Rhine Graben rift system-related multi-junction and other analogs: Large-scale circular lithospheric segmentation indicated in regional topographic and hydrographic data

Many rift-related triple-junctions from various geological periods have been previously investigated worldwide. Some of these large extensional lithospheric phenomena even involved complex circular configurations composed of numerous omnidirectionally spaced radial and arcuate elements, thereby having a general multi-junction character. Although pointing to close association of horizontal plate kinematics with centrally directed vertical updoming as two conjugated significant geodynamic phenomena, such annular dichotomy of features penetrating and segmenting the surrounding upper Earth's mass has yet been addressed only poorly.

Based on spatial analysis of regional topography and/or hydrography, an extensive Cenozoic circular structure (> 6,000 km in diameter) even including recently active tectonic elements appears to have developed in whole Europe and some adjacent areas of Africa and Asia centred at a common intersection point of the Upper Rhine Graben, Lower Rhine grabens (with significant Roer structure), Hessian grabens (involving Leine structure), and more distant Eger Graben current axes. The pervasive surface fracturing of both higher / lower topographic levels was taken into account (numerous concentric boundaries between mountain summit blocks visualized by closed contours / ubiquitous multi-arc- and fan-shaped geometries within piedmonts and lowlands indicated in continental river network, less along important block-bounding slopes, and locally on sea floor). The fairly regular annular lithospheric fragmentation is expressed by a wide-scale spectrum of features from general mountain or basin belt orientations through trends of circumferential, centrifugal, or centripetal river sections and corresponding valleys to consistent sets of sharp stream bends.

Using a similar research approach, several analogous circular phenomena were detected within the Red Sea rift system. Despite possible links to various known geometrically consistent geological structures including magma plumbings or mantle plumes, it is yet hard to determine the main evolutionary processes and the closer time constraints of the circular systems. Their role should be considered and discussed on a broad disciplinary basis, among others, because similar surface configurations seem to exist in different tectonic settings such as large uplifting basement massifs or arcuate orogenic belts and intermontane basins. An attempt to invoke related communication is made also by means of this contribution.