TRACE ELEMENT ANALYSIS OF QUARTZITE CLASTS FROM SESPE FORMATION AND SOURCE ROCKS FROM SOUTHEAST CALIFORNIA AND CENTRAL ARIZONA

The Sespe Formation is an Eocene to Miocene sedimentary unit outcropping in the northwest regions of the Transverse Range north of the Los Angeles Basin. In the late 1990s the general consensus about the Sespe Formation was that it is a fluvial sequence created in a deltaic system by two paleorivers. Jeffrey L. Howard in 2000 made petrographic comparisons between quartzite conglomerate clasts from the Sespe with various quartzite source rocks in central Arizona and southeast California and concluded that one river flowed north and south near present-day Death Valley and it was the ancient Colorado river, and the other river flowed off the Mazatzal Peaks in central Arizona and was the Gila river. For this research, the quartzite clasts and source rocks analyzed petrographically by Howard were reanalyzed and compared through trace element composition and statistical calculations to determine if the Sespe clasts match the source rocks. X-Ray Fluorescence was used to get the ppm values of all the elements present in each rock. Using MATLAB, the ppm values were used to make line plots comparing the values of individual elements between the two rock groups, a correlation coefficient chart was made comparing the correlation between the two rock groups, and principle component analysis was done to plot the loads of individual rock samples to see how they relate with each other. The data from the correlation coefficient chart and PCA plots confirmed that the quartzite clasts in the Sespe have very similar trace element compositions with the quartzite source rocks which further supports the hypothesis that two paleorivers flowed through central Arizona and near present day Death Valley and into present day Los Angeles Basin area.