Löwen, Kersten

The greater aim of this PhD thesis is to test the current palaeotectonic models for the Late Palaeozoic to Early Mesozoic evolution of the Palaeotethys in the Eastern Mediterranean. Therefore, siliciclastic rocks from two key areas – the Karaburun Peninsula in western Turkey and the Konya Complex in south-central Turkey – were examined in detail. These occurrences are of special importance as they exhibit virtually unmetamorphosed Palaeozoic and Mesozoic sedimentary successions and their role within the Tethyan realm has previously been interpreted in different ways. This dissent is caused by the lack of provenance data that could provide information to interpret the history of these sediments and to deduce characteristics of their source area. In the present study this issue is addressed by conducting an extensive provenance analysis using multiple techniques including thin-section petrography, whole-rock geochemistry, detrital zircon U–Pb geochronology and single-grain geochemistry (rutile, garnet, Cr- spinel). After a short introduction into the subject (Chapter 1), the new data from both study areas are presented and discussed (Chapter 2–4). The focus of Chapter 2 and 3 was placed on the Karaburun Peninsula in western Turkey. The first manuscript discusses the main compositional features (petrography and bulk-rock geochemistry) of the Late Palaeozoic sequence (Alandere, Küçükbahçe and Dikendag ̆ı formations) and the unconformably overlying Triassic rocks (Güvercinlik and Gerence formations and the  ̇Idecik unit). These data are combined with single-grain analyses of detrital rutile, garnet and Cr-spinel to unravel the origin and depositional tectonic setting of the studied rocks. In this context, a set of well-established and novel diagrams for the tectonic discrimination of siliciclastic sediments, using major and trace elements was tested. It has been shown that the efficiency of this approach is strongly dependent on the correct choice of a representative database and is hampered by effects of grain-size and age of the sediments. Overall, provenance sensitive data highlight the importance of felsic, amphibolite- to eclogite-facies source rocks for the studied stratigraphic sequence of the Karaburun Peninsula and indicate the presence of a nearby volcanic arc. To some extent, detritus was also derived from Palaeozoic ophiolites as documented by detrital Cr-spinels which were likely derived from harzburgite and lherzolite rocks (Alandere and Küçükbahçe formations) and podiform chromitites (Gerence Formation). The emphasis in Chapter 3 was placed on U–Pb ages from detrital zircons from sandstones of the Karaburun Peninsula to constrain their maximum depositional ages and identify possible source areas. Especially the timing of sediment accumulation for the supposedly Ordovician or Early Carboniferous Küçükbahçe and Dikendag ̆ı formations is a matter of discussion. The new data have set the limit of maximum sedimentation ages to Late Carboniferous–Early Permian and allowed to present a revised stratigraphic section for the Palaeozoic part of the Karaburun Peninsula. Furthermore, the obtained age spectra have been compared to data from Late Neoproterozoic and Palaeozoic potential igneous source rocks exposed in the Eastern Mediterranean region. In particular, the presence of prominent age populations from 350–450 Ma and 400–500 Ma in some samples provide strong evidence for sediment supply from units of the southern Eurasian margin, which is in agreement with previous reconstructions for the nearby Aegean islands of Chios and Inousses. Chapter 4 provides an extensive dataset for siliciclastic rocks of the Upper Palaeozoic Konya Complex and its Mesozoic cover sequence in south-central Turkey. The data are discussed to unravel their age, composition and origin and to shed light on the depositional history of the Konya basin. Despite missing evidence in terms of Late Palaeozoic (or younger) zircon populations in samples of the widely exposed Halıcı Formation, a Pennsylvanian–Cisuralian depositional age is inferred from available biostratigraphic data of the mélange. Information on provenance, inferred from the detrital zircon record of these rocks indicate sediment supply from both, units of the southern Eurasian margin but North Gondwana as well. Similar to source rocks for the stratigraphic sequence on the Karaburun Peninsula, our data suggest low- to medium-grade sedimentary sources of felsic character for both, the Halıcı and Ardıçlı formations. However, common components in the Chios–Karaburun units (garnet, Cr-spinel, arc-derived material) are virtually absent in sediments of the Konya Complex. An open question at the end of the study is the provenance of sediments from the Late Triassic Ardıçlı Formation, even though a very proximal source is most likely.
To conclude, the data from this study support a palaeotectonic model that combines aspects of different reconstructions. Most of the Upper Palaeozoic Chios–Karaburun units were deposited along the southern Eurasian margin in mid-Carboniferous to Early Permian time, whereas parts of the time-equivalent Halıcı Formation of the Konya Complex document sediment supply from North Gondwana as well. Northward directed subduction of Palaeotethys lithosphere was still active during that period but ceased until Late Triassic time, while the nature of the northern Gondwana margin remains controversial

eDiss Georg-August-University Göttingen

Late Palaeozoic to Early Mesozoic evolution of the Palaeotethys in Turkey: Insights from the Karaburun Peninsula and the Konya Complex

https://ediss.uni-goettingen.de/bitstream/21.11130/00-1735-0000-0005-129E-5/1/Dissertation_Loewen.pdf

Late Palaeozoic to Early Mesozoic evolution of the Palaeotethys in Turkey: Insights from the Karaburun Peninsula and the Konya Complex

Abstract

Similar works

Full text

Available Versions

eDiss Georg-August-University Göttingen