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SUMMARY:Constraining sediment routing system responses to tectonics and cl
 imate - Alex Whittaker\, Imperial College
DTSTART:20151027T160000Z
DTEND:20151027T170000Z
UID:TALK59475@talks.cam.ac.uk
CONTACT:John Maclennan
DESCRIPTION:Both tectonics and climate profoundly influence the erosional-
 depositional processes that shape the Earth’s surface1\,2.  Moreover\, t
 he magnitude\, locus and characteristics of sediment export from catchment
 s to basins play a fundamental role in determining depositional stratigrap
 hy.  While progress has been made in understanding the response of erosion
 al-depositional systems to tectonics\, the extent to which sediment routin
 g systems are either sensitive\, or are buffered\, to rapid climate change
  remains extremely contentious3. \n\nA good way to address this fundamenta
 l question is to examine the sedimentary record\, because this constitutes
  the only physical archive we have of mass transport across Earth’s surf
 ace as a function of past climate4. Terrestrial sediments have the potenti
 al to preserve the erosional record of upland landscape response to high-f
 requency climate forcing\, while advances in exposure-age dating now enabl
 e detailed time-series of sediment characteristics\, such as grain size\, 
 to be compared quantitatively with known palaeo-climate archives. Here\, w
 e use exceptionally well-constrained data from the Sierra Nevada\, Califor
 nia\, to demonstrate that the sediment characteristics and channel widths 
 of alluvial fan deposits capture orbitally-induced climate fluctuations wi
 th high fidelity over a complete glacial-interglacial cycle.  For examples
  from Owen’s Valley\, we demonstrate that the grain sizes of these sedim
 ents scale with Pacific sea surface temperature reconstructions for the la
 st 140 ka\, increasing systematically with ocean surface warming.  We prop
 ose this signal is driven by changes in surface runoff\, controlled by the
  magnitude and intensities of flow-triggering storms. Our results (i) prov
 ide new constraints on the sensitivity of sediment routing systems to clim
 ate changes of known magnitude\; (ii) show that the response time of these
  systems to climate change can be rapid (≤104 years)\; and (iii) demonst
 rate that stratigraphy can be successfully inverted for past environmental
  changes where transport and deposition rates are high.\n\nReferences\n\n1
 Whittaker\, A. C.\, 2012\, How do landscapes record tectonics and climate?
  Lithosphere\, 4\, 160-164.\n\n2Armitage\, J.\, Duller R. A.\, Whittaker\,
  A. C.\, and Allen\, P. A.\, 2011\, Transformation of tectonic and climati
 c signals from source to sedimentary archive\, Nature Geoscience\, 4\, 231
 -235. \n\n3Armitage\, J.\, Dunkley Jones\, T.\, Whittaker\, A.C.\, \, Alle
 n\, P.A.\, 2013\, Temporal buffering of climate-driven sediment flux cycle
 s by transient catchment responses\, Earth and Planetary Science Letters\,
  369-370\, 200 -210.  \n\n4Michael\, N. A.\, Whittaker\, A. C.\, Carter\, 
 A.\, Allen P. A.\, 2014\, Volumetric budget and grain-size fractionation o
 f a geological sediment routing system: Eocene Escanilla Formation\, South
 -Central Pyrenees\, GSA Bulletin\, 126\, 585-599\n
LOCATION:Harker 1 seminar room\, Department of Earth Sciences
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