During his journey on the Beagle, Darwin observed the uniformity in the elevation of coastal Eastern Patagonia along more than 2000 km. More than one century later, the sequences of Quaternary shorelines of eastern Patagonia have been described and their deposits dated but not yet interpreted in terms of geodynamics. Consequently, we i) mapped the repartition of the Quaternary coastal sequences in Argentinean Patagonia, ii) secured accurate altitudes of shoreline angles associated with erosional morphologies (i.e. marine terraces and notches), iii) took into account previous chrono-stratigraphical interpretations in order to calculate mean uplift rates since~440 ka (MIS 11) and proposed age ranges for the higher and older features (up to~180 m), and iv) focused on the Last Interglacial Maximum terrace (MIS 5e) as the best constrained marine terrace (in terms of age and altitude) in order to use it as a tectonic benchmark to quantify uplift rates along the entire passive margin of Eastern South America. Our results show that the eastern Patagonia uplift is constant through time and twice the uplift of the rest of the South American margin. We suggest that the enhanced uplift along the eastern Patagonian coast that interested Darwin during his journey around South America on the Beagle could originate from the subduction of the Chile ridge and the associated dynamic uplift.

The coastal fringe of Central Patagonia preserves a unique and spectacular succession of landforms discontinuously formed since MIS 11 up to the Holocene. The study area, stretching from 44° 34' to 44° 54' S of latitude, is crucial to analyze the complexity of multitemporal shorelines formation and preservation along the Atlantic coast of South America. We used depositional and erosional landforms to get reliable and well chronologically constrained sea level markers. In particular, multistoried swale infillings, produced by a complex relationship between river discharge and marine activity, were considered the most accurate sea level markers. Palaeo sea level elevation was assessed cross checking evidence obtained from different marker types and considering the original position of each of the measured features with respect to its contemporary sea level. A dedicated field measurement of the markers current elevation was necessary, considering the macrotidal regime that currently affects this coastal area. Literature and new data provide an excellent set of dating, useful to chronologically constrain all the palaeo shorelines that have been identified. On the whole five sea level highstands have confidently been referred to Holocene (maximum transgression peak), MIS 5, 7, 9 and 11. Sea level elevation for each of them was stated respectively at 2.5, 7.5, 10.5, 22.5 and 32.5 m asl, but different error bars and levels of accuracy are assigned to each of these estimates, based on innovative criterions that are widely discussed in the text. Our work enabled us to obtain new, self-consistent values of the last 400 ka uplift rates for this coastal tract and to compare them with those calculated by other authors, suggesting for the investigated time span a moderate coastal uplift.

Stratigraphic, morphologic and radiocarbon data from Puerto Deseado coastal area (Santa Cruz Province, Argentina) indicate that the Holocene coastline formed in response to the discontinuous aggradation of coarse gravely beaches since c. 6300 cal. yr BP related to a progressive falling of relative sea level. Beach ridge crests crudely approximate to the sea level showing at least three steps of aggradation and relative sea-level lowering. Two inactive abrasive notches at c. 7.9 and 3.4 m a.s.l. have recorded this sea-level trend, suggesting two important phases when sea level was stationary. This allows the estimation of a rate of relative sea-level fall in the last c. 3500 years of c. 1.8 mm/yr. Moreover, notches and morphological data indicate that the crest of the beach ridges exceeded the sea-level height by c. 2 +/- 0.5 m. This value provides a reasonable regional estimate to be applied to produce comparable relative sea-level curve for Atlantic Patagonia coast

The Holocene evolution of the Cabo Raso bay (Atlantic Patagonian coast) was reconstructed by means of geomorphological, stratigraphic, and palaeontological analyses, assisted by radiocarbon dating. Six beach ridges were individuated and mapped in the field, as well as some rocky erosional landforms, e.g., inner margins of marine terraces. Thanks to quarry sections, the internal structure of beach ridges, their relationship with continental deposits, and the fossil contents were determined. Two specimens of Aulacomya atra and Brachidontes purpuratus were radiocarbon dated at 6055 and 4500 6 20 YBP, respectively. The bedrock outcrops at the base of an analysed section allowed us to associate the age of the samples collected to the elevation of the marine transgression surface upon which the entire deposit rests. Because a beach ridge is a regressive form, the elevation of the base of the dated deposit was assumed to be equivalent to or slightly lower than the maximum sea-level stationing, represented by the inner margin of the coheval marine terrace. The altimetric correlation between the base of the beach ridge dated at 6055 6 20 YBP and the inner margin of the corresponding marine terraces allowed us to constrain the maximum Holocene marine transgression to about 3 to 2 m above sea level. This elevation for the maximum Holocene transgression is lower than that shown by most of the previous data for Patagonian coast, but it shows a crude agreement with recent estimates coming from geophysical models that report, for this area, a departure from the eustatic value of sea level, mainly caused by glacioisostatic process. This means that the employment of marine erosional landforms, associated with other multisource field data, proved to be determinant for reconstructing the sea-level variation in the Patagonian coast

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