OF-24-03 Geologic Map of the Severance Quadrangle, Weld County, Colorado

The purpose of this publication is to describe the geology, mineral and groundwater resources, and geologic hazards of the Severance 7.5-minute quadrangle. It is a continuation of field mapping work in the northern Colorado Piedmont where the CGS has mapped multiple quadrangles, this one covering the area around the town of Severance. Nearby published quadrangles include Timnath, Windsor, Bracewell, Greeley and Fort Collins. CGS geologists Alexander Marr, Emily Perman and Kassandra Lindsey completed the field work on this project during the mapping seasons of 2023-24. Digital ZIP download. OF-24-03D

From the abstract:

The Severance quadrangle is located about 100 km northeast of Denver and within the Front Range Urban Corridor. The quadrangle lies within the northern part of the Colorado Piedmont, a physiographic province bounded by the Rocky Mountains to the west and High Plains to the north and east. Fluvial erosion and geomorphic evolution of the ancestral South Platte River and its tributaries during the Pliocene have removed most of the Paleogene and Neogene rocks in the northern Colorado Piedmont. The result is a scoured region that is topographically lower than the surrounding physiographic provinces. The elevation range within the Severance quadrangle is about 1447-1615 m (4749-5297 ft) with a total relief of 167 m (548 ft). South of the quadrangle, incision along the Cache la Poudre River and its three tributaries: The Slough, Coalbank Creek valleys, and the Eaton paleovalley. contribute to the relatively low relief in the area. These three tributaries were possibly part of an ancient tributary system to the Cache al Poudre River that flowed roughly north to south in the quadrangle. These streams had a higher competence and formed wide stream valleys. Over time, the stream competence decreased, resulting in large paleovalleys with low flowing underfit streams.

The Severance quadrangle is located in the western part of the Denver Basin and Weld County. The quadrangle contains the following mineral resources: oil and gas, coal, uranium, and sand and gravel. The Severance quadrangle lies in the northwest margin of the Wattenberg oil field which is a productive oil and gas field that is mostly in Weld and Adam Counties. The Wattenberg Field is the fourth largest oil field in the United States and ninth largest gas field based on proved reserves. Weld County has an estimated total production value of over $12 billion in oil and gas production and produced over 133 million oil barrels in 2023. Oil and gas infrastructure is dominant in the central and southern portions of the quadrangle. The Niobrara Formation is the principal production horizon in the Wattenberg Field. Other formations with production horizons include the Shannon/Hygiene Sandstone (middle member of the Pierre Shale, the Codell Sandstone (upper part of the Colorado Group), the J sandstone (from the Muddy Formation), and the D sandstone of the Dakota Group. Three small oilfields that produced oil primarily from the Permian Lyons Sandstone are located within and around the Severance quadrangle: New Windsor, Black Hollow, and Pierce. In these oilfields, oil is trapped by a combination of oil-producing bedrock units and small anticlines. Oil and natural gas cumulative production from these fields were 10.8 million barrels and 0.330 million cubic feet of gas in Black Hollow and 11.5 million barrels in Pierce. Cretaceous formations also serve as important source rocks for oil in these fields: the Black Hollow field produces oil from the Niobrara Formation and Codell Sandstone; the New Windsor field produced oil from the Terry, Hygiene/Shannon members of the Pierre Shale, and Codell Sandstone.