The purpose of this page is to prepare for the chronostratigraphic exercise that follows. The page is based on a movie of a 3D rendered Sedpak simulation. The simulation provides the cross sections of the evolving sedimentary geometries. Added to the simulation output is a interpretive 3D perspective of the depositional surfaces responding to changes in relative sea level. Without the movie, the information available is overwhelming. The movie is intended to give a better understanding of the depositional settings featured in the simulation. The movie shows how and why sequence stratigraphic interpretative analysis uses the subdividing "surfaces" enveloping discrete sediment body geometries of the sedimentary section. The movie was built by first reversing the order of deposition by back-stripping the geometries from oldest to youngest and then reassembling the sedimentary strata in order of accumulation. The subdividing surfaces provide the framework to the lithofacies geometry enabling the interpretation and rebuilding of the evolving character of depositional setting. The simulation and so movie track how a hypothetical siliciclastic clastic margin setting would respond to varying rates of shoreline progradation, sea level, and base level change. So the output is expressed as a series of block diagrams with a three dimensional perspective and involves sand and shale deposition. History of Relative Sea Level The simulation traces rise in relative sea level, a lowstand of relative sea level, a transgression of relative sea level, a highstand, a relative fall in sea level, a further rise of relative sea level, and finally highstand of relative sea level, and a fall of relative sea level. The sailing boat provides the viewer with a sense of where the elevation of the sea's surface as a function of time.
Tectonic History It was assumed that the accommodation available in the basin for the sedimentary fill was the combined product of a history of subsidence and eustasy. Thus, for this reason, all the changes in sea level shown on the diagram are relative changes.
Eustatic History The simulation traces a fall in sea level, lowstand, transgression, highstand, fall, a further rise in sea level and a final highstand. This can be tracked in the graph to the right of the simulation and the red triangle tracks the position of the sea. This matches the movement of the sea surface in the 3D perspective diagram. The sailing boat is provided to help show the position of the sea's surface.
Sedimentation The percentage of sand and shale initially coming from the left and finally from the right is shown on the graphical display to the left. The Sedpak simulation varies the relative percentage of these sediments as a function of time and this relative amount can be seen when matched to the position of the sea level (the red triangle). In Sedpak, as in nature, the carbonates accumulate more rapidly in shallow water and more slowly as the water depth increases. Carbonate rates tend to be higher where the rates of clastic input are low and slow to zero where the clastic inputs are high.