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:

Foundations: emergent themes…Sea-level reconstruction from saltmarsh sedimentsIllustration of high resolution coastal change data from cores

Particle size distribution ‘shape’ as a sea level proxyTesting the hypothesis of palaeo-marsh altitude

Dee (and other UK)Yangtze

Barrier estuary sedimentation: ICOLL dynamics Underlying principlesBarrier regimes

Pescadero

Summary

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.

Altit

ude

Distance

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

Saltmarsh TF reconstructions widely accepted...

BUT:• Dating

• Preservation (Decalcification)

• Compaction

• Reworking (sediment and foraminifera)

• Tidal dynamics and change

1975 1980 1985 1990 1995 2000 2005 20101.0

1.5

2.0

2.5

3.0 OBDMc OBDM3H&E 4b Annual mean sea-level (Liverpool) Monthly mean sea-level (Liverpool)

Alti

tude

(mO

D)

Year

Reconstructed MTL for Mersey Estuary using ‘local’ and ‘hybrid regional’ foram transfer functions compared with Liverpool tide gauge data (Mills, 2011)

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

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

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

All curves Boulderwall Farm 0.44 to 1.44 m OD

0

1

2

3

4

5

6

7

0.1 1 10 100 1000m

% b

ol

‘fast tide’, well-sorted, fine-skewed, leptokurtic fine sands

‘slow tide’, poorly-sorted, near-symmetrical platy- to mesokurtic silts

(Stupples and Plater, 2007)

Infilling

Sea-level Rise

Dee estuary, NW England and N. Wales

0.393

00000

00000

030.5

71

0.829

00000

00000

011.2

041.7

482.5

393.6

87

5.354

99999

99999

87.7

7611.

29 16.423.

8234.

5950.

2372.

94105

.9153

.8223

.4324

.4471

.1684

.2993

.6144

3

0-26-812-1418-2024-2630-3236-3842-4450-5256-5862-6468-7074-7680-8286-8892-94

Particle Size Contour Plot

0-22-44-66-88-1010-1212-1414-1616-1818-2020-2222-2424-2626-2828-3030-3232-34

Grain Size (um)

Dep

th (

cm)

Particle size (μm)

Plotted after Beierle et al. (2002)

Influence of proximity to creeks and microrelief?

Elevation control?

Yangtze Estuary – Chong Xi Tidal Flat Study

Limited micro-topography

Negligible creek network

Consistent gradient

Sediment surplus

6 km

Surface transects across tidal flats: MHWS-MLWS

Distance/elevational control on particle size data and magnetic proxies

0 1 2 3 4 5 602468

1012141618202224262830323436384042

CX-2 Core Palaeomarsh Altitude

TS ratio and Palaeomarsh Altitude

Dep

th (

cm)

Sea-level rise

Palaeomarsh altitude

(No modern analogue)

Pescadero Marsh, California

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

39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 765

6

7

8Depth (cm)

Mea

n G

rain

Siz

e (φ

)

56.2-56.4 cm

41.8-42 cm

48.6-48.8 cm

60.4-60.6 cm

64.8-65 cm

68.8-70 cm

210Pb & 137Cs chronology: approx 5mm/yr

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.

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, Rubina Rahman, 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 Plater gg07@liverpool.ac.uk