Open AccessRiver Warren boulders, Minnesota, USA: catastrophic paleoflow indicators in the southern spillway of glacial Lake Agassiz
Author(s) -
FISHER TIMOTHY G.
Publication year - 2004
Publication title -
boreas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.95
H-Index - 74
eISSN - 1502-3885
pISSN - 0300-9483
DOI - 10.1111/j.1502-3885.2004.tb01245.x
Subject(s) - spillway , geology , meltwater , fluvial , glacial period , bedrock , flood myth , geomorphology , ephemeral key , hydrology (agriculture) , outwash plain , glacial lake , paleontology , archaeology , geotechnical engineering , algorithm , structural basin , computer science , history
Boulders resting on meltwater‐sculpted and striated‐granite bedrock near the head of the southern outlet spillway of glacial Lake Agassiz are used to generate paleodischarge calculations. The rounded nature of many boulders suggests fluvial transport and a corestone origin. The distribution of boulders in clusters and linear trains records the interaction of clasts during transport and deposition. The geomorphology of the spillway with streamlined erosional remnant hills is characteristic of other large flood spillways. Using the Manning equation and a variety of empirical equations to determine paleovelocity, preferred discharges between 0.364 and 0.102 Sv are calculated. These discharges agree well with flood discharges using modeling methodologies, and most likely represent ephemeral and catastrophic flood events linked to either episodic incision at the outlet or the result of rapid inputs of meltwater to Lake Agassiz.