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| Titel |
Debris flow fans as sensitive recorders of glacial-interglacial climate change in the south-western United States |
| VerfasserIn |
Mitch D'Arcy, Duna Roda Boluda, Alex Whittaker |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091556
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| Publikation (Nr.) |
 EGU/EGU2014-5857.pdf |
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| Zusammenfassung |
| Tectonics and climate are major forces shaping the morphological evolution of the landscape,
and are recorded geomorphically and stratigraphically over response timescales that may vary
across several orders of magnitude. Although the responses of geomorphic systems to
tectonic perturbations have been well studied in recent years, far less is understood about the
effects of climate change. A number of landscape evolution models predict that the sediment
flux and grain size distribution exported from mountain catchments to alluvial fan
systems may be highly responsive to glacial-interglacial climate changes. This
implies that the sedimentology of alluvial fan deposits should record important
information about how eroding mountain landscapes have reacted to past climate changes.
However, a lack of targeted, empirical field data means we have not yet tested model
hypotheses or constrained the magnitudes, mechanisms and characteristic timescales with
which these systems have responded to climate variability in the past. This is a
key challenge for building accurate landscape evolution models with predictive
powers, and understanding how climatic information is recorded by geomorphic
systems.
In this study, we present a new, detailed stratigraphic record from 8 mapped and dated
debris flow fans in southern Owens Valley, California. These fans have a continuous
depositional record extending back more than 150 ka, which we use to examine how the
sediment grain size and flux from Sierra Nevada catchments has varied as a function of high
amplitude climate change during the last glacial-interglacial cycle. We find that
this sedimentological data is highly correlated with the palaeoclimate record, with
depositional events becoming significantly larger in size and 2-3 times coarser in
grain size as the climate warmed and dried. The quantitative relationships that we
identify between high frequency climate change and sustained responses in the
sedimentology of these catchment-fan systems reveals that they are highly sensitive to
climate forcing with a relatively rapid response timescale of -¤ 104years. This is
faster than many current landscape evolution models hypothesize. We demonstrate
that a climatic signal is measurable and consistent across 8 discrete catchment-fan
systems in Owens Valley, and discuss the implications of this for signal shredding by
autocyclic fan processes. This is one of the first detailed, empirical tests of the
sensitivity of fan deposition to climate variability over time, in a region where the
palaeoclimate record is very well constrained. Our findings confirm that climate changes are
expressed in alluvial fan sedimentology, making it possible to calibrate landscape
evolution models using new field data with a high spatial and temporal resolution. |
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