A broad deglacial δ13C minimum event in planktonic foraminiferal records in the Okinawa Trough

The equatorial Pacific upwelling zone has been suspected of playing an important role in the global atmospheric CO₂ changes associated with glacial-interglacial cycles. In order to assess the influencing scope of the surface water deglacial δ ¹³C minimum in the tropical low-latitude Pacific, the core DGKS9603, collected from the middle Okinawa Trough, was examined for δ ¹³C records of planktonic foraminifera N. dutertrei and G. ruber. The planktonic foraminiferal δ ¹³C records show a clear decreasing event from 20 to 6 cal. kaBP., which is characterized by long duration of about 14 ka and amplitude shift of 0.4 × 10^-3. Its minimum value occurred at 15.7 cal kaBP. The event shows fairly synchrony with the surface water deglacial δ ¹³C minimum identified in the tropical Pacific and its marginal seas. Because there is no evidence in planktonic foraminiferal fauna and δ ¹⁸O records for upwelling and river runoff enhancement, the broad deglacial δ ¹³C minimum event in planktonic foraminiferal records revealed in core DGKS9603 might have been the direct influencing result of the deglacial surface water of the tropical Pacific. The identification for the event in the Okinawa Trough provides new evidence that the water evolution in the tropical low-latitude Pacific plays a key role in large regional, even global carbon cycle.