Tectonic Signatures in Stratigraphy: What Are They, and How Do We Best Apply Them?

Aschoff, Jennifer L.¹, Ron J. Steel¹ (1) University of Texas at Austin, Austin, TX

Tectonic signatures are characteristics or aspects of the stratigraphic record that can be used to infer the nature and relative timing of tectonics. These signatures are the fundamental building blocks for a wide array of geologic interpretations in basin evolution, and plate tectonic and paleogeographic reconstructions. Previously-used tectonic signatures include growth strata, onlapping/offlapping stratigraphic patterns, thickness trends, detrital composition, lithofacies distribution, paleoflow changes and vertical stratigraphic stacking patterns. Understanding the context in which these tectonic signatures are best applied, as well as their limitations, are important to reduce the uncertainty associated with interpretations of structural geology and tectonics. However, the practical utility and limitations of commonly-used tectonic signatures in different datasets and geologic settings has not been thoroughly addressed despite widespread application of these signatures. Here, we provide examples of the application of a variety of tectonic signatures, and examine the strengths and limitations of signatures, and suites of signatures. Our discussion includes signatures that are frequently used as well as less-frequently used signatures that have limited, yet unexplored potential. We conclude that the best signatures of structural development and tectonics are growth strata, ‘outsize' sequences, thickness trends, lithofacies trends, grainsize and detrital composition changes. However, we emphasize that tectonic signatures are best used as complete suites of criteria; no one criterion should be used to infer syntectonic deposition. Clear limitations of these key tectonic signatures are 1) poor or cryptic development of signatures in structure-distal regions, 2) time-lag between the development of certain signatures and the tectonic event.