Cenozoic evolution of the Tripolitza carbonate platform in the Tethyan realm: New age constraints on deposition, diagenesis, metamorphism and nappe emplacement based on U-Pb and Rb-Sr dating (External Hellenides, Crete)


Klein T., Zulauf G., Evans D., Gerdes A., Glodny J., Heidelbach F., ...More

Geological Magazine, vol.160, no.7, pp.1282-1300, 2023 (SCI-Expanded) identifier

  • Publication Type: Article / Article
  • Volume: 160 Issue: 7
  • Publication Date: 2023
  • Doi Number: 10.1017/s0016756823000377
  • Journal Name: Geological Magazine
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Artic & Antarctic Regions, CAB Abstracts, Compendex, Environment Index, Geobase
  • Page Numbers: pp.1282-1300
  • Keywords: Crete, External Hellenides, Nummulite, Tripolitza Unit, U-Pb calcite
  • Istanbul Technical University Affiliated: Yes

Abstract

We present kinematic, radiometric, geochemical and PT data, which help to constrain the tectonometamorphic evolution of the Tripolitza Unit (TPU). The age of both the metamorphic peak (P = 0.4 ±0.2 GPa, T = ca. 310 °C) and top-to-the WNW mylonitic thrusting, attributed to the emplacement of the hanging Pindos nappe, has been constrained at 19 ±2.5 Ma using Rb-Sr on synkinematic white mica of a basal mylonite of NW Crete. This early tectonic event is also documented by the oldest generation of veins, which cut through less metamorphic (T = 240 ±15 °C) late Bartonian/Priabonian Nummulite limestone exposed as olistolith in TPU flysch of central Crete. Calcite of these veins yielded a similar U-Pb age at 20 ±6 Ma. U-Pb dating of matrix calcite, on the other hand, reflect the time of sedimentation (38.4 ±5.7 Ma and 37.6 ±1.2 Ma), which is in line with the faunal content of the black limestone. Geochemical data and U-Pb calcite ages of fibres of the Nummulite test (32.3 ±3.1 Ma and 34.6 ±0.9 Ma) suggest unexpected pseudomorphic fibre replacement during late Priabonian/early Rupelian diagenesis. Additional calcite veins, which developed at ca. 10-11 and 7 - 9 Ma (U-Pb on calcite), are attributed to top-to-the S thrusting and subsequent extension, respectively. The resulting anticlockwise rotation of the shortening direction within the TPU from WNW-ESE at ca. 20 Ma to N-S at ca. 10 Ma has significant implications for the geodynamic evolution of the External Hellenides.