Geomorphological Evolution of the Patagonian Coast Surrounding the Golfo Nuevo (Chubut, Argentina) during Late Quaternary: Overview and New Proposal

摘要

The main contribution of this paper is a new interpretation of the geomorphological evolution of the North Patagonian coast surrounding the Golfo Nuevo from Mid-to-Late Pleistocene until present. The proposed model shows how continental and marine landforms evolved during the Late Quaternary. According to this, the Golfo Nuevo depression formed during the Middle Pleistocene (＞130 ka) above previous fluvial terraces, which are attributed to different stages of the Chubut river. Several pediment types and levels were also identified: (1) flanking pediment (level 1) associated with an ancient fluvial valley; (2) convergent pediment related to a previous depression of Golfo Nuevo (level 2), both assigned to Middle Pleistocene; and (3) a littoral pediment (level 3) linked to a Holocene highstand level. The height and position of accretion marine terraces are discussed, in addition to their previous dating. It can be assumed that Golfo San Matias was flooded twice as a consequence of marine transgressions (marine isotopic stage [MIS] 5 and MIS 1). Likewise, Golfo Nuevo and Golfo San Jose were affected only once, during the maximum Holocene transgression (MIS 1). This paper highlights the importance of reconstructing the geomorphological evolution of a coastal area of the Patagonia as a result of a combination of changes linked to sea-level variations (mainly associated with glacio-eustasy) and climate, paleo-shorelines records, and continental landforms through Late Quaternary. The proposed geomorphological model can be considered a novelty because of the complex integration of continental and marine landforms and the study of their relative relation.