Tectonic Processes along the South America Coastline Derived from Quaternary Marine Terraces

Abstract

South America is overriding the Nazca, Antarctic, and Cocos plates, and at the same time is moving along the Caribbean and Scotia plates. Quaternary sea-level highstands are ideal benchmarks to estimate tectonic uplifts considering altitude differences along the coast. The Sangamonian highstand, corresponding to the Marine Isotopic Stage 5, is the most helpful indicator for these purposes as it is more easily preserved and spanning a record of 120,000 years. The Mid-Holocene highstand leads to errors assigned to tidal-range variations, estuarine floods, and meteorological effects; however, its maximum altitudes could confirm faster uplifting rates. The major uplifting trends were estimated in relation to the subduction of seismic or aseismic ridges along the Pacific Ocean coast. The Quaternary uplifted terraces of the Atlantic coast at Patagonia were explained by the decreasing uplift induced by the subduction of the Chile Ridge, and related to a very modern volcanic field.