Missouri Department of Natural Resources
Division of Geology and Land Survey
Geological Survey Program
P. O. Box 250
Rolla, Missouri 65402
Telephone: (573) 368-2147
Fax: (573) 368-2111
e-mail: nrmiddm@mail.dnr.state.mo.us
Geologic mapping, through U. S. Geological Survey STATEMAP and Missouri Department of Natural Resources' general revenue funding, began on the Table Rock Lake, Missouri 30' x 60' quadrangle in 1993 on two 7.5' quadrangles. In the four succeeding years, mappers and map areas increased to a total of eighteen 7.5' quadrangles of the total 32 for the study area. The remaining 7.5' quadrangles had previously been published or had a sufficient reliability (enough control data to present geologic map interpretation at a specific scale; Robertson and Middendorf, 1999) to open file the Table Rock Lake quadrangle compilation at 1:100,000-scale.
It was not until the last round of geologic mapping that ArcView was used to digitally compose the geologic data. Prior to 1997, geologic data was hand drawn by the geologist on screened mylar, and an open file layout of the map area was cut and pasted together to be run through a blue-line printer. ArcView allows a project file for each quadrangle map area to be created, with all the elements organized within the project folder. Bedrock exposures can be more faithfully depicted as to their location and extent, and attributes directly linked with these shapefiles. Support data includes bedrock outcrops, surficial material sites, structural features, water well, spring and stream data, walking and road traverses, lineament and aerial photographic studies, and any other geologically related information that makes the bedrock and surficial material interpretations more reliable.
Shapefiles for all 32 quadrangles were individually composed, either directly through ArcView or converted from .dxf files from digitized mylar copies. Discrepancies in linework between adjacent quadrangles mapped by different authors at different times makes for some compunctious editing bouts, as well as mapping composed on differing topographic bases, non-uniform map units, and quality control relating to digitizing techniques. It had been noticed that "puck" digitizing is relatively quick, but has low quality results - for example, poor line depiction at larger-scales. Recently our older maps have been scanned, which in turn can be geo-referenced, placed in a view and "heads-up" digitized with much better results. The individual quadrangles were compiled into the Table Rock Lake quadrangle, boundaries edgematched, and a layout composed of the bedrock geologic map, sources of mapping, correlation of map units and descriptions of map units and structural features.
Compiling geologic mapping at 1:100,000-scale on 30' x 60' quadrangle map areas is a great means of regionally presenting this data. Larger-scale, highly control-supported geologic mapping is offered as 1:24,000-scale digital files by the Missouri Division of Geology and Land Survey.
Robertson, C. E. and Middendorf, M. A, 1999, Geologic mapping standards for Missouri: Missouri Department of Natural Resources, Division of Geology and Land Survey, working document.