Elemental Chemistry of Sediments From Two Drill Cores in Lake Qinghai, China, From Scanning XRF Analyses
Abstract
The Lake Qinghai Drilling Project (LQDP) obtained cores from a number of sites in Lake Qinghai, China, under the auspices of the International Continental Drilling Program and the Chinese Academy of Sciences. Although thick sands were encountered at depth at all sites, fine-grained sediments as much as 18-20 m thick were obtained, 2-3 times more than in any previous coring efforts. A well behaved sequence of radiocarbon ages, extending to more than 22 cal kyr BP, have been obtained for the upper 9 m of the 18 m of core from site 1, suggesting that the fine-grained sediments extend well past the Last Glacial Maximum. Elemental analyses of the sediments by scanning XRF methods at 2-5 mm intervals have been obtained for cores from drill sites 1 and 2. The overall trends in most elements from the two sites are remarkably similar, suggesting that the sedimentary records from the two sites correlate well. Differences in detail are relatively minor. One significant difference is the fact that the gypsum layer associated with the Younger Dryas in previous coring studies near drill site 1 appears in the XRF data up as a major peak in sulfur abundance at site 1, but no such peak exists at site 2. Ca abundance in the late glacial-to-Holocene section appears to correlate well with carbonate analyses from previous studies of nearby cores. Ca abundance varies slightly but remains low in the glacial-age sediments, and Ca/Ti ratios are nearly constant, suggesting an absence of authigenic carbonate. Ca variations in this interval appear to be related to variations is silica, probably from detrital (eolian?) quartz. Authigenic carbonate, inferred from Ca abundance and Ca/Ti ratios, begins to increase about ca. 14.5 cal kyr BP, and reaches its highest values ca. 10.5-7 cal kyr BP ka. This result is consistent with this interval being the warmest, wettest period of the Holocene. Inferred authigenic carbonate progressively decreases after 7 ca kyr BP, but remains well above glacial values.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMPP21A1392C
- Keywords:
-
- 1051 Sedimentary geochemistry;
- 1845 Limnology (0458;
- 4239;
- 4942);
- 4239 Limnology (0458;
- 1845;
- 4942);
- 4914 Continental climate records;
- 4942 Limnology (0458;
- 1845;
- 4239)