Age dating: visiting the University of Alabama

Introduction

Last week my research adviser and I visited the University of Alabama Geology department. Our lab works with them frequently. They have an amazing geochemistry stable isotope lab and very generously allow us to borrow equipment and process samples. It was very interesting to see first hand how my raw samples are processed. The main focus of this trip was to obtain ages and growth rates for several of my oysters.

Age Dating

Oysters are accretionary growers. Unlike human bones which are resorbed throughout our lifetime, oyster shell is deposited layer upon layer. Therefore, each stage in the oyster’s life cycle, from the very first piece of shell it grew to the very last, is preserved in the adult shell. In order to determine how many years the oyster lived, we sample small portions of powder at very small increments along the oyster’s hinge. It’s important to space samples as close together as possible, so that we can be sure we’re recording every year of the oyster’s life. Determining age allows us to calculate growth rate and lifespan. These two pieces of information are integral to oyster research.

Sampling

I sampled 4 shells from 4 different locations. Each shell was split in half down the length of the shell, exposing the interior. They were then coated in resin, ensuring they wouldn’t break during sampling. We sampled at a resolution of 2 samples per millimeter down the shell’s length using a micro mill. We then weighed the resulting powder and bottled it for testing. We should receive data indicating the age of each shell in about a month.

This was definitely a positive end to my summer research. We worked 12 hour days in order to finish everything during the 4 days we were in Alabama. Despite the hours it was truly a fun, rewarding experience that reaffirmed my love for research.

MG183A

One of the shells that we sampled. Notice a faint line along the very top of the hinge. This is composed of tiny dots where the drill removed powdered shell material.

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