Sedimentology, stratigraphic architecture, and provenance of deep-water systems [electronic resource] : Neoproterozoic Zerrissene Group, Namibia and Neogene east coast basin, New Zealand
Keywords: Geological and Environmental Sciences.

The spatial variability of deep-water sedimentary facies and sediment routing into submarine fan systems are of paramount importance to deep-water research because of their revealing information about turbidity current processes, resulting depositional architectures, and their potential as energy resources. Yet, despite the importance of understanding the deep-water sediment transport and spatial distribution of deep-water deposits, more downslope, unconfined, and fine-grained deposits remain less studied and more poorly understood than those accumulating in upslope locations. Studies of deep-water turbidites are often challenged by relatively poor preservation of outcrop exposures, insufficient resolution in available seismic reflection data, and limited accessibility to modern examples, which nevertheless fail to provide information on reservoir time scales. The complexity of facies distributions in submarine fans leads to challenges in predicting the geometries of their deposits. Thus, there is an increasing need for outcrop analogs of such deep-water systems in order to understand analogous subsurface exploration targets. This dissertation investigates the detailed sedimentology and stratigraphic architecture of deep-water deposits and their intrinsic relationship with regional tectonics by examining two submarine fan systems: the Neoproterozoic Zerrissene Group of the Damara Orogen in Namibia and the Neogene East Coast Basin in New Zealand. Chapter 1 investigates the provenance of the Zerrissene Group, which was deposited in a deep-water basin that likely occupied a central location between the South American Rio de la Plata Craton and the African Kalahari and Congo cratons. New depositional ages for the Zerrissene Group place the deep-water sequence in the context of the breakup of Rodinia and subsequent assembly of Gondwana, and additionally refine the timing and extent of the "Snowball Earth" Marinoan Glaciation, one of the most debated climatic 'crises' of our planet. Chapter 2 documents the distribution and depositional architecture of the large, unconfined turbidite system recorded in the Brak River Formation of the Zerrissene Group, seizing the unique opportunity to investigate the intricacies of lateral facies relationships in likely the most extensive Precambrian unconfined deep-water system in the world. Documentation of outer lobe and basin plain deposits and their relation to more proximal/axial lobe deposits at both the centimeter scale and basin-scale, across tens of kilometers, allows for the Zerrissene deep-water basin geometry to be established. Hierarchically constrained statistical distributions of bed thickness, net-to-gross measurements, and sedimentary facies proportions demonstrate the lateral variability from inner to outer lobe deposits and provide a robust dataset for modeling reservoir properties within analogous deep-water systems. Chapter 3 investigates sandstone provenance along greater than 450 km of the East Coast Basin continental margin of the North Island of New Zealand throughout Cenozoic time. Detrital zircon geochronology provides insight into latest Paleogene through late Neogene basin configuration and paleogeography, and has implications for understanding the evolving sediment dispersal and reservoir distribution in the offshore East Coast Basin. Observed spatial and temporal trends provide possible constraints for early forearc configuration, documenting the development and migration of the Coromandel Volcanic Arc and increased exhumation of local basement blocks in the Axial Ranges, associated with the development of the Alpine Fault. Chapter 4 describes the application of flying a small, unmanned aerial vehicle (UAV) to collect photographic data for modeling rock outcrops and creating detailed, georeferenced digital terrain models (DTM), which can be used for multi-scale digital feature mapping in true three-dimensional (3-D) space. The method of imaging and modeling outcrops is demonstrated in the East Coast Basin, New Zealand, where vertical, coastal cliff exposures of continental slope deposits and extensive, wave-cut platform exposures of steeply dipping, deep-water deposits offer exceptional opportunities to investigate depositional processes, stratigraphic architecture, and geometric variability of each of these systems. Results yield a spatial and temporal understanding of two deep-water depositional systems at a scale that was previously unattainable by conventional field techniques. This work is published in the Journal of Sedimentary Research, v. 87, February 2017, with co-author Stephan A. Graham.