Chapter 6 The Argentine continental shelf: morphology, sediments, processes and evolution since the Last Glacial Maximum

Abstract

The Argentine continental shelf is one of the largest and smoothest siliciclastic shelves in the world. Although it is largely emplaced in a passive continental margin, the southernmost regions are related to transcurrent and active margins respectively associated with the Malvinas Plateau and Scotia Arc. Sea-level fluctuations, sediment dynamics and climatic/oceanographic processes were the most important conditioning factors in the modelling of the shelf, with a minor influence from isostatic and tectonic factors that are more relevant in the southernmost regions. The shelf is shaped by diverse geomorphic features, among which the most significant are four sets of terraces genetically associated to sea-level stillstands during the post-glacial transgression; the final one occurred at around 11 ka and is associated with the Younger Dryas event. The Last Glacial Maximum (LGM) sedimentary sequence is composed of, on average, 5–15 m-thick terrigenous, siliciclastic, relict–palimpsest sands mainly sourced from the Andean region, with minor amounts of bioclast and gravels, resulting from the reworking of pre-transgressive coastal environments.

Evolution of the northern Argentine margin during the Cenozoic controlled by bottom current dynamics and gravitational processes

“…Thus the shallowest sedimentary sequences imaged in the working area are in agreement with the notion that sea level fluctuations, sediment dynamics and climatic/oceanographic processes are considered most important in the shaping of the shelf. Isostatic and tectonic factors have only a minor influence that is more relevant in the southernmost regions of the Argentine margin [ Violante et al ., ].…”

Chemical Weathering of Loess and Its Contribution to Global Alkalinity Fluxes to the Coastal Zone During the Last Glacial Maximum, Mid‐Holocene, and Present

“…Extensive loess deposits on the Arctic shelf were made available by Biryukov et al (1988). For most of the Black Sea, data of shelf loess deposits were made available in Ryan et al (1997) and for the Argentinian continental shelf by Violante et al (2014). Besides, data about loess deposits in the China Sea, on the shelves off West Africa, and in the Indian Ocean and Western Pacific (Figure 3) were made available by Li et al (2013) and references therein.…”

Quantifying Sources and Transport Pathways of Surface Sediments in the Gulf of San Jorge, Central Patagonia (Argentina)

“…47°S (Cape Tres Puntas; Figure 1b,e), an encroachment of the South Atlantic Ocean in the heart of southern South America. The bathymetry of the basin rapidly decreases to reach the 90 m isobath, which defines a large flat central region that covers most of the surface of the gulf and corresponds to the Patagonian outer shelf (Violante et al, 2014). The hydrodynamic and water mass origins in the gulf are related to the northward circulation on the shelf (Figure 1a; Palma et al, 2008), but the GSJ is also located at the limit of the influence of the Magellan Strait discharge flowing along the coast and entering the gulf in the southeastern sector at Cape Tres Puntas (Fernández et al, 2005).…”

“…The main suppliers of terrigenous materials to the Patagonian littoral are coastal erosion, rivers, and aeolian transport, as well as transportation and redistribution of sediments from the shelf by the prevailing northward-flowing Patagonian Current. Indeed, according to Pierce and Siegel (1979) and Gaiero et al (2003), the estimated contributions of coastal erosion, dust transport, and rivers to the terrigenous sedimentary supply transferred offshore are, respectively, 56%, 41%, and 3% (Violante et al, 2014). The weak proportion of sedimentary inputs to the continental shelf by the Patagonian rivers is explained by their present low flows and the low particulate loads in their downstream sectors (Gaiero et al, 2003;Kokot, 2004).…”