Variations in the architecture of fluvial deposits within a marginal marine setting, Eocene Sobrarbe and Escanilla formations, Spain

Abstract

Fluvial systems located near marginal-marine settings are prolific hydrocarbon reservoirs around the world. Outcrops that contain strata that can be correlated from fluvial deposits to coevally deposited marginal marine deposits are important because they provide a rare opportunity to relate fluvial architecture to relative changes in sea level (accommodation to sediment supply changes (A/S)). This information is important because it can be used to aid in reservoir characterization and prediction. This dissertation comprises four outcrop studies of a marginal marine and fluvial deposits of the Eocene Sobrarbe and Escanilla Formations, Ainsa Basin, Spain, focused at three different scales of observation: third- (Chapter 2), fourth- (Chapters 2, 3, 4, and 5), and fifth-order cyclicity (Chapters 4 and 5). This dissertation advances our scientific knowledge about the deposition of fluvial systems in high-accommodation, high-sediment supply settings. The continuity between the axis and margin of the basin and fluvial and coevally deposited marginal marine strata allow for the quantitative documentation of: (1) structure-stratigraphic interactions of the Sobrarbe and Escanilla Formations (Chapter 2); (2) the relationship between fluvial architecture and A/S (Chapter 3); (3) axis-to-margin variations of transgressive fluvial deposits (Chapter 4); and (4) relationships between fluvial architecture and shoreline trajectory (Chapter 5). Key contributions of this dissertation are the following. First, this dissertation provides a more comprehensive knowledge about the structure-stratigraphic evolution of the Sobrarbe and Escanilla Formations than what was previously known (Chapter 2). Second, this dissertation provides knowledge of how large-scale stratigraphic stacking patterns can be used as a predictor of small- (reservoir) scale characteristics and how subdividing populations on the basis of geological distinctions can have important implications when building reservoir models (Chapter 3). Third, this dissertation provides a better understanding of the lateral and vertical distributions of stratigraphic architecture and static connectivity of fluvial strata within a transgressive fluvial system (Chapter 4). Fourth, this dissertation provides a better understanding of the role of autogenic and allogenic processes on stratigraphic architecture of transgressive fluvial deposits and shoreline trajectory at both fourth-order and fifth-order scales of cyclicity (Chapter 5).