THE INTERPRETATION DILEMMA - COMPLEX LITHOSTRATIGRAPHIES IN THE ERA OF GIS: THE CASE OF THE INNER BLUEGRASS REGION OF KENTUCKY

A large amount of time, money, and manpower are invested in geologically mapping a state. The resulting geologic maps are considered the definitive source on the state's geology and widely used by professionals and lay people alike. The data upon which they are based were usually collected during extensive mapping efforts by the USGS and state agencies, but can be decades old. As research efforts continue and interpretations change, updating or revising the geologic maps is limited by financial constraints.

The lithostratigraphy of a study area is a keystone factor in many areas of geoscience research. However, the interpretations represented by the geologic maps are a product of the time of data collection, a snapshot in time. With the advent and broad implementation of GIS and 3D mapping, the need for data to be in digital form has become an expectation and desire. Old data often are already in digital form whereas newer data are not. A geoscience researcher must choose between either old interpretations supported by data that is readily available for use in GIS and 3D visualizations or more recent knowledge and interpretations whose underlying data are not in digital form.

Use of old data can lead to inherenly flawed analysis if updated interpretations are more accurate. However, this option is quick and can be inexpensive because the digital data are often already in a State-Agency-supported GIS. The data provide complete and seamless coverage of the study area and are based on information easily available to anyone who might want to apply the results of the research in a practical manner.

Performing the analysis based on much more recent interpretations leads to a more definitive and detailed scientific understanding. However, the required additional time, labor, and money to extract, manually digitize, and clean the analog data are real barriers to its use, and introduced errors are a real possibility. The newer data may not be spatially seamless or even cover the entire study area well so that spatial analyses and their applicability will be controlled by data distribution.

Issues and opportunities presented by the conflation of both older and more current lithostratigraphic data for the Inner Bluegrass region of Kentucky are major hurtles to be overcome for the purposes of 3D visualization and GIS spatial analysis.