Guidebook to geologic field studies in Rhode Island and adjacent areas: The 73rd annual meeting of the New England Intercollegiate Geological Conference, October 16-18, 1981: Trip B-

Boothroyd, Jon C.

Friedrich, Nancy

McGinn, Stephen R.

English

UNH Scholars' Repository

University of New Hampshire University of New Hampshire Scholars' Repository NEIGC Trips New England Intercollegiate Geological Excursion Collection 1-1-1981 Sedimentation in Microtidal Coastal Lagoons, Southern Rhode Island Friedrich, Nancy McGinn, Stephen R. Boothroyd, Jon C. Follow this and additional works at: https://scholars.unh.edu/neigc_trips Recommended Citation Friedrich, Nancy; McGinn, Stephen R.; and Boothroyd, Jon C., "Sedimentation in Microtidal Coastal Lagoons, Southern Rhode Island" (1981). NEIGC Trips. 300. https://scholars.unh.edu/neigc_trips/300 This Text is brought to you for free and open access by the New England Intercollegiate Geological Excursion Collection at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in NEIGC Trips by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact nicole.hentz@unh.edu. 211 Trip B-9SEDIMENTATION IN MICROTIDAL COASTAL LAGOONS,SOUTHERN RHODE ISLAND Nancy Friedrich1 , Stephen R. McGinn1 , and Jon C. Boothroyd1INTRODUCTIONThe Charlestown barrier spit-lagoon complex is centrally located on the south­ern Rhode Island coast (Fig. 1). The barrier spit is 6 km long E-W, varies in width from 200 to 400 meters, and serves to separate the back-barrier lagoon from Block Island Sound to the south. This coastline is classified as a mixed energy, wave-dominated coast after Hayes (1980) (Fig. 2). Local relative sea-level rise is proceeding at a rate of 30 cm per 100 years (Hicks, 1974).The barrier spit includes a narrow beach, a low dune ridge, vegetated back- barrier flats, and a stabilized inlet (Fig. 3). Subenvironments within the back- barrier lagoon (Fig. 4) include washover lobes to the west of the inlet, flood- tidal delta deposits north of the inlet, a low-energy lagoonal basin, and ero- sional terraces along the near margins of the lagoon.STOP 1. Charlestown Breachway and Flood-Tidal DeltaTwo stone jetties have been used to stabilize the Charlestown Breachway. Con­struction was begun in 1952 and completed in 1954 (Lee, 1980). The breachway is oriented N-S, is 33 meters wide, and 1.6 meters deep. Spring tide range (16 Aug­ust 1979) within the breach is 80 cm, the maximum surface flow velocity was170 cm sec-l. Flow through the breach is flood dominant. The inlet throat widens at the termination of the jetties and a small flood-tidal delta is pre­sent in the main channel.The main channel bifurcates around Wards Island with the greatest volume of water proceeding north over the west lobe of the flood-tidal delta (Fig. 5).Four vibracores were taken along a transect through this area (Fig. 4). Threecores were taken from the east lobe and one in the lagoon to the north. Across-section constructed from core logs (Fig. 6) shows glaciofluvial depositsoverlain by fresh-water wetland peat succeeded by a marine lagoon sequence. The lagoon sequence begins with erosional terrace/beach deposits followed by low-energy lagoon organic silt. Distribution of these deposits is controlled by theunderlying Pleistocene topography and they are not always present in all cores.Flood-tidal sands are deposited over the finer grained basin sediments.A sedimentation rate of 6.9 + 1.4 cm yr 1 has been established for the flood- tidal area through the use of Pb-210 dating (Fig. 7). See Figure 4 for sampling location.From 1951-1980 the flood-tidal delta grew by 141683 (Fig. 8). Sixty-one per­cent (87091 m3) nf this accretion occurred between 1951 and 1963, twenty-eight percent (39500 nr) occurred between 1963 and 1972, while only eleven percentdepartment of Geology, University of Rhode Island, Kingston, RI 02881MASSACHUSETTS212COdX psCO •r4<f\ 1 S 0)CO o I JH£ w M cO•IS So eCO ocd o cO ou CO 4-J 60PQ CD rH cOPQ CDdrH4J CDo CO rH 4S •4-J CO cO 4-J rHCO W d 00cu •H MH O nr-H 1 4-J O t-H5-« 1CO PQ d CO CDW o ps PSc j o •H#> rH CO d1 cO M-4 cO4-J rQ 00PQ rH MH CM<d O >*>d 60 ps• CD U oCO rH X CD4J CO o a PS•r4 d X CD CDa •H 1 MCO 4-J 4J £ cO1 CO o 4-J*4 d <D rHCD o•H o CD X*4 T"H 1 4S 4-J>H MH H uCO oX M-l PSO •u T—H CD 60a <D cd r—4 PSX ps •H •r4o O c MHcO X cO O o^2 U od 4J CJ CX rHCO COCO ps NJ <Dd w •H W 3C cO 1 c rcO 1 g •HrHcO W 1 CJ rOu OT“ 4 #* g CD0) H Xd 0) 4-J ocs 0) rHrH ps 60 MHCO CO d o COd X •H•H o p4 CD CO4J PQ 4J •r41 <D •Hd 60 H CO OO d rH 4JO cd •r4 #\ orH CM XMH dC exPXd I CD o COC CD 4J • r!O Q u CO rCPX c* o 1H4-J 1CD o CM •X cO o O60 CD r\ u•rH PQ +\ r-H oa r—<•H c j CD PX PXg a oo c 4-J CD0) 4J cO CO XCO X 4-JH CDrH CJ 1 MH• V4 PS i—H OCM CO • HX cO r\ (X• c j S d O60 PS 4J•H 1 4-J cOIX CO r H CDPQ CO CO XCJ W w 4-J214600OH I0500CRD COPPER RIVER DELTA,AKBF BAY OF FUNDYBB BRISTOL BAYGB GERMAN BIGHTNWF NW FLORIDASWF SW FLORIDAPI PLUM ISLAND,MAOB OUTER BANKS, NCSK S ICELANDCB CHARLESTOWN BEACH, Rlkr V V400V300q CRDLU100W7mmk h m k p•vV/V.'I... •; '.nICEW AVE-DOMINATED40 80 120 160 200 240MEAN WAVE HEIGHT cmFig. 3. A plot of wave height versus tidal range. The Rhode Island coast­line is indicated by the filled circle and is labelled CB. From Hayes (1979) Charlestown wave data from Swanson (written communication, 1980).215*ocdcn03 cococo+->05CJOcu4->-MCL)03OOCD • C (O• r- C+■> O03 *r—■a 4->05 CJ CJOI05 05 CD-o• r- I +->I“O  0 5O  CD0i—  “OH - c051rv"O  -C-4-> CO05#> 4-)4-> 3  •i- OCLCO i—034->d ) CDCD CJr- 05S- C- 0 5o“O05S -"Oc:05CDOCJ£4->03-OIICDOO03C-+->OCDCOc03£-4-J4-* CDO  C DcomCD CD O  S- 03 03 C- S-CO CD 4-> 4->>C  .3  03 Co oO )  COo o+-> o  CD CDO) O) I03O  C D - P—  .c :  l u05034->CDCOc.CDJOc•  •coCO COCD 03 4-> JD>cCDCO05c03co4->COOC LCD"O“OCDCJCDCOC03Coo050305"OOC LOO4-> r-HC\JCD I5 - jQ  O  CLCJ CD4->03 C05 ICJCD4->03 CJzn "o cj c:ijQ03CDJDOC-CD> ao  ccoCD■aCO 003 S.IO  =CO05 CD4->4->CD_QCL" C 034-> r-C J CD t  "O  0CHANNEL SYSTEM GREEN HILL BRIDGEDISCHARGE Ft5216aoondo00 COEoCMoFig. 5. Schematic diagram indicating percentage of total discharge that each channel carries on the flood and ebb.NINIGRET FLOOD-TIDAL DELTA217a.CDCCOoomoo*i/icUJKUJ2oorOOOCJOOo>>JDcoCOI/)CDNCOCfOCDCOco4->03OOOCOCDC DCDCDLOCoC L4->CDCD4-*OCDCOcf04->034->"cd-ard4->i-aooCDCJ)width of log, narrow for silt to wide for gravel; internal stratification, shells, and roots also shown. Ages were obtained from C-14 dating of shells, peat and wood.218NINIGRET TIDAL D E LTA 1 S= 6.9^1.4 cm vr~1  ----GREEN HILL TID AL D E L TA3=0.92£0.11 cm yr-I PT JUDITH ------EAST POND FLATS=0.37±0.02 cm yr“ 1SEDIMENTATION RATE:210Pb RADIOMETRIC DATINGO.l0.08J QCLO0.060.040.020.0I0.008PLATFORMWASHOVERNINIGRET0.0060.0040.0020.001TOP OF CORE DEPTH cmFig. 7. Sediment accumulation rates obtained by Pb-210 dating of organic material in cores. Sampling location for Ninigret Pond is shown in Figure 3(L2p ).219WEST LOBE6 9 7 9 6  m 32 4 0 7  m 3 a'13  - HEAST LOBE7 1 8 8 7  m 3  3 4 2 3  m 3 a'10Fig. 8. Growth of flood-tidal delta lobes, Ninigret Pond. Areal change through time was determined by measuring intertidal and subtidal flats on sequential vertical aerial photographs (1951, 1963, 1972, 1975, 1980). A sediment thickness of 1.0 and 1.3 m, based on stratigraphy in vibracores, was used to compute sediment volumes. Numbers refer to times of accretion as follows: 1) 1975-1980, 2) 1972-1975, 3) 1972-1980 (composite), 4a) 1951-1963,4b) 1963-1972, 5) 1951-1963, and 6) 1963-1972. See text for volumes. From Boothroyd et al (1981).220(15093 m°) occurred between 1972 and 1980. Examination of aerial photographs show negligible areal changes in the flood-tidal delta from 1938 to 1951 so that the probable cause of flood-tidal delta growth is the opening of the permanent breachway in 1952-1954.STOP 2. Profile CHA-EZBeach profiles, using the Emery method, have been taken at this locality every 1-10 days since 1 October 1977 (Fig. 9). A computer is used to plot the profile and to calculate the area under the curve. Profile volumes are reported as cubic meters per linear meter of beach. Two contrasting profiles, illustrating a mature beach profile and a post-storm profile, are shown in Figures 10a and 10b.Change in the total profile volume (Fig. 9) is a combination of berm erosion and recovery and foredune ridge erosion. Small net change in the total volume indi­dates that some of the eroded dune material is incorporated into the berm during recovery. There is a strong correlation between berm volume changes and storm/ fair weather cycles. A minor seasonal fluctuation is also observed (Boothroyd and O'Brien, 1980).REFERENCESBOOTHROYD, J. C., FRIEDRICH, N. E., MCGINN, S. R., SCHMIDT, C. A., ROSENBERG, M. J., PETERS, C. R., O'BRIEN, J. H., AND DUNNE, L. A., 1981, The geology of selected microtidal coastal lagoons, Rhode Island, I. Data summary and manage­ment questions: Tech. Report No. 2-SRG, Vol. 1 and 2, Sed. Research Group, Dept, of Geology, Univ. Rhode Island.BOOTHROYD, J. C., AND O'BRIEN, J. H., 1980, Erosion and recovery of a microtidal beach; Charlestown Beach, Rhode Island (abs): Geol. Soc. America Abs. with Programs, Northeast Section, v. 12, n. 2, p. 25.HAYES, M. 0., 1979, Barrier island morphology as a function of tidal and wave regime, vn Leatherman, S. P., ed., Barrier islands from the Gulf of St. Law­rence to the Gulf of Mexico: New York, Academic Press, p. 1-28.HICKS, S. D., 1974, Trends and variability of yearly mean sea-level 1893-1972: National Oceanic and Atmospheric Administration, Tech. Memorandum NOS 13 (C0M-74-11012), 14 p.LEE, V., 1980, An elusive compromise: Rhode Island coastal ponds and their peo­ple: Coastal Resources Center, Univ. Rhode Island, Marine Tech. Report 73,82 p.FURTHER READINGBOOTHROYD, J. C., 1978, Mesotidal inlets and estuaries, rn Davis, R. A., ed., Coastal Sedimentary Environments: New York, Springer-Verlag, p. 287-360. DILLON, W. P., 1970, Submergence effects on a Rhode Island barrier and lagoonand inferences on migration of barriers: Jour, of Geology, v. 78, p. 94-106. HAYES, M. 0., AND KANA, T. W., 1976, Terrigenous clastic depositional environ­ments: Tech. Report No. 11-CRD, Coastal Research Division, Dept, of Geology,Univ. South Carolina, 302 p.LEATHERMAN, S. P., 1979, Barrier islands from the Gulf of St. Lawrence to theGulf of Mexico: New York, Academic Press, 325 p.CHARLESTOWN BEAC221LUOLULLOccQ.NLUJcoIoCDC CDCD4-> CO CD *r- CDt/)CD +-> • CDO  TD  •r—  CD X2 CD3  Q-O  (/)=3CO CD CD fO C - P  CD O  t  •i—  to  COrO Ic  (O-o o •CDC  CD roOCO fC  C•iCD •CO34-> OCDCD 4-> 4->CD+-> S- S - O  O  +■>CDCDCOCoCDS- Oid 4->OCO CDCOCO S- CD CO r—  COCL CD CO 3  S-C  O  I-M O  O  COCOCOCD CDE  </>3  3CDCD «E  +* * CDO  O  CO UCD CD OCDCro«- 3O  CD -o SZO> coCOCDCOcM- O  O  -r-OCD ro CD COO COOOcCO roCL OQ- CO 4-> COCD CD • C  >>•r- -M 4-> “O  t -CO OC  Oro O4-> C  -C OO V r -•r- 4->CD rOOCDCo  •CD O E3  CD 3O  S - -CCDCDCO4-> CD CSZ roCDCOcOOcrO4->COCDCDO>CD4->roCD5  3CD4->COCDC3COICoQ. OOroS- O  CDQ- CLCDCCD CD 4-> CD 4-> CL CDCOCDrOMCDL  ro  O3  +■>I3COCOCDO OroCDOrOCD-QO  “O  •r—  rO+■> CD O  CDO  ^  U  CD TJ+->O<+- 4-> 4->OC L  S -4->CDCD O• (D  ro O) E  -OCoCOCDCD lO * CD C  O4->OOCD>r -  roL . -MO  ro“DCDS- CD O  >C  roCOCDC  * oO  Cro•cui awmoA222OCO-T“o intoU 0*1oL o  o>oo 00-I—oTo<r>r t lU  3 A 0 8 VToCMSy313WToooUJo  <o c/o<Dz>ooinooru.cn  cco  uj. roo- oroooCslo ■ oooro<£>TOy>W 0* Ioroo05oo00ooUJo  ^CO«<QO  2= . Oo a :in ll-ooorUJ_  UJ°  roooroooCMOoToToToCOin *«- ro cmM 1U  3 A 0 8 V  S U 3 1 3 WooFig. 10. Computer plotted profiles for the CHA-EZ location. A) Mature profile - exhibits a large berm, steeply sloping beach face, gently landward dipping berm top, and a poorly-to-well-developed seaward dipping face landward of the berm top. B) Post-storm profile - a flat beach with a pronounced intertidal to sub­tidal bulge of sand. The swash bar is quickly returned to rebuild the berm and recovery is rapid.42COcO o44 s 4Jo Od 42 42a CO ad CO4-J 4-J CDcO o 422 o 4->o4-J d MH0) co OcOW l 4-J421 CO 60•iHS Uw "da CD#N o 42>> P^ 4-JCO£ 42 a42 4-J •Ho •HcO dCD d CD •*H CD rH 1PQ CO 004-J42 a CD r-H4-J •H 42•H o a>T3 p^ a dd CO d*“ > 1 o •“ >4-> CD 00d p^ <D CM•H rHO •«H dPH *d r—4 od cO1 O O dP h CDPQ <4H 4 *U o COCD 4-J• 4-J CO42 4-J 4 * *\CO o a 42u p * o 4-JcO *d *HS 1 oCD d42 PH 42CO H 60cO #\ du g •Ho CD • 44o rH 4-J Oo cO CO Od CO rH rHCO d <4Hu CDT3 a> rH da •d CO c rcO T3 •Hi •H rH"d 4J 42d Hi Oo <DpL, 4-J S"d (2 O42 d •H rH4-J cO•H rH d CO"d CO cOd M CO#\ •H4-J m4J CO Od CD Ou 4-J•H U o OO O 4-J 42P-4 i CO PuuCD£oo60•HPh42O03CDPQa>4JCO4-JcoI ca•Hm  42Hr>co0 <f4-»CO O ho1 4JcoCO224Fig. 12. Lower Point Judith Pond and Succotash Marsh, simplified deposi- tional-environmental map. Numbers refer to stop locations. Geologic units: Af - artificial fill, Bs - barrier spit, Ms - marsh, U - glacial upland,Fi - intertidal flats, Fs subtidal flats.ItineraryThe field trip will leave from the Keaney parking lot beside the athletic fields, University of Rhode Island. It involves walking in water, wet sand and mud. A small boat will be used to gain access to two stops. Wear hip waders, sneakers, or tennis shoes. Do not wear field or hiking boots.Pt. to Pt. Total3.8Route and Stops0 0 Leave Keaney parking lot, turn right (west) onRI 138.0.6 0.6 Intersection of RI 110 at lights. Turn left (south)on RI 110. This route is also called MinisterialRoad.Tuckertown Four Corners, intersection of Wordens Pond Road on the right (west), and Tuckertown Road on the left (east), located on ice-contact deposits just north of the Charlestown end moraine. Proceed south through the intersection and up onto the moraine.0.7 5.1 Backside (ice-contact slope) of Charlestown moraine1.3 6.4 Intersection with Old Post Road, and beginning ofproximal outwash plain. Proceed south to US 1.0.2 6.6 US 1, go west past exits to Moonstone and GreenHill beaches. Charlestown moraine on the right.1.2 7.8 Charlestown Beach exit; Exit from left lane ontoUS 1, north.0.3 8.1 Exit right at Charlestown Beach breachway sign.Proceed 100 yds. to stop sign (intersection with US 1A); continue straight through stop sign.Pass over proximal outwash plain (former potato farm).0.5 8.6 Turn left at stop sign onto Schoolhouse Rd; followBeach/Breachway signs.0.1 8.7 Turn right onto Charlestown Beach Rd. Proceedsouth on the outwash plain; across a small till upland, and down to the lagoon.Distancees1.3 10.0 Green Hill Pond bridge; Charlestown Pond with dredged channel to the right; Green Hill Pond226to the left (small island with house is a till up­land). Beyond the pond is Green Hill, a drumlin.Bear left off bridge onto back barrier. Proceed 200 yds.0.2 10.2 Bear right to travel west along the back barrier.Example of a developed barrier spit, most houses built since 1970.0.5 10.7 Location of CHA-EZ profile.0.1 10.8 Two houses formerly on left lost in 1977-78; areaof active overwash.0.1 10.9 Charlestown Breachway (State Camping Area), gravelparking lot.STOP 1 . This will be a long stop to view the breachway jetties constructed in 1952, and then walk north (lagoonward on flood-tidal delta deposits 200 m north is a straight, manmade channel dredged in 1962 to Green Hill Pond. Embark in boats for a short cruise to the tidal-delta flats. Note the channel point bars, channel-margin flats, flood ramp, and high marsh.Leave breachway parking lot, heading east along back barrier.0.2 11.1 Location of CHA-EZ beach profile.STOP 2. The beach profile has been run at 1-10 day intervals since Oct, 1977. Severe erosion occurred during 1977-78; no dune recession has been recorded since Feb. 1978 (as of early Aug. 1981). The houses are on piling with floor joints set at the 1938 hurricane storm-surge still water level.0.7 11.8 Return east along back barrier to the Green HillPond bridge. Proceed north.1.3 13.1 Intersection Charlestown Beach Rd. and SchoolhouseRd. Turn left at Stop sign onto Schoolhouse Rd.Proceed 200 yds.; turn right, heading north.0.5 13.6 Stop sign; intersection with US 1A. Continuestrai ght.0.1 13.7 Bear right onto US 1 (north). Drive east and northalong the front slope of the Charlestown moraine, past exits for Moonstone and Matunuck beaches.227Proceed up onto the moraine with a view of Potter Pond on the right.Exit right off US 1 north at the Jerusalem, Snug Harbor, East Matunuck State Beach sign. Proceed south on Succotash Rd.Bear right at fork.Potter Pond bridge: Succotash Marsh on left;Potter Pond right; houses built on glacial upland and areas of dredge spoil.Bear right into East Matunuck State Beach parking l o t .STOP 3. The State Beach pavilion sits astride the location of the 1897 tidal inlet. We will walk west to the gravel washover fans on the spit fronting Potter Pond; then east onto Succotash Marsh, a marsh-covered flood tidal delta. The areas covered with shrubs are glacial "islands" poking through the tidal-delta deposits.Return north along Succotash Rd; over Potter Pond bridge to US 1 .Turn right onto US 1 (north).Saugatucket River passes under the road to Pt. Judith Pond (on the right).Exit right off US 1 at sign for Point Judith, Scarborough, and Galilee. Proceed up off-ramp; turn right onto Woodruff Ave; follow signs for Point Judith. Bear right at lights onto RI 108 (south).Drive south on RI 108 several miles, through to intersection with traffic lights. You are travers­ing along Pt. Judith end moraine.Fisherman's Memorial State Park on right; the site of coastal defense gun batteries guarding the east entrance to Narragansett Bay during WW II.Exit right off 108, onto the "Escape Route", head­ing west (road work begun in 1954 and finished in 1956).Sand Hill Cove Marsh on left East Pond, part of Point Judith Pond on right.Turn left (south) at T-intersection onto Great Island Rd. Entering Village of Galilee.2280.4 33.3 Turn right into parking lot next to breachway jetty0.3 34.10.1 34.20.2 34.4STOP 4 . Pt. Judith breachway. An inlet formed naturally at this site in 1901 and was stabilized with jetties beginning in 1909. Tidal-current discharge is 6-8 times that of Ninigret Pond and periodic maintenance dredging is needed to remove the flood ramp and ebb spits, and maintain pro­ject depth over the developing bedforms.Turn right (east) out of parking lot.0.1 33.4 Turn left at sign for Providence, and Great Island.0.4 33.8 Turn right at Stop sign onto Great Island Rd (north)Proceed north to Great Island.Great Island Bridge.Bear left at blinking light onto Conch Rd.Turn left onto Island Rd. (also sign for Mollusk Dri ve).0.1 34.5 Bear right down private drive to small, sandyparking lot. STOP: private property; leave vehicl and walk to house on point; request permission to cross property.STOP 5. There is a good view at low tide from this island of glacial material. Visible are the mid­pond intertidal flat and bar systems. We will visit the largest flat, by boat, embarking from the boat launching area near the parking lot. Note the variety of fauna on the tidal flat.END OF TRIP

Sedimentation in Microtidal Coastal Lagoons, Southern Rhode Island

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Sedimentation in Microtidal Coastal Lagoons, Southern Rhode Island

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