084 -- Using Thermal Demagnetization to Date Diabase Dike, Scottsville Basin, VA

The purpose of this project was to determine the age of a diabase dike intrusion in Virginia using paleomagnetism. Previous attempts to date this intrusion using alternating field demagnetization were unsuccessful. Ten samples of this intrusion were run through thermal demagnetization to measure the orientation of the dike’s primary magnetization. The specimens were put through a series of heating steps in a paleomagnetic oven. After each heating step, data was collected for the samples’ magnetic orientation and magnetic susceptibility. Results indicated the magnetic susceptibility gradually decreased as the experiment progressed, signifying a lack of magnetic mineral growth during heating. The data suggested that this dike had a consistent, reproducible magnetic signal. A reasonable age of emplacement of approximately 160 Ma was also identified. This experiment shows that thermal demagnetization was a great technique for identifying a rock sample’s magnetic signal. While this technique may not work on all specimens, it is still a useful tool and should be utilized on similar samples. Future projects should analyze dike samples from many different locations in Virginia to determine if the results presented here are an accurate estimation of the age of this rock sample.