The roles and seismic expressions of turbidites and mass transport deposits using stratigraphic forward modeling and seismic forward modeling

Abstract

• Mass transport is more efficient than turbidity current in forming submarine canyons . • Turbidites are inside the river-fed systems as jigsaw puzzle geometries vertically. • MTDs are not constrained by river-fed systems and tend to occur in the bottom. • MTDs have chaotic or transparent seismic facies with irregular, massive thick shapes. • Turbidites have high amplitude seismic facies with sheet, mound or channel shapes. Turbidity currents and mass transport are two principal processes in deepwater settings. However, their roles in shaping deepwater depositional systems and interpreting their deposits in seismic profiles have not been fully settled due to the lack of extensive well data and high-quality seismic data in comparison with onshore oil fields. Therefore, this study integrated stratigraphic forward modeling (SFM) and seismic forward modeling to differentiate between the contributions of turbidity currents and mass transport as well as their seismic expressions. The workflow firstly compared three single-scenario SFM models, Model A (mass transport active), Model B (turbidity currents active), Model C (both active) to explore their contributions and interplay. Secondly, a multi-process and multi-scenario SFM model, Model D, is discussed with special emphasis on canyons. Thirdly, synthetic seismic profiles are generated via seismic forward modeling using the outcomes of the second step, then compared with actual seismic facies to verify the reliability. Through the abovementioned three steps, this study reveals that mass transport plays a major role in initiating canyons whereas turbidity currents act mainly as the reworking process. Turbidites are usually confined to shelf-incised canyons and adjacent canyons fed by terrestrial systems. Mass transport deposits (MTDs) are mainly distributed on the bottom of canyons and deep basins, forming the base boundary of each depositional cycle. A total of 14 synthetic seismic facies are identified. The comparison with actual seismic data shows that modeling results are similar to equivalent actual seismic features. This study helps to predict the spatial emplacement of MTDs and turbidites and interpret deepwater seismic data.