A multi-proxy study of Holocene environmental change recorded in alluvial deposits along the southern coast of the Pampa region, Argentina

Abstract

Analyses of fossil records of molluscs, stable isotopes of carbon and oxygen, diatoms and palynomorphs from alluvial deposits at Arroyo Claromecó, in the southern Pampa region of Argentina, provide an integrated reconstruction of rapid Holocene environmental change related to marine and palaeoclimate influences. The major events recorded include: (i) disturbances produced by marine influences in close proximity to the coast before ca. 7700 cal a BP; (ii) a short-term decrease in salinity associated with freshwater influx between ca. 7700 and 7400 cal a BP in response to eustatic adjustment as sea level rose; (iii) an increasing input of marine water related to the Holocene sea-level highstand and greater evaporative conditions between 7400 and 6450 cal a BP; and (iv) evaporative processes linked to a pronounced climatic variability that triggered changes in water chemistry during the last ca. 6000 cal a BP concurrently with the late Holocene sea-level fall. A comparison of coastal and continental stable isotope records from the Pampa region reveals that evaporation and a negative precipitation/evaporation (P/E) ratio balance strongly influenced water chemistry in the coastal region, and was as important an influence as marine water during the period of maximum sea-level highstand.