Sources of organic matter in the surface sediments from Lake Sihailongwan Maar and Lake Zhanjiang Maar (Lake Huguangyan Maar) in China

•Higher TOC content was observed in the sediment from Lake Sihailongwan Maar than in that from Lake Zhanjiang Maar.•Aquatic FAs were the main lipids, with alga the major contributor, and FAs from anaerobic bacteria were main components of FAs from bacteria.•The higher microbial reworking components have been found in bound n-alkanols and FAs than in free n-alkanols and FAs.•The aquatic OM fractions are relatively higher in the lower latitude maar lake sediments, mainly due to higher light intensity and MAWT.