Mineralogical and geochemical signatures of weathering on carbonate rocks and dynamic young land surfaces in Muğla Polje (SW Turkey)

Abstract

Red soils as the weathering products in Muğla Polje (SW Turkey) show different occurrences either on hard and permeable limestone (terra rossa (TRs)) or within the matrix of transported sediments (alluvium-derived soils (ALs), alluvium-derived soils specifically from clastics (ALsc), paleosol (Pls), and colluvium-derived soils (CLs)). The purpose of this study is to unlock the effect of weathering on hard carbonate rocks and dynamic young land surfaces (alluvium and colluvium) in Muğla Polje for the first time in terms of mineralogical and geochemical compositions. TRs, the soils of more stable environments are clayey while ALs and CLs as being the soils of dynamic environments have variable textures from silty clay loam to sandy loam. All soils share low CEC property (13–16.8 meq/100 g for TRs; 2–11.6 meq/100g for ALs and CLs). Nonclay components of the samples include quartz, feldspars, calcite, dolomite, and mica minerals. Hematite is observed as the main reddening agent for all samples. Illite, kaolinite, chlorite, and vermiculite are the clay minerals of the fine fractions. TRs are characterized by low intensity of salinization (<1) and calcification ([removed]0.3), and intense hydrolysis due to very high CIA and CIA-K (84%–88% and 89%–93%) under very high MAP (1230–1285 mm year–1). ALs and CLs are the soils with moderate to high calcification (>2), low salinization (<1), high base amounts (70–522; 73–141), low intensity of leaching developed under low CIA and CIA-K (3%–22% and 10%–16%) due to low MAP (<270 and <197 mm year–1). Samples of Pls and ALsc are also qualified with low salinization (<1), low calcification ([removed]0.2) associated with very high CIA and CIA-K (>80%, >90%) under very high MAP (>1260 mm year–1). Therefore, this study suggests that TRs are the results of intense weathering on carbonate rocks of more stable environments while ALs and CLs are the products of weathering of much lower intensity on alluvium and colluvium. As more mature soils of the polje, TRs also contribute to the matrix of the transported sediments in the lowlands of the polje