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(2020) Climate and Environmental Change in the SW-Pacific of the Last ~14, 000 Years Using Lipid Biomarkers in Sediments of a New Zealand Lake
Naeher S, Bauersachs T, Stucker VK, Puddick J, Wood SA, Robert S, Schubert CJ & Vandergoes MJ
10g: Room 3, View in program
Listed below are questions that have been submitted by the community that the author will try and cover in their presentation. To submit a question, ensure you are signed in to the website. Authors or session conveners approve questions before they are displayed here.
Nice talk! I am curious if you have considered that your records might be affected by ice in the catchment or even glaciers at points in the past? Based on the high elevation and position I expect this could be a key factor. Also have you looked at the BIT index of the GDGTs? This might be helpful in determining a terrestrial record which you can compare with your n-alkanes.
Hi Mark, Thanks so much for your message and I am happy that you like our talk. Yes, you are right about the glaciers. Today, the region does not have any glaciers but we know that there is evidence of alpine glaciation during the Pleistocene. The lake sits in a glacial cirque of 3.8 km2 and we know that the early pollen record is likely influenced by having both cold and warm indicators and seems to gives us an ambiguous climate signal that is likely related to glaciers. We need to be careful when interpreting our biomarker records, but I guess it is difficult to quantify the actual impact on the biomarker records though? Yes, GDGTs are one of several indicators (n-alkane distributions, higher plant biomarkers, etc) that show us that the OM in the lake sediments is mainly derived from the lake catchment/surrounding soils. The BIT is pretty much at 1 for all samples. Thanks again and please let me know if you have any further questions or comments. Best wishes, Sebastian
Interesting talk! Just one question/remark: Aside ACL based on C27,C29, and C31, did you also calculate C29/C31 ratios? In such small lakes with both macrophyte and terrestrial contribution, C27 is often a mixture of those two sources. Hints for that are that Paq basically mirrors the calculated ACL in your record. Also, dD values of C27 are more enriched then long-chains, which could be evidence for - an at least partial - contribution of aquatic sources. In that terms, C29/C31 is - maybe - a more reliable indicator for changes of terrestrial sources. In any case, it´s great that you have a quality pollen record for comparison, and to help interpreting your results.
Hi Bernhard, Thanks for your message and happy that you like our talk. Sorry for my late response as I have not seen your question/remark earlier. Yes, I agree with you that C27 is likely of mixed origin and therefore may bias to some degree what we see with changing ACL. Indeed, the C29/C31 ratio looks a little different than the ACL profile and it is sad that I cannot show you how the profile through this message board. We see that there is a dominance of either C29 or C31 in the samples, which indicates changes in vegetation, but interestingly, this fits less good with our pollen record, so we feel that Paq and ACL are more meaningful to compare biomarker and pollen records. I wonder if we can explain this by only using two alkane homologues (and therefore individual variations/scatter?) instead of a whole series of compounds as per ACL and Paq? In any case, I agree that the ACL is affected by aquatic plants and so it mirrors Paq, even if we exclude C25, which again indicates mixed contributions of n-C27 alkane.
Hi all, if you want to discuss more or have any questions, I would be glad to hear from you! Please get in touch with me by email (instead of posting here in the future as I likely won't look at this page anymore), which you can find at the last slide of the talk or in the abstract. Thank you. Cheers, Sebastian
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