THE SCIENCE IN MAKING MOVIES: ELUCIDATING THE VIABILITY OF KINEMATIC RECONSTRUCTIONS

Animations have become a powerful tool in teaching geology, due to the visual nature of the subject and its incredible breadth in both time and space. The visualization of data is also an essential element of most modern scientific research. Animations can help researchers discover trends, evaluate processes, and test the viability of kinematic or dynamic evolutions. To facilitate the goal of understanding how and why a system evolved, sequential reconstructions turned into even simple animations can test the accuracy or viability of time-progressive kinematic scenarios.

In a fold-thrust belt, the viability of a cross section rests on the assumption that if we truly understand how structures form, then we should be able to take them apart. Thus an often overlooked “proof” that a section is balanced is an incrementally or sequentially restored section. Through sequential restoration it is possible to evaluate conservation of fault slip along the entire path of a thrust system. To illustrate this concept, I present a sequentially restored, balanced cross section through the northern Bolivia (15-16ºS), and incorporate new mineral cooling ages to 1) evaluate the viability of the geometry portrayed in the cross section and 2) create a sequential scenario for the fold-thrust belt that can be tested by thermochronologic cooling ages and available basin migration history.

In map view reconstructions of extensional terranes, by combining many regional structural constraints into a single model, the self-consistency of the model (i.e., its strain compatibility through time) provides powerful additional constraints on the kinematics of the region as a whole. These include 1) constraints on its surroundings where information may not be available, 2) the quantification of uncertainty estimates, and 3) contradiction of local constraints, focusing attention on information that is most critical for improving the accuracy of the reconstruction. Using an Arc GIS based, tectonic animation of western North America, I will show that the animation is much better at highlighting unforeseen problems than answering persistent questions. The most apparent “problems” deal with interactions between the magnitude and timing of displacements, which emphasize that even when the finite solution is viable, the incremental solution may not be.