Southern Patagonian archaeological sites (47º - 49º S; 72º W, Argentina) as pollen records: Pollen preservation analysis considerations for accurate palaeoenvironmental reconstructions

Abstract

Fossil pollen records from archaeological sites have been largely used to reconstruct past vegetation dynamics and environmental conditions in relation to anthropogenic factors. In this paper we examine the degree of pollen preservation from four archaeological sequences in the west of Santa Cruz Province, Argentina (47-49º S; 72º W) to determine different types of pollen damage and their associated causes. Sites located in the Pueyrredón Lake basin (47º S; 72º W, CMN1 and CMN2) and in the San Martín Lake basin (49º S; 72º W, CPD and B1Oq) were selected due to differences in morphology, topographic position and orientation but with similar surrounding vegetation composition. Pollen deterioration indices were calculated considering differences in pollen taphonomy mainly related to both biochemical (degraded grains) and mechanical (broken and crumpled grains) damage. The results show that different factors (sedimentological, environmental and anthropogenic) could affect pollen preservation. The preservation problems of CMN1, CPD and B1Oq were not significant. However, pollen assemblage of CMN2 presented remarkable mechanical and biochemical damage. The main causes of problems of pollen preservation detected were: exposure to high temperatures, oxidation, pH effect, abrasion of the sediments that caused mechanical damage and the presence of fungi associated with biochemical damage.