When the Horizon Stack is computed directly from the Geo-Model, it is not possible to choose the horizons that will make up the Horizon Stack. The user can only choose an interval, the number of horizons and the attribute(s) to map.
Nevertheless, the user can choose all the horizons of the Horizon Stack if it is computed from the Sequence Stratigraphy toolbar (available in the Advanced Interpretation add-on module), using the New Horizon Stack from Sequence tool. In that case, the user can define the limits of the sequences within which the Horizon Stack will be created.
To save or extract a specific horizon from a Horizon Stack, the user has to right click on the top bar of the Horizon Stack viewer and select the option called Create Horizon(s). By default, PaleoScan will save and extract the currently displayed horizon, but a top, a bottom and a step can also be defined to save and extract a set of single horizons.