Print this pageThe Growth of Normal Faults Through Enhanced Segment Linkage in a Region with a Strong Structural Inheritance: North Basin, Northern Malawi Rift, Africa
Estelle Mortimer1, Douglas A. Paton2, C A
Scholz3, M Strecker1, and P Blisniuk1
1 University of Potsdam, Potsdam, Germany
2 GeoForschungsZentrum, Potsdam, Germany
3 Syracuse University, Syracuse,
The development, growth and linkage of normal faults in rift settings have been the focus of many recent studies. Established fault-growth models, generated from numerical, analogue and field observations, predict the growth of isolated faults by tip propagation, by linkage due to interactions between neighbouring structures, and the pattern of evolution of normal fault arrays. However, a limitation of these models is that they assume such development within homogeneous lithosphere. A few recently studies have begun to address the role of crustal heterogeneity on normal fault-growth, and predict a modification of existing fault-growth models. The North basin, Malawi rift, is situated within a region of crustal anisotropy; the position of the basin-bounding fault is controlled by Proterozoic structural fabrics. Here we test the applicability of established fault-growth models to this region with a notable structural inheritance.
In our investigation, we utilise basin-scale seismic reflection data to reconstruct the fault-growth history, in particular of intra-basin structures, to test the applicability of established fault-growth models. We identify 11 long-length, high-displacement, intra-basin structures striking sub-parallel to the basin-bounding fault. At a first order, segmentation, interaction and linkage of intra-basin structures conform to the predictions of fault-growth models. However, we observed that intra-basin structures are long-lived, and exhibit an early length - later displacement characteristic not predicted by established models, suggesting that their growth has been modified. We hypothesise that longevity of intra-basin structures and early length acquisition is associated with pre-existing structural heterogeneity that potentially enhances fault segment propagation.
AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005