Geological Survey: July 12-19, 2006
Natural building stones in the monumental structures of Sagalassos include marble, limestone, conglomerate, breccias, travertine, granite, porphyry, sandstone, and siltstone of different qualities. The provenance of most of the building stones is related to local lithological units, both in the immediate area of the city and on its territory (see 2005 Surveys, Geological).
The purpose of this year's quarry survey, performed by Patrick Degryse (K. U. Leuven), Tom Heldal (Norwegian Geological Survey), and Elizabeth Bloxam (University College London) was to relate the quarrying of local stone in the territory to building projects in Sagalassos. This study is integrated, as a case study, into the Quarryscapes Project (Conservation of ancient stone quarry landscapes in the Eastern Mediterranean, an EU sixth framework program project). Important research goals included characterizing the quarries according to their significance and their role in the development of the city, recognizing quarry-related features, investigating the geological features of the individual quarries, and questioning the relationship between volumes that were quarried and volumes that were used.
The quarries around Sagalassos can be grouped according to their location (local or regional), their geology (provenance), morphology (topographical features) and production evidence (quarry marks, worked objects, spoil heaps etc.) Regional quarries include quarries located up to 10 kilometers away from the city centre. One quarry was studied in detail during this survey. The Sarikaya quarry is located 3-4 kilometers southwest of Sagalassos, near the village of Yesilbasköy (Basköy) in the lower part of a steep cliff (see Suburban survey: July 10-13, 2006).
The Sarikaya quarry shows outcrops of white-beige limestone and red nodular limestone. The stone type quarried is unique to the Sarikaya quarry, as it can be microscopically classified as radiolarian mudstone. This type of stone seems to have been used only in late Hellenistic buildings (Bouleuterion, Doric Temple) at Sagalassos. Radiolarian mudstones are not found in quarries elsewhere in the territory and were not used in buildings from the Julio-Claudian period onwards. This indicates that the quarry may have been one of the main suppliers of building stones during the late Hellenistic period. Sagalassos red slipware sherds found in front of the main quarry face date from the early Imperial period and may constitute a terminus ante quem for the exploitation of the quarry.
The survey has further shown that the quarry is a localized, limited quarry. In the immediate vicinity, no further quarrying traces can be observed. Stone is extracted using natural fractures, quarry trenches, and wedges. Many spoil heaps, caused by the extraction and roughing out of the blocks, can be observed in front of the quarry face. The minimal extracted volume of the quarry must have been around 2,000 meters2 of stone, enough to provide stone for several large building projects. The quarry was exhausted for good stone, as can be seen from the back wall. The back end of the quarrying area is formed by a fault plane, composed of a heavily brecciated stone, unsuitable for extraction. The usable stone was likely transported to Sagalassos along a path following the topography from the quarry, leading over a mountain pass north of the modern village of Yesilbasköy, and continuing straight into Sagalassos. Possible stretches of this track along the slope were mapped.
This week (July 16-19), the quarry survey was continued in the city of Sagalassos itself, to relate the quarrying of local stone near the monumental center to building projects in Sagalassos. On-site quarries include limestone and limestone breccia quarries predominantly located within one kilometer from the city center.
An estimate of the amount of stone (ashlars) used in monumental architecture was made on the basis of plans for a number of buildings and streets. The amount of ashlars used is rather limited. Many structures in the city only have a facade of ashlars, and were for the most part constructed with brick or Roman concrete. One could speculate that the amount of ashlars needed for all of monumental Sagalassos would not exceed 10,000 meters2 of ashlars, but is likely to be as low as 5,000 meters2. Yet, this is no small amount for what was a middle-sized city in the Imperial period, when most ashlar buildings at Sagalassos were constructed. By the second century A. D., the peak of building activities in this city and elsewhere in the Empire, mortared rubble and brick layers had replaced ashlars as the most frequently used building material. However, the rich amounts of Pisidian limestone available ensured its further use until the early third century A. D.
Also, estimates of the volumes of stone used for sarcophagi and burial practices were made. The stone volume quarried for this purpose ranges between 500 and 1,500 meters_. The volume of stone extracted for burials would therefore constitute a significant percentage of stone extraction.
The identified quarries have been mapped in detail using GPS and satellite photos The limestone outcrops in and around the city display considerable variations in quality, both regarding use (durability) and quarrying (block potential). The former is important for preservation of the quarries; particularly, brecciated and nodular limestone varieties are severely weathered and extraction marks are usually strongly deteriorated. Block potential is strongly related to the degree of fracturing in the limestone deposits.
In general, less fractured varieties display abundant extraction marks, such as carved walls and channels, while such evidence is rare in fractured limestone. This is due to the extraction method typically used in these quarries, of removing primary blocks bordered by natural fracture surfaces. Particularly interesting is one site where there is evidence of wedging of stone blocks parallel to natural fracture planes. Conversely, the presence of large heaps of limestone chips and fragments, interpreted as quarry spoil heaps, suggest that significant quarrying and working of stone took place in this area, and that the quarries were practically exhausted.
The keyword for the quarrying of limestone in the city area seems to be proximity; in the immediate vicinity of important stone consuming activities, such as construction or funerary work, there are quarries whose size fits the volume of stone needed. The lack of systematic channeling in the quarries likely relates to the stone quality; the abundance of natural fractures in the limestone deposits forced the quarrymen to follow the natural features.