Soils of the Judean Hills and Foothills

Mosaic of Soils

Point in time: 23 million years

Text by Dr. Rivka Amit

The Judea region is generally divided into two sub-regions: the Judean Hills and the Judean Foothills, each characterized by different geological attributes.

The Judean Hills rise up to approximately 1000 meters above sea level, between the Mediterranean coast and the Dead Sea. They are mostly composed of marine carbonate rocks (dolomite, limestone and marl), flanked by less-durable units (mostly chalk and marl).

The Judean Hills are part of the central mountain ridge of the Eastern Mediterranean. The topography of the ridge follows a fold structure, which is composed of short asymmetrical folds. These asymmetrical folds are superimposed on a structural arch, which developed as a response to the subsidence of the Dead Sea Rift since the late Miocene–Pliocene (~ 5.3–2.6 million years ago).

The western flank of the central part of the ridge, also known as the Judean Foothills, was uplifted in few pulses throughout the Neogene (~ 23–5.3 million years ago) and early Pleistocene (5.3–2.6 million years ago). Since the early to mid-Pleistocene, an uplift of ~100 m was followed by tectonic quiescence and base-level stability.

The Judean Hills were formed by limestone and dolomite formations intercalated with marly units and its geological structure results in step-like slopes and springs. In contrast, the Judean Foothills are composed of soft chalk and marl, resulting in gentle and rounded morphology of about 200–400 m height, separated by wide valleys.

The soils of the region developed under humid to sub-humid Mediterranean climate on a variety of marine carbonate rocks, which follow steep, undulating and terraced morphology.

Two soil types dominate this region: terra rossa and rendzina. The terra rossa soil, which develops on hard limestone or dolomite, covers the vast majority of the Judean Hills. Rendzina soils are more commonly found in the Judean Foothills, as they are typically formed on chalk and marl. Brown Rendzina soils are found on hard chalk or Nari crusts (calcrete) that cover soft chalk.

Terra rossa soil is usually shallow with large carbonate rock outcrops forming discontinuity of the soil cover. Thus, the soil tends to develop and accumulate between patches of exposed bedrock (this phenomenon is quite prominent within the Judean Hills, where exposed rock outcrops can be seen in many different parcels). As a result, terra rossa soils differ in many of their morphological aspects. Colors may exhibit various nuances between red and brown. Soil depth ranges from very shallow to moderately deep along solution cracks and crevices in the rock, and the deeper horizons may exhibit signs of clay accumulation and reduced permeability. None to very low content of secondary pedogenic calcium carbonate (0-5%).

Clay and silt dominate the particle size distribution of the terra rossa and range between ~40 and 60% each, fine sand is about 10%, and coarse sand is present in very minor amounts. The high amount of quartz silt in the terra rossa is allochtonic. Quartz silt found in the Judea originates in local dust influx (Negev loess), along with clay and fine silt derived from distal dust sources such as the Sahara and Arabian deserts.

The Rendzina soil group occurs on porous soft calcareous sediments (mainly Senonian chalk and Cenomanian marls). Rendzina soils are common in landscapes characterized by rounded hills and slight to moderate slopes separated by wide valleys (such as in the Judean Foothills). In the Judean Hills, rendzina occurs in association with terra rossa following lithological variations. The common characteristics of the rendzina soils include high CaCO₃ (calcium carbonate) content, limited depth, and AC or AR type profiles. Texture differences within the profile are negligible and the Bt horizon is therefore absent. As it develops on soft chalk, Rendzina soil tends to have pale color, moderate clay content, and high carbonate content. Rendzina formed on marl tends to be grayish-brown in color. Texture is silty loam to clay loam on chalk derived soils, and loam to clay on marl derived soils. Brown rendzina develops on calcareous rocks of moderate hardness and porosity, such as hard flint bearing Eocene chalk, and moderate to hard Nari (calcrete) covering the Senonian and Eocene soft chalk. Frequently, the calcrete disintegrates and the soft chalk underneath is exposed, giving rise to pale rendzina.

Residual soils covering the slope toes and the wadi beds are common in this region – various types of cumulative soils such as colluvial and alluvial soils were developed in the depressions and valleys. These soils are composed of eroded terra rossa and rendzina soils, their texture is clay, silt, and loam. These soils can be stony with rocks and gravel derived from the eroded soils and from the slopes. 

Another characteristic feature of the Judean Hills soils is their association not only with specific rock types, but also with each other. Rapid transitions from one exposed rock type to another are very frequent and result in a close association of the various soil types. While relatively extended areas of terra rossa soils are not uncommon, (pale and brown) rendzina soils are only rarely continuously dominant over large areas and more commonly form an intimately mixed soil mosaic. In addition, slight changes in the physical character of the carbonate bedrock produce deviations from the usual characteristics of the soils formed. Intercalations of softer calcareous sediments within the limestone or dolomite can also produce somewhat different soils and even perched springs that emerge along the hill slopes of the Judean Hills, discharging mostly above the clay-rich aquiclude. 

Characterized by this mosaic of soils and a steep to moderate topography, the terroir of the Judean Hills serves as a basis for producing high quality wine in this region.

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