Natural Resources, School of
Date of this Version
12-2023
Document Type
Article
Citation
Diffendal, R.F. Jr. and Swinehart, J.B., The Broadwater Formation (Pliocene) of Nebraska and Southeastern Wyoming, 2023. University of Nebraska–Lincoln, Conservation and Survey Division, Report of Investigations 13, 36 pp.
ISBN 978-1-56161-093-8
Abstract
The Broadwater Formation, initially defined in 1945, is a Pliocene-aged coarse-grained alluvial deposit in Nebraska and southeastern Wyoming. It is characterized by a complex stratigraphic history and debated geologic interpretations. The formation is a rich resource of groundwater for the citizens of Nebraska and the Central Great Plains. We aim to synthesize and redefine the Broadwater Formation, shedding light on its distribution, geological characteristics, and paleoenvironmental significance. While historical hypotheses on Broadwater Formation paleovalley trajectories suggested northwest-southeast trending valleys, later investigations proposed wind-driven erosional patterns to explain the unique topographic features observed. The Broadwater is divided into an unnamed Upper Member and a lower Remsburg Ranch Member.
The Unnamed Upper Member is primarily composed of coarse clastic sediments. We interpret these to have been deposited in a braided river system, while the Remsberg Ranch Member is even coarser-grained and was deposited primarily in deep, narrow, anastomosing bedrock-incised inner channels. We also explore climatic shifts and tectonic influences, suggesting a relationship between changes in river discharge, sediment load, and climatic conditions during the late Miocene to Pliocene transition. Differential mountain uplift, salt dissolution in underlying strata, and potential glacial activity in the Southern Rockies also were involved in shaping the Broadwater Formation's characteristics.
Comments
Copyright 2023, Diffendal and Swinehart. Used by permission.