Three-dimensional configuration of a pull-apart basin from high-resolution magnetotelluric profiling: Eumsung Basin (Cretaceous), Korea

A new high-resolution magnetotelluric (MT) survey in a pull-apart basin (Cretaceous Eumsung Basin, Korea) provides integrated images of internal architecture. Two cross-basinal MT profiles show an asymmetric form with a subbasin in the southeastern part and these characteristics are reflected well in paleoflow directions and facies transitions of the surface lithofacies units. The results suggest that the basin experienced pull-apart opening with rapid subsidence of the central blocks. Combined with the outcrop data on asymmetric lithofacies distribution, facies transitions, and paleoflow directions of the alluvio-lacustrine systems, the MT data help explain basin-fill processes during basin formation. The high-frequency MT technique is a useful substitute for the costly burden of a seismic-reflection survey.