Transition from arid to hyper-arid environment in the southern Levant deserts as recorded by early Pleistocene cummulic Aridisols

Rivka Amit, Ori Simhai, Avner Ayalon, Yehouda Enzel, Ari Matmon, Onn Crouvi, Naomi Porat, Eric McDonald

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The time at which deserts established their current arid or hyper-arid conditions remains a fundamental question regarding the history of Earth. Cosmogenic isotope exposure ages of desert pavement and welded, calcic-gypsic-salic Reg soils that developed on relatively flat alluvial surfaces ∼2 Ma ago in the Negev Desert indicate long geomorphic stability under extremely dry conditions. Over a short interval during their initial stage of development between 1-2 Ma, these cumulative soils are characterized by calcic soils reaching maximum stage III of carbonate morphology. This interval is the only period when calcic soil horizons formed on stable abandoned alluvial surfaces in the southern Negev Desert. Since ∼1 Ma pedogenesis changed toward more arid soil environment and the formation of gypsic-salic soil horizons that were later followed by dust accumulation. The dichotomy of only moderately-developed calcic soil (stages II-III) during a relatively long time interval (105-106 years) indicates an arid environment that does not support continuous development but only occasional calcic soil formation. The very low δ18O and relatively high δ13C values of these early pedogenic carbonates support soil formation under arid climatic conditions. Such an environment was probably characterized by rare and relatively longer duration rainstorms which occasionally allowed deeper infiltration of rainwater and longer retention of soil moisture. This, in turn enabled the growth of sparse vegetation that enhanced deposition of pedogenic carbonate. At ∼1 Ma these rare events of slightly wetter conditions ceased and less atmospheric moisture reached the southern Negev Desert leading to deposition of soluble salts and dust deposited in the soils. The combination of long-term hyperaridity, scarcity of vegetation and lack of bioturbation, salts cementation, dust accumulation and tight desert pavement cover, has protected the surfaces from erosion forming one of the most remarkably stable landscapes on Earth, a landscape that essentially has not eroded, but accumulated salt and dust for more than 106 yr.

Original languageEnglish
Pages (from-to)312-323
Number of pages12
JournalQuaternary Science Reviews
Issue number3-4
StatePublished - Feb 2011
Externally publishedYes


The research reported here was supported by the United States-Israel Binational Science Foundation grant 2006-221 and the U.S. Army Research Office grant ( DAAD19-03-1-0159 ). PSD analyses were conducted by M. Ben-Israel and R. Krasilshikov. We thank Bat-Sheva Cohen for map drawing and Y. Rephael, R. Madmon, and Y. Mizrachi for field assistance. We thank the anonymous reviewer, and Claude Hiller-Marcel, editor of Quaternary Science Reviews, who significantly improved this paper.

FundersFunder number
Army Research OfficeDAAD19-03-1-0159
United States-Israel Binational Science Foundation2006-221


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