Paleogeography of the Tarsus Plain and Geoarchaeology of Gözlükule Mound in Light of a Multi-Proxy Analysis
Rifat İlhan, Aylin Karadaş, Sabah Kırallı, Serdar Vardar, Ertuğ ÖnerGözlükule Mound is located in the northern Tarsus Plain . This study aims to reconstruct the paleoenvironment of Gözlükule Mound and the paleogeographic development of the Tarsus Plain. Core sediments taken from 19 drillings made between 2001-2002 are used to reveal the effects of natural environmental changes, with granulometric analyses, elemental analyses, and paleontological analyses being done for this purpose. In light of these analyses, the study interprets the natural environmental changes to the Tarsus Plain and the surroundings of Gözlükule Mound that occurred in the Holocene. In order to connect these developments to a certain chronology, a total of five radiocarbon-14 analyses were made with the support of Ege University Scientific Research Project Nos. SHD-2021-22452 and SYL-2020-22305. The paleontological, sedimentological, and elemental analyses, as well as the dating results of the sediment samples, were reevaluated, with the paleogeographic development of the region being revealed in accordance with the new data.
Çoklu Analiz Yöntemlerinin Işığında Tarsus (Berdan) Ovasının Paleocoğrafyası ve Gözlükule Höyüğünün Jeoarkeolojisi
Rifat İlhan, Aylin Karadaş, Sabah Kırallı, Serdar Vardar, Ertuğ ÖnerGözlükule Höyüğü, günümüzdeki Tarsus (Berdan) Ovası’nın kuzey kenarında bulunmaktadır. Bu çalışmada, Tarsus Ovası’nın paleocoğrafik gelişimini ve bölgede yer alan Gözlükule Höyüğü’nün doğal çevre değişimlerinden nasıl etkilendiğini ortaya koymak amacıyla, 2001 ve 2002 yıllarında yörede yapılmış olan 19 adet delgi sondaja ait sedimanlar yeni analizler ışığında değerlendirilmiştir. Sedimanlar, granülometrik, element özellikleri ve paleontolojik açıdan analiz edilmiştir. Bu analizlerin sonuçlarına göre Tarsus Ovası ile Gözlükule Höyüğü çevresinin Holosen’deki doğal çevre değişmeleri yorumlanmıştır. Bu gelişmelerin belli bir kronolojiye bağlanabilmesi için Ege Üniversitesi Bilimsel Araştırma Projeleri SHD - 2021 - 22452 ve SYL - 2020 - 22305 numaralı iki proje desteği ile toplam 5 adet RC14 analizi yaptırılmıştır. Sediman örnekleri paleontolojik, sedimantolojik, element analizleri ve tarihleme sonuçları birlikte değerlendirilerek yeni verilere göre yörenin paleocoğrafik gelişimi ortaya konmuştur.
Tarsus Plain is a part of the Çukurova Deltas Complex and is located in a region bounded by the Mediterranean Sea to the south, the Bolkar Mountains to the north and northwest, and the Misis Mountains to the east. With a historical past dating back to 7,000 BC, Cilicia was one of the most important settlements of the region in the ancient period, and Gözlükule Mound is located on the northern edge of the Tarsus Plain. In order to reveal the paleogeographic development of the Tarsus Plain and how the Gözlükule Mound in the region was affected by natural environmental changes, the study reevaluates within its scope sediment samples that had been taken from core drillings in the region.
A laser-diffraction grain-size analysis was carried out over 300 sediment samples taken from different depths, as well as an elemental analysis using the x-ray fluorescence (XRF) method on 145 sediment samples. In addition, a carbon-nitrogen-sulfur (CNS) analysis, total organic carbon (TOC) and total inorganic carbon (TIC) analysis, and paleontological analysis were also conducted on 150 sediment samples. A total of five radiocarbon-14 (RC-14) analyses were conducted with the support of Ege University Scientific Research Project Nos. SHD-2021-22452 and SYL-2020-22305.
To determine the delta development in the Tarsus Plain as well as in the old lagoon and marsh areas in the region, XRF, CNS, and carbon-to-nitrogen (C/N ratio) elemental analyses were performed on 150 sediment samples. In addition to the calcium-to-potassium (Ca/K) ratio in the sediment content, the high TIC ratio explains the dominance of marine sediments. The high zirconium-to-rubidium (Zr/Rb) ratio indicates the accumulation of sandy material. However, the sediment samples that were determined to be marine were also seen to have high levels of titanium (Ti), manganese (Mn), and strontium (Sr). The environment is explained to have been lagoonal through the high chlorine (Cl), sulfur (S), and calcium (Ca) ratios found in the sediment. The analysis results determined that coastal dunes had provided the formation of the lagoon and reflect the transition. Accordingly, the Ca/K, Cl, S, and TOC ratios decreased, The Si and TIC ratios increased due to the formation of dunes. A high K ratio is also identified in flood plain sediments.
The granulometric analysis of 300 samples from drilling sediments graded the grain size poorly or very poorly at depths reflecting the flood plain sediments. However, the average grain size was seen to range between 3-10 microns. Due to the flooding present in river dynamics, average grain size reaches up to 39 microns at some levels. At the depths determined as the old river bed, the average particle size distribution reached up to 800 microns, with the sediment structure showing very poor grading. These levels contain coarse grains as well as all sizes of sand, silt, and clay. At levels reflecting the marine environment, the average grain size of the sediment is 50 microns, with the sediment being coarse, silty, and poorly graded. In the lagoon environment, this took on a very fine sandy structure with an average grain size of 200 microns.
The fossils in the sediment samples taken from the boreholes made significant contributions to the research in terms of their habitats. The macro- and micro-fossils found in the sediment samples taken from the boreholes in the Tarsus Plain and around the Gözlükule Mound prove the environmental characteristics that were interpreted from the sedimentological point of view. The changes in the coastline in the Holocene in particular provided indicators for determining whether the Gözlükule Mound and the city of Tarsus had been coastal settlements during these periods; whether the Rhegma (Rhegmoi) Lagoon, whose existence appears in historical narratives, had also existed as the plain developed, and whether a harbor town called Aulai had also existed.
The natural environment around the Gözlükule Mound has changed considerably from the Neolithic era to the present. This change occurred mostly in the alluvial area and along the shoreline. The Tarsus Plain and Gözlükule Mound were never located on the coast, nor did the sea penetrate inland this far. The sea had risen rapidly and transgressed around Tarsus. It must have advanced on the old plain surface, which had been shaped under terrestrial conditions compared to the pre-Holocene floor level, and is now located under today’s alluvium area. According to the results on the drillings, the sea had penetrated up to 5 km south of the Gözlükule Mound during this period.
Over the course of time, the settlement that started in Gözlükule Mound expanded to the present city area. Meanwhile, a lagoon began to develop in the south, and the port city of Tarsus, called Rhegma as well as Aulai, was established on the shore of this lagoon. In this period, Tarsus became the most important city of the region with its geographical location and inner harbor. As the Rhegma lagoon filled with alluvium and turned into a lake and then into a large swamp, Tarsus being 15-16 km away from the coast ceased to be a city connected to the sea.
According to the results of the multiple analysis methods that were carried out, the coastline had intruded to the north in the direction of Tarsus and Gözlükule Mound via transgression in the Early Holocene; it moved towards the plain again in the Middle and Late Holocene alongside the alluvia carried by the Tarsus Stream and the Seyhan and Ceyhan rivers in the region. Based on the processes that developed in the Middle and Late Holocene, a lagoon (Rhegma) was formed to the south of Gözlükule Mound. With the continued accumulation, the lagoon environment gradually turned into a lake before then becoming a wetland in the delta-flood plain. Wetlands in the form of swamps remain as current traces of these processes over the plain except where they were dried by drainage works. Today, the Karabucak swamp in the south Tarsus Plain is the last remnant of these environments.
