Growth patterns of deep-sea fans revisited: Turbidite-system morphology in confined basins, examples from the California Borderland

This study characterizes growth and morphologies of turbidite systems in confined receiving basins of the California Borderland. Morphologies were quantified according to volume, area, maximum thickness, length, and width using an extensive grid of seismic-reflection data. Turbidite systems that were supplied sufficient sediment to be confined by their basin margins were unable to areally expand and, as a result, subsequent turbidite deposition thickened the systems. Conversely, insufficient volumes of sediment to extend systems to their receiving-basin margins resulted in thinner systems. Turbidite systems exhibit progressively smaller maximum thickness-to-area ratios, i.e., system areas increased more than maximum thicknesses during successive growth phases. This is most likely a result of progressive turbidite deposition “healing” relatively high-relief bathymetry. We compared these examples from the California Borderland and a similar setting to larger, unconfined systems. The growth and morphologies of turbidite systems in confined receiving basins, such as the western Gulf of Mexico slope, are greatly influenced by relatively meager volumes of sediment supplied and receiving-basin confinement, and are distinctively different from larger systems in unconfined ocean basins with sediment supplied from extensive terrestrial drainages. Areal characteristics (i.e., length-to-width and length-to-area ratios) of turbidite systems are generally similar as a result of sediment-gravity-flow processes and larger-scale autogenic behavior (e.g., channel avulsion, lobe switching, etc.); however, differences are common in tectonically complex settings as a result of receiving-basin geometry. Results of this study provide insights into the distribution and morphology of the largest detrital accumulations on Earth, which can be directly applied to predictive models of turbidite-architecture development in confined receiving basins.