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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

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DOI: 10.1130/0016-7606(2002)114<1550:VFADTL>2.0.CO;2

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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 occured 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 Nin??o events beginning at ca. A.D. 1870.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Valley-fill alluviation during the Little Ice Age (ca. A.D. 1400-1880), Paria River basin and southern Colorado Plateau, United States
Series title:
Geological Society of America Bulletin
DOI:
10.1130/0016-7606(2002)114<1550:VFADTL>2.0.CO;2
Volume
114
Issue:
12
Year Published:
2002
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geological Society of America Bulletin
First page:
1550
Last page:
1563
Number of Pages:
14