Turkish Journal of Earth Sciences




Two important tectonostratigraphic units of the Karakaya Complex in northwest Turkey are: a lower metamorphic sequence of metabasite, phyllite and marble, called the Nilüfer Unit; and an upper clastic sequence with Permian and Carboniferous limestone olistoliths called the Hodul Unit. In northwestern Turkey, the Hodul Unit consists of arkosic sandstones, which pass upward into greywacke and siltstone with Permian and Carboniferous limestone blocks. A scarce macrofauna in the sandstones indicates a Norian age for the Hodul Unit. We report for the first time Norian-Rhaetian limestones, here named the Kaşal Limestone Member, from the Hodul Unit to the southwest of Balıkesir. The Kaşal Limestone Member forms ~80-m-thick, several-hundred-metres large blocks in a sheared siltstone, sandstone, and shale matrix of Norian age. The clastic matrix also includes neritic Permian limestone blocks. The Kaşal Limestone Member is a variegated, medium-bedded, nodular limestone with abundant coral, brachiopod, lamellibranch, crinoid, gastropod, algae, bryzoa, sponge spicules and foraminifera. A varied microfauna in the limestone indicates a Norian-Rhaetian age. The age similarity between the matrix and the Kaşal Limestone, and transition to a muddy facies observed in one of the blocks indicate that, unlike the exotic Permian limestones, the Kaşal Limestone Member represents in situ carbonate deposition in the Hodul basin. The subsequent shearing of the limestone contacts occurred during the deformation associated with the arrival of the olistostromes. The deformation leading to the closure of the Hodul basin is constrained to Rhaetian-Hettangian; that is, between 210 to 202 Ma, from the age of the Hodul Unit and that of the overlying Bayırköy Formation. This age is similar to the isotopic age of regional metamorphism in the Nilüfer Unit (215 to 205 Ma), and suggests that Cimmeride deformation in northwestern Turkey occurred over a short interval in the latest Triassic-earliest Jurassic.


Karakaya Complex, Norian, Rhaetian, northwestern Turkey, reefal limestone

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