| Summary: | This study demonstrates how to make and use a three dimensional model in GSI3D, based on well data from the Geological Survey of Sweden’s well archive. The objective is to determine if it is possible to show a supposed fault scarp, the Bollnäs fault, in the bedrock and the valley morphology in a 3D model based on the data available. During the last ice age, the land surface under the ice was depressed by several hundred meters. As the last ice sheet retreated, land uplift began and faulting occurred. These glacially-induced faults are dated to late or post glacial times since they are cutting post glacial sediments. The same goes for the Bollnäs fault. The scarp is seen through airborne light detecting and ranging, LiDAR, cutting surficial sediments but never outcrops in the bedrock. After examining and validating the well data in the mapped area, 430 of 478 wells were used to build the model, giving a 3D model of the surficial deposits and the bedrock surface. In the model, the scarp cannot be seen in the bedrock, nor in the deposits nor in the valley morphology. Exporting the model to Arc GIS as a digital terrain model, a DTM, as a raster, shows that with the amount of data available a fair pixel resolution would be 150 m2. With that resolution detailed landforms like fault scarps would not appear. The conclusion is that the amount of data is to low to accurately model small-scale features. These findings aligning with earlier research on 3D models.
|
|---|