Insight on Mechanical Stratigraphy and Subsurface Interpretation

Abstract

Abstract A valid structural geologic interpretation should simultaneously honor available surface and subsurface data (e.g., well and seismic) to constrain structural geometry; ideally be restorable to an original unstrained condition – taking into account the possibility of three-dimensional (3-D) movement, volume loss, or volume gain; and incorporate structural styles known or expected for the mechanical stratigraphy and deformation conditions in the region. Incorporating what is known about the mechanical stratigraphy can provide crucial constraints on viable structural styles, for example, where faults are likely to cut across stratigraphy vs. where fault displacement is likely to be accommodated by alternative mechanisms (e.g., ductile flow or folding). Conversely, the structural style can often help to understand the mechanical stratigraphy, including the recognition of dominant competent or incompetent mechanical stratigraphic units. Using this approach provides the interpreter another set of constraints toward improving interpretations, testing hypotheses, and developing valid structural interpretations. Outcrop characterization provides insights into the influence of mechanical stratigraphy and structural position on seismic- and subseismic-scale deformation in the layers. Examples of extensional deformation in Cretaceous carbonate strata in central and west Texas illustrate the utility of considering how mechanical stratigraphy influences the development of different deformation styles, even where deformation conditions are otherwise similar.