We demonstrate that by using detailed pre-treatment on samples, closely examined samples, measurements with higher precision are possible.
Tephra fragments are classified by size: In geology and related fields, a 'stratum' (plural: 'strata') is a layer of rock or soil with internally consistent characteristics that distinguish it from other layers.
Each layer is generally one of a number of parallel layers that lie one upon another, laid down by natural forces.
For example, a widespread tephra erupted from the Tūhua caldera (Mayor Island) about 7,000 years ago contains very unusual minerals.
This tephra can be identified instantly with a microscope, even from just a few grains.
dates measured for paleosols directly underlying a tephra layer have proved to represent the accurate eruption age of the tephra, and have successfully established the high-resolution eruptive histories of several volcanoes.
In addition, oceanic and lacustrine sediments have preserved a large number of tephra layers, and accelerator mass spectrometry ages from several horizons of peat sediments to INTCAL98 calibration data that was established by dendrochronology as well as by varve chronology has enabled us to obtain highly accurate ages of tephras intercalated in the peat deposits.
How can one tephra layer be distinguished from another?
Scientists use many methods to characterise or fingerprint each layer, both in the landscape and laboratory.
Tephra (volcanic ash) layers provide unique chronostratigraphic maker beds in geosciences, allowing ages to be transferred to adjacent units and across regions.
Therefore, it is important to establish the application of radiocarbon dating of tephra layers with high levels of reliability.
Such an established event provides a "tephra horizon".