A record of Lateglacial and early Holocene environmental and ecological change from southwestern Connecticut, USA

W Wyatt Oswald,Elaine D Doughty,David R Foster,Edward K Faison

doi:10.1002/jqs.1299

Abstract

AbstractAnalyses of a sediment core from Highstead Swamp in southwestern Connecticut, USA, reveal Lateglacial and early Holocene ecological and hydrological changes. Lateglacial pollen assemblages are dominated by Picea and Pinus subg. Pinus, and the onset of the Younger Dryas (YD) cold interval is evidenced by higher abundance of Abies and Alnus viridis subsp. crispa. As climate warmed at the end of the YD, Picea and Abies declined and Pinus strobus became the dominant upland tree species. A shift from lacustrine sediment to organic peat at the YD–Holocene boundary suggests that the lake that existed in the basin during the Lateglacial interval developed into a swamp in response to reduced effective moisture. A change in wetland vegetation from Myrica gale to Alnus incana subsp. rugosa and Sphagnum is consistent with this interpretation of environmental changes at the beginning of the Holocene. Copyright © 2009 John Wiley & Sons, Ltd.

Highlights

Environmental and ecological changes associated with the Younger Dryas (YD) climatic oscillation
The changes observed in the Highstead Swamp record at ~13,000 cal yr BP, including declining percentages of Ostrya-Carpinus pollen and higher abundances of Abies and Alnus, are consistent with pollen data from sites in southern New
The ~5 C drop in temperatures at the beginning of the YD (Shemesh and Peteet, 1998; Yu et al, 1998; Cwynar and Spear, 2001; Yu, 2007) appears to have shifted vegetation assemblages across the region towards cold-tolerant taxa (Shuman et al 2002), some ecological changes may have been underway in advance of the onset of YD cooling (Lindbladh et al, 2007)

Summary

Introduction

Environmental and ecological changes associated with the Younger Dryas (YD) climatic oscillation (12,900-11,600 calibratedC years before present; cal yr BP) have been studied at many sites in eastern North America using a variety of approaches (e.g., Peteet et al, 1990; Levesque et al, 1993; Mayle et al, 1993; Cwynar and Levesque, 1995; Shemesh and Peteet, 1998; Yu and Eicher, 1998; Lavoie and Richard, 2000; Newby et al, 2000; Cwynar and Spear, 2001; Huang et al, 2002; Shuman et al, 2001, 2002; Hou et al, 2007; Lindbladh et al, 2007; Yu, 2007). Pollen records typically feature an increase in cold-tolerant taxa at the beginning of the YD and a shift to taxa indicative of warmer conditions at the YD-Holocene boundary (e.g., Shuman et al, 2002). Late-glacial changes in moisture balance, on the other hand, have received less study. Lake-level reconstructions from southern Québec (Lavoie and Richard, 2000) and southeastern Massachusetts (Newby et al., 2000; Shuman et al, 2001) indicate relatively wet conditions during the YD and drier climate at the beginning of the Holocene, but other records of moisture-balance shifts associated with the YD have not been developed.

Methods

Results

Conclusion