MARSH FORAMINIFERAL ASSEMBLAGES IN THE VALDIVIA ESTUARY, SOUTH-CENTRAL CHILE, RELATIVE TO VASCULAR PLANTS AND SEA-LEVEL

High marsh foraminiferal assemblages are distinct from those of the lo w marsh, mud flat, and upland floral zones in two transects across tid al marshes in the Valdivia estuary of south-central Chile. Assemblages from the high marsh, mapped on the basis of vascular plant communitie s, consist mostly of Trochamminita salsa and have higher concentration s of foraminifera than samples from lower intertidal zones. Fossil ass emblages in a core that records the sudden subsidence of the Valdivia estuary during the great earthquake of 1960 cannot be used to estimate the amount of sudden sea-level rise during the earthquake because the core contains only low marsh/mud dat assemblages, which are indisting uishable from one another. The 0.8-0.5 m vertical range of the high ma rsh assemblage zone, and the undefined ranges of the low marsh/mud Bat and upland zones also limit the precision of estimates of relative se alevel change. More precise estimates of the amount of land-level chan ge during past great earthquakes in this region will require identific ation of assemblage zones with narrower elevational ranges. The Valdiv ia high marsh foraminiferal assemblages differ dramatically from other reported high marsh assemblages from the mid-latitude Americas in bei ng dominated by Trochamminita salsa. Our study of the large population s of the genus Trochamminita Cushman and Bronnimann encountered along the transects indicates that the two species of Trochamminita that hav e been described previously should be combined into the single species , Trochamminita salsa.