Chattanooga Shale: geospatial geologic structural datasets in Tennessee

The Chattanooga Shale is relatively thin and generally continuous across the state, making it an important geologic horizon. In Tennessee, the Chattanooga Shale crops out along the escarpment between the Central Basin and the surrounding Highland Rim, in several river valleys and in folded areas outside the basin, and crops out around the Wells Creek, Howell, and Flynn Creek impact structures (Conant and Swanson, 1961). The Devonian-Mississippian-aged Chattanooga Shale is often abbreviated as "MDc.” Data related to the thickness, depth from land surface, and elevation of the unit are useful for resource exploration.
Information from 1,615 oil well and surface data points were used to produce the structure map on the Chattanooga Shale in Tennessee by the Tennessee Department of Environment and Conservation, Division of Geology (Moore and Horton, 1999). The data used in 1999 were acquired from previously drawn structure maps on the base of the Chattanooga Shale and compiled into computer-generated contour lines and maps. The original publication, Structure and isopach maps of the Chattanooga Shale in Tennessee, included three 84x57 cm maps, at an approximate scale of 1:500,000. The paper maps include a structure map on the base of the formation, an isopach map, and a location map of the data points representing wells used to prepare the original structure maps. The three maps associated with the original publication were digitized and rasterized for this project. 
The work for this project consisted of (1) scanning and georeferencing original paper maps to create georeferenced images (GRI), (2) digitizing well location points and contour lines, (3) populating well and contour attribute tables with data from maps and associated reports, and (4) interpolating raster surfaces for the top and bottom altitude, depth from land surface to the top and bottom surface, and thickness of the Chattanooga Shale in Tennessee. All raster surfaces were aligned to a modified version of the National Hydrogeologic Grid (Clark and others, 2018) to support USGS Lower Mississippi Gulf Water Science Center efforts to create a statewide hydrogeologic framework. All horizontal coordinated data are projected to NAD 1983 USGS Contiguous USA Albers. Raster vertical coordinate information was referenced to the North American Vertical Datum of 1988 (NAVD 88).
Dataset types can be identified by the following naming convention:
i_ = georeferenced map images (GRI)
po_ = points
c_ = contours and closed depressions
f_= faults and other structural features
p_ = extent polygon
ra_ = altitude raster
rd_ = depth from land surface raster
rt_ = thickness raster
The datasets included on this child item page are as follows:
chttshl_metadata.xml - metadata file     
chttshl_alldata.zip:
GRI/
i_chttshl_btm.tif - structure contour map of the bottom of the Chattanooga Shale (Moore and Wilson, 1999)
i_chttshl_data.tif - map of data used to create structure and isopach maps (Moore and Horton, 1999c)
i_chttshl_thk.tif - thickness contour map for the Chattanooga Shale (Moore and Horton, 1999b)
polygons/
p_chttshl_ext_ext.shp - study area extent for the Chattanooga Shale (Moore and Wilson, 1999)
p_hohenwald.shp - polygon for extend of the Hohenwald Platform (Moore and Horton, 1999b) - supplemental data
rasters/
ra_chttshl_btm.tif - altitude raster for the bottom of the Chattanooga Shale (NAVD 88) (meters)
ra_chttshl_tp.tif - altitude raster for the top of the Chattanooga Shale (NAVD 88) (meters)
rd_chttshl_btm.tif - depth from land surface raster of the bottom of the Chattanooga Shale (meters)
rd_chttshl_tp.tif - depth from land surface raster of the top of the Chattanooga Shale (meters)
rt_chttshl.tif - thickness raster for the Chattanooga Shale (meters)
vectors/
c_chttshl_btm.shp - structure contours for the bottom of the Chattanooga Shale (NGVD 29) (feet)
c_chttshl_btm_modified.shp - modified structure contours for the bottom of the Chattanooga Shale (hachures removed from closed basins). This vector used to interpolate raster for the bottom of the Chattanooga Shale. (NGVD 29) (feet)
c_chttshl_thk.shp - thickness contours for the Chattanooga Shale (feet)
c_chttshl_thk_modified.shp - modified thickness contours for the Chattanooga Shale (hachures removed from closed basins). This vector used to interpolate raster for the thickness of the Chattanooga Shale (feet)
f_chttshl_btm.shp - faults and other structural features mapped on the base of the Chattanooga Shale 
po_chttshl.shp - point data of altitude and thickness for the Chattanooga Shale (NGVD 29) (feet)
References:
Clark, B.R., Barlow, P.M., Peterson, S.M., Hughes, J.D., Reeves, H.W., Vigor, R.J., 2018, National-Scale Grid to Support Regional Groundwater Availability Studies and a National Hydrogeologic Framework, U.S. Geological Survey, ScienceBase data release, doi:10.5066/F7P84B24
Conant, L.C., and Swanson, V.E., 1961, Chattanooga Shale and related rocks of Central Tennessee and nearby areas, U.S. Geological Survey, Professional Paper 357. https://pubs.usgs.gov/publication/pp357.
Moore, J.L., and Horton, A.B., 1999, Structure and Isopach Maps of the Chattanooga Shale in Tennessee, Tennessee Dept. of Conservation, Division of Geology, Report of Investigations 48, 3 plates.

Tags: chattanooga-shale, contouring, earth-structure, elevation, geographic-information-systems, geology, geoscientificinformation, geospatial-datasets, inlandwaters, maps-and-atlases, natural-resource-exploration, stratigraphic-thickness, structure-contours, tennessee, usgs-6723b508d34e4f57573e8c82, water-resources
Organization: Department of the Interior