Abstract:

The Cretaceous Gabra Formation in the Fula Depression,Muglad basin,Sudan,can be classified into seven three-order sequences.Based on the seismic reflection parameters,internal reflection configuration and external shape,five types of seismic facies are identified on the seismic reflection profiles of the Abu Gabra Formation.They are chaotic facies,paralleling and sub-paralleling sheet facies,foreset wedge facies,foreset(wedge)-filling faceis,and onlap-filling faceis.These facies may be further subdivided into nine classes in terms of their amplitudes and continuities,i.e.(1)parallel sheet facies with strong amplitude and high continuity,(2)parallel sheet facies with medium-strong amplitude and moderate-high continuity(3)sub-parallel sheet facies with me-dium amplitude and moderate-poor continuity,(4)sub-parallel sheet facies with medium amplitude and moderate-high continuity,(5)wedge-filling facies with medium-strong amplitude and moderate continuity,(6)wedge-fil-ling facies with medium amplitude and moderate-poor continuity,(7)onlap-filling facies with medium amplitude and moderate-poor continuity,(8)foreset-wedge facies with medium amplitude and moderate continuity,and(9)chaotic facies with medium amplitude and poor continuity.These seismic facies distinguish from one another ho-rizontally but show hereditability and differentiation over vertical sections.The spacial distribution of the seismic facies corresponds well with the structure and tectonic evolution of Fula depression.

Key words: sequence stratigraghy, seismic facies, Abu Gabra Formation, Fula Depression, Sudan