A MIDDLE TRIASSIC AGE FOR LOW-GRADE GREENSCHIST FACIES METAMORPHIC SEQUENCE IN BERGAMA (IZMIR), WESTERN TURKEY - THE 1ST PALEONTOLOGICAL AGE ASSIGNMENT AND STRUCTURAL-STRATIGRAPHIC IMPLICATIONS

Low-grade greenschist facies metamorphic rocks are widely exposed in western Turkey. Paleozoic and Mesozoic ages have been assigned in previous work on the basis of suggested ages for the bounding sedimentary rocks. To the north of Bergama (Pergamon, Izmir), the upper part of a stratigraphically continuous succession of metamorphic rocks (the Madradag Formation) consists, in ascending order, of micaceous and chloritic phyllite, mafic metatuff, interstratified marble and mafic metatuff, and phyllite and metachert. This succession is overlain unconformably by the Late Triassic sequence of turbidites and olistostromes (the Diskaya Formation). The Late Triassic basal strata contain clasts derived from the immediately underlying metamorphic rocks. The recrystallized limestone interlayers in the phyllite at the top of the Madradag Formation and recrystallized limestone blocks in the Diskaya Formation contain a common conodont fauna indicating a Middle Triassic age (boundary of Late Anisian/Early Ladinian) for the early termination of the metamorphic sequence.