Accommodation and Supply Driven Sequences: Insights From Stratigraphic Forward Modeling

Abstract

The stratal geometries influenced by accommodation change are well documented. In contrast, the role of sediment supply on sequence development are less well understood. We employ numerical stratigraphic forward modeling, DionisosFlow, to study the influences of both accommodation and sediment supply. Two model sets, accommodation-driven cycles with variable sea level and constant ratio between sediment discharge (Q_s) and water discharge (Q_w) as well as supply-driven cycles with constant sea level and variable Q_s/Q_w ratio, are used to simulate the shoreline migrations on the shelf. Our result suggests that both sea-level change and variations in Q_s/Q_w ratio are able to form sequence bounding unconformities therefore both accommodation-driven cycles and supply-driven cycles meet the traditional definitions of sequences. The comparison between two model sets suggests the accommodation-driven sequence and supply-driven sequence share several characteristics (e.g., long-distance regression and absence of coastal-plain topset deposits) which were traditionally interpreted as the results of falling sea level. In addition, these characteristics of both sequences are different when the amplitude of sea-level change, Q_s/Q_w ratio, transport diffusion coefficient, and morphology change. Sea-level fall does not always generate unconformities under the conditions of high Q_s/Q_w ratio and slow sea-level change. This study suggests that the sequence development has multiple controls.

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