The C32 alkane-1,15-diol as a proxy of late Quaternary riverine input in coastal margins
Lattaud, J.; Dorhout, D.; Schulz, H.; Castañeda, I.S.; Schefuß, E.; Sinninghe Damsté, J.S.; Schouten, S. (2017). The C32 alkane-1,15-diol as a proxy of late Quaternary riverine input in coastal margins. Clim. Past 13(8): 1049-1061. https://doi.org/10.5194/cp-13-1049-2017
Additional data:
In: Climate of the Past. Copernicus: Göttingen. ISSN 1814-9324; e-ISSN 1814-9332, more
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| Authors | | Top |
- Lattaud, J., more
- Dorhout, D., more
- Schulz, H.
- Castañeda, I.S., more
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- Schefuß, E.
- Sinninghe Damsté, J.S., more
- Schouten, S., more
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| Abstract |
The study of past sedimentary records fromcoastal margins allows us to reconstruct variations in terrestrialinput into the marine realm and to gain insight intocontinental climatic variability. There are numerous organicproxies for tracing terrestrial input into marine environmentsbut none that strictly reflect the input of river-produced organicmatter. Here, we test the fractional abundance of theC32 alkane 1,15-diol relative to all 1,13- and 1,15-long-chaindiols (FC32 1,15) as a tracer of input of river-produced organicmatter in the marine realm in surface and Quaternary (0–45 ka) sediments on the shelf off the Zambezi and nearbysmaller rivers in the Mozambique Channel (western IndianOcean). A Quaternary (0–22 ka) sediment record off the NileRiver mouth in the eastern Mediterranean was also studiedfor long-chain diols. For the Mozambique Channel, surfacesediments of sites most proximal to Mozambique riversshowed the highest F1,15−C32 (up to 10 %). The sedimentaryrecord shows high (15–35 %) pre-Holocene F1,15−C32 andlow (< 10 %) Holocene F1,15−C32 values, with a major decreasebetween 18 and 12 ka. F1,15−C32 is significantly correlated(r2 = 0.83, p < 0.001) with the branched and isoprenoidtetraether (BIT) index, a proxy for the input of soil and riverproducedorganic matter in the marine environment, whichdeclines from 0.25 to 0.60 for the pre-Holocene to < 0.10 forthe Holocene. This decrease in both FC32 1,15 and the BIT isinterpreted to be mainly due to rising sea level, which causedthe Zambezi River mouth to become more distal to our studysite, thereby decreasing riverine input at the core location.Some small discrepancies are observed between the recordsof the BIT index and FC32 1,15 for Heinrich Event 1 (H1)and the Younger Dryas (YD), which may be explained bya change in soil sources in the catchment area rather than achange in river influx. Like for the Mozambique Channel, asignificant correlation between FC32 1,15 and the BIT index(r2 = 0.38, p < 0.001) is observed for the eastern MediterraneanNile record. Here also, the BIT index and FC32 1,15are lower in the Holocene than in the pre-Holocene, whichis likely due to the sea level rise. In general, the differencesbetween the BIT index and FC32 1,15 eastern MediterraneanNile records can be explained by the fact that the BIT indexis not only affected by riverine runoff but also by vegetationcover with increasing cover leading to lower soil erosion. Ourresults confirm that FC32 1,15 is a complementary proxy fortracing riverine input of organic matter into marine shelf settings,and, in comparison with other proxies, it seems not tobe affected by soil and vegetation changes in the catchment area |
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