Sammendrag
A succession of crater infill sediments is preserved within the Ritland impact structure. Ritland is good example of a small depositional basin where a range of processes from debris flows to turbiditic currents and finally suspension fall-out took place within a very restricted area. Immediately after impact slumps/slides, and mass flows dominated, later to be replaced by running water activities in much calmer basin environment, like fine-grained sedimentation. The sedimentary successions of this small crater, which most likely was a terrestrial impact structure, reveal a shifting depositional environment. Just after the impact accommodation space for sediments was created in an extremely short period. The postimpact breccias covering the crater floor were most likely deposited by rock avalanches, triggered by collapse of crater rim. Breccia deposits interfingering with melt rocks (suevite)
and ejecta, which were formed and deposited seconds after impact. The overlying lacustrine sediments, around the center of the crater, suggesting that a temporary lake was present at some time after the impact. Probably groundwater seepage, through the crushed basement,
filled the structure to some level and initiated sediment deposition in water reservoir. The succeeding conglomeratic and sandy sequence characterizes local thickness variation. This sequence was deposited by various catastrophic sediment gravity flows, such as turbidity
currents, debris flows, slides and slumps, likely triggered by the resurging water, during the Cambrian marine transgression. The resurging water breached the crater rim, which caused its collapse, producing series of rock avalanches. The crater was finally covered by sea and previous rapid depositional procceses switched into deep water sedimentation processes probably not very deep – epicontinental sea. Shales covering gravity flow deposits represent the reestablishment of quiet conditions.