Multi-Scale Analysis of Deep-Water Deposits from High-Relief Slope Systems, Cretaceous Strata of the Magallanes Basin, Southern Chile and Colville Basin, Northern Alaska
Deep-water depositional systems are as diverse as their shallow marine counterparts, yet remain more poorly understood. Due to an inability to directly monitor high-energy currents in the deep-sea, key insights about formative processes are deduced from the stratigraphic record. In this thesis, sedimentary processes and stratigraphic architecture of slope depositional systems are studied at multiple scales and in varied datasets. The basis of this investigation are two Cretaceous-aged slope systems of similar relief and evolution: 1) the Brookian succession of the Colville Basin, North Slope, Alaska; and 2) the Tres Pasos-Dorotea succession of the Magallanes Basin, Chile. Sediment transfer from shallow marine shelf settings to the deep-sea is controlled by a variety of allogenic (e.g., sediment supply) and autogenic (e.g., delta lobe switching) factors. 3-D seismic analysis of the Alaskan slope system demonstrates varied sediment delivery beyond the shelf edge to the deep-sea both in time and space. The unique perspective of along-strike variation in slope to basin processes stresses the limitations of classical 2-D interpretations of basin margin evolution (e.g., sequence stratigraphy, trajectory analysis). Lateral switching of shelf-edge delta lobes, for example, variably impacts the shelf-edge trajectory, slope rugosity and linked basin floor sedimentation along strike. In outcropping Chilean strata, a deep-water sediment-routing system segment characterized by the transition from weakly confined to confined channels is identified. This depositional setting has been poorly constrained, and detailed sedimentological analysis characterizes various stratigraphic units attributed to channels, scours, and sandy bedform deposits characterized by back-set stratification. The dataset captures submarine channels in various stages of development, including scour fills and cyclic steps, low aspect-ratio channel fills, and high aspect-ratio channel fills. The outcrop-constrained strata provide the basis for a geocellular model populated with facies and rock properties, which is used to generate a series of synthetic seismic models. Comparison of the lithology model and seismic volumes reveals differences in the expressions of stratigraphic surfaces and sedimentary bodies. Surfaces that are clear in the outcrop are often not imaged in seismic data; conversely, surfaces defined by high amplitude in seismic volumes are often highly composite, comprised of reflections generated from numerous outcrop-constrained surfaces.
Pemberton, E. (2016). Multi-Scale Analysis of Deep-Water Deposits from High-Relief Slope Systems, Cretaceous Strata of the Magallanes Basin, Southern Chile and Colville Basin, Northern Alaska (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/27036