Calibrating denudation chronology through 40Ar/39Ar weathering geochronology

Vasconcelos, Paulo M. and Carmo, Isabela de O. (2018) Calibrating denudation chronology through 40Ar/39Ar weathering geochronology. Earth-Science Reviews, 179 411-435. doi:10.1016/j.earscirev.2018.01.003

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Author Vasconcelos, Paulo M.
Carmo, Isabela de O.
Title Calibrating denudation chronology through 40Ar/39Ar weathering geochronology
Journal name Earth-Science Reviews   Check publisher's open access policy
ISSN 0012-8252
Publication date 2018-02-15
Year available 2018
Sub-type Critical review of research, literature review, critical commentary
DOI 10.1016/j.earscirev.2018.01.003
Open Access Status File (Author Post-print)
Volume 179
Start page 411
End page 435
Total pages 25
Place of publication Amsterdam, NX Netherlands
Publisher Elsevier
Language eng
Subject 1900 Earth and Planetary Sciences
Abstract Classical geomorphological models identify regional erosion surfaces and raise hypotheses, currently abandoned but largely untested, about the cumulative effects of tectonics and climate on the evolution of continental landscapes. Weathering geochronology provides the appropriate tool for testing these models. New and published Ar/Ar geochronology of 346 grains of Mn oxides extracted from weathering profiles representing four regionally recognized landsurfaces in southeastern Brazil reveals that weathering minerals record minimum ages for the surfaces hosting the weathering profiles. Weathering profiles at the highest elevation surfaces are as old as ~70 Ma; those at intermediate surfaces formed post ~13 Ma; incipient profiles at incised valleys range from ~4–1 Ma; and the shallowest and least evolved weathering profiles at coastal plains yield ~1.0–0.8 Ma ages. The oldest and highest elevation landsurfaces are blanketed by deep (>150 m) chemically stratified lateritic profiles; intermediate surfaces host deep saprolites (ca. 40–60 m) capped by regional stone lines; and shallow (5–20 m) and young weathering profiles cover the more deeply dissected parts of the landscape within intracontinental valleys and along the coastal plains. The hierarchy in ages and elevations for the weathering profiles suggests that the landscape in southeastern Brazil evolved through alternation of weathering-prone periods interrupted by periods of uplift and widespread incision. The denudation chronology model derived from weathering geochronology is compatible with the sedimentary record in adjacent offshore sedimentary basins. It is also compatible with erosion rates measured by cosmogenic isotopes for each of the separate landsurfaces. The results reveal that landscapes in the region are not in dynamic equilibrium and that they evolved by episodic uplift followed by denudation along retreating escarpments.
Keyword K-Mn Oxides
Term Landscape Evolution
South-American Plate
Fission-Track Data
Quadrilatero Ferrifero
Cosmogenic Be-10
Se Brazil
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID 2000/04208-5
Institutional Status UQ

Document type: Journal Article
Sub-type: Critical review of research, literature review, critical commentary
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School of Earth Sciences Papers
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Created: Thu, 22 Mar 2018, 23:31:43 EST