| Title | Tidal modulation of river-flood deposits: how low can you go? |
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| Author | Maselli, V; Normandeau, A ; Nones, M; Tesi, T; Langone, L; Trincardi, F; Bohacs, K M |
| Source | Geology 2020 p. 1-5, https://doi.org/10.1130/G47451.1  Open Access |
| Image |  |
| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20190549 |
| Publisher | Geological Society of America |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Area | Po River; Italy |
| Lat/Long WENS | 11.6000 12.7000 45.2000 44.5000 |
| Subjects | surficial geology/geomorphology; sedimentology; stratigraphy; fossil fuels; Nature and Environment; Science and Technology; fluvial systems; tides; tidal deposits; tidal environments; deltas; fluvial
deposits; fluvial processes; discharge rates; floods; modelling; core samples; graded bedding; bioturbation; flow velocities; depositional cycles; storm deposits; paleogeography; petroleum resources; reservoir rocks; mudstones; depositional
environment; hydrography; sediment transport; stratigraphic analyses; alluvial sediments |
| Illustrations | location maps; satellite images; time series; profiles; geophysical images; plots; models |
| Released | 2020 04 17 |
| Abstract | Quantification of the interaction between river discharge and tides is vital to characterize fluvio-deltaic systems, to identify diagnostic elements of tidal signatures in the rock record, and to
reconstruct paleogeographies. In modern systems, even microtides can significantly influence delta morphodynamics; yet, many fundamental processes, particularly in prodeltaic settings, remain elusive. Here, by combining a unique process-product data
set acquired during a flood event of the Po River (Italy) with numerical modeling, we show that tidal signatures are recorded in the open-water prodelta zone of a microtidal system. Based on the analyses of box-cores collected before and after a
flood off the main distributary channel, we interpreted storm beds, tide-modulated flood strata of alternating normal and inverse graded beds, and rapid bioturbation. Modeling of the river discharge indicates that, at the peak of the flood, the
steepening of the water-surface profile forced by 0.15 m lowering of sea level during low tides generated an 8% increase in river flow velocity. The alternation of profile steepness and associated cyclicity in flow strength during consecutive tidal
cycles controlled the sediment load of the plume and, consequently, led to the deposition of tidal-modulated strata. Formation of microtidal signals appears to be enhanced in fluvio-deltaic successions characterized by multiple distributaries and in
basins where river floods are out of phase with storm-wave activity. Bioturbation of sediment, which can start during the waning stage of the flow, and erosion by storm waves hamper the preservation of tidal signals, unless rapid burial occurs. The
recognition of tidal-modulated strata in river-dominated settings may facilitate the characterization of mudstone reservoirs and reconstruction of paleogeographic conditions during deposition. |
| Summary | (Plain Language Summary, not published)
We combined a unique process-product dataset acquired during a flood event of the Po River (Italy) with numerical modeling. Low tides |
| GEOSCAN ID | 321865 |
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