INSIGHT INTO LATE HOLOCENE CLIMATE CHANGE IN MOZAMBIQUE: OSTRACOD, GEOCHEMICAL AND GRAIN-SIZE PRELIMINARY RESULTS

We present the last 3000 years cal BP of limnological change inferred from ostracod assemblage, carbon and nitrogen content, and grain-size data from a core collected in Lake Nyalonzelwe. These preliminary results provide a framework for local climate reconstructions in southeastern coastal Mozambique.

Lake Nyalonzelwe is an interdunal lake located in Inhambane region, bounded by a Pleistocene dune system. The core was sampled at 10 cm for all proxies. During ostracod analysis, foraminifera presence was also recorded.

From ~3000 to ~1500 yrs cal BP ostracods are predominantly represented by the brackish genus Cyprideis. At ~1500 yrs we observe a species turnover, with a gradual increase of ostracod species diversity, represented by freshwater genera as Sclerocypris and Zonocypris. This timepoint is also characterized by an increase in organic carbon content and a decrease in inorganic carbon content combined with an increase in mud percentage. A transition from an arid to a wet phase may explain the observed pattern. Ostracods are absent from 500 yrs cal BP to the recent, a period characterized by increasing organic matter content.

This work was financed by the Portuguese Science Foundation through project PTDC/HAR-ARQ/28148/2017.