Lawn Hill Crater refers to an impact structure (or astrobleme), the eroded remnant of a former impact crater, situated in northwestern Queensland, Australia. The site is marked by an 18 km diameter ring of
limestone hills. The origin of this circular feature was uncertain until the discovery of shatter cones and shocked quartz from uplifted rocks at the centre was reported in 1987.
The site is heavily eroded and it has been suggested that the original crater was slightly larger, at around 20 km diameter. The age of the impact structure is somewhat contentious, in the absence of any radiometric dating. The impact–shocked rocks at the centre of the site are early Mesoproterozoic in age, which gives an absolute maximum possible age for the impact. In the past it has been debated whether the limestones, which are of Middle Cambrian age (ca. 510 Ma) based on comparisons with nearby outcrops of marine
limestone in the Georgina Basin, were simply deposited in
the crater after its formation, or were actually deformed by the impact event. Depending on the differing points of view,
the crater may be of earlier Cambrian or Proterozoic age, or it could be of younger Paleozoic age. The most recent study concludes that the impact most likely happened just before or even during the early stages of deposition of the
limestone, suggesting an age of around 509–506 Ma.