A POSSIBLE EPHEMERAL SHOALING OF THE CENTRAL AMERICAN SEAWAY DURING THE LATE MIOCENE (12.0 - 9.5 MA)? HIGH-RESOLUTION STABLE ISOTPIC EVIDENCE FROM ODP SITE 1000

High-resolution (4 kyr) benthic foraminiferal δ¹⁸O and δ¹³C records were developed from ODP Site 1000 to investigate the relationship of the Caribbean carbonate crash events (12.0 – 9.5 Ma) to the possible shoaling of the Panamanian Isthmus and the start-up of global thermohaline circulation. Site 1000 is located in the Pedro Channel on the Nicaragua Ridge between the Yucatan Peninsula and the island of Jamaica at 927 m below sea level, making it ideally located to monitor the development of the Caribbean Current as it contributed the development of the Gulf Steam and the onset of North Atlantic Deep Water circulation.

Both δ¹³C and δ¹⁸O records from Site 1000 follow some of the broad global trends as seen from other high-resolution records (e.g., South China Sea Site 1146, North Atlantic Site 982, and Southeast Atlantic Site 1085). This indicates that Site 1000 is a good register of global deep-water changes even though this site is bathed by intermediate waters. Superimposed over these long-term trends is the long (400 kyr) eccentricity cycle signal that dominates the δ¹³C record.

In addition, both isotopic records from Site 1000 contain differences from the global trends that can only be ascribed to regional circulation changes and possibly changes in Central America Seaway (CAS). The increase in δ¹³C values from 12.0 to 9.5 Ma are interpreted as decreasing North Pacific Intermediate Waters entering into the western Caribbean, concomitant with enhanced contribution of AAIW into the Caribbean Basin. In addition, a δ¹³C increase at 11.2 Ma correlates to the Caribbean carbonate crash event as seen in dissolution proxies (see Turetcaia poster).