3:30 PM - 3:45 PM
[STT53-07] Red thermoluminescence (RTL) dating of Pleistocene volcanic quartz
Keywords:Red thermoluminescence dating, Pleistocene tephra, RTL emission pattern
RTL research we have been carrying out using some tephra quartz grains in middle Pleistocene (ex. Hakkoda 1st stage pyroclastic flow) showed three type RTL emission patterns; mono-peak type, double-peak type and broad type.
A broad type with double peaks at around 300 and 360°C showed a quite different pattern when compared to the typical shape of a mono-peak type being commonly used for RTL dating, such as a late Pleistocene Toya tephra (Ganzawa et al, 2005).
The broad type of RTL emission is originating in ignimbrite, suggesting a high emplacement temperature over 800°C. Heating quartz grains up to 1000°C, using Hakkoda aquatic pyroclastic flow fixed at a temperature lower than 200°C, clearly showed a change of the RTL emission pattern from a mono-peak type to a broad type in accordance with temperature increment. The RTL pattern heated at 800°C agreed well with the pattern of the Hakkoda ignimbrite, presumably showing the emplacement temperature of 800°C in the volcanic products.