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EP43A-060 EP43A-060

The Role of Backbarrier Filling in the Evolution of a Barrier Island System Christopher Christopher J. J. Hein Hein (hein@bu.edu) (hein@bu.edu) ,, Duncan Duncan M. M. FitzGerald FitzGerald ,, Byron Byron D. D. Stone Stone ,, Emily Emily A. A. Carruthers Carruthers ,, Allen Allen M. M. Gontz Gontz 11

Sea-Level Curves: 40

Elevation (m)

-60

Oldale et al, 1993 0

4

J

8

Park

er R

iver

Highlighted region shown in Stages II - V

Small southern inlet

STAGE III

STAGE IV

Long Shore Current

Backbarrier Infilling

Spit progradation over closing inlet

-8

Hein et al (this study) Donnelly, 2006

-12

McIntire and Morgan, 1964 Redfield, 1967

-16

Keene, 1971 Lyon and Harrison, 1960

0

2

4

6

STAGE IV: Closure of Parker Inlet STAGE V

• Inlet shoals and narrows due to reduced tidal prism • LST causes southerly spit progradation & migration of inlet; increased backbarrier infilling

STAGE VI

Long Shore Current

8

Calibrated Age (kyr B.P.)

STAGE V: Rapid Spit Progradation Spit progradation over intertidal sediment

STAGE VI: Barrier Island Stabilization Drumlins

Barrier Sediment

Subtidal Sand Shoal

Marsh

Low Intertidal

High Intertidal

Channel

• Plum Island progrades with sediment from Merrimack River • Parker R. joins Rowley R. and Ipswich R. as a single estuary with one inlet stabilized between two drumlins (Parker Inlet)

100

4 150

5 6 7

Truncation

B

10

KEY: Blue Lines: GPR transects (100 & 200 MHz antennas) Bold Colored Lines: profiles A-D Red Circles (12): Geoprobe cores Yellow Circles (11): auger drill cores Green Circles (7): vibracores

SPIT / INLET SEQUENCE

4 6

0

Parker River

CHANNEL FILL

8

14

100 m

300

C

GLACIOMARINE CLAY

Rowley River

14 km

Parker River Inlet Castle Neck

3m+

Methods: • 179 cores (red circles, published 19631990) & 30 new cores (this study)

-15 m

14 km

25 m

TP =

• Data (209 cores, channel and backbarrier boundaries) interpolated (linear variogram kriging) to produce model of backbarrier sediment surface • Gridded DGM represents backbarrier region after marsh and barrier sediments have been removed

• 65 cores penetrated surface below backbarrier sediments • Resulting DGM shows smooth, seaward dipping basal backbarrier surface

1010

Legend

108 3 10

• Backbarrier Sediment Volume (calculated): 850 x 106 m3 (~10x sediment volume of Plum Island)

Backstripped Backbarrier Model:

• Facies surfaces gridded to produce digital geologic maps (DGM) to the right

3m+

• Base of backbarrier sediments given as glaciomarine clay, shallow bedrock, or till • Backbarrier sediments “backstripped” using published (McIntire & Morgan, 1964) and unpublished (this study) marsh & backbarrier accretion rates

-15 m

0 -5 -10

14 km

• Paleo-backbarrier surface backstripped using the following: If Mo-BBo=0; BB1=BBar*T1 If Mo-BBo>3; BB1=BBo If Mo-BBo<3; (T1-(Mo-BBo)*Mar)*BBar Mo: modern marsh level M1: marsh level at time T1 BBo: modern backbarrier sediment BBo: backbarrier sediment at T1 BBar: mean backbarrier sediment accretion rate (0.28 cm/yr) Mar: mean marsh accretion rate (0.12 cm/yr)

1 2T

• GPR horizon surfaces of inlet sequence shown (above; note: GPR Section B highlights base of inlet • Red horizon: top of inlet sequence (base of overlying spit platform) • Blue horizon: base of inlet sequence (coarse lag deposit underlain by fine backbarrier sediments)

Spit Sequence

Major Inlet / Channel Sequence

Very Coarse Sand / Gravel

V.F./ Fine Sand

Spit Platform

Top of Glaciomarine

Medium Sand

Silt / Clay

v: velocity of flow through tidal inlet Q: tidal inlet discharge

• Tidal Prism (TP) related to inlet cross sectional area as per Jarret Curve (left) • TP for three-inlet system calculated from combined x-c areas of inlets, assuming constant areas

Inlet Data Merrimack Parker Essex

m

Li

Jarrett, 1976

BOOTHROYD, J.C., FITZGERALD, D.M., 1989, SEPM Eastern Section Field Trip Guide, 2-4 June, 1989.

Min. X-C Area of Inlet (ft2) Below MSL 105

Tidal Prism

Equivalent Inlet X-C Area

Combined Modern Inlets (calculated) Paleo-Backbarrier (Modeled Surface ±0.5 m)

88 x 10 m

6700 m2

155 x 106 m3 ± 11 x 106 m3

13,100 m2 ± 1200 m2

Residual

67 x 106 m3

5300 m2

6

3

DONNELLY, J.P., 2006, Journal of Coastal Research, 22 (5), 10511061. FITZGERALD, D.M., ROSEN, P.S., VAN HETEREN, S., 1994, in DAVIS, R.A., Geology of Holocene Barrier Island Systems, Berlin, Germany: Springer-Verlag, p 305-394 HARTWELL, A.D., 1970, University of Massachusetts, Amherst, MA, Contribution 5-CRG. Contract Nonr N00014-67-A0230-0001 Geography Brach, Office of Naval Research, 166 pp. KEENE, H.W., 1971, Maritime Sediments, v (2), 64-68

0

0

JARRETT, J.T., 1976, U.S. Army Corps of Engineers, GITI Report 3, 32 pp.

2 100

4 6

1300

8

2 m

200

300

10 12 14

D

50 m Primary inlet structure mapped under Plum Island: X-C Area = 1300 m2 (Equivalent TP: 18 x 106 m3)

REFERENCES

BARNHARDT, W.A., ANDREWS, B.D., ACKERMAN, S.D., BALDWIN, W.E., HEIN, C.J., 2009, USGS Open File Report 2007-1373

• Backstripped TPs normalized to modern TP using modeled modern backbarrier surface

e

fid

n o C

e c n

it

• Backbarrier infilling & subsequent tidal prism reduction are direct causes of inlet closure & primary contibutors to barrier island development • Geomorphic backstripping can provide insight into the analysis of paleo-environments

• TP at time of active paleo-Parker Inlet (3500 BP) modeled via backstripping of backbarrier sediment

Paleo-Parker

% 5 9

• Sediment influx to the backbarrier of Plum Island has driven bay sedimentation, formation of tidal flats & marshes, & a vast reduction in the bay tidal prism

0

Regression Eq: A=5.37 x 10-6 P1.07

Jarrett Data No Jetties One Jetty

CONCLUSIONS

A v dt = Q dt

0

Core Log Key

GPR Key

1 2T

T: time of 1 tidal cycle A: cross-sectional area of tidal inlet

• Core stratigraphy sub-divided by facies • Cores georeferenced to mean low water

Base of Inlet

TIDAL PRISM MODELING

Backbarrier Base Model:

0 -5 -10

400

High resolution GPR, nearshore shallow seismic (Barnhardt et al, 2009) and onshore coring provided for identification of lowstand / transgressive channel of paleo-Parker River; Base of channel located ~10 m below modern MLW. Complex inlet & spit system overlies paleo-channel

-15 m

0 -5 -10

Backbar rier Sedimen ts

12

3m+ 2 km

250

200

10

N

INLET FILL

100

Backbarrier Surface Model:

N 0

5m

ENCE

0

BACKBARRIER BACKSTRIPPING Merrimack River

200

Spit Platform

SPIT SEQU

400

Depth (nanoseconds)

• Paleo-Parker Inlet closes completely • Spit rapidly progrades south, overtopping inlet fill sequences

3

8

250

2

Ground penetrating radar and core locations. Maroon box indicates location of region shown on right.

• Island elongates by spit migration (GPR Section A) • Paleo-Parker Inlet occupies Parker River channel & begins southerly migration; active around BP 3505 +/- 145 cal

• Paleo-Parker Inlet deflected to north, truncating southerly prograding spit and platform (GPR Section B) • Inlet narrows, deepens; backbarrier starts filling

5m

50

2

0

STAGE III: Ebb Tidal Delta Breaching

Ebb tidal delta breach Parker River captures southern stream

Long Shore Current

STAGE II: Migration of Paleo-Parker Inlet

A

Elevation wrt MLW (m)

Sand shoals

Paleo-Parker Inlet ebb tidal delta

7

200

14

Radiocarbon Age (kyr B.P.)

STAGE I: Migration of Sand Shoals

• 12,000-3500 BP, regressive & lowstand deposits reworked onshore during transgression • Parker River maintains course offshore of present mouth; carves channel into highstand sediments; channel buried 12 m below modern Plum Island (GPR Section C) • Transgressive sands pinned to glacial deposits

6

Total Prism (Spring or Diurnal) ft3

STAGE II

Present Day Plum Island

150

5

Elevation wrt MLW (m)

STAGE I

4

1

Ground Penetrating Radar (GPR) profiles taken NW to SE along the section of Plum Island highlighted lower left box.

-4

-20

100

Elevation wrt MLW (m)

• Rowley River: Watershed Area = 36 km2 Annual Discharge = N/A (tidal) • Ipswich River: Watershed Area = 402 km2 Annual Discharge = 0.056 km3

3

8

0 1 km

50

2

M

12

10

EVOLUTION OF PLUM ISLAND Long Shore Current

I

-40

Cape Ann

Rivers of the Plum Island Backbarrier:

• Merrimack River: Watershed Area = 12,885 km2 Annual Discharge = 6.24 km3 • Parker River: Watershed Area = 167 km2 Annual Discharge = 0.033 km3

P

I

Depth Below MSL (m)

Coastal Setting: • mixed-energy, tide dominated • tidal range: 2.7 m

P P P H P P

L

1

GPR Horizon Model:

0

0

Approximate Depth (meters)

• Influenced by northeast winter storms

P Portland

0

Depth (nanoseconds)

Ipswich River

Ledge

-20

Rowley River

• Dominant long shore sediment transport to the south

J Jeffreys

I Isles of Shoals

Wood

0

Plum

P Island

Ice-contact delta

Shell

2 km

L Lynn

Marsh Merrimack M paleodelta

Saltwater peat

0

X

H Hampton

Freshwater peat

Plum Island

Parker River

N

Explanation

20

• Island within the longest continuous barrier chain in the Gulf of Maine

0

Laurentide Ice Sheet

Merrimack River

DATA COLLECTION AND RESULTS Depth (nanoseconds)

Great Boar’s Head

44

44 Woods Hole Oceanographic Institution, Woods Hole, MA 02543; Woods Hole Oceanographic Institution, Woods Hole, MA 02543; University University of of Massachusetts Massachusetts -- Boston, Boston, Boston, Boston, MA MA 02125 02125

Depth (nanoseconds)

• Plum Island located in the Merrimack Embayment, region of the western Gulf of Maine between Cape Ann (MA) and Great Boar’s Head (NH)

33

33

Approximate Depth (meters)

STUDY AREA

22

Approximate Depth (meters)

US US Geological Geological Survey, Survey, Reston, Reston, VA VA 20192; 20192;

22

Approximate Depth (meters)

Boston Boston University, University, Boston, Boston, MA MA 02215; 02215;

11

11

LYON, C.J., HARRISON, W., 1960, Science, 132 (3422), 295-296 McCORMICK, L.C., 1968, Field Trip Guidebook: Coastal Environments of NE Mass and N.H., 368-390 McINTIRE, W.G., MORGAN, J.P., 1964, in: Morgan, J.p., ed., LSU Studies, Coastal Studies Series, no. 8, Baton Rouge: LSU Press OLDALE, R.N., COLMAN, S.M., JONES, G.A., 1993, Quaternary Research, 40, 38-45 REDFIELD, A.C., 1967, Science, 157 (3789), 687-692 RHODES, E.G., 1973, U.S. Army Corps of Engineers, Coastal Engineering Research Technical Memorandum., no.40, 75 pp. SOM, R.M, 1990, M.S. Thesis, Boston University


Plum Island AGU 2009 Poster  

Poster from AGU 2009 on Plum Island formation and backbarrier infilling.

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