The last marine ingression in central Magellan Straits, southernmost Chile: geological and geochemical evidences

• Main Authors: BRAMBATI A, DEMURO, SANDRO
• Other Authors: Brambati, A, Demuro, Sandro
• Format: Conference Object
• Language: English
• Published: 2004
• Subjects: Sedimentology; Paleoclimatology; Holocene; Peri-antarctic area; Strait of Magellan; Antarctic; Antarc*
• Online Access: http://hdl.handle.net/11584/16526

During the last glacial cycle, glaciers drained north-eastward into the Strait of Magellan. The timing of the last advances has been ambiguous but the older dates of 16,590-15,800 up to 10,500 yr for deglaciation is known in the literature. This presentation focuses the Strait of Magellan, where after the last glacial cycle, the marine ingression is well defined. Along the coasts, located on the eastern Atlantic side of the Straits, it is possible to observe at least four orders of terraces, prevalently marine lying on a meso-tertiary sedimentary basement or on glacial and glacifluvial deposits, linked to the last Quaternary main glacial stages. The four main orders of terraced sequences have been mapped, described and dated using 14C. Because of there stratigraphic position and by radiocarbon dating, these four order terraces were referred to the Lower Holocene and connected to the isostasy rebound. The First, and oldest Order, was found regularly between altitudes of 18 and 25 metres. The Second Order, is distributed between 6 and 11 metres, and is mainly represented by fossiliferous gravel deposits; sands and silts are also present. It regularly covers most of the coastal stretch and extends in the backland. The age of formation of the marine deposits, by C14 dating, is on average between 6,000 and 7,000 years B.P. The Third Order is following strictly the present beach, between altitudes of 3 and 5 metres, at the foot of the Second Order terrace. It is made up of gravels and sands and refers preferably to a marine environment. At a slightly lower elevation, there is the Fourth Order marine terrace distribuited between 1.5 and 3 metres. All terraces, present well-preserved characteristics of paleobeach environments (berms, spits and ridges). The First Order terrace belongs to the palaeogeography, which was evolved during the first phase of the last deglaciation. The other orders are connected with subsequent stages of the last deglaciation, but the influences of the tectonics in their evolution cannot be ...