Analyzing sources to sedimentary organic carbon in the Gulf of Uraba, southern Caribbean, using carbon stable isotopes

Carbon stable isotopes analysis serve reconstruction of the origin of organic matter (OM) deposited onto sediments. They also allow tracing vegetation change at different time scales. This study weighs the contribution of both marine and terrestrial sources to sedimentary organic carbon (OC) from a southwestern Caribbean Gulf partly surrounded by large Musa acuminata (banana) croplands. The delta C-13 values in three sediment cores from the gulf have slightly decreased over 1000 yrs BP, indicating enhanced terrestrial input of detrital carbon owing to river discharge. A two-end mixing model fed with these delta C-13 values showed that averaged terrestrial contribution of OC to sediment was 52.0% at prodelta, 76.4% at delta front, and 64.2% at Colombia Bay. This agrees well with sediment dynamics. The main source, of sedimentary OC within the gulf was terrestrial instead of marine. In fact, a distorted trend in delta C-13 values for one of the coring sites could be the result of banana crop expansion through the 20th century. (C) 2017 Elsevier Ltd. All rights reserved.