Practical and efficient three-dimensional structural restoration using an adaptation of the GeoChron model

We document a novel approach to balanced three-dimensional structural restoration based on an adaptation of the GeoChron model. Conventionally, the GeoChron model defines a transformation of a geological model to a flattened space (U-V-T), with paleogeographic coordinates defined by the horizontal axes (U-V) and geologic time on the vertical axis (T). In our new balanced structural restoration scheme, the complete stratigraphy is restored using a transformation constrained only by the datum horizon. Scaling the vertical "T" axis to depth in a manner that preserves volume or layer thickness results in a geometric restoration that approximately minimizes strain globally. This restoration provides a geometrically plausible representation of the geologic structure at the time when the datum horizon was deposited. Restoration is independent of mechanical rock properties and is thus most applicable to regions in which mechanical rock properties are approximately homogeneous. Restoration kinematics may be constrained by growth strata if present. We validate the method with kinematic forward models and a laboratory sandbox model and apply it to two natural examples to demonstrate its capabilities for model validation and palinspastic restoration. We identify four criteria for assessing the validity of a structural model using the results of restoration: (1) anomalous fault throw, (2) timing of fault activity, (3) fault compliance, and (4) restoration strain. Analysis of the sandbox results and limitations of volume conservation derived from uncertainties in compaction states suggest accuracy of the method to be in the 5%-20% range.