Analysis of large-diameter, complex burrows and associated trace fossils in the Salt Wash Member, Upper Jurassic Morrison Formation, southeast Utah

Derek Charles William Raisanen
The University of Kansas, Department of Geology Lawrence, Kansas, United States
[email protected]

This project is identifying the origin, range of morphologies, geographic extent, and potential effects on fluid flow of large-diameter burrows within the Salt Wash Member, Upper Jurassic Morrison Formation in southeast Utah. Determining the range of morphologies represented by these burrows and determining the potential tracemakers—mammals, therapsids, and reptiles—not currently represented by body fossils locally, will enhance reconstructions of the local paleoecology and paleoenvironment. Tracking the burrowed layer may show that it is extensive enough to be a useful stratigraphic marker in regional stratigraphy. The different lithologies in the burrow fill and the matrix may have an effect on movement of groundwater and hydrocarbons in this and similar systems.

Preliminary results show two distinct morphologies for the burrows. The burrowed layer has been identified ~80 km away from the initial study area.

The Salt Wash Member of the Morrison Formation is a complex fluvial system of interbedded sandstone, siltstone, and mudstone. The burrows may act as macrochannels and their effect will be dependent on their density and distribution. The burrow macrochannels can affect the ability of the mudrock matrix to act as a barrier or baffle to fluid flow by improving connectivity between underlying and overlying sandstones. Applying what is learned in this study to previous research in the Salt Wash Member near the study area can greatly improve earlier reservoir models.

AAPG Search and Discovery Article #90157©2012 AAPG Foundation 2012 Grants-in-Aid Projects