Environmental changes related to the transgressive and sea-level highstand (7-5.4 Kyr) at the NE coastal plain of Buenos Aires (Argentina)

LUENGO MARIEL; ANGÉLICA BALLESTEROS PRADA; VILANOVA ISABEL; BERNASCONI EMILIANA; FUCKS ENRIQUE

QUATERNARY INTERNATIONAL

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2021

1040-6182

This study integrates geomorphological and paleontological (pollen, non- pollen palynomorphs, foraminifera and mollusk shells) proxy data from the central zone of Bahía Samborombón (~35.6°S) in order to reconstruct the salt marsh vegetation history and environmental changes, and to develop a geomorphologic evolution model during the mid-Holocene sea-level transgressive phase corresponding to MIS 1. Within a short time interval several and rapid environmental changes took place, affecting vegetation and microfauna, as well as the geomorphological features; between~6800 cal yr BP and 6670 cal yr BP a middle to high salt marsh vegetation developed in an extensive and open tidal plain where wide and long paleo tidal channels were flowing. This salt marsh transitioned, between ~6670- ~6535 cal yr BP, into a low salt marsh vegetation in response to the continue sea-level rise, while the coastline position moved toward inland. Between 6535 a 6453 cal yr BP sea-level reached the highstand with the consequences of unstable conditions related to the inundation of the extensive coastal plain, except for the elevated areas such lunettes and ridges. From ~6400 cal yr BP, autochthonous Tagelus plebeius mollusk assemblages indicate a stabilized sea-level period. After 5500 cal yr BP sand ridge and beach ridges formed, prograding towards the east (seaward) probably in relation to the beginning of the sea-level regressive phase that provoque the isolation of environments developed behind that became protected from the action of direct marine tidal influence. Aeolian and pedogenetic processes took place on the ancient tidal plain at ~10 km westward from the present coastline.