The Bighorn Basin is a large Laramide structural and sedimentary basin that encompasses about 10,400 square miles in north-central Wyoming and south-central Montana (fig. 1). The basin is bounded on the northeast by the Pryor uplift, on the east by the Bighorn uplift and on the south by the Owl Creek uplift. The northern margin is formed by a zone of faulting and folding referred to as the Nye-Bowler lineament. The western and northwestern margins are formed by the Absaroka volcanics and Beartooth uplift, respectively (fig. 1). Commercial hydrocarbon production was first established in the Bighorn Basin when oil was discovered from Cretaceous reservoirs at Garland field in 1906 (Biggs and Espach, 1960). Since then, many important conventional oil and gas resources have been discovered and produced from reservoirs ranging from Cambrian through Tertiary in age (De Bruin, 1993; Fox and Dolton, 1989,1996). In addition, a potential basin-centered gas accumulation may be present in Cretaceous reservoirs in the deeper parts of the basin (Spencer, 1987; Ryder, 1987; Surdam and others, 1997; Johnson and Finn, 1998; Johnson and others, 1999; and Finn and others, 2010). It has been suggested that various Upper Cretaceous marine shales are the principal hydrocarbon source rocks for many of these accumulations (Geis, 1923; Burtner and Warner, 1984; Hagen and Surdam, 1984; Meissner and others, 1984; Ryder, 1987). With new drilling and well completion technologies, equivalent marine source rock intervals, in particular the Niobrara Formation, are now important continuous (unconventional) shale gas and shale oil objectives in other Rocky Mountain basins (Matthews, 2011; Sonnenberg, 2011; Williams and Lyle, 2011; Durham, 2012a,b, 2013; Taylor and Sonnenberg, 2014; and Hawkins, 2016). In the Bighorn Basin the Niobrara is represented by shales, calcareous shales, marls, siltstones, and sandstones in the lower part of the Upper Cretaceous Cody Shale (Finn, 2014) (fig. 2). Please see supplemental information for associated references. Selected figures have also been included to help describe this data release. These figures are provided in pdf and jpg format. These include: Fig. 1_Rocky Mountain basins.pdf/jpg. Map of Rocky Mountain region showing locations of Laramide sedimentary and structural basins and intervening uplifts. Fig. 2_Xsection.pdf/jpg. Regional east-west stratigraphic cross section of Cretaceous rocks in the Wind River Basin. Each modified from Finn (2014). Please see data dictionary sheet in the excel file for detailed table column/attribute information.

The Bighorn Basin is a large Laramide structural and sedimentary basin that encompasses about 10,400 square miles in north-central Wyoming and south-central Montana (fig. 1). The basin is bounded on the northeast by the Pryor uplift, on the east by the Bighorn uplift and on the south by the Owl Creek uplift. The northern margin is formed by a zone of faulting and folding referred to as the Nye-Bowler lineament. The western and northwestern margins are formed by the Absaroka volcanics and Beartooth uplift, respectively (fig. 1). Commercial hydrocarbon production was first established in the Bighorn Basin when oil was discovered from Cretaceous reservoirs at Garland field in 1906 (Biggs and Espach, 1960). Since then, many important conventional oil and gas resources have been discovered and produced from reservoirs ranging from Cambrian through Tertiary in age (De Bruin, 1993; Fox and Dolton, 1989,1996). In addition, a potential basin-centered gas accumulation may be present in Cretaceous reservoirs in the deeper parts of the basin (Spencer, 1987; Ryder, 1987; Surdam and others, 1997; Johnson and Finn, 1998; Johnson and others, 1999; and Finn and others, 2010). It has been suggested that various Upper Cretaceous marine shales are the principal hydrocarbon source rocks for many of these accumulations (Geis, 1923; Burtner and Warner, 1984; Hagen and Surdam, 1984; Meissner and others, 1984; Ryder, 1987). With new drilling and well completion technologies, equivalent marine source rock intervals, in particular the Niobrara Formation, are now important continuous (unconventional) shale gas and shale oil objectives in other Rocky Mountain basins (Matthews, 2011; Sonnenberg, 2011; Williams and Lyle, 2011; Durham, 2012a,b, 2013; Taylor and Sonnenberg, 2014; and Hawkins, 2016). In the Bighorn Basin the Niobrara is represented by shales, calcareous shales, marls, siltstones, and sandstones in the lower part of the Upper Cretaceous Cody Shale (Finn, 2014) (fig. 2). Please see supplemental information for associated references. Selected figures have also been included to help describe this data release. These figures are provided in pdf and jpg format. These include: Fig. 1_Rocky Mountain basins.pdf/jpg. Map of Rocky Mountain region showing locations of Laramide sedimentary and structural basins and intervening uplifts. Fig. 2_Xsection.pdf/jpg. Regional east-west stratigraphic cross section of Cretaceous rocks in the Wind River Basin. Each modified from Finn (2014). Please see data dictionary sheet in the excel file for detailed table column/attribute information.

The Wind River Basin is a large Laramide (Late Cretaceous through Eocene) structural and sedimentary basin that encompasses about 7,400 square miles in central Wyoming (fig. 1). The basin is bounded by the Washakie Range and Owl Creek and southern Bighorn Mountains on the north, the Casper arch on the east, the Granite Mountains on the south, and Wind River Range on the west (figs. 1). Many important conventional and unconventional oil and gas resources have been discovered and produced from reservoirs ranging from Mississippian through Tertiary in age (Keefer, 1969; Fox and Dolton, 1989, 1996; De Bruin, 1993; Johnson and others, 1996, 2007). It has been suggested by numerous authors including: Keefer, 1969; Meissner and others, 1984; Fox and Dolton, 1989, 1996; Johnson and Rice, 1993; Nuccio and others, 1996; and Schelling and Wavrek, 1999, 2001: that various Upper Cretaceous marine shales are the principal hydrocarbon source rocks for many of these accumulations. With new drilling and well completion technologies, equivalent marine source rock intervals, in particular the Niobrara Formation, are now important continuous (unconventional) shale gas and shale oil objectives in other Rocky Mountain basins ((Matthews, 2011; Sonnenberg, 2011; Williams and Lyle, 2011; Durham, 2012a,b, 2013; Taylor and Sonnenberg, 2014; and Hawkins, 2016). In the Wind River Basin the Niobrara is represented by shales, calcareous shales, marls, siltstones, and sandstones in the lower shaly member of the Upper Cretaceous Cody Shale (Finn, 2017) (fig. 2). Please see supplemental information for associated references. Selected figures have also been included to help describe this data release. These figures are provided in pdf and jpg format. These include: Fig. 1_Rocky Mountain basins.pdf/jpg. Map of Rocky Mountain region showing locations of Laramide sedimentary and structural basins and intervening uplifts. Fig. 2_Regional Cretaceous X section.pdf/jpg. Regional east-west stratigraphic cross section of Cretaceous rocks in the Wind River Basin. Each modified from Finn (2017).

The Wind River Basin is a large Laramide (Late Cretaceous through Eocene) structural and sedimentary basin that encompasses about 7,400 square miles in central Wyoming (fig. 1). The basin is bounded by the Washakie Range and Owl Creek and southern Bighorn Mountains on the north, the Casper arch on the east, the Granite Mountains on the south, and Wind River Range on the west (figs. 1). Many important conventional and unconventional oil and gas resources have been discovered and produced from reservoirs ranging from Mississippian through Tertiary in age (Keefer, 1969; Fox and Dolton, 1989, 1996; De Bruin, 1993; Johnson and others, 1996, 2007). It has been suggested by numerous authors including: Keefer, 1969; Meissner and others, 1984; Fox and Dolton, 1989, 1996; Johnson and Rice, 1993; Nuccio and others, 1996; and Schelling and Wavrek, 1999, 2001: that various Upper Cretaceous marine shales are the principal hydrocarbon source rocks for many of these accumulations. With new drilling and well completion technologies, equivalent marine source rock intervals, in particular the Niobrara Formation, are now important continuous (unconventional) shale gas and shale oil objectives in other Rocky Mountain basins ((Matthews, 2011; Sonnenberg, 2011; Williams and Lyle, 2011; Durham, 2012a,b, 2013; Taylor and Sonnenberg, 2014; and Hawkins, 2016). In the Wind River Basin the Niobrara is represented by shales, calcareous shales, marls, siltstones, and sandstones in the lower shaly member of the Upper Cretaceous Cody Shale (Finn, 2017) (fig. 2). Please see supplemental information for associated references. Selected figures have also been included to help describe this data release. These figures are provided in pdf and jpg format. These include: Fig. 1_Rocky Mountain basins.pdf/jpg. Map of Rocky Mountain region showing locations of Laramide sedimentary and structural basins and intervening uplifts. Fig. 2_Regional Cretaceous X section.pdf/jpg. Regional east-west stratigraphic cross section of Cretaceous rocks in the Wind River Basin. Each modified from Finn (2017).

In 2019 the U.S. Geological Survey (USGS) quantitively assessed the potential for undiscovered, technically recoverable continuous (unconventional) oil and gas resources in the Niobrara interval of the Cody Shale in the Bighorn Basin Province (Finn and others, 2019). Leading up to the assessment, in 2017, the USGS collected samples from the Niobrara and underlying Sage Breaks intervals (Finn, 2019) to better characterize the source rock potential of the Niobrara interval. Eighty-two samples from 31 wells were collected from the well cuttings collection stored at the USGS Core Research Center in Lakewood, Colorado. The selected wells are located near the outcrop belt along the shallow margins of the basin to obtain samples that were not subjected to the effects of deep burial and subsequent organic carbon loss due to thermal maturation as described by Daly and Edman (1987) (fig. 1). Sixty samples are from the Niobrara interval, and 22 from the Sage Breaks interval (fig. 2).

This data release contains the boundaries of assessment units and input data for the assessment of continuous oil and gas resources of the Niobrara interval of the Cody Shale in the Bighorn Basin Province of Wyoming and Montana. The Assessment Unit is the fundamental unit used in the National Assessment Project for the assessment of undiscovered oil and gas resources. The Assessment Unit is defined within the context of the higher-level Total Petroleum System. The Assessment Unit is shown herein as a geographic boundary interpreted, defined, and mapped by the geologist responsible for the province and incorporates a set of known or postulated oil and (or) gas accumulations sharing similar geologic, geographic, and temporal properties within the Total Petroleum System, such as source rock, timing, migration pathways, trapping mechanism, and hydrocarbon type. The Assessment Unit boundary is defined geologically as the limits of the geologic elements that define the Assessment Unit, such as limits of reservoir rock, geologic structures, source rock, and seal lithologies. The only exceptions to this are Assessment Units that border the Federal-State water boundary. In these cases, the Federal-State water boundary forms part of the Assessment Unit boundary. Methodology of assessments are documented in USGS Data Series 547 for continuous assessments (https://pubs.usgs.gov/ds/547) and USGS DDS69-D, Chapter 21 for conventional assessments (https://pubs.usgs.gov/dds/dds-069/dds-069-d/REPORTS/69_D_CH_21.pdf). See supplemental information for a detailed list of files included this data release.

This data release contains the boundaries of assessment units and input data for the assessment of continuous oil and gas resources of the Niobrara interval of the Cody Shale in the Bighorn Basin Province of Wyoming and Montana. The Assessment Unit is the fundamental unit used in the National Assessment Project for the assessment of undiscovered oil and gas resources. The Assessment Unit is defined within the context of the higher-level Total Petroleum System. The Assessment Unit is shown herein as a geographic boundary interpreted, defined, and mapped by the geologist responsible for the province and incorporates a set of known or postulated oil and (or) gas accumulations sharing similar geologic, geographic, and temporal properties within the Total Petroleum System, such as source rock, timing, migration pathways, trapping mechanism, and hydrocarbon type. The Assessment Unit boundary is defined geologically as the limits of the geologic elements that define the Assessment Unit, such as limits of reservoir rock, geologic structures, source rock, and seal lithologies. The only exceptions to this are Assessment Units that border the Federal-State water boundary. In these cases, the Federal-State water boundary forms part of the Assessment Unit boundary. Methodology of assessments are documented in USGS Data Series 547 for continuous assessments (https://pubs.usgs.gov/ds/547) and USGS DDS69-D, Chapter 21 for conventional assessments (https://pubs.usgs.gov/dds/dds-069/dds-069-d/REPORTS/69_D_CH_21.pdf). See supplemental information for a detailed list of files included this data release.

This data release contains data associated with the USGS SIM publication "Stratigraphic Cross Sections of the Lewis Shale in the eastern part of the Southwestern Wyoming Province, Wyoming and Colorado". North-to-southeast (A–A’), west-to-east (B–B’), and southwest-to-northeast (C–C’) cross sections were created from 105 wells throughout the eastern part of the Southwestern Wyoming Province. The cross sections highlight 15 clinothems within the Lewis Shale, Fox Hills Sandstone, and Lance Formation progradational system. Data include well information and depths to key stratigraphic surfaces for 105 wells within the three cross sections. Well information includes the cross section identification, API #, well name, latitude in decimals, longitude in decimals, projection datum, county, state, Kelly Bushing elevation in feet, section, township, and range. Wells 19*, 26*, 69* and 70* are intersection points between the three sections. The stratigraphic data are all listed in measured depth relative to the Kelly bushing elevation and include the depth to the top of the Almond Formation, depth to the top and base of the informal Asquith marker, depth to the tops of 15 flooding surfaces which define the series of clinothems within the Lewis Shale, depth the top of the Lewis Shale, and depth to the top of the Fox Hills Sandstone.

The USGS Central Region Energy Team assesses oil and gas resources of the United States. The onshore and State water areas of the United States comprise 71 provinces. Within these provinces, Total Petroleum Systems are defined and Assessment Units are defined and assessed. Each of these provinces is defined geologically, and most province boundaries are defined by major geologic changes. The Bighorn Basin Province is located in Wyoming and south central Montana. The main population centers within the study area are Cody and Thermopolis, Wyoming. The main highways, I-70 and I-90, generally traverse the area from north to south. The Bighorn River and its tributaries drain the area. The province boundary was drawn to include the geologic structures generally considered to be in or bounding the Bighorn Basin.

The USGS Central Region Energy Team assesses oil and gas resources of the United States. The onshore and State water areas of the United States comprise 71 provinces. Within these provinces, Total Petroleum Systems are defined and Assessment Units are defined and assessed. Each of these provinces is defined geologically, and most province boundaries are defined by major geologic changes. The Bighorn Basin Province is located in Wyoming and south central Montana. The main population centers within the study area are Cody and Thermopolis, Wyoming. The main highways, I-70 and I-90, generally traverse the area from north to south. The Bighorn River and its tributaries drain the area. The province boundary was drawn to include the geologic structures generally considered to be in or bounding the Bighorn Basin.