In OpendTect-SSIS, a systems tract interpretation can be created. The created chronostratigraphy can be setup into systems tract by selecting/creating a suitable depositional sequence model from interpretation setup window. It is possible to make more than one interpretation for each Chrono Stratigraphy.
The interpretation of systems tract can be done interactively. To do that, select the chronostratigraphy from SSIS menu. Add the chronostratigraphy display in the tree. Then from SSIS menu select Interpretation > New/Edit.
The pop up window is the interpretation setup window of SSIS. In this window, on the right. you will see a chronostratigraphy slider and on left the pictorial representation of sequence stratigraphic interpretations. In the same window, an interpretation menu is available to save/open the interpretations. To create new interpretation, press Setup button to select/define the depositional sequence model. By default, there are five different standard depositional sequence models already available in the setup. You can either select any one of them or press Add model in the Systems tract setup window. In latter case, type names of systems tract and corresponding colors. You can also remove the user defined models from this window.
After the selection of Depostional sequence model, move either the top or bottom of the chronoslider and view the results of displayed chronostratigraphy on the section. It may be noted that chronoslider will only available in the interpretation window when it is inserted and displayed in the tree element (inline/crossline).
By fixing the top/bottom at appropriate relative geological time, the surface at top/bottom can be inserted by pressing insert button in the same window. It will appear in the right panel (grey area) as un assigned stratigraphic surface. You might note that the relative change in base level is plotted according to the depositional sequence model. Right click within the grey area below the newly inserted stratigraphic surface. In the pop up tree, you will see four options:
Assign Systems Tract: It may be noted that each depositional model has its own systems tract definition. So, if you have selected depositional model IV, the corresponding system tracts that you can assign will be listed as above.
Edit Boundaries: If you are not satisfied with inserted stratigraphic surfaces for system tracts, select edit boundaries option from the tree. On right panel, you can move the chrono-slider to new positions after you are done, press Set button or Cancel edit. The changes can be seen on right panel if any change is made.
Show Thickness Map: This will show the time thickness variations.
Set Absolute Age: The geological absolute age (My) to the any stratigraphic boundaries can be set here. In the next pop up window mention absolute age for top and bottom of the systems tract.
A stratigraphic surface can be saved as an output surface as well. Either right click on the stratigraphic surface name or at dots of base level curve or at numeric values of absolute age (if defined).
Select the area and write the name of output surface. This output surface can be displayed latter on in the Horizon tree.
You can also save all surfaces by pressing Save all surfaces button.
Once you are satisfied with the interpretation, save it or press the "Clear" button to redo the interpretation.
