Reprint - Central Arid Zone Research Institute

flows westward. Detailed studies indicate that the terraces are notvery wide, but still preserve some of the surficial distinguishingmarks of the former stream courses on them, which suggest therecency of the terrace formation. A hypothetical evolutionaryscheme has been put forward for the terraces on the basis of theirmorphology and stratigraphy. It has also been suggested that neotectonicactivities have taken place along a series of faults in thisregion, which were responsible for the formation of terraces alongthe Somesar and some other rivers in the Aravalli foot-hills.96 Kar, A. (1984)Morphology and evolution of some sandstone pediments inRajasthan desert. Geographical Review of India. 46: 67-74Studies conducted on some pediments, formed on the Vindhyansandstone, reveal that minor variations in the rock's character havesignificant influence on both the morphology and evolution of thosepediments. The slope angle and profile form of the pediments, thecharacteristics of the coarse debris, and the drainage characteristicshave been found to change with the changes in the rock character.Chemical weathering seems to be a major process of sedimentationat one of the sites, while at other definite proofs are lacking.97 Kar, A. (1987)Origin and transformation of longitudinal sand dunes in the Indiandesert. Annals of Geomorphology. 31: 311-337Longitudinal dunes of the Indian desert did not originate from theparabolic dunes. Their genesis and evolution are linked with theaerodynamic system prevailing over the region and topographicpeculiarities. In the main field they form from the coalescence ofbarchan forms and the transition from the longitudinal to the ofparabolic shape is also governed by the changes in the aerodynamicpattern. The Taylor-Gortlar vortices pattern used by Wilson in hismodel of dune evolution explains well the situation here. Gradualtransformation of longitudinal dune shape to parabolic shapethrough systematic changes in form over space indicates a commongenetical link for both the types.98 Kar, A. (1988)Possible neotectonic activities in the Luni-Jawai plains, Rajasthan.Journal of the Geological Society of India. 32: 522-26The present disorganised state of many streams in the Luni-Jawaiplains of western Rajasthan has been attributed to a shift to an aridclimate. The satellite images of the area, however, indicate anumber of lineaments across the plains. Most cases of drainagedisappearance appear related to these lineaments, as also the