Resolving sedimentology, stratigraphic architecture and evolution of deep-water systems in two structurally complex areas : the Upper Cretaceous Pigeon Point Formation, California, and the Oligocene Molasse Basin, Austria

Deep-water deposits remain major targets for hydrocarbon exploration and production due to the worldwide success of such ventures to date. Understanding spatial variability of sedimentary facies, sedimentology, depositional environments, and provenance of deep-water deposits are crucial to exploiting the economic potential of these deposits. This dissertation investigates two deep-water systems through outcrop and subsurface studies. Chapter 1 documents the stratigraphic and sedimentological framework of the Upper Cretaceous Pigeon Point Formation through detailed stratigraphic measurements and high-resolution geologic mapping. The outcrop represents deep-water deposits in the late Mesozoic forearc system of western California that have been translated several hundred kilometers northward along faults of the San Andreas Fault system. Lithofacies assemblages suggest that the Pigeon Point Formation outcrops represent the upslope parts of a major deep-water system, including submarine canyon fill and proximal channel-levee complex. Chapter 2 focuses on utilizing provenance analyses, including sandstone petrography, detrital zircon geochronology, mudstone geochemistry, and stratigraphic interpretations of the depositional environments to evaluate the geologic relationship between the Upper Cretaceous Pigeon Point Formation, which outcrops south of San Francisco, California, and the Atascadero Formation, which today outcrops to the south in central California. Slip along the San Gregorio-Hosgri Fault, which separates the two formations, is estimated to be 156 ± 4 km since the late Miocene based in part on correlation of the Pigeon Point Formation with the Atascadero Formation across the fault.Our results suggest that the Pigeon Point and Atascadero formations have similar provenance signatures, but major contrasts in depositional environment: the Pigeon Point Formation represents an upslope and submarine canyon depositional setting whereas the Atascadero Formation consists of stratigraphic units more typical of mid-fan deposition. These contrasts are difficult to reconcile with the proposed tectonic reconstruction of the San Gregorio-Hosgri Fault, which places the original depositional site of the Pigeon Point Formation to the west of the Atascadero Formation. The original depositional setting of these two formations had the Pigeon Point Formation lying upslope and to the east of the Atascadero Formation, and that the two have been decoupled and offset along the Nacimiento Fault south of about Monterey. Chapter 3 investigates deep-water sediments deposited in the Tertiary Molasse Foreland Basin in Austria to understand how mass transport deposits (MTDs) impacted the subsequent turbidity currents and their depositional style. This study utilizes multi-scale subsurface data, including cores, well logs, and 3D seismic data to understand both fine- scale sedimentology and the large-scale facies distributions. Detailed analyses suggest that MTDs played an important role during the early evolution of the basin by controlling the general fairways for flow and deposition of syn- and post-MTD turbidity currents and distribution and structuring of their deposits. Chapter 4 demonstrates an application of statistical and machine learning models for facies classification in subsurface data as well as an integration of model predictions with seismic architectural analysis. Subsurface data from the Austrian Molasse Basin are used to establish the workflow of developing machine learning models from well logs and core data, predicting facies from well logs, and applying the trained models on well logs where cores are not available

Keywords: Geological Sciences.
Advisor: Lowe Donald R.
Graham S. A. (Stephan Alan)
Mukerji Tapan