Metamorphism & Tectonics in the Eastern Mediterranean
TÜRKIYE

Co-workers and I are studying the pressure (P) - temperature (T) - time (t) history and tectonic development of metamorphic terrains in the eastern Mediterranean (Turkey). Central Anatolia contains metamorphic rocks and associated structures that formed during Alpine-Himalayan collision and subduction of Neotethyan seaways prior to collision. These rocks are spectacularly exposed, allowing us to link petrologic and kinematic history through time.


This simplified geologic map of Turkey shows the location of some of the places I've been working: the Central Anatolian Crystalline Complex (CACC) and a region near the town of Sivrihisar.


Paul Umhoefer (left) and Christian Teyssier (right) investigate the subsurface of the
Byzantine (7th-11th century) Gumusler monastery that has been carved into an
ignimbrite, hoping to find the contact with the underlying Nigde metamorphic rocks.

Current work focuses on two regions/problems:

Continental margin subduction complex, Sivrihisar region: blueschist facies metasedimentary and metavolcanic rocks (some containing eclogite pods) record prograde and retrograde metamorphism. These rocks are extremely interesting because the blueschists are adjacent to quartzites that contain andalusite + kyanite + sillimanite + staurolite ± garnet, and schists that contain chloritoid ± staurolite ± garnet.  We are trying to relate the metamorphic history of these rocks (blueschists, eclogites, and Al2SiO5-bearing rocks) to the subduction and exhumation processes, as well as other important events in the region (emplacement of ophiolites; magmatism). Research team: D. Whitney, C. Teyssier, P. Davis, A. Aycenk (Minnesota).
 

Garnet-lawsonite blueschist interlayered with eclogite

Photomicrograph of garnet-lawsonite blueschist.
Field of view = 4 mm.

Thermal evolution of oblique orogens, Nigde region (Central Anatolian Crystalline Complex): The Nigde massif provides a window into the mid-crust of a highly oblique orogenic system and permits reconstruction of the tectonic and thermal history of the upper 20 km of continental crust during oblique motion. What are the rates and styles of thermal and structural processes during oblique deformation at different crustal levels? How does the style and timing of deformation change from the mid- to upper crust in zones of oblique deformation? Since the petrologic study of the massif is largely complete, we can evaluate the structural history of the complex in the context of metamorphic pressure-temperature paths. As part of the broad goal of understanding oblique continental orogens, we are documenting characteristics and rates of deformation and metamorphism during highly oblique deformation and building a conceptual model for crustal thickening and extension leading to the development of metamorphic core complexes in zones of wrenching. Research team: D. Whitney (Minnesota), C. Teyssier (Minnesota), P. Umhoefer (Northern Arizona University), Gabe Casale (formerly at Minnesota; now at Univ of Washington).


View of eastern margin of the Nigde Massif showing the metamorphic sequence (white marble and darker schists on left side), a faulted unconformity, and the overlying sedimentary sequence (dipping layers). East of the massif and cover is the Ecemis fault corridor (valley), and the Aladag Mountains carbonate nappes).

Field companions in Turkey (click for list and photos)


The Aya Sofia, Istanbul  (photo by C. Teyssier)

Recent publications related to our research in Turkey:

Whitney, D.L. and Hamilton, M. (in press) Timing of high-grade metamorphism in central Turkey and the assembly of Anatolia. Journal of the Geological Society of London.

Whitney, D.L., Teyssier, C., Fayon, A.K., Hamilton, M.A., Heizler, M. (2003) Tectonic controls on metamorphism, partial melting, and intrusion: timing of regional metamorphism and magmatism of the Nigde Massif, Turkey. Tectonophysics, 376, 37-60.

Whitney, D.L. (2002) Coexisting andalusite, kyanite, and sillimanite: sequential formation of three polymorphs during progressive metamorphism near the Al2SiO5 triple point, Sivrihisar, Turkey. American Mineralogist, Special issue in honor of M.J. Holdaway, 87, 405-416.

Whitney, D.L. and Bozkurt, E. (2002) Metamorphic history of the southern Menderes Massif, western Turkey. Geological Society of America Bulletin, 114, 829-838.

Fayon, A.K., Whitney, D.L., Teyssier, C., Dilek, Y., and Garver, J.I. (2001) Effects of plate convergence angle on timing and mechanisms of exhumation. Earth and Planetary Science Letters, 192, 191-205.

Whitney, D.L., Teyssier, C., Dilek, Y., and Fayon, A.K. (2001) Metamorphism of the Central Anatolian Crystalline Complex, Turkey: influence of orogen-normal collision vs. wrench-dominated tectonics on P-T-t paths. Journal of Metamorphic Geology, 19, 411-432.

Whitney, D.L., and Dilek, Y. (2001) Metamorphic and structural geology of the Hirkadag block, Central Anatolian Crystalline Complex. Turkish Journal of Earth Sciences, 10 (1), 1-15.

Dilek, Y., and Whitney, D.L. (2000) Cenozoic crustal evolution in central Anatolia: extension, magmatism, and landscape development. In: Panayides, I., Xenophontos, C., and Malpas, J. (eds). Proceedings of the Third International Conference on the Geology of the Eastern Mediterranean. Geological Survey Department, Nicosia, Cyprus, 183-192.

Whitney, D.L., and Dilek, Y. (2000) Andalusite-sillimanite-quartz veins as indicators of low-pressure - high-temperature deformation during late-stage unroofing of a metamorphic core complex, Turkey. Journal of Metamorphic Geology, 18, 59-66.

Dilek, Y., Whitney, D.L., and Tekeli, O.  (1999) Links between neotectonic processes and landscape evolution in an Alpine collision zone, south-central Turkey. Geomorphology, 118, 147-164.

Whitney, D.L., and Dilek, Y. (1998) Metamorphism during crustal thickening and extension in central Anatolia: the Nigde metamorphic core complex. Journal of Petrology, 39, 1385-1403.

Whitney, D.L., and Dilek, Y. (1998) Characterization and interpretation of P-T paths with multiple thermal peaks. In: What Drives Metamorphism and Metamorphic Reactions:? (eds Treloar, P.J. & O'Brien, P.) Geological Society of London Special Publications, 138, 47-54.

Whitney, D.L., and Dilek, Y. (1997) Core complex development in central Anatolia. Geology, 25, 1023-1026.

Dilek, Y., and Whitney, D.L. (1997) Counterclockwise P-T-t trajectory from the metamorphic sole of a Neo-tethyan ophiolite (Turkey). Tectonophysics, 280 (3-4), 295-310.

 


This is me appearing unconcerned about the major strike-slip fault nearby (note fault scarp).
Ecemis fault corridor, Nigde (September 2001).

Images from field work in Turkey, 1994-2003
 
NIGDE MASSIF
MISC GEOLOGY PHOTOS
MISC TURKEY PHOTOS
  X-RAY MAPS & misc images



Here's what the Sivrihisar range looks like from the east/northeast. Pink = metamorphic rocks, red = granitoid;
green = meta-ultramafic rocks and associated metagabbro; everything else (orange, brown, yellow, gray) =
sedimentary rocks or sediments. (Image created by Paul Morin by overlaying the 1: 500 000 geologic map on
a digital elevation model). The western part of the range appears to be entirely a blueschist massif, but the eastern/
southern range is more complex, with juxtaposed blueschists and high-temperature rocks (sillimanite-bearing quartzite).