Implications of Shoreline Trajectory for Transgressive Facies Architecture

Jordan, Oliver¹, Sanjeev Gupta¹, Gary Hampson¹, Howard Johnson¹ (1) Imperial College London, London, United Kingdom

Recent studies have highlighted the importance of the shoreline trajectory in controlling transgressive facies architecture. The coastline migration (shoreline trajectory) is critical to understanding the stratigraphic preservation potential because of erosion occurring during transgression (e.g. at the wave-base “razor”). Analysis of ancient analogues showing different shoreline trajectories has provided an understanding of the sandbody dimensions, distributions and architectures in addition to documenting the lateral and vertical interactions between facies types.

The Cretaceous Cliffhouse Sandstone exhibits several shoreline trajectories and outcrops in localities throughout the San Juan Basin (southwest Colorado and northwest New Mexico). This succession has provided a detailed data set and enabled the correlation of key stratigraphic surfaces between logged sections. Regional facies architectures and sandbody distributions have been correlated from up-dip to down-dip pinch-out of the transgressive sandstone complex. The architecture exhibits a complex arrangement of stacked wave-dominated deposits, tide-dominated sheet and channel sands, lagoonal sand-, silt- and mudstones in addition to coastal plain sand- and siltstones related to the underlying Menefee Formation. These facies are separated into distinct sedimentary packages by a hierarchy of erosional bounding surfaces (wave and tidal ravinement surfaces) which may act as barriers or baffles to flow and influence reservoir connectivity. In addition, these surfaces determine the net reservoir thickness and up-dip to down-dip extent. This study shows that higher shoreline trajectories have greater preservation potentials and high vertical connectivity whilst lower trajectories have lower preservation potentials and are expressed as thinner successions with low vertical connectivity.