The age and paleoenvironmental record of lacustrine deposits in the Aktoprak basin of south-central Turkey provides information about the evolution of topography, including the timing of development of an orographic rain shadow caused by uplift of the mountain ranges fringing the Central Anatolian Plateau. New magnetostratigraphy-based age estimates, in combination with existing biostratigraphic ages, suggest that the partially remagnetized Kurtulmuş Tepe section of the basin is Chattian (Upper Oligocene). The mean carbon and oxygen stable isotope ratios (δ18O = 24.6 ± 2.0 ‰, δ13C = -4.9 ± 1.1‰) are largely constant through the section and indicative of a subtropical, open freshwater lake. These isotopic values are also similar to those of the Chattian Mut basin to the south, on the Mediterranean side of the modern orographic barrier (Tauride Mountains), and indicate absence of an orographic barrier during Late Oligocene basin deposition. Post-depositional partial remagnetization occurred after tilting of the basin sequence and was mineralogically controlled, affecting grey, carbonate-rich rocks (average %CaCO3 = 82), whereas interlayered pink carbonate-poor rocks (average %CaCO3 = 38) carry a primary, pretilt magnetization. The pink rocks are rich in clay minerals that may have reduced the permeability of these rocks that carry a primary magnetization, concentrating basinal fluid flow in the carbonate-rich grey layers and leading to the removal and reprecipitation of magnetic minerals. The normal and reverse polarities recorded by the remagnetized rocks suggest that remagnetization occurred over a protracted period of time.
Bibliographical noteFunding Information:
This research was funded by NSF grant EAR-1109762, "Continental Dynamics: Central Anatolian Tectonics (CD-CAT)" to Donna L. Whitney and by support of the Institute for Rock Magnetism by the NSF/EAR Instruments and Facilities program. Maud J.M. Meijers was supported by the College of Science and Engineering and Department of Earth Sciences at the University of Minnesota. Becky E. Strauss received support from the University of Minnesota Doctoral Dissertation Fellowship. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program. Andreas Mulch acknowledges support through the LOEWE initiative of Hesse's Ministry of Higher Education, Research, and the Arts. Satellite imagery is copyright DigitalGlobe, Inc., provided through the Polar Geospatial Center (University of Minnesota-Twin Cities) and processed by Côme Lefebvre.
© 2016. American Geophysical Union. All Rights Reserved.
- continental basin
- partial remagnetization
- stable isotope geochemistry