79-1 Arid to hyperarid environmental transition of the southern Levant deserts and massive dust influx recorded by early Pleistocene Aridisols

Session: Soil, Dust, and Everything in Between: Current, Quaternary and Earlier Geological Processes and Records

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Abstract:

The time of establishing current arid or hyper-arid deserts conditions remains a fundamental question in Earth history. Welded, calcic-gypsic-salic Reg soils developed on flat ca. 2-million-years old alluvial surfaces, dated by cosmogenic isotope exposure ages of desert pavement in the Negev, indicate very long geomorphic stability under extremely dry conditions. A short interval during their initial stage of development, sometimes between 1-2 Ma, these landscape-stable cumulative soils were characterized by stage III carbonate horizon morphology . This is the only interval with calcic soil horizons forming on stable abandoned alluvial surfaces in the southern Negev, indicate presence of vegetation. Gypsic-salic soil horizons and the total lack of calcic horizons in surfaces ≤1 Ma indicate a transition into hyperarid environment and no vegetation, similar to current conditions. Later phases were controlled by dust accumulation. The moderately-developed earlier calcic horizon (stages II-III) over a long time interval (10⁵-10⁶ years) indicates an environment that does not support continuous development but only occasional calcic soil formation. The very low δ¹⁸O and relatively high δ¹³C values of these 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 and growth of sparse vegetation allowing pedogenic carbonate accumulation. At ∼1 Ma, these rare storms and localized slightly wetter soil conditions ceased and moisture rarely reached the southern Negev as today. The combination of long-term hyperaridity, scarcity of vegetation, salts deposition, dust accumulation, and the total lack of bioturbation, and tight desert pavement, 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 1-2 10⁶ yrs.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7997

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