9510

• UCREFRP Catalog Number: 9510
• Author: Jones, A. T.
• Title: A Cross Section of Grand Canyon Archeology
• USFW Year: 1986.
• USFW - Doc Type: Excavations at Five Sites Along the Colorado River.
• Copyright Material: NO

Chapter 2
PHYSIOGRAPH IC CONTEXT FOR TH~EE ARCHEOLOGICAL SITES

by
Eric T. Karl strom

Introduction

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Physiography
Three of the fi ve si tes desc ri bed in thi s report were bri efly
investigated by the author in May 1984. The geomorphology of these
sites, ftJ... A:16:1, AZ B:15:7, and AZ C:13:10, is discussed at the end of
this chapter. AZ B:10:4 and AZ C:13:4 were not visited by the author
because, as a safety precaution, these were backfilled immediately after
'excavation. \~hile the specific geomorphology of the latter two sites
cannot be di scussed here, probah le ori gins of sediments associ ated wi th
the cultural deposits, based on discussion wjth Jones, are described in
Chapter 5. The follO\'1ing discussion of Grand Canyon physiography,
(including geology, climate and vegetation) and of late Quaternary
alluvial processes and geomorphic features should be useful when
~onsidering each of the five sites.
The Colorado Ri ver is one of the master streams of the American
Southwest and drains an area of about 650,000 km2 (250,000 square
mil es), incl uding parts of the Rocky Mountain and Basin and Range
physiographic provinces and roughly nine-tenths of the Colorado Plateau
province (Thornbury 1969). Just below Marble Canyon and its confluence
with the Little Colorado River, the Colorado River turns west and slices
across the KaibabUpwarp, exposing about a vertical mile of Paleozoic
and Precambri an rocks and formi ng the Grand Canyon. The Colorado Ri ver
itself drops from an elevation of about 949 m (3,112 feet) at Lee1s
Ferry just below Glen Canyon Dam to an elevation of 366 m(1,200 feet)
at Lake Mead some 448 km (280 ~iles) downstream. The Grand Canyon gorge
ranges ~et\"een 6.4 and 25 km wide \'Jith an average of about 16 kill
(9.9 l11i 1 es ).
The tributaries to the Colorado River in the Grand Canyon commonly
follow generally north-south trending faults and commonly have gradients

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