Belle E. Philibosian Aron J. Meltzner Chung-Che Wu Chuan-Chou Shen R. Lawrence Edwards Chih-Kai Chuang Bambang W. Suwargadi Danny H. Natawidjaja Hong-Wei Chiang 2023 <p><span>One of the key factors in obtaining precise and accurate&nbsp;</span>²³⁰<span>Th ages of corals, especially for corals with ages less than a few thousand years, is the correction for non-radiogenic&nbsp;</span>²³⁰<span>Th based on an initial&nbsp;</span>²³⁰<span>Th/</span>²³²<span>Th value (</span>²³⁰<span>Th/</span>²³²<span>Th</span>₀<span>). Studies that consider coral&nbsp;</span>²³⁰<span>Th/</span>²³²<span>Th</span>₀<span>&nbsp;values in intertidal environments are limited, and it is in these environments that corals have Th concentrations 100–1000 times greater than open-ocean corals. Here we present 66 reconstructed U–Th isochrons of modern and&nbsp;Holocene&nbsp;</span><i>Porites lutea</i><span>&nbsp;and&nbsp;</span><i>lobata</i><span>&nbsp;corals from throughout the Sumatran forearc islands (SFI). Mean square of weighted deviates (</span><i>MSWD</i><span>) is used to evaluate the variabilities of 28 location-specific&nbsp;</span>²³⁰<span>Th/</span>²³²<span>Th0 values before the regional mean. Results show no significant spatial difference between the means of 3.1&nbsp;±&nbsp;3.2&nbsp;×&nbsp;10</span>⁻⁶<span>&nbsp;for the northern SFI and 4.7&nbsp;±&nbsp;1.3&nbsp;×&nbsp;10</span>⁻⁶<span>&nbsp;for the southern SFI. Using the weighted mean of 4.3&nbsp;±&nbsp;2.5&nbsp;×&nbsp;10</span>⁻⁶<span>&nbsp;for all islands has the advantage that no data need be subjectively excluded in the calculation of reliable&nbsp;</span>²³⁰<span>Th ages, where a local initial value is unknown. There were no clear centennial to millennial time-scale changes in&nbsp;</span>²³⁰<span>Th/</span>²³²<span>Th</span>₀<span>&nbsp;in the past 2500 years. This study, therefore, suggests a reliable value of initial&nbsp;</span>²³⁰<span>Th/</span>²³²<span>Th ratio in intertidal environments.</span></p> application/pdf 10.1016/j.quascirev.2023.108005 en Elsevier Investigating spatio-temporal variability of initial 230Th/232Th in intertidal corals article