2023 CSDMS meeting-078

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Evolution of rift systems and their fault networks in response to surface processes

Derek Neuharth, ETH Zurich Zurich , Switzerland. dneuharth@erdw.ethz.ch

Sascha Brune, GFZ Potsdam Potsdam , Germany.

Thilo Wrona, GFZ Potsdam Potsdam , Germany.

Anne Glerum, GFZ Potsdam Potsdam , Germany.

Jean Braun, GFZ Potsdam Potsdam , Germany.

Xiaoping Yuan, China University of Geosciences Yuhan , China.

As a rift evolves from its initiation until continental breakup it goes through a number of different phases that can be associated with distinct rifted-margin domains and major sedimentary basins. Seismic and geophysical data around the globe can give us glimpses into the progression through these domains, however, it is not well understood how the fault network evolves to produce them. Additionally, sedimentation and erosion are known factors that influence the longevity of an evolving fault and may affect the overall rift evolution. Previous work has qualitatively investigated the effect surface processes have on an evolving rift, however, there has not been a quantitative approach to analyze changes to the fault network through time.

To investigate the quantitative effect of surface processes on an evolving rift fault network, we utilized the two-way coupling between the geodynamics code ASPECT and the landscape evolution code FastScape to run 12 high-resolution 2D rift models. Using FastScape, we vary the erosional efficiency of the stream power law by changing the bedrock erodibility (Kf) from no surface processes to low (Kf= 10-6 m0.2/yr), medium (10-5 m0.2/yr), and high (10-4 m0.2/yr) efficiency. We then apply this to three different model setups that represent a wide, asymmetric, and symmetric rift. We analyze the models using the fault analysis toolbox (fatbox), which can track and correlate individual faults and their properties through time. Specifically, we utilize this toolbox to track the evolution of the number of faults and the cumulative fault system length and displacement through time and investigate how they change depending on the efficiency of surface processes and the rift type.

Through this analysis, we find that regardless of the rift type or the efficiency of surface processes the rift fault network evolves through up to five distinct phases: 1) distributed deformation and coalescence, 2) fault system growth, 3) fault system decline and basin-ward localization, 4) rift migration, and 5) continental breakup. While we find that surface processes do not exert a strong control on the phase progression or final rifted margin architecture, they do affect the temporal evolution of the fault network by increasing fault longevity. As faults live longer with greater surface processes, the fault network phases are prolonged and continental breakup is delayed. Additionally, greater surface process efficiency leads to fewer faults forming which causes a less complex fault network.