Geological controls on seismic sequence resolution

Abstract

A seismic sequence analysis of the Canterbury basin, eastern South Island of New Zealand, has illustrated the roles of subsidence, sediment supply, and current activity as controls on sequence resolution and architecture during basin evolution. The rates of sediment supply and subsidence determine the background depositional regime (transgressive or regressive),and effectively determine the frequency response of the continental margin sedimentary section to input signals with a broad range of frequencies, including eustasy. A regressive (progradational) depositional regime and minimal current erosion favor the preservation of high-frequency sequences, particularly at fourth-order level. Under less favorable conditions, the record of sequences is incomplete or ambiguous. Such frequency response characteristics must be considered when inverting sequence records to derive the frequency of the input cyclicity, and when making global comparisons of regional sequence stratigraphic studies. Clastic basins with simple subsidence histories and uniform or increasing rates of sediment supply develop from a transgressive phase, characterized by ramplike major sequence boundaries, to a mature, progradational shelf phase with clinoform sequences and optimum sequence resolution. The mature phase constitutes the preferred setting for sequence stratigraphic analyses.