KECK GEOLOGY CONSORTIUM

PROCEEDINGS OF THE TWENTY-SECOND ANNUAL KECK RESEARCH SYMPOSIUM IN GEOLOGY

April 2009 Franklin & Marshall College, Lancaster PA.

Dr. Andrew P. de Wet, Editor Keck Geology Consortium Director Franklin & Marshall College

Dr. Stan Mertzman Symposium Convenor Franklin & Marshall College

Kelly Erb Keck Consortium Administrative Assistant

Diane Kadyk Academic Department Coordinator Department of Earth & Environment Franklin & Marshall College

Keck Geology Consortium Franklin & Marshall College PO Box 3003, Lancaster PA 17604-3003 717 291-4132 keckgeology.org

ISSN # 1528-7491

The Consortium Colleges National Science Foundation KECK GEOLOGY CONSORTIUM PROCEEDINGS OF THE TWENTY-SECOND ANNUAL KECK RESEARCH SYMPOSIUM IN GEOLOGY ISSN# 1528-7491

April 2009

Andrew P. de Wet Keck Geology Consortium Stan Mertzman Editor & Keck Director Franklin & Marshall College Symposium Convenor Franklin & Marshall College PO Box 3003, Lanc. Pa, 17604 Franklin & Marshall C.

Keck Geology Consortium Member Institutions: Amherst College, Beloit College, Carleton College, Colgate University, The College of Wooster, The Colorado College Franklin & Marshall College, Macalester College, Mt Holyoke College, Oberlin College, Pomona College, Smith College, Trinity University Union College, Washington & Lee University, Wesleyan University, Whitman College, Williams College

2008-2009 PROJECTS

THE BLACK LAKE SHEAR ZONE: A POSSIBLE TERRANE BOUNDARY IN THE ADIRONDACK LOWLANDS (GRENVILLE PROVINCE, NEW YORK) Faculty: WILLIAM H. PECK, BRUCE W. SELLECK and MARTIN S. WONG: Colgate University Students: JOE CATALANO: Union College; ISIS FUKAI: Oberlin College; STEVEN HOCHMAN: Pomona College; JOSHUA T. MAURER: Mt Union College; ROBERT NOWAK: The College of Wooster; SEAN REGAN: St. Lawrence University; ASHLEY RUSSELL: University of North Dakota; ANDREW G. STOCKER: Claremont McKenna College; CELINA N. WILL: Mount Holyoke College

PALEOECOLOGY & PALEOENVIRONMENT OF EARLY TERTIARY ALASKAN FORESTS, MATANUSKA VALLEY, AL. Faculty: DAVID SUNDERLIN: Lafayette College, CHRISTOPHER J. WILLIAMS: Franklin & Marshall College Students: GARRISON LOOPE: Oberlin College; DOUGLAS MERKERT: Union College; JOHN LINDEN NEFF: Amherst College; NANCY PARKER: Lafayette College; KYLE TROSTLE: Franklin & Marshall College; BEVERLY WALKER: Colgate University

SEAFLOOR VOLCANIC AND HYDROTHERMAL PROCESSES PRESERVED IN THE ABITIBI GREENSTONE BELT OF ONTARIO AND QUEBEC, CANADA Faculty: LISA A. GILBERT, Williams College and Williams-Mystic and NEIL R. BANERJEE, U. of Western Ontario Students: LAUREN D. ANDERSON: Lehigh University; STEFANIE GUGOLZ: Beloit College; HENRY E. KERNAN: Williams College; ADRIENNE LOVE: Trinity University; KAREN TEKVERK: Haverford College

INTERDISCIPLINARY STUDIES IN THE CRITICAL ZONE, BOULDER CREEK CATCHMENT, FRONT RANGE, CO Faculty: DAVID P. DETHIER: Williams College and MATTHIAS LEOPOLD: Technical University of Munich Students: EVEY GANNAWAY: The U. of the South; KENNETH NELSON: Macalester College; MIGUEL RODRIGUEZ: Colgate University

GEOARCHAEOLOGY OF THE PODERE FUNGHI, MUGELLO VALLEY ARCHAEOLOGICAL PROJECT, ITALY Faculty: ROB STERNBERG: Franklin & Marshall College and SARA BON-HARPER: Monticello Department of Archaeology Students: AVERY R. COTA: Minnesota State University Moorhead; JANE DIDALEUSKY: Smith College; ROWAN HILL: Colorado College; ANNA PENDLEY: Washington and Lee University; MAIJA SIPOLA: Carleton College; STACEY SOSENKO: Franklin and Marshall College

GEOLOGY OF THE HÖH SERH RANGE, MONGOLIAN ALTAI Faculty: NICHOLAS E. BADER and ROBERT J. CARSON: Whitman College; A. BAYASGALAN: Mongolian University of Science and Technology; KURT L. FRANKEL: Georgia Institute of Technology; KARL W. WEGMANN: North Carolina State University Students: ELIZABETH BROWN: Occidental College; GIA MATZINGER, ANDREA SEYMOUR, RYAN J. LEARY, KELLY DUNDON and CHELSEA C. DURFEY: Whitman College; BRITTANY GAUDETTE: Mount Holyoke College; KATHRYN LADIG: Gustavus Adolphus College; GREG MORTKA: Lehigh U.; JODI SPRAJCAR: The College of Wooster; KRISTIN E. SWEENEY: Carleton College.

BLOCK ISLAND, RI: A MICROCOSM FOR THE STUDY OF ANTHROPOGENIC & NATURAL ENVIRONMENTAL CHANGE Faculty: JOHAN C. VAREKAMP: Wesleyan University and ELLEN THOMAS: Yale University & Wesleyan University Students: ALANA BARTOLAI: Macalester College; EMMA KRAVET and CONOR VEENEMAN: Wesleyan University; RACHEL NEURATH: Smith College; JESSICA SCHEICK: Bryn Mawr College; DAVID JAKIM: SUNY.

Funding Provided by: Keck Geology Consortium Member Institutions and NSF (NSF-REU: 0648782) Keck Geology Consortium: Projects 2008-2009 Short Contributions – RHODE ISLAND

BLOCK ISLAND, RI: A MICROCOSM FOR THE STUDY OF ANTHROPOGENIC AND NATURAL ENVIRONMENTAL CHANGE Project Director: JOHAN C. VAREKAMP: Wesleyan University Project Faculty: ELLEN THOMAS: Yale University & Wesleyan University

RECONSTRUCTING THE PALEOENVIRONMENT OF THE GREAT SALT POND: A STABLE ISOTOPE ANALYSIS OF FORAMINIFERA ELPHIDIUM EXCAVATUM OVER THE LAST 1750 YEARS ALANA BARTOLAI: Macalester College Research Advisor: Kelly MacGregor

FORAMINIFERA AS PROXIES FOR SALT MARSH ESTABLISHMENT AND EVOLUTION ON BLOCK ISLAND, RHODE ISLAND EMMA KRAVET: Wesleyan University Research Advisors: Ellen Thomas and Johan Varekamp

ATMOSPHERIC MERCURY DEPOSITION IN AN ISOLATED ENVIRONMENT: A 300-YEAR RECORD AT BLOCK ISLAND, RHODE ISLAND RACHEL NEURATH: Smith College Research Advisor: Robert Newton

USING CARBON AND NITROGEN ISOTOPES AND LOSS-ON-IGNITION TO RECONSTRUCT THE LAND USE HISTORY OF BLOCK ISLAND, RHODE ISLAND JESSICA SCHEICK: Bryn Mawr College Research Advisor: Donald Barber

A 3.5 KY SEDIMENTARY RECORD OF THE GREAT SALT POND ON BLOCK ISLAND, RI CONOR VEENEMAN: Wesleyan University Research Advisor: Johan Varekamp

Funding provided by: Keck Geology Consortium Member Institutions and NSF (NSF-REU: 0648782)

Keck Geology Consortium Franklin & Marshall College PO Box 3003, Lancaster Pa, 17603 Keckgeology.org 22nd Annual Keck Symposium: 2009

FORAMINIFERA AS PROXIES FOR SALT MARSH ESTABLISHMENT AND EVOLUTION ON BLOCK ISLAND, RHODE ISLAND

EMMA KRAVET: Wesleyan University Research Advisors: Ellen Thomas and Johan Varekamp

ABSTRACT spike grass (Distichlis spicata) and marsh elder (Iva frutescens). Less densely vegetated marsh areas Salt marshes bordering Great Salt Pond (Block contain Salicornia species, and pannes in the high Island) were investigated using surface samples marsh are bare or covered with cyanobacterial mats. and samples from three cores, in order to establish Present and past salt marsh environments were the period that the marshes have been in existence, studied using sedimentary parameters (grain size, study their development over time, and attempt to organic matter) as well as information on foramin- reconstruct rates of relative sea level rise. The data ifera, eukaryotic unicellular organisms living in collected include coarse fraction weight percent of marine environments. sediment, organic content (Loss On Ignition), Hg concentration, and marsh foraminiferal assemblage composition. Age models for the cores were con- structed using the Hg pollution records and correla- tion to a core taken in Fresh Pond (Block Island), and dated using radioisotope methods. Our data indicate that the present marshes are a relatively recent part of Block Island’s landscape, and became established about 1935-1940AD, i.e., probably after the major hurricane of 1938. The high marsh environment at our core locations did not show major changes in elevation over that time period, indicating that relative sea level rise occurred at a rate similar to that of marsh accretion in the high marsh areas, about 2-4 mm/year, in agreement with commonly cites rates of modern sea level rise. The low marsh accreted at a much higher rate, especially over the last 2 decades, with increasing density of vegetation.

INTRODUCTION

Salt marshes along the northern edge of Great Salt Pond (Figure 1) include Andy’s Way Marsh (N: 41o12.046, W 071o34.468) and Block Island Salt Marsh (N41o12.189; W 071o34.787), with a vegeta- tion of smooth cordgrass (Spartina alterniflora) in Figure 1: Block Island and its salt marshes. A: Andy’s Way Marsh, mainly a low marsh area; B1: Block Island Salt Marsh East, the low marsh regions, salt hay (Spartina patens) in dominated by high marsh vegetation; B2: Block Island Salt the high marshes, and more diverse floras along the Marsh West, dominated by low marsh vegetation with narrow marsh edge, including black grass (Juncus gerardii), uplands. 287 22nd Annual Keck Symposium: 2009

Pond was dated using the radionuclides 210Pb and Foraminifera form shells, providing a fossil record, 137Cs (Krishnaswamy et al., 1971), and Hg concen-

constructed from CaCO3 or from agglutinated trations were measured in these same sediments. grains of sediment. Foraminifera in salt marshes are almost all agglutinated, whereas tidal flat forms are There are no local sources for Hg pollution on Block dominantly calcareous. The distribution of foramin- Island, and the Hg thus arrives by atmospheric ifera in intertidal settings is primarily controlled by transport and deposition (Varekamp et al., 2003). physico-chemical conditions related to exposure The Hg records in our core are very similar in shape time, i.e., the fraction of time that the salt marsh to these in the Fresh Pond core, where minor initia- surface is not covered by sea water (Scott et al., tion of Hg pollution started in the late 1800s, fol- 2001). The exposure time is controlled by the eleva- lowed by a steep increase in mercury levels at about tion of the local salt marsh surface above mean sea 1945 AD, followed by a poorly defined peak in Hg level and the local tidal range. Foraminifera occur in levels in the 1970s-1980s, prior to the introduction vertical assemblage zones in the intertidal range, in- of the Clean Air Act (Schuster, 2002). We thus used dicative of a specific level above mean sea level, and these three data points to construct an age model for therefore foraminiferal assemblages in core samples our three cores, to date the sediments in the three can be used to indicate the position of each sample cores, and derive linear accretion rates. The grain- with regard to mean sea level at the time that the densities of some samples with a range of LOI values foraminifera were living. If we then know the age of were determined using a Hydraulic Carver Labora- each sample, we can reconstruct the position of each tory Press, in which samples were compressed at sample with regards to modern mean sea level, and 10,000 psi. After compression, the sample pellets thus we can reconstruct the rate of sea level rise over were weighed and measured in order to calculate ap- the time of deposition of the studied samples (e.g. proximate grain-density. We used the correlation be- Varekamp and Thomas, 1998). tween the grain densities from these three samples and the LOI values to calculate grain-densities for METHODS all samples, and combined these values with data on water content to calculate bulk dry density values. Fieldwork was conducted in Block Island Salt Marsh The Mass Accumulation Rate (MAR) was then (BISM) and Andy’s Way Marsh in June and July calculated by multiplying the bulk dry densities and 2008. Cores and surface samples were taken, their linear accretion rates. The accumulation of organic locations recorded with a GPS unit, vegetation and matter was subsequently determined by multiplying environmental setting were recorded, and verti- the organic fraction as measured by LOI with the cal location within the tidal framework estimated. sediment accumulation rate. Similarly, we calculated Three cores and 20 surface samples were analyzed the mercury accumulation rates (in nanograms per for organic and carbonate content (Loss-On-Igni- cm2.year) and the benthic foraminiferal accumula- tion, LOI, at 550oC and 950oC), weight % >63 mm tion rate (BFAR, in number of foraminifera per cm2 (sand fraction), Hg content, assemblage composition .year) from the data. of foraminifera, and absolute abundance of foramin- ifera (number per gram bulk sediment). Specimens RESULTS and DISCUSSION of foraminifera were sorted and identified according to test morphologies. All data were entered in an Data used to reconstruct the paleo-environment at Excel spreadsheet and the relative abundance (per- the locations where our cores were taken are shown centages) of all species calculated. To estimate ages in Figure 2 (A-J). In cores from marginally marine of core samples, we correlated our core to a dated environments, a high marsh environment is repre- core from Fresh Pond on Block Island (N41o9.6564; sented in the core by peat-rich samples with high W 71o34.6028), a lake with a very small catchment values of LOI (>~60%), representing the remains of basin (Neurath, this volume). The core from Fresh dense vegetation, and relatively low values of sand

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Figure 2: Data from 3 cores from Block Island Salt marshes, Cores BISM8 and 11A from the high marsh in Block Island Salt marsh (East) and Core AW1-2 from the low marsh in Andy’s way Marsh. 2A: weight % coarse sediment (sand fraction); 2B: Loss-On-Igni- tion at 550oC (organic matter); 2C: concentration of mercury (Hg); 2D: relative abundance of the foraminiferal species Trocham- mina inflata; 2E Relative abundance of the marsh foraminiferal species Trochammina macrescens; 2F: Relative abundance of the marsh foraminiferal species Miliammina fusca; 2H: mass accumulation rate of bulk sediment; 2I: benthic foraminiferal accumula- tion rate; 2J: accumulation rate of Hg in nanograms per cm2 per year. 289 22nd Annual Keck Symposium: 2009

(wt. % >63 μm). More low marsh environments have age model and bulk dry densities) showed, as ex- lower LOI values and a higher sand content. Storm pected, relatively high values for the sandy intervals, events may be recognized in marsh cores because although the accretion rates are poorly constrained, of the presence of sand-rich layers. Our two cores and lower values for the peat sections of the core taken in the high marsh environment (BISM8, BIS- (Fig. 2H). The BFAR plot (Fig. 2I) for the two high M11A) have sand-rich layers without foraminifera marsh cores show a large peak in the late 1950s-ear- at the base, overlain by peat (Figs. 2A and 2B). The ly 1960s, suggesting that less sediment was accumu- base of the peat thus represents the establishment lating at this time (i.e., the marsh was growing more of the marsh over a sand flat or dune environment. slowly). The BFAR values for the low marsh core In the low marsh core (AW1-2) there is a gradual peak at the top of the core, at the highest LOI values increase in LOI-values up-core (i.e., with time), sug- for that core (Fig. 2B), suggesting that foraminifera gesting gradually increasing density of marsh veg- are more abundant in more densely vegetated areas etation (S. alterniflora) becoming established on a in the low marsh. The Hg accumulation rates in the sandy depositional environment. This gradual devel- high marsh cores (Fig. 2J), which are exposed to the opment was interrupted by the deposition of a very atmosphere for a large part of the time, are similar sand-rich layer in the late 1930s to 1940s. In the peat to estimated atmospheric total Hg deposition rates sections of all our cores, Hg levels are relatively high in this somewhat remote location (1-5 ng Hg/cm2yr, (>50 Hg ppb), indicating that the formation of the USGS, atmospheric deposition network). The Hg peat, i.e., the existence of the marshes, must postdate accumulation rates in the low marsh core (AW1-2) the late 1930s to 1940s (Figures 2A, 2B, 2C). are much higher, similar to those from Fresh Pond (Neurath, this volume), which suggests that sedi- In the two high marsh surface samples and cores, ment was focused by currents and wave action at the foraminiferal species Trochammina inflata and the AW site, in agreement with the observed high Trochammina macrescens (characteristic high to accretion rates. middle marsh species, e.g. Scott et al., 2001) are the dominant species, whereas Milliamina fusca (char- If sea level had risen faster than the sediment ac- acteristic for middle to low marsh settings; Scott cretion rate, the marsh would have drowned (i.e., et al., 2001) is common to dominant in the low we would have seen a transition to a low-marsh marsh surface samples and core (Figs. 2D, 2F, 2G). environment going up-core), and if sea level had The high abundance ofM. fusca in low marsh core risen slower than the sediment accretion rate the AW1-2 is never matched in the high marsh cores, marsh would have changed to an upland area. We suggesting that our core locations in the high marsh see neither of these: the sites where the high marsh have been located in a high marsh setting for the cores were taken remained in the high marsh en- full duration of peat formation (~1940s to 2008), vironment (a zone with a thickness of about 15 cm and the location of the low marsh core has been in a vertical extent in our marshes), so that the sediment low marsh environment for that same time. In high accretion rate must have kept up with the local rate marsh BISM8, there is little variability with respect of relative sea level rise. This accretion rate is about 3 to T. inflata abundance, whereas in BISM11A there mm per year, so relative sea level must have risen at is a large increase in the abundance of T. inflata to- about the same rate. This value is similar to mod- wards the top of the core (Fig. 2D). This species sur- ern rates of absolute sea level rise estimated from vives strong fluctuations in salinity such as occur in satellite observations (e.g. Fitzgerald et al., 2008), the non-vegetated pannes, and core BISM11A was suggesting that the subsidence or rebound of Block taken next to a panne. We thus argue that this varia- Island is only a small factor in the observed relative tion in species relative abundance reflects horizontal sea level rise values. variability within the high marsh environment. The low marsh core shows much higher accretion The mass accumulation rate (determined using our rates than the high marsh environments. The low

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marsh accretion rate is probably also larger than the Schuster, P., Krabbenhoft, D. P., Naftz, D. L., Cecil, local rate of relative sea level rise (e.g., Fitzgerald et D. L., Olson, M. L., Dewild, J. F., Susong, D. D., al., 2008), but depositional environments remain Green, J. R., and Abbott, M. L., 2002. Atmo- within the low marsh faunal zone (with a larger spheric Mercury Deposition During the Last vertical extent than in the high marsh, ~ 40-50 cm). 270 Years: A Glacial Ice Core Record of Natural This low marsh deposit represents a marsh ‘coloni- and Anthropogenic Sources. Environmental zation sequence’ as also suggested by the increasing Science and Technology, v. 36: p. 2302-2310. LOI values up-core. Scott, D.B., Medioli, F. S., and Schafer, C. T., 2001. CONCLUSIONS Monitoring in coastal environments using fora- minifera and thecamoebian indicators. Cam- • The salt marshes along Great Salt Pond bridge University Press, New York, 177 pp. on Block Island became established only in the late 1930s-early 1940s, probably after the great hurricane USGS, Atmospheric Hg deposition in New England, of 1938 (Burns, 2005), at which time a prominent home page: http://nh.water.usgs.gov/projects/ sand layer was deposited at the low marsh site. nawqa/hg_dep.htm

• In the low marsh environment, sediment Varekamp, J. C., and Thomas, E., 1998. Sea Level Rise has been accreting faster then the local rate of rela- and Climate Change over the Last 1000 Years. tive sea level rise, resulting in marsh build-up. EOS, v. 79: p. 69-75.

• In the high marsh environments sediment Varekamp, J. C, Kreulen, B., and Bucholtz ten Brink, accretion has kept pace with the local rate of rela- M. F., and Mecray, E., 2003. Mercury contami- tive sea level rise, which we estimate to be about 3 nation chronologies from Connecticut wetlands mm/year. and Long Island Sound Sediments. Environ- mental Geology, v. 43: p. 268-282 • The Block Island salt marshes do not show evidence of being outpaced by recent rates of rela- tive sea level rise, but our research documents their extreme vulnerability to major storm events such as the hurricane of 1938.

REFERENCES

Burns, C., 2005. The Great Hurricane – 1938. Grove Press, New York, N.Y., 230 pp.

Fitzgerald, D. M., Fenster, M. S., Argow, B. A., and Buynevich, I. V., 2008. Coastal Impacts due to Sea-Level Rise. Annual Review of Earth and Planetary Sciences, 36: 601-647.

Krishnaswamy, S , Lal., D., Martin, J. M., and Mey- beck, M., 1971. Geochronology of Lake Sedi- ments. Earth and Planetary Science Letters, v. 11: p. 407-414.

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