Sediment input from fluvial sources and cliff erosion to the continental shelf of Argentina

Abstract

The coasts of southern Buenos Aires, Patagonia and Tierra del Fuego are dominated by cliff erosion. Mean rates of cliff retreat are estimated to be about 0.5-0.6 m/year by comparing old photographs with modern satellite images. Considering the height of the Patagonian and Fueguian cliffs (70 to 120 m), the volume of sediment eroded from these cliffs exceeded the volumes provided by the erosion of the cliffs of Buenos Aires (10 to 20 m height). These erosion rates support an estimated delivery of 217 million tons of sediment per year to the continental shelf, exceeding significantly the 22 millions of tons/year transported by the larger Patagonian rivers Negro and Colorado. However, the contribution of these rivers has decreased since the Late Pleistocene changes in the direction of transport of some watersheds. The Chubut and Chico de Santa Cruz rivers suffered reductions of 21-24% in their watershed areas, resulting in reductions of about 33-34% in the volume of water transported to the Atlantic Ocean per year. As the amount of sediment delivered to the Argentine continental shelf by cliff erosion is higher than the fluvial transport, it should be also considered in the balance of beaches fed by longshore transport.Keywords: cliff erosion, sediment supply, drainage reversal, Patagonia, Buenos Aires RESUMO Fornecimento sedimentar de origem fluvial e da erosão costeira à plataforma continental Argentina O litoral de Buenos Aires, Patagónia e Terra del Fuego é dominado pela erosão de falésias marinhas. As taxas de medias de recuo foram estimados em 0,5-0,6 m/ano, com base na comparação de fotografias aéreas antigas com imagens satelitárias modernas. Considerando a altura das falésias patagónicas e fueguinas (70 a 120 m), o volume de sedimento erodido supera os volumes que provêm das falésias de Buenos Aires (10 a 20 m). Estas taxas de erosão permitiram estimar um aporte de

Avulsion at a drift-dominated mesotidal estuary: The Chubut River outlet, Patagonia, Argentina

“…Location of the Chubut River basin, and digital terrain model of the lower valley. The area of the watershed diminished since the Puelo River captured a significant portion (grey dark area) towards the Pacific Ocean (modified after Isla and Cortizo, 2014). Inset at the river inlet is in detail in Fig.…”

“…The end of the Last Glaciation caused the blocking of the Pleistocene drainage direction. Much of its former recharge area is today flowing to the Pacific Ocean via the Puelo River (Isla and Cortizo, 2014;Fig. 1).…”

“…The moraines left by the Last Glaciation (Oxygen Isotopic Stage 2, Wisconsin in North America) dammed the original pathways to the Atlantic Ocean, reversing their drainage direction towards the Pacific Ocean (Quensel, 1910;Isla and Cortizo, 2014). Some watersheds, as the Chubut River, diminished significantly during the Pleistocene-Holocene transition (Fig.…”

“…1 Their snow recharge areas at the Andes are today flowing towards the Pacific Ocean (Martínez and Coronato, 2008). These reductions in the drainage areas of the Chubut River were about 24% in relation to the Upper Pleistocene watersheds, and signified reductions between 32% in terms of volume discharged per year (Isla and Cortizo, 2014). In terms of the transport of heavy metals, the Chubut River is one of the rivers which transport lesser loads of Fe, Cu, Pb, Co, Mn and Ni to the South Atlantic Ocean (Gaiero et al, 2003).…”

Shoreline Detection using Optical Remote Sensing: A Review

“…The dune crest is the highest elevation peak, where the slope changes sign from positive (landward facing) to negative (seaward facing) [23]. [18,[22][23][24] Cliffs and backed beach Bluff top, cliff top, top of the cliff The bluff top (cliff top) refers to the top edge of the cliff [14,[25][26][27][28][29] Base of the bluff, cliff toe, bluff toe…”