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Some Uncertainties in the Derivation of Rates of Denudation from Thermochronologic Data
Author(s) -
Brown Roderick W.,
Summerfield M. A.
Publication year - 1997
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/(sici)1096-9837(199703)22:3<239::aid-esp751>3.0.co;2-b
Subject(s) - denudation , thermochronology , geology , fission track dating , closure temperature , advection , crust , geomorphology , geophysics , tectonics , seismology , geochemistry , zircon , physics , thermodynamics
Low‐temperature thermochronology, such as that provided by apatite fission‐track analysis, provides a valuable means of establishing the timing of major denudational events and associated rates of denudation over geological time‐scales of 10 6 –10 8 Ma. Care must be taken, however, in deriving denudation rates from the crustal cooling histories documented by thermochronologic techniques, especially in rapidly eroding terrains, since, in such cases, apparent denudation rates derived from thermochronologic data will usually overestimate true rates if the advective effect of denudation is not included. This is likely to be resolvable where the rate of denudation exceeds 300 m Ma −1 and when the depth of denudation occurring at these rates exceeds several kilometres prior to the sample cooling below the appropriate closure temperature. Because the time at which a sample cools below a particular closure temperature is relatively insensitive to advection, the initiation of denudation can be accurately established, even given uncertainties in the estimation of depths and rates of denudation. Where thermal events originate from a source within or below the lower crust, the cooling through denudation will dominate the low‐temperature history of the shallow crust if denudation occurs coevally with the subsurface heating. © 1997 by John Wiley & Sons, Ltd.