Geomorphic expressions of active rifting reflect the role of structural inheritance: A new model for the evolution of the Shanxi Rift, North China

Abstract

Abstract. Many rifts are influenced by pre-existing structures and heterogeneities during their evolution, a process known as structural inheritance. During rift evolution, these heterogeneities may aid rift nucleation, growth, and segmentation of faults, encourage linkage of various segments, or even inhibit the formation of faults. Understanding how structural inheritance influences early rift evolution could be vital for evaluating seismic risk in tectonically active areas. The Shanxi Rift in the North of China is an active rift system believed to have formed along the trend of the Proterozoic Trans North China Orogen, however, the influence of these pre-existing structures on the present-day rift architecture is poorly known. Here we use tectonic geomorphological techniques, e.g., hypsometric integral (HI), channel steepness (ksn) and local relief to identify the impact of structural inheritance on the formation of the Shanxi Rift. Of these measures, we found that HI was less sensitive to lithology and more valuable in evaluating the tectonic signal. Based on their geomorphic expression we characterise the activity levels of active faults and found that activity is concentrated in two rift interaction zones (RIZ) formed between the sub-basins. Furthermore, we found that many faults formed parallel to inherited structures. Based on these observations we propose a new model for the evolution of the Shanxi Rift where inherited structures play an important part in the initial segmentation of the rift which in turn controls the development of the RIZ structures. Geomorphic indices might prove useful in the study of the evolution of structural inheritance in other active rifts, such as the East African Rift.