Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

Geological Magazine

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (13) Citing Articles via Google Scholar Google Scholar Articles by GAUTIER, P. Articles by DIRIK, K. Search for Related Content GeoRef GeoRef Citation

Dating the exhumation of a metamorphic dome: geological evidence for pre-Eocene unroofing of the Nide Massif (Central Anatolia, Turkey)

PIERRE GAUTIER^*,, ERDIN BOZKURT, ERWAN HALLOT^* and KADIR DIRIK^,

^* Géosciences Rennes, UMR CNRS 6118, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
Middle East Technical University, Department of Geological Engineering, Tectonic Research Unit, TR-06531 Ankara, Turkey

Author for correspondence: pierre.gautier{at}univ-rennes1.fr

The timing of exhumation of metamorphic rocks and granitoids of the Nide metamorphic dome, at the southern tip of the Central Anatolian Crystalline Complex, is a matter of debate. According to some authors, the metamorphic rocks are overlain nonconformably by a sedimentary sequence of late Maastrichtian to Late Palaeocene age. In contrast, other authors recently argued that the Nide dome represents an extensional core complex of Oligocene–Early Miocene age, finally unroofed during late Miocene times. On the one hand, the results of our study contradict the latter interpretation. A sedimentary sequence of earliest Eocene to early Middle Eocene age nonconformably overlies the high-grade rocks of the Nide dome on its southeastern flank. Pebbles from the metamorphic rocks are ubiquitous in the conglomerates of this sequence. As a result, the Nide metamorphic rocks must have reached the surface before Eocene times, or at the very beginning of the Eocene at the latest. The Üçkapili granite, whose crystallization age has been inferred to be Early Miocene, has intruded the metamorphic complex during exhumation. The granite is also found as pebbles within the conglomerates of the Eocene sedimentary sequence and, thus, is actually older than the Eocene. Apatite fission track dates of 12–11 Ma across the Nide dome do not indicate that the metamorphic rocks were still on their way to the surface at that time; instead, they must reflect a later event, which is most probably heating during late Neogene magmatism. Lastly, there is no ductile-then-brittle extensional detachment in the two areas where it has been invoked, that is, on the western and southern flanks of the dome. An extensional detachment nevertheless exists at the top of the Nide dome, best documented in its northern part, where the detachment fault superposes a superficial unit made up of massive ophiolitic rocks onto the high-grade metamorphic sequence. Field evidence indicates that this detachment developed before Eocene times. On the other hand, our observations do not confirm the nonconformity of the sedimentary sequence dated as late Maastrichtian–Late Palaeocene onto the Nide high-grade rocks. Field relations show either a tectonic contact between the two, or the direct nonconformity of the Eocene sediments onto the metamorphic rocks. The lack of coarse clasts originating from the Nide high-grade rocks within the Maastrichtian–Palaeocene sequence further suggests that the metamorphic dome did not reach the surface before Late Palaeocene times. These results compare well with available data from the northwestern part of the Central Anatolian Crystalline Complex, suggesting that exhumation has been broadly synchronous on the scale of the massif, as a result of an episode of high magnitude extension that affected the region in Campanian to Palaeocene times.

Key Words: exhumation • extension tectonics • unconformities • Anatolia • Alpine Orogeny

This article has been cited by other articles:

				N. Kaymakci, Y. Ozcelik, S. H. White, and P. M. Van Dijk Tectono-stratigraphy of the Cankiri Basin: Late Cretaceous to early Miocene evolution of the Neotethyan Suture Zone in Turkey Geological Society, London, Special Publications, January 1, 2009; 311(1): 67 - 106. [Abstract] [Full Text] [PDF]

				P. J. Umhoefer, D. L. Whitney, C. Teyssier, A. K. Fayon, G. Casale, and M. T. Heizler Yo-yo tectonics in a wrench zone, Central Anatolian fault zone, Turkey Geological Society of America Special Papers, January 1, 2007; 434(0): 35 - 57. [Abstract] [Full Text] [PDF]

				T. Taymaz, Y. Yilmaz, and Y. Dilek The geodynamics of the Aegean and Anatolia: introduction Geological Society, London, Special Publications, January 1, 2007; 291(1): 1 - 16. [Full Text] [PDF]

				Y. K. Kadioglu, Y. Dilek, and K. A. Foland Slab break-off and syncollisional origin of the Late Cretaceous magmatism in the Central Anatolian crystalline complex, Turkey Geological Society of America Special Papers, January 1, 2006; 409(0): 381 - 415. [Abstract] [Full Text] [PDF]

				N. ILBEYLI Mineralogical-geochemical constraints on intrusives in central Anatolia, Turkey: tectono-magmatic evolution and characteristics of mantle source Geological Magazine, March 1, 2005; 142(2): 187 - 207. [Abstract] [Full Text] [PDF]