Quantifying Deformation in Ridge-Transform Systems: An Example from the Troodos Ophiolite, Cyprus
Sarah Titus, Dept. of Geology, Carleton College
Chelsea Wagner, Dept. of Geology, Carleton College
Sarah Alexander, Dept. of Geology, Carleton College
Joshua R. Davis, Dept. of Mathematics and Statistics, Carleton College
Ridge-transform intersections are common features along divergent plate boundaries, recording complex deformation from both spreading and faulting processes. The Troodos ophiolite in Cyprus preserves a ridge-transform system defined by the NS-striking Solea Graben (paleoridge) and the EW-striking Arakapas fault (paleotransform). The excellent exposures of crustal rocks including gabbros, sheeted dikes, and lavas on the outside and inside corners of the system allow us to reconstruct deformation in two dimensions across a slice of oceanic lithosphere.
Many previous studies of deformation in the ophiolite used coupled paleomagnetic and structural data. To restore paleomagnetic directions, especially from the sheeted dike complex, these studies (1) relied on the paleomagnetic reference direction for the ophiolite, which is nearly due west in present-day coordinates, and (2) assumed that dikes intruded vertically. These studies examined patterns along 1D transects either perpendicular to the ridge, when interested in seafloor spreading processes, or perpendicular to the transform, primarily to determine the sense of motion on the Arakapas fault.
We take a different approach to characterizing deformation, made possible by the large paleomagnetic and structural datasets, including our own new paleomagnetic results from ~40 sites. Our assumptions are that (1) the paleomagnetic and structural data closest to the ridge should serve as the reference direction for rocks away from the ridge, and (2) dikes did not have to intrude vertically, but magmatic activity was localized near the ridge. Changing the reference frame to the ridge allows us to track the deformation behavior over time. For the outside corner, this means examining changes in the data as a function of westing; for the inside corner, as a function of easting. By tracking deformation along three ridge-perpendicular transects in the southern, central, and northern parts of the ophiolite, we show how the results vary not only by easting/westing but also by distance from the ridge-transform intersection. Our analysis incorporates statistical techniques, such as geodesic regression of the structural and paleomagnetic data, to quantify variation over space.