Embryonic basins in a border fault relay zone, significance for the tectonic evolution of Lake Baikal
Hus, R.; Matton, C.; Klerkx, J.; De Batist, M. (2001). Embryonic basins in a border fault relay zone, significance for the tectonic evolution of Lake Baikal. J. Conf. Abstr. 6: 632 In: Journal of Conference Abstracts. Cambridge Publications: Cambridge. ISSN 1362-0886, more |
| Available in | Authors | | Document type: Summary
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| Authors | | Top | - Hus, R.
- Matton, C.
- Klerkx, J.
- De Batist, M., more
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| Abstract | The segmented nature of Lake Baikal is well expressed by the different geometry of its three sub-basins. This is a result of the different orientation of the main border faults, changing their strike from a more or less SW-NE direction in the southern basin to an almost N-S direction in the northern part of Lake Baikal. The Zavarotny area, along the northwestern lake border, is one of the areas where such a change in orientation is observed. Within this area two different segments of the Baikalsky border fault partly overlap, revealing a linking relay structure. Here the southern fault segment dies out in the lake, allowing a western onshore fault to take over its displacement towards the north. The morphology of the offshore part in this relay zone was examined on digital terrain models, constructed from echo sounding data. This DTM revealed the presence of small basins and ridges within the area, striking obliquely to the border faults. Structural investigations on a detailed high-resolution seismic grid, allowed us to accurately determine the geometry of the faults delimiting these basins. The structure of the onshore part is less well studied because large parts of it are covered by coarse-grained sediments from the Baikalsky Range. Although the two Baikalsky fault segments strike – within the zone of overlap – almost parallelly and have the same dip direction, we observe structures that differ significantly from those well known from relay ramp studies. The ramp structure we observe dips towards the north east, but it is not cross-cut by faults striking more or less orthogonal to the main fault segments. Instead we observe only faults that are slightly oblique, and even smaller faults that are almost parallel. These smaller faults are interpreted as being a result of block rotations in some parts of the ramp along axes parallel to the major faults. The observed deviation from the ideal relay ramp picture is most probably a result of the interference between fault linking processes as well as others. Indeed other processes are to be expected as the border fault deflection systematically occurs on left overstepping relays or splays. This suggests that the main active fault is slightly ‘rotated’ in a clockwise direction, leaving earlier fault traces to become less important. Whether lateral movements on the major transfer zones, separating the different Baikal basins, could be the underlying mechanism is a topic of future research. |
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