Akademik Veri Yönetim Sistemi
Facies, cilt.71, sa.4, 2025 (SCI-Expanded)
Glaucony, an Fe-rich mineral typically formed through marine authigenesis under specific physicochemical conditions, serves as a crucial indicator for reconstructing ancient marine settings. In the Eastern Black Sea region (Northeast Türkiye), glaucony-bearing limestone (GBL) strata have been discovered within uppermost Lower Cretaceous carbonates. However, the specific controls governing GBL formation have remained largely unexamined. This study presents the first comprehensive sedimentological and geochemical data to reconstruct the prevailing palaeoenvironmental conditions during the deposition of these GBL strata. The GBL strata exhibit a packstone texture, primarily comprising skeletal fragments transported from an adjacent inner carbonate platform, along with calcispheres and sponge spicules. The defining characteristic of this lithofacies is the pervasive presence of abundant, authigenic glaucony displaying ellipsoidal to reniform morphologies. Geochemical proxies, including Ce/Ce* ratios and V/(V + Ni) values, imply oxygen-depleted conditions during deposition. Furthermore, Sr/Cu and Sr/Ba ratios, coupled with elevated Al, Rb, Zr and Nb, suggest relatively humid, warm to mesothermal conditions. A slight enrichment in light rare earth elements (LREEs), positive Eu anomalies, depleted Y/Ho and Zr/Hf ratios, and elevated Sm/Yb ratios collectively point to a probable hydrothermal influence. Our integrated sedimentological and geochemical approach suggests that the observed Fe enrichment during the Albian period likely stems from a complex interplay of factors. These include hydrothermal activity associated with syn-sedimentary tectonic regimes and intensified continental weathering driven by prevailing palaeoclimatic conditions. These factors, in conjunction with basin subsidence and distinct palaeoenvironmental conditions, facilitated the deposition of the GBL during the Mid-Cretaceous sedimentary evolution of the Tethys basin.