The flood of the Beagle Valley (11,000 YR B.P.), Tierra del Fuego

Abstract

The Beagle Channel connects the Pacific and Atlantic oceans. It is a deep basin (up to 200 m depth) separated from the Atlantic and Pacific oceans by shallow sills (30 m depth). The Beagle Channel is located at the active seismotectonic setting of the Fuegian Andes (Scotia Plate Domain). It is a tectonic valley (5 km wide) that was completely covered by ice during the Last Glaciation. It has a microtidal range and an indented rocky shoreline, where pocket gravel beaches develop in the embayments. Holocene raised beaches can be recognized in many places along the channel and their elevations vary considera- bly, reaching maximum elevations of 10 m above the present counterpart at ages of 6,000 yr B.P. The estimated average tectonic uplift is 1.3 mm/yr for this period. After the Last Glaciation, glaciofluvial, glaciolacustrine and peat bog environments developed in the basin. The Beagle valley was rapidly flooded by the sea immediately after the Younger Dryas, 11,000 yr B.P. when the sea level transgressed the water divides and boundaries of the basin of Paso Mackinlay (eastward), Murray Channel (southward), Beagle Channel northwestern and southwestern branches. Nowadays, these topographic sills are approximately 30 m deep. Key