Abstract
The Spearfish-Rapid Creek drainage extends from elevations greater than 7130 feet (2173 meters) roughly in a north direction across the northern Black Hills upland to where it becomes the Spearfish-Whitewood Creek drainage divide at an elevation of approximately 6440 feet (1963 meters) and separates north-oriented Spearfish Creek headwaters from southeast- and east-oriented Rapid Creek headwaters. This study used detailed topographic maps to investigate through valleys (and wind gaps) now crossing the Spearfish-Rapid Creek drainage divide, which is one of the Black Hills’ highest drainage divides. Through valley (or wind gap) floor elevations were determined and ranged from approximately 6150 feet (1875 meters) to approximately 7050 feet (2149 meters) and through valley (and wind gap) depths were also calculated and ranged from approximately 30 feet (9 meters) to about 290 feet (88 meters). Map evidence suggesting these through valleys (and wind gaps) originated as components of diverging and converging complexes of bedrock-walled channels is described and suggests large and prolonged southeast-oriented floods once flowed from or across the Spearfish Creek drainage basin to the Rapid Creek drainage basin. Based on today’s topography there is no upland Black Hills region capable of generating the large and prolonged floods required to erode the observed through valleys (and wind gaps) and their associated diverging and converging channel complexes so the erosion is interpreted to have taken place while the Black Hills were just beginning to emerge as the topographic high they are today. A water source could not be determined from map evidence, but large and prolonged southeast-oriented floods across the region are consistent with a recently proposed hypothesis that massive southeast-oriented (continental ice sheet) ice-marginal melt water floods eroded what are today western South Dakota and North Dakota river drainage basins.
Highlights
The term through valley is frequently used to describe former glacial melt water channels, the term can describe any water-eroded valley crossed by one or more drainage divides
Research related to this paper used detailed topographic maps found at the United States Geological Survey (USGS) National Map website to identify through valleys and wind gaps linking the Spearfish Creek and Rapid Creek drainage basins
Southeast-oriented water flowing from the present day Spearfish Creek drainage basin to the North Fork Rapid Creek valley eroded through valley 1 and a reversal of flow created what is today northwest-oriented East Spearfish Creek and created the present day East Spearfish-North Rapid Creek drainage divide
Summary
The term through valley is frequently used to describe former glacial melt water channels, the term can describe any water-eroded valley crossed by one or more drainage divides. In many non-glaciated regions through valleys of the latter type are remarkably common and provide evidence of dismembered stream or river drainage routes. The dismemberment of those former drainage routes and the through valley formation process almost always involved one or more stream capture events, yet Bishop (1995) argues stream capture is rare in normal drainage net evolution. The study reported here analyzes detailed topographic map evidence to determine the nature of drainage routes responsible for through valleys (and wind gaps) that cross Black Hills upland regions and that link the present day Spearfish Creek drainage basin with the modern day Rapid Creek drainage basin. Rapid and Spearfish Creeks both have headwaters in the western Limestone Plateau area at elevations exceeding 7000 feet (2134 meters), Rapid Creek flows in a generally east direction across jgg.ccsenet.org
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