Project Description
The objectives of this project are to better understand 1) the nature of sediment deposits in the late Paleozoic Ansilta Formation in northwest Argentina, and 2) the extent of ice sheet coverage at the time.
Deposited about 315 million years ago during the late Paleozoic ice age, the Ansilta Formation sediments can provide information on the local position of the ice sheet and the local glacial environment. However, interpreting this information in the context of global climate requires an understanding of the latitude at which these deposits were formed. The inclination (steepness) of Earth’s magnetic field is systematically related to latitude, and the magnetic field vector is recorded by fine-grained sediments at or near the time of deposition. This is achieved by an aligning torque between Earth’s field and magnetic minerals within the sediment. The sediments therefore provide an archive of paleolatitude. Unfortunately, most rocks of this age in South America have been remagnetized and carry a much younger magnetization, making it challenging to find a true paleolatitude. The goal of this SURF is to conduct a conglomerate test which will tell us if the rocks of the Ansilta formation have been remagnetized.
Tasks and Responsibilites
The student will be responsible for the entire experiment, as well as data interpretation. A conglomerate is a sedimentary deposit where larger fragments or clasts are surrounded by a matrix of finer-grained material. Because the large clasts (in this case > 8 cm) are too big to be re-aligned by exposure to Earth’s magnetic field, clast magnetization directions will be random in a deposit that has not been remagnetized. By contrast, if the deposit was later remagnetized (perhaps by a regional thermal event), all the clasts will have the same magnetization direction. The experiment designed to recover the clast magnetization direction involves heating the samples to progressively higher temperatures and then measuring the magnetization after each step. This data is then interpreted in terms of a best-fit direction, and statistical tests can be applied to assess whether the directions are random or not. The student will be responsible for all of these tasks.