Kinematic Markers I: Geomorphology

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Fig6 Torocko faultWorld topography is shaped by a complex interaction of various physical and chemical processes, where climate plays an important role. Different rocks may deform in very different way under same conditions. Structural stress has its important role in preconditioning the ultimate style of deformation in rocks, because fracture systems not only enhance, but may also drive erosional processes, especially in hard rocks, like limestones.

Fracture systems in lowlands may be hidden by young sediments; fault scarps in deserts are rapidly covered by mobile sand, while on oceanic passive margins delta systems may shed sediment over them. Fluvial channels also migrate autocyclically in the alluvial plain, hence cannot be used with automatism in geomorphological studies, however automatic techniques might be useful in delimiting recently uplifted areas. The higher the sediment input, the less chance we have to capture neotectonic events. Because on the central part of oceanic basins sediment input is extremely low, fault scars can be traced most easily on oceanic floors.

Despite the presence of inconvenient obstacles, there still remain several principles according to which geomorphological elements can be used in tracing worldwide quasi-neotectonic lineaments: 1) sharpness of geomorphological lineaments, 2) regional continuity, 3) linkage of linear geomorphological lineaments to other point-type markers, 4) inter-regional altitude contrast, 5) abrupt changes in watercourse of larger rivers, 6) abrupt changes in shorelines, 7) abrupt changes in mountain ridges, 8) presence of extensional or contractional duplexes.

In order to map strike-slip lineaments of the world we constructed digital elevation models from SRTM data for Eurasia and Northern Africa; oceanic domains and the other parts of the world were approximated using Google Earth data.

Example:

Trascăului Mountains, which delimit the Transylvanian basin from west, belong to the Western Transylvanides and form an obducted tectonic unit (Săndulescu, 1984) of the Apuseni Mts. range, exhibiting an oceanic (ophiolitic) basement. The study area around the Piatra Secuiului Peak is made up from slope and shelf-margin deposits of an Upper Jurassic-Lower Cretaceous carbonate platform (Săsăran, 2006). Given the well-cemented and compacted nature of the sedimentary succession, weathering plays only a secondary role in shaping the landscape of the Trascăului Mountains, thus regional neotectonic lineaments can be recognized at the local scale as well (Fig. 11, 12). Local fault lineaments delineated in plain view by geomorphological techniques on the Google Earth topography can be identified on field as well.

Published in: Kovács, J.Sz., 2015 (in press), Elements of Global Strike-Slip Tectonics: a Quasi-Neotectonic Analysis, Journal of Global Strike-Slip Tectonics, v1., Szekler Academic Press, Sfintu Gheorghe.