Esta dissertação apresenta o resultado de um levantamento de sítios líticos caçadores-coletores no alto rio das Almas nos contrafortes ocidentais da Serra de Paranapiacaba. Dados sobre as indústrias líticas relacionadas são fornecidos sucintamente e comparadas às pesquisas desenvolvidas no Médio Ribeira por De Blasis (1988). Em acréscimo, esta Dissertação trata de estabelecer parâmetros para a compreensão da formação de sítios arqueológicos detectados em profundidade em porções de alta vertente, datados do Holoceno Médio. A continuidade de grupos caçadores-coletores na área de pesquisa é delimitada entre 5920 e 1000 anos AP e, em face a este período, tratamos de reconstruir os cenários sob transformação ambiental regional em a que estiveram submetidos esses grupos humanos e seus assentamentos. Nossa contribuição é desvincular os estudos sobre grupos caçadores-coletores do cunho hiper-determinista da tecno-tipologia lítica para uma discussão mais ampla que dialogue de forma transdisciplinar com a geomorfologia, a palinologia e a espeleologia. / This thesis provides the results of an archaeological survey focused in hunter-gatherer settlements from Upper Almas valley, on the western side of Paranapiacaba Mountains. Dates from lithics analysis associated to these sites are compared with results from Middle Ribeira valley, developed by De Blasis (1988). In addition, this Thesis treats to establish frames of reference to understand the formation processes of archaeological sites settled during the Middle Holocene in high depth on high portions of the mountains. The hunter-gatherer continuity between 5920 and 1000 yr BP in the studied area is approached by a paleoambiental treatment: our additional goal is to reconstruct the scenarios of environmental transformations in which these human groups developed their History. Furthermore, this thesis provides an instance to reduce the technological approach over these groups, opening an ecosystem approach which includes dates from palinology, geomorphology and espeleology.

This doctoral thesis presents the results of the pioneering archaeological investigation conducted in the Northern Mexican Highlands with the aim to evaluate the existing indicators of the earliest human occupations at the end of the Pleistocene and discover new evidence of ancient cultural manifestations through a systematic exploration of an endorheic basic in the Zacatecas desert, a region never studied before. An exhaustive survey and analysis of the available literature on Mexican prehistory establishes the weak points of the local paradigms, differentiating between academic myths and objective realities. A complete historiography of the topic of the earliest humans in Mexico has been achieved, for the first time. The study of several collections of flaked stone artefacts, in different cities in Mexico, show new indicators of the presence of bearers of the Late Paleoamerican cultures, in regions where their presence had been weakly confirmed. The most important part of the research consisted in fieldwork realised during two long seasons; the first one dedicated to the surface explorations and the second one to excavations. Thirty-five new archaeological sites were discovered in the first phase, most of them open campsites reminiscent of hunter-gatherer societies, with a richness of stone artefacts on their surface. They indicate a long cultural sequence, going from the Late Pleistocene to the Late Holocene and the historic periods. Four sites were further studied by fourteen test excavation units: Dunas de Milpa Grande, San José de las Grutas, the Chiquihuite Cave and Ojo de Agua. Two new archaeological cultures were identified, one at Dunas (an interesting assemblage of limestone and basalt flaked stone tools) and another one at San José (a limestone concave-based points complex). First indicators of ʻolder than Clovisʼ human presence have also been obtained. The palaeoenvironmental data provide a preliminary reconstruction of the Late Pleistocene-Early Holocene landscape of the basin, based on geology, extinct fauna, phytolith and mollusc analyses. Radiocarbon and OSL results support a first cultural and paleoclimatic model for the study area. This investigation also discovered the first case of a “black mat” in Mexico: a black layer of sediment deposited under specific environmental conditions during the Younger Dryas cooling event.

The objective of this research is to interpret high-resolution palaeo-proxy data sets to understand the Asian summer monsoon variability in the past. This was done by synthesizing published palaeo-records from the Asian monsoon region, model simulation comparisons, and analysing new lake sedimentary records from northeast Thailand. Palaeo-records and climate modeling indicate a strengthened summer monsoon over Mainland Southeast Asia during the Last Glacial Maximum (LGM), compared to dry conditions in other parts of the Asian monsoon region. This can be explained by the LGM sea level low stand, which exposed Sundaland and created a large land-sea thermal contrast. Sea level rise ~19 600 years before present (BP), reorganized the atmospheric circulation in the Pacific Ocean and weakened the summer monsoon between 20 000 and 19 000 years BP. Both the Mainland Southeast Asia and the East Asian monsoon hydroclimatic records point to an earlier Holocene onset of strengthened summer monsoon, compared to the Indian Ocean monsoon. The asynchronous evolution of the summer monsoon and a time lag of 1500 years between the East Asian and the Indian Ocean monsoon can be explained by the palaeogeography of Mainland Southeast Asia, which acted as a land bridge for the movement of the Intertropical Convergence Zone. The palaeo-proxy records from Lake Kumphawapi compare well to the other data sets and suggest a strengthened summer monsoon between 10 000 and 7000 years BP and a weakening of the summer monsoon thereafter. The data from Lake Pa Kho provides a picture of summer monsoon variability over 2000 years. A strengthened summer monsoon prevailed between BC 170-AD 370, AD 800-960 and since AD 1450, and was weaker about AD 370-800 and AD 1300-1450. The movement of the mean position of the Intertropical Convergence Zone explains shifts in summer monsoon intensity, but weakening of the summer monsoon between 960 and 1450 AD could be affected by changes in the Walker circulation. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript..</p>

published_or_final_version / abstract / Earth Sciences / Master / Master of Philosophy

<p>The main aim of this thesis was to contribute with detailed information of regional environmental change during the Holocene through studies of speleothems and their growth environments from two caves, Korallgrottan and Labyrintgrottan in northwestern Sweden, and a cellar vault in Uppsala. This was done through studies of stable isotopes and luminescence properties in the speleothems in combination with a detailed monitoring study in Korallgrottan.</p><p>The monitoring study suggests that stalagmites fed by stalactites with slow and stable drip rates from deep inside the cave may be suitable as palaeoclimate archives. Similarities between oxygen isotope signals of contemporary samples from Labyrintgrottan and Korallgrottan emphasize the potential of speleothems from Labyrintgrottan to also provide high resolution regional palaeoclimate information.</p><p>Except for a number of cold events stalagmite δ¹⁸O records from northern Scandinavia indicate that temperatures were warmer than today between 9500 and 6000 years ago. During this period the interval between 7800 and 6000 years ago seems to have been the warmest. The area above Labyrintgrottan was most likely covered by much denser vegetation than today at the time of stalagmite growth (9500-7500 years ago) and was, unlike today, probably situated below the local tree-limit between 9000 and 8000 years ago. The δ¹⁸O record of a stalagmite from Korallgrottan covering the last 4000 years agrees with the concept of a warmer period, the so called Medieval Warm Period, centred around AD1000 and a colder period, the so called Little Ice Age, somewhere between AD1000 and today.</p><p>Studies of luminescence properties in fast growing speleothems from Uppsala indicate that the variations in luminescence intensity are annual and that the annual lamiae of the luminescent record represent a flush of organic material.</p>

This thesis resulted in the development of robust chironomid-based transfer-functions for February mean air temperature and the concentration of total nitrogen (TN) in lake-water. The New Zealand transfer-functions for both variables compare favourably with chironomid-based transfer-functions for equivalent variables from elsewhere in the world, and diatom-based transfer-functions for nutrients and lake production from New Zealand. The application of the temperature and TN transfer-functions provided insight into New Zealand climate conditions during the last glacial and served as validation for the reconstructions. Chironomid-based Temperature reconstructions from lake silts preserved in the banks of Lyndon Stream indicate a maximum cooling of ca 4 ℃ between 26.6 and 24.5 ka BP, which is consistent with estimates based on beetles and plant macrofossils. A cooling of 4 ℃ is insufficient to explain the lack of canopy tree pollen in many New Zealand pollen records at this time. Other environmental parameters additional to temperature may have limited the expansion forest cover. The chironomid-based TN reconstructions infer a trend of rapidly deteriorating water-quality in a small doline in north-west Nelson, in the South Island of New Zealand following deforestation immediately surrounding the lake ca. 1970 AD. The overall trend and timing of eutrophication inferred from the chironomids was consistent with other biological proxies and actual observations of changes in lake water quality. The chironomid-based transfer-functions provide a valuable new tool for the study of longterm climate variability and improving our understanding of the response of aquatic ecosystems to long-term natural and human induced environmental change in New Zealand lakes. I have identified some possibilities for future research which should improve the performance of these transfer-functions. The improvement of the chironomid taxonomy and the expansion of the training set should be the highest priorities.

The southwest monsoon is responsible for a summer precipitation maximum for much of the southwest U.S. Biostratigraphies of pollen, plant macrofossils, and aquatic fossils in lakes from near modern monsoon boundaries in conjunction with climate modelling suggests variations in strength of the monsoon system during the late Quaternary. At Montezuma Well, Arizona, high percentages of Pinus and Juniperus pollen as well as maximum influxes of Quercus and Gramineae pollen suggest a shift from dominantly winter to summer precipitation between ca. 12,000 and 9000 yr BP. Maximum aridity occurred 7000-4000 yr BP, coincident with lowest lake levels. In the High Plateaus region of the Colorado Plateau, high Artemisia to Chenopodiaceae-Amaranthus pollen ratios suggests precipitation maxima until ca. 6000 yr BP at Fryingpan Lake and 5000 yr BP at Posy Lake. Pollen records suggest that Pinus edulis, P. ponderosa, and Quercus gambelii, were present on the western Colorado Plateau throughout the Holocene. Expansion of shadscale steppe vegetation at low elevations and upslope movement of ecotones for Pinus edulis, P. ponderosa, and Q. gambelii after ca. 6000 yr BP and low lake levels ca. 5000-3700 yr BP, suggest a period of maximum aridity from decreased summer precipitation. In the San Luis Valley, Colorado, pollen records from Head Lake on the basin floor suggest an expansion of oaks and junipers at the Pleistocene/Holocene boundary that may indicate increased summer precipitation. Lake levels of Head Lake fell sharply after ca. 9500 yr BP. Pollen records from Como Lake in the Sangre de Cristo Mountains suggest that Pinus ponderosa was established in the area by ca. 12,000 yr BP and Pinus edulis by ca. 9500 yr BP. Highland regions such as the High Plateaus (until ca. 6000-5000 yr BP) and central Colorado (until ca. 4000 yr BP) may have experienced Holocene summer precipitation maxima later into the Holocene than sites in lower elevation regions. Regional orographic uplift as a catalyst for convective summer precipitation may be responsible for the duration of summer precipitation maxima in these regions. On a longitudinal gradient, sites to the west such as in the southern Great Basin and Mohave Desert may have recorded enhanced summer precipitation earlier, reflecting different histories of the low-level jets in the southwest. The paleoecologic record generally confirm predictions of general circulation models (GCMs) that southwest monsoon circulation was enhanced from 12,000-6000 yr BP in response to peaks in annual (11,500-11,000 yr BP) and summer insolation (10,000-9000 yr BP) during the late Quaternary.

This study reconstructs vegetation and climate encompassing pre-full glacial and Holocene time for the Mogollon Rim region of Arizona. Implications for the southwestern United States are discussed. Pine species (some currently disjunct) or species groups are identified. Two lakes were cored, the sediments were analyzed for pollen content, and dates were obtained by radiocarbon analysis. Hay Lake (2780 m) is surrounded by mixed conifer forest in the White Mountains, Arizona (34°N and 109°30'W). Jacob Lake (2285 m, 34°25' N and 110°50' W) is surrounded by ponderosa pine forest. Extrapolated dates for basal sediments are approximately 42,000 B.P. and 20,000 B.P. for Hay Lake and Jacob Lake respectively. Based on pollen, local vegetation at Hay Lake between approximately 42,000 and 29,000 B.P. consisted of mixed conifer forest dominated by Pinus aristata, P. flexilis and/or P. strobiformis with Picea codominant. Of the identified pine species, 98% are haploxylon and most are pinyon pine. Pinyon pine was more widespread at lower elevations than today. The proposed 1 Mid-Wisconsin climate has greater winter precipitation and summers cooler than today. However, the climate was warmer and probably drier than the full-glacial. Treeline was above the site. The period 29,000 to 25,000 B.P. is climatically and vegetationally transitory to the full glacial. Yellow pines (p. ponderosa/contorta) are present for the first time and Picea pollen increases from previous levels. The full glacial (25,000 to 13,700 B.P.) at Hay Lake is characterized by an association of Picea and Gramineae pollen and at Jacob Lake by Picea and Artemisia pollen. A high elevation parkland at the forest-tundra ecotone surrounded Hay Lake. Open coniferous forest surrounded Jacob Lake. A conservative estimate of treeline depression is 570 m. Winters during the full glacial were warmer and wetter and summers were cooler and drier than today. The early and middle Holocene is characterized by an increase in open vegetation and in herbaceous pollen taxa; Artemisia at Hay Lake and Gramineae at Jacob Lake. The climate was cooler and wetter than today but less so than during the Pleistocene. Iron-mottled sediments and a hiatus in the pollen record at Jacob Lake (between about 11,850 and 900 B.P.) together with expansion of Artemisia at Hay Lake represent overall drought during the middle Holocene when compared with today although summer monsoons may have been intensified. Modern pollen assemblages begin at Hay Lake about 1700 B.P. and are not datable at Jacob Lake. The transition to modern conditions may have resulted from increased fire frequency at Hay Lake and from fire suppression by early settlers at Jacob Lake.

Lake sediments can play an important role in understanding and reconstructing temporal characteristics of the geomagnetic field, as they potentially offer near continuous high-resolution archives of magnetic information extending throughout the Holocene. To date lake sediment geomagnetic data has typically been excluded from British archaeomagnetic secular variation curves (SVC) due to uncertainties with the acquisition of magnetisation by lake sediments. This paper presents the argument that, with regards to British datasets, the real problem lies with poor chronological control and sets out to illustrate that with British archaeomagnetic data some progress has been made. The results indicate that it is not currently possible to resolve secular variation on a time scale of ¿100 years from published British lake sediment data but more success has been made with data from archaeological sediments. This level of detail has been considered necessary for the incorporation of lake sediment data into the British archaeomagnetic dataset, as the ability to resolve short-term geomagnetic changes is critical for the integration of any dataset into the British SVC. As the latter is predominantly employed to date archaeological architecture and artefacts requires that it has the ability to resolve changes over timescales relevant to human lifetimes. Using currently available data this retrospective critique confirms that, in archaeological sediments, depositional and thermoremanent magnetisation can record the same direction over the same time interval.

A pollen profile from varved lake sediments sampled at 10-year intervals and spanning the past 1000 years is analyzed to understand the effects of climate change and anthropogenic activity on forests in southwestern Quebec. The forests responded rapidly to changes in temperature and precipitation during the Medieval Warm Period and Little Ice Age as well as to land-use changes associated with the European Settlement of the area. The transition into the Little Ice Age was abrupt and had significant impact on the pollen production within a couple of decades. A synthesis of this record with other high-resolution and well-dated pollen data from the conifer-hardwood forest of eastern North America shows consistent results across the whole area, indicating that very-high resolution pollen data can provide insight into multi-decadal climate variability and its impact on forest vegetation. Tree-ring records from the region show inter-annual fluctuations not always consistent between sites, while high-resolution pollen data record multi-decadal to century changes which enable us to interpret climatic effects on plant communities.