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| Titel |
Is their a distinctive difference between climate and tectonically driven increases in sediment flux? |
| VerfasserIn |
John Armitage, Stefan Schmalholz |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250077171
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| Zusammenfassung |
| The sedimentary record contains the only time dependent record of past climate and
tectonics. As we increasingly probe this archive for information of change in the Earth’s past,
it is becoming essential to understand how this system responds to change. As an example,
during the middle Miocene both the Eastern North American Margin and the northern
margins of the South China Sea recorded a rapid increase in sediment accumulation, which
may be a signal of global change in the Earth’s climate leading to increased precipitation
derived run-off.
Variations in sediment flux can be estimated from preserved stratigraphy, cosmogenic
nuclitide methods and low-temperature thermochronolgy, but a general quantative model
of sediment fluxes remains a research challenge. There exist an array of complex
models of sediment transport, which are capable of re-creating realistic morphologies.
However, all that remains of the ancient landscape are the sediments deposited, and
this record is a partial one at best. Given that observations are incomplete, it is
difficult to justify the use of hydrological models for geological problems. Instead we
present a simple, somewhat heuristic, advective-diffusive model of sediment transport
coupled to lithosphere flexure with the aim of capturing the basics of landscape
evolution.
For this idealised system, an increase in surface uplift causes a gradual increase in
sediment flux as erosion takes time to react to the new topography. In contrast, when the
system is subject to a increase in surface run-off, there is a rapid increase in sediment delivery
to the basin. This is due to the erosive power instantly increasing, causing increased removal
of sediment. Interestingly, if the elastic thickness of the lithosphere is low, the unloading of
the upland areas causes a flexural response that balances erosion and maintains high sediment
discharge. If the thickness is high, the flexural response does not keep pace with erosion, and
sediment fluxes reduce as topography is eroded down. The rapid response of the
predicted sediment delivery out of the catchment to change in run-off versus the slow
response to uplift may prove to be a diagnostic tool to decode the sedimentary record. |
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