For stratigraphic records in Geolex, we continue the established practice of assigning one or more "Geologic Provinces", to indicate roughly where the geologic unit is known to occur. A graphic of this province map is shown here; see References Cited to obtain a copy of the map (Meyer and others, 1991), which is published by the American Association of Petroleum Geologists.
Why do we use this map?
In 1968, the American Association of Petroleum Geologists Committee on Statistics of Drilling (AAPG-CSD) made available its first geologic provinces code map (Meyer, 1968) and published an explanatory text for the map (Meyer, 1970). Shortly thereafter, these provinces were adopted by the USGS Geologic Names Committee as a convenient indicator of the extent of geologic units. In Geolex, this practice is continued.
Background on the AASG Geologic Provinces map
"The [AAPG] Committee on Statistics of Drilling has prepared a code map of geologic provinces of the United States for use with automatic data processing. On this map the province boundaries are adjusted to county (parish) boundaries. The artificial geologic subdivision along such political boundary lines may be justified in several ways: (1) geologic features rarely coincide both areally and vertically through time and therefore the political boundaries of such features in many places approximate geologic boundaries; (2) a code for geologic provinces is needed to permit inexperienced personnel to assign the provinces from data, including wells, fields, and oil, gas, and brine analyses reported by county; (3) many states report data on oil production only by county; and (4) the geologic provinces code map is sufficiently accurate to indicate relative quantities of production, numbers of wells, or types of fluids among the principal producing areas. The code map is intended to discriminate between geologic positive and negative elements and to segregate these from purely physiographic features. The boundaries between provinces follow county, parish, and offshore area lines and, in the case of Alaska, topographic quadrangle lines. ... The map is frankly intended to emphasize geologic provinces with petroleum development or potential; therefore no effort has been made to subdivide such igneous and metamorphic provinces as the New England states." (From Meyer (1970))
"The map's offshore areas have been entirely redone using 1-degree x 2-degree UTM quadrangles. The geologic province boundaries are adjusted to follow geographic UTM quadrangle boundaries, just as onshore geologic boundaries follow county lines." (From Meyer and others (1991))
Meyer, R.F., ed., 1968, AAPG-CSD geological provinces code map: Association of Petroleum Geologists Bulletin, 1 sheet, scale 1:5,000,000.
Meyer, R. F., 1970, Geologic provinces code map for computer use: AAPG Bulletin, v. 54, no. 7, p. 1301-1305.
Meyer, R.F., Wallace, L.G., and Wagner, F.J., Jr., eds., 1991, AAPG-CSD geological provinces code map: Association of Petroleum Geologists Bulletin, v. 75, no. 10, p. 1644-1651, 1 sheet, scale 1:7,500,000.