The rare earth element geochemistry on surface sediments, shallow cores and lithological units of Lake Acıgöl basin, Denizli, Turkey Murat Budakoglu a,⇑ , Amr Abdelnasser a,b , Muhittin Karaman a , Mustafa Kumral a a Geochemistry Research Group and JAL Laboratories, Department of Geological Engineering, Faculty of Mines, Istanbul Technical University, Maslak, 34469 Istanbul, Turkey b Department of Geology, Faculty of Science, Benha University, 13518 Benha, Egypt article info Article history: Received 20 January 2015 Received in revised form 4 May 2015 Accepted 28 May 2015 Available online 18 June 2015 Keywords: REE geochemistry Paleoenvironmental proxy 137 Cs and 210 Pb dating Sediment accumulation rate Spatial geochemical modeling IDW GWR Lake Acıgöl Turkey abstract The sediments in Lake Acıgöl, located in SW Anatolia, Turkey, were formed under tectono-sedimentary events. REE geochemical investigations of the Lake Acıgöl sediments, from surface and shallow core sed- iments at different depths (0–10 cm, 10–20 cm and 20–30 cm) are presented to clarify the characteristics of REE and the nature of source rocks in the lake sediments’ and to deduce their paleoenvironmental proxies. The chondrite-normalized REE patterns of these sediments are shown as light enrichment in LREE and flat HREE with a negative Eu anomaly that is close to the continental collision basin (CCB) in its profile; this is not comparable with PAAS and UCC. Inorganic detrital materials control the REE char- acteristics of the Lake Acıgöl sediments and these sediments were accumulated in oxic and dysoxic depo- sitional conditions and/or at passive margins derived from oceanic island arc rocks. They were affected by low chemical weathering, either at the original source or during transport, before deposition under arid or subtropical humid climatic conditions. In addition, we used GIS techniques (such as Inverse Distance Weighted (IDW) and Geographically Weighted Regression (GWR)) to investigate the spatial interpolation and spatial correlation of the REEs from the lake surface sediments in Lake Acıgöl and its surrounding lithological units. GIS techniques showed that the lithological units (e.g., Hayrettin Formation) north of Lake Acıgöl have high REE contents; however, Eu/Eu ⁄ values were higher in some lake surface sediments than in lithological units, and that refers to a negative Eu-anomaly. Therefore, Lake Acıgöl sediments are derived from the weathered products, mainly from local, highly basic bedrock around the lake from the Archean crust. The chronology of Lake Acıgöl sediment was conducted using the Constant Rate of Supply (CRS) model. Using the CRS methods for the calculation of sedimentation rate, we obtained a 0.012 g/cm 2 /year value which is an average value for the first 20 cm depth of this lake. The core activity profiles of 210 Pb and 137 Cs were measured to estimate the age of the sediments; we observed activities of 8.08 ± 5.5 Bq/kg for 210 Pb and 0.86 ± 0.6 Bq/kg for 137 Cs. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction In the last two decades, REEs have been widely used to study paleoenvironmental conditions and paleoclimatic changes (Bai et al., 2014; Ding et al., 2001; Domingo et al., 2011; Holser, 1997; Och et al., 2014; Yang et al., 2014) as well as sedimentary origin and tectonic settings (Chen et al., 2014; Cui et al., 2014). In addition, the distribution patterns of normalized-REE have received considerable attention in various geochemical studies due to their chemical properties of REEs. From La to Lu, REEs show limited variations in their physical and chemical properties which allow their fractionation and enrichment in different parts of the earth surface (Das et al., 2006; Henderson, 1984; Johannesson et al., 1999; Taylor and McLennan, 1988; Wood, 1990). Alkaline lakes provide a useful opportunity to investigate and improve the understandings of the mechanism of REE fractionation and behaviors in the aquatic systems (Wang et al., 2013). At SW Anatolia, Turkey, the crustal extension created several fluvio-lacustrine basins with active sedimentation in modern deep to shallow lakes (Helvaci et al., 2013). Lake Acıgöl is considered to be one of the largest hypersaline lakes in Turkey. It is located at the inner Aegean Region in a closed basin at the junction between three Provinces: Denizli, Afyonkarahisar and Burdur. Its sediments were formed under tectono-sedimentary events and its surface varies greatly due to seasonal drought with an active precipitation of sodium, calcium and magnesium salts (Helvaci et al., 2004). Lacustrine mineral sources of Lake Acıgöl include detrital, http://dx.doi.org/10.1016/j.jseaes.2015.05.016 1367-9120/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: budak@itu.edu.tr (M. Budakoglu). Journal of Asian Earth Sciences 111 (2015) 632–662 Contents lists available at ScienceDirect Journal of Asian Earth Sciences journal homepage: www.elsevier.com/locate/jseaes