Tidal dynamics in palaeo-seas in response to changes in bathymetry, tidal forcing, and bed shear stress

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Authors

Valentin Zuchuat, Elisabeth Steel , Ryan Mulligan, Daniel Collins, Mattias Green

Abstract

The overall goal of this study is to simulate hydrodynamic conditions in a palaeo-ocean basin in order to better understand the effects of tidal forcing on sedimentary strata and our interpretation of the rock record. The application of numerical models can help deciphering the complex temporal evolution and spatial distribution of energy in tide-dominated palaeo-ocean basins recorded within sedimentary strata. Herein, palaeotidal modelling of the epicontinental, Upper Jurassic (160 Ma, lower Oxfordian) Sundance and Curtis Seas sheds lights on the regional-scale variations in tidal dynamics as a response to possible realistic changes in ocean tidal forcing, bathymetric configuration, and bottom drag coefficient. The use of a numerical model forced with an M2 tidal constituent at the open boundary has shown that the magnitude and the location of tidal amplification, and the variability in current velocity and bed shear stress in the basin were controlled by palaeobathymetry. Second, numerical results obtained using a depth of 600 m at the ocean boundary of the system enables the prediction of a distribution of sedimentary facies similar to the one observed in the lower Curtis Formation, except in the southernmost parts of the Curtis Sea, close to the palaeoshoreline. There, the sediments could have been transported from the neighbouring arid coastal plain by aeolian processes before being reworked by tidal or alongshore currents during a subsequent transgression. In this particular scenario, the Sundance Sea and the Curtis Sea would have reached maximum depths of 240 m and 40 m respectively, which we consider to be a realistic palaeobathymetric configuration based on geological observations. In this context, the simulated 2.60 m tidal range of the Curtis Sea would classify it as a meso-tidal system. The results suggest that sedimentary successions deposited in a tide-dominated basin could be considered as non-unique since one specific succession could have been deposited under several, equally-valid relative sea-level, and/or sediment supply, and/or tidal range histories. Reciprocally, it is possible to consider sediment-supply variations and relative sea-level change (and its effects) in tide-dominated basins as non-unique, since one relative sea-level curve can lead to the deposition of different sedimentary successions in different parts of the basin. Overall, results of our detailed numerical model indicate the need for considering the variations of tidal dynamics associated with changes in palaeobathymetric configuration when developing a geological model of a tide-dominated sedimentary basin.

DOI

https://doi.org/10.31223/X50S3G

Subjects

Physical Sciences and Mathematics

Keywords

sequence stratigraphy, Upper Jurassic, palaeooceanography, tidal deposits, relative sea-level change, non-uniqueness, sequence stratigraphy, Upper Jurassic, Curtis Formation, palaeooceanography, tidal deposits, relative sea-level change, non-uniqueness, Curtis Formation

Dates

Published: 2020-12-21 13:13

Last Updated: 2020-12-21 21:13

License

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:
None

Data Availability (Reason not available):
All the data necessary for these simulations (>500 Gb) can be saved on external hard-drives and sent by mail

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