T205 Growing a Skeleton: Methodological and Theoretical Approaches to Unraveling the Stories Preserved in Skeletal Materials II

Thursday, 29 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

GLYCYMERIS NUMMARIA AS HIGH-RESOLUTION TRACE METAL ARCHIVES OF EASTERN MEDITERRANEAN ENVIRONMENTAL CHANGE

Paper number: T205-8
Program: Technical Sessions
Time: 3:10 PM – 3:25 PM

Authors

Abstract

High-resolution trace metal time series in bivalve shells have proven to be useful environmental archives for both modern and fossil specimens. Fewer studies have compared modern and fossil shells for the same locality, an approach which would be of particular use in the Eastern Mediterranean, where long-term natural and anthropogenic changes in Nile flow have brought about dramatic changes in nutrient cycling. We report on comparative high-resolution trace metal ratio transects undertaken via LA-ICP-MS on shells of the violet bittersweet clam Glycymeris nummaria, with ages ranging from ~4700 BP to the mid-20th century when the species largely disappeared from the Levant for reasons still poorly understood. Within fossil shells, we find reduced variability in Mg/Ca ratio indicative of a population still in the subadult phase when they died, before the seasonal cessations known to influence the Mg/Ca ratio in mature specimens of this genus. Meanwhile, seasonal Sr/Ca values show much more dramatic swings than is known from Glycymeris in the Adriatic, suggestive of a strong seasonal control on [Sr] present in this region, as well as higher mean Sr/Ca in fossil specimens. Lastly, Mn/Ca values show much more dramatic variability in modern specimens than their fossil counterparts. This is possibly indicative of the greater control of local erosional runoff on seasonal Mn availability (and thereby productivity) compared to historic times, when more consistent Nile transport was the main source of dissolved Mn. Through comparative high-resolution transects of fossil and modern specimens, we can investigate the high-resolution variability of trace metals in disparate windows of time, allowing us to interpret how long-term environmental changes influence the comparative life histories of historic and modern bivalves.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-353120

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