HIGH RESOLUTION DEM AND PRECISE GPS ELEVATIONS FROM THE NORTHERN TIP OF MEJILLONES PENINSULA, NORTHERN CHILE: NEW IMPLICATIONS IN THE MORPHOTECTONIC EVOLUTION OF THE NEOGENE COASTAL TERRACE SEQUENCE

Mejillones Peninsula of northern Chile is located over the active subduction zone along the Pacific coast of South America. Its morphology exhibits a remarkably well preserved sequence of coastal terraces, a valuable source of information about the tectonic and climatic evolution in this segment of the Andes.

A set of 30, 000 –scale aerial photographs plus GPS ground elevation control points, have been put together in the generation of an orthomosaic, and the automatic extraction of a high resolution DEM. Detailed mapping of the terraces, and elevation data collected in the field are being utilized in the generation of a three-dimensional morphotectonic model of the peninsula.

More than 13 different levels were identified in the northern tip of the peninsula, whose elevations have been precisely measured utilizing the differential GPS technique. The east boundary of the northern tip, presents a sequence with narrow and discontinuous terraces, Some perturbations in their natural morphology, related to the activity in branches of Mejillones fault, can be seen in the older levels as well in the younger ones. A contrasting situation occurs in the western boundary, where the terraces are wider, continuous, and there is no sign of recent deformation in the sequence.

The collection of articulated mollusks, to be dated with Electron Spin Resonance technique (ESR), allows estimations of the age of the different levels and their correlation from side to side in the tip of the peninsula. Variations in uplift rates will be documented utilizing the age and precise elevation of the sequence. The DEM will be integrated to resolve the Pleistocene fault slip history of structures affecting the coastal terrace sequence.