Complex structural features recognized in the basement complex in the Delaware City area in northern Delaware show that intense tectonic deformations affected this area sometime during its geologic history. The main feature is a graben that trends approximately N. 25° E. diagonally through the area. The graben was broken by other northeast-trending normal faults. The relatively uplifted marginal blocks on both sides of the graben were also cut by normal faults into a secondary graben in the northwestern part of the area and a set of normal faults in the southeastern part of the area. Similar structural features may exist in the basement complex in other parts of Delaware and the surrounding Coastal Plain.