Visualization of Angular Unconformities and Tectonic Angular Discordance Measurement Constraints by Structural Geometrical Flattening: Case Studies in the Permian (California), Grand Canyon (Arizona), Chad Basin (Nigeria), Algarve Basin (Iberian Peninsula), and the Aegean Sea Basin (Turkey)

摘要

Geometrical flattening of stratigraphic data (seismic data, outcrop data, and interpreted well sections) is often practiced within a sequence stratigraphic framework with an emphasis on the chronostratigraphic order of sequence tracts. The representation of geological data within a chronostratigraphic framework reveals significant features such as non-depositional or erosional features (unconformities and condensed sections) that may not be obvious in the original domain. Angular unconformities represent time-significant surfaces formed when an older rock unit is tilted and truncated and a younger rock unit is deposited on top of it; they present a noteworthy situation where the older rock unit may be composed of several sequence tracts, simultaneously separated from the younger rock unit by a common time-significant interface. This implies that chronostratigraphic interpretation can be applied across this interface by geometrically flattening the rock units. We apply geometrical flattening using newly developed software: WheelerLab. We examine case studies in the Permian Strata (California), the Grand Canyon (Arizona), the Chad Basin (Nigeria), the Algarve Basin (Iberian Peninsula), and the Aegean Sea Basin (Turkey). Results show that the angular unconformities are represented as angular shaped hiatuses in the chronostratigraphic section containing an acute angle less than or equal to the total tectonic angular rotation (sum of angular discordance and dip angle).