An important component to understanding groundwater is to study the geologic formations that comprise the aquifers where groundwater resides or the confining units that inhibit groundwater movement. This is accomplished by creating wells logs from examining the samples collect during the drilling of wells. Geologists can analyze the samples to determine the lithology, mineralization, geologic structures, and aquifers the well penetrates.
For more than a century, the most detailed source of subsurface geologic information in Missouri has been the well logs files maintained by the department. Beginning in the early 1900s, MGS struck an informal agreement with the fledgling drilling industry. Drillers would collect and save samples of the rock cuttings from wells each five feet of drilling then send them to MGS where geologists would examine them microscopically, and produce a graphic log of the well that illustrated the geologic data gleaned from the cuttings, along with location, production and well construction information.
Today, logs exist for more than 28,000 wells. Not every well that has been drilled in Missouri has been logged, as there have been several hundred thousand wells drilled over the years. Approximately 3,000 new water wells are drilled every year.
Well logs, cuttings and cores are housed at the department's McCracken Core Library and Research Center. The facility contains nearly 8 million feet of geologic subsurface material that is made available to anyone interested in the subsurface geology of the state. Contact us to schedule a visit.
Well logs contain geologic, stratigraphic and groundwater information.
- Well Drilling Logs Viewer – Use this ArcGIS web application to display and download well logs and related data.
- GeoSTRAT – Use this ArcGIS web application to display and download well logs and related data. Select “Well Logs” from the list of layers on the left side of the interface and zoom in until they are displayed, or search for an address.
- Geologic Well Log Symbol Key and Descriptions - PUB2932.
Handsamples and Thin Sections
More than 1,300 handsamples and nearly 1,100 thin sections are stored in our repositories. Specimen locations and other information about each sample are included in the database.
Locations, lithologies and stratigraphic units of outcrops from publications and field notebooks created by our geologists, as well as publications by authors across Missouri are included in the database.
Core and Cuttings
Database of core and cuttings maintained at the department's McCracken Core Library.
Precambrian Drillhole Information – Operation Basement
This department database features select Missouri Precambrian drillhole information for continued interpretations of Missouri’s crystalline basement. The database may be downloaded from the U.S. Geological Survey’s Operation Basement webpage.