Wooldridge, Peter
(2021)
Quantifying the Role of Floodplain Peat in Carboniferous Fluvial
Systems.
PhD thesis, University of Liverpool.
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Abstract
Sediment is generated in mountainous regions and transported across the terrestrial segment to the marine segment by river systems. Basin scale and channel belt fluvial architecture is determined by river mobility and a river’s ability to traverse its floodplains through lateral river migration and river avulsion. Floodplain peat generation and accumulation occurs as an autogenic process that is reported to modify a river’s ability to transverse its floodplain and thereby modify basin and fluvial architecture. However, the mechanism of modification and the extent to which peat may modify river dynamics and dictate basin architecture remains relatively unknown. The Carboniferous period represents the foremost period of peat production (observed today as coal) in the rock record. Using the coal-rich Carboniferous Pikeville Formation in Kentucky, this study shows how the presence of floodplain peat modifies fluvial systems through enhanced bank strength and elevated floodplain aggradation by in-situ generated peat. Using a high-resolution field-core meta dataset consisting of 846 sedimentary logs covering an area 6,000 km2 , this study found that a combination of rapid peat aggradation and its resistance to mechanical erosion limited the ability of rivers to traverse the width of the system and, in doing so, promoted vertically stacked multistorey channel belts through compensational steering of meandering rivers. Mobility analysis conducted in this study found in-situ peat deposits increase avulsion timescales by a minimum 2.5 times, and potentially increase system mobility by a minimum 2.5 times. Through the comparison of ancient lateral migration rates to modern systems, the results of this study found that peatrelated increase in system mobility may not have translated into increased lateral migration; therefore, the potential increase in mobility is interpreted as having promoted the downstream accretion of channel bars. These results suggest that thick 5 | P a g e floodplain peat can generate confinement akin to that of valley settings. Furthermore, this study found that by inhibiting river migration, peat reduces the volume of sand deposited in the terrestrial setting (delta plain), increasing the volume exported to the marine segment. These finding are supported by the results of physical models upon the impact of delta cohesion upon the delta plain and delta plain processes. The results of this study demonstrate how voluminous in-situ floodplain peat modified fluvial systems of the Carboniferous and partially dictated fluvial architecture. This work has implications for understanding deep time records of river systems, basin and fluvial architecture, and sediment delivery to marine environments. It is hoped this work to be a starting point for (i) examination and re-examination of large sandstone bodies within coal rich successions, especially the Carboniferous, (ii) further investigations into the sediment transport and deposition characteristics of fluvial systems within peat-rich floodplains, and (iii) more detailed process-based and experimental modelling of sediment transport and deposition within coal rich source to sink systems.
| Item Type: | Thesis (PhD) |
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| Divisions: | Faculty of Science and Engineering > School of Environmental Sciences |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 14 Jan 2022 09:15 |
| Last Modified: | 18 Jan 2023 21:24 |
| DOI: | 10.17638/03143213 |
| Supervisors: |
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| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3143213 |
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