T79 Modern and Ancient Saline Lakes

Monday, 5 November 2012
8:00 AM - 9:30 AM
219AB

BIOGEOCHEMISTRY OF THE AL AZRAQ BASIN, JORDAN: DIFFERENTIATING BETWEEN TERRESTRIAL AND AQUATIC SOURCES OF ORGANIC CARBON

Paper number: T79-1
Program: Technical Sessions
Time: 8:00 AM – 8:15 AM

Authors

Abstract

The Al-Azraq basin, a closed basin and the second largest on the Jordan Plateau, contains a long and detailed sediment record of paleoenvironment change. This study identifies organic matter (OM) sources and their environments of formation. Biogeochemistry, stable isotopes and mineralogy reveal biological processes that detail a lake history significantly different from present conditions. Analysis of two hundred and fifteen samples from 23 m of playa lake sediment identifies the presence and distribution of organic matter (OM). Changes in the proportion (%) of OM, C/N ratio, carbon isotopic composition and sediment characteristics are the basis for dividing the basin into five environmental zones. The distribution of OM (as Corg), increases with depth, ranging from 0.2% to 2.8% of the total sediment. The carbon isotopic composition values range from -26.8 to -15.00. These values indicate the abundance of C3 and CAM vegetation in the basin as a possible function of changing climates on the Jordan Plateau. C/N values differentiate terrestrial and lake OM sources. The changes in Corg %, source composition and OM origin establish a wide range of past environments that varied considerably from being both drier and wetter than the present conditions.