In this study, stable C and O isotope compositions of bulk rock samples
from Barremian-Aptian platform carbonates of the Taurides, the Pontides,
and of their pelagic counterparts of the Sakarya continent in Turkey
were measured for the first time. Platform carbonates and pelagic
successions including a prominent black shale interval are composed of
distinct sedimentary cycles in the form of meter-scale shallowing-upward
sequences and limestone-marl/ shale couplets, respectively. The
biostratigraphy and the delta(13)C values allow this black shale
interval to be correlated with the ``Selli level''. Variations in
lithofacies and delta(13)C and delta(18)O values with the magnitudes of
about 2parts per thousand within the cycles indicate high frequency
fluctuations in sea level, probably in response to alternate periods of
cooling and warming occurring on Milankovitch-cycle scales even during
the greenhouse-type Cretaceous. A good overall correlation between
sedimentary cyclicity and variations in delta(18)O values suggests
preservation of the primary isotopic signal.