Characterizing the Growth of Structures in Three-Dimensions Using Patterns of Deepwater Fan and Channel Systems in Growth Strata

Abstract

Channel and fan systems in deepwater continental slopes respond to active deformation. The history of deformation is recorded in the patterns of channels and fans within growth strata, providing important constraints on the timing and kinematics of deformation. We show that the location, orientation, and sinuosity of channel systems, and the location of fan deposits, are affected by the emergence and growth of fault-related folds. We aim to characterize this response of depositional systems to understand the initiation and lateral growth of these structures and further our understanding of fault-related fold kinematics.

We develop two end-member 3D kinematic models to describe the interaction of channels and growing structures. In the first model, structures grow through lateral propagation causing channels to migrate laterally outward through time. In the second model, structures grow with fixed edges, and therefore channels maintain relatively fixed positions through time. We compare our kinematic models with structures in the outer fold-and-thrust belt in the Niger Delta. The initiation of structural growth is recorded by a dramatic change in channel architecture with a reduction in sinuosity followed by migration toward the lateral edges of folds. Subsequently, in some examples, channels maintain relatively fixed positions through time, consistent with the first model. In contrast, other examples show channels that migrate laterally outward through time, similar to the second model. We corroborate our interpretations by comparing our analysis of channel distribution to isopach and structure contour maps. These results indicate that structures in close proximity can grow through different mechanisms, and that a single structure can grow with both fixed edges and lateral propagation during different times in its history.

Using these methods to constrain the timing and kinematics of geologic structures is useful in defining the initiation and growth of prospective structural traps. As an example, structures that grow with fixed lateral edges generally maintain closure size and fetch area through time, whereas these properties can increase dramatically in structures with laterally propagating edges. Understanding the growth of folds through time gives insight into location and stacking patterns of turbidite fan systems and channels through time, which leads to a better understanding of reservoir distribution in deepwater environments.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018