-
DEPOSITIONAL ENVIRONMENT OF HOLOCENE COOL WATERTRAVERTINES IN THE VALLEY OF BAŞKÖY
- Leuven University Press
- Chapter
- Additional Information
211 DEPOSITIONAL ENVIRONMENT OF HOLOCENE COOL WATER TRAVERTINES IN THE VALLEY OF BAŞKÖY Patrick DEGRYSE, Philippe MUCHEZ, Willy VIAENE† , Yves QUINIF and Marc WAELKENS petrographical investigation. Within the field, three major types of travertine have been distinguished: phytoherm framestone (Figure 1A), finely laminated (Figure 1B) and detrital travertine. The phytoherm framestone consists of coarse-grained radial and concentric calcites encrusting plants. The finely laminated travertine is composed of thin calcite layers, in which different morphologies are present . Detrital travertine is characterized by rounded sand to cobble sized carbonates. In addition to the mapping of the different travertine types on a regional scale, three sections have been studied. 4. PETROGRAPHY 4.1. Description and interpretation Microscopically, the phytoherm framestone (Figure 1A) consists of equidimensional to acicular calcite crystals. The crystals grew perpendicular on a plant stem. The detrital travertine deposits are built up by reworked fragments of earlier deposited travertine and siliciclastics. Sometimes the relic structures of the older, original deposits can be seen. In the finely laminated travertine, several biological features can be observed. Firstly, the calcites may show a three-dimensional network of spheres composed of a micritic nucleus surrounded by irregular concentric laminae (Figure 1B). This structure is identical to the 3D network of bacterial shrubs described by Chafetz and Folk (1984) and Guo et al. (1996). Since the growth period of these bacteria is dominantly from spring until summer, these calcites are likely to have been precipitated during these seasons. However, they can also grow in zones of slow flow throughout the year. Secondly, acicular sparitic calcite crystals radiating from a central line may build up mm- to cm-thick layers (Figure 1C). This structure closely resembles that of colonies of Rivulariacea (Caudwell, 1983; Obenlüneschloβ, 1991). Gastropods belonging to the families Succineidea and Zonitidae, occur within the mm to cm-thick layers. Thirdly, calcite encrusting half circular to oval pores (Figure 1D) consists of three layers. The latter are composed of a white microsparitic layer of 5µm, a brown micritic layer of 10µm and a layer of acicular crystals in which there are remains of tubes. These structures are biomediated 1. INTRODUCTION The study of cool water travertines in the village of Başköy, located some 5 km to the west of Sagalassos, forms part of an interdisciplinary research carried out at the territory of the archaeological site of Sagalassos. This site was occupied from prehistoric times until the 7th century A.D. The aim of this interdisciplinary study is to reconstruct the physical, biological and socio-economical environment of the ancient city (Waelkens et al., 1999). Within the present paper, a reconstruction of the environment in the valley of Başköy has been made based on travertine deposits. 2. MODERN ENVIRONMENT 2.1. Geomorphology and geology The valley of Başköy is surrounded to the north, west and south by the slopes of the Taurus Mountains and opens towards the east to the valley of Ağlasun. The flanks of this valley consist of Tertiary allochthonous nappes, built up by limestone and ophiolites and of Tertiary flysch deposits. These nappes are thrusted over the allochthonous Mesozoic limestone massif of the Bey Dağları (Robertson, 1993). The limestone acts as an aquifer for travertine depositing waters in the area. In the valley itself we find alluvial, lake and travertine deposits of Quaternary age. 2.2. Climate The area studied is characterized by a relatively short dry, hot period in summer, and a long wet, cold period from autumn until spring. Most of the precipitation falls as snow in December and January. The area has an oro-mediterranean climate (Poesen et al., 1995). The valley of Başköy, where the travertines are situated, lies at an altitude between 1000 and 1200m a.s.l. 3. FIELD INVESTIGATION A field study was carried out to map different types of travertine deposits and to collect samples for a further SAGALASSOS_f11_209-214.indd 211 SAGALASSOS_f11_209-214.indd 211 9/30/2008 2:44:22 PM 9/30/2008 2:44:22 PM 212 by algae colonizing on larvae of Chironomida, encrusting themselves with calcite, as described by Thienemann (1954) and Golubic et al. (1993). The larvae of Chironimus only live in April and May in this region (Thienemann, 1954). The finely laminated travertine is also composed of white to brown, compact layers of acicular calcite crystals with micritic particles enclosed in and between them (Figure 1E). The acicular calcite crystals are interpreted...