Stratigraphic successions of sedimentary rocks represent an important repository for signals pertaining to the history and evolution of Earth. Whereas the specific processes reflected by the stratigraphic record differ with respect to a given depositional environment, deposits in deep-marine settings, particularly passive margins, provide a unique, long-term record of paleoclimate, paleoceanography, and tectonics affecting the basin in question. Whereas deep-marine strata may be used to answer myriad of questions regarding the evolution and development of Earth systems, this dissertation narrowly targets two distinct aspects of sedimentation in deep-sea settings. The first two chapters focus on the utility of sortable silt in reconstructing bottom-current intensity linked to major shifts in climate. First, the relationship of sortable silt to flow velocity was tested under controlled conditions in a flow-through flume. This chapter investigates the correlation of sortable silt metrics across several experimental parameters, which is found here to dispute longstanding assumptions that multiple metrics must correlate to infer sediment sorting by deep currents. Additionally, the results are compared to calibrations from natural settings, where the correlation between the two datasets is remarkably similar, validating the relationship of sortable silt with current velocity in the deep ocean. Chapter two leverages sortable silt to investigate the long-term evolution of the Deep Western Boundary Current in the North Atlantic, targeting contourite drifts offshore Newfoundland to investigate the Eocene-Oligocene Transition (EOT), the most recent global greenhouse-to-icehouse transition. Results suggest that the Deep Western Boundary Current intensified gradually from 35-26 Ma, not abruptly at the EOT, and change consistent with deepening of the Greenland-Scotland Ridge and enhanced overflow of deep water into the North Atlantic. Chapter three utilizes detrital zircon U-Pb dating to characterize source-to-sink pathways and linkages during the rift-to-drift transition, in the Early Cretaceous, along the U.S. mid-Atlantic passive margin. This work shows that onshore and offshore system segments were initially disconnected, and progressively integrated over the course of ~45 Myr. Taken together, this work demonstrates a focused yet powerful example of how deep-marine sedimentary systems can be leveraged to robustly model major changes throughout Earth history. / Doctor of Philosophy / Sediments and sedimentary rocks deposited in the deep ocean house long-term signals pertaining to important Earth processes and properties. The nature of a given deposit, for example, can be the direct result of climatic conditions or tectonic development in adjacent mountainous and coastal environments. While the range of questions that can be answered using the sedimentary record is vast, this dissertation narrowly focuses on 1) how deep-ocean currents change over long periods of time, and 2) how onshore and offshore depositional environments correlate during the early phases of supercontinent break-up. To address the reconstruction of deep-ocean currents, laboratory experiments were performed to test how the sortable silt proxy – the 10-63 um fraction of a deposit – correlates with current velocity, the first controlled test of the proxy since its inception by paleoceanographers nearly three decades ago. Sortable silt is then applied to sediments of Eocene-Oligocene age, recovered from contourites offshore Newfoundland, Canada, to assess the long-term behavior of the Deep Western Boundary Current in the North Atlantic across the Eocene-Oligocene Transition (EOT). While the EOT, a major global cooling that occurred ~33.7 Ma, is well-studied with respect to Antarctica and its surrounding ocean basins, little is known about the paleoceanographic response of the North Atlantic. Grain-size records show a gradual increase in sortable silt before, during, and after the EOT, through entirety of the 9 Myr record. This trend is interpreted to reflect a long-term invigoration of the Deep Western Boundary Current in North Atlantic, likely due to progressive deepening of the Greenland-Scotland Ridge. The final chapter leverages detrital zircon U-Pb geochronology to compare sediment provenance of Early Cretaceous fluvial sandstones with coeval, distal turbidite sands. Results suggest that coastal rivers were fed by a single source terrane during the earliest Cretaceous, disconnected from the regional catchment feeding the submarine fan. By the Aptian-Albian, coastal rivers share a detrital zircon signature with turbidite strata, suggesting that rivers were progressively integrated into the sediment-routing system feeding the offshore margin.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/108095 |
| Date | 02 February 2022 |
| Creators | Parent, Andrew Michael |
| Contributors | Geosciences, Romans, Brian W., Spotila, James A., Gill, Benjamin C., Eriksson, Kenneth A., Stocker, Michelle |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/octet-stream, application/octet-stream, application/octet-stream, application/octet-stream, application/octet-stream, application/octet-stream, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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