A METHODOLOGY FOR STUDYING SUBSIDENCE VARIATIONS WITHIN A BASIN

Subsidence curves from over 100 locations in western Canada reveal that during Mesozoic times the subsidence history varied throughout the basin. In other words, a single subsidence curve, which provides a record of the vertical movement at a single point in a basin, is not representative of the subsidence history of the entire basin. Creating a large volume of subsidence curves with many existing software packages is often tedious because the user has little control over the input data. Additionally, the “black box” format of many programs limits which output data can be used.

Here we demonstrate how these problems were addressed with macros in a Microsoft Excel 2007 spreadsheet. A key advantage of this approach is that input data can be exported from other software applications and easily adjusted for use in the subsidence spreadsheet. The user can define the lithologies as well as the input variables for each lithology: porosity, density, and compaction coefficient. Rather than manually entering these parameters for each layer of each sediment column, the parameters are defined in master lists in the spreadsheet. These master lists can contain as many units and lithologies as the user needs.

Customized curves, such as subsidence curves and burial history curves can be generated in Microsoft Excel 2007. Furthermore, calculated values can be extracted from the spreadsheet and mapped to give a picture of how subsidence changes within a basin.