Response to Comments on the "Age and Evolution of the Grand Canyon Revealed by U-Pb Dating of Water Table–Type Speleothems"

Polyak, Victor J.; Hill, Carol A.; Asmerom, Yemane

doi:10.1126/science.1159762

Cited by 4 publications

(1 citation statement)

References 9 publications

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“…Kr-Ar, U-Pb and U-series, CIA, OSL) is helping to advance understanding of the timing and rates of change but considerable controversies remain, as is evident from some recent provocatively titled articles. In line with earlier estimates of an 'old' canyon, some researchers suggest that incision in western Grand Canyon began as early as 17 Ma (Polyak et al, 2008a(Polyak et al, , 2008b, but a broader consensus seems to favour a downward age revision, arguing for a relatively 'young' canyon that started to be cut *5-6 Ma (see, for example, Karlstrom et al, 2008;Pearthtree et al, 2008;Pederson et al, 2008).…”

Section: Perspectives On Timescales Of Changementioning

confidence: 59%

Arid geomorphology

Tooth

2011

Progress in Physical Geography: Earth and Environment

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Arid geomorphological research continues apace with publications appearing in a diverse range of outlets. Themes common to several recent (2008)(2009) books include greater emphasis on the global diversity of arid environments, the improved temporal framework for research findings, and the growing contribution of arid geomorphology to interdisciplinary research fields. Building on previous progress reports, this article touches on all three themes, but particularly highlights how applications of geochronology (e.g. cosmogenic isotope analysis, luminescence dating, and radiocarbon dating) are challenging or revolutionizing understanding of the timing and rates of arid geomorphological change. Four case studies from 'iconic' arid landscapes illustrate changes over different timescales: (1) canyons of the Colorado Plateau region, southwest USA (last *5-6 Ma); ( 2) aeolian dunefields in central Australia (last *1 Ma); (3) palaeolakes in the Kalahari, central southern Africa (last *300 ka); and (4) alluvial and bedrock-controlled rivers in the southwest USA (last *12 ka). Other developments across the suite of geochronological techniques are also contributing to improved understanding of arid landscape dynamics and the links with late Cenozoic environmental changes, biological (including hominin) evolution and cultural developments, but many outstanding issues remain. These include: (1) compiling large geochronological data sets to enable rigorous hypothesis testing;(2) establishing guiding conceptual frameworks to aid the selection and interpretation of geochronological data;(3) using multiple chronometers; (4) combining geochronology with other investigative techniques such as computational modelling; and (5) clarifying the causal links between events in different palaeorecords, even when temporal correlation can be established with a high degree of certainty. Despite recent rapid advances, today's understanding of the antiquity and tempo of landscape development in Earth's arid environments undoubtedly will be challenged and extended by further research, with particularly valuable perspectives likely to be provided by arid geomorphological research on other planetary bodies.

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Section: Perspectives On Timescales Of Changementioning

confidence: 59%

Arid geomorphology

Tooth

2011

Progress in Physical Geography: Earth and Environment

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A karst hydrology model for the geomorphic evolution of Grand Canyon, Arizona, USA

Hill

Polyak

2020

Earth-Science Reviews

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The California River and its role in carving Grand Canyon

Wernicke

2011

Geological Society of America Bulletin

112

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Recently published thermochronological and paleoelevation studies in the Grand Canyon region, combined with sedimentary provenance data in both the coastal and interior portions of the North American Cordillera, place important new constraints on the paleohydrological evolution of the southwestern United States. Review and synthesis of these data lead to an interpretation where incision of a large canyon from a plain of low elevation and relief to a canyon of roughly the length and depth of modern Grand Canyon occurred primarily in Campanian time (80-70 Ma). Incision was accomplished by a main-stem, NE-fl owing antecedent river with headwaters on the NE slope of the North American Cordillera in California, referred to herein after its source region as the California River. At this time, the river had cut to within a few hundred meters of its modern erosion level in western Grand Canyon, and to the level of Lower Mesozoic strata in eastern Grand Canyon. Subsequent collapse of the head waters region into a continental border land and coeval uplift of the Cordilleran foreland during the Laramide orogeny reversed the river's course by Paleogene time. After reversal, its terminus lay near its former source regions in what is now the Western Transverse Ranges and Salinian terrane. Its headwaters lay in the ancient Mojave/Mogollon Highlands region of Arizona and eastern California, apparently reaching as far northeast as the eastern Grand Canyon region. This system is herein referred to after its source region as the Arizona River. From Paleogene through late Miocene time, the interior of the Colorado Plateau was a closed basin separated from the Arizona River drainage by an asymmetrical divide in the Lees Ferry-Glen Canyon area, with a steep SW fl ank and gently sloping NE fl ank that drained into large interior lakes, fed primarily by Cor dilleran/Rocky Mountain sources to the north and west, and by recycled California River detritus shed from Laramide uplifts on the plateau. By Oligocene time, the lakes had largely dried up and were replaced by ergs. By mid-Miocene time, a pulse of unroofi ng had lowered the erosion level of eastern Grand Canyon to within a few hundred meters of its present level, and the Arizona River drainage below modern Grand Canyon was deranged by extensional tectonism, cutting off the supply of interior detritus to the coast. Increasing moisture in the Rocky Mountains in late Miocene time reinvigorated fl uvio lacustrine aggradation NE of the asymmetrical divide, which was fi nally overtopped between 6 and 5 Ma, lowering base level in the interior of the plateau by 1500 m. This event reintegrated the former Arizona drainage system through a cascade of spillover events through Basin and Range valleys, for the fi rst time connecting sediment sources in Colorado with the coast. This event, combined with the intensifi cation of summer rainfall as the Gulf of California opened, increased the sediment yield through Grand Canyon by perhaps two orders of magnitude from its Miocene nadir, giving birth t...

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Response to Comments on the "Age and Evolution of the Grand Canyon Revealed by U-Pb Dating of Water Table–Type Speleothems"

Cited by 4 publications

References 9 publications

Arid geomorphology

Arid geomorphology

A karst hydrology model for the geomorphic evolution of Grand Canyon, Arizona, USA

The California River and its role in carving Grand Canyon

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