Late-Pleistocene and Early-Holocene climate signals in lake-sediment delta18O records from the northeastern United States.

摘要

In this thesis, I present a new oxygen isotope (delta18O) record from carbonate-rich lake sediments from central Vermont. The record spans from 13.5 ka (thousands of calibrated radiocarbon years before 1950 AD) to present. Due to a multi-millennial hiatus starting shortly after 7.5 ka, I focus on the first 6.0 ka of the record and compare it with previously published delta18O data from the region. The comparison allows me to determine the regional isotopic variation, which results from the interacting effects of temperature, moisture source, moisture balance (aridity), and seasonality. Furthermore, the comparison reveals the regionally-coherent characteristics of the isotope signal, which are likely related to large-scale climatic mechanisms such as insolation, greenhouse gases, progressive decline of the Laurentide Ice Sheet (LIS), and changes in oceanic circulation. The multi-record comparison also exposes contemporaneous, but opposing isotopic changes across sites, which suggest shifts in the regional isotopic gradients.