In conjunction with geologic mapping of four 7.5′ quadrangles along the South Platte River corridor in northeastern Colorado (Masters, Orchard, Weldona, and Fort Morgan), geochronology samples were collected and analyzed using optically stimulated luminescence (OSL), radiocarbon (14C), or U-series methods to provide age control for mapping units. This section of river corridor is largely covered by surficial deposits that formed from alluvial, eolian, and hillslope processes operating in concert with environmental changes from the Pleistocene to the present. The South Platte River originates high in the Colorado Rocky Mountains and recurrent glaciation of basin headwaters has affected river discharge and sediment supply far downstream, influencing aggradation and incision along this part of the river corridor. Unglaciated tributaries originating in the Colorado Piedmont east of the Front Range have periodically deposited large volumes of sediment at their confluences during major flood events. Eolian sand deposits cover much of the area and record past episodes of sand mobilization during times of prolonged drought. Sediment samples dated using OSL provide ages for alluvial and eolian sand deposits; organic samples dated using 14C methods constrain ages of alluvial deposits; and bone and river gravels with calcium carbonate rinds dated using U-series methods provide minimum ages for alluvial deposits.

The Weldona 7.5' quadrangle is located on the semiarid plains of northeastern Colorado, along the South Platte River corridor where the river has incised into Upper Cretaceous Pierre Shale. The Pierre Shale is largely covered by surficial deposits that formed from alluvial, eolian, and hillslope processes operating in concert with environmental changes from the Pleistocene to the present. The South Platte River, originating high in the Colorado Rocky Mountains, has played a major role in shaping surficial geology in the map area, which is several tens of kilometers downstream from where headwater tributaries join the river. Recurrent glaciation (and deglaciation) of basin headwaters has affected river discharge and sediment supply far downstream, influencing deposition of alluvium and river incision in the Weldona quadrangle. During the Pleistocene the course of the river within the map area shifted progressively southward as it incised, and by late middle Pleistocene the river was south of its present position, cutting and filling deep paleochannels now covered by younger alluvium. The river shifted back to the north during the late Pleistocene. Kiowa and Bijou Creeks are unglaciated tributaries originating in the Colorado Piedmont east of the Front Range that also have played a major role in shaping surficial geology of the map area. Periodically during the late Pleistocene, major flood events on these tributaries deposited large volumes of sediment at their confluences, forming a broad, low-gradient fan of sidestream alluvium that could have occasionally dammed the river for short periods of time. Eolian sand deposits of the Sterling (north of river) and Fort Morgan (south of river) dune fields cover much of the quadrangle and record past episodes of sand mobilization during times of prolonged drought. With the onset of irrigation and damming during historical times, the South Platte River has changed from a broad, shallow, and sandy braided river with highly variable seasonal discharge to a much narrower, deeper river with braided-meandering transition morphology and more uniform discharge.

The Weldona 7.5' quadrangle is located on the semiarid plains of northeastern Colorado, along the South Platte River corridor where the river has incised into Upper Cretaceous Pierre Shale. The Pierre Shale is largely covered by surficial deposits that formed from alluvial, eolian, and hillslope processes operating in concert with environmental changes from the Pleistocene to the present. The South Platte River, originating high in the Colorado Rocky Mountains, has played a major role in shaping surficial geology in the map area, which is several tens of kilometers downstream from where headwater tributaries join the river. Recurrent glaciation (and deglaciation) of basin headwaters has affected river discharge and sediment supply far downstream, influencing deposition of alluvium and river incision in the Weldona quadrangle. During the Pleistocene the course of the river within the map area shifted progressively southward as it incised, and by late middle Pleistocene the river was south of its present position, cutting and filling deep paleochannels now covered by younger alluvium. The river shifted back to the north during the late Pleistocene. Kiowa and Bijou Creeks are unglaciated tributaries originating in the Colorado Piedmont east of the Front Range that also have played a major role in shaping surficial geology of the map area. Periodically during the late Pleistocene, major flood events on these tributaries deposited large volumes of sediment at their confluences, forming a broad, low-gradient fan of sidestream alluvium that could have occasionally dammed the river for short periods of time. Eolian sand deposits of the Sterling (north of river) and Fort Morgan (south of river) dune fields cover much of the quadrangle and record past episodes of sand mobilization during times of prolonged drought. With the onset of irrigation and damming during historical times, the South Platte River has changed from a broad, shallow, and sandy braided river with highly variable seasonal discharge to a much narrower, deeper river with braided-meandering transition morphology and more uniform discharge.

In 1978, the late Denis Marchand launched a project to identify, sample, and analyze soil profiles from seven soil chronosequences in the Western United States. The resulting datasets were compiled as part of a series of reports titled "Soil Chronosequences in the Western United States". Early studies of soil formation highlighted several key factors that together determine the degree of soil pedogenesis, which include climate, organisms (including vegetation), topography, and parent material (Jenny H.; 1941; Factors of Soil Formation, a System of Quantitative Pedology; https://doi.org/10.2134/agronj1941.00021962003300090016x). A soil chronosequence is defined as a series of soils in which all soil-forming factors except time are similar, where time is represented by soil or landform age. This compilation of chronosequences included soils developed on a variety of landforms including alluvial fans, fluvial terraces, glacial moraines, and marine terraces. The estimated age of these soils was based on a variety of chronological dating tools specific to each chronosequence and values range from modern-aged samples to samples that are three hundred thousand years old. At the time preceding this work, it was becoming clear from the marine record that the variations in climate and terrestrial processes were extensive with a paucity of numerical dating techniques applicable to the geologic record. The ubiquitous nature of soils made this project of critical importance to a better understanding of terrestrial processes. These data were originally published in analog form by individual authors in the U.S. Geological Survey Bulletin 1590 series, which was edited by J.W. Harden. Here, data from the original bulletin series including location, land cover, horizon depths, field morphology, color, texture, particle size, bulk density, organic carbon, pH, cation exchange capacity, dithionite extractable iron, major element abundance, trace element abundance, inorganic carbon content, and mineralogy, are compiled together as a single dataset in digital form. In addition, we have also compiled scanned field notes and site photographs that are associated with these publications. Furthermore, the original samples that were collected and analyzed associated with this dataset for the Colorado, Cowlitz, Kane Fans, Merced, Rock Creek, and Ventura chronosequences have been archived via the U.S. Geological Survey Soil Sample Archive (https://doi.org/10.5066/P90KTZW4).

In 1978, the late Denis Marchand launched a project to identify, sample, and analyze soil profiles from seven soil chronosequences in the Western United States. The resulting datasets were compiled as part of a series of reports titled "Soil Chronosequences in the Western United States". Early studies of soil formation highlighted several key factors that together determine the degree of soil pedogenesis, which include climate, organisms (including vegetation), topography, and parent material (Jenny H.; 1941; Factors of Soil Formation, a System of Quantitative Pedology; https://doi.org/10.2134/agronj1941.00021962003300090016x). A soil chronosequence is defined as a series of soils in which all soil-forming factors except time are similar, where time is represented by soil or landform age. This compilation of chronosequences included soils developed on a variety of landforms including alluvial fans, fluvial terraces, glacial moraines, and marine terraces. The estimated age of these soils was based on a variety of chronological dating tools specific to each chronosequence and values range from modern-aged samples to samples that are three hundred thousand years old. At the time preceding this work, it was becoming clear from the marine record that the variations in climate and terrestrial processes were extensive with a paucity of numerical dating techniques applicable to the geologic record. The ubiquitous nature of soils made this project of critical importance to a better understanding of terrestrial processes. These data were originally published in analog form by individual authors in the U.S. Geological Survey Bulletin 1590 series, which was edited by J.W. Harden. Here, data from the original bulletin series including location, land cover, horizon depths, field morphology, color, texture, particle size, bulk density, organic carbon, pH, cation exchange capacity, dithionite extractable iron, major element abundance, trace element abundance, inorganic carbon content, and mineralogy, are compiled together as a single dataset in digital form. In addition, we have also compiled scanned field notes and site photographs that are associated with these publications. Furthermore, the original samples that were collected and analyzed associated with this dataset for the Colorado, Cowlitz, Kane Fans, Merced, Rock Creek, and Ventura chronosequences have been archived via the U.S. Geological Survey Soil Sample Archive (https://doi.org/10.5066/P90KTZW4).

The data release includes 35 new luminescence ages and 3 new radiocarbon ages. The new age data further brackets the ages of the Las Vegas basin Quaternary stratigraphy and provide new constraints on the timing of Quaternary fault activity.

The data release includes 35 new luminescence ages and 3 new radiocarbon ages. The new age data further brackets the ages of the Las Vegas basin Quaternary stratigraphy and provide new constraints on the timing of Quaternary fault activity.

This digital dataset release of the Tectonic Map of the Colorado Plateau is a courtesy publication of the previously published legacy report by V.C. Kelley in 1955. The original publication, "Tectonic Map of the Colorado Plateau Showing Uranium Deposits" contains elevation contours from the top of the Chinle formation in 1000 ft intervals and geologic structural formations such as monoclinal, synclinal, and anticlinal structures. The digitizing of this map is to provide a more accessible dataset to be available for public usage. The original dataset was in relation to a larger project by the University of New Mexico and their publications in geology of uranium distributions throughout the Colorado Plateau (Kelley, V.C., 1955, Regional tectonics of the Colorado Plateau and relationship to the origin and distribution of uranium: Albuquerque, University of New Mexico, Publications in Geology no. 5, 120 p., 1 sheet, scale 1:1,000,000.). The entirety of this dataset includes both spatial and non-spatial data held in a singular, GeMS compliant geodatabase. This geodatabase includes a geologic map feature dataset holding fault lines, iso value lines, structure contours, and other geologic lines; nonspatial data recorded in standalone tables such as a description of map units, glossary, data source reference, geomaterials dictionary, and their entities and attributes. Data source references include web links to published standards, data dictionaries, and any other referenced data within the published map. There is a final nonspatial table that is in reference to the original digitized and identified geologic structures per the legacy map plate, these structures were broken up by state (Arizona, Colorado, New Mexico, and Utah) with each structure given a numerical value (starting at 1, for each individual state) these structures were compiled into a synchronous excel document to provide a digital record of those structures and features listed on the legacy map plate.

This digital dataset release of the Tectonic Map of the Colorado Plateau is a courtesy publication of the previously published legacy report by V.C. Kelley in 1955. The original publication, "Tectonic Map of the Colorado Plateau Showing Uranium Deposits" contains elevation contours from the top of the Chinle formation in 1000 ft intervals and geologic structural formations such as monoclinal, synclinal, and anticlinal structures. The digitizing of this map is to provide a more accessible dataset to be available for public usage. The original dataset was in relation to a larger project by the University of New Mexico and their publications in geology of uranium distributions throughout the Colorado Plateau (Kelley, V.C., 1955, Regional tectonics of the Colorado Plateau and relationship to the origin and distribution of uranium: Albuquerque, University of New Mexico, Publications in Geology no. 5, 120 p., 1 sheet, scale 1:1,000,000.). The entirety of this dataset includes both spatial and non-spatial data held in a singular, GeMS compliant geodatabase. This geodatabase includes a geologic map feature dataset holding fault lines, iso value lines, structure contours, and other geologic lines; nonspatial data recorded in standalone tables such as a description of map units, glossary, data source reference, geomaterials dictionary, and their entities and attributes. Data source references include web links to published standards, data dictionaries, and any other referenced data within the published map. There is a final nonspatial table that is in reference to the original digitized and identified geologic structures per the legacy map plate, these structures were broken up by state (Arizona, Colorado, New Mexico, and Utah) with each structure given a numerical value (starting at 1, for each individual state) these structures were compiled into a synchronous excel document to provide a digital record of those structures and features listed on the legacy map plate.

This dataset includes tables of U- and Th-isotopic data used to calculate uranium-series age estimates (230Th/U method) and initial 234U/238U activity ratios for samples of pedogenic carbonate formed in soils on alluvial fans in the San Luis Valley, Colorado, USA.