Post-Eocene (predominantly Pliocene) continental sedimentary rocks of the Sacramento Valley, CA are up to 1,200 m thick beneath the valley. These rocks contain most of the fresh ground water in the valley, forming a key component of the total water budget for the valley. A 1974 study by the U.S. Geological Survey was an early attempt to develop detailed knowledge of the subsurface geology of the Sacramento Valley. The study delineated the configuration of the base post-Eocene continental sedimentary rocks of the Sacramento Valley and mapped the thickness of those deposits. This digital dataset contains spatial datasets corresponding to the contoured base and thickness of the post-Eocene continental sedimentary rocks as mapped by the U.S. Geological Survey's study of the Sacramento Valley. The structure contour and thickness maps were digitized and attributed as GIS data sets so that these data could be used in digital form as part of U.S. Geological Survey and other studies of the basin.

The Upper Colorado River Basin has a drainage area of about 113,500 square miles in western Colorado, eastern Utah, southwestern Wyoming, northeastern Arizona, and northwestern New Mexico. In the 1980’s and 1990’s, the Upper Colorado River Basin was a study area under of the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) program (Sun and Johnston, 1994; Sun and Weeks, 1991). The objectives of the RASA program for the Upper Colorado River Basin were to provide regional assessments of major aquifer systems by providing quantitative assessments of the occurrence, movement, and availability of water stored in rock formations that underlie the basin/watershed. These assessments included: (1) the classification of stratigraphic sequences into those intervals that constitute aquifers and those that constitute confining beds; and (2) the generation of maps that portrayed the areal extent of aquifers, aquifer thickness, and overburden thickness. These studies generated a large body of subsurface geologic information as part of the regional aquifer analyses, some of which are captured in this digital data release. Aquifer systems in consolidated rocks in the Upper Colorado River Basin have been grouped into three major subdivisions of sedimentary rocks; in descending order: (1) Tertiary-rock aquifers, (2) Mesozoic-rock aquifers, and (3) Paleozoic-rock aquifers (Taylor and others, 1983; 1986). Within each aquifer group, rocks are further divided into aquifers and confining units on the basis of lithology, depositional environment, and hydrologic characteristics (Glover and others, 1998; Freethy and Cordy, 1991; Geldon, 2003). In a report describing consolidated-rock aquifers of Paleozoic age, 7 hydrostratigraphic units were defined, four aquifers and three confining units (Geldon, 2003). The hydrostratigraphic units of Paleozoic age are locally exposed around the margins of uplifts and in deeply-incised canyon; they occur widely in the subsurface of the Upper Colorado River Basin study area, except in parts of the Uinta, Wind River, and Uncompahgre uplifts where they have been removed by erosion. These hydrostratigraphic units are part of the stratigraphic sequence of Paleozoic rocks that has a total thickness of more than 5,000 ft. This digital dataset contains spatial datasets corresponding to the contoured subsurface maps of Paleozoic rock units produced by the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) of the Upper Colorado River Basin (Geldon, 2003). The data define the thickness, extent, nomenclature, and facies characteristics of principal hydrostratigraphic units of Paleozoic age in the basin. The digital data describe the following hydrostratigraphic units: the Flathead aquifer, the Gros Ventre confining unit, the Bighorn aquifer, the Elbert-Parting confining unit, the Madison aquifer (consisting of two zones, the Redwall-Leadville zone, and the Darwin-Humbug zone), the Four Corners confining unit (consisting of the Belden-Molas subunit and the Paradox-Eagle Valley subunit), and the Canyonlands aquifer (consisting of three zones, the Cutler-Maroon zone, the Weber-de Chelly zone, and the Park City-State Bridge zone). Contoured thickness and lithology data for each unit are contained in line features classes within a geodatabase; unit extents, facies extents, and formation nomenclatural extents are represented as polygon feature classes. Both types of data are also saved as individual shapefiles. Nonspatial tables define the data sources used, terminology, and the stacking hierarchy and component geologic formations of each the of hydrostratigraphic units

The Upper Colorado River Basin has a drainage area of about 113,500 square miles in western Colorado, eastern Utah, southwestern Wyoming, northeastern Arizona, and northwestern New Mexico. In the 1980’s and 1990’s, the Upper Colorado River Basin was a study area under of the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) program (Sun and Johnston, 1994; Sun and Weeks, 1991). The objectives of the RASA program for the Upper Colorado River Basin were to provide regional assessments of major aquifer systems by providing quantitative assessments of the occurrence, movement, and availability of water stored in rock formations that underlie the basin/watershed. These assessments included: (1) the classification of stratigraphic sequences into those intervals that constitute aquifers and those that constitute confining beds; and (2) the generation of maps that portrayed the areal extent of aquifers, aquifer thickness, and overburden thickness. These studies generated a large body of subsurface geologic information as part of the regional aquifer analyses, some of which are captured in this digital data release. Aquifer systems in consolidated rocks in the Upper Colorado River Basin have been grouped into three major subdivisions of sedimentary rocks; in descending order: (1) Tertiary-rock aquifers, (2) Mesozoic-rock aquifers, and (3) Paleozoic-rock aquifers (Taylor and others, 1983; 1986). Within each aquifer group, rocks are further divided into aquifers and confining units on the basis of lithology, depositional environment, and hydrologic characteristics (Glover and others, 1998; Freethy and Cordy, 1991; Geldon, 2003). In a report describing consolidated-rock aquifers of Paleozoic age, 7 hydrostratigraphic units were defined, four aquifers and three confining units (Geldon, 2003). The hydrostratigraphic units of Paleozoic age are locally exposed around the margins of uplifts and in deeply-incised canyon; they occur widely in the subsurface of the Upper Colorado River Basin study area, except in parts of the Uinta, Wind River, and Uncompahgre uplifts where they have been removed by erosion. These hydrostratigraphic units are part of the stratigraphic sequence of Paleozoic rocks that has a total thickness of more than 5,000 ft. This digital dataset contains spatial datasets corresponding to the contoured subsurface maps of Paleozoic rock units produced by the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) of the Upper Colorado River Basin (Geldon, 2003). The data define the thickness, extent, nomenclature, and facies characteristics of principal hydrostratigraphic units of Paleozoic age in the basin. The digital data describe the following hydrostratigraphic units: the Flathead aquifer, the Gros Ventre confining unit, the Bighorn aquifer, the Elbert-Parting confining unit, the Madison aquifer (consisting of two zones, the Redwall-Leadville zone, and the Darwin-Humbug zone), the Four Corners confining unit (consisting of the Belden-Molas subunit and the Paradox-Eagle Valley subunit), and the Canyonlands aquifer (consisting of three zones, the Cutler-Maroon zone, the Weber-de Chelly zone, and the Park City-State Bridge zone). Contoured thickness and lithology data for each unit are contained in line features classes within a geodatabase; unit extents, facies extents, and formation nomenclatural extents are represented as polygon feature classes. Both types of data are also saved as individual shapefiles. Nonspatial tables define the data sources used, terminology, and the stacking hierarchy and component geologic formations of each the of hydrostratigraphic units

The San Juan basin is a significant physical and structural element in the southeastern part of the Colorado Plateau physiographic province. The San Juan basin is in New Mexico, Colorado, Arizona, and Utah and has an area of about 21,600 square miles. The basin is about 140 miles wide and about 200 miles long. In the 1980’s and 1990’s, the U.S. Geological Survey's Evolution of Sedimentary Basins—San Juan basin study produced several reports on aspects of the stratigraphy and sedimentology of the basin. A report of the stratigraphy, structure, and paleogeography of Pennsylvanian and Permian rocks included 18 plates of contoured elevation and thickness data for various units (Huffman and Condon, 1993). This digital dataset contains spatial datasets corresponding to selected contour maps from the Evolution of Sedimentary Basins—San Juan basin study. The data help define the elevation, thickness, and extent of principal stratigraphic units of the basin. The digital data describe the following stratigraphic units: the Molas Formation, the Rico Formation, the elevation of the top of Permian strata, and the estimated thickness of Permian and Pennsylvanian rocks. Digital data for each unit are contained in individual features classes within a geodatabase (also saved as individual shapefiles). Feature classes have a single attribute, either elevation or thickness, that represents the contoured value. Contoured values are given in feet, to maintain consistency with the original publication, and in meters.

The San Juan basin is a significant physical and structural element in the southeastern part of the Colorado Plateau physiographic province. The San Juan basin is in New Mexico, Colorado, Arizona, and Utah and has an area of about 21,600 square miles. The basin is about 140 miles wide and about 200 miles long. In the 1980’s and 1990’s, the U.S. Geological Survey's Evolution of Sedimentary Basins—San Juan basin study produced several reports on aspects of the stratigraphy and sedimentology of the basin. A report of the stratigraphy, structure, and paleogeography of Pennsylvanian and Permian rocks included 18 plates of contoured elevation and thickness data for various units (Huffman and Condon, 1993). This digital dataset contains spatial datasets corresponding to selected contour maps from the Evolution of Sedimentary Basins—San Juan basin study. The data help define the elevation, thickness, and extent of principal stratigraphic units of the basin. The digital data describe the following stratigraphic units: the Molas Formation, the Rico Formation, the elevation of the top of Permian strata, and the estimated thickness of Permian and Pennsylvanian rocks. Digital data for each unit are contained in individual features classes within a geodatabase (also saved as individual shapefiles). Feature classes have a single attribute, either elevation or thickness, that represents the contoured value. Contoured values are given in feet, to maintain consistency with the original publication, and in meters.

The Upper Colorado River Basin has a drainage area of about 113,500 square miles in western Colorado, eastern Utah, southwestern Wyoming, northeastern Arizona, and northwestern New Mexico. In the 1980’s and 1990’s, the Upper Colorado River Basin was a study area under of the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) program (Sun and Johnston, 1994; Sun and Weeks, 1991). The objectives of the RASA program for the Upper Colorado River Basin were to provide regional assessments of major aquifer systems by providing quantitative assessments of the occurrence, movement, and availability of water stored in rock formations that underlie the basin/watershed. These assessments included: (1) the classification of stratigraphic sequences into those intervals that constitute aquifers and those that constitute confining beds; and (2) the generation of maps that portrayed the areal extent of aquifers, aquifer thickness, and overburden thickness. These studies generated a large body of subsurface geologic information as part of the regional aquifer analyses, some of which are captured in this digital data release. Aquifer systems in consolidated rocks in the Upper Colorado River Basin have been grouped into three major subdivisions of sedimentary rocks; in descending order: (1) Tertiary-rock aquifers, (2) Mesozoic-rock aquifers, and (3) Paleozoic-rock aquifers (Taylor and others, 1983; 1986). Within each aquifer group, rocks are further divided into aquifers and confining units on the basis of lithology, depositional environment, and hydrologic characteristics (Glover and others, 1998; Freethy and Cordy, 1991; Geldon, 2003). In a report describing consolidated-rock aquifers of Mesozoic age, 10 hydrostratigraphic units were defined, five aquifers and five confining units (Freethy and Cordy, 1991). The hydrostratigraphic units of Mesozoic age occur throughout the Upper Colorado River Basin study area, except in parts of the Uinta, White River, and San Juan uplifts where they have been removed by erosion. These hydrostratigraphic units are part of the stratigraphic sequence of Mesozoic rocks that has a total thickness of more than 8,000 ft. The sandstones of Mesozoic age are the most areally extensive and the thickest bedrock aquifers in the Upper Colorado River Basin. This digital dataset contains spatial datasets corresponding to the contoured subsurface maps produced by the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) of the Upper Colorado River Basin (Freethy and Cordy, 1991). The data define the thickness and extent of principal hydrostratigraphic units of Mesozoic age in the basin. The digital data describe the following hydrostratigraphic units: the Chinle-Moenkopi confining unit, the Navajo-Nugget aquifer, the Carmel-Twin Creek confining unit, the Entrada-Preuss aquifer, the Curtis-Stump confining unit, the Morrison aquifer, the Morrison confining unit, the Dakota aquifer, the Mancos confining unit, and the Mesaverde aquifer. Contoured thickness data for each unit are contained in line features classes within a geodatabase; unit extents are represented as polygon feature classes. Both types of data are also saved as individual shapefiles. Nonspatial tables define the data sources used, and the stacking hierarchy and component geologic formations of each the of hydrostratigraphic units.

The Upper Colorado River Basin has a drainage area of about 113,500 square miles in western Colorado, eastern Utah, southwestern Wyoming, northeastern Arizona, and northwestern New Mexico. In the 1980’s and 1990’s, the Upper Colorado River Basin was a study area under of the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) program (Sun and Johnston, 1994; Sun and Weeks, 1991). The objectives of the RASA program for the Upper Colorado River Basin were to provide regional assessments of major aquifer systems by providing quantitative assessments of the occurrence, movement, and availability of water stored in rock formations that underlie the basin/watershed. These assessments included: (1) the classification of stratigraphic sequences into those intervals that constitute aquifers and those that constitute confining beds; and (2) the generation of maps that portrayed the areal extent of aquifers, aquifer thickness, and overburden thickness. These studies generated a large body of subsurface geologic information as part of the regional aquifer analyses, some of which are captured in this digital data release. Aquifer systems in consolidated rocks in the Upper Colorado River Basin have been grouped into three major subdivisions of sedimentary rocks; in descending order: (1) Tertiary-rock aquifers, (2) Mesozoic-rock aquifers, and (3) Paleozoic-rock aquifers (Taylor and others, 1983; 1986). Within each aquifer group, rocks are further divided into aquifers and confining units on the basis of lithology, depositional environment, and hydrologic characteristics (Glover and others, 1998; Freethy and Cordy, 1991; Geldon, 2003). In a report describing consolidated-rock aquifers of Mesozoic age, 10 hydrostratigraphic units were defined, five aquifers and five confining units (Freethy and Cordy, 1991). The hydrostratigraphic units of Mesozoic age occur throughout the Upper Colorado River Basin study area, except in parts of the Uinta, White River, and San Juan uplifts where they have been removed by erosion. These hydrostratigraphic units are part of the stratigraphic sequence of Mesozoic rocks that has a total thickness of more than 8,000 ft. The sandstones of Mesozoic age are the most areally extensive and the thickest bedrock aquifers in the Upper Colorado River Basin. This digital dataset contains spatial datasets corresponding to the contoured subsurface maps produced by the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) of the Upper Colorado River Basin (Freethy and Cordy, 1991). The data define the thickness and extent of principal hydrostratigraphic units of Mesozoic age in the basin. The digital data describe the following hydrostratigraphic units: the Chinle-Moenkopi confining unit, the Navajo-Nugget aquifer, the Carmel-Twin Creek confining unit, the Entrada-Preuss aquifer, the Curtis-Stump confining unit, the Morrison aquifer, the Morrison confining unit, the Dakota aquifer, the Mancos confining unit, and the Mesaverde aquifer. Contoured thickness data for each unit are contained in line features classes within a geodatabase; unit extents are represented as polygon feature classes. Both types of data are also saved as individual shapefiles. Nonspatial tables define the data sources used, and the stacking hierarchy and component geologic formations of each the of hydrostratigraphic units.

This report and associated dataset, contains subsurface geologic information collected in the Sacramento-San Joaquin Valley. The primary data includes X, Y, Z locations of stratigraphic horizons and, to a much lesser extent, geologic structures where penetrated by oil and gas wells in the subsurface as recorded in well logs and well records. Selected oil and gas wells are not only examined for depth to stratigraphic horizon data, but also marked if deviated from vertical, or containing specific electronic logs that may be used for geophysical research. The data was compiled from well records made available through the California Department of Conservation, Geologic Energy Management Division (CalGEM) Well Finder web interface. Well Finder provides a map view of wells and fields with links to well records in the CalGEM database. Select records for wells in the study area (principally the well data report, which is a PDF copy of all the forms and associated "paperwork" filed with CalGEM and its predecessor state agencies, and the standard Spontaneous-Potential/Resistivity/Conductivity electric log) were requested, downloaded, and examined. Measurements of depth to geologic features (horizons) such as top or bottom of a geologic unit that are recorded in the well records were compiled into the data set, along with information about the location and identity of the well, and whether the well records available include other types of well log that are commonly of interest to 3D mappers. We also recorded if the well record mentioned that the well is deviated (not entirely vertical), which would affect the true X,Y,Z location of recorded horizons. However, we did not attempt to correct the data to account for the deviation. The values in the data set are those recorded in the well records. We also harvested the same information from the previously published USGS Open-File Report 2011-1262 (Brabb, 2011). Where there are many wells close together, we examined well records until finding a well with a relatively large suite of horizon depths recorded, and then used that well as representative of the many closely spaced wells. The goal was to get a good representation of the regional subsurface, not to record every well. In addition, we did not record all the information available in the well records for those wells in this dataset. The full records are freely available from the data sources. This dataset includes specific information compiled for the purpose described below. The information in this metadata file mainly describes the details of the contents and formats of the digital files.

The San Juan basin is a significant physical and structural element in the southeastern part of the Colorado Plateau physiographic province. The San Juan basin is in New Mexico, Colorado, Arizona, and Utah and has an area of about 21,600 square miles. The basin is about 140 miles wide and about 200 miles long. In the 1980’s and 1990’s, the San Juan basin was the focus of the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) study. Investigation of the San Juan structural basin began in October 1984 with an objective, among others, to define and evaluate the aquifer system. As part of this analysis, a multi-publication series of reports were produced as Hydrologic Atlas 720 (HA-720) that described on 1:1,000,000-scale maps the subsurface configuration and hydrogeology of the San Jose, Nacimiento, and Animas Formations (Levings and others, 1990; HA-720-A), the Ojo Alamo Sandstone (Thorn and others, 1990; HA-720-B), the Kirtland Shale and Fruitland Formation (Kernodle and others, 1990; HA-720-C), the Pictured Cliffs Sandstone (Dam and others, 1990; HA-720-D), the Cliff House Sandstone (Thorn and others, 1990; HA-720-E), the Menefee Formation (Levings and others, 1990; HA-720-F), the Point Lookout Sandstone (Craigg and others, 1990; HA-720-G), the Gallup Sandstone (Kernodle and others, 1990; HA-720-H), the Dakota Sandstone (Craigg and others, 1990; HA-720-I), and the Morrison Formation (Dam and others, 1990; HA-720-J). This digital dataset contains spatial datasets corresponding to the contoured subsurface maps produced by the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) San Juan basin study. The data define the elevation, thickness, and extent of principal stratigraphic units of the basin. The digital data describe the following stratigraphic units: the San Jose Formation, the Ojo Alamo Sandstone, the Kirtland Shale and Fruitland Formation, the Pictured Cliffs Sandstone, the Cliff House Sandstone, the Menefee Formation, the Point Lookout Sandstone, the Gallup Sandstone, the Dakota Sandstone, and the Morrison Formation. Digital data for each unit are contained in individual features classes within a geodatabase (also saved as individual shapefiles). Feature classes have a single attribute, either elevation or thickness, that represents the contoured value. Contoured values are given in feet, to maintain consistency with the original publication, and in meters.

The San Juan basin is a significant physical and structural element in the southeastern part of the Colorado Plateau physiographic province. The San Juan basin is in New Mexico, Colorado, Arizona, and Utah and has an area of about 21,600 square miles. The basin is about 140 miles wide and about 200 miles long. In the 1980’s and 1990’s, the San Juan basin was the focus of the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) study. Investigation of the San Juan structural basin began in October 1984 with an objective, among others, to define and evaluate the aquifer system. As part of this analysis, a multi-publication series of reports were produced as Hydrologic Atlas 720 (HA-720) that described on 1:1,000,000-scale maps the subsurface configuration and hydrogeology of the San Jose, Nacimiento, and Animas Formations (Levings and others, 1990; HA-720-A), the Ojo Alamo Sandstone (Thorn and others, 1990; HA-720-B), the Kirtland Shale and Fruitland Formation (Kernodle and others, 1990; HA-720-C), the Pictured Cliffs Sandstone (Dam and others, 1990; HA-720-D), the Cliff House Sandstone (Thorn and others, 1990; HA-720-E), the Menefee Formation (Levings and others, 1990; HA-720-F), the Point Lookout Sandstone (Craigg and others, 1990; HA-720-G), the Gallup Sandstone (Kernodle and others, 1990; HA-720-H), the Dakota Sandstone (Craigg and others, 1990; HA-720-I), and the Morrison Formation (Dam and others, 1990; HA-720-J). This digital dataset contains spatial datasets corresponding to the contoured subsurface maps produced by the U.S. Geological Survey's Regional Aquifer-System Analysis (RASA) San Juan basin study. The data define the elevation, thickness, and extent of principal stratigraphic units of the basin. The digital data describe the following stratigraphic units: the San Jose Formation, the Ojo Alamo Sandstone, the Kirtland Shale and Fruitland Formation, the Pictured Cliffs Sandstone, the Cliff House Sandstone, the Menefee Formation, the Point Lookout Sandstone, the Gallup Sandstone, the Dakota Sandstone, and the Morrison Formation. Digital data for each unit are contained in individual features classes within a geodatabase (also saved as individual shapefiles). Feature classes have a single attribute, either elevation or thickness, that represents the contoured value. Contoured values are given in feet, to maintain consistency with the original publication, and in meters.