This study focuses on HAP0212, a 332-cm-long undisturbed core taken from the deepest part of the basin. Here, we reappraised bottom unit 4 (272 to 320 cm)— homogenous, dense, and minerogenic sediments that were excluded from previous work on the Holocene lake history by (13) because of “improbably old” radiocarbon ages [16,580 ± 180 and 25,100 ± 300 14C yr B.P. (radiocarbon years before the present)] and signs of dewatering. We characterized the stratigraphy of unit 4 sediments using four parameters on a common 0.5-cm resolution. Sediment density [dry bulk density (DBD)] and water content, basic measures for compaction (9), were determined. Magnetic susceptibility (MS), an indicator of detrital input (15), was measured using a Bartington MS2E sensor. We also measured loss on ignition (LOI) on these samples, a basic measure of organic content, following the protocol by (16). To assess sediment provenance, we carried out x-ray diffraction (XRD) analysis on 14C-dated depth intervals (n = 3). For this purpose, we sieved sample material through a 63-μm mesh and separated clay from silt using gravity settling. Both fine fractions were then analyzed as randomly oriented dry powders on a Bruker D8 ADVANCE ECO X-ray diffractometer. Last, we visualized sedimentary structure in three dimensions (3-D) using a ProCon X-Ray ALPHA Computed Tomography (CT) scanner. Extensive sampling of HAP0212 for previous work (13) has restricted this exercise to selected depth intervals. In addition, we tried to extract lipids from analyzed unit 4 sediments in mixture of dichloromethane (DCM) and methanol (9:1 volume %) with a Dionex ASE 350 system. So far, all analyzed samples (n = 5) were devoid of identifiable compounds following gas chromatography mass spectrometry and flame ionization detection.

Note: The content above has been extracted from a research article, so it may not display correctly.

Please log in to submit your questions online.
Your question will be posted on the Bio-101 website. We will send your questions to the authors of this protocol and Bio-protocol community members who are experienced with this method. you will be informed using the email address associated with your Bio-protocol account.

We use cookies on this site to enhance your user experience. By using our website, you are agreeing to allow the storage of cookies on your computer.