ðə ɹˈeɪʃɪˌoʊ ʌv ˈeɪtiːn ˈoʊ tə sˈɪkstiːn ˈoʊ ɪnðə ʃˈɛl ɪz jˈuːzd tʊ ˌɪndɚɹˈɛktli dɪtˈɜːmɪn ðə tˈɛmpɹɪtʃɚɹ ʌvðə sɚɹˈaʊndɪŋ wˈɔːɾɚɹ æt ðə tˈaɪm ðə ʃˈɛl wʌz fˈɔːɹmd.
The ratio of 18O to 16O in the shell is used to indirectly determine the temperature of the surrounding water at the time the shell was formed.