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Multiple post-last glacial maximum (LGM) moraines occur in the Sawtooth Range of the Rocky Mountains in central Idaho. Although relative ages of the moraines have been studied, few numerical ages exist for these moraine sequences. In this study, the ages of LGM and late glacial (Younger Dryas) moraines in the Redfish Lake drainage of Idaho are constrained with 23 new, cosmogenic, 10Be dates. Results of this study include developing a new chronology for the Redfish Lake late Pleistocene moraines that are consistent with regional morainal ages. New cosmogenic 10Be data from boulders on Bull Lake moraines at Redfish Lake are consistent with other dates obtained from Bull Lake moraines elsewhere in the Rocky Mountains. Ages of 107 to 206 ka and 238 to 323 ka suggest synchroniety with other Bull Lake glacial advances in the Wind River Range, Tetons, and Yellowstone. New cosmogenic 10Be data from boulders on terminal moraines in Redfish Lake valley, Idaho, show a LGM at 18.5 ± 0.9 ka to 15.6 ± 0.8 ka, recessional (or minor readvance) moraines deposited between 15.4 ± 0.7 ka and 14.2 ± 0.7 ka; and a Younger Dryas (YD) phase at 11.4-11.7 ± 0.5 ka. Boulders on an LGM moraine at Alturas Lake, Idaho were 10Be dated in order to supplement and test the existing concepts of glaciation there. Ages of 17.2 ± 1.0 ka and 16.8 ± 0.8 ka indicate that this moraine is late Pinedale, not mid-Pinedale as previously suggested by Thackray et al. (2004). The late Pleistocene ice chronology at Redfish Lake is consistent with the glacial chronology in the Wind River Range, WY (LGM 24 ka to l8 ka; recessional deposits 18 ka to 16 ka and YD 11.5 ka); Yellowstone, WY (LGM advances: 29.5-22.5 ka, and 19.5- 5.5 ka); Wallowa Mountains, OR (two 10Be dated LGM advances: 21.1 ± 0.4 ka and 17.0 ± 0.3 ka, and YD advance: 10.2 ± 0.6 ka); Crowfoot Lake, Canada (YD advance: 11,330 ± 220-10,100 ± 70 14C yrs B.P.); and many other places throughout western North America. This research provides chronological constraints on Pinedale LGM (~18.5 ka) moraines, Pinedale recessional (between 18.5 and 14.2 ka) moraines, and Younger Dryas (~11.4 ka) moraines in the Sawtooth Range of the Rocky Mountains, and assists in determining the areal extent of the late Pleistocene cold period in the Western United States.
The assumption that prehistoric Native American land use practices had little impact on the North American landscape persists in the literature. However, recent research suggests the effects of prehistoric burning, deforestation and agriculture may potentially have been greater than previously considered. To resolve this discrepancy, quantitative estimates of changes in human population size and forest structure and composition over the course of the Holocene are needed. This thesis addresses this need by providing radiocarbon-based paleodemographic reconstructions and pollen-inferred estimates of vegetation change, as well as analyses of associations between the two at both continental and regional scales, from the late Pleistocene to the Anthropocene. One way to estimate paleodemographic change is to use the number of radiocarbon (14C) dates from a given area to study patterns of human occupation through time. A review of the literature and compilation of existing databases relevant to this method showed there is now sufficient data to study the paleodemographic history of many regions around the world. An analysis of 14C datasets from North America and Australia compared well with model-based reconstructions of past demographic growth, and provided higher frequency fluctuations in population densities that will be important for future research. Using a kernel density estimation approach, the first estimates of prehistoric population density for North America were obtained and synthesized into a series of continental-scale maps showing the distribution and frequency of 14C dates in the Canadian Archaeological Radiocarbon Database (CARD). The maps illustrated the space-time evolution of population and migration patterns, which were corroborated by independent sources of evidence. A methodology based on the statistical evaluation of cross-correlations between population and plant abundance was then developed to analyze the associations between these population estimates and plant communities derived from pollen databases. Periods of high spatial cross-correlation (positive and negative) between population and plant abundance were irregular and did not improve over time, suggesting that ancient human impacts are not discernable at a continental scale, either due to low populations or varying human land use practices. To further examine the relationship between pollen data and human land use at a regional scale, estimates of plant density and landscape openness are needed. The REVEALS (Regional Estimates of VEgetation Abundance from Large Sites) model corrects for the non-linear relationship between pollen production and plant abundance and can therefore be used to map histories of land use and land cover change. The model was applied to pollen records from lake sediments in the deciduous forest of southeastern Quebec. A preliminary analysis comparing these results to population density revealed low population during times of high Populus abundance and high population following the appearance of the mixed temperate forest suggesting a discernable human-environment association at regional scales. Overall, the results of thesis support the growing body of literature that suggests prehistoric Native Americans impacted their environments and that these impacts can be detected and quantified by integrating archaeological and paleoecological information. However, the timing, location, and intensity of human land use has changed in both space and time, suggesting regional- to local-scale analyses of human-environment interactions are most appropriate for continental North America. The methodology presented here can be used to study additional North American regions for the purpose of developing a continental history of human-environment interaction.
ABSTRACT: The magnitude of global sediment flux from streams to the oceans over the last 5 Ma is poorly quantified, yet important for predicting future fluxes and deciphering the relative control of tectonic uplift, climate change, vegetation, and related feedback mechanisms on landscape evolution. Despite numerous proxy studies on global sediment delivery to the oceans, it remains uncertain whether bulk sedimentation increased, decreased, or remained approximately constant across one of the most significant global climate changes: the Plio-Pleistocene transition. New developments and strategies in the application of cosmic-ray-produced isotopes, in part developed by this thesis, provide records of pre-historic denudation of confined fluvial catchments in Texas and Yukon. Non-glaciated, tectonically passive regions were targeted in contrast to other studies on modern sedimentation rates in order to isolate the climate influence from glacial and tectonic controls. The results suggest that average catchment temperature, and surficial processes and other factors such as vegetation cover associated with temperature, are the primary controls on the variation in landscape denudation in regions lacking tectonics and direct glacial cover. Specifically, warmer temperatures yield higher denudation rates, both at the scale of glacial-interglacial climate change and over the Plio-Pleistocene transition. The implication is that stream sediment flux to the ocean from tropical and temperate regions was higher during the Pliocene than in the Quaternary. However, this may have been balanced by an increase in sediment flux from regions covered by warm-based glaciers during glacial periods, or by increased temporary continental storage during interglacial periods.
Reprint of the original, first published in 1882.
This introductory textbook introduces the basics of dating, the range of techniques available and the strengths and limitations of each of the principal methods. Coverage includes: the concept of time in Quaternary Science and related fields the history of dating from lithostratigraphy and biostratigraphy the development and application of radiometric methods different methods in dating: radiometric dating, incremental dating, relative dating and age equivalence Presented in a clear and straightforward manner with the minimum of technical detail, this text is a great introduction for both students and practitioners in the Earth, Environmental and Archaeological Sciences. Praise from the reviews: "This book is a must for any Quaternary scientist." SOUTH AFRICAN GEOGRAPHICAL JOURNAL, September 2006 “...very well organized, clearly and straightforwardly written and provides a good overview on the wide field of Quaternary dating methods...” JOURNAL OF QUATERNARY SCIENCE, January 2007
10 papers using new conceptual frameworks to interpret late Quaternary cultural and environmental remains. Chapters are composed largely of the proceedings of a symposium held at the Society for American Archaeology meetings in 1982.