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GEOREF RECORD

Valley-fill alluviation during the Little Ice Age (ca. A.D. 1400-1880), Paria River Basin and southern Colorado Plateau, United States

Richard Hereford
Valley-fill alluviation during the Little Ice Age (ca. A.D. 1400-1880), Paria River Basin and southern Colorado Plateau, United States
Geological Society of America Bulletin (December 2002) 114 (12): 1550-1563

Abstract

Valley-fill alluvium deposited from ca. A.D. 1400 to 1880 is widespread in tributaries of the Paria River and is largely coincident with the Little Ice Age epoch of global climate variability. Previous work showed that alluvium of this age is a mappable stratigraphic unit in many of the larger alluvial valleys of the southern Colorado Plateau. The alluvium is bounded by two disconformities resulting from prehistoric and historic arroyo cutting at ca. A.D. 1200-1400 and 1860-1910, respectively. The fill forms a terrace in the axial valleys of major through-flowing streams. This terrace and underlying deposits are continuous and interfinger with sediment in numerous small tributary valleys that head at the base of hillslopes of sparsely vegetated, weakly consolidated bedrock, suggesting that eroded bedrock was an important source of alluvium along with in-channel and other sources. Paleoclimatic and high-resolution paleoflood studies indicate that valley-fill alluviation occurred during a long-term decrease in the frequency of large destructive floods. Aggradation of the valleys ended about A.D. 1880, if not two decades earlier, with the beginning of historic arroyo cutting. This shift from deposition to valley entrenchment near the close of the Little Ice Age generally coincided with the beginning of an episode of the largest floods in the preceding 400-500 yr, which was probably caused by an increased recurrence and intensity of flood-producing El Nino events beginning at ca. A.D. 1870.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 114
Serial Issue: 12
Title: Valley-fill alluviation during the Little Ice Age (ca. A.D. 1400-1880), Paria River Basin and southern Colorado Plateau, United States
Author(s): Hereford, Richard
Affiliation: U. S. Geological Survey, Flagstaff, AZ, United States
Pages: 1550-1563
Published: 200212
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 104
Accession Number: 2002-079365
Categories: Geomorphology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 3 tables, geol. sketch map
N37°00'00" - N37°07'30", W112°15'00" - W112°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200224
Program Name: USGSOPNon-USGS publications with USGS authors
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