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 a re described from the drained proglacial lake bed of Hagavatn, Iceland. Sub surface drainage along desiccation cracks leads to the formation of small-s cale subsidence structures. These subsidence structures include linear fiss ures, located along the limbs of desiccation cracks, and crater-like depres sions that form at crack intersections. The controls on subsurface piping a re discussed and the role of these subsidence structures in determining the pattern of surface drainage on the former lake bed is identified. Preserva tion potential of these sedimentary structure is considered to be high, giv en renewed lacustrine sedimentation. The potential for similar structures t o be found in the geological record is considered likely, and consequently these structures may be of importance in the interpretation of crack networ ks in the geological record as being of subaerial as opposed to subaqueous origin.