New quantitative tools for paleoclimatic reconstructions and applications to paleosols throughout the geologic record.

摘要

While soil science is a scientific discipline with over one hundred years of history, the study of fossil soils (paleosols) is a comparatively recent development. Because paleosols formed at the Earth's surface, in direct contact with the atmosphere, they hold great potential as a repository of paleoclimatic and paleoenvironmental information. Much of the previous work in paleopedology (the study of paleosols) has been descriptive and focused on finding morphological characteristics in modern soils and on using them as analogues for the formation of the paleosols. While descriptive paleopedology has and will always form the basis of paleosol studies, more fundamental insights into weathering processes, the role of changing atmospheric conditions in weathering, and the role of soils in biogeochemical element cycling are possible when a more quantitative approach is taken. Because paleopedology is still a branch of paleoclimatology in its nascence, many fundamental properties of pedogenetic processes, easily measurable in modern soils, remain difficult to constrain for paleosols.; New quantitative tools are described herein for determining how much a paleosol was compacted during burial using an equation derived from first principles and empirical constants (Chapter II), for determining mean annual precipitation and mean annual temperature using measurements of the degree of chemical weathering (Chapter III), for determining whether the distribution of potassium is due to soil formation or to metasomatism (Chapter IV), and for estimating soil gas conditions (Chapter VIII). The tools are applied in a series of case studies aimed at understanding soil formation during a time of elevated carbon dioxide levels (Chapter IV), at understanding paleohydrology (Chapter V), at understanding the regional distribution of past precipitation (Chapter VI), and at understanding how climatic and soil forming conditions vary on short times scales as in the recent glacial/interglacial cycling of the last 400,000 years (Chapter VII).; This dissertation contains my previously published and co-authored materials as parts of Chapters II--IV, and VIII.