Coastal Sediments 2011 Presentation

The Role of Backbarrier Infilling in the Formation of Barrier Island Systems

Christopher Hein and Duncan FitzGerald Coastal Sediments 2011 3 May 2011

Backbarriers & The “Doomsday Scenario”

(FitzGerald et al., 2006, Journal of Coastal Research)

Study Site: Plum Island, MA

Merrimack River

Gulf of Maine

Plum Island Parker River Inlet

N 0

2 km

Cape Ann

Massachusetts Post-Glacial Sea Level History

(Modified from Oldale et al., 1993, Quaternary Research)

Paraglacial Sediment Inputs

(FitzGerald et al., 1993)

Data Collection

N 0

2 km

• 20 km of ground-penetrating radar, 100 & 200 MHz antenna (blue lines) • 7 vibracores, max. 4 m depth (green dots) • 12 Geoprobe cores, max. 15 m (red dots) • 11 auger drill cores, max. 38 m (yellow dots)

Evolution of Plum Island Barrier System 0

0

5 200 10

300

400 15

Channel Fill

5 cm

Channel Weathered Lag Gm

Unweathered Gm

Depth (m)

TWT (nS)

100

Evolution of Plum Island Barrier System

Evolution of Plum Island Barrier System

1

0

MHW

100 150

-4

200 250

3.6 ka -8

Depth (m)

TWT (nS)

50

Northern Massachusetts Calibrated Sea Level Curve

Base of inlet sequence: 3.6 ka

Evolution of Plum Island Barrier System

(Hein et al., in review, Marine Geology)

Research Question 30-50% of barrier length in wave dominated settings (Moslow and Tye, 1985)

Scientific Question: how does a change in tidal fluxes affect island development?

Essex Inlet, MA

FitzGerald et al., in press

Research Question

O’Brien Relationship: Jarrett Curve Paleo-Parker Inlet Inlet Fill Sequence Area: 2800 m2 Equivalent Tidal Prism: 36 x 106 m3

(Jarrett, 1976, USACE Report)

Research Question

TP ~ 32 x 106 m3*

TP >> 32 x 106 m3

(* - Vallino and Hopkinson, 1998, Estuarine, Coastal and Shelf Science)

Stratigraphic Database Barrier Sands Merrimack River

N

0

2 km

Marsh / Peat Tidal Flat

Parker River Rowley River

Parker River Inlet Castle Neck

Backbarrier Sands

Glaciomarine Clay

Till / Bedrock Data: 6 grad theses & 4 govt data sets

Plum Island Stratigraphy: Surface N 156 cores + known elevation points 2 km

3m+ Elevation with respect to MLW (m)

0

-15 m

Plum Island Sound drainage basin

Points tied to MSL

Plum Island Stratigraphy: Backbarrier Sediment Surface N 2 km

3m+ Elevation with respect to MLW (m)

0

156 cores penetrate to backbarrier sediment

-15 m

Backbarrier: strip off marsh, barrier sands, modern organics, etc

Plum Island Stratigraphy: Backbarrier Base N 2 km

3m+ Elevation with respect to MLW (m)

0

63 cores penetrate to backbarrier base

-15 m

Backbarrier Base: basal freshwater peat, glaciomarine clay, till, bedrock Volume of Backbarrier Sediment: 290 x 106 m3

Backbarrier Backstripping If P > 3.6, then B = Bo If P = 0, then B = Bo-(T1*Br) If 3.6 > P > 0, then B = Bo-([T1-(P/Pr)]*Br)

N 2 km

3m+ Elevation with respect to MLW (m)

0

P: marsh / peat thickness (m) T1: time in past B: marsh level at time T1 Bo: modern backbarrier sediment elevation Br: backbarrier sediment accretion rate (0.25 cm/yr) Pr: mean marsh accretion rate (0.1 cm/yr) 3.6: maximum marsh thickness in 3600 yrs

-15 m

T1: 3600 yrs BP

Results N 2 km

3m+ Elevation with respect to MLW (m)

0

Volume Sediment Removed: 225 x 106 m3

-15 m

Backbarrier Tidal Prism: 45 x 106 m3 (140% modern) Modern Parker River Inlet: X-C Area: 3000 m2 TP: 32 x 106 m3

Results

Backstripping Tidal Prism: 45 x 106 m3 3600 Parker River Inlet: Cross-Sectional Area: 1300 m2 Tidal Prism: 18 x 106 m3 Max Paleo-Parker Tidal Prism: 37 x 106 m3 Residual Backbarrier Tidal Prism: ~10 x 106 m3

Implications: Backbarriers & The “Doomsday Scenario”

(FitzGerald et al et al., 2008, Annual Reviews of Earth Science)

Acknowledgements Funding: NSF Graduate Research Fellowship Program, US Minerals Management Service, GSA Graduate Student Research Grant, AAPG Student Grant, AGU Tilford Field Studies Scholarship Field / Lab Assistants: Byron Stone (USGS), Emily Carruthers, (WHOI), Mary Ellison (U. of New Orleans), Nicholas Cohn, Jeff Grey (USGS), Allen Gontz (Umass Boston) Parker River National Wildlife Refuge Staff