Geologic Materials
One of the major contributions by geoarchaeologists (earth scientists working in archaeology) is to identify the geological materials at an archaeological site and in the general study area. The geology of a site has an important function in providing the parent materials for soil formation and in supplying natural consolidated materials for building stone and many other uses. On the Karak Plateau, for example, many bowls and implements were made of volcanic rock (basalt) that occurs in many localities of the study area.
The Karak Plateau has a variety of geologic formations including limestone, basalt, and unconsolidated wind-blown silts (loess). In numerous localities around al- Mudaybi’, the most pronounced rock type is the Pleistocene basalt. There are at least four distinct basalt flows on the Karak Plateau and most are believed to have been deposited during the Pleistocene (last 2 million years).
Weathering of basalt is noted on several exposed road cuts and shows the disintegration of basalt usually as a weathering rind around exposed boulders. Basalt has a special interest in this study as a result of its use as a common building stone and for grinding bowls, in addition to its location at al-Mudaybi’ at the base of the archaeological excavations.
Limestone is the dominant rock type on the Karak Plateau and provided much of the building stone for construction of forts and towers. Limestone outcrops are common on the steeply sloping landscapes and valley floors where erosion has been severe as south of Mahai, illustrates the outcroppings on these landscapes. The many limestone outcrops and shallow soils occurring on significant amount of landscapes on the Karak Plateau limit agricultural production in these areas. This is the reason that loess is of such importance as a parent material in many regions of the study area.
The following photo illustrates the relationship of the thicker loess deposits on the lee slope and the potential agricultural value of loess compared to the upper slope where shallow areas of soils occur with numerous limestone outcrops. Unfortunately, however, loess is one of the erosive types of soil and can result in areas of deep gullies and thin soils. Loess is the parent material for the more productive areas on the Karak Plateau and especially when combined with more abundant rainfall. Loess was deposited in several sequences on the study area.
This road cut east of Karak illustrates thick loess deposits with three paleosols in the sequence. Deposition probably started in the Pleistocene with secondary deposition occurring even today in the region.
