Seismic geomorphology of Palaeozoic collapse f atures in the Fort Worth Basin (USA)

Abstract: Modem multi-trace geometric attributes produce three-dimensional volumes that can facilitate the recognition of karst geomorphology by avoiding the need to pre-interpret irregular hori-zons and by enhancing subseismic lateral variations in reflectivity. These geometric attributes include the well-established coherence t chnology, coupled with recent developments in pectrally limited esti-mates of volumetric curvature. Coherence measures lateral changes i waveform, and as such, is often sensitive to joints, small faults, sinkholes and collapse features. The many components of reflector curvature, including themost negative, most positive, Gaussian curvature nd related shape indices (e.g. valleys, saddles, domes), are complimentary to coherence measures. Short wavelength estimates of curvature will illuminate small-scale lineaments while longer wavelength estimates of curvature illuminate more subtle flexures and compaction features. We show the results of app ying a variety of multi-trace geometric attributes to a three-dimensional seismic volume from the Fort Worth Basin, where a collapse system extends vertically some 800m from the Ordovician Ellenburger carbonates through the dominantly siliciclastic Mississippian- Pennsylvanian interval. The collapse features in our data set appear as rounded, sinkhole-like appearances on time and horizon slices in the Pennsylvanian Marble Falls Limestones and the Ellenburger horizon displays features that can b