20 Reconstructing Environmental Change from Marine, Lacustrine, and Terrestrial Sedimentary Records

Saturday, 29 March 2025
8:00 AM - 12:00 PM
170B

WETLAND DEPOSITS RECORD MILLENNIAL-SCALE HYDROCLIMATE VARIABILITY OVER THE PAST 30,000 YEARS IN SOUTHERN JORDAN

Paper number: 20-6
Program: Theme Sessions
Time: 9:25 AM – 9:45 AM

Authors

Abstract

Understanding the dynamics between temperature change and water availability in the Levant is vital as the region is facing extreme water scarcity while the modern climate continues to warm. Synoptic climatology in the Levant is complex, with multiple air mass trajectories converging in the region. This has led to a lack of consensus among researchers regarding how millennial-scale climate perturbations, both in the past and in the future, impact the water budget. The study site is in Gregra, Jordan, within the Jordan Valley at an elevation of ~115 m asl and the modern water table is ~6 m below the ground surface. The occurrence of wetland deposits in the currently hyper-arid climate indicates the water table was higher in the past as a result of a wetter climate. The majority of Pleistocene wetland deposits in the region are marls, yet at the study site, there is a 2.5 m thick peat (up to 27 wt % organic carbon) that interfingers with the marl and allows for excellent age control. Particle size, total organic carbon, and bulk chemistry was measured throughout the section to determine how the water budget and eolian sediment supply in the study area fluctuated during and since Last Glacial Maximum (LGM, ~26,000 yrs BP). The lowermost age returned from the study site was 27,900 ± 650 cal yrs BP, indicating a minimum age for the onset of a perennial wetland environment. A drying period was interpreted from the presence of an unconformity between 23,200 ± 200 cal yrs BP and 24,000 ± 300 cal yrs BP, correlated to Heinrich event 2. An unconformity and evidence of soil formation after 17,200 cal yrs BP roughly corresponds to Heinrich event 1, which began 17,000 years ago. After this period of drying no wetland environment persisted at the study site, and approximately 3 m of eolian sand overlie the peat. Results indicate a high water table corresponds to LGM and millennial scale cooling events cause increased aridity in the Levant. These findings suggest a link between Heinrich events and climatic drying in the Levant, supporting records from Lake Lisan.

Geological Society of America Abstracts with Programs. Vol. 57, No. 3

doi: 10.1130/abs/2025NE-408167

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