Visualizing the sedimentary response through the orogenic cycle: A multidimensional scaling approach

Abstract

Changing patterns in detrital provenance through time have the ability to resolve salient features of an orogenic cycle. Such changes in the age spectrum of detrital minerals may be attributable to fluctuations in the geodynamic regime (e.g., opening of seaways, initiation of subduction and arc magmatism, and transition from subduction to collisional tectonics with arrival of exotic crustal material). This changing geodynamic regime leads to a variety of sedimentary responses driven by basin formation, transition from rift to drift sedimentation, or inversion and basement unroofing. Detrital zircon grains within sedimentary rocks chart the aforementioned processes by the presence of older detrital zircon populations during basement unroofing events, followed by a successive younging in the detrital zircon age signature either through arrival of young island arc terranes or the progression of subduction magmatism along a continental margin. Hence, the response within the detrital zircon cargo to the geodynamic environment can be visualized in their changing age patterns. However, such patterns are often cryptic and evaluated on the basis of visual comparisons. In an effort to enhance objectivity in the diagnosis of the sedimentary response to the orogenic cycle, we illustrate the utility of a multidimensional scaling approach to detrital zircon age spectra. This statistical tool characterizes the “dissimilarity” of age spectra from various sedimentary successions, but it importantly also charts this measure through time. We present three case studies in which multidimensional scaling reveals additional useful information on the style of basin evolution within the orogenic cycle. The Albany-Fraser orogen in Western Australia and Grenville orogen (sensu stricto) in Laurentia demonstrate clear patterns in which detrital zircon age spectra become more dissimilar with time. In stark contrast, sedimentary successions from the Mesoproterozoic to Neoproterozoic North Atlantic region reveal no consistent pattern. Rather, the North Atlantic region reflects a signature consistent with significant zircon age communication due to a distal position from the orogenic front, oblique translation of terranes, and complexity of the continental margin. This statistical approach provides a mechanism to connect the evolutionary patterns of detrital zircon age spectra to the geodynamics of an orogenic system, which in many cases is a direct function of proximity to the orogenic front.