This study aimed to determine the paleoenvironmental reconstruction of the Upper Triassic–Lower Jurassic Kızılören carbonates (limestone and dolostone) in the Kütahya–Bolkardağ Belt. Previous researchers have not studied these carbonates at this level of detail or from this perspective. The importance of the Late Triassic and Early Jurassic time interval lies in the dominance of hot, semiarid to arid climatic conditions in the Tethys region and the occurrence of two short, relatively humid peaks in the Middle–Late Carnian period, known as the Late Triassic Carnian Precipitation Event, followed by arid conditions, and the lack of any evidence of glacial activity in the Late Triassic, presenting this as a unique period in the Phanerozoic history of the Earth; the fact that the Early Jurassic period included extreme climate fluctuations along with glacial periods occurring within the general greenhouse conditions range, and significant events, such as major events in the Mid-Atlantic and Karoo–Ferrar magmatic regions of this period and the gradual disintegration of the Pangea supercontinent, have led us to study the carbonates that developed during this process. The Kızılören carbonates consist of gray to dark gray, medium-thick layered limestone and dolostone. Based on their microfacies, the Kızılören carbonates are classified as wackestone, mudstone, neomorphic wackestone, neomorphic mudstone, neomorphic dolowackestone, neomorphic dolomudstone, neomorphic crystalline dolostone, and crystalline dolostone. In MSS-A, the primary texture was preserved in all samples except for the crystalline dolostone sample A120, which was taken from the uppermost level. In MSS-B, the primary texture was preserved in all samples except for the neomorphic crystalline dolostone sample B1, which was taken from the uppermost level. In MSS-C, the primary texture was preserved in all samples except for the crystalline dolostone sample C87, which was taken from the uppermost level. In determining diagenetic alteration, Mn/Sr, Fe/Sr, Rb/Sr, Mg/Ca, and Sr/Ca element ratios; Fe, Sr, Mg, and Mn element amounts; and ẟ13C and ẟ18O isotope values were used. The Mn/Sr ratios of the Kızılören carbonate samples ranged from 0.33 to 3.22 (average 0.93), indicating insignificant diagenetic alteration. The Fe/Sr ratios in the studied samples ranged from 1.6 to 111 (average 14.1), and alteration was observed in six samples, while insignificant alteration was observed in 14. The Rb/Sr ratios in our samples ranged between 0.00042 and 0.02116 (average 0.00329), and 18 samples were < 0.01 and did not show any alteration, while two samples were > 0.01 and showed a low degree of diagenetic alteration. The Mg/Ca ratios in our samples ranged between 0.0063 and 0.5922 (average 0.3829) with 12 samples were > 0.4 and showed a low degree of diagenetic alteration while eight were < 0.4 and did not show any alteration. The Sr/Ca ratios of the studied samples ranged from 0.000159 to 0.00103 (average: 0.000472), and all samples were < 1, indicating they did not undergo diagenetic alteration. The REE + Y values of the Kızılören carbonate samples normalized to the Post-Archaean Australian Shale (PAAS) indicated that all samples were of marine origin, were not influenced by any hydrothermal input, and that some fell into the modern marine environment. In the δ18O and δ13C isotope diagrams, the Kızılören carbonate samples exhibited effects of climatic and diagenetic alteration, with a primary marine signature. Furthermore, in the δ18O and δ13C isotope graphs, most of the Kızılören carbonate samples were located within the original seawater area and the low rock–water interaction area, while only one sample was located within the high rock–water interaction area. The positive correlation observed between the δ18O and δ13C isotopes in our studied samples indicates both meteoric water–seawater mixing and diagenetic alteration. The negative correlation in the carbonate samples and the positive correlation in the dolostone samples indicate low-grade diagenetic alteration in the limestones and moderate-grade diagenetic alteration in the dolostones. Both the Sr/Ba and Rb/K values (except for two samples indicating a brackish water environment) and the Z values calculated from the δ18O and δ13C isotope values (except for one sample indicating a brackish water environment) indicated that the vast majority of Kızılören carbonate samples were deposited in a marine environment. This situation likely resulted from a river flowing into the sea, forming a short-lived estuarine environment and subsequent carbonate accumulation. Paleoproductivity (Ba/Al, Baxs, P/Ti, P/Al, and Baxs diagrams) was observed at medium–low levels during the Kızılören carbonate deposition process. The CIX and PIX values of the Kızılören Formation carbonates are similar, with some samples (eight samples; < 40) unweathered, some (ten samples; 40–70) weakly weathered, and some (two samples; > 80) severely weathered. To determine the provenance of the detritals observed in the Kızılören carbonates, the La/Sc, Th/Sc, La/Co, Th/Co, Th/Cr, and Th/U element ratios were used. It was determined that the detrital grains in our studied samples were mostly from mafic and, to a lesser extent, felsic sources. According to geochemical data, the Neotethian (Late Triassic-Early Jurassic) Kızılören carbonate layers were deposited in an arid-to-subhumid climate and a shallow marine (carbonate shelf) environment, with relatively low detrital input and oxic-anoxic conditions.

Paleoenvironmental Reconstruction of the Upper Triassic–Lower Jurassic Kızılören Formation Carbonates in Ardıçlı, Konya, Türkiye

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2026年5月25日

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Ali Müjdat Özkan

摘要

This study aimed to determine the paleoenvironmental reconstruction of the Upper Triassic–Lower Jurassic Kızılören carbonates (limestone and dolostone) in the Kütahya–Bolkardağ Belt. Previous researchers have not studied these carbonates at this level of detail or from this perspective. The importance of the Late Triassic and Early Jurassic time interval lies in the dominance of hot, semiarid to arid climatic conditions in the Tethys region and the occurrence of two short, relatively humid peaks in the Middle–Late Carnian period, known as the Late Triassic Carnian Precipitation Event, followed by arid conditions, and the lack of any evidence of glacial activity in the Late Triassic, presenting this as a unique period in the Phanerozoic history of the Earth; the fact that the Early Jurassic period included extreme climate fluctuations along with glacial periods occurring within the general greenhouse conditions range, and significant events, such as major events in the Mid-Atlantic and Karoo–Ferrar magmatic regions of this period and the gradual disintegration of the Pangea supercontinent, have led us to study the carbonates that developed during this process. The Kızılören carbonates consist of gray to dark gray, medium-thick layered limestone and dolostone. Based on their microfacies, the Kızılören carbonates are classified as wackestone, mudstone, neomorphic wackestone, neomorphic mudstone, neomorphic dolowackestone, neomorphic dolomudstone, neomorphic crystalline dolostone, and crystalline dolostone. In MSS-A, the primary texture was preserved in all samples except for the crystalline dolostone sample A120, which was taken from the uppermost level. In MSS-B, the primary texture was preserved in all samples except for the neomorphic crystalline dolostone sample B1, which was taken from the uppermost level. In MSS-C, the primary texture was preserved in all samples except for the crystalline dolostone sample C87, which was taken from the uppermost level. In determining diagenetic alteration, Mn/Sr, Fe/Sr, Rb/Sr, Mg/Ca, and Sr/Ca element ratios; Fe, Sr, Mg, and Mn element amounts; and ẟ¹³C and ẟ¹⁸O isotope values were used. The Mn/Sr ratios of the Kızılören carbonate samples ranged from 0.33 to 3.22 (average 0.93), indicating insignificant diagenetic alteration. The Fe/Sr ratios in the studied samples ranged from 1.6 to 111 (average 14.1), and alteration was observed in six samples, while insignificant alteration was observed in 14. The Rb/Sr ratios in our samples ranged between 0.00042 and 0.02116 (average 0.00329), and 18 samples were < 0.01 and did not show any alteration, while two samples were > 0.01 and showed a low degree of diagenetic alteration. The Mg/Ca ratios in our samples ranged between 0.0063 and 0.5922 (average 0.3829) with 12 samples were > 0.4 and showed a low degree of diagenetic alteration while eight were < 0.4 and did not show any alteration. The Sr/Ca ratios of the studied samples ranged from 0.000159 to 0.00103 (average: 0.000472), and all samples were < 1, indicating they did not undergo diagenetic alteration. The REE + Y values of the Kızılören carbonate samples normalized to the Post-Archaean Australian Shale (PAAS) indicated that all samples were of marine origin, were not influenced by any hydrothermal input, and that some fell into the modern marine environment. In the δ¹⁸O and δ¹³C isotope diagrams, the Kızılören carbonate samples exhibited effects of climatic and diagenetic alteration, with a primary marine signature. Furthermore, in the δ¹⁸O and δ¹³C isotope graphs, most of the Kızılören carbonate samples were located within the original seawater area and the low rock–water interaction area, while only one sample was located within the high rock–water interaction area. The positive correlation observed between the δ¹⁸O and δ¹³C isotopes in our studied samples indicates both meteoric water–seawater mixing and diagenetic alteration. The negative correlation in the carbonate samples and the positive correlation in the dolostone samples indicate low-grade diagenetic alteration in the limestones and moderate-grade diagenetic alteration in the dolostones. Both the Sr/Ba and Rb/K values (except for two samples indicating a brackish water environment) and the Z values calculated from the δ¹⁸O and δ¹³C isotope values (except for one sample indicating a brackish water environment) indicated that the vast majority of Kızılören carbonate samples were deposited in a marine environment. This situation likely resulted from a river flowing into the sea, forming a short-lived estuarine environment and subsequent carbonate accumulation. Paleoproductivity (Ba/Al, Baxs, P/Ti, P/Al, and Baxs diagrams) was observed at medium–low levels during the Kızılören carbonate deposition process. The CIX and PIX values of the Kızılören Formation carbonates are similar, with some samples (eight samples; < 40) unweathered, some (ten samples; 40–70) weakly weathered, and some (two samples; > 80) severely weathered. To determine the provenance of the detritals observed in the Kızılören carbonates, the La/Sc, Th/Sc, La/Co, Th/Co, Th/Cr, and Th/U element ratios were used. It was determined that the detrital grains in our studied samples were mostly from mafic and, to a lesser extent, felsic sources. According to geochemical data, the Neotethian (Late Triassic-Early Jurassic) Kızılören carbonate layers were deposited in an arid-to-subhumid climate and a shallow marine (carbonate shelf) environment, with relatively low detrital input and oxic-anoxic conditions.