54 Application of Organic Geochemical Proxies to (Paleo)Environmental Studies

Tuesday, 21 March 2017
9:35 AM - 12:00 PM
Frick, Conference Level

IDENTIFYING BASIN-SPECIFIC CONTROLS ON LEAF WAX RECORDS IN LAKE SEDIMENTS OF THE ADIRONDACK MOUNTAINS, NEW YORK

Paper number: 54-2
Program: Theme Sessions
Time: 9:55 AM – 10:15 AM

Authors

Abstract

The hydrogen isotopic composition of leaf waxes (dDwax) primarily reflects that of plant source water. Therefore, sedimentary δDwax records are increasingly used to reconstruct the δD of past precipitation (δDp) and to investigate paleohydrologic changes. Such reconstructions rely on estimates of apparent fractionation (εapp) between δDp and the resulting δDwax. While numerous studies have calibrated εapp offsets between modern δDp and δDwax in living plants, relatively few have assessed the effects of leaf wax integration, transport and deposition on εapp values in sediments. Here, we evaluate the influence of basin-specific factors on sedimentary leaf wax composition from multiple lakes in the same region with similar local δDp.

We report δDwax and εapp values from the uppermost sediments of seven lakes within the Adirondack Mountains in NY that vary in terms of their vegetation structure, basin size, shoreline slopes, surface erosion and fluvial inputs. Leaf wax analyses include n-alkanes and n-alkanoic acids, both of which are commonly applied in paleohydrology reconstructions. Molecular and isotopic leaf wax data from each lake are interpreted in the context of sediment properties including grain size, bulk organic content, and bulk sediment δ13C and C:N ratios. We compare εapp values among lakes and investigate potential relationships with basin morphology, sediment composition and transport processes specific to each site. We also compare the abundance, molecular distribution and δDwax composition among two major leaf wax classes (n-alkanes and n-alkanoic acids) to examine differences in fractionation between these compounds at the sediment level.

Geological Society of America Abstracts with Programs. Vol. 49, No. 2

doi: 10.1130/abs/2017NE-291150

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