CHARACTERISTICS OF THE CAMPANIAN TRANSGRE SSION ONTO THE HAUSHI-HUQF BASEMENT (EAST-OMAN) STRATIGRAPHY, GEODYNAMIC SETTING AND PALEOENVIRONMENTS

Stratigraphic and palaeoecologic studies of the Cretaceous formations in eastern central Oman (Haushi-Huqf area), recently made to support g eological mapping, have enabled to determine or refine the age and pal aeoenvironments of the sediments of the Campanian transgresion (Aruma Group) unconformably overlying the Cenomanian Natih Formation or any o ther older formation up to the Proterozoic palaeohigh. Corresponding t o one of the highest sea-level of the Mesozoic, this transgression pro ceeded in several steps over this region, with facies diversification, strongly controlled by the proximity of emerged areas. During the fir st step, was built the early Campanian shallow-marine rudist-rich shel f of the Samhan Formation; this is roughly contemporaneous to the empl acement of the Hawasina and Samail nappes over northern Oman. The seco nd step, starting in the << middle >> Campanian, indicates a more impo rtant transgression with sedimentation of chalky lithofacies in a rela tively deep basin (Fiqa Formation) ; these sediments overly a major fl ooding surface, separating both formations with a prominant discontinu ity, reflecting active subsidence around the Haushi-Huqf massif; this surface and the overlying Fiqa facies succession suggest a drowning of the platform due to a tectonic event related to the geodynamic evolut ion of the Oman Mountains foreland basin (i.e. Suneynah foreland) afte r the nappes emplacement.