Adding the missing third and fourth dimensions to trajectory analysis in carbonate systems

Abstract

AbstractWe developed a seismic geomorphology‐based procedure to enhance traditional trajectory analysis with the ability to visualize and quantify lateral variability along carbonate prograding‐margin types (ramps and rimmed shelves) in 3D and 4D. This quantitative approach analysed the shelf break geometric evolution of the Oligo‐Miocene carbonate clinoform system in the Browse Basin and delineated the feedback between antecedent topography and carbonate system response as controlling factor on shelf break rugosity. Our geometrical analysis identified a systematic shift in the large‐scale average shelf break strike direction over a transect of 10 km from 62° to 55° in the Oligo‐Miocene interval of the Browse Basin, which is likely controlled by far‐field allogenic forcing from the Timor Trough collision zone. Plotting of 3D shelf break trajectories represents a convenient way to visualize the lateral variability in shelf break evolution. Shelf break trajectories that indicate contemporaneous along‐strike progradation and retrogradation correlate with phases of autogenic slope system re‐organization and may be a proxy for morphological stability of the shelf break. Shelf break rugosity and shelf break trajectory rugosity are not inherited parameters and antecedent topography does not dictate long‐term differential movement of the shelf margin through successive depositional sequences. The autogenic carbonate system response to antecedent topography smooths high‐rugosity areas by filling accommodation and maintains a relatively constant shelf break rugosity of ~150 m. Color‐coding of the vertical component in the shelf break trajectory captures the creation and filling of accommodation, and highlights areas of the transect that are likely to yield inconsistent 2D sequence stratigraphic interpretations.