Establishment of 14C chronology of Lake Qinghai and the application of Mean Value Concept to removal of Old Carbon Effect
Abstract
The largest inland lake in China, Lake Qinghai, has experienced apparently continuous sedimentation since the Pliocene. Its unique geologic setting and potential for high-resolution records makes Lake Qinghai an ideal site to study past environmental changes in the inland continental setting. Since 2004 "Scientific Drilling at Lake Qinghai in the Northeastern Tibetan Plateau: High-resolution Paleoenvironmental Records of Eastern Asia Linked to Global Change" (QHDP) was on-schedule. One of the multi-disciplinary studies for the QHDP project is to establish a reliable and high resolution geochronology stratigraphy, which is crucial to quantify the time resolution of the proxies, and will be the foundation for all subsequent studies of climate, environment, and tectonic. However, there is no varve or dated archeological remains available in the core sequence from lake Qinghai, and the living fish and algae seeds there all have been polluted by the nuclear explosion, which have made it difficult to calibrate the chronology for Qinghai core. Furthermore, the traditional regression analysis method to establish the lake chronology did not consider the different accumulation rate in the core sequence, which would introduce the significant error into the established chronology. In this paper, we use 14C-AMS technique to measure organic carbon, non-organic carbon and plant seeds from drilling core sequences, 1F(36°48'40.7"N,100° 08'13.5"E)with 18m deep in Qinghai lake. By introducing the "mean value concept" in the linear regression analysis of a multi-variable geological system into the traditional regression method and dividing the 18m deep core sequence into two sections according to their different accumulation rates, we have established the 14C chronology of the Qinghai lake and determined the average dead carbon age of about 260 yr and 650 yr for the core sequence above and below about 12m depth respectively. The results above the 12m depth are compared with ones obtained from the wiggle matching method and in good coincidence with each other.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMPP21A1389Z
- Keywords:
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- 1100 GEOCHRONOLOGY;
- 1105 Quaternary geochronology;
- 1115 Radioisotope geochronology;
- 1165 Sedimentary geochronology;
- 1194 Instruments and techniques