Ring and Dome Features, Possible and Probable Impact Structures

Circular drainage patterns, round lakes and oval depressions may provide hints of possible underlying ring or dome structures, requiring field tests or drilling where no outcrop occurs (Grieve RAF, Pilkington M, Aust Geol Surv J Aust Geol Geophys 16: 399-420, 1996; Glikson AY, Uysal IT, Earth-Sci Rev 125: 114-122, 2013). Structural domes and near-circular fold structures may initially be mistaken for impact structures, as are basins of approximately circular or slightly elongate pattern and plutonic domes such as oval granite intrusions, laccoliths and gabbro plugs. In orogenic belts, domes may be produced by compression and associated folding, including folding fold sets with different trends producing domes at the culminations of crossing anticlines. Diapirs are cored by relatively low-density rocks or magma, an example being granite domes rising in response to the gravity instability of the granitic magma relative to the denser country rocks. Circular drainage patterns, round lakes and oval depressions may provide hints of possible underlying ring or dome structures, requiring field tests or drilling where no outcrop occurs (Grieve RAF, Pilkington M, Aust Geol Surv J Aust Geol Geophys 16: 399-420, 1996; Glikson AY, Uysal IT, Earth-Sci Rev 125: 114-122, 2013). Structural domes and near-circular fold structures may initially be mistaken for impact structures, as are basins of approximately circular or slightly elongate pattern and plutonic domes such as oval granite intrusions, laccoliths and gabbro plugs. In orogenic belts domes may be produced by compression and associated folding, including folding fold sets with different trends producing domes at the culminations of crossing anticlines. Diapirs are cored by relatively low-density rocks or magma, an example being granite domes rising in response to the gravity instability of the granitic magma relative to the denser country rocks.