Debris flows, soil creep and heavy rains in the Wadi Queilbeh, northern Jordan

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Lucke, Bernhard ; Schmidt, Christoph:
Debris flows, soil creep and heavy rains in the Wadi Queilbeh, northern Jordan.
In: Zeitschrift für Geomorphologie : Supplementary Issues. Bd. 61 (April 2017) Heft 1 . - S. 159-201.
ISSN 0372-8854
DOI: https://doi.org/10.1127/zfg_suppl/2016/0340

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Abstract

We conducted a detailed study of a valley fill in Wadi Queilbeh near the ancient site Abila of the Decapolis in northern Jordan to check whether the fill can serve as environmental archive of landscape changes in the region. Apart from several profiles along the course of the valley and its bordering slopes, one profile was studied in the neighboring Wadi Hubras. A consistent stratigraphy of regional sedimentation phases emerged, indicating that the valleys had been subject to soil formation during the Late Pleistocene. Fluvial erosion might then have eroded part of the paleosols, and deposited varying amounts of matrix- supported gravels and stones, pointing to repeated floods. Well-sorted, well-rounded gravels of smaller channels within these sediments are interpreted as indications of perennial creeks, which were present in Wadi Queilbeh from around 7000 b2k (b2k = before the year 2000) until at least 1800 b2k throughout the valley. Apart from a possible phase of increased sedimentation during the Iron Age, the valley appears stable until the Late Byzantine period, and probably hosted a small floodplain in its upper section. However, sometime around 1400–1300 b2k and 700–500 b2k, massive debris flows were deposited. As well, an ancient cemetery at the upper slope was buried by viscous, plastic soil creep of Terra rossa from the limestone plateau that sealed but did not fill entrances to chamber graves. This points to the occurrence of prolonged heavy rainfalls as most important agents of landscape changes, possibly in the context of the global climatic events triggered by volcanism. Land use seems to have played no major role for the formation of the valley fill. After these events, the landscape returned to stability, although the perennial creek disappeared in the upper part of the valley, possibly indicating more arid conditions than during antiquity.