Overview

The subject of stratigraphy and sedimentation is concerned with rock features ranging in size from 10 ^?5 m (grain size) to 10 ⁵ m (depositional systems). Our interest here is a basic understanding of those stratigraphic features likely to be visible in seismic reflection data. With the bandwidth limitation of surface seismic data, this means features thicker than a few tens of meters and lateral extent of twice that.

Large-scale stratigraphic features seen in 2D seismic data are evidenced by bed terminations. Stratigraphic bed terminations seen in seismic data occur in only a few ways as illustrated in Figure 24.1. From these basic building blocks, complex geologic relationships can be deduced through the principles of seismic stratigraphy ^[188] developed in the 1970s and sequence stratigraphy ^[189] a decade later.

Figure 24.1: Classification of bed terminations likely to be observed on seismic data. Stratigraphic terminations are fundamental components of seismic stratigraphy using 2D seismic data.

From the mid-1980s on, 3D seismic data afforded a direct map view of stratigraphic features that was never available from even a grid of 2D seismic lines. This revolution is continuing with more and better ways to pull stratigraphic information from 3D seismic data.