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About KGS Stratigraphic Formation Tops

Interpreted stratigraphic "tops" from Kentucky Geological Survey investigators and research projects are now available via the oil and gas record search page:
You can limit the results by records with stratigraphic tops, view and download tops for a specific well, or download tops for all the returned records (by page of results).

A stratigraphic top (also known as a "borehole lithology intercept") is an interpretation ("pick") by a geologist of the depth to the top or bottom of a stratigraphic horizon in a borehole using geophysical, lithologic, or other data from well logs. The data provided here are derived from Kentucky Geological Survey oil and gas record data, and can either be viewed and downloaded for each well, or downloaded for a set of returned wells.

Some notes about these data:
  • In the data you will find that some investigators solely picked the top of a horizon and the base was not interpreted.
  • Not all wells for which tops are available have stratigraphic data picked from surface to total depth. Additionally, we report only the base of the formation encountered at the surface (i.e., top is not available) and only the top of the formation encountered at total depth (i.e., base is not available).
  • There may be several tops recorded for the same horizon by different workers from different sources.
  • There may be some overlap or repetition of information. For example: in the data for a well, there may be a pick for the top of the New Albany shale and also picks for the top of each the Grassy Creek, Sweetland Creek, and Blocher shales (which are contained within the New Albany).
The data includes a stratigraphic code for each interpreted horizon, and a complete listing of stratigraphic codes and their use is available at

These data are distributed "as is" with no assurances as to accuracy or completeness. The Kentucky Geological Survey makes no warranties either express or implied and the user of the data assumes all liability for damages incurred through the use or misuse of the data.

If you have questions, comments, or suggestions, please contact Carrie Pulliam at the Kentucky Geological Survey (phone: 859.323.0543 or email:

Data Field Explanation for Stratigraphic Tops Interpretations:
Data Item
(download header name)
Currently the only available type is "Stratigraphic". If you are interested in "Interval" tops, please contact KGS.
record_number Download only: oil and gas record number
Stratigraphic Name
Full stratigraphic name of the picked horizon.
pick_fm_kgscode Download only: alpha-numeric formation code used to designate the picked horizon. A complete listing of stratigraphic codes and their use is available at
Strat Code
Seven (7)-digit formation code used to designate the picked horizon (used for sorting horizons). A complete listing of stratigraphic codes and their use is available at
Top Depth (ft)
Interpretation of the drilling depth in feet to the top of the formation picked.
Bottom Depth (ft)
Interpretation of the drilling depth in feet to the base of the formation picked.
Datum (ft)
Supplied for adjusting the top and base supplied to an elevation with respect to sea level. Specifically it is the difference between ground level and a permanent datum such as the "Kelly bushing", "rig floor", etc. If the DATUM field is blank, it is suggested that the user check the elevation on the well's DjVu documents to ensure the correct depths are determined.
Primary Litho
Primary lithology of the picked horizon.
Secondary Litho
Secondary lithology (if applicable and available) of the picked horizon.
Fluid show information
KGS geologist or project that provided the pick interpretation.
Source of the data used to determine the tops:
Common abbreviations for sources are:
DLDriller's log
STScout Ticket
ELElectric Log (sometimes abbreviated as "ELOG" or using the standard elog type abbreviations: SPR, GRN, etc)
SDRSample Description
Some special sources are:
SPINDLETOPMcGuire, W., and Howell, P., 1963, Oil and Gas Possibilities of the Cambrian and Lower Ordovician in Kentucky : Spindletop Research Center, Lexington, KY, various paging (out of print).
SDR-HSindicates data is from a sample description by Howard Schwalb.
SDR-LBFindicates data is from a sample description by Louise B. Freeman.
Date Added
Date the data was added to KGS database.
Additional comments from interpreter.
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