Evaluating the Rheological Controls on Topography Development During Craton Stabilization: Objective Approaches to Comparing Geodynamic Models

Surface topography is an important yet largely neglected aspect of the early evolution of cratons. The lateral accretion of cratonic nuclei inevitably forms orogenic belts that subsequently provide a sediment source for large, resource-rich intracratonic basins, but to date, geodynamic models have focused exclusively on lithospheric root processes. Here we use two-dimensional thermal-mechanical models to study the topography and lithospheric deformation during 50 Myr of compression of a cratonic nucleus, to simulate the lateral accretion phase of craton growth in the Neoarchean. Although the cratonic nucleus thickens slightly during the compression phase, most of the deformation occurs in the regions adjacent to the nucleus that have weaker lithosphere. Here, crustal thickness triples developing high topography in excess of 10 km without active erosion. Models with different initial rheological parameters will have different final topography and lithosphere geometry, but in general it is difficult to shorten and deform the depleted cratonic nucleus, unless there are significantly weak heterogeneities in the mantle lithosphere. We apply two quantitative analysis techniques to objectively evaluate a multitude of model outputs. Cross-correlation clustering (CCC) measures the degree of similarity between topography profiles and categorizes models based on the general topographic character. Six different topography families are possible in the context of our models and crustal strength is the most important parameter affecting the shape. From principal component analysis (PCA) we identify four dominant lithosphere geometries. When used together, these two methods provide distinct yet complementary information about the surface and subsurface deformation features in our models. Cratons, the ancient building blocks of continents, have existed on our planet, virtually unchanged, for the last 2 to 3 billion years. These regions contain the world's largest deposits of economic and precious metals, and they preserve the earliest evidence of life on Earth. The longevity of cratons is attributed to their unique chemical composition and structure that modern day plate tectonics is unable to reproduce. Therefore, understanding how cratons form may help unlock some of the mystery of Earth's early history. While many previous geodynamic studies on this topic have been published, the evolution of surface topography during craton formation via lateral compression has been ignored until now. We present 54 numerical models to test a wide range of initial conditions, showing that topographic relief is largely controlled by crustal strength. We also demonstrate how quantitative analysis techniques can effectively cluster models based on their large-scale behavior and therefore aid in the interpretation of model results. Quantitative clustering techniques effectively summarize results from numerous numerical models and facilitate objective comparison Significant surface topography formed during cratonic nuclei compression in supercontinent cycles is strongly controlled by crustal strength Homogenous cratonic lithosphere is resistant to pure shear thickening when subjected to horizontal compression