<正> Apatite Fission-Track Analysis(AFTA)is emerging as an important new tool for ther-mal history analysis in sedimentary basins.At temperatures between approximately 20℃ and150℃ over times of the order of 1 to 100 million years,fission tracks in apatite are an-nealed.This is due to a rearrangement of the damage present in unetched tracks,with theresult that less of a track is etchable than in fresh,newly created tracks.Because of this,thelength of an etched fission track reduces with increasing annealing,and in turn,the track den-sity(and hence the fission-track age) is also decreased.In selected boreholes in the OtwayBasin,southeastern Australia,apatites from the Otway Group show reduction in confinedfission-track length and apparent fission-track age,in a fashion characteristic of a simple ther-mal history in which samples are at or near their maximum temperatures at the present day.Track lengths show a steady decrease from lengths of approximately 15μm in outcrop ornear surface samples,to zero at abo
