissertation uncovers a detailed 15,000 year ecological history of Easter Island and its climatic variability. New radiocarbon dating methods establish a more precise chronology which shows that the island before human habitation was very different than what we know today. It had a simple but prolific ecology that transitioned into a barren grassland. What factors caused the transition are unclear but are likely to be human related. As the forests slowly disappeared, it could have triggered changes in regional and local climate, particularly rainfall, which generally leads to a rapid loss of ecosystems. With virtually stable climate conditions over the last 2,000 years, Easter Island has lost 33 species of plants including the giant palms, and still has not recovered today. This research challenges the previously accepted theory that humans deforested the island for the sole purpose of moving the Moai around, and focuses rather on uncovering the role of climate change that may have altered the ecosystem. New cores were obtained in 2005 from Rano Kao that were radiocarbon dated using scirpus seeds. The nine meters of core were sampled for oxygen isotope analysis of the lake water changes, a new science to the island. Detailed palynological studies of pollen and non-pollen palynomorphs uncovered changing vegetation patterns that aligned with a 700 year drought cycle. Conclusions support a cool-dry event that occurred 545 years ago, at which time the giant palms disappeared. While it was not the focus of this study, evidence confirms human occupation for more than 500 years before the disappearance of the trees.
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Becker, Bárbara Fernandes. "Evolução paleoambiental em salinas da Nhecolândia no holoceno superior, Pantanal sul-matogrossense." Universidade Federal de Mato Grosso, 2014. http://ri.ufmt.br/handle/1/588.
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CAPES
A região de Nhecolândia possui uma paisagem distinta quando comparadas às outras regiões do Pantanal, pois comporta áreas de lagoas limitadas por cordilheiras, faixas de areia, e que podem estar interligadas por vazantes. Algumas dessas lagoas possuem índices de salinidade podendo chegar até hipersalino. Acredita-se que a origem desses lagos tenha sido nos últimos cinco mil anos. Aqui, apresentam-se análises palinológicas e de geoquímica orgânica de sedimentos coletadas em duas lagoas salinas na região de Nhecolândia, MS. Os dados indicam que há 3.410 +/- 30 anos AP a vegetação em volta da lagoa foi composta por Bromeliaceae, Asteraceae, Arecaceae, Amaranthaceae e Nymphaceae. Registros de Cabomba sp. há 2.300 anos AP mostram que os índices de salinidade ainda permitiam a existência de macrófitas aquáticas dentro da lagoa. A partir de cerca de 1.200 anos AP, aumento na quantidade de COT associados a grãos que indicam florestas sazonalmente inundáveis sugerem o estabelecimento de vegetação semelhante à atual.
The region of Nhecolândia has a distinct landscape when compared to other Pantanal regions since it bears areas with ponds limited by Cordilheira forest, sand stripes and that may be connected by ebb tides. Some of these pounds have salinity indexes that may reach the hyper-salinity. It is believed that the origin of these lakes was in the last 5 thousand years. Here, it is presented palinological and organic geochemistry analysis of sediments collected at two saline pounds at the region of Nhecolância, MS. The obtained data indicate that at 3.410 years BP the vegetation surrounding the pound was composed by Bromeliaceae, Asteraceae, Arecaceae, Amarantaceae and Nymphaceae. Registers of Cabomba sp. at 2.300 years BP show that the salinity indexes still allow the existence of macrophytes inside the pound. Beyond 1.200 years BP, the increasing in the quantity of COT associated to grains that indicate seasonal floodable forests, suggest the establishing of vegetation similar to the current one.
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Lazar, Kelly Best. "Benthic foraminifera as paleo-sea-ice indicators in the western Arctic Ocean." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417617424.
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Black, Manu School of Biological Earth & Environmental Sciences UNSW. "A late quaternary palaeoenvironmental investigation of the fire, climate, human and vegetation nexus from the Sydney basin, Australia." Awarded by:University of New South Wales. School of Biological, Earth and Environmental Sciences, 2006. http://handle.unsw.edu.au/1959.4/25745.
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It is widely believed that Australian Aboriginals utilised fire to manage various landscapes however to what extent this impacted on Australia???s ecosystems remains uncertain. The late Pleistocene/Holocene fire history from three sites within the Sydney Basin, Gooches Swamp, Lake Baraba and Kings Waterhole, were compared with archaeological and palaeoclimatic data using a novel method of quantifying macroscopic charcoal, which is presented in this study. The palynology and other palaeoecological proxies were also investigated at the three sites. The Gooches Swamp fire record appeared to be most influenced by climate and there was an abrupt increase in fire activity from the mid-Holocene perhaps associated with the onset of modern El Ni??o dominated conditions. The Kings Waterhole site also displayed an abrupt increase in charcoal at this time however there was a marked decrease in charcoal from ~3 ka. Lake Baraba similarly had displayed low levels of charcoal in the late Holocene. At both Kings Waterhole and Lake Baraba archaeological evidence suggests intensified human activity in the late Holocene during this period of lower and less variable charcoal. It is hence likely that at these sites Aboriginal people controlled fire activity in the late Holocene perhaps in response to the increased risk of large intense fires under an ENSO-dominated climate. The fire history of the Sydney Basin varies temporally and spatially and therefore it is not possible to make generalisations about pre-historic fire regimes. It is also not possible to use ideas about Aboriginal fire regimes or pre-historic activity as a management objective. The study demonstrates that increased fire activity is related to climatic variation and this is likely to be of significance under various enhanced Greenhouse scenarios. There were no major changes in the composition of the flora at all sites throughout late Pleistocene/Holocene although there were some changes in the relative abundance of different taxa. It is suggested that the Sydney Sandstone flora, which surrounds the sites, is relatively resistant to environmental changes. Casuarinaceae was present at Lake Baraba during the Last Glacial Maximum and therefore the site may have acted as a potential refugium for more mesic communities. There was a notable decline in Casuarinaceae during the Holocene at Lake Baraba and Kings Waterhole, a trend that has been found at a number of sites from southeastern Australia.
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Awad, Lara. "Dynamique des forêts de sapin de Cilicie au Liban et changements globaux : apports des analyses palynologiques et génétiques." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20087/document.
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Le Liban est un pays qui constitue un carrefour des civilisations. Depuis le temps des pharaons, ses ressources forestières ont été exploitées, notamment pour le commerce du bois. Le Liban, connu pour son cèdre, possède une autre espèce emblématique, le sapin de Cilicie, dont les forêts sont en majorité non protégées. Historiquement, le bois de sapin a été exploité durant le Nouvel Empire égyptien ancien pour la construction des temples et des navires. Il représentait ainsi un signe de pouvoir du pharaon, en formant notamment la barque d'Amon. De même, le sapin a été coupé pour la construction du temple de Jérusalem, ainsi que des instruments de musique et de guerre. La fragmentation des sapinières au Liban n'est pas ancienne mais cette faible divergence se traduit cependant par un dème Nord-Est englobant 11 populations et un dème Sud-Ouest englobant 4 populations qui semblent être le résultat de deux processus démographiques consécutifs ou simultanés durant l'histoire du sapin au Liban. Le premier est un phénomène de migration en altitude en réponse à des changements dans l'environnement ou le climat. La reconstruction de la dynamique passée du sapin au Liban a montré que le sapin a subi des fluctuations importantes dans sa taille, depuis le Tardiglaciaire, il y a 14,000 ans. Notamment, le sapin a connu des périodes d'absence du registre pollinique qui pourrait être liées à la fragmentation anthropique de l'habitat ou à des extinctions locales ou contraction de l'aire de répartition. De même, il a connu des périodes d'expansion notamment au cours des événements de sécheresse dans le climat, notamment à 4090 cal. BP, à 5010 cal. BP et de 7800 à 8090 cal. BP. La richesse en allèles privés dans le dème Nord-Est indique la présence de plusieurs micro-refuges glaciaires de basses et de hautes altitudes, ainsi que des zones de suture issues de la recolonisation. Dans le dème Sud-Ouest, une recolonisation postglaciaire en altitude à partir du seul micro-refuge glaciaire détecté est probable. Le deuxième phénomène est lié à une migration asymétrique des populations génétiquement diversifiées du centre du dème vers les populations marginales génétiquement peu diversifiées. Ce processus, qui semblait être le résultat de la faible taille des populations cibles, pourrait permettre de retarder l'extinction des populations marginales, localement menacées. La superformance de la migration sur la dérive génétique et la dispersion sur des longues distances de 15 à 20 km constituent les effets médiateurs de ces processus démographiques. L'empreinte de cette dynamique démographique est une réduction historique de la taille effective des populations sur le long terme avec un signal ancien plutôt que récent, et une diversité génétique et richesse allélique basses. Cette diversité génétique semble être façonnée par les effets anthropiques ainsi que par les changements dans l'environnement ou le climat. La conservation in situ et ex situ de ces sapinières est nécessaire pour préserver leur patrimoine historique et génétiqueThe Lebanon is a country that constitutes a crossroads of civilizations. Back in the time of pharaohs, fir forests in Lebanon were exploited, particularly for the timber trade. Lebanon, known for its cedar, has another emblematic species, the Cilician fir, whose forests are in majority unprotected. Historically, the fir was used during the ancient Egyptian New Kingdom rule over Phoenicia for the construction of temples and ships. Notably, it represented a sign of power of the pharaoh, forming the sacred barque of Amun. Similarly, this tree was cut from Lebanon to build the temple of Jerusalem, as well as for making instruments of music and war. The fragmentation of the fir populations in Lebanon is not ancient but their low divergence, however, is marked by a Northeastern Ridge including 11 populations and a Southwestern Ridge including 4 populations that seem to be the result of two consecutive or simultaneous demographic processes during the history of fir in Lebanon. The first is a phenomenon of altitudinal migration in response to changes in the environment or climate. The reconstruction of the past dynamics of fir in Lebanon showed that it has undergone significant fluctuations in size, since the Late Glacial, 14,000 years ago. In particular, the tree has experienced periods of absence from the pollen record that could be related to anthropogenic habitat fragmentation or to local extinctions or contraction of the range of distribution. Similarly, there have been periods of expansion especially during periods of drought in the climate, at 4090 cal. BP, at 5010 cal. BP and between 7800 and 8090 cal. BP. The private allelic richness in the Northeastern Ridge indicated the presence of multiple glacial microrefugia of low and high elevations, as well as suture zones issues from recolonization. In the Southwestern Ridge, postglacial altitudinal recolonization from single microrefugial population is moslty probable. The second phenomenon is related to an asymmetric Northeast-Southwest migration from genetically diverse populations towards marginal and less genetically diverse populations. This process, which seems to be the result of the small size of the target populations, could help delay the extinction of marginal populations, locally threatened. The outperformance of migration over genetic drift and the dispersal over long distances of 15 to 20 km constitute the mediating effects of these demographic processes. The footprint of these population dynamics is a historic reduction in the effective population size on the long-term rather than on the short term, and weak genetic diversity and allelic richness. This genetic diversity seems to be shaped by anthropogenic effects as well as by changes in the environment or climate. In situ and ex situ conservation of fir populations in Lebanon is necessary to preserve their historical and genetic heritage
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Avery, Graham. "Avian fauna, palaeoenvironments and palaeoecology in the late quaternary of the Western and Southern Cape, South Africa." Doctoral thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/22441.
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Bibliography: pages 171-197.Avian remains in coastal archaeological samples from Eland's Bay Cave, Die Kelders Cave 1 and Nelson Bay Cave in the Cape Province, South Africa, cover the periods between 80 000 and 40 000 B.P. and 18 000 and 300 B.P. Results of modern comparative surveys indicate that beached birds provide a predictable food supply. Kolmogorov-Smirnov two-sample nonparametric tests confirmed the close resemblance between the relative proportions of seabirds in archaeological and beached assemblages and earlier assumptions that the composition of seabird samples in archaeological sites could not otherwise have been achieved. It is shown that this simple but effective practice has a history going well into the Middle Stone Age. Kolmogorov-Smirnov tests for differences between the relative proportions of skeletal elements of Cape cormorants preserved in archaeological and modern jackal accumulations provided a useful means of drawing attention to possible activity of jackals and/or domesticated dogs. Recognition that diagenesis in some earlier samples may mimic the characteristics of modern jackal samples has established the need to extend the comparison of skeletal elements to additional species and to study the relative durability of avian skeletal elements. Similar comparison with the proportions of modern mammalian and avian predator prey species and size (mass) categories provided no indication that black or martial eagles might have contributed to the samples. Similarly, present knowledge of Cape eagle owls argues against their being likely inhabitants of caves suitable for occupation by people. It is concluded that people were the primary accumulators of the assemblages studied and that the role of small food items in prehistoric subsistence can be addressed with greater confidence. Correspondence analysis was used to determine the existence of seasonality in the modern beached seabird samples. The profiles of the archaeological samples are plotted in relation to months in which they were most likely to have been collected. Seasonal evidence from species not subjected to the correspondence analysis supported these results. The results obtained closely supported the hypothesis for seasonal exploitation of the coast. It was also possible to indicate that visits were probably of short duration and that their timing varied. Exploitation of seabirds did not coincide with the period of maximum availability of beached birds. Comparison of the avian evidence with that from seals, Cape dune mole rats and steenbok/grysbok suggested that small food items comprised part of a seasonal strategy that made maximum use of a range of seasonal resources. Evidence for significant local environmental change in addition to, and in support of, existing information has been obtained. Fluctuations in marine, freshwater and terrestrial birds at Eland's Bay Cave have been related to evidence for changes in terminal Pleistocene and Holocene sea levels and the position of the coast, and in the morphology of Verlorenvlei. At Die Kelders Cave 1 between 80 000 and 40 000 B.P., previously drier conditions were ameliorating and mixed scrub and grass and freshwater existed on the coastal foreland in the vicinity of the cave. Fluctuations in frequencies of seabirds indicate that the sea level rose slightly and then receded during the period of deposition. At Nelson Bay Cave samples indicate the approach of the coast after the Last Glacial Maximum, the disappearance of grassland and its replacement by scrub and bush as significant elements of the vegetation. Freshwater birds did not respond as expected, however, indicating that their interpretation at Nelson Bay Cave is complex and not consistent with evidence for wetter or drier conditions. A possible link has been shown to exist between fluctuations of albatrosses, petrels and shearwaters at Nelson Bay Cave and the intensity of wind patterns which are related to oceanic and atmospheric circulation. Further investigation should establish whether seabirds would provide an index of climatic conditions without support from other sources.
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Balch, Deborah P. "Quaternary Ostracode Paleoecology and Its Link to Climate Change in the Bonneville Basin: A Detailed Study of the Glad800 Core GSL00-4, Great Salt Lake, Utah." Thesis, The University of Arizona, 2003. http://hdl.handle.net/10150/249251.
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We report the results of a detailed paleoecological study of the Bonneville Basin covering the last ~240,000 years. Our study used fossil ostracodes and a sedimentological record obtained from the August 2000 GLAD800 drilling operation at the Great Salt Lake. We analyzed 125 samples, taken at ~1 meter intervals from core GSL00-4, for ostracodes and other paleoecologic and sedimentological indicators of environmental change. Multivariate analyses applied to the ostracode data indicate an alternation between three major environments at the core site over the cored interval. The environments fluctuated most often between shallow saline, open -water lake conditions (when the lake was high enough to inundate the core site) and salt or freshwater, spring -fed marsh (when the water level was at or lower than the core site). But occasionally, the core site was submerged by deep fresh water. Immediately following deep lake phases, crashes in lake level from rapid desiccation resulted in the deposition of thick evaporite units. These environmental changes are consistent with shoreline studies of regional lake level fluctuations, but provide considerable new detail on both the timing and environmental conditions associated with the various lake phases. Our age model (using dates obtained from ¹⁴C, U- series, tephra and biostratigraphic chronologies) allowed us to associate the core's record of regional paleohydrology to the marine oxygen isotope stages record of global climate change. The core contains high resolution, continuous records for the last three glacial/interglacial sequences. In each case we found that fresh open-water conditions (i.e. lake highstands) correspond with maximum glacial advances, except for the smaller, less intense OIS 4 glaciation, when the lake remained saline. Salt and freshwater marshes were dominant environments for most of the interglacials. However, throughout most of the Quaternary, this basin has contained a shallow, saline open-water lake.
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De, Deckker P. "Australian Quaternary studies : a compilation of papers and documents submitted for the degree of Doctor of Science in the Faculty of Science, University of Adelaide /." Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09SD/09sdd299.pdf.
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Figueroa, Rangel Blanca. "Long-term forest dynamics in high-altitude mountains of West-Central Mexico : the human and climate dimension in the Holocene." Thesis, University of Oxford, 2007. http://ora.ox.ac.uk/objects/uuid:30826402-1eb7-4d94-9a07-4d376c16eea0.
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This thesis presents the results of a study to examine long-term forest dynamics in the high-altitude mountains of West-Central Mexico. Vegetation dynamics on temporal scales ranging from 102 to 103 years were reconstructed in order to provide essential information on the temporal variability of ecological patterns and processes in these forests; information that is of direct relevance for their current and future conservation and management strategies. Vegetation and palaeoecological methods undertaken included fossil and modern pollen analysis, vegetation surveys, microfossil charcoal analysis, magnetic susceptibility, inorganic and organic geochemistry, radiocarbon and 210Pb dating. These were used to evaluate the long-term dynamics of three forest types; Pine Forest, Cloud Forest and Transitional Forest on timescales spanning the past 4260, 1340 and 1230 years respectively. The main drivers of change were climate and disturbance events induced by climate fluctuations, for example increased fire frequency. The reconstructed records indicate that the sequences from the Cloud Forest and the Transitional Forest spanned two wet and one dry climatic interval while the Pine Forest sequence spanned two dry and two wet periods. The impact of these climatic fluctuations was significant on all three forest types and resulted in variations in forest diversity, taxonomic turnover and successional change. The climate change episodes observed in these records seem to be the local manifestation of climatic events that were occurring throughout Mexico at these intervals in time. Human influences were evident in the three forests through the appearance of cultural taxa, particularly during the driest period (~ 1200 yr BP). There is little evidence from these records, however, to suggest a widespread clearance of the landscape for agriculture. Results from this study support the current conservation and management recommendations for Cloud Forest to exclude timber extraction, grazing and agricultural activities from this forest type. In the Pine Forest, human interventions such small-scale agriculture, prescribed burning and silvicultural actions are in agreement with the longterm pine ecology and as such, total exclusion of human activities is not necessary. For the Transitional Forest, results from this study suggest that there needs to be the establishment of adequate plans to reduce frequent fires to arrest the development of prone-to-fire taxa.
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Barbour, Wood Susan L. "Quantitative Ecological and Taphonomic Patterns in Late Cenozoic Mollusk-Dominated Marine Fossil Assemblages." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/27710.
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Applications in paleontological research are far from being limited to taxonomic collection and identification. Nor is such research limited to working solely on fossil data. Actualistic paleontology is the study of modern or recent organisms and processes to better understand those of the past. The bulk of this body of research falls under the category of actualistic paleontology, and examines geochronological methods and error biases in dating biological specimens ranging in age from modern to thousands of years old. Although such methods are arguably not perfect, error rates of ± a few hundred to few thousand years can be extremely important when considering ecological relationships among both Holocene taxa and time-averaged paleocommunities, but quite diminished when considering implications on more traditional dating techniques for ancient strata. Regardless, understanding implications of time resolution is important in analyses of and comparisons between any biological dataset. The following chapters are united by quantitative and statistical management of data with varying levels of temporal resolution, and represent four manuscripts that either are in press or soon to be submitted for publication.Ph. D.
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Piva, Andrea <1978>. "High-resolution stratigraphy of Central and Southern Adriatic Quaternary deposits of sub-Milankovian climate change on Mediterranean circulation." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/456/.
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This volume is a collection of the work done in a three years-lasting PhD, focused in the analysis of Central and Southern Adriatic marine sediments, deriving from the collection of a borehole and many cores, achieved thanks to the good seismic-stratigraphic knowledge of the study area.
The work was made out within European projects EC-EURODELTA (coordinated by Fabio Trincardi, ISMAR-CNR), EC-EUROSTRATAFORM (coordinated by Phil P. E. Weaver, NOC, UK), and PROMESS1 (coordinated by Serge Bernè, IFREMER, France). The analysed sedimentary successions presented highly expanded stratigraphic intervals, particularly for the last 400 kyr, 60 kyr and 6 kyr BP. These three different time-intervals resulted in a tri-partition of the PhD thesis. The study consisted of the analysis of planktic and benthic foraminifers’ assemblages (more than 560 samples analysed), as well as in preparing the material for oxygen and carbon stable isotope analyses, and interpreting and discussing the obtained dataset. The chronologic framework of the last 400 kyr was achieved for borehole PRAD1-2 (within the work-package WP6 of PROMESS1 project), collected in 186.5 m water depth. The proposed chronology derives from a multi-disciplinary approach, consisting of the integration of numerous and independent proxies, some of which analysed by other specialists within the project. The final
framework based on: micropaleontology (calcareous nannofossils and foraminifers’ bioevents), climatic cyclicity (foraminifers’ assemblages), geochemistry (oxygen stable isotope, made out on planktic and benthic records), paleomagnetism, radiometric ages (14C AMS), teprhochronology, identification of sapropel-equivalent levels (Se). It’s worth to note the good consistency between
the oxygen stable isotope curve obtained for borehole PRAD1-2 and other deeper Mediterranean records. The studied proxies allowed the recognition of all the isotopic intervals from MIS10 to MIS1 in PRAD1-2 record, and the base of the borehole has been ascribed to the early MIS11.
Glacial and interglacial intervals identified in the Central Adriatic record have been analysed in detail for the paleo-environmental reconstruction, as well. For instance, glacial stages MIS6, MIS8 and MIS10 present peculiar foraminifers’ assemblages, composed by benthic species typical of polar regions and no longer living in the Central Adriatic nowadays. Moreover, a deepening trend in the paleo-bathymetry during glacial intervals was observed, from MIS10 (inner-shelf environment) to MIS4 (mid-shelf environment).Ten sapropel-equivalent levels have been recognised in PRAD1-2 Central Adriatic record. They showed different planktic foraminifers’ assemblages, which allowed the first distinction of events occurred during warm-climate (Se5, Se7), cold-climate (Se4, Se6 and Se8) and temperate-intermediate-climate (Se1, Se3, Se9, Se’, Se10) conditions, consistently with literature. Cold-climate
sapropel equivalents are characterised by the absence of an oligotrophic phase, whereas warm-temeprate-climate sapropel equivalents present both the oligotrophic and the eutrophic
phases (except for Se1). Sea floor conditions vary, according to benthic foraminifers’ assemblages, from relatively well oxygenated (Se1, Se3), to dysoxic (Se9, Se’, Se10), to highly dysoxic (Se4, Se6, Se8) to events during which benthic foraminifers are absent (Se5, Se7). These two latter levels are also characterised by the lamination of the sediment, feature never observed in literature in such
shallow records. The enhanced stratification of the water column during the events Se8, Se7, Se6, Se5, Se4, and the concurring strong dilution of shallow water, pointed out by the isotope record, lead to the hypothesis of a period of intense precipitation in the Central Adriatic region, possibly due to a northward shift of the African Monsoon. Finally, the expression of Central Adriatic PRAD1-2 Se5 equivalent was compared with the same event, as registered in other Eastern Mediterranean areas. The sequence of substantially the same planktic foraminifers’ bioevents has
been consistently recognised, indicating a similar evolution of the water column all over the Eastern Mediterranean; yet, the synchronism of these events cannot be demonstrated. A high resolution analysis of late Holocene (last 6000 years BP) climate change was carried out for the Adriatic area, through the recognition of planktic and benthic foraminifers’ bioevents. In particular, peaks of planktic Globigerinoides sacculifer (four during the last 5500 years BP in the most expanded core) have been interpreted, based on the ecological requirements of this species, as warm-climate, arid intervals, correspondent to periods of relative climatic optimum, such as, for instance, the Medieval Warm Period, the Roman Age, the Late Bronze Age and the Copper Age. Consequently, the minima in the abundance of this biomarker could correspond to relatively cooler and more rainy periods. These conclusions are in good agreement with the isotopic and the pollen data. The Last Occurrence (LO) of G. sacculifer has been dated in this work at an average age of 550 years BP, and it is the best bioevent approximating the base of the Little Ice Age in the Adriatic. Recent literature reports the same bioevent in the Levantine Basin, showing a rather consistent age. Therefore, the LO of G. sacculifer has the potential to be extended to all the Eastern Mediterranean. Within the Little Ice Age, benthic foraminifer V. complanata shows two distinct peaks in the shallower Adriatic cores analysed, collected hundred kilometres apart, inside the mud belt environment. Based on the ecological requirements of this species, these two peaks
have been interpreted as the more intense (cold and rainy) oscillations inside the LIA. The chronologic framework of the analysed cores is robust, being based on several range-finding 14C AMS ages, on estimates of the secular variation of the magnetic field, on geochemical estimates
of the activity depth of 210Pb short-lived radionuclide (for the core-top ages), and is in good agreement with tephrochronologic, pollen and foraminiferal data. The intra-holocenic climate oscillations find out in the Adriatic have been compared with those pointed out in literature from other records of the Northern Hemisphere, and the chronologic constraint seems quite good. Finally, the sedimentary successions analysed allowed the review and the update of the foraminifers’ ecobiostratigraphy available from literature for the Adriatic region, thanks to the
achievement of 16 ecobiozones for the last 60 kyr BP. Some bioevents are restricted to the Central Adriatic (for instance the LO of benthic Hyalinea balthica , approximating the MIS3/MIS2 boundary), others occur all over the Adriatic basin (for instance the LO of planktic Globorotalia inflata during MIS3, individuating Dansgaard-Oeschger cycle 8 (Denekamp)).
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Clemente, Iara Martins Matos Moreira. "Ecologia e paleoecologia de foraminíferos do holoceno na Baia de Guanabara, RJ." Universidade do Estado do Rio de Janeiro, 2011. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=9289.
Full textAbstract:
Este estudo teve como objetivo contribuir com as informações ecológicas e paleoecológicas geradas para a Baía de Guanabara com base na distribuição das assembléias de foraminíferos bentônicos. Para tal foram coletadas 30 amostras de sedimento superficial, ao longo de três perfis distribuídos pela baía e um testemunho (BG28) de 6 m de comprimento retirado próximo a Ilha do Governador. Nas amostras superficiais foram identificados 30 gêneros e 52 espécies das quais as espécies mais constantes foram Amonia tepida e Bolivina translucens que apresentaram a maior constância. Espécies de habitat de plataforma foram identificadas em diversas estações indicando uma boa eficiência no transporte das correntes de fundo para dentro da baía. Das estações superficiais analisadas, 10 localizadas ao redor da Ilha do Governador não continham testas de foraminíferos, possivelmente como resultado da acidificação do sedimento causado pelo derrame de óleo ocorrido em 2000. O índice de confinamento associado às análises de agrupamento e ao DCA indicaram a presença de três setores ambientais influenciadas por COT e granulometria. O primeiro setor entre Copacabana-Itatipú e Aeroporto Santos Dumont Ilha de Boa Viagem foi o ambiente marinho, o segundo setor entre o Aeroporto Santos Dumont - Ilha de Boa Viagem e Ilha do Governador Ilha de Paquetá Litoral de São Gonçalo pode se classificado como um ambiente de estuário inferior ou baía com grande influência marinha e o terceiro setor entre a Ilha do Governador Ilha de Paquetá Litoral de São Gonçalo e fundo da baía como o ambiente mais confinado. No testemunho foram feitas 7 datações indicando uma idade de aproximadamente 5180 40 anos BP. As datações também mostraram que nos últimos anos a taxa de sedimentação aumentou muito podendo estar relacionada com o período de colonização européia. Foram encontradas 18 gêneros e 30 espécies de foraminíferos das quais a espécie mais constante foi a Ammonia tepida seguida pela Buliminella elegantissima. O padrão de distribuição dessas espécies ocorreu com a maior abundância de B. elegantissima nas porções mais inferiores do testemunho e uma abundância maior de A. tepida nas porções mais superiores. Os índices de confinamento junto com as análises de agrupamento e com as curvas de isótopos mostraram que houve poucas oscilações no aporte de água marinha naquela região. As análises dos isótopos de C13 e C14 e O16 e O18 não seguiram um padrão inverso comum em outros estudos, possivelmente influenciado pela proximidade da costa. As análises de agrupamentos indicaram que nos últimos 5180 anos BP a baía não sofreu grandes variações ambientais, ou seja, a região oeste da baía mesmo apresentando alterações ao longo dos anos não foi suficiente para modificar as características de confinamento. As análises nos padrões de distribuição das assembléias de foraminíferos demonstraram ser eficientes ferramentas na caracterização ambiental e paleoambiental da Baía de Guanabara.This study aimed to contribute with ecological and paleoecological informations generated in the Guanabara Bay based on the distribution of benthic foraminifera assemblages. In this study were collected 30 samples of surface sediments along three transect distributed in the bay and one core of 6 m length extracted near to Ilha do Governador. In the surface samples were identified 30 genera and 52 species which the most constant species were Ammonia tepida e Bolivina translucens exhibit the major constancy. Marine species were identified in several stations indicating good efficiency of tidal landward transport. In the surface stations analyzed, 10 located around Ilha do Governador doesn`t contain foraminifera tests, perhaps as a result of sediment acidification caused by oil spill occurred at year 2000. The confinement index associated to cluster analysis and DCA indicated the presence of three influenced environmental sectors by COT and grain size. The first section between Copacabana Itaipú and Santos Dumont airport Ilha de Boa Viagem was the marine environment, the second section between Santos Dumont airport Ilha de Boa Viagem and Ilha do Governador Ilha de Paquetá São Gonçalo coast can be classified like a inferior estuarine environment or bay with great marine influence and a third section between Ilha do Governador Ilha de Paquetá São Gonçalo coast and the inner of the bay as the most confined environment. In the core were done 7 dating indicating an age approximately 518040 years BP. The dating also reveal that in the last years the sedimentation rate increase and could be related with the European colonization period. Were found 18 genera and 30 species of foraminifera which the most constant specie was Ammonia tepida followed by Buliminella elegantissima. The distribution pattern of this species occurred with higher abundance of B. elegantissima in most inferior portions from the core and major abundance of A. tepida in most superior portions. The confinement index combined with cluster analysis and isotopes curves showed that was a few oscillations in the input of marine water in that region. Isotope analysis of C13/C14 and O16/O18 doens`t followed usual inverse pattern in other studies, possibly influenced by the proximity with the coast. The cluster analysis indicated that in the last 5180 years BP the bay didn`t suffer large environmental variations, that means the west region of the bay even presenting modification through the years it was not sufficient to modify the characteristics of the confinement. Analysis in the distribution pattern of foraminiferal assemblages demonstrated to be efficient tools to the environmental and paleoenvironmental characterization of Guanabara Bay.
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Alin, Simone Rebecca. "Calibration and Interpretation of Holocene Paleoecological Records of Diversity from Lake Tanganyika, East Africa." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/231412.
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Lake Tanganyika is a complex, tropical ecosystem in East Africa, harboring an estimated 2,100 species. Extensive watershed deforestation threatens the biodiversity and ecological integrity of the lake. In this dissertation, ecological and paleoecological methods were employed to study the distribution of invertebrate biodiversity through space and time, with particular emphasis on linkages between biodiversity and land –use patterns. Ecological surveys of fish, mollusc, and ostracod crustacean diversity at sites in northern Lake Tanganyika representing different levels of watershed disturbance revealed a negative correlation between biodiversity and intensity of watershed disturbance. To elucidate the long -term relationship between disturbance and biodiversity, paleoecological records of invertebrates offshore from watersheds experiencing different degrees of anthropogenic disturbance were examined. Life, death, and fossil assemblages of ostracod valves were compared to assess the reliability and natural variability inherent to the paleoecological record. These comparisons indicated that paleoecological (i.e. death and fossil) assemblages reliably preserve information on species richness, abundance, and occurrence frequency at comparable -to- annual resolution. Unlike life assemblages, species composition of paleoecological assemblages reflects input of species from multiple habitat types. Ostracod paleoecological assemblages are characterized by spatiotemporal averaging that renders them representative of larger areas and longer time spans than life assemblages. Thus, paleoecological assemblages provide an efficient means of characterizing longer -term, site -average conditions. Natural variability in ostracod fossil assemblages from a sediment core representing the Late Glacial to the present indicates that abundance of individual ostracod species is highly variable. Ostracod assemblages were preserved in only the most recent 2,500 years of sediment. Species composition of ostracod assemblages reflects lake water depth. Core geochemical data indicate that the coring site may have been below the oxycline for ~2,000 years, inhibiting ostracod survival and preservation. Paleoecological, sedimentological, and stable isotope data revealed differences in biodiversity and watershed disturbance through time offshore from a pair of sites. The protected site is offshore from Gombe Stream National Park (Tanzania), the other offshore from a deforested watershed outside the park. Offshore from the deforested watershed, sedimentation rates increased, and turnover in ostracod species composition occurred during the past 50 years. Comparable changes were not observed offshore from the park.
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Petrocchi, Francesca. "Paleo- ecologia dei Foraminiferi in ambiente estremo: un caso di studio in Antartide." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/9763/.
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Nel presente lavoro sono state analizzate le distribuzioni quantitative dei Foraminiferi planctonici e bentonici presenti in una carota e in un box core prelevati nel Mare di Ross in Antartide durante la campagna KOPRI ANTA03 nel Febbraio 2013 nell’ambito del progetto di ricerca congiunto Corea- Italia finanziato dal Progetto Nazionale di Ricerca in Antartide (PNRA). Scopo del lavoro è stato quello di comprendere l’evoluzione ambientale dell’area in base alla distribuzione quantitativa e qualitativa delle associazioni a Foraminiferi nel tardo Quaternario. In base alla distribuzione quantitativa dei Foraminiferi identificati, la sequenza sedimentaria della carota C2 è stata suddivisa in tre intervalli corrispondenti a tre principali fasi paleoceanografiche/paleoclimatiche. La prima fase, più antica di 18 ka, caratterizzata dall’assenza o rarità di forme documenta un ambiente con presenza di copertura glaciale. La seconda, depositatasi tra 18 ka e ~8 ka è caratterizzata da una maggiore variabilità intraspecifica e riflette un miglioramento delle condizioni climatiche. La terza, corrisponde ad un periodo compreso tra ~8 ka e ~2 ka. La presenza di forme agglutinanti e l’assenza di Foraminiferi a guscio calcareo suggeriscono la presenza di condizioni di dissoluzione carbonatica sul fondale in un ambiente marino libero da copertura glaciale. La documentazione di numerosi individui allo stadio giovanile di Neogloboquadrina pachyderma durante l’intervallo B ha reso possibile avanzare ipotesi riguardo la strategia di sopravvivenza di questa specie in ambiente estremo quale il ghiaccio antartico. La somiglianza morfologica tra individui giovanili di Neogloboquadrina pachyderma riscontrata durante il nostro studio nei sedimenti a livello fossile nella carota con individui giovanili della stessa specie provenienti da campioni di ghiaccio marino antartico documentati in bibliografia, ha permesso di supportare la tesi dello sviluppo di tali forme nei pori del “microghiaccio”.
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Schwartz, James P. "Late quaternary periplatform sediments and paleoenvironmental analysis of Pedro Channel, northeastern Nicaragua rise, Caribbean Sea." Thesis, 1996. http://hdl.handle.net/1911/14080.
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Using four periplatform sediment cores of intermediate water depth (900 to 1400 m) from the western Caribbean Sea, an investigation was conducted to ascertain the difference in cyclicity between the late-Brunhes Mode and the mid-Brunhes Mode. The past 185 ky define the late-Brunhes Mode, which records extreme changes between glacial and interglacial conditions, and consistent behavior within isotopic stages. Defined as 525 to 185 ky for the purposes of this study, the mid-Brunhes Mode represents a time of mild changes between and within glacial and interglacial stages, much like an extended late-Brunhes interglacial stage. Changes between the two modes were monitored using proxies for dissolution, AAIW influx (influence of the Southern Ocean on intermediate Caribbean waters), nutrients, migration of the North Atlantic Gyre, sea level and strength of the Caribbean Current.
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George, Christian Owens. "Alternative approaches to the identification and reconstruction of paleoecology of Quaternary mammals." 2012. http://hdl.handle.net/2152/19580.
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Since the 19th century the remains of Quaternary mammals were an important source of data for reconstructing past environmental conditions. I tested two basic assumptions that underlie Quaternary vertebrate paleoecology. The first assumption is that fossils mammals can be identified reliably to species. The second assumption is that correlations established between extant mammals and environmental parameters can be used to interpret reliably the paleoenvironment from the latest Pleistocene.
Incorrect specimen identifications could lead to errors in paleoecologic interpretations. I explicitly tested an alternative to the traditional approach to identification by identifying fossil shrews based on apomorphies. My results indicated that some traditional characters are useful for identification, but only complete specimens with a combination of characters can be identified to species. This indicates that previous authors who identified shrews to species did not compare them to the full diversity of species.
I tested the reliability of cenograms and species-richness models as approaches for the reconstruction of environmental conditions in the past. I used faunal data from Hall’s Cave, Kerr County, Texas to construct cenograms and species-richness models and compared the results to independent paleoclimate proxies. Neither species-richness models nor cenograms agree with paleoenvironmental reconstructions based on proxy data from the Late Pleistocene and Holocene. Cenograms and species-richness models are unreliable and fraught with problems, and both approaches should be abandoned as tools for paleoecological reconstruction.
To test for potential geographic bias in the identification of Quaternary fossils I developed a GIS (geographic information systems) database of Quaternary paleontological sites within Texas. I was able to show that the identification of species of fossil soricids, heteromyids, Odocoileus, and Spilogale was influenced by geography. Those fossils should be treated as generic identifications until they are re-evaluated against the full diversity of species. Utilizing GIS I also developed a method of paleoecological analysis. My analysis showed that the environmental conditions found today in Texas might not be limiting the current range of shrews. Based on the known geographic range of shrew fossils, other ecological factors besides environmental conditions are shaping the current distribution of shrews.text
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Haddad, Geoffrey Allen. "Calcium carbonate dissolution patterns at intermediate water depths of the tropical oceans during the Quaternary." Thesis, 1994. http://hdl.handle.net/1911/16729.
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This study presents mineralogic and stable isotopic records generated for piston cores and Ocean Drilling Program holes recovered from intermediate water depths (500 to 2500 meters) near carbonate platforms around the world. Study areas included the Bahamas (western North Atlantic Ocean), the Nicaragua Rise (Caribbean Sea), the Maldives (north equatorial Indian Ocean), and the Queensland Plateau (southwest Pacific Ocean). Mineralogic data includes percent fine aragonite content, percent fine Mg calcite content, pteropod (aragonitic holoplanktonic gastropods) abundance, percent whole pteropods, and for some cores, percent clear pteropods. Carbonate data were interpreted both in terms of carbonate input from the nearby banks and in terms of seafloor dissolution. Planktic foraminiferal $\delta\sp{18}$O records were used as the primary chronostratigraphic tool for all sites.
Statistical analyses of four metastable CaCO$\sb3$ dissolution proxies yielded a composite dissolution index (CDI) that displays different dissolution histories for Bahama and Nicaragua Rise sediments over the last 200,000 years. These differences are not predicted by intermediate to deep water nutrient fractionation models (e.g., Boyle, 1988). A good correlation is observed between the Caribbean CDI record (this study) and CaCO$\sb3$ dissolution and benthic $\delta\sp{13}$C records from 4641 meters in the Venezuela Basin, Caribbean Sea (Cofer-Shabica, 1987). It is concluded that during the last 200,000 years, variable cross-equatorial flux of Antarctic Intermediate Water has strongly influenced Caribbean carbon chemistry at water depths greater than 1100 meters. The assumption, therefore, that deep Caribbean sediment cores reliably record nutrient and (CO$\sb3\sp{=}$) variations of average mid-depth Atlantic water may need re-evaluation.
Over longer time scales, CaCO$\sb3$ dissolution records from intermediate water depths near the Bahamas, Maldives, and Queensland Plateau are similar to deep-water dissolution records. Dissolution occurred from thermocline to abyssal depths from 500,000 to 300,000 years ago (during the middle Brunhes Chron) and between 1,000,000 and 900,000 years ago revealing that whole-ocean changes in carbonate chemistry have occurred during the Quaternary. Enhanced CaCO$\sb3$ dissolution may be related to decreased Ca$\sp{2+}$ flux to the ocean (decreased glacial weathering) and increased neritic CaCO$\sb3$ production and accumulation during periods of elevated interglacial sea-level highstands.
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SINGER, JILL KAREN. "TERRIGENOUS, BIOGENIC, AND VOLCANOCLASTIC SEDIMENTATION PATTERNS OF THE BRANSFIELD STRAIT AND BAYS OF THE NORTHERN ANTARCTIC PENINSULA: IMPLICATIONS FOR QUATERNARY GLACIAL HISTORY." Thesis, 1987. http://hdl.handle.net/1911/16106.
Full textAbstract:
A marine sedimentologic investigation was conducted on the northern Antarctic Peninsula continental margin. The data base included piston cores, surficial sediments, and high resolution seismic reflection profiles. The objectives of this study were three-fold: examine sedimentation patterns in the Bransfield Basin, a high-latitude, actively spreading back-arc basin; relate sedimentation processes to lithofacies patterns in bays and fjords of the South Shetland Islands, Palmer Archipelago, and Danco Coast; and interpret the recent glacial-climatic history of this region.
As a back-arc basin in a polar latitude, the Bransfield Basin represents a unique sedimentary environment. Fluvial discharge systems are lacking and the Bransfield Basin receives only minor amounts of continentally-derived sediment. The South Shetland arc is inactive, and the locus of recent volcanic activity is the axis of back-arc spreading. The sediments accumulating in the Bransfield Basin represent the input of terrigenous, biogenic, and volcaniclastic phases. Sediment distribution reflects the interplay of marine currents, primary production, and volcanic activity.
At water depths $<$250 m, marine currents actively redistribute sediment, and residual deposits blanket the shelf between the northern tip of the Antarctic Peninsula and Tower Island. A transition from residual deposits to deposits with increased mud content west of Tower Island indicates a decrease in the intensity of marine currents as they flow east to west along the shelf. Lower energy conditions characterize the Bransfield Basin, permitting the suspension settling of fine terrigenous and biogenic phases. These predominantly fine-grained deposits record episodic pulses of increased volcaniclastic input. The normally graded volcanic ash layers represent both air fall deposits and sediment gravity flow deposits (turbidites).
The distribution and composition of lithofacies recovered in bays and fjords appear to be regulated by the proximity to ice margins and to discharging meltwater systems. Where terrigenous sediment input is less pronounced, a biogenic lithofacies is present. Seismic records show that the thickness of the meltwater facies increases from south to north in the study area. It appears that initiation of meltwater production occurred relatively recently in bays of the Danco Coast. In contrast, sedimentation in bays of the Palmer Archipelago and South Shetland Islands is meltwater-dominated, and terrigenous sediments are rapidly accumulating. (Abstract shortened with permission of author.)
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Marianelli, Pyramo C. "Palaeoenvironmental proxies from Southern Australian speleothems." Phd thesis, 2000. http://hdl.handle.net/1885/149912.
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Haberle, Simon. "Late quaternary environmental history of the Tari Basin, Papua New Guinea." Phd thesis, 1993. http://hdl.handle.net/1885/140965.
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Hellstrom, John Charles. "Late quaternary palaeoenvironmental records from the geochemistry of speleothems, North-West Nelson, New Zealand." Phd thesis, 1998. http://hdl.handle.net/1885/144671.
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De, Deckker P. (Patrick). "Australian Quaternary studies : a compilation of papers and documents submitted for the degree of Doctor of Science in the Faculty of Science, University of Adelaide." 2002. http://web4.library.adelaide.edu.au/theses/09SD/09sdd299.pdf.
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"April 2002" Includes bibliographical references and list of the publications and papers submitted. Pt. 1: section 1. Ostracod taxonomy and ecology -- section 2. Limnology of salt lakes -- section 3. Ostracod palaoecology - Quaternary environments -- section 4. Palaolimnology - Quaternary paleoenvironments and geology -- pt. 2: section 5. Geochemistry of ostracod shells -- section 6. Palaeoceanography Contains the majority of the author's scientific publications. Aims at reconstructing Quaternary paleoenvironments, mostly from the Australian region, using the fossil remains of organisms as well as new geochemical techniques.
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Hickin, Adrian Scott. "Late Quaternary to Holocene Geology, Geomorphology and Glacial History of Dawson Creek and Surrounding area, Northeast British Columbia, Canada." Thesis, 2013. http://hdl.handle.net/1828/5100.
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Northeastern British Columbia was occupied by the Cordilleran (CIS) and the Laurentide (LIS) ice sheets, however, the timing and extent remains contentious. The late Quaternary and Holocene history of this area is examined by exploring geomorphic, stratigraphic, geochemical and geochronologic components of glacial, deglacial, paraglacial and non-glacial landsystems. New tools, such as GIS, LiDAR, and new geochronologic methods, such as optical dating are used to understand the Quaternary geology and geomorphology of the region.
Bedrock topography represents the base of the Quaternary section and modelling shows that paleovalleys, common in this region, host extensive Neogene sedimentary records. Stratigraphies from the Murray and Pine valleys indicate glaciation prior to the Mid-Wisconsinan (MIS 3) and during the Late Wiconsinan (MIS 2). Glacial landforms record Late Wisconsinan ice-sheet coalescence and reflect the complex interaction of the LIS and CIS margins.
During deglaciation, the LIS and CIS separated and glacial Lake Peace (GLP) formed. Shoreline features enable reconstruction of lake and ice configurations. Four phases of GLP are preserved. Optical ages from Phase II indicate GLP occupied the area some time between ca. 16 – 14 ka yrs ago. The apparent tilt on the shorelines provides a measure of isostatic adjustments and suggests asynchronous retreat of first the LIS, then the CIS.
The transition from paraglacial to boreal conditions was driven by climate change and is recorded by vegetation sucession and cessation of paraglacial processes. Optical ages from stabilized dunes and radiocarbon ages from organics date the transition between 12 – 11.5 ka yrs ago with full boreal conditions established by 10 ka yrs ago.
The Holocene is dominated by erosional processes, however some systems are aggrading. A case study on a floodplain demonstrates that resistivity (Ohmmapper) surveys provide a grain-size proxy to suppliant GPR studies, which is essential for geophysical fluvial architectural analysis. In the study, the discrepancy between planform style (classic meander model) and subsurface geophysical surveys (indicative of vertical accretion associated with braided and wandering fluvial styles) reiterates cautions that planform may not always be a functions of depositional process and one may not be used to predict the other.Graduate
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Vollbrecht, Rüdiger Dr. "Postglazialer Anstieg des Meeresspiegels, Paläoklima und Hydrographie, aufgezeichnet in Sedimenten der Bermuda inshore waters." 1997. http://hdl.handle.net/11858/00-1735-0000-0006-B35B-4.
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