Natural Resources, School of


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Educational Circular 16; published by the Conservation and Survey Division, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln


Copyright (c) 2002, the authors.


The year 2002 will mark the fiftieth anniversary of completion of the Harlan County Dam and Multi-Purpose Reservoir. This seems a good time to write about the history of and reasons for building the dam, the effects of the dam and reservoir on the Republican River valley, and the geologic features seen along the shores of the lake and areas nearby. As many junior authors helped produced this educational circular, they are listed in the table of contents. All other sections were written by the senior author.

Includes July 2016 update: Addendum of photographs showing fault traces on drought-exposed lake bottom. Cretaceous Niobrara Chalk Formation and the younger Pierre Shale are also shown.

Table of Contents
Introduction 1
Location 1
Republican River Floods 1
The Republican River Flood of 1935 - D R Mohlman 1
Cautionary Notes (sidebar) 1
Events After the Flood Leading to Creation of Harlan County Lake 9
Stormer Ford Dog Town (sidebar) 10
Water 10
Surface Water Hydrology - S Summerside 10
Shoreline Springs and Seeps - F: E Harvey and K J Warren 12
Introduction 12
Using Water Chemistry to Identify Spring and Seep Origin 1 2
Geology 15
General Conditions Leading to Good Exposures 15
Stratigraphy of Unconsolidated Sediments and Rock Strata 15
Cretaceous System - Upper Cretaceous Series 15
Niobrara Formation - Smoky Hill Chalk Member 15
Pierre Shale 15
Tertiary System - Miocene Series 16
Ogallala Group -Ash Hollow Formation 16
Quaternary System - Pleistocene Series 16
Crete (?) Formation (Sands and Gravels) 1 6
Loveland Loess 16
Gliman Canyon Formation 16
Peoria and Bignell Loesses 16
Quaternary System - Holocene (Recent) Series 1 6
Unnamed Fluvial, Eolian, and Colluvial Deposits 16
Paleontology of the Various Formations 16
Plants 16
Invertebrates - R K Pabian 17
Cretaceous Marine Fossils 17
Niobrara Formation 17
Foraminifers 17
Post-Devonian "Stromatoporoids" 1 9
Mollusks 19
Bivalves 19
Ammonites 19
Pierre Shale Formation 19
Bivalves 19
Ammonites 19
Quaternary - Pleistocene (Ice Age) Invertebrate Fossils 19
Vertebrate Fossils - R G Corner 24
Late Cretaceous Fossils 24
Niobrara Formation 24
Niobrara Fishes 24
Niobrara Mosasaurs 29
Pierre Shale Formation 30
"Protosphyvaena " gladius: Giant Mystery Fish 30
Pierre Mosasaurs 32
Late Miocene Ogallala Group 32
Bone Cove I Fauna 32
Bone Cove II Fauna 32
Quaternary - Pleistocene (Ice Age) 33
Crete (?) Sands and Gravels 33
Gilman Canyon Formation 33
Peoria Loess 35
Late Pleistocene Fauna 35
Late Pleistocene Environments 37
Geologic Processes Affecting the Strata 37
Modem and Ancient Landslides 37
Modern Landslides D A Eversoll 37
Ancient Landslides - D A Eversoll and R F Diffendal, Jr 39
Geologic Structures 41
Introduction and Previous Work 41
Angular Unconformities 45
Joints 45
Faults and Folds 45
Ancient Landscapes (Paleotopography) 50
Quaternary River Terraces 50
Concluding Remarks 50
References Cited 51

Keywords: flooding 1930s, vertebrate fossils, earthquake faults, landslides, groundwater quality