Neotectonic Indications from the Western and Southern Deserts of Iraq

The Iraqi Western and Southern deserts are part of the Iraqi Stable Shelf (Inner Platform) that belongs to the Arabian Plate. Therefore, both deserts lack tectonic forms like folds and faults;however, very rarely faults and regional lineaments can be seen in both deserts. Although both deserts are tectonically stable, tens of Neotectonic indications can be seen everywhere in both deserts. Among those indications are: Straight valleys, perpendicular valley bendings, sinkholes aligned along straight lines, dislocated valleys, knickpoints within valleys aligned along straight lines, regional lineaments, anomalous valley shapes, trends, and types, dissected alluvial fans. We have used existing geological maps of different scales and Esri World Imagery to recognize those Neotectonic indications. All those recognized features are excellent indications that both the Iraqi Western and Southern deserts are tectonically not stable. Accordingly, new terminology is suggested instead of the Stable Shelf (Inner Platform) which is the “Less Disturbed Shelf”.

Recent tectonic activity in Central Alborz Mountain,Iran:morphometric analysis and knickpoint identification

Alborz,as part of the Alpine-Himalayan orogeny belt,has been the result of the convergence of the Central Iranian and Eurasian plate since the late Triassic.The study area located in Central Alborz encompasses different Quaternary faults.Thus,the present study aimed to evaluate the effect of faults on river landforms through morphotectonic indices and the causes of knickpoints and knickzones in the Bedrock Rivers in part of Central Alborz.To this end,six morphometric indices such as longitudinal gradient(SL),hierarchical anomaly(Δα),the bifurcation index(R),hypsometric integral and hypsometric curve(Hi-Hc),relative relief(Bh),and basin shape(Bs) were calculated and analyzed in38 sub-basins of the area.Finally,the area was divided into extremely high,high,medium,and low tectonic activity areas using the relative tectonic activity(IAT).Normalized steepness and concavity indices along with the longitudinal profiles of the streams were obtained using Matlab and Arc GIS software.Based on the findings,the existence of slope-break knickpoints at the mountain piedmont at the outlet of large rivers through active faults demonstrated that most of these landforms were created by movements along the main faults such as Khazar,Nusha,Soheil,Deylaman,Kashachal,representing high tectonic activity in the central and southern parts of the study area.However,the values of these indices were extremely low and indicated low tectonic activity in the northern parts located in the embayment part of the Caspian Sea.Finally,the findings revealed that these classes correspond well to the areas with landforms such as V-shaped and narrow valleys,gorges,deflected and offset streams,deformed Neogene,and Quaternary units that indicate the post-Neogene activity.

Application of River Longitudinal Profile Morphometrics to Reveal the Uplift of Lushan Mountain

The stream power model was applied to Lushan Mt. in South China in order to verify its capability of interpreting the uplift of a small block mountain. On a log-log plot, the longitudinal profiles of 9 rivers derived from a 30 m DEM exhibit primary characteristics similar to those derived from a 5 m DEM; however, the 5 m DEM clearly reveals more minor knickpoints, and the positions of knickpoints are pinpointed more accurately. All of the studied rivers on the block mountain are in a transient state due to geological perturbations. Some of them exhibit two segments in steady state separated by a slopebreak knickpoint. Such rivers generally develop in a longitudinal valley, which are less perturbed by substrate inhomogeneities. The similar heights of the slope-break knickpoints and the similar uplift rate indicated by the k_（sn） values demonstrate an almost simultaneous headward erosion induced by the fall in base level. This modelling result is consistent with the mode of formation of this particular block mountain. Our study demonstrates that the stream power model is applicable to a small tectonicallyactive massif only if the channel segments are in a steady state.

Stability Analysis of Cliff Face around Kegon Falls in Nikko, Eastern Japan: An Implication to Its Erosional Mechanisms

A waterfall highlights the locus of active fluvial erosion of bedrock, and its mechanism has been the subject of several studies;however, erosional processes remain to be clarified for specific rock structures composing a waterfall. Herein, the detailed morphology of cliffs around a waterfall is examined by a terrestrial laser scanning (TLS) approach to analyze erosional processes occurring in the cliffs. The study site is Kegon Falls in Japan, which has a vertical drop of surface water from the top of its cliff and groundwater outflows from its lower portion. The entire cliff is mostly overhanging and minor rockfalls are often observed. The latest major rockfall occurred in 1986, causing an approximate 8-m upstream shift of the waterfall lip. From the point cloud obtained by TLS measurement, a digital elevation model on a vertical plane was generated, and cross-sectional profiles were extracted. A distinct 5- to 10-m depression was found at the bottom of the upper andesite layer of the waterfall cliff, which appears to have been formed by freeze-thaw and wet-dry weathering following the upstream shift of the surface water drop. Stability analysis of the waterfall cliff with an undercutting notch indicates that the igneous rock composing the cliff is sufficiently strong to maintain its current overhanging shape and that catastrophic collapse of the entire waterfall face rarely occurs. Following the formation of the depression, the upper cliff face appears to have been gradually eroded by gravitational collapses of relatively small blocks bounded by columnar and platy joints.

Regional- to local-scale controls on waterfalls in Rocky Mountain National Park,Colorado

Previous work on the eastern side of Rocky Mountain National Park(RMNP),Colorado indicated correlations among waterfall location,waterfall morphology,and the characteristics of bedrock joints.Characteristics of waterfalls on the western side of the national park do not correlate as strongly with joint geometry.Longitudinal river profiles on the western side are less concave and waterfalls account for a greater proportion of the total elevation loss.We interpret these differences to result from more widely spaced joints,lithological differences,and complex glacial history.These results demonstrate that waterfall shape and typology may change due to both local and regional controls operating in a mountain region.Both regions had alpine valley glaciers,but continued landscape evolution via fluvial erosion has developed waterfalls with diverse locations and morphologies that reflect the influences of glacial deposits,bedrock erosional resistance,and joint geometry.