 |
| Titel |
Quantifying site-specific Holocene soil erosion using depth-profiles of cosmogenic in-situ 14C and 10Be |
| VerfasserIn |
R.-H. Fülöp, P. Bishop, D. Fabel, G. T. Cook, C. Schnabel, P. Naysmith, S. Xu |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024498
|
|
|
|
|
|
| Zusammenfassung |
| The sustainable use of soils represents one of the key challenges that society faces.
Glacial sediments (tills and moraines) form the parent material of soils in many
parts of the northern hemisphere but little is known about the histories of these
soils. Several methods of estimating soil erosion exist but these have limitations,
mainly in that they are unable to quantify at-a-site soil erosion rates over Holocene
timescales.
The cosmogenic exposure age of an erratic on a moraine is an estimate of the
moraine’s age and an uneroded soil/till on the moraine must have the same total
cosmogenic nuclide inventory as the erratic given that they have been exposed to
cosmic radiation for the same lenght of time. Any cosmogenic nuclide inventory
shortfall in the soil/till is therefore a measure of loss, most likely by erosion but
also potentially by other mechanisms. Depth-profiles of two cosmogenic nuclides
of substantially different half-lives and production rates, such as 10Be and 14C,
should indicate the timing of any erosion that is identified, with a broad resolution
to, for example, Middle or Late Holocene. If the technique proves successful, it
will provide for the first time a means of measuring and broadly dating Holocene
at-a-site soil erosion, complementing techniques that rely on basin sedimentation to
assess catchment-wide average soil erosion based on sediment flux to receiving
basins.
We are assessing these principles using the soil formed on the Younger Dryas Loch
Lomond Readvance moraine near Glasgow. 10Be determinations on vein quartz in erratics on
the moraine surface yield a mean exposure age of 10,500 ± 900 years confirming the
Younger Dryas age of the moraine. Eighteen 10Be determinations in till material of varying
size fractions collected from a depth-profile in a 240 cm pit from the moraine crest confirm
that the cosmogenic nuclide depth-profile to be expected from a sediment body
of Holocene age can be reconstructed and, thus, the technique can be applied for
estimating amounts and timing of at-a-site Holocene soil erosion. Moreover, the
agreement between the cosmogenic 10Be results in the erratics and till samples indicate
that there has been no soil erosion at the sample site since the deposition of the
till/moraine.
This interpretation is now being tested more rigorously using in-situ 14C data from
erratics and clasts in the depth-profile in the till/moraine. |
|
|
|
|
|
|