|Musing about a seismic interpretation, Uinta Basin, Utah|
The link below, to my online storage, contains a PowerPoint file that chronicles the process I went through trying to figure out the aeromagnetic seismic interpretation of a lease our company has in the Uinta Basin, Utah. My web page is too primitive to present the maps in sufficient detail to be meaningful; however, you should be able to expand the size of the maps on the Power Point presentation. I have tentatively come to the conclusion that the magnetic highs are more indicative of a meteor shower of small bolides rather than the traditional interpretation that they represent basement highs. There were too few Dakota penetrations or sufficient seismic information in the area at the time the map was made to have the necessary control needed to make a structure map of this detail on the top of the Dakota Formation. Second future drilling and well control of tops of shallower formations gave a different picture all together. Finally 3D seismic did not confirm the magnetic interpretation made by the authors of this structure map. I did not believe the authors made up the structural interpretation out of whole cloth, and the only way I could imagine that the information necessary to map all these small structures was obtained was by surface mapping in the field. I made a quick drive by in the field to see if there was any surface evidence that might indicate structural highs in the area. I came across some large steeply dipping sandstone blocks (megabreccia clasts?) scattered about in a small circle (see photographs in linked file). This particular group of clasts is off the aeromagnetic map, but in the vicinity. I also found other more subtle evidence of small structural features. This structural information may have been used as evidence in the field to map the small Dakota highs plotted on the map. I might find more of these structures that fit the mapped structures if and when I have more time. I also need to do more microscope work and try to determine if there is any microscopic evidence of shock metamorphism. What finding the structure in the field did was raise my suspicions that the magnetic highs might represent a surface phenomena rather than a deep basement structure. In the file linked below I give more detail of how I came to believe that the magnetic highs were caused by magnetic meteorite material scattered on the surface that was measured by the aeromagnetic survey.
I must emphasize that my musing about this data is pure speculation, and at present I have no hard evidence that these surface structures are the result of small bolide impacts.