Salt domes are listed alphabetically by State and then by area of salt dome occurrence in table 2 (at back of report). The distribution of salt domes among the areas is shown in figure 13. A code has been used in table 2 to show which references identified and mapped each entry as a salt dome. Specific data about each of the 624 domes was included in table 2 wherever available, including: depth to caprock and depth to salt (Anderson and others, 1973; Halbouty, 1979; Jackson and Seni, 1984; ‘and Stipe, 1960, 1962, 1980). When depth discrepancies occurred between sources the shallowest depth and generally the latest source was used. Size of the domes is shown by diameter of dome top (Anderson and others, 1973; Stipe, 1960, 1962, 1980) and the volume of salt above a depth of 10,560 feet, the presumed depth of what is termed "mother salt" in Halbouty (1979, tables 8-3 through 8-8).
The volume of salt is a more accurate measurement of dome size than diameter, because diameter can vary greatly with depth. Mature, piercement salt structures may contain most of their salt at shallow depths with the cross sectional area of the dome decreasing with depth. Less mature salt structures are found at greater depths and usually have a mounded shape so that their cross sectional area increases with depth. A depth of 10,000 feet represents the delineation between intermediate and deep salt structures in the classification of Halbouty (1979), but in Jackson and Seni (1984) 10,000 feet seems to be the cutoff between salt diapirs (piercement structures) and salt pillows (less mature, nonpiercement structures).
The land-surface or sea-bottom altitudes in table 2 are approximations. Landsurface altitudes at -salt domes were estimated by interpolation from a uniform grid of altitudes spaced at 5-mile intervals. Onshore, each altitude in the grid was the average of about 90 points uniformly spaced at intervals of 30 seconds of latitude and longitude. The data set and the method used is described more fully by Williams and Williamson (1989, p. 335-336). The original data was recorded in meters, so the resolution is at least 3 feet. That is why land-surface altitude at so many salt domes near the coastline is shown as 3 feet. The grid values of sea-bottom altitude were estimated by computer contouring about 100 data points at oil wells.