Morfología y estructura del basamento precuaternario de la Caleta Española, Península Hurd, Isla Livingston

Abstract

In the Caleta Española (surroundings of the Spanish station Juan Carlos I, Hurd Peninsula, Livingston Island, Western Antarctica) are located several Holocene raised beaches, that are developed on Quaternary sediments. Below these sediments there is a basement of Permo-Triassic age, the Miers-Bluff formation. In order to know the characteristics of the Quaternary sediments, their thickness and the geometry of the basement under the raised beaches, as well as the possible presence of permafrost, this area has been studied by means of geophysical methods (geoelectric) and the main structural features has been mapped. For establishing the underground resistivity characteristics 12 vertical electric soundings have been made, with a georesistivimeter with a sensibility of 0.1 mA and 0.1 mV provided with digital lecture and with automatic polarity commutation. Has been used the Schlumberger quadripole array for each sounding. The vertical electric soundings have been modelised by means of an automatic inversion procedure and represented in five longitudinal and transversal profiles. Based on the geoelectric soundings a map of isobaths of the bedrock has been made. The most important feature is the presence of the ESE-WNW trending buried trough of approximately -72 m of depth below the present sea level. This morphology of the pre-Quaternary bedrock is probably related with a small pull-apart structure and with erosion (glacial overexcavation). This trough is now infilled by Quaternary sediments, mainly of marine and glacial origin. The existence of this structure seems to be coherent with the results of the gravimetric and magnetic studies carried out in the area, that show a negative anomaly over this small basin.