Techniques for assessing sand and gravel resources in glaciofluvial deposits : an example using the surficial geologic map of the Loudon Quadrangle, Merrimack and Belknap counties, New Hampshire

A method for estimating the sand and gravel resources in glaciofluvial systems has been developed based on surficial mapping techniques that use the morphosequence concept and geographic information systems (GIS). Two different strategies are used to estimate gravel resources. One strategy estimates the sand and gravel resources contained in esker deposits; the other, which is more dependent on GIS, estimates resources in non-esker deposits. An attempt has been made to determine which deposits are sterilized; that is, those beneath the water table, adjacent to streams or roads, or encroached on by urbanization. Preliminary estimates using these methods indicate that about 158,000,000 m 3 (206,000,000 yd 3 ) of sand and gravel are present in the Soucook River valley part of the Loudon, N.H., 7.5-minute quadrangle. About 64,500,000 m 3 (84,400,000 yd 3 ) of these materials are in deposits above the water table. About 26 percent of the sand and gravel resources above the water table are unlikely to be mined because they have been sterilized. Of the remaining resources, 479,000 m 3 (627,000 yd 3 ) of gravel and 1,120,000 m 3 (1,460,000 yd 3 ) of sand are in esker deposits, and 9,400,000 m 3 (12,300,000 yd 3 ) of gravel and 38,300,000 m 3 (50,100,000 yd 3 ) of sand are in stratified non-esker deposits. With the addition of new well data, newer and more accurate estimates are possible.