Holocene coastal environments and processes in subantarctic/temperate cold Tierra del Fuego, Argentina-Chile

Abstract

Holocene coastal environments in the Tierra del Fuego archipelago in southernmost South America evolved in a temperate cold climate characterized by strong and persistent mid-latitude westerly winds, and under stable to falling relative sea level. Southern and western coasts are rocky, microtidal, and generally devoid of Holocene accretionary coastal landforms; they are young, having originated through flooding by the early Holocene. Northern and eastern coasts are lined by receding cliffs that supply abundant sediment to macro/mesotidal embayments lodging accretionary coastal landforms. Spit growth on the Atlantic shore played a major part in modifying the development of other landforms through barring the shoreline from wave attack. Sediment was mainly supplied from Pleistocene glacial deposits exposed at eroding headlands, and, more locally, obtained through cannibalization and from elevated Pleistocene beaches. In places, westerly winds combined with Atlantic swell to foster spit growth under high-energy wave power on both the bay and the ocean flanks, an unique occurrence. In addition, the westerlies caused widespread deflation on supratidal marshes and delivered fine-grained sediment inland and to the sea. Recent acceleration of glacio-eustatic rise is gradually changing the coastal zone to a condition of relative sea-level rise. The generally high and steep coastlines will not be greatly affected. A few gently-dipping lowlands might be flooded and biodiversity will be negatively affected.