DISCRIMINANT ANALYSIS OF ELEMENTAL DATA TO DIFFERENTIATE FORMATIONS OF LIKE FACIES VERTICALLY ACROSS AN UNCONFORMITY AND LATERALLY ACROSS A PALEOTOPOGRAPHIC DIVIDE

摘要

Distinguishing different lithostratigraphic formations that are in contact with each other can be problematic when they are of like facies, appearance, and provenance. For example, formations of like facies that are vertically separated by a subtle unconformable surface are difficult to distinguish, especially if multiple candidate surfaces exist. Similarly, time-equivalent formations of like facies that were separated into distinct subbasins by a topographic divide may also be challenging to distinguish. In this study, formations of this nature were discriminated using statistical discriminant analysis of X-ray fluorescence (XRF) elemental data that included both mobile and immobile elements. This discrimination has important consequences for stratigraphic analysis. For example, accurate placement of an unconformable surface within a stratal succession is important because it affects the interpreted thickness of units and sequences in contact with that surface. Unit thickness influences the interpretation of basin subsidence and its timing, depositional style of basin fill, paleotopography, and diagenesis.