13C, C/N and pollen as Holocene environmental indicators in northeastern Buenos Aires

VILANOVA I; MALAMUD-ROAM F.; INGRAM B.L.; YANG W.

Bariloche, Argentina

Congreso; IV Southern Connection Congress; 2010

Univ. Nac. del COMAHUE, CONICET, INTA

We present carbon isotopes, C/N ratios and fossil pollen which provide a record of changing paleoenvironmental conditions from a sedimentary sequence from Rio Salado, a coastal marsh in northeastern Buenos Aires, Argentina. Surface sediments from local modern coastal environments were used to calibrate the proxy-methods so that records from the paleo-sediments could be interpreted.Vegetation changes, as revealed by variations in the ä13C and pollen data, indicate a transition from high marsh conditions to unstable low marsh/intertidal conditions occurring between 7700-5870 14C yr BP, possibly related to a mid- Holocene sea-level high stand. This interpretation is supported by shell deposits found in the sediments. Unstable estuarine marsh conditions prevailed until ca. 4300 ¨C 1500 14C yr BP, replaced by brackish to freshwater marsh conditions, as reflected in greater diversity of vegetation. Our results demonstrate that stable C isotopes, fossil pollen and C/N ratios can be combined to reconstruct paleoenvironmental sequences in coastal marshes in the south Atlantic. The records reveal that sea level reached a high stand 7700 ¨C 5870 14C yr BP. These results provide insights for evaluating vulnerabilities in these coastal environments in the face of global sea level rise.