10:15 AM - 10:30 AM
[HQR05-06] Paleoenvironment of Anatolia based on Eski Acigol drilling
Keywords:Eski Acigol, Central Anatolia, Late Holocene, Paleoenvironmental changes
Eski Acigol was a crater lake located in the central part of Central Anatolia and dried up in 1970’s due to a heavy agricultural use of water. The lake is known to continuously accumulate fine-grained detrital sediments for over the last 15,000 years. From August 23 to 25, 2023, we conducted drilling of 4 holes at the central part of the lake using a portable percussion corer, drilled to the depth of ca. 5.5 m, and continuously recovered the sediments down to ca. 4.6 m (ca. 5000 years BP).
The recovered sediments are dominantly composed of fine-grained clastic material with various amounts of calcareous materials (microfossils such as ostracodes’ shells and inorganic carbonate precipitates) and silica (biogenic silica such as diatoms and sponge spicules, and inorganic opal precipitates). Decimeter-scale alternations of dark- and light-colored layers developed in the stratigraphic interval of ca. 2.4 to 4.3 m depth (corresponding to ca. 5,000 to 3,000 years BP) and repeated 6 times. This means the average periodicity of ca. 400 years for the dark and light alteration. Centimeter-scale color banding of reddish, yellowish, and grayish colors develops especially in the light-colored layers, suggesting the presence of decadal-scale paleoenvironmental variation.
We conducted preliminary observation of grain components under the petrographic microscope, and measurements of color, mineral composition by XRD, chemical composition by WD-XRF and XRF core scanner (ITRAX) to examine the cause(s) of the centennial-scale changes manifested as dark and light cycles. The results suggest that the decimeter-scale alternations of dark- and light layers represent changes in lake level (and possibly wet and dry cycles). The cause(s) of the decadal-scale changes (centimeter-scale color bandings) is the future problem to be explored.
The time interval of ca. 5,000 to 3,000 years ago where ca. 400 year dry-wet cycles are recognized, approximately corresponds to the interval (ca. 4,500 to 2,700 years ago) where 4 fire event layers are recognized. It is possible that there fire event layers are associated with ca. 400 year dry-wet cycles. Higher precision and resolution age models are necessary for both records in the time interval between ca. 5,000 and 3,000 years ago in order to clarify the association between the fire events and dry events.
The recovered sediments are dominantly composed of fine-grained clastic material with various amounts of calcareous materials (microfossils such as ostracodes’ shells and inorganic carbonate precipitates) and silica (biogenic silica such as diatoms and sponge spicules, and inorganic opal precipitates). Decimeter-scale alternations of dark- and light-colored layers developed in the stratigraphic interval of ca. 2.4 to 4.3 m depth (corresponding to ca. 5,000 to 3,000 years BP) and repeated 6 times. This means the average periodicity of ca. 400 years for the dark and light alteration. Centimeter-scale color banding of reddish, yellowish, and grayish colors develops especially in the light-colored layers, suggesting the presence of decadal-scale paleoenvironmental variation.
We conducted preliminary observation of grain components under the petrographic microscope, and measurements of color, mineral composition by XRD, chemical composition by WD-XRF and XRF core scanner (ITRAX) to examine the cause(s) of the centennial-scale changes manifested as dark and light cycles. The results suggest that the decimeter-scale alternations of dark- and light layers represent changes in lake level (and possibly wet and dry cycles). The cause(s) of the decadal-scale changes (centimeter-scale color bandings) is the future problem to be explored.
The time interval of ca. 5,000 to 3,000 years ago where ca. 400 year dry-wet cycles are recognized, approximately corresponds to the interval (ca. 4,500 to 2,700 years ago) where 4 fire event layers are recognized. It is possible that there fire event layers are associated with ca. 400 year dry-wet cycles. Higher precision and resolution age models are necessary for both records in the time interval between ca. 5,000 and 3,000 years ago in order to clarify the association between the fire events and dry events.