Geological and geothermal mapping in Djúpavatn-Vigdísarvellir area, SW-Iceland

Abstract

Geological and hydrothermal mapping was carried out in the Djúpavatn–Vigdísarvellir area which is a part of the Krýsuvík-Trölladyngja geothermal area on the Reykjanes Peninsula, SW-Iceland. The bedrock consists mainly of Late Pleistocene hyaloclastites and interglacial lava flows and Holocene lavas. They are divided into 11 hyaloclastite units and 3 interglacial lava flows. The geological age of the volcanic field extends from Holocene, through the last glaciation, the last interglacial period, the 2nd last glaciation, the 2nd last interglacial period, the 3rd last glaciation, and the 3rd last interglacial period. The oldest bedrock units outcrop in the northeast part of the study area and are from the third last interglacial period and third last glaciation, while Holocene lava flows occur in the northwest and east sides of the study area. The Krýsuvík-Trölladyngja area has two main hyaloclastite ridges, with the valley between covered by Holocene lava flows. Two tephra layers were found in the soil section on top of the youngest lava, the earlier from Reykjanes AD 1226 and the latter from the Katla volcano dated from 1485. The tectonics of the study area is controlled by the regional tectonics of the Reykjanes Peninsula. The main structural features are NE-SW trending hyaloclastite ridges. Numerous NE-SW trending normal faults were mapped in the study area. The main geothermal manifestations occur in the southern part of the study area. The alteration ranges from slight alteration to intense and indicates relatively young geothermal activity, but all of it is extinct on surface within the study area.