Changes of palaeozonation patterns within Miocene coral reefs, Gebel Abu Shaar, Gulf of Suez, Egypt



The Gebel Abu Shaar represents the southern end of a tilted fault-block consisting of Precambrian basement upon which a mixed siliciclastic-carbonate platform developed during mid-Miocene time. The Miocene sequence contains coral reefs and reef facies. Palaeozonation patterns of the Miocene coral reefs were assessed on the well-preserved outcrops of the Gebel Abu Shaar by recording both qualitative and quantitative data of reef-building assemblages. The various patterns of palaeozonation were analysed and compared at different spatial and temporal scales, including both within-reef and between-reef variations. The palaeozonal changes recorded within these fossil reefs are similar to those described from present-day living coral reefs and involve contraction or extension, fusion or splitting, replacement and omission of reef-builder zones. Depending on the scale concerned, the nature and importance of changes affecting the palaeozonation pattern vary. Spatial variations of the palaeozonal pattern appear mainly controlled by local changes of ecological conditions while temporal variations are related to regional and global environmental changes.