Stratigraphic transition and palaeoenvironmental changes from the Aptian oceanic anoxic event 1a (OAE1a) to the oceanic red bed 1 (ORB1) in the Yenicesihlar section, central Turkey

► The early Aptian oceanic anoxic event 1a (OAE1a) in central Turkey. ► The stratigraphic and paleoenvironmental transition from the OAE1a to the oceanic red beds (ORB1) in central Turkey. ► The OAE1a-ORB1 transition corresponds to carbon isotopic C7 and C8 stages and lasted ∼1.3 Myr.