An Integrated Approach to the Study of Turbidite Systems

Abstract

Meaningful comparisons of modern and ancient turbidite systems must include consideration of the physical and temporal scales of the deposits as well as the limitations presented by the widely varying techniques used to map and describe the deposits. To facilitate such comparisons, we describe five basic elements of turbidite systems that, with appropriate types of field observations, can be recognized in both ancient and modern systems (i.e., in marine geologic, outcrop, or seismic-stratigraphie studies). The primary elements discussed are (1) major erosional features (other than channels), (2) channels, (3) overbank deposits, (4) lobes, and (5) channel-lobe-transition deposits. The determination of time-equivalent elements within any given turbidite system is necessary for deciphering depositional processes and sequence stratigraphy as well as for comparison with different systems to develop reliable, predictive sedimentation models for both modern and ancient submarine fans and other types of turbidite systems. This chapter is primarily intended to help stratigraphers and explorationists avoid being misled by the application of existing models. These models generally have not adequately taken into account either the complex interaction of the many factors that control turbi-dite deposition or the different stages of growth that many types of turbidite systems undergo with time during their evolution. Geometry of sandstone bodies, facies types, and resulting facies associations can differ substantially from one system to another in response to different composition and volume of turbidity currents as well as to the different factors (e.g., eustacy and tectonic control) that control the development of stages within a system. Basin type and configuration are also of primary importance in controlling geometry and facies patterns on turbidite systems. Care should be exerted also in applying submarine-fan models as depicted in recent seismic-stratigraphic studies. These models have no \textquotedblleft{}general validity\textquotedblright{} and suffer severe limitations because of lack of supporting sedimentological data and, at least in part, could represent systems that were more or less affected by bottom-current activity.