Erosional history of the Karkonosze Granite Massif – constraints from adjacent sedimentary basins and thermochronology

Abstract

The long-term erosional history of the Karkonosze Granite Massif is revised and reconstructed using different sources of information, including the sedimentary record of adjacent basins, previously published low-temperature thermochronological data and geomorphic features. Although the evidence is still incomplete, this work has identified a number of intervals, of unequal duration, characterized by different denudation regimes and rates. Several major phases of rapid exhumation are inferred – in the Permian and the Early Triassic as seen in the sedimentary record, and in the Late Cretaceous as shown by both the thermochronological and sedimentary records. Neotectonic uplift of the Karkonosze Mts. in the late Cenozoic is not recorded in the thermochronological record and there is no evidence of any accelerated denudation close to the massif. Apatite fission track data show that >~3.6 km of rock must have been eroded since the Turonian, while the results of zircon (U-Th)/He analysis suggest that in places erosion of >~6 km of rock must have taken place. This picture differs from previous estimates of denudation which suggested that only 2–2.5 km has been eroded from the axial part of the Karkonosze dome since the exposure of granite batholith in the Permian.