This study utilizes major-, trace- and rare earth elements, as well as radiogenic isotopes (Rb-Sr, Sm-Nd, Pb), in bulk sediment, extracted glass shards, and discrete ash layers, at Ocean Drilling Program Site 1149 (Izu-Bonin Arc), Deep Sea Drilling Project Site 52 (Mariana Arc), and Integrated Ocean Drilling Program Sites C0011 and C0012 (Nankai Trough) in order to characterize and quantify the abundance of dispersed ash, rather than discrete ash layers, in sediments from the Northwest Pacific Ocean. Combination of the geochemical methods with multivariate statistical techniques, such as Q-mode Factor Analysis and multiple linear regressions, allows for differentiation of unique chemistries of the dispersed ash, and the terrigenous components. Therefore, we can document sources that change through time and space. At Site 1149 the bulk sediment is a mixture of two dust and two dispersed ash sources. The two dust sources show contrasting accumulation patterns changing over at a tectonically and climactically active time in Earth's past (~22 Ma) and yield a more complete history of Asian aridity than has been previously considered. We interpret the source of the ashes as basalt from the Izu-Bonin Front Arc (IBFA) and rhyolite from the Honshu Arc (HR). Comparison of the dispersed ash component to the discrete ash layers suggests that eruption frequency, rather than eruption size, drives the dispersed ash record. In contrast, at Site 52 Chinese Loess, IBFA, dispersed boninite from the Izu-Bonin arc, and a dispersed felsic ash of unknown origin are the sources. Interestingly, there are no boninite layers, yet boninite is dispersed within the sediment. Changes in the volcanic and eolian inputs through time indicate strong arc- and climate-related controls. The bulk sediment at Site C0011 is characterized by eolian dust, HR, and a dacite of unknown origin. Site C0012 is comprised of eolian dust, a dacite of unknown origin, as well as dacite and andesite from the Izu-Bonin Arc. Analysis of the total ash record at these two sites provides insight into subduction zone mass balance and water budgets as well as information about the changes in physical properties that result from the alteration of volcanic ash.

Global climate is controlled by two factors, the amount of heat energy received from the sun (solar insolation) and the way that heat is distributed Earth's surface. Solar insolation varies on timescales of 10s to 100s of thousands of years due to changes in the path of Earth's orbit about the sun (Milankovitch cycles). Earth's internal boundary conditions, such as paleogeography, the presence/absence of polar icecaps, atmospheric/oceanic chemistry and sea level, provide distribution and feedback mechanisms for the incoming heat. Variations in these internal boundary conditions may happen abruptly or, as in the case of plate tectonics, take millions of years. We use geochemical and sedimentological techniques to investigate the response of ocean chemistry, regional aridity and atmospheric and oceanic circulation patterns to climate change during both greenhouse and icehouse climates. To explore the connection between orbitally-forced changes in solar insolation, continental aridity and wind, we generated a high-resolution dust record for ~58 Myr old deep-sea sediments from Shatsky Rise. Our data provide the first evidence of a correlation between dust flux to the deep sea and orbital cycles during the Early Paleogene, indicating dust supply (regional aridity) responded to orbital forcing during the last major interval of greenhouse climate. The change in dust flux was comparable to that during icehouse climates implying subtle variations in solar insolation have a similar impact on climate during intervals of over-all warmth as they do during glacial-interglacial states. The Carboniferous Period (359-299 Ma) marks a critical time in Earth's history when a series of tectonic and biological events caused a shift in the mean climate state from a global "greenhouse" to an "icehouse". Geochemical records extracted from sedimentary rocks deposited in shallow epicontinental seaways are increasingly being used to infer relationships between tectonism, carbon cycling and climate and therefore are assumed to reflect global ocean processes. We analyzed radiogenic isotopes in biogenic apatite along a North American transect to constrain the degree of geochemical coupling between the epicontinental seas and the open ocean. Our results argue strongly for decoupling of North American seaways from the open ocean by latest Mississippian time.