2:30 PM - 2:45 PM
[HQR05-16] Varved sediments of the Nar Lake, Central Anatolia: their utility for high-resolution paleoenvironmental reconstruction
Keywords:Central Anatolia, Nar Lake, Varved sediments, Flood layer
Institute for Geo-Cosmology of Chiba Institute of Technology (CIT) has been conducting archaeological excavation in Urfa region, southeastern Anatolia to study the emergence of civilization approximately at 12,000 years BP and observation and sampling in Kaman-Kalehöyük archaeological site in central Anatolia to study the initiation of iron manufacturing technology and emergence of Hittite empire under the strong support of Japanese Institute of Anatolian Archaeology (JIAA). In order to understand how paleoclimatic/paleoenvironmental changes affected switching points of civilization and technological revolution, joint project to reconstruct paleoclimatic/paleoenvironmental changes in Anatolia during the Holocene is organized between consortium of Japanese institutions (CIT, Shinshu University, Shimane University), General Directorate of Mineral Research and Exploration (MTA) at Ankara, and JIAA at Kaman last year.
Varved sediment is an annually laminated sediment characterized by alternation of two types of laminae with different composition and/or color. Consequently, it has an annual or even seasonal time resolution. The Nar Lake, a crater lake in Central Anatolia, is known for its varved sediment characterized by couplets of lighter-colored calcareous clay lamina and darker-colored silt lamina that have been accumulating nearly continuously for more than 12,000 years. Paleoenvironmental reconstructions have been conducted using stable isotopes of carbonates and several types of microfossils. However, these previous works have following problems, i) annual origin of the lamina couplet is not well-proved, ii) origin and nature of the lamina couplet are not well-described, iii) their age model is not well-presented, well-constrained, and not testable by others because detailed data are not presented, and iv) comprehensive study on paleoclimatic/paleoenvironmental reconstruction and impact of such changes on the switching points of civilization and technological revolution have not been conducted. To solve these problems, we conducted preliminary coring of the Nar Lake sediments and retrieved a 1.2 m long piston core from the eastern central part and a 16 cm long Limnos core from the northeastern part of the lake, and we conducted feasibility study to observe and analyze these core samples.
We found lighter-colored lamina is composed of either needle-shaped aragonite or rhombohedral calcite micro-crystals which were probably precipitated and settled down within the water column during dry season in summer, whereas darker-colored lamina is dominantly composed of coarse silt size siliciclastic grains that were probably derived from soils formed on the alluvial fan on the southern side of the lake and fine siliciclastic materials delivered from small rivers drained from the south. We also found that dark grey very fine siliciclastic sand layers, which are frequently intercalated in the varved clay sediments, were derived from the cliff exposed on the inner wall of southern part of the crater rim and delivered through small rivers as turbid water at the time of heavy rain.
In the presentation, we will introduce the results of preliminary analyses and demonstrate the potential of the Nar Lake varved sediments to become an excellent high-resolution and precision standard time scale in Anatolia covering the entire Holocene. We will also show what kind of paleoclimatic/paleoenvironmental information we can extract from the sediments.
Varved sediment is an annually laminated sediment characterized by alternation of two types of laminae with different composition and/or color. Consequently, it has an annual or even seasonal time resolution. The Nar Lake, a crater lake in Central Anatolia, is known for its varved sediment characterized by couplets of lighter-colored calcareous clay lamina and darker-colored silt lamina that have been accumulating nearly continuously for more than 12,000 years. Paleoenvironmental reconstructions have been conducted using stable isotopes of carbonates and several types of microfossils. However, these previous works have following problems, i) annual origin of the lamina couplet is not well-proved, ii) origin and nature of the lamina couplet are not well-described, iii) their age model is not well-presented, well-constrained, and not testable by others because detailed data are not presented, and iv) comprehensive study on paleoclimatic/paleoenvironmental reconstruction and impact of such changes on the switching points of civilization and technological revolution have not been conducted. To solve these problems, we conducted preliminary coring of the Nar Lake sediments and retrieved a 1.2 m long piston core from the eastern central part and a 16 cm long Limnos core from the northeastern part of the lake, and we conducted feasibility study to observe and analyze these core samples.
We found lighter-colored lamina is composed of either needle-shaped aragonite or rhombohedral calcite micro-crystals which were probably precipitated and settled down within the water column during dry season in summer, whereas darker-colored lamina is dominantly composed of coarse silt size siliciclastic grains that were probably derived from soils formed on the alluvial fan on the southern side of the lake and fine siliciclastic materials delivered from small rivers drained from the south. We also found that dark grey very fine siliciclastic sand layers, which are frequently intercalated in the varved clay sediments, were derived from the cliff exposed on the inner wall of southern part of the crater rim and delivered through small rivers as turbid water at the time of heavy rain.
In the presentation, we will introduce the results of preliminary analyses and demonstrate the potential of the Nar Lake varved sediments to become an excellent high-resolution and precision standard time scale in Anatolia covering the entire Holocene. We will also show what kind of paleoclimatic/paleoenvironmental information we can extract from the sediments.