Journal
GEOMORPHOLOGY
Volume 303, Issue -, Pages 13-29Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.geomorph.2017.11.016
Keywords
Estuary; Sea-level change; Sediment flux; Incised-valley
Funding
- Tertiary Education Commission Top Achievers' Doctoral Scholarship
- Massey University Research Fund
- Geoscience Society of New Zealand Wellman Research Award
- School of People, Environment, and Planning, Massey University
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The Manawatu incised-valley estuary was rapidly infilled between 12,000-4700 cal. yr BP. A combination of empirical measurements of sedimentation rates, a reconstruction of relative sea-level (RSL) change, and digital elevation models of key surfaces within the Holocene sedimentary fill of the valley were integrated to produce a numerical model to investigate the influence of the system controls of sea-level change, sediment flux, and accommodation space on the rapid infilling history of the palaeo-estuary. The numerical model indicates that sediment flux into the palaeo-estuary was greatest during the Holocene marine transgression between 12,000-8000 years BP. The average rate of sediment deposition in the estuary during this period was similar to 1.0 M m(3) yr(-1). This rapid rate of sedimentation was controlled by the rate of accommodation space creation, as regulated by the rate of sea-level rise and the antecedent configuration of the valley. By the time sea levels stabilised c. 7500 cal. yr BP, the palaeo-estuary had been substantively infilled. Limited accommodation space resulted in rapid infilling of the central basin, though sediment flux into the estuary between 7100 and 4500 cal. yr BP was at a lower rate of 234,000 m(3) yr(-1). The limited accommodation space also influenced hydrodynamic conditions in the estuarine central basin, driving export of fine-grained sediment from the estuary. Once the accommodation space of the estuarine basin was infilled sediment bypassed the system, with a consequent reduction in the sedimentation rate in the valley. More accurate partitioning of the sources of sediment driving the infilling is necessary to quantify sediment bypassing. Post-depositional lowering of RSL index points from the valley is driven by neotectonics and sediment compaction. (C) 2017 Elsevier B.V. All rights reserved.
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