Multiple constraints on the age of a Pleistocene lava dam across the Little Colorado River at Grand Falls, Arizona

Wendell Duffield, Nancy R Riggs, Darrell S Kaufman, Duane Champion, Cassandra Fenton, Steven Forman, William McIntosh, Richard Hereford, Jeffery Plescia, Michael H Ort

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

The Grand Falls basalt lava flow in northern Arizona was emplaced in late Pleistocene time. It flowed 10 km from its vent area to the Little Colorado River, where it cascaded into and filled a 65-m-deep canyon to form the Grand Falls lava dam. Lava continued ∼25 km downstream and ∼1 km onto the far rim beyond where the canyon was filled. Subsequent fluvial sedimentation filled the reservoir behind the dam, and eventually the river established a channel along the margin of the lava flow to the site where water falls back into the pre-eruption canyon. The ca. 150 ka age of the Grand Falls flow provided by whole-rock K-Ar analysis in the 1970s is inconsistent with the preservation of centimeter-scale flow-top features on the surface of the flow and the near absence of physical and chemical weathering on the flow downstream of the falls. The buried Little Colorado River channel and the present-day channel are at nearly the same elevation, indicating that very little, if any, regional downcutting has occurred since emplacement of the flow. Newly applied dating techniques better define the age of the lava dam. Infrared-stimulated luminescence dating of silty mudstone baked by the lava yielded an age of 19.6 ± 1.2 ka. Samples from three noneroded or slightly eroded outcrops at the top of the lava flow yielded 3He cosmogenic ages of 16 ± 1 ka, 17 ± 1 ka, and 20 ± 1 ka. A mean age of 8 ± 19 ka was obtained from averaging four samples using the 40Ar/39Ar step-heating method. Finally, paleomagnetic directions in lava samples from two sites at Grand Falls and one at the vent area are nearly identical and match the curve of magnetic secular variation at ca. 15 ka, 19 ka, 23 ka, and 28 ka. We conclude that the Grand Falls flow was emplaced at ca. 20 ka.

Original languageEnglish (US)
Pages (from-to)421-429
Number of pages9
JournalBulletin of the Geological Society of America
Volume118
Issue number3-4
DOIs
StatePublished - Mar 2006

Fingerprint

lava
dam
Pleistocene
lava flow
river
canyon
downcutting
luminescence dating
secular variation
chemical weathering
river channel
mudstone
emplacement
outcrop
volcanic eruption
basalt
sedimentation
heating
rock
water

Keywords

  • He
  • Ar/Ar
  • Grand Falls lava dam
  • Infrared luminescence
  • Magnetic secular variation
  • Quaternary

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

Multiple constraints on the age of a Pleistocene lava dam across the Little Colorado River at Grand Falls, Arizona. / Duffield, Wendell; Riggs, Nancy R; Kaufman, Darrell S; Champion, Duane; Fenton, Cassandra; Forman, Steven; McIntosh, William; Hereford, Richard; Plescia, Jeffery; Ort, Michael H.

In: Bulletin of the Geological Society of America, Vol. 118, No. 3-4, 03.2006, p. 421-429.

Research output: Contribution to journalArticle

Duffield, Wendell ; Riggs, Nancy R ; Kaufman, Darrell S ; Champion, Duane ; Fenton, Cassandra ; Forman, Steven ; McIntosh, William ; Hereford, Richard ; Plescia, Jeffery ; Ort, Michael H. / Multiple constraints on the age of a Pleistocene lava dam across the Little Colorado River at Grand Falls, Arizona. In: Bulletin of the Geological Society of America. 2006 ; Vol. 118, No. 3-4. pp. 421-429.
@article{31f1ff299bdd40c591a64bc57290593e,
title = "Multiple constraints on the age of a Pleistocene lava dam across the Little Colorado River at Grand Falls, Arizona",
abstract = "The Grand Falls basalt lava flow in northern Arizona was emplaced in late Pleistocene time. It flowed 10 km from its vent area to the Little Colorado River, where it cascaded into and filled a 65-m-deep canyon to form the Grand Falls lava dam. Lava continued ∼25 km downstream and ∼1 km onto the far rim beyond where the canyon was filled. Subsequent fluvial sedimentation filled the reservoir behind the dam, and eventually the river established a channel along the margin of the lava flow to the site where water falls back into the pre-eruption canyon. The ca. 150 ka age of the Grand Falls flow provided by whole-rock K-Ar analysis in the 1970s is inconsistent with the preservation of centimeter-scale flow-top features on the surface of the flow and the near absence of physical and chemical weathering on the flow downstream of the falls. The buried Little Colorado River channel and the present-day channel are at nearly the same elevation, indicating that very little, if any, regional downcutting has occurred since emplacement of the flow. Newly applied dating techniques better define the age of the lava dam. Infrared-stimulated luminescence dating of silty mudstone baked by the lava yielded an age of 19.6 ± 1.2 ka. Samples from three noneroded or slightly eroded outcrops at the top of the lava flow yielded 3He cosmogenic ages of 16 ± 1 ka, 17 ± 1 ka, and 20 ± 1 ka. A mean age of 8 ± 19 ka was obtained from averaging four samples using the 40Ar/39Ar step-heating method. Finally, paleomagnetic directions in lava samples from two sites at Grand Falls and one at the vent area are nearly identical and match the curve of magnetic secular variation at ca. 15 ka, 19 ka, 23 ka, and 28 ka. We conclude that the Grand Falls flow was emplaced at ca. 20 ka.",
keywords = "He, Ar/Ar, Grand Falls lava dam, Infrared luminescence, Magnetic secular variation, Quaternary",
author = "Wendell Duffield and Riggs, {Nancy R} and Kaufman, {Darrell S} and Duane Champion and Cassandra Fenton and Steven Forman and William McIntosh and Richard Hereford and Jeffery Plescia and Ort, {Michael H}",
year = "2006",
month = "3",
doi = "10.1130/B25814.1",
language = "English (US)",
volume = "118",
pages = "421--429",
journal = "Geological Society of America Bulletin",
issn = "0016-7606",
publisher = "Geological Society of America",
number = "3-4",

}

TY - JOUR

T1 - Multiple constraints on the age of a Pleistocene lava dam across the Little Colorado River at Grand Falls, Arizona

AU - Duffield, Wendell

AU - Riggs, Nancy R

AU - Kaufman, Darrell S

AU - Champion, Duane

AU - Fenton, Cassandra

AU - Forman, Steven

AU - McIntosh, William

AU - Hereford, Richard

AU - Plescia, Jeffery

AU - Ort, Michael H

PY - 2006/3

Y1 - 2006/3

N2 - The Grand Falls basalt lava flow in northern Arizona was emplaced in late Pleistocene time. It flowed 10 km from its vent area to the Little Colorado River, where it cascaded into and filled a 65-m-deep canyon to form the Grand Falls lava dam. Lava continued ∼25 km downstream and ∼1 km onto the far rim beyond where the canyon was filled. Subsequent fluvial sedimentation filled the reservoir behind the dam, and eventually the river established a channel along the margin of the lava flow to the site where water falls back into the pre-eruption canyon. The ca. 150 ka age of the Grand Falls flow provided by whole-rock K-Ar analysis in the 1970s is inconsistent with the preservation of centimeter-scale flow-top features on the surface of the flow and the near absence of physical and chemical weathering on the flow downstream of the falls. The buried Little Colorado River channel and the present-day channel are at nearly the same elevation, indicating that very little, if any, regional downcutting has occurred since emplacement of the flow. Newly applied dating techniques better define the age of the lava dam. Infrared-stimulated luminescence dating of silty mudstone baked by the lava yielded an age of 19.6 ± 1.2 ka. Samples from three noneroded or slightly eroded outcrops at the top of the lava flow yielded 3He cosmogenic ages of 16 ± 1 ka, 17 ± 1 ka, and 20 ± 1 ka. A mean age of 8 ± 19 ka was obtained from averaging four samples using the 40Ar/39Ar step-heating method. Finally, paleomagnetic directions in lava samples from two sites at Grand Falls and one at the vent area are nearly identical and match the curve of magnetic secular variation at ca. 15 ka, 19 ka, 23 ka, and 28 ka. We conclude that the Grand Falls flow was emplaced at ca. 20 ka.

AB - The Grand Falls basalt lava flow in northern Arizona was emplaced in late Pleistocene time. It flowed 10 km from its vent area to the Little Colorado River, where it cascaded into and filled a 65-m-deep canyon to form the Grand Falls lava dam. Lava continued ∼25 km downstream and ∼1 km onto the far rim beyond where the canyon was filled. Subsequent fluvial sedimentation filled the reservoir behind the dam, and eventually the river established a channel along the margin of the lava flow to the site where water falls back into the pre-eruption canyon. The ca. 150 ka age of the Grand Falls flow provided by whole-rock K-Ar analysis in the 1970s is inconsistent with the preservation of centimeter-scale flow-top features on the surface of the flow and the near absence of physical and chemical weathering on the flow downstream of the falls. The buried Little Colorado River channel and the present-day channel are at nearly the same elevation, indicating that very little, if any, regional downcutting has occurred since emplacement of the flow. Newly applied dating techniques better define the age of the lava dam. Infrared-stimulated luminescence dating of silty mudstone baked by the lava yielded an age of 19.6 ± 1.2 ka. Samples from three noneroded or slightly eroded outcrops at the top of the lava flow yielded 3He cosmogenic ages of 16 ± 1 ka, 17 ± 1 ka, and 20 ± 1 ka. A mean age of 8 ± 19 ka was obtained from averaging four samples using the 40Ar/39Ar step-heating method. Finally, paleomagnetic directions in lava samples from two sites at Grand Falls and one at the vent area are nearly identical and match the curve of magnetic secular variation at ca. 15 ka, 19 ka, 23 ka, and 28 ka. We conclude that the Grand Falls flow was emplaced at ca. 20 ka.

KW - He

KW - Ar/Ar

KW - Grand Falls lava dam

KW - Infrared luminescence

KW - Magnetic secular variation

KW - Quaternary

UR - http://www.scopus.com/inward/record.url?scp=33645299539&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33645299539&partnerID=8YFLogxK

U2 - 10.1130/B25814.1

DO - 10.1130/B25814.1

M3 - Article

VL - 118

SP - 421

EP - 429

JO - Geological Society of America Bulletin

JF - Geological Society of America Bulletin

SN - 0016-7606

IS - 3-4

ER -