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Conference papers

Architectural variability of a coarse-grained barrier system in a hypertidal environment (Santa Cruz Estuary, Argentinean Patagonia)

Abstract : The southern coast of Argentina is composed of many coarse-grained coastal barriers, which are mostly concentrated at the mouth of a few large rivers that drains the Andean mountains. As the Patagonian estuaries are characterized by tidal ranges that are among the largest in the world, coastal barriers are exposed to high amplitude tide-induced sea-level changes as well as strong tidal currents. In order to better understand the influence of tides in wave-built sedimentary bodies, an in-depth analysis of the architecture of barrier systems has been realized at the mouth of the Santa Cruz estuary (50°S). Maximum tidal range is 12 m in this estuary. A great variety of morphologies compose both sides of the estuary inlet, from simple spits and barrier spits to beach ridges. Barrier spit and beach ridges characterize the southern side, whereas elongated simple spits and spit barriers isolating large tidal flats are more developed on the northern side. As a consequence of this configuration the northern system is much wider than the southern one (6 km vs 1 km). The site was investigated using ground-penetrating radar (400 MHz GSSI antenna), along with the analysis of digital elevation models and some sedimentological observations. Cross-shore and long-shore profiles, with a penetration depth up to 4 meters, show a large range of radar facies attributed to erosional surfaces, beach face progradation, along-drift elongation, hooks and spit terminus development, and washover deposits. The analysis of the radar architecture allows reconstructing the development of individual morphology, and helps to differentiate the influence of wave- and tide-related processes. The most open-sea barrier spit systems show a classic development controlled by the wave-related littoral drift entering into the estuary (onshore directed), and enhanced due to shore parallel flood currents into the inlet. In contrast, in the innermost part of the northern side, spits and barrier spits feature contrasting morphologies, structures and directions of elongation, either landward or seaward, reflecting a complex combination between wave-, tide-and fluvial dynamics on their construction. One of the spits imaged with the GPR shows an intense reflection that has been associated with the top of the tidal flat on which the spit migrates (Fig. 1). The GPR lines highlight the control of underlying substrate on spit morphologies A same morphology is thus characterized by different architectures; in Figure 1B the prograding sequence follows a transgressive sequence, while in Figure 1C the transgressive sequence cannot be observed in the architecture due to the highest elevation of the tidal flat. In the southern side of the estuary, the barriers show extensive progradational sequences with different slopes that seem to depend on the spit morphology, and therefore on the exposure to ocean swells.
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https://hal-normandie-univ.archives-ouvertes.fr/hal-03661792
Contributor : Léo Pancrazzi Connect in order to contact the contributor
Submitted on : Saturday, May 7, 2022 - 10:44:37 PM
Last modification on : Sunday, May 8, 2022 - 3:35:38 AM

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  • HAL Id : hal-03661792, version 1

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Léo Pancrazzi, Bernadette Tessier, Pierre Weill, Dominique Mouazé, José Cuitiño, et al.. Architectural variability of a coarse-grained barrier system in a hypertidal environment (Santa Cruz Estuary, Argentinean Patagonia). 10th International Congress of Tidal sedimentology, May 2022, Matera, Italy. ⟨hal-03661792⟩

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