Application of Sr isotope stratigraphy and sedimentary analysis to the origin and evolution of the Neogene basins in the Isparta Angle, southern Turkey

Four Miocene basins are located within the Isparta Angle in southern Turkey. One of these, the Darioren Basin, is well established as the foreland basin to the adjacent Lycian Nappes which marks the western margin of the Isparta Angle. The tectonic origin of the other three basins (Aksu, Kopru and Manavgat) has remained enigmatic largely because of the difficulties of dating the lowermost part of the succession (continental and shallow-marine conglomerates and limestones). Comparison of carbonate Sr-87/Sr-86 With the ocean water Sr isotope record provides a powerful chronological tool for marine sediments. By using Sr isotope ratios in this way, ages of the neritic limestones have been derived despite the absence of age-diagnostic fossils, These data constrain the age of the underlying conglomerates as lower to middle Burdigalian. The timing of deepening and subsidence events suggested by these new dates, taken together with palaeocurrent measurements from conglomerates, suggest that the basin configuration of the Isparta Angle was initiated in the lower Burdigalian and was directly related to movement on north-south-oriented faults. Depocentre development in the north of the Aksu Basin is consistent with a tectonic origin for all three basins by flexurally induced block faulting of the foreland in front of the Lycian Nappes along pre-existing structural weaknesses.