Adding the missing third and fourth dimensions to trajectory analysis in carbonate systems
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AbstractWe developed a seismic geomorphologybased procedure to enhance traditional trajectory analysis with the ability to visualize and quantify lateral variability along carbonate progradingmargin types (ramps and rimmed shelves) in 3D and 4D. This quantitative approach analysed the shelf break geometric evolution of the OligoMiocene 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 largescale average shelf break strike direction over a transect of 10km from 62 to 55 in the OligoMiocene interval of the Browse Basin, which is likely controlled by farfield 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 alongstrike progradation and retrogradation correlate with phases of autogenic slope system reorganization 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 longterm differential movement of the shelf margin through successive depositional sequences. The autogenic carbonate system response to antecedent topography smooths highrugosity areas by filling accommodation and maintains a relatively constant shelf break rugosity of ~150m. Colorcoding 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.
