Beach-morphodynamic changes conditioned by the Holocene sea-level fluctuation: mesotidal beaches of Northern Patagonia

ISLA, F.I.; BÉRTOLA, G.R.; FERNÁNDEZ, J.M.; BEDMAR, J.M.; TOFFANI, M.; GARZO, P.A.

Acta Geológica Lilloana

Fundación Miguel Lillo

Año: 2023 vol. 34 p. 111 - 128

Beach morphodynamics are stated as depending on wave climate, tidal range andgrain size. Sediment availability is a conditioning factor biased to inheritance factors.Seven natural beaches from Northern Patagonia: 4 from Southern Buenos Aires and3 from Eastern Rio Negro Province were surveyed during several years. La ChiquitaBeach is characterised by an abundance of fine sand supplied by the Colorado Riverdelta. Pocitos Beach is rather stable although it is changing due to colonisation bythe invasive reef-building oyster Crassostrea virginica. Faro Segunda Barranca is anopen-ocean beach, very affected by extratropical storms coming from the SE. Thebeach of Villa Siete de Marzo has a very active dynamics affected by the embankments of the Negro River outlet, and episodic storms. The beach of Balneario ElCóndor is very wide with an intense strong longshore drift from west to east. Thebeach in front of the San Matías Lighthouse (Villarino Peninsula) is controlled by anabrasion platform close to the low-tide limit. Las Grutas beach is also controlled by an abrasion platform but the sand abundance is related to the ebb-tidal delta of theSan Antonio Gulf. Open-ocean beaches in Buenos Aires province are very affectedby a drift towards the north delivered by South Atlantic waves. On the other hand,Rio Negro beaches are affected by the strong westerly winds blowing alongshore.