The majority of bitumen, on the other hand, was formed naturally when vast quantities of organic animal materials were deposited by water and buried hundreds of metres deep at the diagenetic point, where the disorganized fatty hydrocarbon molecules joined in long chains in the absence of oxygen.
ðə mədʒˈɔːɹᵻɾi ʌv bɪtˈuːmɛn, ɔnðɪ ˈʌðɚ hˈænd, wʌz fˈɔːɹmd nˈætʃɚɹəli wɛn vˈæst kwˈɔntᵻɾiz ʌv ɔːɹɡˈænɪk ˈænɪməl mətˈɪɹiəlz wɜː dᵻpˈɑːzɪɾᵻd baɪ wˈɔːɾɚ ænd bˈɛɹid hˈʌndɹɪdz ʌv mˈiːɾɚz dˈiːp æt ðə dˌaɪədʒɪnˈɛɾɪk pˈɔɪnt, wˌɛɹ ðə dɪsˈoːɹɡənˌaɪzd fˈæɾi hˈaɪdɹəkˌɑːɹbən mˈɑːlɪkjˌuːlz dʒˈɔɪnd ɪn lˈɔŋ tʃˈeɪnz ɪnðɪ ˈæbsəns ʌv ˈɑːksɪdʒən.