A New Facies Model for Asymmetric Deltas Formed by Downdrift Lobe Growth
University of Nebraska-Lincoln, Department of Earth and Atmospheric Sciences, Lincoln, Nebraska, USA
Studies of modern deltas are stimulating changes to ideas about deltaic reservoir characteristics. Asymmetric growth is now thought to exert a strong influence on deltaic sand bodies. The model for wave-influenced asymmetric deltas predicts best reservoir development on the up-drift side of the river mouth. Other studies have demonstrated that plume deflection during deltaic growth may lead to the development of reservoir bodies on the down-drift side—just the opposite of the former model. This study will represent the first facies model for an asymmetric delta formed by plume deflection. It will focus on deltaic deposits of the Ferron Sandstone (Turonian) in Utah, USA, where continuous exposures exist for 65 km along strike and 30-km along dip near the Henry Mountains. Recent work by this research group demonstrates an asymmetric deflection of mean paleocurrent directions by some 60–80 degrees from proximal to distal facies from a broad interval within the Ferron Sandstone. The present study focuses more closely on several selected parasequences to develop a high-resolution, three-dimensional facies model. Closely spaced measured sections will be used to examine lithofacies, paleocurrent directions, and trace fossil size, diversity, and abundance as a measure of stresses on organisms from riverine water and sediment input. This work will extend the range of models for predicting reservoir geometry, quality, and interconnectedness in deltaic deposits worldwide.
AAPG Search and Discovery Article #90183©2013 AAPG Foundation 2013 Grants-in-Aid Projects