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The cosmogenic isotope 7Be (t1/2 = 53.3d) was measured in sediments collected from dust traps deployed in the Judean Desert which is part of the Dead Sea drainage basin. The results show that (a) the 7Be dry deposition flux in the Dead Sea region is 2.0 ± 0.6 × 104 atoms cm−2 y−1 during summer and winter and 5.3 ± 0.7 × 104 atoms cm−2 y−1 during fall; (b) the residence time of dust in the Dead Sea drainage basin is less than one year; (c) the recycled component of the cosmogenic isotope 10Be (t1/2 = 1.39 106y) in Judean desert dust is potentially small; and (d) the 7Be inventory (atoms cm−2) in dust settled in the drainage basin did not reach steady state between consecutive rare events of desert winter floods suggesting a short transport rate of fine detritus material from the marginal terraces into the Dead Sea. Provided 10Be behaves similarly (as implied by the common geochemistry and cosmogenic origin of 7Be and 10Be), we suggest 10Be in Lake Lisan (Pleistocene Dead Sea) detrital sediments as a potential proxy for paleo‐flood frequency and dust transport.

ABSTRACT. Carbon isotopic and chemical compositions of freshwaters feeding the Dead Sea and the Sea of Galilee (i.e. perennial streams and floods along their stream profiles) were used to constrain the factors that dictate the reservoir ages (RA) of these lakes and the last glacial Lake Lisan. Runoff waters are characterized by high Ca 2+ , Mg 2+ , alkalinity, and radiocarbon contents (67-108 pMC), suggesting a major role for ,4 C atmospheric exchange reactions (carbonate rock dissolution alone will result in lower pMC values). These exchange, processes were corroborated by dissolved inorganic carbon (DIC) and Ô 13 C trends throughout the flood profile. During the evolution from rain to incipient runoff, the 14 C DIC of the water increases and is accompanied by a DIC increase and Ô 13 C DIC decrease, suggesting an addition of soil C0 2 , which is characterized by light ô ,3 C and high 14 C content. When incipient runoffs evolve to floods, the opposite trends are observed.It appears that the Sea of Galilee, the Dead Sea, and its last glacial precursor, Lake Lisan, maintained uniform but specific RAs of 0.8 ±0.1, 2.3 ±0.1, and 1.6 ± 0.3 kyr, respectively. However, applying the 14 C contents of modern Dead Sea water sources to the water mass balance of Lake Lisan reveals that the RA of Lake Lisan is higher than that predicted by the mass balance. This discrepancy may reflect enhanced dissolution of carbonatic dust, changes in the amount of 14 C exchanged in Judean Desert floods, or variations in the contribution of brine and saline springs. Furthermore, the small fluctuations in the Lisan RA (1.6 ± 0.3 kyr) may reflect small, short-term changes in the relative contributions of these sources.

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