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Particle size evidence of recent coastal change. Andy Plater

Particle size evidence of recent coastal change. Andy Plater …featuring Dave Clarke, Hayley Mills, Joe Brennan, Weiguo Zhang, Rubina Rahman , James Walker and Samantha Godfrey School of Environmental Sciences, University of Liverpool. Bridging Operational Scales. Seminar structure:

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Particle size evidence of recent coastal change. Andy Plater

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  1. Particle size evidence of recent coastal change. Andy Plater …featuring Dave Clarke, Hayley Mills, Joe Brennan, Weiguo Zhang, RubinaRahman, James Walker and Samantha Godfrey School of Environmental Sciences, University of Liverpool

  2. Bridging Operational Scales...

  3. Seminar structure: Foundations: emergent themes… Sea-level reconstruction from saltmarsh sediments Illustration of high resolution coastal change data from cores Particle size distribution ‘shape’ as a sea level proxy Testing the hypothesis of palaeo-marsh altitude Dee (and other UK) Yangtze Barrier estuary sedimentation: ICOLL dynamics Underlying principles Barrier regimes Pescadero Summary

  4. Saltmarsh Data: Foraminiferal Transfer Function As the surface of a saltmarsh slopes towards the sea, areas of a saltmarsh differ in the amount of tidal submergence and sub-aerial exposure - related to elevation. Different species assemblages occupy different altitudes or height above sea-level. Intertidal foraminifera can be used to reconstruct palaeo-sea level as their distribution may be related to height above sea-level. Altitude Distance

  5. Kemp, A.C. et al. (2011) Climate related sea-level variations over the past two millennia. PNAS doi/10/1073

  6. Saltmarsh TF reconstructions widely accepted... • BUT: • Dating • Preservation (Decalcification) • Compaction • Reworking (sediment and foraminifera) • Tidal dynamics and change Reconstructed MTL for Mersey Estuary using ‘local’ and ‘hybrid regional’ foram transfer functions compared with Liverpool tide gauge data (Mills, 2011)

  7. Can we obtain high resolution ‘process’ information from sediment record of palaeoenvironments?

  8. Rhythmites: imperfect preservation of tidal inundation magnitude/frequency in laminae

  9. Re-examining particle size distributions • Sediments are present! • More robust than palaeoecological proxies (generally!) • Relationship with tidal flow vector – a function of tidal height • Rapid, high-resolution analysis ‘fast tide’, well-sorted, fine-skewed, leptokurtic fine sands ‘slow tide’, poorly-sorted, near-symmetrical platy- to mesokurtic silts (Stupples and Plater, 2007)

  10. Infilling Sea-level Rise

  11. Dee estuary, NW England and N. Wales

  12. Elevation control? Influence of proximity to creeks and microrelief?

  13. Yangtze Estuary – Chong Xi Tidal Flat Study Limited micro-topography Negligible creek network Consistent gradient Sediment surplus

  14. 6 km Surface transects across tidal flats: MHWS-MLWS Distance/elevational control on particle size data and magnetic proxies

  15. Palaeomarsh altitude Sea-level rise (No modern analogue)

  16. Pescadero Marsh, California

  17. Mean particle size base level sections: • Barrier regimes • Variability between end-member states • Aggregate state of barrier estuary / lagoon • Disturbance and recovery • High energy events

  18. 48.6-48.8 cm 64.8-65 cm 68.8-70 cm 60.4-60.6 cm 41.8-42 cm 210Pb & 137Cs chronology: approx 5mm/yr

  19. Summary Particle size (shape) data show considerable potential for saltmarsh/mudflat elevation reconstruction... as well as providing data on changing coastal environments and hydro/morphodynamics (long-, medium- and short-term), e.g. estuary infilling, barrier regime shifts, disturbance/recovery etc. Data do not suffer from occurrence or preservation issues, but may suffer from methodological issues re. analytical method/ particle shape Technique is rapid and capable of very high resolution analysis At the very minimum, particle size data are valuable for assessing viability of a sediment record for sea-level reconstruction (infilling vs. sea level, also disturbance) Issues remain in relation to microtopography and creek proximity – as well as sub-annual variability and extreme events BUT at least the data reveal such phenomena.

  20. Additional thanks to: Weiguo Zhang and colleagues, Stake Key Laboratory for Estuarine and Coastal Research Ken Pye, KPAL Jimmy Zheng, Joe Brennan and many postgraduates from East China Normal University Jason Kirby, Liverpool John Moores University Sandra Mather, Hayley Mills, Dave Clarke, RubinaRahman, Tim Shaw, James Walker, Paul Stupples, Dan Schillerreff and Samantha Godfrey, University of Liverpool Simon Holgate, Svetlana Jevrejeva and Phil Woodworth, National Oceanography Centre-Liverpool Thanks for your attention – Andy Platergg07@liverpool.ac.uk

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