The Impact of Fold and Fault Development on Sequence Variability
Rob L. Gawthorpe and Peter Talling
Existing models of clastic sequence stratigraphy are largely based around two-dimensional dip-profiles in which predictable stacking patterns and key stratal surfaces are related to the interplay of i) rate of accommodation development, and ii) rate of sediment supply. Within active phases of basin evolution, rates of subsidence/uplift and deformation around developing faults and folds exert a major influence on accommodation development, basin physiography, sediment sources and sediment transport pathways.
Rates of uplift and subsidence in the vicinity of active faults and folds in extensional, compressional and strike-slip settings commonly range from 0.5 to 5 m ka-1. These rates have a significant effect on relative sea-level change (accommodation development) and show marked spatial changes over the length-scales of major fault segments (commonly in the range of 20-50 km). Thus along-strike as well as dip-oriented variations in sequence development may be pronounced. For example, spatial variations in accommodation create contrasting facies stacking patterns (systems tracts) in contemporaneous depositional systems. Furthermore, the high rates of tectonic uplift or subsidence associated with developing faults and folds may be sufficient to reverse the trend of regional base-level change, such that key stratal surfaces (e.g. sequence boundaries) may be of only local extent.
An understanding of the three-dimensional subsidence and uplift patterns within tectonically active phases of basin evolution is crucial for using sequence stratigraphy in a predictive way in exploration.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California