Journai of Coastal Research SI 11 125-158 Fort Lauderdale. Florida Fall 1991 Paleo-Environmental Analyses of Marsh Sequences (Clinton, Connecticut): Evidence for Punctuated Rise in Relative Sealevel During the Latest Holocene E. Thomas' and J.C. VarekamP+ .Department of Earth Sciences University of Cambridge Cambridge CB2 3EQ, UK II{TRODUCTION Global sea level has been rising since the ini- tiation of the last deglaciation about 15,000 years ago, predominantly because of melting of the polar ice sheets and continental glaciers (e.g., W.a.LCorr, 1972; CLARK et al.,I97 8; NtxoN, 1982 ). This process will continue over the fore- seeable future,, and in macro- and micro-plan- ning of society and economy one can not neglect the fact that shorelines will keep retreating in the future. Models for future sea level rise are based either on computational models that take th e rising temperature caused by the atmos- pheric anthropogenic greenhouse effect into account, or extrapolate historic trends in rela- tive sea level rise into the next century. Many of these models assume a smooth time-function for the change in sea level during the past and 91A66 receiued and accepted in reuision 28 July 1991' rDepartment of Earth and Environmental Sciences Wesleyan University Middletown, CT 06457 , IJ.S.A. ABSTRACT THOMAS, E. and VAREKAMP, J.C., 1991. Paleo-environmental analyses of marsh sequences (Clinton, Connecticu;: evidence for punctuated rise in relative sealevel during the latest Hol- ocene. Journal of Coastal Researcft, SI #Ll.125-158. Fort Lauderdale (Floridal. ISSN 0749' 0208. We developed an integrated chemical-faunal approach to paleo-environmental analysis of salt marsh seciuences. Sediment cores from the Hammock River Marsh (Clinton, Connecticut, I-i.S.A.) were studied for benthic foraminiferal assemblages and sediment chemistry (Fe. Zn, Cu, S). Foraminiferal faunal assemblages, especially the relative abundance of the species 7ro- chantmina macrescens. as well as the abundance of Fe, Zn and S are reliable indicators for the flooding frequency of marsh sub-environments in the intertidal range. The faunal assemblages largely reflect the average exposure time to the atmosphere, and the sediment chemistry reflects tfrJtrapping of fine-grained particulate matter in the marsh, and thus reflects the complemen- tary aspect, flooding f."qrr"ncy. Results from the chemical and faunal analyses are in close "g.""-Lnt, and indicate that the Hammock River Marsh underwent three relatively sudden periods of drowning over the last 1500 years, followed by marsh recovery. Much of the rise in ielative sea level over the last 1500 years can be accounted for by these three periods of drown- ing of the marsh. We propose that these pulses might represent true eustatic accelerations rn'ith an estimated time span of several decades to some hundred years. ADDITIONAL INDEX WORDS: Clirnate change, rnarsh foramini.fera, sea leuel rise, trace ele- ments in marsh sedime.nts. in the near future. Exceptions to this general- ization are studies by FaTRBRIDGE ( 1961 , 1981 , 1987), MonRNER ,1976,1980, 1987), RauptNo and SaNnBns (1981), vAN DE Plasscsp (1982), Scorr and MnoIoLI (1986) and Knapr et al. (1987), among others, who interpreted the available data for the last several thousands of years as indicative of a fluctuating pattern of sea level rise, with oscillations on the order of hundreds of years. Most studies of sea level rise over the last few millennia document age-depth profiles in sedi- ments from the intertidal range, based on sam- ple intervals of several hundreds of years. The scattered data points are commonly connected through a least-squares regression analysis with a straight line or with a curve based on an exponential fitting routine (e.g., PtNrun and GannNER, 1989). These studies assume that the scatter in data points is related to compaction, illlJl,l:- TOOOOOOOOOOO .t!.ffi