Wadi Fatima Thin-Skinned Foreland FAT Belt: A Post Amalgamation Marine Basin in the Arabian Shield

Abstract

Wadi Fatima fold-thrust (FAT) belt is a distinctive foreland FAT belt in the Arabian-Nubian Shield (ANS) involving unmetamorphosed to slightly metamorphosed sedimentary sequence of Fatima Group, deposited over a metamorphic/igneous basement, comprising ortho-amphibolites, orthoand para-schists (with chaotic unmappable blocks of marbles, pyroxenites and metagabbros), older granite (773 ± 16 Ma) and younger granite. The basement exhibits structural fabrics, such as attenuated tight isoclinal folds, sheared-out hinges, NE-SW penetrative foliation and subhorizontal stretched and mineral lineations, related to an oldest prominent dextral shearing phase affected the main Wadi Fatima during the Neoproterozoic. In Wadi Fatima FAT belt, the style of deformation encompasses flexural-slip folding forming mesoscopicand map-scales NE to ENE plunging overturned antiforms and synforms, and a thrust duplex system bounded by floor thrust and sole thrust (basal detachment) dipping gently towards the hinterland (SE to SSE direction) and rises stratigraphically upwards towards the foreland. Such style is affiliated to thin-skinned deformation. Several lines of evidence, such as geometry of interacting outcropand map-scale folds and thrusts, patterns of thrust displacement variations and indications for hinge migration during fold growth, strongly suggest that folding and thrusting in Wadi Fatima FAT belt are geometrically and kinematically linked and that thrusting initiated as a consequence of folding (fold-first kinematics). Thrusts frequently show flat-ramp-flat geometry, and every so often give an impression that they are formed during two main sub-stages; an older sub-stage during which bedding sub-parallel thrusts were formed, and a younger sub-stage which generated younger ramps oblique to bedding. Thrust ramps with SE to SSE dipping regularly show sequential decrease in dip or inclination (due to piggy-back imbrication) into their transport direction which is proposed to be towards NW to NNW. Evidence indicating this transport direction of Wadi Fatima FAT belt embrace NW to NNW oriented stretching lineations recorded along thrust planes, NW to NNW folding vergence, and diminishing of the intensity of deformation and thrust stacking and imbrication from SE to NW; <i>i.e.</i> from hinterland to foreland. The tectonic transport vector is congruent with the mean orientation of slickenline striae formed by layer-parallel slipping along folded bedding planes. The mean orientation of slickenline lineations, after their host beds were rotated to horizontal about their strikes, is found to be N25°W - S25°E. Two tectonic models are proposed to unravel the structural history of the study area and to illustrate the tectonic evolution of Wadi Fatima FAT belt which represents one of interesting foreland FAT belts recorded worldwide. In the first model, the area was evolved from dextral shearing during the early convergence and amalgamation between East and West Gondwana, to emplacement of the older granite during a period of c...

Natural Hazard Assessment in Western Saudi Arabia using Remote Sensing and GIS Methods

“…Of course, there is a need to verify these features in the field. These linear features could be partly correlated with known larger shear zones such as the Wadi Fatima shear zone [31]. Examples of the visibility of these traces are shown in the next figures (Figures 8-10).…”

Volcanosedimentary Basins in the Arabian-Nubian Shield: Markers of Repeated Exhumation and Denudation in a Neoproterozoic Accretionary Orogen

“…The carbonates are well bedded ( Figure 21A) and show abundant microbial lamination ( Figure 21B). Carbonates from the lower Muraykhah formation were likely deposited in relatively deep water, whereas the upper Muraykhah formation carbonates include rippled and crossed-bedded dolarenites, implying a shallow depositional setting [90]. Stromatolites have been described [92,93], but are relatively rare.…”

“…Other mixed terrestrial and shallow-marine Ediacaran basins include the Fatimah group [90,91] and Ablah group [22,23]. The Jibalah Group was formally recognized and defined during the 1960s [92,93].…”

Remote Sensing and GIS Contribution to a Natural Hazard Database in Western Saudi Arabia

“…The origin of this parallel, linear arrangement might be complex and has to be discussed and to be further investigated: Reasons among others might be a) compression of the subsurface, b) traces of uplift, c) traces of parallel longitudinal dunes underneath the younger eolian covers, linear wind erosion, and flash flood sediments? Due to the rifting processes in the Red Sea and the movements of the Arabian Plate towards NE with velocities of about 10 to 15 mm/year, it seems most likely that the parallel alignment of linear features is related to compression [13,38,39].…”