Existing sequence stratigraphic models have largely been developed from passive margin settings where variations in accommodation, sediment supply and facies transitions occur over tens to hundreds of kilometres. In contrast, during active phases of basin evolution, variability in sediment supply and accommodation occur on a kilometre length-scale. In particular, marked variations in accommodation development occur along the length of fault segments due to variations in fault displacement from a maximum at fault segment centres to a minimum at fault tips. Implications for sequence development are great, with pronounced variations occurring in facies stacking patterns both along strike and dip in contemporaneous depositional systems. Furthermore, the progressive lateral and vertical propagation and linkage of fault segments during basin evolution results in progressive spatial and temporal variations in basin physiography and profoundly influences sequence development.

We describe a case example of stratal stacking patterns which developed within the rift-initiation Nukhul Formation of the Suez Rift during normal fault propagation and linkage. Detailed analysis of facies, palaeocurrent data, synsedimentary faults and correlation of marine flooding surfaces reveal a direct relationship between changes in basin physiography due to seismicity and spatial and temporal changes in facies stacking patterns. These data indicate that i) Flooding surfaces are the key to correlation, facies prediction and understanding the structural/sedimentary evolution of rift basins ii) Sequence stratigraphical models in extensional basins must address fault growth and linkage iii) Surfaces of erosional truncation (sequence boundaries) and system tracts are of limited use in correlation and facies prediction in extensional settings.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah