Distributions of C22–C30 even-carbon-number n-alkanes in Ocean Anoxic Event 1 samples from the Basque-Cantabrian Basin
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- Chaler, R., Dorronsoro, C., Grimalt, J.O. et al. Naturwissenschaften (2005) 92: 221. doi:10.1007/s00114-005-0616-2
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The Ocean Anoxic Event 1 (OAE-1) in central sites of the Basque-Cantabrian Basin exhibits very reducing depositional conditions of sedimentation. These sedimentation events have left a distinct mixture of hydrocarbons that are represented by C22–C30 n-alkanes with a predominance of the even-carbon-number homologues, high relative proportions of squalane and C16–C24 n-alkylcyclopentanes predominated by n-undecyl-, n-tridecyl- and n-pentadecylcyclopentane. Other minor compounds encompass a series of C18–C21 n-alkylcyclohexanes and C18–C24 dimethyl n-alkylcyclohexanes maximized by the even-carbon-number homologues as well as iso- and anteiso-alkanes. This unusual distribution of n-alkanes in this environment provides a new case for comparison with previously reported hypersaline and phosphorite sedimentary deposits where the occurrence of similar n-alkane distributions was reported. In the present case, these major n-alkanes and squalane are indicative of transformation under strong reducing conditions. In contrast, the occurrence of the alkylcyclopentanes, irrespective of the presence of even-carbon-number n-alkanes or squalane, suggests that reductive cyclization of fatty acids is less dependent on strong reducing conditions.