CORRELATING MULTI-PROXY DATA ACROSS MULTIPLE BASINS IN WALDEN POND (MA, USA): EVIDENCE OF SUDDEN ONSET EVENTS AND HUMAN IMPACT

Walden Pond (Concord, MA, USA) has long held important value from a cultural, ecological, and geological perspective. While much research has been performed, little has been done showing the utility of comparing sediments across the multiple basins in the pond. This project will present multiproxy data from six cores to correlate observed events over the last 500 years across the three main basins in Walden Pond. A series of fires in the late 1890s and early 1900s allowed all six cores to be correlated using a combination of palynological, geochemical, and sedimentological proxies: an increase in elements associated with terrigenous sediments using μXRF analysis and peaks in charcoal, carbonaceous particles, and sporomorphs of shoreline aquatics followed by an increase in early successional plants identify this event in each basin. Changes in grain size, organic carbon, and nearshore aquatic taxa also indicate redeposition of shoreline sediments, and sharp declines in aquatic taxa in immediately overlying sediments suggest possible seiche activity following mass transport. This is inferred to be a result of shaking from the 1638 New Hampshire earthquake, at the base of the colonial zone dating to European settlement of Concord beginning in 1635. These results seen in all three main basins of Walden Pond support a synchronous trigger affecting the entire water body. This illustrates that there is significant value in using multiple cores to correlate events within a single water body, and it shows the potential of this multiproxy approach to disentangle anthropogenic influence from significant natural events in the paleoecological record, even if these events occur temporally close together.