Formation of Ti-rich bauxite from alkali basalt in continental margin carbonates, Payas region, SE Turkey: implications for sea level change in the Upper Cretaceous

Abstract

The Payas region bauxite deposits occur as a sandwiched layer that is a few kilometers long and an average of 10 m thick between the lower and upper Cretaceous carbonates of the Arabian Platform. The bauxites occur as 2 types, comprising blanket and pocket, are chemically and texturally homogeneous, and have a thrust structure with ophiolitic mélange formations. The bauxite varies in color, from reddish-brown to grayish-green to black, and has a massive, patchy, and very rare oolitic-pisolitic texture. The bauxite mainly consists of diaspore, hematite, rutile, anatase, rare kaolinite, boehmite, and pyrite minerals.The prismatic and lath-shaped euhedral rutile within the bauxites indicated in situ formation of the bauxites from Ti-rich basaltic pyroclastics. The chondrite-normalized rare earth element pattern of the bauxite was similar to the basalt pattern and had a very weak Eu anomaly (0.9). There are 2 groups of elements have been enriched in the Payas region bauxite: the first group contains TiO2 (9.67wt%), Cr (752 ppm), V (617 ppm) and Ni (72 ppm), and the second group comprises Zr (993 ppm), Nb (86 ppm) and Sn (7 ppm). These 2 groups of element enrichment indicated that the parental material of bauxite had an alkali basalt character. The carbon and oxygen isotope stratigraphy throughout the carbonate section from the bottom to the top indicated that the climate was warm during bauxitization (mean δ18OVPDB: -6.15‰) and relatively cold after bauxite deposition (mean δ18OVPDB: -4.71‰). A marine regression during the warm climate could have been related to the uplifting of the coastal zone, which was linked to the vertical fault movements of the normal faults. A rapid transgression after bauxite formation during the cold climate period can be explained by subsidence of the continental margin, which was associated with episodic ophiolitic nappe loading during the closure of the Neotethyan Ocean in the region.