TY - JOUR
T1 - Rapid regolith formation over volcanic bedrock and implications for landscape evolution
AU - Dosseto, Anthony
AU - Buss, Heather L
AU - Suresh, P O
PY - 2012/7/1
Y1 - 2012/7/1
N2 - The ability to quantify how fast weathering profiles develop is crucial
to assessing soil resource depletion and quantifying how landscapes
evolve over millennia. Uranium-series isotopes can be used to determine
the age of the weathering front throughout a profile and to infer
estimates of regolith production rates, because the abundance of
U-series isotopes in a weathering profile is a function of chemical
weathering and time. This technique is applied to a weathering profile
in Puerto Rico developed over a volcaniclastic bedrock. U-series isotope
compositions are modelled, revealing that it takes 40–60 kyr to develop
an 18 m-thick profile. This is used to estimate an average regolith
production rate of 334±46 mm/kyr. This value is higher by a factor of up
to 30 when compared to production rates estimated for weathering
profiles developed over granitic or shale lithologies. This quantitatively
underpins the lithological control on rates of regolith production (in a
neighbouring watershed but over a granitic bedrock, production rates
are only ∼30–40 mm/kyr). Moreover, by comparing these results to a
compilation of soil erosion rates, it is clear that landscapes are
controlled by the balance (or imbalance) between regolith production and
erosion: soil-mantled landscapes are the result of a relative balance
between production and erosion, whereas in cratonic areas, thicker
weathering profiles are generated because erosion fails to match
regolith production rates.
AB - The ability to quantify how fast weathering profiles develop is crucial
to assessing soil resource depletion and quantifying how landscapes
evolve over millennia. Uranium-series isotopes can be used to determine
the age of the weathering front throughout a profile and to infer
estimates of regolith production rates, because the abundance of
U-series isotopes in a weathering profile is a function of chemical
weathering and time. This technique is applied to a weathering profile
in Puerto Rico developed over a volcaniclastic bedrock. U-series isotope
compositions are modelled, revealing that it takes 40–60 kyr to develop
an 18 m-thick profile. This is used to estimate an average regolith
production rate of 334±46 mm/kyr. This value is higher by a factor of up
to 30 when compared to production rates estimated for weathering
profiles developed over granitic or shale lithologies. This quantitatively
underpins the lithological control on rates of regolith production (in a
neighbouring watershed but over a granitic bedrock, production rates
are only ∼30–40 mm/kyr). Moreover, by comparing these results to a
compilation of soil erosion rates, it is clear that landscapes are
controlled by the balance (or imbalance) between regolith production and
erosion: soil-mantled landscapes are the result of a relative balance
between production and erosion, whereas in cratonic areas, thicker
weathering profiles are generated because erosion fails to match
regolith production rates.
KW - soil
KW - weathering
KW - isotope geochemistry
KW - uranium-series disequilibrium
KW - Puerto Rico
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84862321717&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2012.05.008
DO - 10.1016/j.epsl.2012.05.008
M3 - Article (Academic Journal)
AN - SCOPUS:84862321717
SN - 0012-821X
VL - 337-338
SP - 47
EP - 55
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -