Subsidence Structures Associated with Subaerial Desiccation-Crack Piping and Their Role in Drainage Evolution on a Drained Proglacial Lake Bed: Hagavatn, Iceland

A range of subsidence structures associated with desiccation-crack piping are described from the drained proglacial lake bed of Hagavatn, Iceland. Subsurface drainage along desiccation cracks leads to the formation of small-scale subsidence structures. These subsidence structures include linear fissures, located along the limbs of desiccation cracks, and crater-like depressions that form at crack intersections. The controls on subsurface piping are discussed and the role of these subsidence structures in determining the pattern of surface drainage on the former lake bed is identified. Preservation potential of these sedimentary structure is considered to be high, given renewed lacustrine sedimentation. The potential for similar structures to be found in the geological record is considered likely, and consequently these structures may be of importance in the interpretation of crack networks in the geological record as being of subaerial as opposed to subaqueous origin.