SPATIAL PATTERN OF DEGLACIAL CLIMATIC OSCILLATIONS AND VEGETATION RESPONSES FROM ATLANTIC SEABOARD TO GREAT LAKES REGION IN EASTERN NORTH AMERICA: EVIDENCE FROM LACUSTRINE STABLE-ISOTOPE AND POLLEN RECORDS

Large and abrupt climatic oscillations occurred during the last deglaciation evident in ice, lacustrine and marine records from different geographic regions. Stable isotopes retrieved from these records could potentially provide a common proxy in correlating these records and detecting temporal and spatial patterns, which are critical in understanding the nature and regional gradients of climate changes and thus their forcing mechanisms. Here I provide new isotopic and pollen results from the Mid-Atlantic region of USA to expand the existing late-glacial isotopic records from the Great Lakes region toward the Atlantic Seaboard. White Lake, a marl lake in northwestern New Jersey, provides high-resolution sedimentary records since ice retreat (as early as 20,000 cal BP). Preliminary isotope results of marl bulk samples (contain >90% carbonates) from this site show >3‰ shift in oxygen isotopes between -8 and -4‰ during the late glacial and early Holocene, indicating distinctive multiple oscillations at millennial and centennial scales. Pollen stratigraphy suggests the timing of these shifts representing the Bölling-Alleröd warm period, including three short-lived cooling events (intra-Bölling cold period, Older Dryas, and intra-Alleröd cold period), the Younger Dryas and Preboreal Oscillation. Oxygen and carbon isotopes show strong covariation during these climate events. Pollen sequence from this site is similar to previously published extensive pollen records from this region, which indicate the Younger Dryas event as a return of boreal taxa (including Abies and Alnus) after establishment of a mixed deciduous-coniferous forest containing Quercus, Fraxinus and Ostrya/Carpinus. Combined isotope (as an independent climate indicator) and pollen data from the same sites shed new light into understanding the nature of late-glacial vegetation change in this region and sensitivity of upland vegetation to abrupt climate changes. Close-interval AMS dating of this record and others in this region is ongoing, and isotope analysis of shells from ostracodes calcified during different seasons would provide insight into potential change in seasonality associated with these climatic oscillations.