New insights on the Holocene marine transgression in the Bahía Camarones (Chubut, Argentina)

Abstract

The stratigraphic reconstruction of the northern sector of the Bahía Camarones (Chubut, Argentina) allowed to improve our understanding of the Holocene marine transgression in the area. The first phase of the maximum of the transgression, is interpreted as dominated by the high rate of eustatic rise of sea level until ca. 6-7 ka BP possibly associated to sedimentary starvation as suggested by fossil accumulation. After this first phase, the general trend indicates a progressive fall of the relative sea level after the Middle Holocene high stand as documented in other parts of south America Atlantic coast. Our data, coupled with the robust radiocarbon data set available for the area from literature, indicate three main local steps of coastal aggradation between ca. 6600 and 5400 yr BP (ca. 7000-5600 yr cal BP), ca. 3300 and 2000 yr BP (ca. 3100-1700 yr cal BP), and ca. 1300-500 yr BP (ca. 1000-300 yr cal BP). A significant age gap in coastal aggradation is present between ca. 5300 and 4400 yr BP (ca. 5600-4500 yr cal BP), and perhaps between ca 2000 and 1300 yr BP (ca. 1700-1000 yr cal BP). These can be linked to phases of local sea level fall and/or phases of sedimentary starvation and/or changes in drift transport which can have produced local coastal cannibalization. However, no conclusive data can be advanced. Data obtained from careful measurements of sea level markers represented by the top of marsh and fluvial terraces indicate lower values for the sea level estimation compared with the data set previously proposed for the area. This stigmatizes the fact that field-oriented works are still the priority in the Patagonia coast along with accurate age measurement, especially for obtaining the fundamental information we need for predicting the environmental impact, in these coastal areas, from accelerate sea level rise as effect of global warming.