154 CONSTRUCTION SOURCES OF GRAVEL, MINTZER 
cretions and nodules of impure calcium carbonate known as kankar. Kankar is found in 
small granules like peas and some are larger that the human head. The older alluvium 
deposits have formed slightly elevated terraces, generally cut here and there by such 
rivers as the Beas, Ghaggar and Yummana. The valley sediments in places are found as 
deep as 20,000 feet in the Bengal Gangetic Delta and as shallow as 20,000 feet near the 
foothills of the Sewaliks. Detailed data is lacking concerning the depths of the various 
layers underneath the alluvial strata of the Gangetic Plains. It is believed by geologists 
that tertiary rock strata are present below the ailuvium. If these sediments cover similar 
strata, as in Assam, folded structures will be found [15]. 
In the study area near the Sewaliks a river terrace was investigated. In the Ghaggar 
river valley are relatively recently deposited terraces. Here layers were observed having 
textures ranging from large boulders to silts and clays. The alluvial materials were 
eroded from the surfaces of the Sewalik hills and then carried to the present sites by the 
drainage system. Where the water currents were swift, the carrying capacity was suf- 
ficient to move large erratics; but a decrease in rate of flow discharged these coarse 
materials not far from their source. Successively finer materials were deposited as the 
stream proceeded. Stratification, consisting of layers of different-sized particles, is com- 
mon in these alluvial deposits; such deposits are characterized by gravels, sands, silts 
and clays. 
The photo study was first done after the assembly of a mosaic. Aerial photography 
was procured for the study area through the Surveyor General, India. Observing the 
mosaic, each landform break was delineated by means of its distinct features. Foothills, 
terraces and river flood plain landforms were observed and outlined on the mosaic. A 
terrace formation was found situated a few miles East of Chandigarh. The elongated 
terrace spread some 30 to 50 square miles in a Northeasterly direction alongside of and 
being about a mile wide where the Ghaggar River has cut through. The surface is some 
30 to 50 feet above the present flood level of the river. The terrace formation had its 
own characteristics. The sharp face of the terrace adjacent to the river could be seen 
as an abrupt bluff standing some 20 to 30 feet above stream flood level. Then the foot 
of slope of foothill is observed and delineated. The drainage pattern change, as well as 
the topographic change of slope was easily seen as a clear-cut line on the photo mosaic. 
A detailed stereo study was made of the terrace to determine the pattern charac- 
teristics. The drainage characteristics for the terrace were observed to be those generally 
associated with granular soils, i.e., water percolated into the ground rather than formed 
run-off channels with eroding effect. Few, if any, streams actually crossed the terrace 
even though it was tilted slightly. Infiltration basins were seen as dark irregularly 
shaped splotches on the photo. Along the terrace face, near the Ghaggar river, gullies 
had formed with the usual V-shaped, steep gradients predominating, but in places a 
modified U-shaped gully was seen. These were found to be associated with hard indurated 
sediments at about 20 feet below the surface. The gray tone seen on the photos corre- 
sponded to that usually observed for gravelly areas. Corn and maize were the type of 
crops that are generally identified with these terrace soils. 
Results of the investigation. 
A site was selected for field exploration. The site was found at the village of Panch- 
koola to spot-check the presence, or absence, of granular materials. Engineers had al- 
ready tapped the site as a quarry for pit-run gravel. This site was not evident on the 
old photos. The gravel was found to be quite suitable for stabilized-gravel roads which 
were under construction at the Capital Site, Chandigarh, Punjab. The extent of the ter- 
race, however, did indicate there are other places in the area which could conveniently 
be tapped for the gravel supply. On careful field observation one saw the gravel to be in 
stratified layers, confirming the terrace to be of water-laid origin.